Self-reported knee joint instability is related to passive mechanical stiffness in medial knee osteoarthritis

PubMed Central

2013-01-01

Background Self-reported knee joint instability compromises function in individuals with medial knee osteoarthritis and may be related to impaired joint mechanics. The purpose of this study was to evaluate the relationship between self-reported instability and the passive varus-valgus mechanical behaviour of the medial osteoarthritis knee. Methods Passive varus-valgus angular laxity and stiffness were assessed using a modified isokinetic dynamometer in 73 participants with medial tibiofemoral osteoarthritis. All participants self-reported the absence or presence of knee instability symptoms and the degree to which instability affected daily activity on a 6-point likert scale. Results Forward linear regression modelling identified a significant inverse relationship between passive mid-range knee stiffness and symptoms of knee instability (r = 0.27; P < 0.05): reduced stiffness was indicative of more severe instability symptoms. Angular laxity and end-range stiffness were not related to instability symptoms (P > 0.05). Conclusions Conceivably, a stiffer passive system may contribute toward greater joint stability during functional activities. Importantly however, net joint stiffness is influenced by both active and passive stiffness, and thus the active neuromuscular system may compensate for reduced passive stiffness in order to maintain joint stability. Future work is merited to examine the role of active stiffness in symptomatic joint stability. PMID:24252592

The bending stiffness of shoes is beneficial to running energetics if it does not disturb the natural MTP joint flexion.

PubMed

Oh, Keonyoung; Park, Sukyung

2017-02-28

A local minimum for running energetics has been reported for a specific bending stiffness, implying that shoe stiffness assists in running propulsion. However, the determinant of the metabolic optimum remains unknown. Highly stiff shoes significantly increase the moment arm of the ground reaction force (GRF) and reduce the leverage effect of joint torque at ground push-off. Inspired by previous findings, we hypothesized that the restriction of the natural metatarsophalangeal (MTP) flexion caused by stiffened shoes and the corresponding joint torque changes may reduce the benefit of shoe bending stiffness to running energetics. We proposed the critical stiffness, k cr , which is defined as the ratio of the MTP joint (MTPJ) torque to the maximal MTPJ flexion angle, as a possible threshold of the elastic benefit of shoe stiffness. 19 subjects participated in a running test while wearing insoles with five different bending stiffness levels. Joint angles, GRFs, and metabolic costs were measured and analyzed as functions of the shoe stiffness. No significant changes were found in the take-off velocity of the center of mass (CoM), but the horizontal ground push-offs were significantly reduced at different shoe stiffness levels, indicating that complementary changes in the lower-limb joint torques were introduced to maintain steady running. Slight increases in the ankle, knee, and hip joint angular impulses were observed at stiffness levels exceeding the critical stiffness, whereas the angular impulse at the MTPJ was significantly reduced. These results indicate that the shoe bending stiffness is beneficial to running energetics if it does not disturb the natural MTPJ flexion. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multi-field coupled sensing network for health monitoring of composite bolted joint

NASA Astrophysics Data System (ADS)

Wang, Yishou; Qing, Xinlin; Dong, Liang; Banerjee, Sourav

2016-04-01

Advanced fiber reinforced composite materials are becoming the main structural materials of next generation of aircraft because of their high strength and stiffness to weight ratios, and excellent designability. As key components of large composite structures, joints play important roles to ensure the integrity of the composite structures. However, it is very difficult to analyze the strength and failure modes of composite joints due to their complex nonlinear coupling factors. Therefore, there is a need to monitor, diagnose, evaluate and predict the structure state of composite joints. This paper proposes a multi-field coupled sensing network for health monitoring of composite bolted joints. Major work of this paper includes: 1) The concept of multifunctional sensor layer integrated with eddy current sensors, Rogowski coil and arrayed piezoelectric sensors; 2) Development of the process for integrating the eddy current sensor foil, Rogowski coil and piezoelectric sensor array in multifunctional sensor layer; 3) A new concept of smart composite joint with multifunctional sensing capability. The challenges for building such a structural state sensing system and some solutions to address the challenges are also discussed in the study.

A model-based approach to stabilizing crutch supported paraplegic standing by artificial hip joint stiffness.

PubMed

van der Spek, Jaap H; Veltink, Peter H; Hermens, Hermie J; Koopman, Bart F J M; Boom, Herman B K

2003-12-01

The prerequisites for stable crutch supported standing were analyzed in this paper. For this purpose, a biomechanical model of crutch supported paraplegic stance was developed assuming the patient was standing with extended knees. When using crutches during stance, the crutches will put a position constraint on the shoulder, thus reducing the number of degrees of freedom. Additional hip-joint stiffness was applied to stabilize the hip joint and, therefore, to stabilize stance. The required hip-joint stiffness for changing crutch placement and hip-joint offset angle was studied under static and dynamic conditions. Modeling results indicate that, by using additional hip-joint stiffness, stable crutch supported paraplegic standing can be achieved, both under static as well as dynamic situations. The static equilibrium postures and the stability under perturbations were calculated to be dependent on crutch placement and stiffness applied. However, postures in which the hip joint was in extension (C postures) appeared to the most stable postures. Applying at least 60 N x m/rad hip-joint stiffness gave stable equilibrium postures in all cases. Choosing appropriate hip-joint offset angles, the static equilibrium postures changed to more erect postures, without causing instability or excessive arm forces to occur.

A painless and constraint-free method to estimate viscoelastic passive dynamics of limbs' joints to support diagnosis of neuromuscular diseases.

PubMed

Venture, Gentiane; Nakamura, Yoshihiko; Yamane, Katsu; Hirashima, Masaya

2007-01-01

Though seldom identified, the human joints dynamics is important in the fields of medical robotics and medical research. We present a general solution to estimate in-vivo and simultaneously the passive dynamics of the human limbs' joints. It is based on the use of the multi-body description of the human body and its kinematics and dynamics computations. The linear passive joint dynamics of the shoulders and the elbows: stiffness, viscosity and friction, is estimated simultaneously using the linear least squares method. Acquisition of movements is achieved with an optical motion capture studio on one examinee during the clinical diagnosis of neuromuscular diseases. Experimental results are given and discussed.

An acoustic startle alters knee joint stiffness and neuromuscular control.

PubMed

DeAngelis, A I; Needle, A R; Kaminski, T W; Royer, T R; Knight, C A; Swanik, C B

2015-08-01

Growing evidence suggests that the nervous system contributes to non-contact knee ligament injury, but limited evidence has measured the effect of extrinsic events on joint stability. Following unanticipated events, the startle reflex leads to universal stiffening of the limbs, but no studies have investigated how an acoustic startle influences knee stiffness and muscle activation during a dynamic knee perturbation. Thirty-six individuals were tested for knee stiffness and muscle activation of the quadriceps and hamstrings. Subjects were seated and instructed to resist a 40-degree knee flexion perturbation from a relaxed state. During some trials, an acoustic startle (50 ms, 1000 Hz, 100 dB) was applied 100 ms prior to the perturbation. Knee stiffness, muscle amplitude, and timing were quantified across time, muscle, and startle conditions. The acoustic startle increased short-range (no startle: 0.044 ± 0.011 N·m/deg/kg; average startle: 0.047 ± 0.01 N·m/deg/kg) and total knee stiffness (no startle: 0.036 ± 0.01 N·m/deg/kg; first startle 0.027 ± 0.02 N·m/deg/kg). Additionally, the startle contributed to decreased [vastus medialis (VM): 13.76 ± 33.6%; vastus lateralis (VL): 6.72 ± 37.4%] but earlier (VM: 0.133 ± 0.17 s; VL: 0.124 ± 0.17 s) activation of the quadriceps muscles. The results of this study indicate that the startle response can significantly disrupt knee stiffness regulation required to maintain joint stability. Further studies should explore the role of unanticipated events on unintentional injury. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints

PubMed Central

Avgoulas, Evangelos I.; Sutcliffe, Michael P. F.

2016-01-01

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints. PMID:28773688

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints.

PubMed

Avgoulas, Evangelos I; Sutcliffe, Michael P F

2016-07-12

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints.

Estimation of joint stiffness with a compliant load.

PubMed

Ludvig, Daniel; Kearney, Robert E

2009-01-01

Joint stiffness defines the dynamic relationship between the position of the joint and the torque acting about it. It consists of two components: intrinsic and reflex stiffness. Many previous studies have investigated joint stiffness in an open-loop environment, because the current algorithm in use is an open-loop algorithm. This paper explores issues related to the estimation of joint stiffness when subjects interact with compliant loads. First, we show analytically how the bias in closed-loop estimates of joint stiffness depends on the properties of the load, the noise power, and length of the estimated impulse response functions (IRF). We then demonstrate with simulations that the open-loop analysis will fail completely for an elastic load but may succeed for an inertial load. We further show that the open-loop analysis can yield unbiased results with an inertial load and document IRF length, signal-to-noise ratio needed, and minimum inertia needed for the analysis to succeed. Thus, by using a load with a properly selected inertia, open-loop analysis can be used under closed-loop conditions.

Joint stiffness and running economy during imposed forefoot strike before and after a long run in rearfoot strike runners.

PubMed

Melcher, Daniel A; Paquette, Max R; Schilling, Brian K; Bloomer, Richard J

2017-12-01

Research has focused on the effects of acute strike pattern modifications on lower extremity joint stiffness and running economy (RE). Strike pattern modifications on running biomechanics have mostly been studied while runners complete short running bouts. This study examined the effects of an imposed forefoot strike (FFS) on RE and ankle and knee joint stiffness before and after a long run in habitual rearfoot strike (RFS) runners. Joint kinetics and RE were collected before and after a long run. Sagittal joint kinetics were computed from kinematic and ground reaction force data that were collected during over-ground running trials in 13 male runners. RE was measured during treadmill running. Knee flexion range of motion, knee extensor moment and ankle joint stiffness were lower while plantarflexor moment and knee joint stiffness were greater during imposed FFS compared with RFS. The long run did not influence the difference in ankle and knee joint stiffness between strike patterns. Runners were more economical during RFS than imposed FFS and RE was not influenced by the long run. These findings suggest that using a FFS pattern towards the end of a long run may not be mechanically or metabolically beneficial for well-trained male RFS runners.

Measuring multi-joint stiffness during single movements: numerical validation of a novel time-frequency approach.

PubMed

Piovesan, Davide; Pierobon, Alberto; DiZio, Paul; Lackner, James R

2012-01-01

This study presents and validates a Time-Frequency technique for measuring 2-dimensional multijoint arm stiffness throughout a single planar movement as well as during static posture. It is proposed as an alternative to current regressive methods which require numerous repetitions to obtain average stiffness on a small segment of the hand trajectory. The method is based on the analysis of the reassigned spectrogram of the arm's response to impulsive perturbations and can estimate arm stiffness on a trial-by-trial basis. Analytic and empirical methods are first derived and tested through modal analysis on synthetic data. The technique's accuracy and robustness are assessed by modeling the estimation of stiffness time profiles changing at different rates and affected by different noise levels. Our method obtains results comparable with two well-known regressive techniques. We also test how the technique can identify the viscoelastic component of non-linear and higher than second order systems with a non-parametrical approach. The technique proposed here is very impervious to noise and can be used easily for both postural and movement tasks. Estimations of stiffness profiles are possible with only one perturbation, making our method a useful tool for estimating limb stiffness during motor learning and adaptation tasks, and for understanding the modulation of stiffness in individuals with neurodegenerative diseases.

Lower limb joint kinetics and ankle joint stiffness in the sprint start push-off.

PubMed

Charalambous, Laura; Irwin, Gareth; Bezodis, Ian N; Kerwin, David

2012-01-01

Sprint push-off technique is fundamental to sprint performance and joint stiffness has been identified as a performance-related variable during dynamic movements. However, joint stiffness for the push-off and its relationship with performance (times and velocities) has not been reported. The aim of this study was to quantify and explain lower limb net joint moments and mechanical powers, and ankle stiffness during the first stance phase of the push-off. One elite sprinter performed 10 maximal sprint starts. An automatic motion analysis system (CODA, 200 Hz) with synchronized force plates (Kistler, 1000 Hz) collected kinematic profiles at the hip, knee, and ankle and ground reaction forces, providing input for inverse dynamics analyses. The lower-limb joints predominately extended and revealed a proximal-to-distal sequential pattern of maximal extensor angular velocity and positive power production. Pearson correlations revealed relationships (P < 0.05) between ankle stiffness (5.93 ± 0.75 N x m x deg(-1)) and selected performance variables. Relationships between negative power phase ankle stiffness and horizontal (r = -0.79) and vertical (r = 0.74) centre of mass velocities were opposite in direction to the positive power phase ankle stiffness (horizontal: r = 0.85; vertical: r = -0.54). Thus ankle stiffness may affect the goals of the sprint push-off in different ways, depending on the phase of stance considered.

Idiopathic toe-walking in children, adolescents and young adults: a matter of local or generalised stiffness?

PubMed Central

2011-01-01

Background Idiopathic Toe Walking (ITW) is present in children older than 3 years of age still walking on their toes without signs of neurological, orthopaedic or psychiatric diseases. ITW has been estimated to occur in 7% to 24% of the childhood population. To study associations between Idiopathic Toe Walking (ITW) and decrease in range of joint motion of the ankle joint. To study associations between ITW (with stiff ankles) and stiffness in other joints, muscle strength and bone density. Methods In a cross-sectional study, 362 healthy children, adolescents and young adults (mean age (sd): 14.2 (3.9) years) participated. Range of joint motion (ROM), muscle strength, anthropometrics sport activities and bone density were measured. Results A prevalence of 12% of ITW was found. Nine percent had ITW and severely restricted ROM of the ankle joint. Children with ITW had three times higher chance of severe ROM restriction of the ankle joint. Participants with ITW and stiff ankle joints had a decreased ROM in other joints, whereas bone density and muscle strength were comparable. Conclusion ITW and a decrease in ankle joint ROM might be due to local stiffness. Differential etiological diagnosis should be considered. PMID:21418634

Idiopathic toe-walking in children, adolescents and young adults: a matter of local or generalised stiffness?

PubMed

Engelbert, Raoul; Gorter, Jan Willem; Uiterwaal, Cuno; van de Putte, Elise; Helders, Paul

2011-03-21

Idiopathic Toe Walking (ITW) is present in children older than 3 years of age still walking on their toes without signs of neurological, orthopaedic or psychiatric diseases. ITW has been estimated to occur in 7% to 24% of the childhood population. To study associations between Idiopathic Toe Walking (ITW) and decrease in range of joint motion of the ankle joint. To study associations between ITW (with stiff ankles) and stiffness in other joints, muscle strength and bone density. In a cross-sectional study, 362 healthy children, adolescents and young adults (mean age (sd): 14.2 (3.9) years) participated. Range of joint motion (ROM), muscle strength, anthropometrics sport activities and bone density were measured. A prevalence of 12% of ITW was found. Nine percent had ITW and severely restricted ROM of the ankle joint. Children with ITW had three times higher chance of severe ROM restriction of the ankle joint. Participants with ITW and stiff ankle joints had a decreased ROM in other joints, whereas bone density and muscle strength were comparable. ITW and a decrease in ankle joint ROM might be due to local stiffness. Differential etiological diagnosis should be considered.

Shoe midsole longitudinal bending stiffness and running economy, joint energy, and EMG.

PubMed

Roy, Jean-Pierre R; Stefanyshyn, Darren J

2006-03-01

It has been shown that mechanical energy is dissipated at the metatarsophalangeal (MTP) joint during running and jumping. Furthermore, increasing the longitudinal bending stiffness of the midsole significantly reduced the energy dissipated at the MTP joint and increased jump performance. It was hypothesized that increasing midsole longitudinal bending stiffness would also lead to improvements in running economy. This study investigated the influence of midsole longitudinal bending stiffness on running economy (performance variable) and evaluated the local effects on joint energetics and muscular activity. Carbon fiber plates were inserted into running shoe midsoles and running economy, joint energy, and electromyographic (EMG) data were collected on 13 subjects. Approximately a 1% metabolic energy savings was observed when subjects ran in a stiff midsole relative to the control midsole. Subjects with a greater body mass had a greater decrease in oxygen consumption rates in the stiff midsole relative to the control midsole condition. The stiffer midsoles showed no significant differences in energy absorption at the MTP joint compared with the control shoe. Finally, no significant changes were observed in muscular activation. Increasing midsole longitudinal bending stiffness led to improvements in running economy, yet the underlying mechanisms that can be attributed to this improvement are still not fully understood.

Parameter identification and optimization of slide guide joint of CNC machine tools

NASA Astrophysics Data System (ADS)

Zhou, S.; Sun, B. B.

2017-11-01

The joint surface has an important influence on the performance of CNC machine tools. In order to identify the dynamic parameters of slide guide joint, the parametric finite element model of the joint is established and optimum design method is used based on the finite element simulation and modal test. Then the mode that has the most influence on the dynamics of slip joint is found through harmonic response analysis. Take the frequency of this mode as objective, the sensitivity analysis of the stiffness of each joint surface is carried out using Latin Hypercube Sampling and Monte Carlo Simulation. The result shows that the vertical stiffness of slip joint surface constituted by the bed and the slide plate has the most obvious influence on the structure. Therefore, this stiffness is taken as the optimization variable and the optimal value is obtained through studying the relationship between structural dynamic performance and stiffness. Take the stiffness values before and after optimization into the FEM of machine tool, and it is found that the dynamic performance of the machine tool is improved.

Evaluating the Ergonomic Benefit of a Wrist Brace on Wrist Posture, Muscle Activity, Rotational Stiffness, and Peak Shovel-Ground Impact Force During a Simulated Tree-Planting Task.

PubMed

Sheahan, Peter J; Cashaback, Joshua G A; Fischer, Steven L

2017-09-01

Background Tree planters are at a high risk for wrist injury due to awkward postures and high wrist loads experienced during each planting cycle, specifically at shovel-ground impact. Wrist joint stiffness provides a measure that integrates postural and loading information. Objective The purpose of this study was to evaluate wrist joint stiffness requirements at the instant of shovel-ground impact during tree planting and determine if a wrist brace could alter muscular contributions to wrist joint stiffness. Method Planters simulated tree planting with and without wearing a brace on their planting arm. Surface electromyography (sEMG) from six forearm muscles and wrist kinematics were collected and used to calculate muscular contributions to joint rotational stiffness about the wrist. Results Wrist joint stiffness increased with brace use, an unanticipated and negative consequence of wearing a brace. As a potential benefit, planters achieved a more neutrally oriented wrist angle about the flexion/extension axis, although a less neutral wrist angle about the ulnar/radial axis was observed. Muscle activity did not change between conditions. Conclusion The joint stiffness analysis, combining kinematic and sEMG information in a biologically relevant manner, revealed clear limitations with the interface between the brace grip and shovel handle that jeopardized the prophylactic benefits of the current brace design. This limitation was not as evident when considering kinematics and sEMG data independently. Application A neuromechanical model (joint rotational stiffness) enhanced our ability to evaluate the brace design relative to kinematic and sEMG parameter-based metrics alone.

Spatial and temporal modulation of joint stiffness during multijoint movement.

PubMed

Mah, C D

2001-02-01

Joint stiffness measurements during small transient perturbations have suggested that stiffness during movement is different from that observed during posture. These observations are problematic for theories like the classical equilibrium point hypothesis, which suggest that desired trajectories during movement are enforced by joint stiffness. We measured arm impedances during large, slow perturbations to obtain detailed information about the spatial and temporal modulation of stiffness and viscosity during movement. While our measurements of stiffness magnitudes during movement generally agreed with the results of measurements using fast perturbations, they revealed that joint stiffness undergoes stereotyped changes in magnitude and aspect ratio which depend on the direction of movement and show a strong dependence on joint angles. Movement simulations using measured parameters show that the measured modulation of impedance acts as an energy conserving force field to constrain movement. This mechanism allows for a computationally simplified account of the execution of multijoint movement. While our measurements do not rule out a role for afferent feedback in force generation, the observed stereotyped restoring forces can allow a dramatic relaxation of the accuracy requirements for forces generated by other control mechanisms, such as inverse dynamical models.

Measurement of the passive stiffness of ankle joint in 3 DOF using stewart platform type ankle foot device.

PubMed

Nomura, Kenta; Yonezawa, Teru; Mizoguchi, Hiroshi; Takemura, Hiroshi

2016-08-01

This paper presents a method to measure the passive stiffness of an ankle joint in three degrees of freedom (DOF) under two motion speeds (1 Hz and 5 degree/s) using a developed Stewart platform-type device. The developed device can reproduce input motions of the foot in 6 DOF by controlling six pneumatic linear motion actuators. We used the device to measure the passive stiffness of an ankle joint undergoing three kinds of motion, namely dorsi-plantar flexion, inversion-eversion, and adduction-abduction. The measured values of the passive stiffness of the ankle joint in dorsiflexion that we obtained agreed well with that obtained in a previous study, indicating that the developed device is useful for measuring the passive stiffness of ankle joint. In addition, the developed device can be used to measure the stiffness in inversion-eversion and adduction-abduction motions as well, parameters that have never been measured. The results we obtained demonstrated certain interesting features as we varied both the direction and pace of motion (e.g., there were significant differences in the stiffness not only between adduction and abduction during the faster pace, but also between these and the other motions).

Cell Elasticity Is Regulated by the Tropomyosin Isoform Composition of the Actin Cytoskeleton

PubMed Central

Jalilian, Iman; Heu, Celine; Cheng, Hong; Freittag, Hannah; Desouza, Melissa; Stehn, Justine R.; Bryce, Nicole S.; Whan, Renee M.; Hardeman, Edna C.

2015-01-01

The actin cytoskeleton is the primary polymer system within cells responsible for regulating cellular stiffness. While various actin binding proteins regulate the organization and dynamics of the actin cytoskeleton, the proteins responsible for regulating the mechanical properties of cells are still not fully understood. In the present study, we have addressed the significance of the actin associated protein, tropomyosin (Tpm), in influencing the mechanical properties of cells. Tpms belong to a multi-gene family that form a co-polymer with actin filaments and differentially regulate actin filament stability, function and organization. Tpm isoform expression is highly regulated and together with the ability to sort to specific intracellular sites, result in the generation of distinct Tpm isoform-containing actin filament populations. Nanomechanical measurements conducted with an Atomic Force Microscope using indentation in Peak Force Tapping in indentation/ramping mode, demonstrated that Tpm impacts on cell stiffness and the observed effect occurred in a Tpm isoform-specific manner. Quantitative analysis of the cellular filamentous actin (F-actin) pool conducted both biochemically and with the use of a linear detection algorithm to evaluate actin structures revealed that an altered F-actin pool does not absolutely predict changes in cell stiffness. Inhibition of non-muscle myosin II revealed that intracellular tension generated by myosin II is required for the observed increase in cell stiffness. Lastly, we show that the observed increase in cell stiffness is partially recapitulated in vivo as detected in epididymal fat pads isolated from a Tpm3.1 transgenic mouse line. Together these data are consistent with a role for Tpm in regulating cell stiffness via the generation of specific populations of Tpm isoform-containing actin filaments. PMID:25978408

Multivariable Dynamic Ankle Mechanical Impedance With Relaxed Muscles

PubMed Central

Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

2015-01-01

Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic “peanut” shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed. PMID:24686292

Multivariable dynamic ankle mechanical impedance with relaxed muscles.

PubMed

Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

2014-11-01

Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic "peanut" shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed.

Ankle Joint Intrinsic Dynamics is More Complex than a Mass-Spring-Damper Model.

PubMed

Sobhani Tehrani, Ehsan; Jalaleddini, Kian; Kearney, Robert E

2017-09-01

This paper describes a new small signal parametric model of ankle joint intrinsic mechanics in normal subjects. We found that intrinsic ankle mechanics is a third-order system and the second-order mass-spring-damper model, referred to as IBK, used by many researchers in the literature cannot adequately represent ankle dynamics at all frequencies in a number of important tasks. This was demonstrated using experimental data from five healthy subjects with no voluntary muscle contraction and at seven ankle positions covering the range of motion. We showed that the difference between the new third-order model and the conventional IBK model increased from dorsi to plantarflexed position. The new model was obtained using a multi-step identification procedure applied to experimental input/output data of the ankle joint. The procedure first identifies a non-parametric model of intrinsic joint stiffness where ankle position is the input and torque is the output. Then, in several steps, the model is converted into a continuous-time transfer function of ankle compliance, which is the inverse of stiffness. Finally, we showed that the third-order model is indeed structurally consistent with agonist-antagonist musculoskeletal structure of human ankle, which is not the case for the IBK model.

Biomechanical response to ankle-foot orthosis stiffness during running.

PubMed

Russell Esposito, Elizabeth; Choi, Harmony S; Owens, Johnny G; Blanck, Ryan V; Wilken, Jason M

2015-12-01

The Intrepid Dynamic Exoskeletal Orthosis (IDEO) is an ankle-foot orthosis developed to address the high rates of delayed amputation in the military. Its use has enabled many wounded Service Members to run again. During running, stiffness is thought to influence an orthosis' energy storage and return mechanical properties. This study examined the effect of orthosis stiffness on running biomechanics in patients with lower limb impairments who had undergone unilateral limb salvage. Ten patients with lower limb impairments underwent gait analysis at a self-selected running velocity. 1. Nominal (clinically-prescribed), 2. Stiff (20% stiffer than nominal), and 3. Compliant (20% less stiff than nominal) ankle-foot orthosis stiffnesses were tested. Ankle joint stiffness was greatest in the stiffest strut and lowest in the compliant strut, however ankle mechanical work remained unchanged. Speed, stride length, cycle time, joint angles, moments, powers, and ground reaction forces were not significantly different among stiffness conditions. Ankle joint kinematics and ankle, knee and hip kinetics were different between limbs. Ankle power, in particular, was lower in the injured limb. Ankle-foot orthosis stiffness affected ankle joint stiffness but did not influence other biomechanical parameters of running in individuals with unilateral limb salvage. Foot strike asymmetries may have influenced the kinetics of running. Therefore, a range of stiffness may be clinically appropriate when prescribing ankle-foot orthoses for active individuals with limb salvage. Published by Elsevier Ltd.

An experimental and morphometric test of the relationship between vertebral morphology and joint stiffness in Nile crocodiles (Crocodylus niloticus).

PubMed

Molnar, Julia L; Pierce, Stephanie E; Hutchinson, John R

2014-03-01

Despite their semi-aquatic mode of life, modern crocodylians use a wide range of terrestrial locomotor behaviours, including asymmetrical gaits otherwise only found in mammals. The key to these diverse abilities may lie in the axial skeleton. Correlations between vertebral morphology and both intervertebral joint stiffness and locomotor behaviour have been found in other animals, but the vertebral mechanics of crocodylians have not yet been experimentally and quantitatively tested. We measured the passive mechanics and morphology of the thoracolumbar vertebral column in Crocodylus niloticus in order to validate a method to infer intervertebral joint stiffness based on morphology. Passive stiffness of eight thoracic and lumbar joints was tested in dorsal extension, ventral flexion and mediolateral flexion using cadaveric specimens. Fifteen measurements that we deemed to be potential correlates of stiffness were taken from each vertebra and statistically tested for correlation with joint stiffness. We found that the vertebral column of C. niloticus is stiffer in dorsoventral flexion than in lateral flexion and, in contrast to that of many mammals, shows an increase in joint stiffness in the lumbar region. Our findings suggest that the role of the axial column in crocodylian locomotion may be functionally different from that in mammals, even during analogous gaits. A moderate proportion of variation in joint stiffness (R(2)=0.279-0.520) was predicted by centrum width and height, neural spine angle and lamina width. These results support the possible utility of some vertebral morphometrics in predicting mechanical properties of the vertebral column in crocodiles, which also should be useful for forming functional hypotheses of axial motion during locomotion in extinct archosaurs.

Joint stability characteristics of the ankle complex after lateral ligamentous injury, part I: a laboratory comparison using arthrometric measurement.

PubMed

Kovaleski, John E; Heitman, Robert J; Gurchiek, Larry R; Hollis, J M; Liu, Wei; Pearsall, Albert W

2014-01-01

The mechanical property of stiffness may be important to investigating how lateral ankle ligament injury affects the behavior of the viscoelastic properties of the ankle complex. A better understanding of injury effects on tissue elastic characteristics in relation to joint laxity could be obtained from cadaveric study. To biomechanically determine the laxity and stiffness characteristics of the cadaver ankle complex before and after simulated injury to the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) during anterior drawer and inversion loading. Cross-sectional study. University research laboratory. Seven fresh-frozen cadaver ankle specimens. All ankles underwent loading before and after simulated lateral ankle injury using an ankle arthrometer. The dependent variables were anterior displacement, anterior end-range stiffness, inversion rotation, and inversion end-range stiffness. Isolated ATFL and combined ATFL and CFL sectioning resulted in increased anterior displacement but not end-range stiffness when compared with the intact ankle. With inversion loading, combined ATFL and CFL sectioning resulted in increased range of motion and decreased end-range stiffness when compared with the intact and ATFL-sectioned ankles. The absence of change in anterior end-range stiffness between the intact and ligament-deficient ankles indicated bony and other soft tissues functioned to maintain stiffness after pathologic joint displacement, whereas inversion loading of the CFL-deficient ankle after pathologic joint displacement indicated the ankle complex was less stiff when supported only by the secondary joint structures.

Subspace methods for identification of human ankle joint stiffness.

PubMed

Zhao, Y; Westwick, D T; Kearney, R E

2011-11-01

Joint stiffness, the dynamic relationship between the angular position of a joint and the torque acting about it, describes the dynamic, mechanical behavior of a joint during posture and movement. Joint stiffness arises from both intrinsic and reflex mechanisms, but the torques due to these mechanisms cannot be measured separately experimentally, since they appear and change together. Therefore, the direct estimation of the intrinsic and reflex stiffnesses is difficult. In this paper, we present a new, two-step procedure to estimate the intrinsic and reflex components of ankle stiffness. In the first step, a discrete-time, subspace-based method is used to estimate a state-space model for overall stiffness from the measured overall torque and then predict the intrinsic and reflex torques. In the second step, continuous-time models for the intrinsic and reflex stiffnesses are estimated from the predicted intrinsic and reflex torques. Simulations and experimental results demonstrate that the algorithm estimates the intrinsic and reflex stiffnesses accurately. The new subspace-based algorithm has three advantages over previous algorithms: 1) It does not require iteration, and therefore, will always converge to an optimal solution; 2) it provides better estimates for data with high noise or short sample lengths; and 3) it provides much more accurate results for data acquired under the closed-loop conditions, that prevail when subjects interact with compliant loads.

Effect of static foot posture on the dynamic stiffness of foot joints during walking.

PubMed

Sanchis-Sales, E; Sancho-Bru, J L; Roda-Sales, A; Pascual-Huerta, J

2018-05-01

The static foot posture has been related to the development of lower limb injuries. This study aimed to investigate the dynamic stiffness of foot joints during gait in the sagittal plane to understand the role of the static foot posture in the development of injuries. Seventy healthy adult male subjects with different static postures, assessed by the Foot Posture Index (FPI) (30 normal, 20 highly pronated and 20 highly supinated), were recruited. Kinematic and kinetic data were recorded using an optical motion capture system and a pressure platform, and dynamic stiffness at the different stages of the stance was calculated from the slopes of the linear regression on the flexion moment-angle curves. The effect of foot type on dynamic stiffness and on ranges of motion and moments was analysed using ANOVAs and post-hoc tests, and linear correlation between dynamic stiffness and FPI was also tested. Highly pronated feet showed a significantly smaller range of motion at the ankle and metatarsophalangeal joints and also a larger range of moments at the metatarsophalangeal joint than highly supinated feet. Dynamic stiffness during propulsion was significantly greater at all foot joints for highly pronated feet, with positive significant correlations with the squared FPI. Highly supinated feet showed greater dynamic stiffness than normal feet, although to a lesser extent. Highly pronated feet during normal gait experienced the greatest decrease in the dorsiflexor moments during propulsion, normal feet being the most balanced regarding work generated and absorbed. Extreme static foot postures show greater dynamic stiffness during propulsion and greater absorbed work, which increases the risk of developing injuries. The data presented may be used when designing orthotics or prostheses, and also when planning surgery that modifies joint stiffness. Copyright © 2018 Elsevier B.V. All rights reserved.

Management of the Stiff Finger: Evidence and Outcomes

PubMed Central

Yang, Guang; McGlinn, Evan P.; Chung, Kevin C.

2014-01-01

SYNOPSIS The term “stiff finger” refers to a reduction in the range of motion in the finger, and it is a condition that has many different causes and involves a number of different structures. Almost all injuries of the fingers and some diseases can cause finger stiffness. Hand surgeons often face difficulty treating stiff fingers that are affected by irreversible soft tissues fibrosis. Stiff fingers can be divided into flexion and extension deformities. They can also be sub-classified into four categories according to the involved tissues extending from the skin to the joint capsule. Prevention of stiff fingers by judicious mobilization of the joints is prudent to avoid more complicated treatment after established stiffness occurs. Static progressive and dynamic splints have been considered as effective non-operative interventions to treat stiff fingers. Most authors believe force of joint distraction and time duration of stretching are two important factors to consider while applying a splint or cast. We also introduce the concepts of capsulotomy and collateral ligament release and other soft tissue release of the MCP and PIP joint in this article. Future outcomes research is vital to assessing the effectiveness of these surgical procedures and guiding postoperative treatment recommendations. PMID:24996467

A torsional MRE joint for a C-shaped robotic leg

NASA Astrophysics Data System (ADS)

Christie, M. D.; Sun, S. S.; Ning, D. H.; Du, H.; Zhang, S. W.; Li, W. H.

2017-01-01

Serving to improve stability and energy efficiency during locomotion, in nature, animals modulate their leg stiffness to adapt to their terrain. Now incorporated into many locomotive robot designs, such compliance control can enable disturbance rejection and improved transition between changing ground conditions. This paper presents a novel design of a variable stiffness leg utilizing a magnetorheological elastomer joint in a literal rolling spring loaded inverted pendulum (R-SLIP) morphology. Through the semi-active control of this hybrid permanent-magnet and coil design, variable stiffness is realized, offering a design which is capable of both softening and stiffening in an adaptive sort of way, with a maximum stiffness change of 48.0%. Experimental characterization first serves to assess the stiffness variation capacity of the torsional joint, and through later comparison with force testing of the leg, the linear stiffness is characterized with the R-SLIP-like behavior of the leg being demonstrated. Through the force relationships applied, a generalized relationship for determining linear stiffness based on joint rotation angle is also proposed, further aiding experimental validation.

Measuring Multi-Joint Stiffness during Single Movements: Numerical Validation of a Novel Time-Frequency Approach

PubMed Central

Piovesan, Davide; Pierobon, Alberto; DiZio, Paul; Lackner, James R.

2012-01-01

This study presents and validates a Time-Frequency technique for measuring 2-dimensional multijoint arm stiffness throughout a single planar movement as well as during static posture. It is proposed as an alternative to current regressive methods which require numerous repetitions to obtain average stiffness on a small segment of the hand trajectory. The method is based on the analysis of the reassigned spectrogram of the arm's response to impulsive perturbations and can estimate arm stiffness on a trial-by-trial basis. Analytic and empirical methods are first derived and tested through modal analysis on synthetic data. The technique's accuracy and robustness are assessed by modeling the estimation of stiffness time profiles changing at different rates and affected by different noise levels. Our method obtains results comparable with two well-known regressive techniques. We also test how the technique can identify the viscoelastic component of non-linear and higher than second order systems with a non-parametrical approach. The technique proposed here is very impervious to noise and can be used easily for both postural and movement tasks. Estimations of stiffness profiles are possible with only one perturbation, making our method a useful tool for estimating limb stiffness during motor learning and adaptation tasks, and for understanding the modulation of stiffness in individuals with neurodegenerative diseases. PMID:22448233

An under-actuated origami gripper with adjustable stiffness joints for multiple grasp modes

NASA Astrophysics Data System (ADS)

Firouzeh, Amir; Paik, Jamie

2017-05-01

Under-actuated robots offer multiple degrees of freedom without much added complexity to the actuation and control. Utilizing adjustable stiffness joints in these robots allows us to control their stable configurations and their mode of interaction with the environment. In this paper, we present the design of tendon-driven robotic origami (robogami) joints with adjustable stiffness. The proposed designs allow us to place joints along any direction in the plane of the robot and in the normal direction to the plane. The layer-by-layer manufacturing of robogamis facilitates the design and manufacturing of robots with different arrangement of joints for different applications. We use thermally activated shape memory polymer to control the joint stiffness. The manufacturing of the polymer layer is compatible with the layer-by-layer manufacturing process of the robogamis which results in scalable and customizable robots. To demonstrate, we prototyped an under-actuated gripper with three fingers and only one input actuation. The grasp mode of the gripper is set by adjusting the configuration of the locked joints and modulating the stiffness of the active joints. We present a model to estimate the configuration and the contact forces of the gripper at different settings that will assist us in design and control of future generation of under-actuated robogamis.

Muscle contributions to elbow joint rotational stiffness in preparation for sudden external arm perturbations.

PubMed

Holmes, Michael W R; Keir, Peter J

2014-04-01

Understanding joint stiffness and stability is beneficial for assessing injury risk. The purpose of this study was to examine joint rotational stiffness for individual muscles contributing to elbow joint stability. Fifteen male participants maintained combinations of three body orientations (standing, supine, sitting) and three hand preloads (no load, solid tube, fluid filled tube) while a device imposed a sudden elbow extension. Elbow angle and activity from nine muscles were inputs to a biomechanical model to determine relative contributions to elbow joint rotational stiffness, reported as percent of total stiffness. A body orientation by preload interaction was evident for most muscles (P<.001). Brachioradialis had the largest change in contribution while standing (no load, 18.5%; solid, 23.8%; fluid, 26.3%). Across trials, the greatest contributions were brachialis (30.4±1.9%) and brachioradialis (21.7±2.2%). Contributions from the forearm muscles and triceps were 5.5±0.6% and 9.2±1.9%, respectively. Contributions increased at time points closer to the perturbation (baseline to anticipatory), indicating increased neuromuscular response to resist rotation. This study quantified muscle contributions that resist elbow perturbations, found that forearm muscles contribute marginally and showed that orientation and preload should be considered when evaluating elbow joint stiffness and safety.

Research regarding stiffness optimization of wires used for joints actuation from an elephant's trunk robotic arm

NASA Astrophysics Data System (ADS)

Ciofu, C.; Stan, G.

2016-11-01

Elephant's trunk robotic arms driven by wires and pulley mechanisms have issues with wires stiffness because of the entailed elastic deformations that is causing errors of positioning. Static and dynamic loads from each joint of the robotic arm affect the stiffness of driving wires and precision positioning. The influence of wires elastic deformation on precision positioning decreases with the increasing of wires stiffness by using different pre-tensioning devices. In this paper, we analyze the variation of driving wires stiffness particularly to each wire driven joint. We obtain optimum wires stiffness variation by using an analytical method that highlights the efficiency of pre-tensioning mechanism. The analysis of driving wires stiffness is necessary for taking appropriate optimization measures of robotic arm dynamic behavior and, thus, for decreasing positioning errors of the elephant's trunk robotic arm with inner actuation through wires/cables.

Comparison of neuromuscular abnormalities between upper and lower extremities in hemiparetic stroke.

PubMed

Mirbagheri, M M; AliBiglou, L; Thajchayapong, M; Lilaonitkul, T; Rymer, W Z

2006-01-01

We studied the neuromuscular mechanical properties of the elbow and ankle joints in chronic, hemiparetic stroke patients and healthy subjects. System identification techniques were used to characterize the mechanical abnormalities of these joints and to identify the contribution of intrinsic and reflex stiffness to these abnormalities. Modulation of intrinsic and reflex stiffness with the joint angle was studied by applying PRBS perturbations to the joint at different joint angles. The experiments were performed for both spastic (stroke) and contralateral (control) sides of stroke patients and one side of healthy (normal) subjects. We found reflex stiffness gain (GR) was significantly larger in the stroke than the control side for both elbow and ankle joints. GR was also strongly position dependent in both joints. However, the modulation of GR with position was slightly different in two joints. GR was also larger in the control than the normal joints but the differences were significant only for the ankle joint. Intrinsic stiffness gain (K) was also significantly larger in the stroke than the control joint at elbow extended positions and at ankle dorsiflexed positions. Modulation of K with the ankle angle was similar for stroke, control and normal groups. In contrast, the position dependency of the elbow was different. K was larger in the control than normal ankle whereas it was lower in the control than normal elbow. However, the differences were not significant for any joint. The findings demonstrate that both reflex and intrinsic stiffness gain increase abnormally in both upper and lower extremities. However, the major contribution of intrinsic and reflex stiffness to the abnormalities is at the end of ROM and at the middle ROM, respectively. The results also demonstrate that the neuromuscular properties of the contralateral limb are not normal suggesting that it may not be used as a suitable control at least for the ankle study.

Comparison of cervical spine stiffness in individuals with chronic nonspecific neck pain and asymptomatic individuals.

PubMed

Ingram, Lewis A; Snodgrass, Suzanne J; Rivett, Darren A

2015-03-01

Clinical measurement, cross-sectional. To determine if spinal joint stiffness is different in individuals with nonspecific neck pain, and whether stiffness magnitude is associated with pain intensity and disability. Manual therapists commonly evaluate spinal joint stiffness in patients presenting with nonspecific neck pain. However, a relationship between stiffness and neck pain has not yet been demonstrated. Spinal stiffness at C7 was objectively measured in participants with chronic nonspecific neck pain whose symptomatic spinal level was identified as C7 (n = 12) and in age- and sex-matched asymptomatic controls (n = 12). Stiffness (slope of the linear region of the force-displacement curve) was quantified using a device that applied 5 standardized mechanical force cycles to the C7 spinous process, while concurrently measuring displacement and resistance to movement. Stiffness was compared between groups using an independent t test. Spearman rho and Pearson r were used to determine the extent to which stiffness magnitude was associated with pain intensity (visual analog scale) and level of disability (Neck Disability Index), respectively, in the group with neck pain. Participants with nonspecific neck pain had greater spinal joint stiffness at C7 compared with asymptomatic individuals (mean difference, 1.78 N/mm; 95% confidence interval: 0.28, 3.27; P = .022). However, stiffness magnitude in the group with neck pain was not associated (P>.05) with pain intensity or level of disability. These preliminary results suggest that cervical spine stiffness may be greater in the presence of nonspecific neck pain. However, judgments regarding pain intensity and level of disability should not be inferred from examinations of spinal joint stiffness.

Determination of Ankle and Metatarsophalangeal Stiffness During Walking and Jogging.

PubMed

Mager, Fabian; Richards, Jim; Hennies, Malika; Dötzel, Eugen; Chohan, Ambreen; Mbuli, Alex; Capanni, Felix

2018-05-29

Forefoot stiffness has been shown to influence joint biomechanics. However, little or no data exists on metatarsophalangeal stiffness. Twenty-four healthy rearfoot strike runners were recruited from a staff and student population at the University of Central Lancashire. Five repetitions of shod, self-selected speed level walking and jogging were performed. Kinetic and kinematic data were collected using retro-reflective markers placed on the lower limb and foot, to create a three-segment foot model using the Calibrated Anatomical System Technique. Ankle and metatarsophalangeal moments and angles were calculated. Stiffness values were calculated using a linear best fit line of moment versus of angle plots. Paired t-tests were used to compare values between walking and jogging conditions. Significant differences were seen in ankle range of motion (ROM), but not in metatarsophalangeal ROM. Maximum moments were significantly greater in the ankle during jogging, but these were not significantly different at the metatarsophalangeal joint. Average ankle joint stiffness exhibited significantly lower stiffness when walking compared to jogging. However, the metatarsophalangeal joint exhibited significantly greater stiffness when walking compared to jogging. A greater understanding of forefoot stiffness may inform the development of footwear, prosthetic feet and orthotic devices, such as ankle-foot orthoses for walking and sporting activities.

Lower Body Stiffness Modulation Strategies in Well Trained Female Athletes.

PubMed

Millett, Emma L; Moresi, Mark P; Watsford, Mark L; Taylor, Paul G; Greene, David A

2016-10-01

Millett, EL, Moresi, MP, Watsford, ML, Taylor, PG, and Greene, DA. Lower body stiffness modulation strategies in well trained female athletes. J Strength Cond Res 30(10): 2845-2856, 2016-Lower extremity stiffness quantifies the relationship between the amount of leg compression and the external load to which the limb are subjected. This study aimed to assess differences in leg and joint stiffness and the subsequent kinematic and kinetic control mechanisms between athletes from various training backgrounds. Forty-seven female participants (20 nationally identified netballers, 13 high level endurance athletes and 14 age and gender matched controls) completed a maximal unilateral countermovement jump, drop jump and horizontal jump to assess stiffness. Leg stiffness, joint stiffness and associated mechanical parameters were assessed with a 10 camera motion analysis system and force plate. No significant differences were evident for leg stiffness measures between athletic groups for any of the tasks (p = 0.321-0.849). However, differences in joint stiffness and its contribution to leg stiffness, jump performance outcome measures and stiffness control mechanisms were evident between all groups. Practitioners should consider the appropriateness of the task utilised in leg stiffness screening. Inclusion of mechanistic and/or more sports specific tasks may be more appropriate for athletic groups.

Knee joint laxity and passive stiffness in meniscectomized patients compared with healthy controls.

PubMed

Thorlund, Jonas B; Creaby, Mark W; Wrigley, Tim V; Metcalf, Ben R; Bennell, Kim L

2014-10-01

Passive mechanical behavior of the knee in the frontal plane, measured as angular laxity and mechanical stiffness, may play an important role in the pathogenesis of knee osteoarthritis (OA). Little is known about knee laxity and stiffness prior to knee OA onset. We investigated knee joint angular laxity and passive stiffness in meniscectomized patients at high risk of knee OA compared with healthy controls. Sixty patients meniscectomized for a medial meniscal tear (52 men, 41.4 ± 5.5 years, 175.3 ± 7.9 cm, 83.6 ± 12.8 kg, mean ± SD) and 21 healthy controls (18 men, 42.0 ± 6.7 years, 176.8 ± 5.7 cm, 77.8 ± 13.4 kg) had their knee joint angular laxity and passive stiffness assessed twice ~2.3 years apart. Linear regression models including age, sex, height and body mass as covariates in the adjusted model were used to assess differences between groups. Greater knee joint varus (-10.1 vs. -7.3°, p<0.001), valgus (7.1 vs. 5.6°, p=0.001) and total (17.2 vs. 12.9°, p<0.001) angular laxity together with reduced midrange passive stiffness (1.71 vs. 2.36 Nm/°, p<0.001) were observed in patients vs. healthy controls. No differences were observed in change in stiffness over time between patients and controls, however a tendency towards increased laxity in patients was seen. Meniscectomized patients showed increased knee joint angular laxity and reduced passive stiffness ~3 months post surgery compared with controls. In addition, the results indicated that knee joint laxity may increase over time in meniscectomized patients. Copyright © 2014 Elsevier B.V. All rights reserved.

Interlimb symmetry of dynamic knee joint stiffness and co-contraction is maintained in early stage knee osteoarthritis.

PubMed

Collins, A T; Richardson, R T; Higginson, J S

2014-08-01

Individuals with knee OA often exhibit greater co-contraction of antagonistic muscle groups surrounding the affected joint which may lead to increases in dynamic joint stiffness. These detrimental changes in the symptomatic limb may also exist in the contralateral limb, thus contributing to its risk of developing knee osteoarthritis. The purpose of this study is to investigate the interlimb symmetry of dynamic knee joint stiffness and muscular co-contraction in knee osteoarthritis. Muscular co-contraction and dynamic knee joint stiffness were assessed in 17 subjects with mild to moderate unilateral medial compartment knee osteoarthritis and 17 healthy control subjects while walking at a controlled speed (1.0m/s). Paired and independent t-tests determined whether significant differences exist between groups (p<0.05). There were no significant differences in dynamic joint stiffness or co-contraction between the OA symptomatic and OA contralateral group (p=0.247, p=0.874, respectively) or between the OA contralateral and healthy group (p=0.635, p=0.078, respectively). There was no significant difference in stiffness between the OA symptomatic and healthy group (p=0.600); however, there was a slight trend toward enhanced co-contraction in the symptomatic knees compared to the healthy group (p=0.051). Subjects with mild to moderate knee osteoarthritis maintain symmetric control strategies during gait. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interlimb symmetry of dynamic knee joint stiffness and co-contraction is maintained in early stage knee osteoarthritis

PubMed Central

Collins, A.T.; Richardson, R.T.; Higginson, J.S.

2014-01-01

Individuals with knee OA often exhibit greater co-contraction of antagonistic muscle groups surrounding the affected joint which may lead to increases in dynamic joint stiffness. These detrimental changes in the symptomatic limb may also exist in the contralateral limb, thus contributing to its risk of developing knee osteoarthritis. The purpose of this study is to investigate the interlimb symmetry of dynamic knee joint stiffness and muscular co-contraction in knee osteoarthritis. Muscular co-contraction and dynamic knee joint stiffness were assessed in 17 subjects with mild to moderate unilateral medial compartment knee osteoarthritis and 17 healthy control subjects while walking at a controlled speed (1.0 m/s). Paired and independent t-tests determined whether significant differences exist between groups (p < 0.05). There were no significant differences in dynamic joint stiffness or co-contraction between the OA symptomatic and OA contralateral group (p = 0.247, p = 0.874, respectively) or between the OA contralateral and healthy group (p = 0.635, p = 0.078, respectively). There was no significant difference in stiffness between the OA symptomatic and healthy group (p = 0.600); however, there was a slight trend toward enhanced co-contraction in the symptomatic knees compared to the healthy group (p = 0.051). Subjects with mild to moderate knee osteoarthritis maintain symmetric control strategies during gait. PMID:24768278

Biomechanics of an orthosis-managed cranial cruciate ligament-deficient canine stifle joint predicted by use of a computer model.

PubMed

Bertocci, Gina E; Brown, Nathan P; Mich, Patrice M

2017-01-01

OBJECTIVE To evaluate effects of an orthosis on biomechanics of a cranial cruciate ligament (CrCL)-deficient canine stifle joint by use of a 3-D quasistatic rigid-body pelvic limb computer model simulating the stance phase of gait and to investigate influences of orthosis hinge stiffness (durometer). SAMPLE A previously developed computer simulation model for a healthy 33-kg 5-year-old neutered Golden Retriever. PROCEDURES A custom stifle joint orthosis was implemented in the CrCL-deficient pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation in the orthosis-stabilized stifle joint (baseline scenario; high-durometer hinge]) were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints. Sensitivity analysis was conducted to evaluate the influence of orthosis hinge stiffness on model outcome measures. RESULTS The orthosis decreased loads placed on the caudal cruciate and lateral collateral ligaments and increased load placed on the medial collateral ligament, compared with loads for the CrCL-intact stifle joint. Ligament loads were decreased in the orthosis-managed CrCL-deficient stifle joint, compared with loads for the CrCL-deficient stifle joint. Relative tibial translation and rotation decreased but were not eliminated after orthosis management. Increased orthosis hinge stiffness reduced tibial translation and rotation, whereas decreased hinge stiffness increased internal tibial rotation, compared with values for the baseline scenario. CONCLUSIONS AND CLINICAL RELEVANCE Stifle joint biomechanics were improved following orthosis implementation, compared with biomechanics of the CrCL-deficient stifle joint. Orthosis hinge stiffness influenced stifle joint biomechanics. An orthosis may be a viable option to stabilize a CrCL-deficient canine stifle joint.

Influence of Joint Flexibility on Vibration Analysis of Free-Free Beams

NASA Astrophysics Data System (ADS)

Gunda, Jagadish Babu; Krishna, Y.

2014-12-01

In present work, joint flexibility (or looseness) of the free-free beam is investigated by using a two noded beam finite element formulation with transverse displacement and joint rotations as the degrees of freedom per node at joint location. Flexibility of the joint is primarily represented by means of a rotational spring analogy, where the stiffness of the rotational spring characterizes the looseness of the flexible joint for an applied bending moment. Influence of joint location as well as joint stiffness on modal behavior of first five modes of slender, uniform free-free beams are discussed for various values of non-dimensional rotational spring stiffness parameter. Numerical accuracy of the results obtained from the present finite element formulation are validated by using the commercially available finite element software which shows the confidence gained on the numerical results discussed in the present study.

Soft tissue balance changes depending on joint distraction force in total knee arthroplasty.

PubMed

Nagai, Kanto; Muratsu, Hirotsugu; Matsumoto, Tomoyuki; Miya, Hidetoshi; Kuroda, Ryosuke; Kurosaka, Masahiro

2014-03-01

The influence of joint distraction force on intraoperative soft tissue balance was evaluated using Offset Repo-Tensor® for 78 knees that underwent primary posterior-stabilized total knee arthroplasty. The joint center gap and varus ligament balance were measured between osteotomized surfaces using 20, 40 and 60 lbs of joint distraction force. These values were significantly increased at extension and flexion as the distraction force increased. Furthermore, lateral compartment stiffness was significantly lower than medial compartment stiffness. Thus, larger joint distraction forces led to larger varus ligament balance and joint center gap, because of the difference in soft tissue stiffness between lateral and medial compartments. These findings indicate the importance of the strength of joint distraction force in the assessment of soft tissue balance, especially when using gap-balancing technique. © 2014.

Effect of joint mechanism on vehicle redirectional capability of water-filled road safety barrier systems.

PubMed

Thiyahuddin, M I; Thambiratnam, D P; Gu, Y T

2014-10-01

Portable water-filled barriers (PWFBs) are roadside appurtenances that prevent vehicles from penetrating into temporary construction zones on roadways. PWFBs are required to satisfy the strict regulations for vehicle re-direction in tests. However, many of the current PWFBs fail to re-direct the vehicle at high speeds due to the inability of the joints to provide appropriate stiffness. The joint mechanism hence plays a crucial role in the performance of a PWFB system at high speed impacts. This paper investigates the desired features of the joint mechanism in a PWFB system that can re-direct vehicles at high speeds, while limiting the lateral displacement to acceptable limits. A rectangular "wall" representative of a 30m long barrier system was modeled and a novel method of joining adjacent road barriers was introduced through appropriate pin-joint connections. The impact response of the barrier "wall" and the vehicle was obtained and the results show that a rotational stiffness of 3000kNm/rad at the joints seems to provide the desired features of the PWFB system to re-direct impacting vehicles and restrict the lateral deflection. These research findings will be useful to safety engineers and road barrier designers in developing a new generation of PWFBs for increased road safety. Copyright © 2014 Elsevier Ltd. All rights reserved.

Acromioclavicular joint dislocations: coracoclavicular reconstruction with and without additional direct acromioclavicular repair.

PubMed

Weiser, Lukas; Nüchtern, Jakob V; Sellenschloh, Kay; Püschel, Klaus; Morlock, Michael M; Rueger, Johannes M; Hoffmann, Michael; Lehmann, Wolfgang; Großterlinden, Lars G

2017-07-01

To evaluate different stabilisation techniques for acromioclavicular (AC) joint separations, including direct AC repair, and to compare the properties of the stabilised and native joints. An established in vitro testing model for the AC joint was used to analyse joint stability after surgical reconstruction [double TightRope (DTR), DTR with AC repair (DTR + AC), single TR with AC repair (TR + AC), and PDS sling with AC repair (PDS + AC)]. Twenty-four human cadaveric shoulders were randomised by age into four testing groups. Joint stiffness was measured by applying an axial load during defined physiological ranges of motion. Similar tests were performed for the native joints, after dissecting the coracoclavicular and AC ligaments, and after surgical reconstruction. Cyclic loading was performed for 1000 cycles with 20-70 N and vertical load to failure determined after cyclic testing. Axial stiffness for all TR groups was significantly higher than for the native joint (DTR 38.94 N/mm, p = 0.005; DTR + AC 37.79 N/mm, p = 0.015; TR + AC 45.61 N/mm, p < 0.001 vs. native 26.05 N/mm). The axial stiffness of the PDS + AC group was similar to that of the native joint group (21.4 N/mm, n.s.). AC repair did not significantly influence rotational stiffness. Load to failure was similar and >600 N in all groups (n.s.). Reconstruction of AC dislocations with one or two TRs leads to stable results with a higher stiffness than the native joints. For the PDS + AC group, axial stiffness was similar to the native situation, although there might be a risk of elongation. Direct AC repair showed no significantly increased stability in comparison with reconstructions without direct AC repair. Thus, a direct AC repair seems to be dispensable in clinical practice, while TRs or PDS cerclages appear to provide sufficiently stable results.

Lower Extremity Stiffness Changes after Concussion in Collegiate Football Players.

PubMed

Dubose, Dominique F; Herman, Daniel C; Jones, Deborah L; Tillman, Susan M; Clugston, James R; Pass, Anthony; Hernandez, Jorge A; Vasilopoulos, Terrie; Horodyski, Marybeth; Chmielewski, Terese L

2017-01-01

Recent research indicates that a concussion increases the risk of musculoskeletal injury. Neuromuscular changes after concussion might contribute to the increased risk of injury. Many studies have examined gait postconcussion, but few studies have examined more demanding tasks. This study compared changes in stiffness across the lower extremity, a measure of neuromuscular function, during a jump-landing task in athletes with a concussion (CONC) to uninjured athletes (UNINJ). Division I football players (13 CONC and 26 UNINJ) were tested pre- and postseason. A motion capture system recorded subjects jumping on one limb from a 25.4-cm step onto a force plate. Hip, knee, and ankle joint stiffness were calculated from initial contact to peak joint flexion using the regression line slopes of the joint moment versus the joint angle plots. Leg stiffness was (peak vertical ground reaction force [PVGRF]/lower extremity vertical displacement) from initial contact to peak vertical ground reaction force. All stiffness values were normalized to body weight. Values from both limbs were averaged. General linear models compared group (CONC, UNINJ) differences in the changes of pre- and postseason stiffness values. Average time from concussion to postseason testing was 49.9 d. The CONC group showed an increase in hip stiffness (P = 0.03), a decrease in knee (P = 0.03) and leg stiffness (P = 0.03), but no change in ankle stiffness (P = 0.65) from pre- to postseason. Lower extremity stiffness is altered after concussion, which could contribute to an increased risk of lower extremity injury. These data provide further evidence of altered neuromuscular function after concussion.

Lower Extremity Stiffness Changes following Concussion in Collegiate Football Players

PubMed Central

DuBose, Dominique F.; Herman, Daniel C.; Jones, Debi L.; Tillman, Susan M.; Clugston, James R.; Pass, Anthony; Hernandez, Jorge A.; Vasilopoulos, Terrie; Horodyski, MaryBeth; Chmielewski, Terese L.

2016-01-01

Purpose Recent research indicates that a concussion increases risk of musculoskeletal injury. Neuromuscular changes following concussion might contribute to the increased risk of injury. Many studies have examined gait post-concussion, but few studies have examined more demanding tasks. This study compared changes in stiffness across the lower extremity, a measure of neuromuscular function, during a jump-landing task in athletes with a concussion (CONC) to uninjured athletes (UNINJ). Methods Division I football players (13 CONC, 26 UNINJ) were tested pre- and post-season. A motion-capture system recorded subjects jumping on one limb from a 25.4 cm step onto a force plate. Hip, knee, and ankle joint stiffness were calculated from initial contact to peak joint flexion using the regression line slopes of the joint moment versus joint angle plots. Leg stiffness was (peak vertical ground reaction force (PVGRF)/lower extremity vertical displacement) from initial contact to PVGRF. All stiffness values were normalized to bodyweight. Values from both limbs were averaged. General linear models compared group (CONC, UNINJ) differences in the changes of pre- and post-season stiffness values. Results Average time from concussion to post-season testing was 49.9 days. The CONC group showed an increase in hip stiffness (p=0.03), a decrease in knee (p=0.03) and leg stiffness (p=0.03), but no change in ankle stiffness (p=0.65) from pre- to post-season. Conclusion Lower extremity stiffness is altered following concussion, which could contribute to an increased risk of lower extremity injury. These data provide further evidence of altered neuromuscular function after concussion. PMID:27501359

Independent control of joint stiffness in the framework of the equilibrium-point hypothesis.

PubMed

Latash, M L

1992-01-01

In the framework of the equilibrium-point hypothesis, virtual trajectories and joint stiffness patterns have been reconstructed during two motor tasks practiced against a constant bias torque. One task required a voluntary increase in joint stiffness while preserving the original joint position. The other task involved fast elbow flexions over 36 degrees. Joint stiffness gradually subsided after the termination of fast movements. In both tasks, the external torque could slowly and unexpectedly change. The subjects were required not to change their motor commands if the torque changed, i.e. "to do the same no matter what the motor did". In both tasks, changes in joint stiffness were accompanied by unchanged virtual trajectories that were also independent of the absolute value of the bias torque. By contrast, the intercept of the joint compliant characteristic with the angle axis, r(t)-function, has demonstrated a clear dependence upon both the level of coactivation and external load. We assume that a template virtual trajectory is generated at a certain level of the motor hierarchy and is later scaled taking into account some commonly changing dynamic factors of the movement execution, for example, external load. The scaling leads to the generation of commands to the segmental structures that can be expressed, according to the equilibrium-point hypothesis, as changes in the thresholds of the tonic stretch reflex for corresponding muscles.

Bioinspired Robotic Fingers Based on Pneumatic Actuator and 3D Printing of Smart Material.

PubMed

Yang, Yang; Chen, Yonghua; Li, Yingtian; Chen, Michael Z Q; Wei, Ying

2017-06-01

In this article, we have proposed a novel robotic finger design principle aimed to address two challenges in soft pneumatic grippers-the controllability of the stiffness and the controllability of the bending position. The proposed finger design is composed of a 3D printed multimaterial substrate and a soft pneumatic actuator. The substrate has four polylactic acid (PLA) segments interlocked with three shape memory polymer (SMP) joints, inspired by bones and joints in human fingers. By controlling the thermal energy of an SMP joint, the stiffness of the joints is modulated due to the dramatic change in SMP elastic modulus around its glass transition temperature (T g ). When SMP joints are heated above T g , they exhibit very small stiffness, allowing the finger to easily bend around the SMP joints if the attached soft actuator is actuated. When there is no force from the soft actuator, shape recovery stress in SMP contributes to the finger's shape restoration. Since each joint's rotation can be individually controlled, the position control of the finger is made possible. Experimental analysis has been conducted to show the finger's variable stiffness and the result is compared with the analytical values. It is found that the stiffness ratio can be 24.9 times for a joint at room temperature (20°C) and at an elevated temperature of 60°C when air pressure p of the soft actuator is turned off. Finally, a gripper composed of two fingers is fabricated for demonstration.

Gait training reduces ankle joint stiffness and facilitates heel strike in children with Cerebral Palsy.

PubMed

Willerslev-Olsen, Maria; Lorentzen, Jakob; Nielsen, Jens Bo

2014-01-01

Foot drop and toe walking are frequent concerns in children with cerebral palsy (CP). Increased stiffness of the ankle joint muscles may contribute to these problems. Does four weeks of daily home based treadmill training with incline reduce ankle joint stiffness and facilitate heel strike in children with CP? Seventeen children with CP (4-14 years) were recruited. Muscle stiffness and gait ability were measured twice before and twice after training with an interval of one month. Passive and reflex-mediated stiffness were measured by a dynamometer which applied stretches below and above reflex threshold. Gait kinematics were recorded by 3-D video-analysis during treadmill walking. Foot pressure was measured by force-sensitive foot soles during treadmill and over-ground walking. Children with increased passive stiffness showed a significant reduction in stiffness following training (P = 0.01). Toe lift in the swing phase (P = 0.014) and heel impact (P = 0.003) increased significantly following the training during both treadmill and over-ground walking. Daily intensive gait training may influence the elastic properties of ankle joint muscles and facilitate toe lift and heel strike in children with CP. Intensive gait training may be beneficial in preventing contractures and maintain gait ability in children with CP.

A quasi-linear control theory analysis of timesharing skills

NASA Technical Reports Server (NTRS)

Agarwal, G. C.; Gottlieb, G. L.

1977-01-01

The compliance of the human ankle joint is measured by applying 0 to 50 Hz band-limited gaussian random torques to the foot of a seated human subject. These torques rotate the foot in a plantar-dorsal direction about a horizontal axis at a medial moleolus of the ankle. The applied torques and the resulting angular rotation of the foot are measured, digitized and recorded for off-line processing. Using such a best-fit, second-order model, the effective moment of inertia of the ankle joint, the angular viscosity and the stiffness are calculated. The ankle joint stiffness is shown to be a linear function of the level of tonic muscle contraction, increasing at a rate of 20 to 40 Nm/rad/Kg.m. of active torque. In terms of the muscle physiology, the more muscle fibers that are active, the greater the muscle stiffness. Joint viscosity also increases with activation. Joint stiffness is also a linear function of the joint angle, increasing at a rate of about 0.7 to 1.1 Nm/rad/deg from plantar flexion to dorsiflexion rotation.

The differential effects of gender, anthropometry, and prior hormonal state on frontal plane knee joint stiffness

PubMed Central

Cammarata, Martha L.; Dhaher, Yasin Y.

2012-01-01

Background Gender differences in passive frontal plane knee stiffness may contribute to the increased anterior cruciate ligament injury rate in females. Gender-based stiffness differences have been attributed to anthropometric variations, but little data exist describing this relationship. Furthermore, sex hormone levels appear to influence joint stiffness, but the differential effects of instantaneous and prior hormonal concentrations remain unknown. This study sought to explore the effect of gender, prior hormonal status, and anthropometry on passive frontal plane knee joint stiffness. Methods Twelve males and 31 females participated. Females were grouped by hormonal contraceptive use (non users [n=11], monophasic contraceptive users [n=11], and triphasic contraceptive users [n=9]) and tested at the same point in the menstrual cycle. Subjects’ right knee was passively stretched ±7° in the frontal plane at 3°/s. Stiffness was estimated at three loading levels and normalized by body size to minimize anthropometric biases. A 4 (group) × 3 (load) repeated measures analysis of variance was performed for both raw and normalized stiffness. Linear regression analyses were preformed between stiffness estimates and knee diameter and quadriceps femoris angle. Findings Males displayed significantly greater (P<0.05) frontal plane stiffness than females. When normalized, males displayed significantly greater stiffness in valgus (P<0.05), but not varus (P>0.05) than females. No significant effect (P>0.05) of prior hormonal state was found; however, when normalized, varus stiffness was significantly less for triphasic contraceptive users than the other female groups (P<0.05). Quadriceps femoris angle was negatively correlated and knee diameter was positively correlated to knee stiffness. Interpretation Consistent with earlier in vitro findings, our data may indicate that ligament material properties are gender specific. A deficit in passive knee joint stiffness may place a larger burden on the neuromuscular system to resist frontal plane loading in females. PMID:18479791

Arch structure is associated with unique joint work, relative joint contributions and stiffness during landing.

PubMed

Powell, Douglas W; Queen, Robin M; Williams, D S Blaise

2016-10-01

To examine lower extremity joint contributions to a landing task in high-(HA) and low-arched (LA) female athletes by quantifying vertical stiffness, joint work and relative joint contributions to landing. Twenty healthy female recreational athletes (10 HA and 10 LA) performed five barefoot drop landings from a height of 30cm. Three-dimensional kinematics (240Hz) and ground reaction forces (960Hz) were recorded simultaneously. Vertical stiffness, joint work values and relative joint work values were calculated using Visual 3D and MatLab. HA athletes had significantly greater vertical stiffness compared to LA athletes (p=0.013). Though no differences in ankle joint work were observed (p=0.252), HA athletes had smaller magnitudes of knee (p=0.046), hip (p=0.019) and total lower extremity joint work values (p=0.016) compared to LA athletes. HA athletes had greater relative contributions of the ankle (p=0.032) and smaller relative contributions of the hip (p=0.049) compared to LA athletes. No differences in relative contributions of the knee were observed (p=0.255). These findings demonstrate that aberrant foot structure is associated with unique contributions of lower extremity joints to load attenuation during landing. These data may provide insight into the unique injury mechanisms associated with arch height in female athletes. Copyright © 2016 Elsevier B.V. All rights reserved.

Inspiration from nature: dynamic modelling of the musculoskeletal structure of the seahorse tail.

PubMed

Praet, Tomas; Adriaens, Dominique; Van Cauter, Sofie; Masschaele, Bert; De Beule, Matthieu; Verhegghe, Benedict

2012-10-01

Technological advances are often inspired by nature, considering that engineering is frequently faced by the same challenges as organisms in nature. One such interesting challenge is creating a structure that is at the same time stiff in a certain direction, yet flexible in another. The seahorse tail combines both radial stiffness and bending flexibility in a particularly elegant way: even though the tail is covered in a protective armour, it still shows sufficient flexibility to fully function as a prehensile organ. We therefore study the complex mechanics and dynamics of the musculoskeletal system of the seahorse tail from an engineering point of view. The seahorse tail derives its combination of flexibility and resilience from a chain of articulating skeletal segments. A versatile dynamic model of those segments was constructed, on the basis of automatic recognition of joint positions and muscle attachments. Both muscle structures that are thought to be responsible for ventral and ventral-lateral tail bending, namely the median ventral muscles and the hypaxial myomere muscles, were included in the model. Simulations on the model consist mainly of dynamic multi-body simulations. The results show that the sequential structure of uniformly shaped bony segments can remain flexible because of gliding joints that connect the corners of the segments. Radial stiffness on the other hand is obtained through the support that the central vertebra provides to the tail plating. Such insights could help in designing biomedical instruments that specifically require both high bending flexibility and radial stiffness (e.g. flexible stents and steerable catheters). Copyright © 2012 John Wiley & Sons, Ltd.

Mechanical loading regulates human MSC differentiation in a multi-layer hydrogel for osteochondral tissue engineering.

PubMed

Steinmetz, Neven J; Aisenbrey, Elizabeth A; Westbrook, Kristofer K; Qi, H Jerry; Bryant, Stephanie J

2015-07-01

A bioinspired multi-layer hydrogel was developed for the encapsulation of human mesenchymal stem cells (hMSCs) as a platform for osteochondral tissue engineering. The spatial presentation of biochemical cues, via incorporation of extracellular matrix analogs, and mechanical cues, via both hydrogel crosslink density and externally applied mechanical loads, were characterized in each layer. A simple sequential photopolymerization method was employed to form stable poly(ethylene glycol)-based hydrogels with a soft cartilage-like layer of chondroitin sulfate and low RGD concentrations, a stiff bone-like layer with high RGD concentrations, and an intermediate interfacial layer. Under a compressive load, the variation in hydrogel stiffness within each layer produced high strains in the soft cartilage-like layer, low strains in the stiff bone-like layer, and moderate strains in the interfacial layer. When hMSC-laden hydrogels were cultured statically in osteochondral differentiation media, the local biochemical and matrix stiffness cues were not sufficient to spatially guide hMSC differentiation after 21 days. However dynamic mechanical stimulation led to differentially high expression of collagens with collagen II in the cartilage-like layer, collagen X in the interfacial layer and collagen I in the bone-like layer and mineral deposits localized to the bone layer. Overall, these findings point to external mechanical stimulation as a potent regulator of hMSC differentiation toward osteochondral cellular phenotypes. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The effect of ankle-foot orthosis plantarflexion stiffness on ankle and knee joint kinematics and kinetics during first and second rockers of gait in individuals with stroke

PubMed Central

Singer, Madeline L.; Kobayashi, Toshiki; Lincoln, Lucas S.; Orendurff, Michael S.; Foreman, K. Bo

2014-01-01

Background Stiffness of an ankle-foot orthosis plays an important role in improving gait in patients with a history of stroke. To address this, the aim of this case series study was to determine the effect of increasing plantarflexion stiffness of an ankle-foot orthosis on the sagittal ankle and knee joint angle and moment during the first and second rockers of gait. Methods Gait data were collected in 5 subjects with stroke at a self-selected walking speed under two plantarflexion stiffness conditions (0.4 Nm/deg and 1.3 Nm/deg) using a stiffness-adjustable experimental ankle-foot orthosis on a Bertec split-belt fully instrumented treadmill in a 3-dimensional motion analysis laboratory. Findings By increasing the plantarflexion stiffness of the ankle-foot orthosis, peak plantarfexion angle of the ankle was reduced and peak dorsiflexion moment was generally increased in the first rocker as hypothesized. Two subjects demonstrated increases in both peak knee flexion angle and peak knee extension moment in the second rocker as hypothesized. The two subjects exhibited minimum contractility during active plantarflexion, while the other three subjects could actively plantarflex their ankle joint. Interpretation It was suggested that those with the decreased ability to actively plantarflex their ankle could not overcome excessive plantarflexion stiffness at initial contact of gait, and as a result exhibited compensation strategies at the knee joint. Providing excessively stiff ankle-foot orthoses might put added stress on the extensor muscles of the knee joint, potentially creating fatigue and future pathologies in some patients with stroke. PMID:25241248

Optimal compliant-surface jumping: a multi-segment model of springboard standing jumps.

PubMed

Cheng, Kuangyou B; Hubbard, Mont

2005-09-01

A multi-segment model is used to investigate optimal compliant-surface jumping strategies and is applied to springboard standing jumps. The human model has four segments representing the feet, shanks, thighs, and trunk-head-arms. A rigid bar with a rotational spring on one end and a point mass on the other end (the tip) models the springboard. Board tip mass, length, and stiffness are functions of the fulcrum setting. Body segments and board tip are connected by frictionless hinge joints and are driven by joint torque actuators at the ankle, knee, and hip. One constant (maximum isometric torque) and three variable functions (of instantaneous joint angle, angular velocity, and activation level) determine each joint torque. Movement from a nearly straight motionless initial posture to jump takeoff is simulated. The objective is to find joint torque activation patterns during board contact so that jump height can be maximized. Minimum and maximum joint angles, rates of change of normalized activation levels, and contact duration are constrained. Optimal springboard jumping simulations can reasonably predict jumper vertical velocity and jump height. Qualitatively similar joint torque activation patterns are found over different fulcrum settings. Different from rigid-surface jumping where maximal activation is maintained until takeoff, joint activation decreases near takeoff in compliant-surface jumping. The fulcrum-height relations in experimental data were predicted by the models. However, lack of practice at non-preferred fulcrum settings might have caused less jump height than the models' prediction. Larger fulcrum numbers are beneficial for taller/heavier jumpers because they need more time to extend joints.

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses.

PubMed

Kim, Ji-Won; Chong, Song-Hun; Cho, Gye-Chun

2018-03-29

Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10 -5 ) and mid-strain (10 -5 to 10 -3 ) ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1) grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2) the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3) the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4) increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass.

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses

PubMed Central

Cho, Gye-Chun

2018-01-01

Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10−5) and mid-strain (10−5 to 10−3) ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1) grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2) the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3) the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4) increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass. PMID:29596371

Neuromuscular properties of different spastic human joints vary systematically.

PubMed

Mirbagheri, M M; Settle, K

2010-01-01

We quantified the mechanical abnormalities of the spastic wrist in chronic stroke survivors, and determined whether these findings were representative of those recorded at the elbow and ankle joints. System identification techniques were used to characterize the mechanical abnormalities of these joints and to identify the contribution of intrinsic and reflex stiffness to these abnormalities. Modulation of intrinsic and reflex stiffness with the joint angle was studied by applying PRBS perturbations to the joints at different joint angles over the range of motion. Age-matched healthy subjects were used as control.

Improving stability and curving passing performance for railway vehicles with a variable stiffness MRF rubber joint

NASA Astrophysics Data System (ADS)

Harris, B. J.; Sun, S. S.; Li, W. H.

2017-03-01

With the growing need for effective intercity transport, the need for more advanced rail vehicle technology has never been greater. The conflicting primary longitudinal suspension requirements of high speed stability and curving performance limit the development of rail vehicle technology. This paper presents a novel magnetorheological fluid based joint with variable stiffness characteristics for the purpose of overcoming this parameter conflict. Firstly, the joint design and working principle is developed. Following this, a prototype is tested by MTS to characterize its variable stiffness properties under a range of conditions. Lastly, the performance of the proposed MRF rubber joint with regard to improving train stability and curving performance is numerically evaluated.

Kinetic Compensations due to Chronic Ankle Instability during Landing and Jumping.

PubMed

Kim, Hyunsoo; Son, S Jun; Seeley, Matthew K; Hopkins, J Ty

2018-02-01

Skeletal muscles absorb and transfer kinetic energy during landing and jumping, which are common requirements of various forms of physical activity. Chronic ankle instability (CAI) is associated with impaired neuromuscular control and dynamic stability of the lower extremity. Little is known regarding an intralimb, lower-extremity joint coordination of kinetics during landing and jumping for CAI patients. We investigated the effect of CAI on lower-extremity joint stiffness and kinetic and energetic patterns across the ground contact phase of landing and jumping. One hundred CAI patients and 100 matched able-bodied controls performed five trials of a landing and jumping task (a maximal vertical forward jump, landing on a force plate with the test leg only, and immediate lateral jump toward the contralateral side). Functional analyses of variance and independent t-tests were used to evaluate between-group differences for lower-extremity net internal joint moment, power, and stiffness throughout the entire ground contact phase of landing and jumping. Relative to the control group, the CAI group revealed (i) reduced plantarflexion and knee extension and increased hip extension moments; (ii) reduced ankle and knee eccentric and concentric power, and increased hip eccentric and concentric power, and (iii) reduced ankle and knee joint stiffness and increased hip joint stiffness during the task. CAI patients seemed to use a hip-dominant strategy by increasing the hip extension moment, stiffness, and eccentric and concentric power during landing and jumping. This apparent compensation may be due to decreased capabilities to produce sufficient joint moment, stiffness, and power at the ankle and knee. These differences might have injury risk and performance implications.

Virtual trajectories, joint stiffness, and changes in the limb natural frequency during single-joint oscillatory movements.

PubMed

Latash, M L

1992-07-01

In the framework of the equilibrium-point hypothesis, virtual trajectories and patterns of joint stiffness were reconstructed during voluntary single-joint oscillatory movements in the elbow joint at a variety of frequencies and against two inertial loads. At low frequencies, virtual trajectories were in-phase with the actual joint trajectories. Joint stiffness changed at a doubled frequency. An increase in movement frequency and/or inertial load led to an increase in the difference between the peaks of the actual and virtual trajectories and in both peak and averaged values of joint stiffness. At a certain, critical frequency, virtual trajectory was nearly flat. Further increase in movement frequency led to a 180 degree phase shift between the actual and virtual trajectories. The assessed values of the natural frequency of the system "limb + manipulandum" were close to the critical frequencies for both low and high inertial loads. Peak levels and integrals of the electromyograms of two flexor and two extensor muscles changed monotonically with movement frequency without any special behavior at the critical frequencies. Nearly flat virtual trajectories at the natural frequency make physical sense as hypothetical control signals, unlike the electromyographic recordings, since a system at its natural frequency requires minimal central interference. Modulation of joint stiffness is assumed to be an important adaptive mechanism attenuating difference between the system's natural frequency and desired movement frequency. Virtual trajectory is considered a behavioral observable. Phase transitions between the virtual and actual trajectories are illustrations of behavioral discontinuities introduced by slow changes in a higher level control parameter, movement frequency. Relative phase shift between these two trajectories may be considered an order parameter.

Behavior of Fiber Glass Bolts, Rock Bolts and Cable Bolts in Shear

NASA Astrophysics Data System (ADS)

Li, Xuwei; Aziz, Naj; Mirzaghorbanali, Ali; Nemcik, Jan

2016-07-01

This paper experimentally compares the shear behavior of fiber glass (FG) bolt, rock bolt (steel rebar bolt) and cable bolt for the bolt contribution to bolted concrete surface shear strength, and bolt failure mode. Two double shear apparatuses of different size were used for the study. The tensile strength, the shear strength and the deformation modulus of bolt control the shear behavior of a sheared bolted joint. Since the strength and deformation modulus of FG bolt, rock bolt and cable bolt obtained from uniaxial tensile tests are different, their shear behavior in reinforcing joints is accordingly different. Test results showed that the shear stiffness of FG bolted joints decreased gradually from the beginning to end, while the shear stiffness of joints reinforced by rock bolt and cable bolt decreased bi-linearly, which is clearly consistent with their tensile deformation modulus. The bolted joint shear stiffness was highly influenced by bolt pretension in the high stiffness stage for both rock bolt and cable bolt, but not in the low stiffness stage. The rock bolt contribution to joint shear strength standardised by the bolt tensile strength was the largest, followed by cable bolts, then FG bolts. Both the rock bolts and cable bolts tended to fail in tension, while FG bolts in shear due to their low shear strength and constant deformation modulus.

An analytical investigation of a conceptual design for the station transverse boom rotary joint structure

NASA Technical Reports Server (NTRS)

Lake, M. S.; Bush, H. G.

1986-01-01

A study was conducted to define an annular ring, discrete roller assembly concept for the space station transverse boom rotary joint. The concept was analyzed using closed-form and finite element techniques, to size structural members for a range of joint diameters and to determine necessary equivalent stiffnesses for the roller assemblies. Also, a mass study of the system was conducted to determine its practicality, and maximum loads in the joint were identified. To obtain the optimum balance between high stiffness and low structural mass in the design of the rotary joint, it is necessary to maximize the diameter of the annular ring within operational constraints (i.e., shuttle cargo bay size). Further, a rotary joint designed with the largest possible ring diameter will result in minimum operational loads in both the roller assemblies and the transition truss members while also allowing minimum design stiffnesses for the roller assemblies.

A Modelling Method of Bolt Joints Based on Basic Characteristic Parameters of Joint Surfaces

NASA Astrophysics Data System (ADS)

Yuansheng, Li; Guangpeng, Zhang; Zhen, Zhang; Ping, Wang

2018-02-01

Bolt joints are common in machine tools and have a direct impact on the overall performance of the tools. Therefore, the understanding of bolt joint characteristics is essential for improving machine design and assembly. Firstly, According to the experimental data obtained from the experiment, the stiffness curve formula was fitted. Secondly, a finite element model of unit bolt joints such as bolt flange joints, bolt head joints, and thread joints was constructed, and lastly the stiffness parameters of joint surfaces were implemented in the model by the secondary development of ABAQUS. The finite element model of the bolt joint established by this method can simulate the contact state very well.

Investigating the use of multi-point coupling for single-sensor bearing estimation in one direction

NASA Astrophysics Data System (ADS)

Woolard, Americo G.; Phoenix, Austin A.; Tarazaga, Pablo A.

2018-04-01

Bearing estimation of radially propagating symmetric waves in solid structures typically requires a minimum of two sensors. As a test specimen, this research investigates the use of multi-point coupling to provide directional inference using a single-sensor. By this provision, the number of sensors required for localization can be reduced. A finite-element model of a beam is constructed with a symmetrically placed bipod that has asymmetric joint-stiffness properties. Impulse loading is applied at different points along the beam, and measurements are taken from the apex of the bipod. A technique is developed to determine the direction-of-arrival of the propagating wave. The accuracy when using the bipod with the developed technique is compared against results gathered without the bipod and measuring from an asymmetric location along the beam. The results show 92% accuracy when the bipod is used, compared to 75% when measuring without the bipod from an asymmetric location. A geometry investigation finds the best accuracy results when one leg of the bipod has a low stiffness and a large diameter relative to the other leg.

Biomimetic-inspired joining of composite with metal structures: A survey of natural joints and application to single lap joints

NASA Astrophysics Data System (ADS)

Avgoulas, Evangelos Ioannis; Sutcliffe, Michael P. F.

2014-03-01

Joining composites with metal parts leads, inevitably, to high stress concentrations because of the material property mismatch. Since joining composite to metal is required in many high performance structures, there is a need to develop a new multifunctional approach to meet this challenge. This paper uses the biomimetics approach to help develop solutions to this problem. Nature has found many ingenious ways of joining dissimilar materials and making robust attachments, alleviating potential stress concentrations. A literature survey of natural joint systems has been carried out, identifying and analysing different natural joint methods from a mechanical perspective. A taxonomy table was developed based on the different methods/functions that nature successfully uses to attach dissimilar tissues (materials). This table is used to understand common themes or approaches used in nature for different joint configurations and functionalities. One of the key characteristics that nature uses to joint dissimilar materials is a transitional zone of stiffness in the insertion site. Several biomimetic-inspired metal-to-composite (steel-to-CFRP), adhesively bonded, Single Lap Joints (SLJs) were numerically investigated using a finite element analysis. The proposed solutions offer a transitional zone of stiffness of one joint part to reduce the material stiffness mismatch at the joint. An optimisation procedure was used to identify the variation in material stiffness which minimises potential failure of the joint. It was found that the proposed biomimetic SLJs reduce the asymmetry of the stress distribution along the adhesive area.

Multi-fingered haptic palpation utilizing granular jamming stiffness feedback actuators

NASA Astrophysics Data System (ADS)

Li, Min; Ranzani, Tommaso; Sareh, Sina; Seneviratne, Lakmal D.; Dasgupta, Prokar; Wurdemann, Helge A.; Althoefer, Kaspar

2014-09-01

This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators for simulating tissue palpation procedures in traditional and in robot-assisted minimally invasive surgery. Soft tissue stiffness is simulated by changing the stiffness property of the actuator during palpation. For the first time, granular jamming and pneumatic air actuation are combined to realize stiffness modulation. The stiffness feedback actuator is validated by stiffness measurements in indentation tests and through stiffness discrimination based on a user study. According to the indentation test results, the introduction of a pneumatic chamber to granular jamming can amplify the stiffness variation range and reduce hysteresis of the actuator. The advantage of multi-fingered palpation using the proposed actuators is proven by the comparison of the results of the stiffness discrimination performance using two-fingered (sensitivity: 82.2%, specificity: 88.9%, positive predicative value: 80.0%, accuracy: 85.4%, time: 4.84 s) and single-fingered (sensitivity: 76.4%, specificity: 85.7%, positive predicative value: 75.3%, accuracy: 81.8%, time: 7.48 s) stiffness feedback.

Differentiation between non-neural and neural contributors to ankle joint stiffness in cerebral palsy

PubMed Central

2013-01-01

Background Spastic paresis in cerebral palsy (CP) is characterized by increased joint stiffness that may be of neural origin, i.e. improper muscle activation caused by e.g. hyperreflexia or non-neural origin, i.e. altered tissue viscoelastic properties (clinically: “spasticity” vs. “contracture”). Differentiation between these components is hard to achieve by common manual tests. We applied an assessment instrument to obtain quantitative measures of neural and non-neural contributions to ankle joint stiffness in CP. Methods Twenty-three adolescents with CP and eleven healthy subjects were seated with their foot fixated to an electrically powered single axis footplate. Passive ramp-and-hold rotations were applied over full ankle range of motion (RoM) at low and high velocities. Subject specific tissue stiffness, viscosity and reflexive torque were estimated from ankle angle, torque and triceps surae EMG activity using a neuromuscular model. Results In CP, triceps surae reflexive torque was on average 5.7 times larger (p = .002) and tissue stiffness 2.1 times larger (p = .018) compared to controls. High tissue stiffness was associated with reduced RoM (p < .001). Ratio between neural and non-neural contributors varied substantially within adolescents with CP. Significant associations of SPAT (spasticity test) score with both tissue stiffness and reflexive torque show agreement with clinical phenotype. Conclusions Using an instrumented and model based approach, increased joint stiffness in CP could be mainly attributed to higher reflexive torque compared to control subjects. Ratios between contributors varied substantially within adolescents with CP. Quantitative differentiation of neural and non-neural stiffness contributors in CP allows for assessment of individual patient characteristics and tailoring of therapy. PMID:23880287

Differentiation between non-neural and neural contributors to ankle joint stiffness in cerebral palsy.

PubMed

de Gooijer-van de Groep, Karin L; de Vlugt, Erwin; de Groot, Jurriaan H; van der Heijden-Maessen, Hélène C M; Wielheesen, Dennis H M; van Wijlen-Hempel, Rietje M S; Arendzen, J Hans; Meskers, Carel G M

2013-07-23

Spastic paresis in cerebral palsy (CP) is characterized by increased joint stiffness that may be of neural origin, i.e. improper muscle activation caused by e.g. hyperreflexia or non-neural origin, i.e. altered tissue viscoelastic properties (clinically: "spasticity" vs. "contracture"). Differentiation between these components is hard to achieve by common manual tests. We applied an assessment instrument to obtain quantitative measures of neural and non-neural contributions to ankle joint stiffness in CP. Twenty-three adolescents with CP and eleven healthy subjects were seated with their foot fixated to an electrically powered single axis footplate. Passive ramp-and-hold rotations were applied over full ankle range of motion (RoM) at low and high velocities. Subject specific tissue stiffness, viscosity and reflexive torque were estimated from ankle angle, torque and triceps surae EMG activity using a neuromuscular model. In CP, triceps surae reflexive torque was on average 5.7 times larger (p = .002) and tissue stiffness 2.1 times larger (p = .018) compared to controls. High tissue stiffness was associated with reduced RoM (p < .001). Ratio between neural and non-neural contributors varied substantially within adolescents with CP. Significant associations of SPAT (spasticity test) score with both tissue stiffness and reflexive torque show agreement with clinical phenotype. Using an instrumented and model based approach, increased joint stiffness in CP could be mainly attributed to higher reflexive torque compared to control subjects. Ratios between contributors varied substantially within adolescents with CP. Quantitative differentiation of neural and non-neural stiffness contributors in CP allows for assessment of individual patient characteristics and tailoring of therapy.

Linear Parameter Varying Identification of Dynamic Joint Stiffness during Time-Varying Voluntary Contractions

PubMed Central

Golkar, Mahsa A.; Sobhani Tehrani, Ehsan; Kearney, Robert E.

2017-01-01

Dynamic joint stiffness is a dynamic, nonlinear relationship between the position of a joint and the torque acting about it, which can be used to describe the biomechanics of the joint and associated limb(s). This paper models and quantifies changes in ankle dynamic stiffness and its individual elements, intrinsic and reflex stiffness, in healthy human subjects during isometric, time-varying (TV) contractions of the ankle plantarflexor muscles. A subspace, linear parameter varying, parallel-cascade (LPV-PC) algorithm was used to identify the model from measured input position perturbations and output torque data using voluntary torque as the LPV scheduling variable (SV). Monte-Carlo simulations demonstrated that the algorithm is accurate, precise, and robust to colored measurement noise. The algorithm was then used to examine stiffness changes associated with TV isometric contractions. The SV was estimated from the Soleus EMG using a Hammerstein model of EMG-torque dynamics identified from unperturbed trials. The LPV-PC algorithm identified (i) a non-parametric LPV impulse response function (LPV IRF) for intrinsic stiffness and (ii) a LPV-Hammerstein model for reflex stiffness consisting of a LPV static nonlinearity followed by a time-invariant state-space model of reflex dynamics. The results demonstrated that: (a) intrinsic stiffness, in particular ankle elasticity, increased significantly and monotonically with activation level; (b) the gain of the reflex pathway increased from rest to around 10–20% of subject's MVC and then declined; and (c) the reflex dynamics were second order. These findings suggest that in healthy human ankle, reflex stiffness contributes most at low muscle contraction levels, whereas, intrinsic contributions monotonically increase with activation level. PMID:28579954

Development of a finite element/multi-body model of a newborn infant for restraint analysis and design.

PubMed

Bondy, Matthew; Altenhof, William; Chen, Xilin; Snowdon, Anne; Vrkljan, Brenda

2014-01-01

A finite element/multi-body model of a newborn infant has been developed by researchers at the University of Windsor. The geometry of this model is derived from a Nita newborn hospital training mannequin. It consists of 17 parts: eight upper and lower limb segments, the torso, head, and a seven-segment neck with seven translational and eight rotational joints. Anthropometry is consistent with hospital growth charts, measurements requested from health professionals and data from the open literature. The biomechanical properties of the model (i.e. joint stiffnesses) are implementations of data identified in the open literature. The model has been validated with respect to studies of the biomechanics of shaken baby syndrome, infant falls and the Q0 anthropomorphic testing device. A significant conclusion of this study is that the kinetics of the Q0 neck is not biofidelic. This model is currently used in an analysis of airway patency for infants in modern automotive child restraints.

Objective Assessment of Joint Stiffness: A Clinically Oriented Hardware and Software Device with an Application to the Shoulder Joint.

PubMed

McQuade, Kevin; Price, Robert; Liu, Nelson; Ciol, Marcia A

2012-08-30

Examination of articular joints is largely based on subjective assessment of the "end-feel" of the joint in response to manually applied forces at different joint orientations. This technical report aims to describe the development of an objective method to examine joints in general, with specific application to the shoulder, and suitable for clinical use. We adapted existing hardware and developed laptop-based software to objectively record the force/displacement behavior of the glenohumeral joint during three common manual joint examination tests with the arm in six positions. An electromagnetic tracking system recorded three-dimensional positions of sensors attached to a clinician examiner and a patient. A hand-held force transducer recorded manually applied translational forces. The force and joint displacement were time-synchronized and the joint stiffness was calculated as a quantitative representation of the joint "end-feel." A methodology and specific system checks were developed to enhance clinical testing reproducibility and precision. The device and testing protocol were tested on 31 subjects (15 with healthy shoulders, and 16 with a variety of shoulder impairments). Results describe the stiffness responses, and demonstrate the feasibility of using the device and methods in clinical settings.

Estimation of Quasi-Stiffness of the Human Knee in the Stance Phase of Walking

PubMed Central

Shamaei, Kamran; Sawicki, Gregory S.; Dollar, Aaron M.

2013-01-01

Biomechanical data characterizing the quasi-stiffness of lower-limb joints during human locomotion is limited. Understanding joint stiffness is critical for evaluating gait function and designing devices such as prostheses and orthoses intended to emulate biological properties of human legs. The knee joint moment-angle relationship is approximately linear in the flexion and extension stages of stance, exhibiting nearly constant stiffnesses, known as the quasi-stiffnesses of each stage. Using a generalized inverse dynamics analysis approach, we identify the key independent variables needed to predict knee quasi-stiffness during walking, including gait speed, knee excursion, and subject height and weight. Then, based on the identified key variables, we used experimental walking data for 136 conditions (speeds of 0.75–2.63 m/s) across 14 subjects to obtain best fit linear regressions for a set of general models, which were further simplified for the optimal gait speed. We found R2 > 86% for the most general models of knee quasi-stiffnesses for the flexion and extension stages of stance. With only subject height and weight, we could predict knee quasi-stiffness for preferred walking speed with average error of 9% with only one outlier. These results provide a useful framework and foundation for selecting subject-specific stiffness for prosthetic and exoskeletal devices designed to emulate biological knee function during walking. PMID:23533662

Astym® Therapy for the Management of Recalcitrant Knee Joint Stiffness after Total Knee Arthroplasty.

PubMed

Bhave, Anil; Corcoran, James; Cherian, Jeffery J; Mont, Michael A

2016-01-01

Knee stiffness is a common complication after total knee arthroplasty (TKA). Despite studies published on the surgical management of reduced range of motion (ROM) after TKA, there is limited evidence on the nonoperative management of joint and soft tissue imbalances possibly contributing to reduced knee ROM. This report assesses changes in ROM, pain, function, and patellar tendon length after Astym® joint mobilization use. A 38-year-old male professional skier had a right TKA 3 months before presentation with 2 subsequent manipulations under anesthesia secondary to persistent knee stiffness. He had patellar baja on radiograph, a reduced arc of ROM, reduced patellar mobility and muscular extensibility, and pain to palpation along the patellar tendon. He had 12 visits of physical therapy with the use of Astym®, patellar mobilization, and tibio-femoral mobilizations with movement. The patient also used a customized knee device at home for prolonged knee extension stretching. The patient was treated for 12 visits, along with home use of customized bracing for knee extension. Significant improvements were seen in pain, function, and ROM. He returned to work full-time, ambulated prolonged distances, and negotiated stairs pain-free. He also demonstrated resolution of patellar baja radiographically. Conservative management of recalcitrant knee joint stiffness after primary TKA can be effective in restoring knee mobility and reducing pain and activity limitation. A multimodal approach using Astym® treatment, customized knee bracing, and targeted joint mobilization can be effective in resolving knee joint stiffness.

Lower Body Stiffness and Muscle Activity Differences Between Female Dancers and Basketball Players During Drop Jumps

PubMed Central

Ambegaonkar, Jatin P.; Shultz, Sandra J.; Perrin, David H.; Schmitz, Randy J.; Ackerman, Terry A.; Schulz, Mark R.

2011-01-01

Background: Anterior cruciate ligament (ACL) injuries often occur during landing, with female athletes at higher injury risk than male athletes. Interestingly, female dancers have lower ACL injury rates than do female athletes in general. Hypothesis: Female dancers will have earlier and greater lower extremity muscle activity and higher sagittal knee joint and leg stiffness than will female basketball players. Study Design: Cross-sectional group comparison. Methods: Fifty-five healthy female athletes (35 dancers, 20 basketball players) performed 5 double-leg drop jumps from a 45-cm box. Surface electromyography (onsets and amplitudes; prelanding and postlanding) was recorded from the lateral gastrocnemius, medial and lateral hamstrings, lateral quadriceps muscles with a 3-dimensional electromagnetic tracking system, and forceplates recording biomechanics (leg spring stiffness and knee joint stiffness). Results: Compared with basketball players, dancers had greater leg spring stiffness (P = 0.047) but similar knee joint stiffness (P = 0.44). Although no significant differences were observed in overall muscle onset times (P = 0.22) or activation amplitudes (prelanding, P = 0.60; postlanding, P = 0.78), small to moderate effect sizes (ESs) suggest trends in dancers toward earlier (ES = 0.53) and higher medial hamstrings activation pre- (ES = 0.55) and post- (ES = 0.41) landing and lower lateral quadriceps (ES = 0.30) and higher gastrocnemius (ES = 0.33) postlanding muscle activation. Conclusions: In dancers, the higher leg spring stiffness and trends toward higher hamstrings prelanding and postlanding, as well as lower quadriceps and higher gastrocnemius activation postlanding with similar knee joint stiffness, indicate lower extremity neuromechanical differences across other joints. Clinical Relevance: Female dancers may have lower extremity neuromechanics that are different from those of basketball players during drop jumps. If dancers use ACL-protective strategies during activity, then their training routines should be further investigated to improve ACL injury prevention programs. PMID:23015996

Application of traction drives as servo mechanisms

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Rohn, D. A.; Steinetz, B. M.

1985-01-01

The suitability of traction drives for a wide class of aerospace control mechanisms is examined. Potential applications include antenna or solar array drive positioners, robotic joints, control moment gyro (CMG) actuators and propeller pitch change mechanisms. In these and similar applications the zero backlash, high torsional stiffness, low hysteresis and torque ripple characteristics of traction drives are of particular interest, as is the ability to run without liquid lubrication in certain cases. Wear and fatigue considerations for wet and dry operation are examined along with the tribological performance of several promising self lubricating polymers for traction contracts. The speed regulation capabilities of variable ratio traction drives are reviewed. A torsional stiffness analysis described suggests that traction contacts are relatively stiff compared to gears and are significantly stiffer than the other structural elements in the prototype CMG traction drive analyzed. Discussion is also given of an advanced turboprop propeller pitch change mechanism that incorporates a traction drive.

Assessment of passive knee stiffness and viscosity in individuals with spinal cord injury using pendulum test.

PubMed

Joghtaei, Mahmoud; Arab, Amir Massoud; Hashemi-Nasl, Hamed; Joghataei, Mohammad Taghi; Tokhi, Mohammad Osman

2015-03-01

Stiffness and viscosity represent passive resistances to joint motion related with the structural properties of the joint tissue and of the musculotendinous complex. Both parameters can be affected in patients with spinal cord injury (SCI). The purpose of this study was to measure passive knee stiffness and viscosity in patients with SCI with paraplegia and healthy subjects using Wartenberg pendulum test. Non-experimental, cross-sectional, case-control design. An outpatient physical therapy clinic, University of social welfare and Rehabilitation Science, Iran. A sample of convenience sample of 30 subjects participated in the study. Subjects were categorized into two groups: individuals with paraplegic SCI (n = 15, age: 34.60 ± 9.18 years) and 15 able-bodied individuals as control group (n = 15, age: 30.66 ± 11.13 years). Not applicable. Passive pendulum test of Wartenberg was used to measure passive viscous-elastic parameters of the knee (stiffness, viscosity) in all subjects. Statistical analysis (independent t-test) revealed significant difference in the joint stiffness between healthy subjects and those with paraplegic SCI (P = 0.01). However, no significant difference was found in the viscosity between two groups (P = 0.17). Except for first peak flexion angle, all other displacement kinematic parameters exhibited no statistically significant difference between normal subjects and subjects with SCI. Patients with SCI have significantly greater joint stiffness compared to able-bodied subjects.

Integrated, proportionally controlled, and naturally compliant universal joint actuator with controllable stiffness

DOEpatents

Borenstein, Johann; Granosik, Grzegorz

2005-03-22

An apparatus for traversing obstacles having an elongated, round, flexible body that includes a plurality of segments interconnected by an integrated joint actuator assembly. The integrated joint actuator assembly includes a plurality of bellows-type actuators individually coupling adjacent segments to permit pivotal actuation of the apparatus therebetween. A controller is employed to maintain proper positional control and stiffness control while minimize air flow.

Knee stiffness and viscosity: New implementation and perspectives in prosthesis development

PubMed Central

Bohinc, Klemen; Vantur, Nejc; Torkar, Drago; Lampe, Tomaž; Hribernik, Marija; Jakovljević, Miroljub

2017-01-01

The pendulum test is a method applied to measure passive resistance of the knee. A new and simple pendulum test with instrumentation based on infrared camera was used to evaluate knee stiffness and viscosity on a female human cadaver. The stiffness and viscosity were calculated based on the kinetic data. During the measurements, the periarticular and intraarticular soft tissue of the knee was gradually removed to determine the stiffness and viscosity as a function of the tissue removal rate. The measurements showed that the removal of tissue around the joint reduces the damping of leg oscillation, and therefore decreases the stiffness and viscosity. The contribution to knee joint damping was 10% for the skin, 20% for ligaments, and 40% for muscles and tendons. Tissue removal has a very large impact on the knee stiffness and viscosity. PMID:28422623

Knee stiffness and viscosity: New implementation and perspectives in prosthesis development.

PubMed

Bohinc, Klemen; Vantur, Nejc; Torkar, Drago; Lampe, Tomaž; Hribernik, Marija; Jakovljević, Miroljub

2017-05-20

The pendulum test is a method applied to measure passive resistance of the knee. A new and simple pendulum test with instrumentation based on infrared camera was used to evaluate knee stiffness and viscosity on a female human cadaver. The stiffness and viscosity were calculated based on the kinetic data. During the measurements, the periarticular and intraarticular soft tissue of the knee was gradually removed to determine the stiffness and viscosity as a function of the tissue removal rate. The measurements showed that the removal of tissue around the joint reduces the damping of leg oscillation, and therefore decreases the stiffness and viscosity. The contribution to knee joint damping was 10% for the skin, 20% for ligaments, and 40% for muscles and tendons. Tissue removal has a very large impact on the knee stiffness and viscosity.

Effects of Low-Intensity Pulsed Ultrasound for Preventing Joint Stiffness in Immobilized Knee Model in Rats.

PubMed

Itaya, Nobuyuki; Yabe, Yutake; Hagiwara, Yoshihiro; Kanazawa, Kenji; Koide, Masashi; Sekiguchi, Takuya; Yoshida, Shinichirou; Sogi, Yasuhito; Yano, Toshihisa; Tsuchiya, Masahiro; Saijo, Yoshihumi; Itoi, Eiji

2018-06-01

The purpose of this study was to examine the effect of low-intensity pulsed ultrasound (LIPUS) in preventing joint stiffness. Unilateral knee joints were immobilized in two groups of rats (n = 6/period/group). Under general anesthesia, the immobilized knee joints were exposed to LIPUS for 20 min/d, 5 d/wk, using an existing LIPUS device (LIPUS group, 1.5-MHz frequency, 1.0-kHz repetition cycle, 200-µs burst width and 30-mW/cm 2 power output) until endpoints (2, 4 or 6 wk). In the control group, general anesthesia alone was administered in the same manner as in the other group. The variables compared between the groups included joint angles; histologic, histomorphometric and immunohistochemical analyses; quantitative reverse transcription polymerase chain reactions; and tissue elasticity. LIPUS had a preventive effect on joint stiffness, resulting in decreased adhesion, fibrosis and inflammation and hypoxic response after joint immobilization. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

A review of models of vertical, leg, and knee stiffness in adults for running, jumping or hopping tasks.

PubMed

Serpell, Benjamin G; Ball, Nick B; Scarvell, Jennie M; Smith, Paul N

2012-01-01

The 'stiffness' concept originates from Hooke's law which states that the force required to deform an object is related to a spring constant and the distance that object is deformed. Research into stiffness in the human body is undergoing unprecedented popularity; possibly because stiffness has been associated with sporting performance and some lower limb injuries. However, some inconsistencies surrounding stiffness measurement exists bringing into question the integrity of some research related to stiffness. The aim of this study was to review literature which describes how vertical, leg and knee stiffness has been measured in adult populations while running, jumping or hopping. A search of the entire MEDLINE, PubMed and SPORTDiscus databases and an iterative reference check was performed. Sixty-seven articles were retrieved; 21 measured vertical stiffness, 51 measured leg stiffness, and 22 measured knee stiffness. Thus, some studies measured several 'types' of stiffness. Vertical stiffness was typically the quotient of ground reaction force and centre of mass displacement. For leg stiffness it was and change in leg length, and for the knee it was the quotient of knee joint moments and change in joint angle. Sample size issues and measurement techniques were identified as limitations to current research.

Knee joint stiffness in individuals with and without knee osteoarthritis: a preliminary study.

PubMed

Oatis, Carol A; Wolff, Edward F; Lennon, Sandra K

2006-12-01

Descriptive, case-matched comparison. To compare the knee joint stiffness and damping coefficients of individuals with knee osteoarthritis (KOA) to those of age- and gender-matched individuals without KOA. A secondary purpose was to investigate relationships between these coefficients and complaints of stiffness in individuals with KOA. KOA is a leading cause of disability, and stiffness is a common complaint in individuals with KOA. Yet the most common method of assessing knee joint stiffness is through a self-report questionnaire. Stiffness and damping coefficients at the knee were calculated in 10 volunteers (mean age +/- SD, 64.1+/-15.5 years) with KOA and compared to coefficients from age-and gender-matched individuals without KOA, collected in a previous study (mean age +/- SD, 62.1+/-13.9 years). Stiffness and damping coefficients were calculated from the angular motion of the knee during a relaxed oscillation. Spearman correlation coefficients were calculated between stiffness and damping coefficients and WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) scores for subjects with KOA. Independent 2-tailed t tests revealed significantly larger damping coefficients (P = .035) among those with KOA (95% CI, 0.10-2.32 Nm s/rad). Spearman rank correlations revealed a significant positive relationship (r = .85, P = .003) between the damping coefficient and the stiffness subscore of the WOMAC. This study offers preliminary data demonstrating the feasibility of measuring stiffness and damping coefficients in individuals with KOA. Additionally, the damping coefficient is increased in people with KOA when compared to age- and gender-matched individuals without KOA. The damping coefficient appears to be associated with the complaints of stiffness reported by the WOMAC.

Linear parameter varying identification of ankle joint intrinsic stiffness during imposed walking movements.

PubMed

Sobhani Tehrani, Ehsan; Jalaleddini, Kian; Kearney, Robert E

2013-01-01

This paper describes a novel model structure and identification method for the time-varying, intrinsic stiffness of human ankle joint during imposed walking (IW) movements. The model structure is based on the superposition of a large signal, linear, time-invariant (LTI) model and a small signal linear-parameter varying (LPV) model. The methodology is based on a two-step algorithm; the LTI model is first estimated using data from an unperturbed IW trial. Then, the LPV model is identified using data from a perturbed IW trial with the output predictions of the LTI model removed from the measured torque. Experimental results demonstrate that the method accurately tracks the continuous-time variation of normal ankle intrinsic stiffness when the joint position changes during the IW movement. Intrinsic stiffness gain decreases from full plantarflexion to near the mid-point of plantarflexion and then increases substantially as the ankle is dosriflexed.

Experimental behaviour of beam-column connection using cold-formed steel sections with rectangular gusset-plate

NASA Astrophysics Data System (ADS)

Aminuddin, K. M.; Saggaff, Anis; Tahir, Mahmood Md

2017-11-01

Beam-to-column connections setting up as isolated joint of cold-formed steel sections were tested up to failure. This experiment was conducted to observe the behaviour of connection in term of strength, stiffness and ductility. The type of connection used was rectangular gusset plate which stiffen the beam-to-column connection. The behaviour of the proposed connection was expressed with Moment-Rotation curves plotted from the experiment test results. The capacity of connections on this research were done in two ways: theoretical calculation by adopting Eurocode 3 BS EN 1993-1-8:2005 and experimental test results. The theoretical calculation of the moment capacit y of the proposed connection has found (Mj) to be 10.78 kNm with joint stiffness (Sj) amount to 458.53 kNm/rad. The experimental test results has recorded that the Moment capacity (Mj) of 15.68 kNm with joint stiffness (Sj) of 1948.06 kNm/rad. The moment ratio of theoretical to experimental amount to 0.69. The joint stiffness ratio of theoretical to experimental amount to 0.24.

Biomechanical effects of transverse partial sacrectomy on the sacroiliac joints: an in vitro human cadaveric investigation of the borderline of sacroiliac joint instability.

PubMed

Yu, Binsheng; Zheng, Zhaomin; Zhuang, Xinming; Chen, Hui; Xie, Denghui; Luk, K D K; Lu, W W

2009-06-01

In vitro laboratory study. To measure the effects of transverse partial sacrectomies on the compressive and torsional stiffness of the sacroiliac joints. Surgical treatment for sacral tumor of different location and nature includes partial or complete sacrectomy. Though the biomechanical investigations about the local destructive force of residual sacrum after partial sacrectomy have been reported, biomechanical properties of the residual sacroiliac joints after different transverse partial sacrectomies remain unknown. Seven fresh human cadaveric L5-pelves with normal bone mineral density were used in this study. Each specimen was tested in intact condition first, followed by a series of segmental transverse partial sacrectomies: under S2 partial sacrectomy (U-S2); U-(1/2)S2; U-S1; U-(1/2)S1; and right side sacroiliac joint resection (one-side). A material testing machine was used to apply 800 N compression and 7 Nm torsion loads through the L5/S1 joint. The resected dimensional area of sacroiliac joints and structural stiffness of the residual sacroiliac joints were analyzed. Average percentages of the resected area of sacroiliac joints were 8.4% in U-S2, 15.1% in U-(1/2)S2, 24.8% in U-S1, and 72.3% in U-(1/2)S1, respectively. In compression U-S2 approximately one-side preserved 98.7%, 97.1%, 94.4%, 82.9%, and 55.2% of the initial stiffness of the sacroiliac joint, respectively. No significant differences were detected among intact, U-S2, U-(1/2)S2, and U-S1 (P > 0.05). However, compressive stiffness of U-(1/2)S1 and one-side was markedly less than that of intact, U-S2, and U-(1/2)S2 (P < 0.05). In Torsion U-S2 approximately one-side preserved 90.7%, 88.5%, 81.9%, 71.9%, and 44.5% of the initial sacroiliac joint stiffness, respectively. No significant differences were demonstrated among intact, U-S2, and U-(1/2)S2 (P > 0.05); However, U-S1, U-(1/2)S1 and one-side exhibited significantly less torsional stiffness than intact and U-S2 (P < 0.05). In surgical treatment of distal sacral tumor, transverse partial sacrectomy involving S1 could result in rotational instability, and the resection level beyond (1/2)S1 further led to compressive instability. When the sacrectomy was at or above the S1/2 level, local reconstruction should be considered.

Low-Friction, High-Stiffness Joint for Uniaxial Load Cell

NASA Technical Reports Server (NTRS)

Lewis, James L.; Le, Thang; Carroll, Monty B.

2007-01-01

A universal-joint assembly has been devised for transferring axial tension or compression to a load cell. To maximize measurement accuracy, the assembly is required to minimize any moments and non-axial forces on the load cell and to exhibit little or no hysteresis. The requirement to minimize hysteresis translates to a requirement to maximize axial stiffness (including minimizing backlash) and a simultaneous requirement to minimize friction. In practice, these are competing requirements, encountered repeatedly in efforts to design universal joints. Often, universal-joint designs represent compromises between these requirements. The improved universal-joint assembly contains two universal joints, each containing two adjustable pairs of angular-contact ball bearings. One might be tempted to ask why one could not use simple ball-and-socket joints rather than something as complex as universal joints containing adjustable pairs of angularcontact ball bearings. The answer is that ball-and-socket joints do not offer sufficient latitude to trade stiffness versus friction: the inevitable result of an attempt to make such a trade in a ball-and-socket joint is either too much backlash or too much friction. The universal joints are located at opposite ends of an axial subassembly that contains the load cell. The axial subassembly includes an axial shaft, an axial housing, and a fifth adjustable pair of angular-contact ball bearings that allows rotation of the axial housing relative to the shaft. The preload on each pair of angular-contact ball bearings can be adjusted to obtain the required stiffness with minimal friction, tailored for a specific application. The universal joint at each end affords two degrees of freedom, allowing only axial force to reach the load cell regardless of application of moments and non-axial forces. The rotational joint on the axial subassembly affords a fifth degree of freedom, preventing application of a torsion load to the load cell.

A Subspace Approach to the Structural Decomposition and Identification of Ankle Joint Dynamic Stiffness.

PubMed

Jalaleddini, Kian; Tehrani, Ehsan Sobhani; Kearney, Robert E

2017-06-01

The purpose of this paper is to present a structural decomposition subspace (SDSS) method for decomposition of the joint torque to intrinsic, reflexive, and voluntary torques and identification of joint dynamic stiffness. First, it formulates a novel state-space representation for the joint dynamic stiffness modeled by a parallel-cascade structure with a concise parameter set that provides a direct link between the state-space representation matrices and the parallel-cascade parameters. Second, it presents a subspace method for the identification of the new state-space model that involves two steps: 1) the decomposition of the intrinsic and reflex pathways and 2) the identification of an impulse response model of the intrinsic pathway and a Hammerstein model of the reflex pathway. Extensive simulation studies demonstrate that SDSS has significant performance advantages over some other methods. Thus, SDSS was more robust under high noise conditions, converging where others failed; it was more accurate, giving estimates with lower bias and random errors. The method also worked well in practice and yielded high-quality estimates of intrinsic and reflex stiffnesses when applied to experimental data at three muscle activation levels. The simulation and experimental results demonstrate that SDSS accurately decomposes the intrinsic and reflex torques and provides accurate estimates of physiologically meaningful parameters. SDSS will be a valuable tool for studying joint stiffness under functionally important conditions. It has important clinical implications for the diagnosis, assessment, objective quantification, and monitoring of neuromuscular diseases that change the muscle tone.

Anti-buckling design of variable stiffness composite cylinder under combined loading based on the multi-objective optimization method

NASA Astrophysics Data System (ADS)

Zheng, Y.; Chen, J.

2018-06-01

Variable stiffness composite structures take full advantages of composite’s design ability. An enlarged design space will make the structure’s performance more excellent. Through an optimal design of a variable stiffness cylinder, the buckling capacity of the cylinder will be increased as compared with its constant stiffness counterpart. In this paper, variable stiffness composite cylinders sustaining combined loadings are considered, and the optimization is conducted based on the multi-objective optimization method. The results indicate that variable stiffness cylinder’s loading capacity is increased significantly as compared with the constant stiffness, especially when an inhomogeneous loading is considered.

Assessment of passive knee stiffness and viscosity in individuals with spinal cord injury using pendulum test

PubMed Central

Joghtaei, Mahmoud; Arab, Amir Massoud; Hashemi-Nasl, Hamed; Joghataei, Mohammad Taghi; Tokhi, Mohammad Osman

2015-01-01

Objective Stiffness and viscosity represent passive resistances to joint motion related with the structural properties of the joint tissue and of the musculotendinous complex. Both parameters can be affected in patients with spinal cord injury (SCI). The purpose of this study was to measure passive knee stiffness and viscosity in patients with SCI with paraplegia and healthy subjects using Wartenberg pendulum test. Design Non-experimental, cross-sectional, case–control design. Setting An outpatient physical therapy clinic, University of social welfare and Rehabilitation Science, Iran. Patients A sample of convenience sample of 30 subjects participated in the study. Subjects were categorized into two groups: individuals with paraplegic SCI (n = 15, age: 34.60 ± 9.18 years) and 15 able-bodied individuals as control group (n = 15, age: 30.66 ± 11.13 years). Interventions Not applicable. Main measures Passive pendulum test of Wartenberg was used to measure passive viscous-elastic parameters of the knee (stiffness, viscosity) in all subjects. Results Statistical analysis (independent t-test) revealed significant difference in the joint stiffness between healthy subjects and those with paraplegic SCI (P = 0.01). However, no significant difference was found in the viscosity between two groups (P = 0.17). Except for first peak flexion angle, all other displacement kinematic parameters exhibited no statistically significant difference between normal subjects and subjects with SCI. Conclusions Patients with SCI have significantly greater joint stiffness compared to able-bodied subjects. PMID:25437824

Treadmill training with an incline reduces ankle joint stiffness and improves active range of movement during gait in adults with cerebral palsy.

PubMed

Lorentzen, Jakob; Kirk, Henrik; Fernandez-Lago, Helena; Frisk, Rasmus; Scharff Nielsen, Nanna; Jorsal, Martin; Nielsen, Jens Bo

2017-05-01

We investigated if 30 min of daily treadmill training with an incline for 6 weeks would reduce ankle joint stiffness and improve active range of movement in adults with cerebral palsy (CP). The study was designed as a randomized controlled clinical trial including 32 adults with CP (GMFCS 1-3) aged 38.1 SD 12 years. The training group (n = 16) performed uphill treadmill training at home daily for 30 min for 6 weeks in addition to their usual activities. Passive and reflex mediated stiffness and range of motion (ROM) of the ankle joint, kinematic and functional measures of gait were obtained before and after the intervention/control period. Intervention subjects trained 31.4 SD 10.1 days for 29.0 SD 2.3 min (total) 15.2 h. Passive ankle joint stiffness was reduced (F = 5.1; p = 0.031), maximal gait speed increased (F = 42.8, p < 0.001), amplitude of toe lift prior to heel strike increased (F = 5.3, p < 0.03) and ankle angle at heel strike was decreased (F = 12.5; p < 0.001) significant in the training group as compared to controls. Daily treadmill training with an incline for 6 weeks reduces ankle joint stiffness and increases active ROM during gait in adults with CP. Intensive gait training may thus be beneficial in preventing and reducing contractures and help to maintain functional gait ability in adults with CP. Implications for rehabilitation Uphill gait training is an effective way to reduce ankle joint stiffness in adult with contractures. 6 weeks of daily uphill gait training improves functional gait parameters such as gait speed and dorsal flexion during gait in adults with cerebral palsy.

Joining of Components of Complex Structures for Improved Dynamic Response

DTIC Science & Technology

2011-10-28

system- level mass and stiffness matrices and force vector (at each frequency in the range of interest). To address this issue a series of complex...displacements of all candidate joint locations by using the system- level mass and stiffness matrices and force vector (at each frequency in the range of...joints. In contrast, Li et al. [10] proposed a fastener layout/topology that achieves an almost uniform stress level in each joint, and adopted

Experimental Investigation of Composite Pressure Vessel Performance and Joint Stiffness for Pyramid and Inverted Pyramid Joints

NASA Technical Reports Server (NTRS)

Verhage, Joseph M.; Bower, Mark V.; Gilbert, Paul A. (Technical Monitor)

2001-01-01

The focus of this study is on the suitability in the application of classical laminate theory analysis tools for filament wound pressure vessels with adhesive laminated joints in particular: pressure vessel wall performance, joint stiffness and failure prediction. Two 18-inch diameter 12-ply filament wound pressure vessels were fabricated. One vessel was fabricated with a 24-ply pyramid laminated adhesive double strap butt joint. The second vessel was fabricated with the same number of plies in an inverted pyramid joint. Results from hydrostatic tests are presented. Experimental results were used as input to the computer programs GENLAM and Laminate, and the output compared to test. By using the axial stress resultant, the classical laminate theory results show a correlation within 1% to the experimental results in predicting the pressure vessel wall pressure performance. The prediction of joint stiffness for the two adhesive joints in the axial direction is within 1% of the experimental results. The calculated hoop direction joint stress resultant is 25% less than the measured resultant for both joint configurations. A correction factor is derived and used in the joint analysis. The correction factor is derived from the hoop stress resultant from the tank wall performance investigation. The vessel with the pyramid joint is determined to have failed in the joint area at a hydrostatic pressure 33% value below predicted failure. The vessel with the inverted pyramid joint failed in the wall acreage at a hydrostatic pressure within 10% of the actual failure pressure.

Multi-scale computational study of the mechanical regulation of cell mitotic rounding in epithelia

PubMed Central

Xu, Zhiliang; Zartman, Jeremiah J.; Alber, Mark

2017-01-01

Mitotic rounding during cell division is critical for preventing daughter cells from inheriting an abnormal number of chromosomes, a condition that occurs frequently in cancer cells. Cells must significantly expand their apical area and transition from a polygonal to circular apical shape to achieve robust mitotic rounding in epithelial tissues, which is where most cancers initiate. However, how cells mechanically regulate robust mitotic rounding within packed tissues is unknown. Here, we analyze mitotic rounding using a newly developed multi-scale subcellular element computational model that is calibrated using experimental data. Novel biologically relevant features of the model include separate representations of the sub-cellular components including the apical membrane and cytoplasm of the cell at the tissue scale level as well as detailed description of cell properties during mitotic rounding. Regression analysis of predictive model simulation results reveals the relative contributions of osmotic pressure, cell-cell adhesion and cortical stiffness to mitotic rounding. Mitotic area expansion is largely driven by regulation of cytoplasmic pressure. Surprisingly, mitotic shape roundness within physiological ranges is most sensitive to variation in cell-cell adhesivity and stiffness. An understanding of how perturbed mechanical properties impact mitotic rounding has important potential implications on, amongst others, how tumors progressively become more genetically unstable due to increased chromosomal aneuploidy and more aggressive. PMID:28531187

Model-Based Estimation of Knee Stiffness

PubMed Central

Pfeifer, Serge; Vallery, Heike; Hardegger, Michael; Riener, Robert; Perreault, Eric J.

2013-01-01

During natural locomotion, the stiffness of the human knee is modulated continuously and subconsciously according to the demands of activity and terrain. Given modern actuator technology, powered transfemoral prostheses could theoretically provide a similar degree of sophistication and function. However, experimentally quantifying knee stiffness modulation during natural gait is challenging. Alternatively, joint stiffness could be estimated in a less disruptive manner using electromyography (EMG) combined with kinetic and kinematic measurements to estimate muscle force, together with models that relate muscle force to stiffness. Here we present the first step in that process, where we develop such an approach and evaluate it in isometric conditions, where experimental measurements are more feasible. Our EMG-guided modeling approach allows us to consider conditions with antagonistic muscle activation, a phenomenon commonly observed in physiological gait. Our validation shows that model-based estimates of knee joint stiffness coincide well with experimental data obtained using conventional perturbation techniques. We conclude that knee stiffness can be accurately estimated in isometric conditions without applying perturbations, which presents an important step towards our ultimate goal of quantifying knee stiffness during gait. PMID:22801482

A novel approach to study effects of asymmetric stiffness on parametric instabilities of multi-rotor-system

NASA Astrophysics Data System (ADS)

Jain, Anuj Kumar; Rastogi, Vikas; Agrawal, Atul Kumar

2018-01-01

The main focus of this paper is to study effects of asymmetric stiffness on parametric instabilities of multi-rotor-system through extended Lagrangian formalism, where symmetries are broken in terms of the rotor stiffness. The complete insight of dynamic behaviour of multi-rotor-system with asymmetries is evaluated through extension of Lagrangian equation with a case study. In this work, a dynamic mathematical model of a multi-rotor-system through a novel approach of extension of Lagrangian mechanics is developed, where the system is having asymmetries due to varying stiffness. The amplitude and the natural frequency of the rotor are obtained analytically through the proposed methodology. The bond graph modeling technique is used for modeling the asymmetric rotor. Symbol-shakti® software is used for the simulation of the model. The effects of the stiffness of multi-rotor-system on amplitude and frequencies are studied using numerical simulation. Simulation results show a considerable agreement with the theoretical results obtained through extended Lagrangian formalism. It is further shown that amplitude of the rotor increases inversely the stiffness of the rotor up to a certain limit, which is also affirmed theoretically.

A comparison of muscle stiffness and musculoarticular stiffness of the knee joint in young athletic males and females.

PubMed

Wang, Dan; De Vito, Giuseppe; Ditroilo, Massimiliano; Fong, Daniel T P; Delahunt, Eamonn

2015-06-01

The objective of this study was to investigate the gender-specific differences in peak torque (PT), muscle stiffness (MS) and musculoarticular stiffness (MAS) of the knee joints in a young active population. Twenty-two male and twenty-two female recreational athletes participated. PT of the knee joint extensor musculature was assessed on an isokinetic dynamometer, MS of the vastus lateralis (VL) muscle was measured in both relaxed and contracted conditions, and knee joint MAS was quantified using the free oscillation technique. Significant gender differences were observed for all dependent variables. Females demonstrated less normalized PT (mean difference (MD)=0.4Nm/kg, p=0.005, η(2)=0.17), relaxed MS (MD=94.2N/m, p<.001, η(2)=0.53), contracted MS (MD=162.7N/m, p<.001, η(2)=0.53) and MAS (MD=422.1N/m, p<.001, η(2)=0.23) than males. MAS increased linearly with the external load in both genders with males demonstrating a significantly higher slope (p=0.019) than females. The observed differences outlined above may contribute to the higher knee joint injury incidence and prevalence in females when compared to males. Copyright © 2015 Elsevier Ltd. All rights reserved.

Methodological considerations of task and shoe wear on joint energetics during landing.

PubMed

Shultz, Sandra J; Schmitz, Randy J; Tritsch, Amanda J; Montgomery, Melissa M

2012-02-01

To better understand methodological factors that alter landings strategies, we compared sagittal plane joint energetics during the initial landing phase of drop jumps (DJ) vs. drop landings (DL), and when shod vs. barefoot. Surface electromyography, kinematic and kinetic data were obtained on 10 males and 10 females during five consecutive drop landings and five consecutive drop jumps (0.45m) when shod and when barefoot. Energy absorption was greater in the DJ vs. DL (P=.002), due to increased energy absorption at the hip during the DJ. Joint stiffness/impedance was more affected by shoe condition, where overall stiffness/impedance was greater in shod compared to barefoot conditions (P=.036). Further, hip impedance was greater in shod vs. barefoot for the DL only (via increased peak hip extensor moment in DL), while ankle stiffness was greater in the barefoot vs. shod condition for the DJ only (via decreased joint excursion and increased peak joint moment in DJ vs. DL) (P=.011). DJ and DL place different neuromechanical demands upon the lower extremities, and shoe wear may alter impact forces that modulate stiffness/impedance strategies. The impact of these methodological differences should be considered when comparing landing biomechanics across studies. Copyright © 2011 Elsevier Ltd. All rights reserved.

Unintentional Changes in the Apparent Stiffness of the Multi-Joint Limb

PubMed Central

Zhou, Tao; Zatsiorsky, Vladimir M.; Latash, Mark L.

2015-01-01

We explored the phenomenon of unintentional changes in the apparent stiffness of the human arm produced by transient changes in the external force. The subjects performed a positional task against a constant baseline force and were instructed not to react to changes in the force. A HapticMaster robot produced a smooth force increase (a perturbation) leading to a hand movement, followed by a dwell time. No visible hand drift was observed during the dwell time. After the robot force dropped to its initial baseline value, the hand moved towards the initial position but stopped short of it. Small perturbations were applied at different time intervals along different directions during the dwell time. Arm apparent stiffness distribution in a horizontal plane was approximated with an ellipse. The apparent stiffness magnitude along the main axis of the ellipse showed a non-monotonic increase with dwell time while the apparent stiffness along the minor axis did not change significantly. We interpreted the early part of the changes in the apparent stiffness as due to peripheral muscle properties. The later part is interpreted as caused by a combination of two processes, a drift in the referent hand coordinate due to the hypothesized back-coupling between the referent and actual hand coordinates and an implicit instruction to keep the hand steady when no changes in robot-generated force took place. The data provide support for the idea of back-coupling between the referent and actual body configurations, which may be an important contributor to stability of motor actions. PMID:26169103

Low-Intensity Vibration as a Treatment for Traumatic Muscle Injury

DTIC Science & Technology

2015-08-01

improving muscle healing, thereby reducing joint stiffness and increasing mobility of polytrauma patients. 15. SUBJECT TERMS Skeletal muscle repair...mobility of polytrauma patients. 2. KEYWORDS Skeletal muscle repair, low-intensity vibration, monocytes/macrophages, endothelial precursor cells...innovative, non-invasive and simple treatment for improving muscle healing and thereby reducing joint stiffness and increasing mobility of polytrauma

Investigation of the performance of articular cartilage and synthetic biomaterials in multi-directional sliding motion as in orthopedic implants

NASA Astrophysics Data System (ADS)

Schwartz, Christian John

The performance of several synthetic biomaterials and bovine articular cartilage were investigated in terms of their suitability for use as articulating surfaces in artificial joints. The Dual-Axis Wear Simulator (DAWS), a wear testing machine that simulates conditions in a synovial joint, was designed and fabricated to enable investigators to measure the wear of such materials in multi-directional sliding while immersed in a bovine serum lubricant solution. This machine was used initially to determine the wear mechanisms and wear amounts of ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), polyoxymethylene (POM), and the compliant elastomer Pellethane(TM) 2363-80A. It was found that the compliant material produced lower wear. Dynamic mechanical analysis was used to determine that bovine articular cartilage had a very significant amount of viscoelasticity to support static loads and damp impact loads. Furthermore, the use of a compliant counterface led to lower wear in the cartilage as compared to a rigid counterface. Pt-Zr quasicrystals were used as fillers in UHMWPE, and the wear, stiffness, and impact toughness of the filled polymer were shown to be comparable or better than those of UHMWPE that had been irradiation crosslinked. Crosslinked UHMWPE was investigated for its susceptibility to oxidative degradation and increased wear. It was found that thermal stabilization of the polymer could be eliminated if a mild amount crosslinking was used. Furthermore, there was no degradation in wear resistance of mildly crosslinked and non-stabilized UHMWPE even after accelerated aging. Based on the results of this work and lessons learned about compliance and wear resistance, blends were produced by using surface-activated UHMWPE particles as fillers in elastomeric PUR. The blends showed better wear resistance than UHMWPE, as well as increased stiffness and damping over PUR. The results of this work indicated that there is great potential for the development of new biomaterials and materials treatment methods to produce more durable articulating components in artificial joints.

Contribution of knee flexor and extensor strength on sex-specific energy absorption and torsional joint stiffness during drop jumping.

PubMed

Schmitz, Randy J; Shultz, Sandra J

2010-01-01

Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Cross-sectional study. Laboratory environment. Recreationally active, college-aged students (41 women: age  =  22.1 ± 2.9 years, height  =  1.63 ± 0.07 m, mass  =  59.3 ± 8.0 kg; 40 men: age  =  22.4 ± 2.8 years, height  =  1.77 ± 0.1 m, mass  =  80.9 ± 14.1 kg). Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Lower extremity joint energetics (J × N(-1) × m(-1)) and torsional joint stiffnesses (Nm × N(-1) × m(-1) × degrees(-1)) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R(2)  =  0.11, P  =  .04), and greater knee flexor strength predicted greater hip torsional stiffness (R(2)  =  0.12, P  =  .03). Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences.

Virtual trajectories of single-joint movements performed under two basic strategies.

PubMed

Latash, M L; Gottlieb, G L

1992-01-01

The framework of the equilibrium point hypothesis has been used to analyse motor control processes for single-joint movements. Virtual trajectories and joint stiffness were reconstructed for different movement speeds and distances when subjects were instructed either to move "as fast as possible" or to intentionally vary movement speed. These instructions are assumed to be associated with similar or different rates of change of hypothetical central control variables (corresponding to the speed-sensitive and speed-insensitive strategies). The subjects were trained to perform relatively slow, moderately fast and very fast (nominal movement times 800, 400 and 250 ms) single-joint elbow flexion movements against a constant extending torque bias. They were instructed to reproduce the motor command for a series of movements while ignoring possible changes in the external torque which could slowly and unpredictably increase, decrease, or remain constant. The total muscle torque was calculated as a sum of external and inertial components. Fast movements over different distances were made with the speed-insensitive strategy. They were characterized by an increase in joint stiffness near the midpoint of the movements which was relatively independent of movement amplitude. Their virtual trajectories had a non-monotonic N-shape. All three arms of the N-shape scaled with movement amplitude. Movements over one distance at different speeds were made with a speed-sensitive strategy. They demonstrated different patterns of virtual trajectories and joint stiffness that depended on movement speed. The N-shape became less apparent for moderately fast movements and virtually disappeared for the slow movements. Slow movements showed no visible increase in joint stiffness.(ABSTRACT TRUNCATED AT 250 WORDS)

Low Intensity Vibration as a Treatment for Traumatic Muscle Injury

DTIC Science & Technology

2016-08-01

improving muscle healing, thereby reducing joint stiffness and increasing mobility of polytrauma patients. 15. SUBJECT TERMS Skeletal muscle repair...and increasing mobility of polytrauma patients. 2. KEYWORDS Skeletal muscle repair, low-intensity vibration, monocytes/macrophages, endothelial...reducing joint stiffness and increasing mobility of polytrauma patients. 11 What was the impact on other disciplines? Nothing to report What was

Mechanical model of suture joints with fibrous connective layer

NASA Astrophysics Data System (ADS)

Miroshnichenko, Kateryna; Liu, Lei; Tsukrov, Igor; Li, Yaning

2018-02-01

A composite model for suture joints with a connective layer of aligned fibers embedded in soft matrix is proposed. Based on the principle of complementary virtual work, composite cylinder assemblage (CCA) approach and generalized self-consistent micro-mechanical models, a hierarchical homogenization methodology is developed to systematically quantify the synergistic effects of suture morphology and fiber orientation on the overall mechanical properties of sutures. Suture joints with regular triangular wave-form serve as an example material system to apply this methodology. Both theoretical and finite element mechanical models are developed and compared to evaluate the overall normal stiffness of sutures as a function of wavy morphology of sutures, fiber orientation, fiber volume fraction, and the mechanical properties of fibers and matrix in the interfacial layer. It is found that generally due to the anisotropy-induced coupling effects between tensile and shear deformation, the effective normal stiffness of sutures is highly dependent on the fiber orientation in the connective layer. Also, the effective shear modulus of the connective layer and the stiffness ratio between the fiber and matrix significantly influence the effects of fiber orientation. In addition, optimal fiber orientations are found to maximize the stiffness of suture joints.

Bio-inspired control of joint torque and knee stiffness in a robotic lower limb exoskeleton using a central pattern generator.

PubMed

Schrade, Stefan O; Nager, Yannik; Wu, Amy R; Gassert, Roger; Ijspeert, Auke

2017-07-01

Robotic lower limb exoskeletons are becoming increasingly popular in therapy and recreational use. However, most exoskeletons are still rather limited in their locomotion speed and the activities of daily live they can perform. Furthermore, they typically do not allow for a dynamic adaptation to the environment, as they are often controlled with predefined reference trajectories. Inspired by human leg stiffness modulation during walking, variable stiffness actuators increase flexibility without the need for more complex controllers. Actuation with adaptable stiffness is inspired by the human leg stiffness modulation during walking. However, this actuation principle also introduces the stiffness setpoint as an additional degree of freedom that needs to be coordinated with the joint trajectories. As a potential solution to this issue a bio-inspired controller based on a central pattern generator (CPG) is presented in this work. It generates coordinated joint torques and knee stiffness modulations to produce flexible and dynamic gait patterns for an exoskeleton with variable knee stiffness actuation. The CPG controller is evaluated and optimized in simulation using a model of the exoskeleton. The CPG controller produced stable and smooth gait for walking speeds from 0.4 m/s up to 1.57 m/s with a torso stabilizing force that simulated the use of crutches, which are commonly needed by exoskeleton users. Through the CPG, the knee stiffness intrinsically adapted to the frequency and phase of the gait, when the speed was changed. Additionally, it adjusted to changes in the environment in the form of uneven terrain by reacting to ground contact forces. This could allow future exoskeletons to be more adaptive to various environments, thus making ambulation more robust.

Midtarsal locking, the windlass mechanism, and running strike pattern: A kinematic and kinetic assessment.

PubMed

Bruening, Dustin A; Pohl, Michael B; Takahashi, Kota Z; Barrios, Joaquin A

2018-05-17

Changes in running strike pattern affect ankle and knee mechanics, but little is known about the influence of strike pattern on the joints distal to the ankle. The purpose of this study was to explore the effects of forefoot strike (FFS) and rearfoot strike (RFS) running patterns on foot kinematics and kinetics, from the perspectives of the midtarsal locking theory and the windlass mechanism. Per the midtarsal locking theory, we hypothesized that the ankle would be more inverted in early stance when using a FFS, resulting in decreased midtarsal joint excursions and increased dynamic stiffness. Associated with a more engaged windlass mechanism, we hypothesized that a FFS would elicit increased metatarsophalangeal joint excursions and negative work in late stance. Eighteen healthy female runners ran overground with both FFS and RFS patterns. Instrumented motion capture and a validated multi-segment foot model were used to analyze midtarsal and metatarsophalangeal joint kinematics and kinetics. During early stance in FFS the ankle was more inverted, with concurrently decreased midtarsal eversion (p < 0.001) and abduction excursions (p = 0.003) but increased dorsiflexion excursion (p = 0.005). Dynamic midtarsal stiffness did not differ (p = 0.761). During late stance in FFS, metatarsophalangeal extension was increased (p = 0.009), with concurrently increased negative work (p < 0.001). In addition, there was simultaneously increased midtarsal positive work (p < 0.001), suggesting enhanced power transfer in FFS. Clear evidence for the presence of midtarsal locking was not observed in either strike pattern during running. However, the windlass mechanism appeared to be engaged to a greater extent during FFS. Copyright © 2018 Elsevier Ltd. All rights reserved.

Neural Network Optimization of Ligament Stiffnesses for the Enhanced Predictive Ability of a Patient-Specific, Computational Foot/Ankle Model.

PubMed

Chande, Ruchi D; Wayne, Jennifer S

2017-09-01

Computational models of diarthrodial joints serve to inform the biomechanical function of these structures, and as such, must be supplied appropriate inputs for performance that is representative of actual joint function. Inputs for these models are sourced from both imaging modalities as well as literature. The latter is often the source of mechanical properties for soft tissues, like ligament stiffnesses; however, such data are not always available for all the soft tissues nor is it known for patient-specific work. In the current research, a method to improve the ligament stiffness definition for a computational foot/ankle model was sought with the greater goal of improving the predictive ability of the computational model. Specifically, the stiffness values were optimized using artificial neural networks (ANNs); both feedforward and radial basis function networks (RBFNs) were considered. Optimal networks of each type were determined and subsequently used to predict stiffnesses for the foot/ankle model. Ultimately, the predicted stiffnesses were considered reasonable and resulted in enhanced performance of the computational model, suggesting that artificial neural networks can be used to optimize stiffness inputs.

Acute effects of static stretching on passive stiffness of the hamstring muscles calculated using different mathematical models.

PubMed

Nordez, Antoine; Cornu, Christophe; McNair, Peter

2006-08-01

The aim of this study was to assess the effects of static stretching on hamstring passive stiffness calculated using different data reduction methods. Subjects performed a maximal range of motion test, five cyclic stretching repetitions and a static stretching intervention that involved five 30-s static stretches. A computerised dynamometer allowed the measurement of torque and range of motion during passive knee extension. Stiffness was then calculated as the slope of the torque-angle relationship fitted using a second-order polynomial, a fourth-order polynomial, and an exponential model. The second-order polynomial and exponential models allowed the calculation of stiffness indices normalized to knee angle and passive torque, respectively. Prior to static stretching, stiffness levels were significantly different across the models. After stretching, while knee maximal joint range of motion increased, stiffness was shown to decrease. Stiffness decreased more at the extended knee joint angle, and the magnitude of change depended upon the model used. After stretching, the stiffness indices also varied according to the model used to fit data. Thus, the stiffness index normalized to knee angle was found to decrease whereas the stiffness index normalized to passive torque increased after static stretching. Stretching has significant effects on stiffness, but the findings highlight the need to carefully assess the effect of different models when analyzing such data.

Mechanics of Suture Joints

NASA Astrophysics Data System (ADS)

Li, Yaning; Song, Juha; Ortiz, Christine; Boyce, Mary; Ortiz Group/DMSE/MIT Team; Boyce Group/ME/MIT Team

2011-03-01

Biological sutures are joints which connect two stiff skeletal or skeletal-like components. These joints possess a wavy geometry with a thin organic layer providing adhesion. Examples of biological sutures include mammalian skulls, the pelvic assembly of the armored fish Gasterosteus aculeatus (the three-spined stickleback), and the suture joints in the shell of the red-eared slider turtle. Biological sutures allow for movement and compliance, control stress concentrations, transmit loads, reduce fatigue stress and absorb energy. In this investigation, the mechanics of the role of suture geometry in providing a naturally optimized joint is explored. In particular, analytical and numerical micromechanical models of the suture joint are constructed. The anisotropic mechanical stiffness and strength are studied as a function of suture wavelength, amplitude and the material properties of the skeletal and organic components, revealing key insights into the optimized nature of these ubiquitous natural joints.

Human-like Compliance for Dexterous Robot Hands

NASA Technical Reports Server (NTRS)

Jau, Bruno M.

1995-01-01

This paper describes the Active Electromechanical Compliance (AEC) system that was developed for the Jau-JPL anthropomorphic robot. The AEC system imitates the functionality of the human muscle's secondary function, which is to control the joint's stiffness: AEC is implemented through servo controlling the joint drive train's stiffness. The control strategy, controlling compliant joints in teleoperation, is described. It enables automatic hybrid position and force control through utilizing sensory feedback from joint and compliance sensors. This compliant control strategy is adaptable for autonomous robot control as well. Active compliance enables dual arm manipulations, human-like soft grasping by the robot hand, and opens the way to many new robotics applications.

Quantifying in vivo laxity in the anterior cruciate ligament and individual knee joint structures.

PubMed

Westover, L M; Sinaei, N; Küpper, J C; Ronsky, J L

2016-11-01

A custom knee loading apparatus (KLA), when used in conjunction with magnetic resonance imaging, enables in vivo measurement of the gross anterior laxity of the knee joint. A numerical model was applied to the KLA to understand the contribution of the individual joint structures and to estimate the stiffness of the anterior-cruciate ligament (ACL). The model was evaluated with a cadaveric study using an in situ knee loading apparatus and an ElectroForce test system. A constrained optimization solution technique was able to predict the restraining forces within the soft-tissue structures and joint contact. The numerical model presented here allowed in vivo prediction of the material stiffness parameters of the ACL in response to applied anterior loading. Promising results were obtained for in vivo load sharing within the structures. The numerical model overestimated the ACL forces by 27.61-92.71%. This study presents a novel approach to estimate ligament stiffness and provides the basis to develop a robust and accurate measure of in vivo knee joint laxity.

Model-Based Estimation of Ankle Joint Stiffness

PubMed Central

Misgeld, Berno J. E.; Zhang, Tony; Lüken, Markus J.; Leonhardt, Steffen

2017-01-01

We address the estimation of biomechanical parameters with wearable measurement technologies. In particular, we focus on the estimation of sagittal plane ankle joint stiffness in dorsiflexion/plantar flexion. For this estimation, a novel nonlinear biomechanical model of the lower leg was formulated that is driven by electromyographic signals. The model incorporates a two-dimensional kinematic description in the sagittal plane for the calculation of muscle lever arms and torques. To reduce estimation errors due to model uncertainties, a filtering algorithm is necessary that employs segmental orientation sensor measurements. Because of the model’s inherent nonlinearities and nonsmooth dynamics, a square-root cubature Kalman filter was developed. The performance of the novel estimation approach was evaluated in silico and in an experimental procedure. The experimental study was conducted with body-worn sensors and a test-bench that was specifically designed to obtain reference angle and torque measurements for a single joint. Results show that the filter is able to reconstruct joint angle positions, velocities and torque, as well as, joint stiffness during experimental test bench movements. PMID:28353683

Increased vertical impact forces and altered running mechanics with softer midsole shoes.

PubMed

Baltich, Jennifer; Maurer, Christian; Nigg, Benno M

2015-01-01

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes.

Increased Vertical Impact Forces and Altered Running Mechanics with Softer Midsole Shoes

PubMed Central

Baltich, Jennifer; Maurer, Christian; Nigg, Benno M.

2015-01-01

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes. PMID:25897963

Stress stiffened silicon nitride micro bridges array as substrate with tunable stiffness for cell culture.

PubMed

Chen, Jianfeng; Liu, Guangli; Ma, Chengfu; Zhao, Gang; Du, Wenqiang; Zhu, Wulin; Chu, Jiaru

2017-06-01

Recently, interactions between one-dimensional structural stiffness of physical micro environments and cell biological process have been widely studied. However in previous studies, the influence of structural stiffness on biological process was coupled with the influence of micro fiber curvature. Therefore decoupling the influences of fiber curvature and structural stiffness on cell biological process is of prime importance. In this study, we proposed a novel cell culture substrate comprised of silicon nitride bridges whose structure stiffness can be regulated by altering the axial residual stress without changing material and geometry properties. Both theoretical calculations and finite element simulations were performed to study the influence of residual stress on structure stiffness of bridges. Then multi-positions AFM bending tests were implemented to measure local stiffness of a single micro bridge so as to verify our predictions. NIH/3T3 mouse fibroblast cells were cultured on our substrates to examine the feasibility of the substrate application for investigating cellular response to microenvironment with variable stiffness. The results showed that cells on the edge region near bridge ends were more spread, elongated and better aligned along the bridge axial direction than those on the bridge center region. The results suggest that cells can sense and respond to the differences of stiffness and stiffness gradient between the edge and the center region of the bridges, which makes this kind of substrates can be applied in some biomedical fields, such as cell migration and wound healing. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Reduced Stiffness Dance Flooring on Lower Extremity Joint Angular Trajectories During a Ballet Jump.

PubMed

Hackney, James; Brummel, Sara; Newman, Mary; Scott, Shannon; Reinagel, Matthew; Smith, Jennifer

2015-09-01

We carried out a study to investigate how low stiffness flooring may help prevent overuse injuries of the lower extremity in dancers. It was hypothesized that performing a ballet jump (sauté) on a reduced stiffness dance floor would decrease maximum joint flexion angles and negative angular velocities at the hips, knees, or ankles compared to performing the same jump on a harder floor. The participants were 15 young adult female dancers (age range 18 to 28, mean = 20.89 ± 2.93 years) with at least 5 years of continuous ballet experience and without history of serious lower body injury, surgery, or recent pain. They performed sautés on a (low stiffness) Harlequin ® WoodSpring Floor and on a vinyl-covered hardwood on concrete floor. Maximum joint flexion angles and negative velocities at bilateral hips, knees, and ankles were measured with the "Ariel Performance Analysis System" (APAS). Paired one-tailed t-tests yielded significant decreases in maximum knee angle (average decrease = 3.4° ± 4.2°, p = 0.026) and angular negative velocity of the ankles (average decrease = 18.7°/sec ± 27.9°/sec, p = 0.009) with low stiffness flooring. If the knee angle is less acute, then the length of the external knee flexion moment arm will also be shorter and result in a smaller external knee flexion moment, given an equal landing force. Also, high velocities of eccentric muscle contraction, which are necessary to control negative angular velocity of the ankle joint, are associated with higher risk of musculotendinous injury. Hence, our findings indicate that reduced floor stiffness may indeed help decrease the likelihood of lower extremity injuries.

Contribution of Knee Flexor and Extensor Strength on Sex-Specific Energy Absorption and Torsional Joint Stiffness During Drop Jumping

PubMed Central

Schmitz, Randy J.; Shultz, Sandra J.

2010-01-01

Abstract Context: Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. Objective: To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Design: Cross-sectional study. Setting: Laboratory environment. Patients or Other Participants: Recreationally active, college-aged students (41 women: age  =  22.1 ± 2.9 years, height  =  1.63 ± 0.07 m, mass  =  59.3 ± 8.0 kg; 40 men: age  =  22.4 ± 2.8 years, height  =  1.77 ± 0.1 m, mass  =  80.9 ± 14.1 kg). Intervention(s): Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Main Outcome Measure(s): Lower extremity joint energetics (J × N−1 × m−1) and torsional joint stiffnesses (Nm × N−1 × m−1 × degrees−1) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Results: Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R2  =  0.11, P  =  .04), and greater knee flexor strength predicted greater hip torsional stiffness (R2  =  0.12, P  =  .03). Conclusions: Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences. PMID:20831388

Comparison of plantar flexor musculotendinous stiffness, geometry, and architecture in male runners with and without a history of tibial stress fracture.

PubMed

Pamukoff, Derek N; Blackburn, J Troy

2015-02-01

Greater lower extremity joint stiffness may be related to the development of tibial stress fractures in runners. Musculotendinous stiffness is the largest contributor to joint stiffness, but it is unclear what factors contribute to musculotendinous stiffness. The purpose of this study was to compare plantar flexor musculotendinous stiffness, architecture, geometry, and Achilles tendon stiffness between male runners with and without a history of tibial stress fracture. Nineteen healthy runners (age = 21 ± 2.7 years; mass = 68.2 ± 9.3 kg; height = 177.3 ± 6.0 cm) and 19 runners with a history of tibial stress fracture (age = 21 ± 2.9 years; mass = 65.3 ± 6.0 kg; height = 177.2 ± 5.2 cm) were recruited from community running groups and the university's varsity and club cross-country teams. Plantar flexor musculotendinous stiffness was estimated from the damped frequency of oscillatory motion about the ankle follow perturbation. Ultrasound imaging was used to measure architecture and geometry of the medial gastrocnemius. Dependent variables were compared between groups via one-way ANOVAs. Previously injured runners had greater plantar flexor musculotendinous stiffness (P < .001), greater Achilles tendon stiffness (P = .004), and lesser Achilles tendon elongation (P = .003) during maximal isometric contraction compared with healthy runners. No differences were found in muscle thickness, pennation angle, or fascicle length.

Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors

PubMed Central

Gao, Fan; Ren, Yupeng; Roth, Elliot J.; Harvey, Richard; Zhang, Li-Qun

2011-01-01

Background The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle-tendon unit induced by controlled ankle stretching in stroke survivors. Methods Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque-angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions. Findings Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P<0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P<0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P = 0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P<0.05). Ankle range of motion was also increased by stretching (P<0.001). Interpretation At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle-tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention. PMID:21211873

Impact attenuation properties of jazz shoes alter lower limb joint stiffness during jump landings.

PubMed

Fong Yan, Alycia; Smith, Richard M; Hiller, Claire E; Sinclair, Peter J

2017-05-01

To quantify the impact attenuation properties of the jazz shoes, and to investigate the in-vivo effect of four jazz shoe designs on lower limb joint stiffness during a dance-specific jump. Repeated measures. A custom-built mechanical shoe tester similar to that used by athletic shoe companies was used to vertically impact the forefoot and heel region of four different jazz shoe designs. Additionally, dancers performed eight sautés in second position in bare feet and the shoe conditions. Force platforms and 3D-motion capture were used to analyse the joint stiffness of the midfoot, ankle, knee and hip during the jump landings. Mechanical testing of the jazz shoes revealed significant differences in impact attenuation characteristics among each of the jazz shoe designs. Gross knee and midfoot joint stiffness were significantly affected by the jazz shoe designs in the dancers' jump landings. The tested jazz shoe designs altered the impact attenuating capacity of jump landing technique in dancers. The cushioned jazz shoes are recommended particularly for injured dancers to reduce impact on the lower limb. Jazz shoe design should consider the impact attenuation properties of the forefoot region, due to the toe-strike landing technique in dance movement. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Adjustments with running speed reveal neuromuscular adaptations during landing associated with high mileage running training.

PubMed

Verheul, Jasper; Clansey, Adam C; Lake, Mark J

2017-03-01

It remains to be determined whether running training influences the amplitude of lower limb muscle activations before and during the first half of stance and whether such changes are associated with joint stiffness regulation and usage of stored energy from tendons. Therefore, the aim of this study was to investigate neuromuscular and movement adaptations before and during landing in response to running training across a range of speeds. Two groups of high mileage (HM; >45 km/wk, n = 13) and low mileage (LM; <15 km/wk, n = 13) runners ran at four speeds (2.5-5.5 m/s) while lower limb mechanics and electromyography of the thigh muscles were collected. There were few differences in prelanding activation levels, but HM runners displayed lower activations of the rectus femoris, vastus medialis, and semitendinosus muscles postlanding, and these differences increased with running speed. HM runners also demonstrated higher initial knee stiffness during the impact phase compared with LM runners, which was associated with an earlier peak knee flexion velocity, and both were relatively unchanged by running speed. In contrast, LM runners had higher knee stiffness during the slightly later weight acceptance phase and the disparity was amplified with increases in speed. It was concluded that initial knee joint stiffness might predominantly be governed by tendon stiffness rather than muscular activations before landing. Estimated elastic work about the ankle was found to be higher in the HM runners, which might play a role in reducing weight acceptance phase muscle activation levels and improve muscle activation efficiency with running training. NEW & NOTEWORTHY Although neuromuscular factors play a key role during running, the influence of high mileage training on neuromuscular function has been poorly studied, especially in relation to running speed. This study is the first to demonstrate changes in neuromuscular conditioning with high mileage training, mainly characterized by lower thigh muscle activation after touch down, higher initial knee stiffness, and greater estimates of energy return, with adaptations being increasingly evident at faster running speeds. Copyright © 2017 the American Physiological Society.

Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping

PubMed Central

van der Krogt, Marjolein M.; de Graaf, Wendy W.; Farley, Claire T.; Moritz, Chet T.; Richard Casius, L. J.; Bobbert, Maarten F.

2009-01-01

When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain. PMID:19589956

On the stiffness matrix of the intervertebral joint: application to total disk replacement.

PubMed

O'Reilly, Oliver M; Metzger, Melodie F; Buckley, Jenni M; Moody, David A; Lotz, Jeffrey C

2009-08-01

The traditional method of establishing the stiffness matrix associated with an intervertebral joint is valid only for infinitesimal rotations, whereas the rotations featured in spinal motion are often finite. In the present paper, a new formulation of this stiffness matrix is presented, which is valid for finite rotations. This formulation uses Euler angles to parametrize the rotation, an associated basis, which is known as the dual Euler basis, to describe the moments, and it enables a characterization of the nonconservative nature of the joint caused by energy loss in the poroviscoelastic disk and ligamentous support structure. As an application of the formulation, the stiffness matrix of a motion segment is experimentally determined for the case of an intact intervertebral disk and compared with the matrices associated with the same segment after the insertion of a total disk replacement system. In this manner, the matrix is used to quantify the changes in the intervertebral kinetics associated with total disk replacements. As a result, this paper presents the first such characterization of the kinetics of a total disk replacement.

A comparative study on dynamic stiffness in typical finite element model and multi-body model of C6-C7 cervical spine segment.

PubMed

Wang, Yawei; Wang, Lizhen; Du, Chengfei; Mo, Zhongjun; Fan, Yubo

2016-06-01

In contrast to numerous researches on static or quasi-static stiffness of cervical spine segments, very few investigations on their dynamic stiffness were published. Currently, scale factors and estimated coefficients were usually used in multi-body models for including viscoelastic properties and damping effects, meanwhile viscoelastic properties of some tissues were unavailable for establishing finite element models. Because dynamic stiffness of cervical spine segments in these models were difficult to validate because of lacking in experimental data, we tried to gain some insights on current modeling methods through studying dynamic stiffness differences between these models. A finite element model and a multi-body model of C6-C7 segment were developed through using available material data and typical modeling technologies. These two models were validated with quasi-static response data of the C6-C7 cervical spine segment. Dynamic stiffness differences were investigated through controlling motions of C6 vertebrae at different rates and then comparing their reaction forces or moments. Validation results showed that both the finite element model and the multi-body model could generate reasonable responses under quasi-static loads, but the finite element segment model exhibited more nonlinear characters. Dynamic response investigations indicated that dynamic stiffness of this finite element model might be underestimated because of the absence of dynamic stiffen effect and damping effects of annulus fibrous, while representation of these effects also need to be improved in current multi-body model. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot

PubMed Central

Roy, Anindo; Bever, Christopher T.; Forrester, Larry W.; Macko, Richard F.; Hogan, Neville

2011-01-01

Our objective in this study was to assess passive mechanical stiffness in the ankle of chronic hemiparetic stroke survivors and to compare it with those of healthy young and older (age-matched) individuals. Given the importance of the ankle during locomotion, an accurate estimate of passive ankle stiffness would be valuable for locomotor rehabilitation, potentially providing a measure of recovery and a quantitative basis to design treatment protocols. Using a novel ankle robot, we characterized passive ankle stiffness both in sagittal and in frontal planes by applying perturbations to the ankle joint over the entire range of motion with subjects in a relaxed state. We found that passive stiffness of the affected ankle joint was significantly higher in chronic stroke survivors than in healthy adults of a similar cohort, both in the sagittal as well as frontal plane of movement, in three out of four directions tested with indistinguishable stiffness values in plantarflexion direction. Our findings are comparable to the literature, thus indicating its plausibility, and, to our knowledge, report for the first time passive stiffness in the frontal plane for persons with chronic stroke and older healthy adults. PMID:21346215

Structural Mechanics Solutions for Butt Joint Seals in Cold Climates

DOT National Transportation Integrated Search

1996-08-01

An effective, formed-in-place joint seal will respond with elastic or viscoelastic behavior over a reasonable design life to any large movement of the joint without adhesive or cohesive failure. For a given joint movement, seals with lower stiffness ...

Biomechanical Evaluation of a Prototype Foot/Ankle Prosthesis

PubMed Central

Quesada, P. M.; Pitkin, M.; Colvin, J.

2016-01-01

In this paper, we report on our pilot evaluation of a prototype foot/ankle prosthesis. This prototype has been designed and fabricated with the intention of providing decreased ankle joint stiffness during the middle portion of the stance phase of gait, and increased (i.e., more normal) knee range of motion during stance. Our evaluation involved fitting the existing prototype foot/ankle prosthesis, as well as a traditional solid ankle cushioned heel (SACH) foot, to an otherwise healthy volunteer with a below-knee (BK) amputation. We measured this individual’s lower extremity joint kinematics and kinetics during walking using a video motion analysis system and force platform. These measurements permitted direct comparison of prosthetic ankle joint stiffness and involved side knee joint motion, as well as prosthetic ankle joint moment and power. PMID:10779119

Reconstruction of equilibrium trajectories and joint stiffness patterns during single-joint voluntary movements under different instructions.

PubMed

Latash, M L

1994-01-01

A method for reconstructing joint compliant characteristics during voluntary movements was applied to the analysis of oscillatory and unidirectional elbow flexion movements. In different series, the subjects were given one of the following instructions: (1) do not intervene voluntarily; (2) keep the trajectory; (3) in cases of perturbations, return back to the starting position as quickly as possible (only during unidirectional movements). Under the instruction 'keep trajectory', the apparent joint stiffness increased by 50% to 250%. During oscillatory movements, this was accompanied by a decrease in the maximal difference between the actual and equilibrium joint trajectories and, in several cases, led to a change in the phase relation between the two trajectories. The coefficients of correlation between joint torque and angle were very high (commonly, over 0.9) under the 'do not intervene' instruction. They dropped to about 0.6 under the 'keep trajectory' and to about 0.3 under the 'return back' instructions. Under these two instructions, the low values of the coefficients of correlation did not allow reconstruction of segments of equilibrium trajectories and joint stiffness values in all the subjects. The results provide further support for the lambda-version of the equilibrium-point hypothesis and for using the instruction 'do not intervene voluntarily' to obtain reproducible time patterns of the central motor command.

Bee venom acupuncture for rheumatoid arthritis: a systematic review of randomised clinical trials.

PubMed

Lee, Ju Ah; Son, Mi Ju; Choi, Jiae; Jun, Ji Hee; Kim, Jong-In; Lee, Myeong Soo

2014-11-07

To assess the clinical evidence for bee venom acupuncture (BVA) for rheumatoid arthritis (RA). Systematic review of randomised controlled trials (RCTs). We searched 14 databases up to March 2014 without a language restriction. Patients with RA. BVA involved injecting purified, diluted BV into acupoints. We included trials on BVA used alone or in combination with a conventional therapy versus the conventional therapy alone. Morning stiffness, pain and joint swelling Erythrocyte sedimentation rate (ESR), C reactive protein (CRP), rheumatoid factor, the number of joints affected by RA and adverse effects likely related to RA. A total of 304 potentially relevant studies were identified; only one RCT met our inclusion criteria. Compared with placebo, BVA may more effectively improve joint pain, swollen joint counts, tender joint counts, ESR and CRP but was not shown to improve morning stiffness. There is low-quality evidence, based on one trial, that BVA can significantly reduce pain, morning stiffness, tender joint counts, swollen joint counts and improve the quality of life of patients with RA compared with placebo (normal saline injection) control. However, the number of trials, their quality and the total sample size were too low to draw firm conclusions. PROSPERO 2013: CRD42013005853. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Running Economy: Neuromuscular and Joint Stiffness Contributions in Trained Runners.

PubMed

Tam, Nicholas; Tucker, Ross; Santos-Concejero, Jordan; Prins, Danielle; Lamberts, Robert P

2018-05-29

It is debated whether running biomechanics make good predictors of running economy, with little known information about the neuromuscular and joint stiffness contributions to economical running gait. The aim of this study was to understand the relationship between certain neuromuscular and spatiotemporal biomechanical factors associated with running economy. Thirty trained runners performed a 6-minute constant-speed running set at 3.3 m∙s -1 , where oxygen consumption was assessed. Overground running trials were also performed at 3.3 m∙s -1 to assess kinematics, kinetics and muscle activity. Spatiotemporal gait variables, joint stiffness, pre-activation and stance phase muscle activity (gluteus medius; rectus femoris (RF); biceps femoris(BF); peroneus longus (PL); tibialis anterior (TA); gastrocnemius lateralis and medius (LG and MG) were variables of specific interest and thus determined. Additionally, pre-activation and ground contact of agonist:antagonist co-activation were calculated. More economical runners presented with short ground contact times (r=0.639, p<0.001) and greater strides frequencies (r=-0.630, p<0.001). Lower ankle and greater knee stiffness were associated with lower oxygen consumption (r=0.527, p=0.007 & r=0.384, p=0.043, respectively). Only LG:TA co-activation during stance were associated with lower oxygen cost of transport (r=0.672, p<0.0001). Greater muscle pre-activation and bi-articular muscle activity during stance were associated with more economical runners. Consequently, trained runners who exhibit greater neuromuscular activation prior to and during ground contact, in turn optimise spatiotemporal variables and joint stiffness, will be the most economical runners.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses.

PubMed

Kerkum, Yvette L; Houdijk, Han; Brehm, Merel-Anne; Buizer, Annemieke I; Kessels, Manon L C; Sterk, Arjan; van den Noort, Josien C; Harlaar, Jaap

2015-09-01

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion-extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of Passive Joint Stiffness on Proprioceptive Acuity in Individuals With Functional Instability of the Ankle.

PubMed

Marinho, Hellen Veloso Rocha; Amaral, Giovanna Mendes; de Souza Moreira, Bruno; Araújo, Vanessa Lara; Souza, Thales Rezende; Ocarino, Juliana Melo; da Fonseca, Sérgio Teixeira

2017-12-01

Study Design Controlled laboratory study, cross-sectional. Background Deficits in ankle proprioceptive acuity have been reported in persons with functional instability of the ankle. Passive stiffness has been proposed as a possible mechanism underlying proprioceptive acuity. Objective To compare proprioceptive acuity and passive ankle stiffness in persons with and without functional ankle instability, and to assess the influence of passive joint stiffness on proprioceptive acuity in persons with functional ankle instability. Methods A sample of 18 subjects with and 18 without complaints of functional ankle instability following lateral ankle sprain participated. An isokinetic dynamometer was used to compare motion perception threshold, passive position sense, and passive ankle stiffness between groups. To evaluate the influence of passive stiffness on proprioceptive acuity, individuals in the lateral functional ankle instability group were divided into 2 subgroups: "high" and "low" passive ankle stiffness. Results The functional ankle instability group exhibited increased motion perception threshold when compared with the corresponding limb of the control group. Between-group differences were not found for passive position sense and passive ankle stiffness. Those in the functional ankle instability group with higher passive ankle stiffness had smaller motion perception thresholds than those with lower passive ankle stiffness. Conclusion Unlike motion perception threshold, passive position sense is not affected by the presence of functional ankle instability. Passive ankle stiffness appears to influence proprioceptive acuity in persons with functional ankle instability. J Orthop Sports Phys Ther 2017;47(12):899-905. Epub 7 Oct 2017. doi:10.2519/jospt.2017.7030.

A Study of the Effect of Adhesive and Matrix Stiffnesses on the Axial, Normal, and Shear Stress Distributions of a Boron-epoxy Reinforced Composite Joint. M.S. Thesis

NASA Technical Reports Server (NTRS)

Howell, W. E.

1974-01-01

The mechanical properties of a symmetrical, eight-step, titanium-boron-epoxy joint are discussed. A study of the effect of adhesive and matrix stiffnesses on the axial, normal, and shear stress distributions was made using the finite element method. The NASA Structural Analysis Program (NASTRAN) was used for the analysis. The elastic modulus of the adhesive was varied from 345 MPa to 3100 MPa with the nominal value of 1030 MPa as a standard. The nominal values were used to analyze the stability of the joint. The elastic moduli were varied to determine their effect on the stresses in the joint.

Powered Upper Limb Orthosis Actuation System Based on Pneumatic Artificial Muscles

NASA Astrophysics Data System (ADS)

Chakarov, Dimitar; Veneva, Ivanka; Tsveov, Mihail; Venev, Pavel

2018-03-01

The actuation system of a powered upper limb orthosis is studied in the work. To create natural safety in the mutual "man-robot" interaction, an actuation system based on pneumatic artificial muscles (PAM) is selected. Experimentally obtained force/contraction diagrams for bundles, consisting of different number of muscles are shown in the paper. The pooling force and the stiffness of the pneumatic actuators is assessed as a function of the number of muscles in the bundle and the supply pressure. Joint motion and torque is achieved by antagonistic actions through pulleys, driven by bundles of pneumatic muscles. Joint stiffness and joint torques are determined on condition of a power balance, as a function of the joint position, pressure, number of muscles and muscles

Association of Vogt Koyanagi Harada Syndrome and Seronegative Rheumatoid Arthritis.

PubMed

Aydin, Teoman; Taspinar, Ozgur; Guneser, Meryem; Keskin, Yasar

2016-03-01

Vogt Koyanagi Harada (VKH) Syndrome is a rarely-seen multi-systemic, autoimmune and inflammatory disease. It observed frequently with neurologic, auditory and skin manifestations and characterized with bilateral, chronic and diffused granulomatous panuveitis. It generally affects women in young-adult period. A 57 year-old female patient applied to a special center one year ago with a complaint of decrease in the sight acuity of the right eye. The right eye was operated on with cataract diagnosis. Uveitis was developed firstly in the right eye and then in the left eye after the operation. Having complaints about uveitis, tinnitus and hear loss, the patient was diagnosed with VKH syndrome. The pains started to be felt in small hand joints and both of the two ankles. The pains were increasing especially in the mornings and during rest. The duration of morning stiffness was two hours in hand and foot joints. The patient had had lumbar pain with mechanic characteristic for five years. Being diagnosed with seronegative rheumatoid arthritis (RA), our case is presented because VKH syndrome is rarely seen in Turkey, and the joint findings are at the forefront.

Non-classical adhesive-bonded joints in practical aerospace construction

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1973-01-01

Solutions are derived for adhesive-bonded joints of non-classical geometries. Particular attention is given to bonded doublers and to selective reinforcement by unidirectional composites. Non-dimensionalized charts are presented for the efficiency limit imposed on the skin as the result of the eccentricity in the load path through the doubler. It is desirable to employ a relativly large doubler to minimize the effective eccentricity in the load path. The transfer stresses associated with selective reinforcement of metal structures by advanced composites are analyzed. Reinforcement of bolt holes in composites by bonded metal doublers is covered quantitatively. Also included is the adhesive joint analysis for shear flow in a multi-cell torque box, in which the bond on one angle becomes more critical sooner than those on the others, thereby restricting the strength to less than the total of each maximum strength when acting alone. Adhesive plasticity and adherend stiffness and thermal imbalances are included. A simple analysis/design technique of solution in terms of upper and lower bounds on an all-plastic adhesive analysis is introduced.

A commercialized dietary supplement alleviates joint pain in community adults: a double-blind, placebo-controlled community trial.

PubMed

Nieman, David C; Shanely, R Andrew; Luo, Beibei; Dew, Dustin; Meaney, Mary Pat; Sha, Wei

2013-11-25

The purpose of this study was to assess the effect of 8-weeks ingestion of a commercialized joint pain dietary supplement (Instaflex™ Joint Support, Direct Digital, Charlotte, NC) compared to placebo on joint pain, stiffness, and function in adults with self-reported joint pain. Instaflex™ is a joint pain supplement containing glucosamine sulfate, methylsufonlylmethane (MSM), white willow bark extract (15% salicin), ginger root concentrate, boswella serrata extract (65% boswellic acid), turmeric root extract, cayenne, and hyaluronic acid. Subjects included 100 men and women, ages 50-75 years, with a history (>3 months) of joint pain, and were randomized to Instaflex™ or placebo (3 colored gel capsules per day for 8 weeks, double-blind administration). Subjects agreed to avoid the use of non-steroidal anti-inflammatory drugs (NSAID) and all other medications and supplements targeted for joint pain. Primary outcome measures were obtained pre- and post-study and included joint pain severity, stiffness, and function (Western Ontario and McMaster Universities [WOMAC]), and secondary outcome measures included health-related quality of life (Short Form 36 or SF-36), systemic inflammation (serum C-reactive protein and 9 plasma cytokines), and physical function (6-minute walk test). Joint pain symptom severity was assessed bi-weekly using a 12-point Likert visual scale (12-VS). Joint pain severity was significantly reduced in Instaflex™ compared to placebo (8-week WOMAC, ↓37% versus ↓16%, respectively, interaction effect P = 0.025), with group differences using the 12-VS emerging by week 4 of the study (interaction effect, P = 0.0125). Improvements in ability to perform daily activities and stiffness scores in Instaflex™ compared to placebo were most evident for the 74% of subjects reporting knee pain (8-week WOMAC function score, ↓39% versus ↓14%, respectively, interaction effect P = 0.027; stiffness score, ↓30% versus ↓12%, respectively, interaction effect P = 0.081). Patterns of change in SF-36, systemic inflammation biomarkers, and the 6-minute walk test did not differ significantly between groups during the 8-week study Results from this randomized, double blind, placebo-controlled community trial support the use of the Instaflex™ dietary supplement in alleviating joint pain severity in middle-aged and older adults, with mitigation of difficulty performing daily activities most apparent in subjects with knee pain.

Improved Function and Reduced Pain after Swimming and Cycling Training in Patients with Osteoarthritis.

PubMed

Alkatan, Mohammed; Baker, Jeffrey R; Machin, Daniel R; Park, Wonil; Akkari, Amanda S; Pasha, Evan P; Tanaka, Hirofumi

2016-03-01

Arthritis and its associated joint pain act as significant barriers for adults attempting to perform land-based physical activity. Swimming can be an ideal form of exercise for patients with arthritis. Yet there is no information on the efficacy of regular swimming exercise involving patients with arthritis. The effect of a swimming exercise intervention on joint pain, stiffness, and physical function was evaluated in patients with osteoarthritis (OA). Using a randomized study design, 48 sedentary middle-aged and older adults with OA underwent 3 months of either swimming or cycling exercise training. Supervised exercise training was performed for 45 min/day, 3 days/week at 60-70% heart rate reserve for 12 weeks. The Western Ontario and McMaster Universities Arthritis Index was used to measure joint pain, stiffness, and physical limitation. After the exercise interventions, there were significant reductions in joint pain, stiffness, and physical limitation accompanied by increases in quality of life in both groups (all p < 0.05). Functional capacity as assessed by maximal handgrip strength, isokinetic knee extension and flexion power (15-30% increases), and the distance covered in the 6-min walk test increased (all p < 0.05) in both exercise groups. No differences were observed in the magnitude of improvements between swimming and cycling training. Regular swimming exercise reduced joint pain and stiffness associated with OA and improved muscle strength and functional capacity in middle-aged and older adults with OA. Additionally, the benefits of swimming exercise were similar to the more frequently prescribed land-based cycling training. clinicaltrials.gov NCT01836380.

Self-Myofascial Release: No Improvement of Functional Outcomes in 'Tight' Hamstrings.

PubMed

Morton, Robert W; Oikawa, Sara Y; Phillips, Stuart M; Devries, Michaela C; Mitchell, Cameron J

2016-07-01

Self-myofascial release (SMR) is a common exercise and therapeutic modality shown to induce acute improvements in joint range of motion (ROM) and recovery; however, no long-term studies have been conducted. Static stretching (SS) is the most common method used to increase joint ROM and decrease muscle stiffness. It was hypothesized that SMR paired with SS (SMR+SS) compared with SS alone over a 4-wk intervention would yield greater improvement in knee-extension ROM and hamstring stiffness. 19 men (22 ± 3 y) with bilateral reduced hamstring ROM had each of their legs randomly assigned to either an SMR+SS or an SS-only group. The intervention consisted of 4 repetitions of SS each for 45 s or the identical amount of SS preceded by 4 repetitions of SMR each for 60 s and was performed on the respective leg twice daily for 4 wk. Passive ROM, hamstring stiffness, rate of torque development (RTD), and maximum voluntary contraction (MVC) were assessed pre- and postintervention. Passive ROM (P < .001), RTD, and MVC (P < .05) all increased after the intervention. Hamstring stiffness toward end-ROM was reduced postintervention (P = .02). There were no differences between the intervention groups for any variable. The addition of SMR to SS did not enhance the efficacy of SS alone. SS increases joint ROM through a combination of decreased muscle stiffness and increased stretch tolerance.

Development of a mechatronic platform and validation of methods for estimating ankle stiffness during the stance phase of walking.

PubMed

Rouse, Elliott J; Hargrove, Levi J; Perreault, Eric J; Peshkin, Michael A; Kuiken, Todd A

2013-08-01

The mechanical properties of human joints (i.e., impedance) are constantly modulated to precisely govern human interaction with the environment. The estimation of these properties requires the displacement of the joint from its intended motion and a subsequent analysis to determine the relationship between the imposed perturbation and the resultant joint torque. There has been much investigation into the estimation of upper-extremity joint impedance during dynamic activities, yet the estimation of ankle impedance during walking has remained a challenge. This estimation is important for understanding how the mechanical properties of the human ankle are modulated during locomotion, and how those properties can be replicated in artificial prostheses designed to restore natural movement control. Here, we introduce a mechatronic platform designed to address the challenge of estimating the stiffness component of ankle impedance during walking, where stiffness denotes the static component of impedance. The system consists of a single degree of freedom mechatronic platform that is capable of perturbing the ankle during the stance phase of walking and measuring the response torque. Additionally, we estimate the platform's intrinsic inertial impedance using parallel linear filters and present a set of methods for estimating the impedance of the ankle from walking data. The methods were validated by comparing the experimentally determined estimates for the stiffness of a prosthetic foot to those measured from an independent testing machine. The parallel filters accurately estimated the mechatronic platform's inertial impedance, accounting for 96% of the variance, when averaged across channels and trials. Furthermore, our measurement system was found to yield reliable estimates of stiffness, which had an average error of only 5.4% (standard deviation: 0.7%) when measured at three time points within the stance phase of locomotion, and compared to the independently determined stiffness values of the prosthetic foot. The mechatronic system and methods proposed in this study are capable of accurately estimating ankle stiffness during the foot-flat region of stance phase. Future work will focus on the implementation of this validated system in estimating human ankle impedance during the stance phase of walking.

Experimental characterization and numerical simulation of riveted lap-shear joints using Rivet Element

NASA Astrophysics Data System (ADS)

Vivio, Francesco; Fanelli, Pierluigi; Ferracci, Michele

2018-03-01

In aeronautical and automotive industries the use of rivets for applications requiring several joining points is now very common. In spite of a very simple shape, a riveted junction has many contact surfaces and stress concentrations that make the local stiffness very difficult to be calculated. To overcome this difficulty, commonly finite element models with very dense meshes are performed for single joint analysis because the accuracy is crucial for a correct structural analysis. Anyhow, when several riveted joints are present, the simulation becomes computationally too heavy and usually significant restrictions to joint modelling are introduced, sacrificing the accuracy of local stiffness evaluation. In this paper, we tested the accuracy of a rivet finite element presented in previous works by the authors. The structural behaviour of a lap joint specimen with a rivet joining is simulated numerically and compared to experimental measurements. The Rivet Element, based on a closed-form solution of a reference theoretical model of the rivet joint, simulates local and overall stiffness of the junction combining high accuracy with low degrees of freedom contribution. In this paper the Rivet Element performances are compared to that of a FE non-linear model of the rivet, built with solid elements and dense mesh, and to experimental data. The promising results reported allow to consider the Rivet Element able to simulate, with a great accuracy, actual structures with several rivet connections.

Dwarfism

MedlinePlus

... dwarfism might have: cleft palate hand and ear differences hip dysplasia club feet severe curvature of the spine early deterioration of joints and joint stiffness potential hip and knee dislocation Complications From Spondyloepiphyseal Dysplasia ...

Adaptation of multijoint coordination during standing balance in healthy young and healthy old individuals

PubMed Central

Pasma, J. H.; Schouten, A. C.; Aarts, R. G. K. M.; Meskers, C. G. M.; Maier, A. B.; van der Kooij, H.

2015-01-01

Standing balance requires multijoint coordination between the ankles and hips. We investigated how humans adapt their multijoint coordination to adjust to various conditions and whether the adaptation differed between healthy young participants and healthy elderly. Balance was disturbed by push/pull rods, applying two continuous and independent force disturbances at the level of the hip and between the shoulder blades. In addition, external force fields were applied, represented by an external stiffness at the hip, either stabilizing or destabilizing the participants' balance. Multivariate closed-loop system-identification techniques were used to describe the neuromuscular control mechanisms by quantifying the corrective joint torques as a response to body sway, represented by frequency response functions (FRFs). Model fits on the FRFs resulted in an estimation of time delays, intrinsic stiffness, reflexive stiffness, and reflexive damping of both the ankle and hip joint. The elderly generated similar corrective joint torques but had reduced body sway compared with the young participants, corresponding to the increased FRF magnitude with age. When a stabilizing or destabilizing external force field was applied at the hip, both young and elderly participants adapted their multijoint coordination by lowering or respectively increasing their neuromuscular control actions around the ankles, expressed in a change of FRF magnitude. However, the elderly adapted less compared with the young participants. Model fits on the FRFs showed that elderly had higher intrinsic and reflexive stiffness of the ankle, together with higher time delays of the hip. Furthermore, the elderly adapted their reflexive stiffness around the ankle joint less compared with young participants. These results imply that elderly were stiffer and were less able to adapt to external force fields. PMID:26719084

Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

NASA Technical Reports Server (NTRS)

Newman, D. J.; Jackson, D. K.; Bloomberg, J. J.

1997-01-01

Astronauts exposed to the microgravity conditions encountered during space flight exhibit postural and gait instabilities upon return to earth that could impair critical postflight performance. The aim of the present study was to determine the effects of microgravity exposure on astronauts' performance of two-footed jump landings. Nine astronauts from several Space Shuttle missions were tested both preflight and postflight with a series of voluntary, two-footed downward hops from a 30-cm-high step. A video-based, three-dimensional motion-analysis system permitted calculation of body segment positions and joint angular displacements. Phase-plane plots of knee, hip, and ankle angular velocities compared with the corresponding joint angles were used to describe the lower limb kinematics during jump landings. The position of the whole-body center of mass (COM) was also estimated in the sagittal plane using an eight-segment body model. Four of nine subjects exhibited expanded phase-plane portraits postflight, with significant increases in peak joint flexion angles and flexion rates following space flight. In contrast, two subjects showed significant contractions of their phase-plane portraits postflight and three subjects showed insignificant overall changes after space flight. Analysis of the vertical COM motion generally supported the joint angle results. Subjects with expanded joint angle phase-plane portraits postflight exhibited larger downward deviations of the COM and longer times from impact to peak deflection, as well as lower upward recovery velocities. Subjects with postflight joint angle phase-plane contraction demonstrated opposite effects in the COM motion. The joint kinematics results indicated the existence of two contrasting response modes due to microgravity exposure. Most subjects exhibited "compliant" impact absorption postflight, consistent with decreased limb stiffness and damping, and a reduction in the bandwidth of the postural control system. Fewer subjects showed "stiff" behavior after space flight, where contractions in the phase-plane portraits pointed to an increase in control bandwidth. The changes appeared to result from adaptive modifications in the control of lower limb impedance. A simple 2nd-order model of the vertical COM motion indicated that changes in the effective vertical stiffness of the legs can predict key features of the postflight performance. Compliant responses may reflect inflight adaptation due to altered demands on the postural control system in microgravity, while stiff behavior may result from overcompensation postflight for the presumed reduction in limb stiffness inflight.

New insights on equid locomotor evolution from the lumbar region of fossil horses

PubMed Central

Jones, Katrina Elizabeth

2016-01-01

The specialization of equid limbs for cursoriality is a classic case of adaptive evolution, but the role of the axial skeleton in this famous transition is not well understood. Extant horses are extremely fast and efficient runners, which use a stiff-backed gallop with reduced bending of the lumbar region relative to other mammals. This study tests the hypothesis that stiff-backed running in horses evolved in response to evolutionary increases in body size by examining lumbar joint shape from a broad sample of fossil equids in a phylogenetic context. Lumbar joint shape scaling suggests that stability of the lumbar region does correlate with size through equid evolution. However, scaling effects were dampened in the posterior lumbar region, near the sacrum, which suggests strong selection for sagittal mobility in association with locomotor–respiratory coupling near the lumbosacral joint. I hypothesize that small-bodied fossil horses may have used a speed-dependent running gait, switching between stiff-backed and flex-backed galloping as speed increased. PMID:27122554

Changes in In Vivo Knee Loading with a Variable-Stiffness Intervention Shoe Correlate with Changes in the Knee Adduction Moment

PubMed Central

Erhart, Jennifer C.; Dyrby, Chris O.; D'Lima, Darryl D.; Colwell, Clifford W.; Andriacchi, Thomas P.

2010-01-01

External knee adduction moment can be reduced using footwear interventions, but the exact changes in in vivo medial joint loading remain unknown. An instrumented knee replacement was used to assess changes in in vivo medial joint loading in a single patient walking with a variable-stiffness intervention shoe. We hypothesized that during walking with a load modifying variable-stiffness shoe intervention: (1) the first peak knee adduction moment will be reduced compared to a subject's personal shoes; (2) the first peak in vivo medial contact force will be reduced compared to personal shoes; and (3) the reduction in knee adduction moment will be correlated with the reduction in medial contact force. The instrumentation included a motion capture system, force plate, and the instrumented knee prosthesis. The intervention shoe reduced the first peak knee adduction moment (13.3%, p=0.011) and medial compartment joint contact force (22%; p=0.008) compared to the personal shoe. The change in first peak knee adduction moment was significantly correlated with the change in first peak medial contact force (R2=0.67, p=0.007). Thus, for a single subject with a total knee prosthesis the variable-stiffness shoe reduces loading on the affected compartment of the joint. The reductions in the external knee adduction moment are indicative of reductions in in vivo medial compressive force with this intervention. PMID:20973058

Manipulation under Anesthesia for Stiffness after Total Knee Arthroplasty

PubMed Central

Yoo, Ju-Hyung; Oh, Jin-Cheol; Park, Sang-Hoon

2015-01-01

Purpose This study evaluated the incidence of manipulation under anesthesia (MUA) for stiffness after total knee arthroplasty (TKA) and the degree of joint motion recovery after MUA. Materials and Methods A total of 4,449 TKAs (2,973 patients) were performed between March 2000 and August 2014. Cases that underwent MUA for stiffness after TKA were reviewed. TKAs were performed using the conventional procedure in 329 cases and using the minimally invasive procedure in 4,120 cases. The preoperative range of joint motion, timing of manipulation, diagnosis and the range of joint motion before and after MUA were retrospectively investigated. Results MUA was carried out in 22 cases (16 patients), resulting in the incidence of 0.5%. The incidence after the conventional procedure was 1.2% and 0.4% after the minimally invasive procedure. In the manipulated knees, the preoperative range of motion (ROM) was 102.5°±26.7°, and the preoperative diagnosis was osteoarthritis in 19 cases, rheumatoid arthritis in two, and infection sequela in one. MUA was performed 4.7±3.0 weeks after TKA. The average ROM was 64.5°±13.5° before manipulation. At an average of 64.3±41.3 months after manipulation, the ROM was recovered to 113.4°±31.2°, which was an additional 49.9° improvement in flexion. Conclusions The satisfactory recovery of joint movement was achieved when MUA for stiffness was performed relatively early after TKA. PMID:26676186

Quasi-stiffness of the knee joint in flexion and extension during the golf swing.

PubMed

Choi, Ahnryul; Sim, Taeyong; Mun, Joung Hwan

2015-01-01

Biomechanical understanding of the knee joint during a golf swing is essential to improve performance and prevent injury. In this study, we quantified the flexion/extension angle and moment as the primary knee movement, and evaluated quasi-stiffness represented by moment-angle coupling in the knee joint. Eighteen skilled and 23 unskilled golfers participated in this study. Six infrared cameras and two force platforms were used to record a swing motion. The anatomical angle and moment were calculated from kinematic and kinetic models, and quasi-stiffness of the knee joint was determined as an instantaneous slope of moment-angle curves. The lead knee of the skilled group had decreased resistance duration compared with the unskilled group (P < 0.05), and the resistance duration of the lead knee was lower than that of the trail knee in the skilled group (P < 0.01). The lead knee of the skilled golfers had greater flexible excursion duration than the trail knee of the skilled golfers, and of both the lead and trail knees of the unskilled golfers. These results provide critical information for preventing knee injuries during a golf swing and developing rehabilitation strategies following surgery.

An Extended Passive Motion Paradigm for Human-Like Posture and Movement Planning in Redundant Manipulators

PubMed Central

Tommasino, Paolo; Campolo, Domenico

2017-01-01

A major challenge in robotics and computational neuroscience is relative to the posture/movement problem in presence of kinematic redundancy. We recently addressed this issue using a principled approach which, in conjunction with nonlinear inverse optimization, allowed capturing postural strategies such as Donders' law. In this work, after presenting this general model specifying it as an extension of the Passive Motion Paradigm, we show how, once fitted to capture experimental postural strategies, the model is actually able to also predict movements. More specifically, the passive motion paradigm embeds two main intrinsic components: joint damping and joint stiffness. In previous work we showed that joint stiffness is responsible for static postures and, in this sense, its parameters are regressed to fit to experimental postural strategies. Here, we show how joint damping, in particular its anisotropy, directly affects task-space movements. Rather than using damping parameters to fit a posteriori task-space motions, we make the a priori hypothesis that damping is proportional to stiffness. This remarkably allows a postural-fitted model to also capture dynamic performance such as curvature and hysteresis of task-space trajectories during wrist pointing tasks, confirming and extending previous findings in literature. PMID:29249954

Nervous system excitability and joint stiffness following short-term dynamic ankle immobilization.

PubMed

Stirling, Alyssa M; McBride, Jeffrey M; Merritt, Edward K; Needle, Alan R

2018-01-01

Joint immobilization has been demonstrated to modify neural excitability in subsets of healthy populations, leading to disinhibition of cortical and reflexive pathways. However, these findings may have limited clinical application as most models have investigated casting and rigid immobilization, while many musculoskeletal injuries often utilize dynamic immobilization devices such as boot immobilizers and pneumatic splints that allow for modified ambulation. We therefore aimed to determine the short-term effects of ambulation in ankle immobilization devices on nervous system excitability and stiffness in able-bodied individuals. A repeated-measures design was implemented where 12 healthy individuals were tested for cortical excitability to the ankle musculature using transcranial magnetic stimulation, reflexive excitability using the Hoffmann reflex, and ankle joint stiffness using arthrometry before and after 30min of ambulation with a boot immobilizer, pneumatic leg splint, or barefoot. Motor evoked potential (MEP), cortical silent period (CSP), H max to M max ratio, and ankle joint displacement were extracted as dependent variables. Results indicated that despite the novel motor demands of walking in immobilization devices, no significant changes in cortical excitability (F≥0.335, P≥0.169), reflexive excitability (F≥0.027, P≥0.083), or joint stiffness (F≥0.558, P≥0.169) occurred. These findings indicate that short-term ambulation in dynamic immobilization devices does not modify neural excitability despite forced constraints on the sensorimotor system. We may therefore conclude that modifications to neural excitability in previous immobilization models are mediated by long-term nervous system plasticity rather than acute mechanisms, and there appear to be no robust changes in corticomotor or spinal excitability acutely posed by ambulation with immobilization devices. Copyright © 2017 Elsevier B.V. All rights reserved.

Muscle short-range stiffness can be used to estimate the endpoint stiffness of the human arm

PubMed Central

Hu, Xiao; Murray, Wendy M.

2011-01-01

The mechanical properties of the human arm are regulated to maintain stability across many tasks. The static mechanics of the arm can be characterized by estimates of endpoint stiffness, considered especially relevant for the maintenance of posture. At a fixed posture, endpoint stiffness can be regulated by changes in muscle activation, but which activation-dependent muscle properties contribute to this global measure of limb mechanics remains unclear. We evaluated the role of muscle properties in the regulation of endpoint stiffness by incorporating scalable models of muscle stiffness into a three-dimensional musculoskeletal model of the human arm. Two classes of muscle models were tested: one characterizing short-range stiffness and two estimating stiffness from the slope of the force-length curve. All models were compared with previously collected experimental data describing how endpoint stiffness varies with changes in voluntary force. Importantly, muscle properties were not fit to the experimental data but scaled only by the geometry of individual muscles in the model. We found that force-dependent variations in endpoint stiffness were accurately described by the short-range stiffness of active arm muscles. Over the wide range of evaluated arm postures and voluntary forces, the musculoskeletal model incorporating short-range stiffness accounted for 98 ± 2, 91 ± 4, and 82 ± 12% of the variance in stiffness orientation, shape, and area, respectively, across all simulated subjects. In contrast, estimates based on muscle force-length curves were less accurate in all measures, especially stiffness area. These results suggest that muscle short-range stiffness is a major contributor to endpoint stiffness of the human arm. Furthermore, the developed model provides an important tool for assessing how the nervous system may regulate endpoint stiffness via changes in muscle activation. PMID:21289133

Forms of Arthritis

MedlinePlus

... stiffness, inflammation, swelling and, sometimes, destruction of joints. Gout — a form of arthritis that occurs when uric ... the joints. Some 2.1 million Americans have gout. Lupus — a form of arthritis, like rheumatoid arthritis, ...

Stiff, Strong Splice For A Composite Sandwich Structure

NASA Technical Reports Server (NTRS)

Schmaling, D.

1991-01-01

New type of splice for composite sandwich structure reduces peak shear stress in structure. Layers of alternating fiber orientation interposed between thin ears in adhesive joint. Developed for structural joint in spar of helicopter rotor blade, increases precision of control over thickness of adhesive at joint. Joint easy to make, requires no additional pieces, and adds little weight.

A commercialized dietary supplement alleviates joint pain in community adults: a double-blind, placebo-controlled community trial

PubMed Central

2013-01-01

Background The purpose of this study was to assess the effect of 8-weeks ingestion of a commercialized joint pain dietary supplement (InstaflexTM Joint Support, Direct Digital, Charlotte, NC) compared to placebo on joint pain, stiffness, and function in adults with self-reported joint pain. InstaflexTM is a joint pain supplement containing glucosamine sulfate, methylsufonlylmethane (MSM), white willow bark extract (15% salicin), ginger root concentrate, boswella serrata extract (65% boswellic acid), turmeric root extract, cayenne, and hyaluronic acid. Methods Subjects included 100 men and women, ages 50-75 years, with a history (>3 months) of joint pain, and were randomized to Instaflex™ or placebo (3 colored gel capsules per day for 8 weeks, double-blind administration). Subjects agreed to avoid the use of non-steroidal anti-inflammatory drugs (NSAID) and all other medications and supplements targeted for joint pain. Primary outcome measures were obtained pre- and post-study and included joint pain severity, stiffness, and function (Western Ontario and McMaster Universities [WOMAC]), and secondary outcome measures included health-related quality of life (Short Form 36 or SF-36), systemic inflammation (serum C-reactive protein and 9 plasma cytokines), and physical function (6-minute walk test). Joint pain symptom severity was assessed bi-weekly using a 12-point Likert visual scale (12-VS). Results Joint pain severity was significantly reduced in Instaflex™ compared to placebo (8-week WOMAC, ↓37% versus ↓16%, respectively, interaction effect P = 0.025), with group differences using the 12-VS emerging by week 4 of the study (interaction effect, P = 0.0125). Improvements in ability to perform daily activities and stiffness scores in Instaflex™ compared to placebo were most evident for the 74% of subjects reporting knee pain (8-week WOMAC function score, ↓39% versus ↓14%, respectively, interaction effect P = 0.027; stiffness score, ↓30% versus ↓12%, respectively, interaction effect P = 0.081). Patterns of change in SF-36, systemic inflammation biomarkers, and the 6-minute walk test did not differ significantly between groups during the 8-week study Conclusions Results from this randomized, double blind, placebo-controlled community trial support the use of the Instaflex™ dietary supplement in alleviating joint pain severity in middle-aged and older adults, with mitigation of difficulty performing daily activities most apparent in subjects with knee pain. Trial registration ClinicalTrials.gov Identifier: NCT01956500 PMID:24274358

The Relationship Between Early-Stage Knee Osteoarthritis and Lower-Extremity Alignment, Joint Laxity, and Subjective Scores of Pain, Stiffness, and Function.

PubMed

Hicks-Little, Charlie A; Peindl, Richard D; Hubbard-Turner, Tricia J; Cordova, Mitchell L

2016-08-01

Knee osteoarthritis (OA) is a debilitating disease that affects an estimated 27 million Americans. Changes in lower-extremity alignment and joint laxity have been found to redistribute the medial and/or lateral loads at the joint. However, the effect that changes in anteroposterior knee-joint laxity have on lower-extremity alignment and function in individuals with knee OA remains unclear. To examine anteroposterior knee-joint laxity, lower-extremity alignment, and subjective pain, stiffness, and function scores in individuals with early-stage knee OA and matched controls and to determine if a relationship exists among these measures. Case control. Sports-medicine research laboratory. 18 participants with knee OA and 18 healthy matched controls. Participants completed the Western Ontario McMaster (WOMAC) osteoarthritis questionnaire and were tested for total anteroposterior knee-joint laxity (A-P) and knee-joint alignment (ALIGN). WOMAC scores, A-P (mm), and ALIGN (°). A significant multivariate main effect for group (Wilks' Λ = 0.30, F7,26 = 8.58, P < .0001) was found. Knee-OA participants differed in WOMAC scores (P < .0001) but did not differ from healthy controls on ALIGN (P = .49) or total A-P (P = .66). No significant relationships were identified among main outcome measures. These data demonstrate that participants with early-stage knee OA had worse pain, stiffness, and functional outcome scores than the matched controls; however, ALIGN and A-P were no different. There was no association identified among participants' subjective scores, ALIGN, or A-P measures in this study.

Effects of hamstring stretching on passive muscle stiffness vary between hip flexion and knee extension maneuvers.

PubMed

Miyamoto, N; Hirata, K; Kanehisa, H

2017-01-01

The purpose of this study was to examine whether the effects of hamstring stretching on the passive stiffness of each of the long head of the biceps femoris (BFl), semitendinosus (ST), and semimembranosus (SM) vary between passive knee extension and hip flexion stretching maneuvers. In 12 male subjects, before and after five sets of 90 s static stretching, passive lengthening measurements where knee or hip joint was passively rotated to the maximal range of motion (ROM) were performed. During the passive lengthening, shear modulus of each muscle was measured by ultrasound shear wave elastography. Both stretching maneuvers significantly increased maximal ROM and decreased passive torque at a given joint angle. Passive knee extension stretching maneuver significantly reduced shear modulus at a given knee joint angle in all of BFl, ST, and SM. In contrast, the stretching effect by passive hip flexion maneuver was significant only in ST and SM. The present findings indicate that the effects of hamstring stretching on individual passive muscles' stiffness vary between passive knee extension and hip flexion stretching maneuvers. In terms of reducing the muscle stiffness of BFl, stretching of the hamstring should be performed by passive knee extension rather than hip flexion. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Biomechanical constraints on the feedforward regulation of endpoint stiffness.

PubMed

Hu, Xiao; Murray, Wendy M; Perreault, Eric J

2012-10-01

Although many daily tasks tend to destabilize arm posture, it is still possible to have stable interactions with the environment by regulating the multijoint mechanics of the arm in a task-appropriate manner. For postural tasks, this regulation involves the appropriate control of endpoint stiffness, which represents the stiffness of the arm at the hand. Although experimental studies have been used to evaluate endpoint stiffness control, including the orientation of maximal stiffness, the underlying neural strategies remain unknown. Specifically, the relative importance of feedforward and feedback mechanisms has yet to be determined due to the difficulty separately identifying the contributions of these mechanisms in human experiments. This study used a previously validated three-dimensional musculoskeletal model of the arm to quantify the degree to which the orientation of maximal endpoint stiffness could be changed using only steady-state muscle activations, used to represent feedforward motor commands. Our hypothesis was that the feedforward control of endpoint stiffness orientation would be significantly constrained by the biomechanical properties of the musculoskeletal system. Our results supported this hypothesis, demonstrating substantial biomechanical constraints on the ability to regulate endpoint stiffness throughout the workspace. The ability to regulate stiffness orientation was further constrained by additional task requirements, such as the need to support the arm against gravity or exert forces on the environment. Together, these results bound the degree to which slowly varying feedforward motor commands can be used to regulate the orientation of maximum arm stiffness and provide a context for better understanding conditions in which feedback control may be needed.

Is statin use associated with new joint-related symptoms, physical function, and quality of life? Results from two population-based cohorts of women.

PubMed

Peeters, Geeske; Tett, Susan E; Conaghan, Philip G; Mishra, Gita D; Dobson, Annette J

2015-01-01

Previous studies have suggested that statins may prevent development of osteoarthritis and have antiinflammatory effects. Our aim was to examine the associations between statin use and patient-reported joint symptoms in 2 large cohorts of middle-aged and older women. Data were from 6,966 middle-aged (born 1946-1951) and 4,806 older (born 1921-1926) participants in the Australian Longitudinal Study on Women's Health who completed surveys from 2001 to 2011, including questions about joint pain/stiffness, physical functioning, and self-rated health (SRH). Administrative pharmaceutical data were used to classify participants according to statin use, cumulative volume of statin use, and type of drug. Associations between statin use and newly reported symptoms were analyzed using logistic regression with generalized estimating equations to account for repeated measures. A total of 2,096 (31.3%) of the middle-aged women and 2,473 (51.5%) of the older women were classified as statin users. After adjustment for confounders, statin use in middle-aged women was weakly associated with poor physical functioning (odds ratio [OR] 1.29, 99% confidence interval [99% CI] 1.07-1.55) and poor SRH (OR 1.35, 99% CI 1.13-1.61), but not with new joint pain/stiffness (OR 1.09, 99% CI 0.88-1.34). No dose-response relationships were found. Pravastatin and atorvastatin were associated with poor physical functioning, while atorvastatin was also associated with poor SRH. Associations found in older women were mostly explained by confounders. This large study did not demonstrate an association between statin use and reduced onset of joint pain/stiffness. Associations between statin use and poor physical functioning and poor SRH may be explained by factors other than joint pain/stiffness, e.g., muscle pain. Copyright © 2015 by the American College of Rheumatology.

Mechanisms of Shoulder Range of Motion Deficits in Asymptomatic Baseball Players.

PubMed

Bailey, Lane B; Shanley, Ellen; Hawkins, Richard; Beattie, Paul F; Fritz, Stacy; Kwartowitz, David; Thigpen, Charles A

2015-11-01

Shoulder range of motion (ROM) deficits have been identified as injury risk factors among baseball athletes. Despite the knowledge surrounding these risk factors, there is a lack of consensus regarding the specific tissues responsible for these deficits in ROM. The purpose of this study was to elucidate the primary mechanisms of posterior shoulder tightness (capsular, musculotendinous, bony) by examining the tissue responses that occur with the application of an acute intervention in baseball players with ROM deficits. The hypothesis was that posterior rotator cuff stiffness, not glenohumeral joint mobility, would be primarily responsible for ROM gains observed within an acute treatment setting. Controlled laboratory study. Through use of ultrasound elastography, electromagnetic motion analysis, and ultrasound imaging, posterior rotator cuff stiffness, glenohumeral joint translation, and humeral torsion were examined in 60 asymptomatic baseball players (age, mean ± SD, 19 ± 2 years) with shoulder ROM deficits. Tissue mechanisms were examined concurrently, with the ROM gains elicited by an acute application of instrument-assisted soft tissue mobilization plus self-stretching (n = 30) versus self-stretching only (n = 30). Separate 3-way analyses of variance (group × arm × time) and linear regression analyses were used to determine the treatment effects and relationships between tissue mechanisms and ROM gains. ROM gains were associated with decreases in rotator cuff stiffness (internal rotation: r = 0.35, P = .034; horizontal adduction: r = 0.44, P = .008) and increased humeral retrotorsion (internal rotation: r = -0.35, P = .034), not joint translation (P > .05). Players receiving instrument-assisted soft tissue mobilization plus stretching displayed greater shoulder ROM gains (internal rotation, +5° ± 2° [P = .010]; total arc of motion, +8° ± 6° [P = .010]; horizontal adduction, +7° ± 2° [P = .004]; and decreased posterior rotator cuff stiffness, -0.2 ± 0.3 kPa [P = .050]) compared with players receiving self-stretching alone. Decreases in rotator cuff stiffness were associated with acute ROM gains in baseball players. The study results show that changes in rotator cuff stiffness, not glenohumeral joint mobility or humeral torsion, are most likely associated with the ROM deficits observed in adolescent baseball players. Reducing rotator cuff stiffness may be beneficial in improving the ROM deficits associated with injury risk in overhead athletes. © 2015 The Author(s).

Molecular mechanisms underlying osteoarthritis development: Notch and NF-κB.

PubMed

Saito, Taku; Tanaka, Sakae

2017-05-15

Osteoarthritis (OA) is a multi-factorial and highly prevalent joint disorder worldwide. Since the establishment of murine surgical knee OA models in 2005, many of the key molecules and signalling pathways responsible for OA development have been identified. Here we review the roles of two multi-functional signalling pathways in OA development: Notch and nuclear factor kappa-light-chain-enhancer of activated B cells. Previous studies have identified various aspects of articular chondrocyte regulation by these pathways. However, comprehensive understanding of the molecular networks regulating articular cartilage homeostasis and OA pathogenesis is needed.

X-ray motion analysis of the vertebral column during the startle response in striped bass, Morone saxatilis.

PubMed

Nowroozi, B N; Brainerd, E L

2013-08-01

Whole-body stiffness has a substantial impact on propulsive wave speed during axial undulatory locomotion in fishes. The connective tissues of the vertebral column may contribute to body stiffness, but without mechanical and kinematic analysis it is unclear whether the in vivo range of motion of intervertebral joints (IVJs) is great enough to stress IVJ tissues, thus generating stiffness. The present study used 2D videoradiography and 3D X-ray reconstruction of moving morphology (XROMM) to quantify vertebral kinematics during the startle response in striped bass (Morone saxatilis). X-ray video revealed two distinct patterns of bending: pattern I begins in the abdominal region and then proceeds to maximum IVJ angles in the caudal region, whereas pattern II begins in the cervical region and proceeds to maximum IVJ angles in the abdominal and then the caudal joints. In pattern II bends, the cervical joints exhibit a greater in vivo range of motion than previously reported in other species. XROMM analysis of caudal IVJs suggests primarily lateral bending: mean axial and dorsoventral rotations were less than 2 deg and inconsistent across 51 sequences analyzed from five individuals, whereas mean maximum lateral bending angles were 10.4±3.57 deg. These angles, combined with previous investigations of mechanical properties, reveal that the maximum angles all occur within the neutral zone of bending, indicating that little stress is experienced about the joint. This suggests that the IVJs of striped bass are quite compliant and likely do not contribute significantly to whole-body stiffness or elastic recoil during swimming in vivo.

Control of paraplegic ankle joint stiffness using FES while standing.

PubMed

Hunt, K J; Gollee, H; Jaime, R P

2001-10-01

The goal of this work was to investigate the feasibility of ankle stiffness control using functional electrical stimulation (FES) while standing, as relevant to the development of feedback systems for balance control in paraplegia. The work was carried out using apparatus in which the subject stands with all joints above the ankles braced, and where ankle moment is provided via FES of the ankle flexor and extensor muscles. A feedback control strategy for ankle stiffness control is proposed in which the ankle moment is controlled to a reference value equal to the product of the desired stiffness and the measured ankle angle. Two subjects participated in the study: one neurologically-intact person, and one paraplegic person with a complete thoracic spinal cord lesion. The results show that during forward-leaning postures, when the plantarflexor muscles are stimulated, relatively high ankle moments of up to 60 Nm can be generated and accurate moment tracking is achieved. As a consequence, ankle stiffness is close to the desired value. During backward lean, on the other hand, the dorsiflexor muscles are stimulated. These muscles are relatively weak and only modest ankle moments of up to around 15 Nm can be produced. As a result, dorsiflexor stimulation readily saturates giving poor stiffness control. It was further observed that when the desired stiffness is higher more external force has to be applied to perturb the body away from the neutral (upright) position. We conclude that: (i) accurate ankle stiffness control, up to the fundamental strength limits of the muscles, can be achieved with controlled FES; (ii) ankle stiffness control using FES in paraplegia has the potential to ease the task of stabilising upright posture by application of additional upper-body forces.

The effects of prosthetic foot stiffness on transtibial amputee walking mechanics and balance control during turning.

PubMed

Shell, Courtney E; Segal, Ava D; Klute, Glenn K; Neptune, Richard R

2017-11-01

Little evidence exists regarding how prosthesis design characteristics affect performance in tasks that challenge mediolateral balance such as turning. This study assesses the influence of prosthetic foot stiffness on amputee walking mechanics and balance control during a continuous turning task. Three-dimensional kinematic and kinetic data were collected from eight unilateral transtibial amputees as they walked overground at self-selected speed clockwise and counterclockwise around a 1-meter circle and along a straight line. Subjects performed the walking tasks wearing three different ankle-foot prostheses that spanned a range of sagittal- and coronal-plane stiffness levels. A decrease in stiffness increased residual ankle dorsiflexion (10-13°), caused smaller adaptations (<5°) in proximal joint angles, decreased residual and increased intact limb body support, increased residual limb propulsion and increased intact limb braking for all tasks. While changes in sagittal-plane joint work due to decreased stiffness were generally consistent across tasks, effects on coronal-plane hip work were task-dependent. When the residual limb was on the inside of the turn and during straight-line walking, coronal-plane hip work increased and coronal-plane peak-to-peak range of whole-body angular momentum decreased with decreased stiffness. Changes in sagittal-plane kinematics and kinetics were similar to those previously observed in straight-line walking. Mediolateral balance improved with decreased stiffness, but adaptations in coronal-plane angles, work and ground reaction force impulses were less systematic than those in sagittal-plane measures. Effects of stiffness varied with the residual limb inside versus outside the turn, which suggests that actively adjusting stiffness to turn direction may be beneficial. Copyright © 2017 Elsevier Ltd. All rights reserved.

Juvenile Arthritis

MedlinePlus

Juvenile arthritis (JA) is arthritis that happens in children. It causes joint swelling, pain, stiffness, and loss of motion. It can affect any joint, but ... of JA that children get is juvenile idiopathic arthritis. There are several other forms of arthritis affecting ...

Evaluation of Silicone as an Artificial Lubricant in Osteoarthrotic Joints

PubMed Central

Wright, V.; Haslock, D. I.; Dowson, D.; Seller, P. C.; Reeves, B.

1971-01-01

Silicone 300 has been evaluated as an artificial lubricant in osteoarthrotic joints by means of a pilot study in five inpatients and a control trial of 25 outpatients with 40 osteoarthrotic knees. Sequential analysis showed a significant benefit from saline compared with silicone at one week follow-up and no significant difference at one month. Measurement of stiffness with a knee arthrograph showed no difference in reduction of stiffness between the two substances. In a study of 18 rabbits there was no evidence that silicone was retained in the joint cavity for longer than 48 hours. There was a failure of clearance of iodinated serum albumin for as long as three to four days after the injection of silicone, suggesting some obstruction to lymphatic outflow. Experimentally produced cartilaginous defects did not heal quicker with the injection of silicone into the joint. PMID:5575973

Associations between lower extremity muscle mass and multiplanar knee laxity and stiffness: a potential explanation for sex differences in frontal and transverse plane knee laxity.

PubMed

Shultz, Sandra J; Pye, Michele L; Montgomery, Melissa M; Schmitz, Randy J

2012-12-01

Compared with men, women have disproportionally greater frontal (varus-valgus) and transverse (internal-external) plane laxity and lower stiffness, despite having similar sagittal (anterior-posterior) plane laxity and stiffness. While the underlying cause is unclear, the amount of lower extremity lean mass (LELM) may be a contributing factor. Lower extremity lean mass would be a stronger predictor of frontal and transverse plane laxity and incremental stiffness than the sagittal plane. Associations between LELM and stiffness would be stronger at lower force increments. Descriptive laboratory study. Sixty-three women and 30 men with no history of ligament injury were measured for knee laxity and incremental stiffness in the sagittal (-90- to 130-N posterior-to-anterior directed loads), frontal (±10-N·m varus-valgus torques), and transverse (±5-N·m internal-external rotation torques) planes and underwent dual-energy X-ray absorptiometry scans to measure LELM. Linear regressions examined the extent to which LELM predicted each laxity and stiffness value, while also accounting for a person's sex. Females (vs males) had greater laxity and less stiffness in the frontal and transverse planes but not the sagittal plane. Lower extremity lean mass was a poor predictor of sagittal laxity and stiffness (R (2) range = .021-.081; P > .06) but was a stronger predictor of frontal (R (2) range = .215-.567; P < .01) and transverse (R (2) range = .224-.356; P < .01) plane laxity and stiffness. Associations were stronger for low (R (2) = .495-.504) versus high (R (2) = .215-.435) frontal plane stiffness but were similar for low (R (2) = .233-.293) versus high (R (2) = .224-.356) transverse plane stiffness. Once we accounted for a person's LELM, sex had little effect on laxity and stiffness (change in R (2) after removal = .01-.08; P = .027-.797). Less LELM was associated with greater laxity and less stiffness in frontal and transverse planes, which may contribute to the disproportionally higher laxities and reduced stiffnesses observed in females in these planes. Frontal and transverse plane laxity and stiffness may be modifiable through strength training interventions that promote changes in muscle characteristics (eg, muscle cross-sectional area, stiffness) that may contribute to static knee joint stability, thus dynamic joint stability during sport activity.

The influence of landing mat composition on ankle injury risk during a gymnastic landing: a biomechanical quantification.

PubMed

Xiao, Xiaofei; Hao, Weiya; Li, Xuhong; Wan, Bingjun; Shan, Gongbing

2017-01-01

About 70% injury of gymnasts happened during landing - an interaction between gymnast and landing mat. The most injured joint is the ankle. The current study examined the effect of mechanical properties of landing mat on ankle loading with aims to identify means of decreasing the risk of ankle injury. Gymnastic skill - salto backward stretched with 3/2 twist was captured by two high-speed camcorders and digitized by using SIMI-Motion software. A subject-specific, 14-segment rigid-body model and a mechanical landing-mat model were built using BRG.LifeMODTM. The landings were simulated with varied landing-mat mechanical properties (i.e., stiffness, dampness and friction coefficients). Real landing performance could be accurately reproduced by the model. The simulations revealed that the ankle angle was relatively sensitive to stiffness and dampness of the landing mat, the ankle loading rate increased 26% when the stiffness was increased by 30%, and the changing of dampness had notable effect on horizontal ground reaction force and foot velocity. Further, the peak joint-reaction force and joint torque were more sensitive to friction than to stiffness and dampness of landing mat. Finally, ankle muscles would dissipate about twice energy (189%) when the friction was increased by 30%. Loads to ankles during landing would increase as the stiffness and dampness of the landing mat increase. Yet, increasing friction would cause a substantial rise of the ankle internal loads. As such, the friction should be a key factor influencing the risk of injury. Unfortunately, this key factor has rarely attracted attention in practice.

Torsional stiffness after subtalar arthrodesis using second generation headless compression screws: Biomechanical comparison of 2-screw and 3-screw fixation.

PubMed

Riedl, Markus; Glisson, Richard R; Matsumoto, Takumi; Hofstaetter, Stefan G; Easley, Mark E

2017-06-01

Subtalar joint arthrodesis is a common operative treatment for symptomatic subtalar arthrosis. Because excessive relative motion between the talus and calcaneus can delay or prohibit fusion, fixation should be optimized, particularly in patients at risk for subtalar arthrodesis nonunion. Tapered, fully-threaded, variable pitch screws are gaining popularity for this application, but the mechanical properties of joints fixed with these screws have not been characterized completely. We quantified the torsion resistance of 2-screw and 3-screw subtalar joint fixation using this type of screw. Ten pairs of cadaveric subtalar joints were prepared for arthrodesis and fixed using Acutrak 2-7.5 screws. One specimen from each pair was fixed with two diverging posterior screws, and the contralateral joint was fixed using two posterior screws and a third screw directed through the anterior calcaneus into the talar neck. Internal and external torsional loads were applied and joint rotation and torsional stiffness were measured at two torque levels. Internal rotation was significantly less in specimens fixed with three screws. No difference was detectable between 2-screw and 3-screw fixation in external rotation or torsional stiffness in either rotation direction. Both 2-screw and 3-screw fixation exhibited torsion resistance surpassing that reported previously for subtalar joints fixed with two diverging conventional lag screws. Performance of the tapered, fully threaded, variable pitch screws exceeded that of conventional lag screws regardless of whether two or three screws were used. Additional resistance to internal rotation afforded by a third screw placed anteriorly may offer some advantage in patients at risk for nonunion. Copyright © 2017. Published by Elsevier Ltd.

Prevention of the Post-traumatic Fibrotic Response in Joints

DTIC Science & Technology

2014-10-01

The American journal of forensic medicine and pathology . 1988; 9(4):310-2. 14 APPENDICES: An abstract submitted for the ORS conference...clinical problem of posttraumatic joint stiffness, a pathology that reduces the range of motion (ROM) of injured joints and contributes to the...development of osteoarthritis. The fundamental hypothesis that drives the current study is that pathological fibrotic response of injured joint tissues

Age and Sex Effects on the Active Stiffness of Vastus Intermedius under Isometric Contraction

PubMed Central

Wang, Cong-Zhi; Guo, Jing-Yi; Li, Tian-Jie; Shi, Wenxiu; Zheng, Yong-Ping

2017-01-01

Previously, a novel technique was proposed to quantify the relationship between the muscle stiffness and its nonfatigue contraction intensity. The method extended the measured range of isometric contraction to 100% maximum voluntary contraction (MVC) using an ultrasonic shear wave measurement setup. Yet, it has not been revealed how this relationship could be affected by factors like age or sex. To clarify these questions, vastus intermedius (VI) stiffness of 40 healthy subjects was assessed under 11 step levels of isometric contraction. The subjects were divided into four groups: young males, young females, elderly males, and elderly females (n = 10 for each). In a relaxed state, no significant difference was observed between the male and female subjects (p = 0.156) nor between the young and elderly subjects (p = 0.221). However, when performing isometric contraction, the VI stiffness of males was found to be significantly higher than that of females at the same level (p < 0.001), and that of the young was higher than the elderly (p < 0.001). Meanwhile, for two knee joint angles used, the stiffness measured at a 90° knee joint angle was always significantly larger than that measured at 60° (p < 0.001). Recognizing the active muscle stiffness of VI contributes to body stability, and these results may provide insight into the age and sex bias in musculoskeletal studies, such as those on fall risks. PMID:28473990

Treatment with Ruta graveolens 5CH and Rhus toxicodendron 9CH may reduce joint pain and stiffness linked to aromatase inhibitors in women with early breast cancer: results of a pilot observational study.

PubMed

Karp, Jean-Claude; Sanchez, Carole; Guilbert, Philippe; Mina, William; Demonceaux, Antoine; Curé, Hervé

2016-11-01

To determine the possible effect of two homeopathic medicines, Ruta graveolens 5CH and Rhus toxicodendron 9CH, in the prevention of aromatase inhibitor (AI) associated joint pain and/or stiffness in women with early, hormone-receptor positive, breast cancer. This prospective, unrandomized observational study was carried out between April and October 2014. Women were recruited in two groups, according to which of the two study centres they attended: one receiving homeopathy in addition to standard treatment (group H) and a control group, receiving standard treatment (group C). All women were treated with an AI. In addition, women in group H also took Ruta graveolens 5CH and Rhus toxicodendron 9CH (5 granules, twice a day) up to 7 days before starting AI treatment. The homeopathic medicines were continued for 3 months. Demographic and clinical data were recorded using a self-assessment questionnaire at inclusion (T0) and 3 months (T3). Primary evaluation criteria were the evolution of scores for joint pain and stiffness, the impact of pain on sleep and analgesic consumption in the two groups after 3 months of treatment. Forty patients (mean age 64.9±8.1 years) were recruited, 20 in each group. Two-thirds of the patients had joint pain before starting AI treatment. There was a significant difference in the evolution of mean composite pain score between T0 and T3 in the two groups (-1.3 in group H vs. +3.4 in group C; p=0.0001). The individual components of the pain score (frequency, intensity and number of sites of pain) also decreased significantly in group H. Nine patients in group C (45%) vs. 1 (5%) in group H increased their analgesic consumption between T0 and T3 (p=0.0076). After 3 months of treatment, joint pain had a worse impact on sleep in patients in group C (35% vs. 0% of patients; p=0.0083). The differences observed in the evolution of morning and daytime stiffness between the two groups were smaller (p=0.053 and p=0.33, respectively), with the exception of time necessary for the disappearance of morning stiffness which was greater in group C (37.7±23.0 vs. 17.9±20.1 min; p=0.0173). These preliminary results suggest that treatment with Ruta graveolens 5CH and Rhus toxicodendron 9CH may decrease joint pain/stiffness in breast cancer patients treated with AIs. A larger-scale randomized study is required to confirm these results. Copyright © 2016 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

Geomechanical Response of Jointed Caprock During CO2 Geological Sequestration

NASA Astrophysics Data System (ADS)

Newell, P.; Martinez, M. J.; Bishop, J. E.

2014-12-01

Geological sequestration of CO2 refers to the injection of supercritical CO2 into deep reservoirs trapped beneath a low-permeability caprock formation. Maintaining caprock integrity during the injection process is the most important factor for a successful injection. In this work we evaluate the potential for jointed caprock during injection scenarios using coupled three-dimensional multiphase flow and geomechanics modeling. Evaluation of jointed/fractured caprock systems is of particular concern to CO2 sequestration because creation or reactivation of joints (mechanical damage) can lead to enhanced pathways for leakage. In this work, we use an equivalent continuum approach to account for the joints within the caprock. Joint's aperture and non-linear stiffness of the caprock will be updated dynamically based on the effective normal stress. Effective permeability field will be updated based on the joints' aperture creating an anisotropic permeability field throughout the caprock. This feature would add another coupling between the solid and fluid in addition to basic Terzaghi's effective stress concept. In this study, we evaluate the impact of the joint's orientation and geometry of caprock and reservoir layers on geomechanical response of the CO2 geological systems. This work is supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Quantifying anti-gravity torques for the design of a powered exoskeleton.

PubMed

Ragonesi, Daniel; Agrawal, Sunil K; Sample, Whitney; Rahman, Tariq

2013-03-01

Designing an upper extremity exoskeleton for people with arm weakness requires knowledge of the joint torques due to gravity and joint stiffness, as well as, active residual force capabilities of users. The objective of this research paper is to describe the characteristics of the upper limb of children with upper limb impairment. This paper describes the experimental measurements of the torque on the upper limb due to gravity and joint stiffness of three groups of subjects: able-bodied adults, able-bodied children, and children with neuromuscular disabilities. The experiment involves moving the arm to various positions in the sagittal plane and measuring the resultant force at the forearm. This force is then converted to torques at the elbow and shoulder. These data are compared to a two-link lumped mass model based on anthropomorphic data. Results show that the torques based on anthropometry deviate from experimentally measured torques as the arm goes through the range. Subjects with disabilities also maximally pushed and pulled against the force sensor to measure maximum strength as a function of arm orientation. For all subjects, the maximum voluntary applied torque at the shoulder and elbow in the sagittal plane was found to be lower than gravity torques throughout the disabled subjects' range of motion. This experiment informs designers of upper limb orthoses on the contribution of passive human joint torques due to gravity and joint stiffness and the strength capability of targeted users.

Preliminary Comparison of Multi-scale and Multi-model Direct Inversion Algorithms for 3T MR Elastography.

PubMed

Yoshimitsu, Kengo; Shinagawa, Yoshinobu; Mitsufuji, Toshimichi; Mutoh, Emi; Urakawa, Hiroshi; Sakamoto, Keiko; Fujimitsu, Ritsuko; Takano, Koichi

2017-01-10

To elucidate whether any differences are present in the stiffness map obtained with a multiscale direct inversion algorithm (MSDI) vs that with a multimodel direct inversion algorithm (MMDI), both qualitatively and quantitatively. The MR elastography (MRE) data of 37 consecutive patients who underwent liver MR elastography between September and October 2014 were retrospectively analyzed by using both MSDI and MMDI. Two radiologists qualitatively assessed the stiffness maps for the image quality in consensus, and the measured liver stiffness and measurable areas were quantitatively compared between MSDI and MMDI. MMDI provided a stiffness map of better image quality, with comparable or slightly less artifacts. Measurable areas by MMDI (43.7 ± 17.8 cm 2 ) was larger than that by MSDI (37.5 ± 14.7 cm 2 ) (P < 0.05). Liver stiffness measured by MMDI (4.51 ± 2.32 kPa) was slightly (7%), but significantly less than that by MSDI (4.86 ± 2.44 kPa) (P < 0.05). MMDI can provide stiffness map of better image quality, and slightly lower stiffness values as compared to MSDI at 3T MRE, which radiologists should be aware of.

Integral abutment bridge for Louisiana's soft and stiff soils.

DOT National Transportation Integrated Search

2016-03-01

Integral abutment bridges (IABs) have been designed and constructed in a few US states in the past few : decades. The initial purpose of building such bridges was to eliminate the expansion joints and resolve the : joint-induced problems. Although IA...

Use of a Multivector Mandibular Distractor for Treatment of Pediatric Proximal Interphalangeal Joint Pilon Fractures: A Case-Based Review.

PubMed

Pedreira, Rachel; Cho, Brian H; Geer, Angela; DeJesus, Ramon A

2018-04-01

The difficulties in surgical treatment of pilon fractures of the finger include fragment reconstitution and posthealing stiffness. In adults, external fixation with traction and early active range of motion (AROM)/passive range of motion (PROM) during healing is considered necessary for avoiding joint stiffness and attaining realignment. The authors present a unique approach to pediatric pilon fractures that uses open reduction and multivector external fixation with delayed AROM/PROM. Initial immobilization and significant traction allowed for joint realignment and prevented noncompliance with staged distraction. The authors believe this immobilization leads to a superior outcome because, unlike adults, children tend to avoid stiffness and a larger distraction force allowed for sufficient joint realignment to regain range of motion (ROM). A right-handed 13-year-old boy sustained a right ring finger fracture and presented 12 days later. Radiographs revealed a comminuted Salter-Harris 4 fracture of the middle phalanx. The patient underwent open reduction and placement of multivector external fixation using a pediatric mandibular distractor/fixator. Significant traction was applied to distract the finger to length. Hardware was removed 6 weeks postoperatively and AROM was initiated after splinting. The patient started PROM 8 weeks postoperatively. Strengthening was initiated 2 weeks later. ROM improved and rehabilitation was continued. The patient exhibited nearly equal grip strength 12 weeks postoperatively. At 14 months follow-up, radiographs showed complete healing and joint realignment. There was no deformity or pain and finger length was restored. Management of pediatric pilon fractures is rarely described and presents unique considerations. Early-stage traction and immobilization using a multivector mandibular fixator/distractor is suitable in a child because noncompliance is avoided and there is a decreased risk for stiffness. Combining early immobilization with subsequent-staged AROM, PROM, and strengthening resulted in no loss of ROM and maintained articular symmetry.

Estimation of Quasi-Stiffness and Propulsive Work of the Human Ankle in the Stance Phase of Walking

PubMed Central

Shamaei, Kamran; Sawicki, Gregory S.; Dollar, Aaron M.

2013-01-01

Characterizing the quasi-stiffness and work of lower extremity joints is critical for evaluating human locomotion and designing assistive devices such as prostheses and orthoses intended to emulate the biological behavior of human legs. This work aims to establish statistical models that allow us to predict the ankle quasi-stiffness and net mechanical work for adults walking on level ground. During the stance phase of walking, the ankle joint propels the body through three distinctive phases of nearly constant stiffness known as the quasi-stiffness of each phase. Using a generic equation for the ankle moment obtained through an inverse dynamics analysis, we identify key independent parameters needed to predict ankle quasi-stiffness and propulsive work and also the functional form of each correlation. These parameters include gait speed, ankle excursion, and subject height and weight. Based on the identified form of the correlation and key variables, we applied linear regression on experimental walking data for 216 gait trials across 26 subjects (speeds from 0.75–2.63 m/s) to obtain statistical models of varying complexity. The most general forms of the statistical models include all the key parameters and have an R2 of 75% to 81% in the prediction of the ankle quasi-stiffnesses and propulsive work. The most specific models include only subject height and weight and could predict the ankle quasi-stiffnesses and work for optimal walking speed with average error of 13% to 30%. We discuss how these models provide a useful framework and foundation for designing subject- and gait-specific prosthetic and exoskeletal devices designed to emulate biological ankle function during level ground walking. PMID:23555839

Simulation of dynamics of beam structures with bolted joints using adjusted Iwan beam elements

NASA Astrophysics Data System (ADS)

Song, Y.; Hartwigsen, C. J.; McFarland, D. M.; Vakakis, A. F.; Bergman, L. A.

2004-05-01

Mechanical joints often affect structural response, causing localized non-linear stiffness and damping changes. As many structures are assemblies, incorporating the effects of joints is necessary to produce predictive finite element models. In this paper, we present an adjusted Iwan beam element (AIBE) for dynamic response analysis of beam structures containing joints. The adjusted Iwan model consists of a combination of springs and frictional sliders that exhibits non-linear behavior due to the stick-slip characteristic of the latter. The beam element developed is two-dimensional and consists of two adjusted Iwan models and maintains the usual complement of degrees of freedom: transverse displacement and rotation at each of the two nodes. The resulting element includes six parameters, which must be determined. To circumvent the difficulty arising from the non-linear nature of the inverse problem, a multi-layer feed-forward neural network (MLFF) is employed to extract joint parameters from measured structural acceleration responses. A parameter identification procedure is implemented on a beam structure with a bolted joint. In this procedure, acceleration responses at one location on the beam structure due to one known impulsive forcing function are simulated for sets of combinations of varying joint parameters. A MLFF is developed and trained using the patterns of envelope data corresponding to these acceleration histories. The joint parameters are identified through the trained MLFF applied to the measured acceleration response. Then, using the identified joint parameters, acceleration responses of the jointed beam due to a different impulsive forcing function are predicted. The validity of the identified joint parameters is assessed by comparing simulated acceleration responses with experimental measurements. The capability of the AIBE to capture the effects of bolted joints on the dynamic responses of beam structures, and the efficacy of the MLFF parameter identification procedure, are demonstrated.

Contact stiffness of regularly patterned multi-asperity interfaces

NASA Astrophysics Data System (ADS)

Li, Shen; Yao, Quanzhou; Li, Qunyang; Feng, Xi-Qiao; Gao, Huajian

2018-02-01

Contact stiffness is a fundamental mechanical index of solid surfaces and relevant to a wide range of applications. Although the correlation between contact stiffness, contact size and load has long been explored for single-asperity contacts, our understanding of the contact stiffness of rough interfaces is less clear. In this work, the contact stiffness of hexagonally patterned multi-asperity interfaces is studied using a discrete asperity model. We confirm that the elastic interaction among asperities is critical in determining the mechanical behavior of rough contact interfaces. More importantly, in contrast to the common wisdom that the interplay of asperities is solely dictated by the inter-asperity spacing, we show that the number of asperities in contact (or equivalently, the apparent size of contact) also plays an indispensable role. Based on the theoretical analysis, we propose a new parameter for gauging the closeness of asperities. Our theoretical model is validated by a set of experiments. To facilitate the application of the discrete asperity model, we present a general equation for contact stiffness estimation of regularly rough interfaces, which is further proved to be applicable for interfaces with single-scale random roughness.

Effect of sex and fatigue on muscle stiffness and musculoarticular stiffness of the knee joint in a young active population.

PubMed

Wang, Dan; De Vito, Giuseppe; Ditroilo, Massimiliano; Delahunt, Eamonn

2017-08-01

The purpose of this study was to investigate the influence of sex and fatigue on knee extensor peak torque (PT), muscle stiffness (MS) of the vastus lateralis (VL) and knee joint musculoarticular stiffness (MAS) in young adults. Twenty-two male and 22 female recreational athletes participated. Males were characterised by higher relaxed [pre-: males 364.43 (52.00) N · m -1 , females 270.27 (37.25) N · m -1 ; post-: males 446.75 (83.27) N · m -1 , females 307.39 (38.58) N · m -1 ] and contracted [pre-: males 495.07 (71.04) N · m -1 , females 332.34 (85.42) N · m -1 ; post-: males 546.37 (90.74) N · m -1 , females 349.21 (85.55) N · m -1 ] MS of the VL, and knee joint MAS [pre-: males 1450.11 (507.98) N · m -1 , females 1027.99 (227.33) N · m -1 ; post-: males 1345.81 (404.90) N · m -1 , females 952.78 (192.38) N · m -1 ] than females pre- and post-fatigue. A similar finding was observed in pre-fatigue normalised knee extensor PT [pre-: males 2.77 (0.42) N · m kg -1 , females 2.41 (0.40) N · m kg -1 , post-: males 2.53 (0.54) N · m kg -1 , females 2.26 (0.44) N · m kg -1 ]. After the fatigue protocol, normalised knee extensor PT and knee joint MAS decreased, whilst relaxed and contracted MS of the VL increased in both sexes. These observed differences may contribute to the higher risk of knee injury in females and following the onset of fatigue.

Optimization of prosthetic foot stiffness to reduce metabolic cost and intact knee loading during below-knee amputee walking: a theoretical study.

PubMed

Fey, Nicholas P; Klute, Glenn K; Neptune, Richard R

2012-11-01

Unilateral below-knee amputees develop abnormal gait characteristics that include bilateral asymmetries and an elevated metabolic cost relative to non-amputees. In addition, long-term prosthesis use has been linked to an increased prevalence of joint pain and osteoarthritis in the intact leg knee. To improve amputee mobility, prosthetic feet that utilize elastic energy storage and return (ESAR) have been designed, which perform important biomechanical functions such as providing body support and forward propulsion. However, the prescription of appropriate design characteristics (e.g., stiffness) is not well-defined since its influence on foot function and important in vivo biomechanical quantities such as metabolic cost and joint loading remain unclear. The design of feet that improve these quantities could provide considerable advancements in amputee care. Therefore, the purpose of this study was to couple design optimization with dynamic simulations of amputee walking to identify the optimal foot stiffness that minimizes metabolic cost and intact knee joint loading. A musculoskeletal model and distributed stiffness ESAR prosthetic foot model were developed to generate muscle-actuated forward dynamics simulations of amputee walking. Dynamic optimization was used to solve for the optimal muscle excitation patterns and foot stiffness profile that produced simulations that tracked experimental amputee walking data while minimizing metabolic cost and intact leg internal knee contact forces. Muscle and foot function were evaluated by calculating their contributions to the important walking subtasks of body support, forward propulsion and leg swing. The analyses showed that altering a nominal prosthetic foot stiffness distribution by stiffening the toe and mid-foot while making the ankle and heel less stiff improved ESAR foot performance by offloading the intact knee during early to mid-stance of the intact leg and reducing metabolic cost. The optimal design also provided moderate braking and body support during the first half of residual leg stance, while increasing the prosthesis contributions to forward propulsion and body support during the second half of residual leg stance. Future work will be directed at experimentally validating these results, which have important implications for future designs of prosthetic feet that could significantly improve amputee care.

Development of an Intelligent Stretching Device for Ankle Joints With Contracture/Spasticity

DTIC Science & Technology

2001-10-25

percentage corresponded to background dorsi-flexion muscle contraction and 0% was the relaxed state. Next, tendon reflexes were evaluated...the representative cases, joint stiffness was reduced markedly after stretching across the range of muscle contraction (Fig. 5), including both

Sway‐dependent changes in standing ankle stiffness caused by muscle thixotropy

PubMed Central

Sakanaka, Tania E.; Lakie, Martin

2016-01-01

Key points The passive stiffness of the calf muscles contributes to standing balance, although the properties of muscle tissue are highly labile.We investigated the effect of sway history upon intrinsic ankle stiffness and demonstrated reductions in stiffness of up to 43% during conditions of increased baseline sway.This sway dependence was most apparent when using low amplitude stiffness‐measuring perturbations, and the short‐range stiffness component was smaller during periods of high sway.These characteristics are consistent with the thixotropic properties of the calf muscles causing the observed changes in ankle stiffness.Periods of increased sway impair the passive stabilization of standing, demanding more active neural control of balance. Abstract Quiet standing is achieved through a combination of active and passive mechanisms, consisting of neural control and intrinsic mechanical stiffness of the ankle joint, respectively. The mechanical stiffness is partly determined by the calf muscles. However, the viscoelastic properties of muscle are highly labile, exhibiting a strong dependence on movement history. By measuring the effect of sway history upon ankle stiffness, the present study determines whether this lability has consequences for the passive stabilization of human standing. Ten subjects stood quietly on a rotating platform whose axis was collinear with the ankle joint. Ankle sway was increased by slowly tilting this platform in a random fashion, or decreased by fixing the body to a board. Ankle stiffness was measured by using the same platform to simultaneously apply small, brief perturbations (<0.6 deg; 140 ms) at the same time as the resulting torque response was recorded. The results show that increasing sway reduces ankle stiffness by up to 43% compared to the body‐fixed condition. Normal quiet stance was associated with intermediate values. The effect was most apparent when using smaller perturbation amplitudes to measure stiffness (0.1 vs. 0.6 deg). Furthermore, torque responses exhibited a biphasic pattern, consisting of an initial steep rise followed by a shallower increase. This transition occurred earlier during increased levels of ankle sway. These results are consistent with a movement‐dependent change in passive ankle stiffness caused by thixotropic properties of the calf muscle. The consequence is to place increased reliance upon active neural control during times when increased sway renders ankle stiffness low. PMID:26607292

Soldier-relevant body borne loads increase knee joint contact force during a run-to-stop maneuver.

PubMed

Ramsay, John W; Hancock, Clifford L; O'Donovan, Meghan P; Brown, Tyler N

2016-12-08

The purpose of this study was to understand the effects of load carriage on human performance, specifically during a run-to-stop (RTS) task. Using OpenSim analysis tools, knee joint contact force, grounds reaction force, leg stiffness and lower extremity joint angles and moments were determined for nine male military personnel performing a RTS under three load configurations (light, ~6kg, medium, ~20kg, and heavy, ~40kg). Subject-based means for each biomechanical variable were submitted to repeated measures ANOVA to test the effects of load. During the RTS, body borne load significantly increased peak knee joint contact force by 1.2 BW (p<0.001) and peak vertical (p<0.001) and anterior-posterior (p=0.002) ground reaction forces by 0.6 BW and 0.3 BW, respectively. Body borne load also had a significant effect on hip (p=0.026) posture with the medium load and knee (p=0.046) posture with the heavy load. With the heavy load, participants exhibited a substantial, albeit non-significant increase in leg stiffness (p=0.073 and d=0.615). Increases in joint contact force exhibited during the RTS were primarily due to greater GRFs that impact the soldier with each incremental addition of body borne load. The stiff leg, extended knee and large braking force the soldiers exhibited with the heavy load suggests their injury risk may be greatest with that specific load configuration. Further work is needed to determine if the biomechanical profile exhibited with the heavy load configuration translates to unsafe shear forces at the knee joint and consequently, a higher likelihood of injury. Published by Elsevier Ltd.

Experimental measure of arm stiffness during single reaching movements with a time-frequency analysis

PubMed Central

Pierobon, Alberto; DiZio, Paul; Lackner, James R.

2013-01-01

We tested an innovative method to estimate joint stiffness and damping during multijoint unfettered arm movements. The technique employs impulsive perturbations and a time-frequency analysis to estimate the arm's mechanical properties along a reaching trajectory. Each single impulsive perturbation provides a continuous estimation on a single-reach basis, making our method ideal to investigate motor adaptation in the presence of force fields and to study the control of movement in impaired individuals with limited kinematic repeatability. In contrast with previous dynamic stiffness studies, we found that stiffness varies during movement, achieving levels higher than during static postural control. High stiffness was associated with elevated reflexive activity. We observed a decrease in stiffness and a marked reduction in long-latency reflexes around the reaching movement velocity peak. This pattern could partly explain the difference between the high stiffness reported in postural studies and the low stiffness measured in dynamic estimation studies, where perturbations are typically applied near the peak velocity point. PMID:23945781

Reduced-order modeling approach for frictional stick-slip behaviors of joint interface

NASA Astrophysics Data System (ADS)

Wang, Dong; Xu, Chao; Fan, Xuanhua; Wan, Qiang

2018-03-01

The complex frictional stick-slip behaviors of mechanical joint interface have a great effect on the dynamic properties of assembled structures. In this paper, a reduced-order modeling approach based on the constitutive Iwan model is proposed to describe the stick-slip behaviors of joint interface. An improved Iwan model is developed to describe the non-zero residual stiffness at macro-slip regime and smooth transition of joint stiffness from micro-slip to macro-slip regime, and the power-law relationship of energy dissipation during the micro-slip regime. In allusion to these nonlinear behaviors, the finite element method is used to calculate the recycle force under monolithic loading and the energy dissipation per cycle under oscillatory loading. The proposed model is then used to predict the nonlinear stick-slip behaviors of joint interface by curve-fitting to the results of finite element analysis, and the results show good agreements with the finite element analysis. A comparison with the experiment results in literature is also made. The proposed model agrees very well with the experiment results.

Estimating the Mechanical Behavior of the Knee Joint during Crouch Gait: Implications for Real-Time Motor Control of Robotic Knee Orthoses

PubMed Central

Damiano, Diane L.; Bulea, Thomas C.

2016-01-01

Individuals with cerebral palsy frequently exhibit crouch gait, a pathological walking pattern characterized by excessive knee flexion. Knowledge of the knee joint moment during crouch gait is necessary for the design and control of assistive devices used for treatment. Our goal was to 1) develop statistical models to estimate knee joint moment extrema and dynamic stiffness during crouch gait, and 2) use the models to estimate the instantaneous joint moment during weight-acceptance. We retrospectively computed knee moments from 10 children with crouch gait and used stepwise linear regression to develop statistical models describing the knee moment features. The models explained at least 90% of the response value variability: peak moment in early (99%) and late (90%) stance, and dynamic stiffness of weight-acceptance flexion (94%) and extension (98%). We estimated knee extensor moment profiles from the predicted dynamic stiffness and instantaneous knee angle. This approach captured the timing and shape of the computed moment (root-mean-squared error: 2.64 Nm); including the predicted early-stance peak moment as a correction factor improved model performance (root-mean-squared error: 1.37 Nm). Our strategy provides a practical, accurate method to estimate the knee moment during crouch gait, and could be used for real-time, adaptive control of robotic orthoses. PMID:27101612

Effects of circumferential ankle pressure on ankle proprioception, stiffness, and postural stability: a preliminary investigation.

PubMed

You, Sung H; Granata, Kevin P; Bunker, Linda K

2004-08-01

Cross-sectional repeated-measures design. Determine the effects of circumferential ankle pressure (CAP) intervention on proprioceptive acuity, ankle stiffness, and postural stability. The application of CAP using braces, taping, and adaptive shoes or military boots is widely used to address chronic ankle instability (CAI). An underlying assumption is that the CAP intervention might improve ankle stability through increased proprioceptive acuity and stiffness in the ankle. METHOD AND MEASURES: A convenience sample of 10 subjects was recruited from the local university community and categorized according to proprioceptive acuity (high, low) and ankle stability (normal, CAI). Proprioceptive acuity was measured when blindfolded subjects were asked to accurately reproduce a self-selected target ankle position before and after the application of CAP. Proprioceptive acuity was determined in 5 different ankle joint position sense tests: neutral, inversion, eversion, plantar flexion, and dorsiflexion. Joint position angles were recorded electromechanically using a potentiometer. Passive ankle stiffness was computed from the ratio of applied static moment versus angular displacement. Active ankle stiffness was determined from biomechanical analyses of ankle motion following a mediolateral perturbation. Postural stability was quantified from the center of pressure displacement in the mediolateral and the anteroposterior directions in unipedal stance. All measurements were recorded with and without CAP applied by a pediatric blood pressure cuff. Data were analyzed using a separate mixed-model analysis of variance (ANOVA) for each dependent variable. Post hoc comparison using Tukey's honestly significant difference (HSD) test was performed if significant interactions were obtained. Significance level was set at P<.05 for all analyses. Significant group (high versus low proprioceptive acuity) x CAP interactions were identified for postural stability. Passive ankle stiffness was not increased by an application of CAP. Active ankle stiffness was significantly different between the high and low proprioceptive acuity groups and was not affected by an application of CAP. Significant group (normal versus CAI) x CAP interactions were observed for mediolateral center-of-pressure displacement with a main effect of group on neutral joint position sense. Application of CAP increased proprioceptive acuity and demonstrated trends toward increased active stiffness in the ankle, hence improved postural stability. The effects tend to be limited to individuals with low proprioceptive acuity.

Heavily loaded joints for assembling aerobrake support trusses

NASA Technical Reports Server (NTRS)

Bandel, Hannskarl; Olsson, Nils; Levintov, Boris

1990-01-01

The major emphasis was to develop erectable joints for large aerobrake support trusses. The truss joints must be able to withstand the large forces experienced by the truss during the aero-pass, as well as be easily assembled and disassembled on orbit by astronauts or robots. Other important design considerations include; strength, stiffness, and allowable error in strut length. Six mechanical joint designs, as well as a seventh joint design, where a high strength epoxy is injected to make the connection rigid, are presented.

Artificial atlanto-odontoid joint replacement through a transoral approach.

PubMed

Lu, Bin; He, Xi Jing; Zhao, Chen Guang; Li, Hao Peng; Wang, Dong

2009-01-01

Resection of the odontoid process and anterior arch of the atlas results in atlantoaxial instability, which if left uncorrected may lead to severe neurological complications. Currently, such atlantoaxial instability is corrected by anterior and/or posterior C1-C2 fusion. However, this results in considerable loss of rotation function of the atlantoaxial complex. From the viewpoint of retaining the rotation function and providing stability, we designed an artificial atlanto-odontoid joint based on anatomical measurements of 50 pairs of dry atlantoaxial specimens by digital calipers and 10 fresh cadaveric specimens by microsurgical techniques. The metal-on-metal titanium alloy joint has an arc-shaped atlas component, and a hollow cylindrical bushing into which fits a rotation axle of an inverted v-shaped axis component and is implanted through a transoral approach. After the joint was implanted onto specimens with anterior decompression, biomechanical tests were performed to compare the stability parameters in the intact state, after decompression, after artificial joint replacement, and after fatigue test. Compared to the intact state, artificial joint replacement resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension, and lateral bending (P < 0.001); however, with regard to axial rotation, there was no significant difference in ROM (P = 0.405), a significant increase in NZ (P = 0.008), and a significant decrease in stiffness (P = 0.003). Compared to the decompressed state, artificial joint replacement resulted in a significantly decreased ROM (P B 0.021) and NZ (P B 0.002) and a significantly increased stiffness (P \\ 0.001) in all directions. Following artificial joint replacement, there was no significant difference in ROM (P C 0.719), NZ (P C 0.580), and stiffness (P C 0.602) in all directions before and after the fatigue test. The artificial joint showed no signs of wear and tear after the fatigue test. This artificial atlanto-odontoid joint may be useful in cases of odontoid resection due to malunion or nonunion of odontoid fracture, atraumatic odontoid fracture, irreducible atlas dislocation, posterior atlantoaxial subluxation, or congenital skull base abnormalities.

Artificial atlanto-odontoid joint replacement through a transoral approach

PubMed Central

Lu, Bin; Zhao, Chen Guang; Li, Hao Peng; Wang, Dong

2008-01-01

Resection of the odontoid process and anterior arch of the atlas results in atlantoaxial instability, which if left uncorrected may lead to severe neurological complications. Currently, such atlantoaxial instability is corrected by anterior and/or posterior C1–C2 fusion. However, this results in considerable loss of rotation function of the atlantoaxial complex. From the viewpoint of retaining the rotation function and providing stability, we designed an artificial atlanto-odontoid joint based on anatomical measurements of 50 pairs of dry atlantoaxial specimens by digital calipers and 10 fresh cadaveric specimens by microsurgical techniques. The metal-on-metal titanium alloy joint has an arc-shaped atlas component, and a hollow cylindrical bushing into which fits a rotation axle of an inverted v-shaped axis component and is implanted through a transoral approach. After the joint was implanted onto specimens with anterior decompression, biomechanical tests were performed to compare the stability parameters in the intact state, after decompression, after artificial joint replacement, and after fatigue test. Compared to the intact state, artificial joint replacement resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension, and lateral bending (P < 0.001); however, with regard to axial rotation, there was no significant difference in ROM (P = 0.405), a significant increase in NZ (P = 0.008), and a significant decrease in stiffness (P = 0.003). Compared to the decompressed state, artificial joint replacement resulted in a significantly decreased ROM (P ≤ 0.021) and NZ (P ≤ 0.002) and a significantly increased stiffness (P < 0.001) in all directions. Following artificial joint replacement, there was no significant difference in ROM (P ≥ 0.719), NZ (P ≥ 0.580), and stiffness (P ≥ 0.602) in all directions before and after the fatigue test. The artificial joint showed no signs of wear and tear after the fatigue test. This artificial atlanto-odontoid joint may be useful in cases of odontoid resection due to malunion or nonunion of odontoid fracture, atraumatic odontoid fracture, irreducible atlas dislocation, posterior atlantoaxial subluxation, or congenital skull base abnormalities. PMID:19043745

The gearing function of running shoe longitudinal bending stiffness.

PubMed

Willwacher, Steffen; König, Manuel; Braunstein, Björn; Goldmann, Jan-Peter; Brüggemann, Gert-Peter

2014-07-01

The purpose of the present study was to investigate whether altered longitudinal bending stiffness (LBS) levels of the midsole of a running shoe lead to a systematic change in lower extremity joint lever arms of the ground reaction force (GRF). Joint moments and GRF lever arms in the sagittal plane were determined from 19 male subjects running at 3.5 m/s using inverse dynamics procedures. LBS was manipulated using carbon fiber insoles of 1.9 mm and 3.2 mm thickness. Increasing LBS led to a significant shift of joint lever arms to a more anterior position. Effects were more pronounced at distal joints. Ankle joint moments were not significantly increased in the presence of higher GRF lever arms when averaged over all subjects. Still, two individual strategies (1: increase ankle joint moments while keeping push-off times almost constant, 2: decrease ankle joint moments and increase push-off times) could be identified in response to increased ankle joint lever arms that might reflect individual differences between subjects with respect to strength capacities or anthropometric characteristics. The results of the present study indicate that LBS systematically influences GRF lever arms of lower extremity joints during the push-off phase in running. Further, individual responses to altered LBS levels could be identified that could aid in finding optimum LBS values for a given individual. Copyright © 2014 Elsevier B.V. All rights reserved.

The behavior of bonded doubler splices for composite sandwich panels

NASA Technical Reports Server (NTRS)

Zeller, T. A.; Weisahaar, T. A.

1980-01-01

The results of an investigation into the behavior of adhesively bonded doubler splices of two composite material sandwich panels are presented. The splices are studied from three approaches: analytical; numerical (finite elements); and experimental. Several parameters that characterize the splice are developed to determine their influence upon joint strength. These parameters are: doubler overlap length; core stiffness; laminate bending stiffness; the size of the gap between the spliced sandwich panels; and room and elevated temperatures. Similarities and contrasts between these splices and the physically similar single and double lap joints are discussed. The results of this investigation suggest several possible approaches to improving the strength of the sandwich splices.

Electrical stimulation on joint contracture: an experiment in rat model with direct current.

PubMed

Akai, M; Shirasaki, Y; Tateishi, T

1997-04-01

To examine whether electrical stimulation could decrease the degree of joint stiffness in a rat lower extremity model. Rat knee joints were surgically immobilized in a flexed position for 3 weeks. Two groups of rats were stimulated with 20 microA and 50 microA constant direct current. Another group had surgical intervention and sham electrodes without electricity. The hind leg was extirpated and prepared for a sample with the femur-knee joint-tibia unit. Recording the knee flexion angle with extension torque, the degree of joint contracture was assessed biomechanically by measuring the bone-joint-bone sample as a cantilever. Measurement was performed with (1) spectral analysis of transfer function measurement using random mechanical noise with frequency range from 1 to 50Hz, and (2) dynamic stiffness and loss tangent with steady-state sinusoidal excitation (11 and 35Hz). The results showed that no significant difference or trend was found in vibration analysis among three groups. However, spectral analysis of transfer function measurement revealed more deformation against load, and more viscous nature in the stimulation groups, especially in low frequency band, than in the sham group. Electrical stimulation with constant direct current has a possibility of reducing the degree of joint contracture.

Advanced joining concepts for passive vibration control

NASA Technical Reports Server (NTRS)

Prucz, Jacky C.; Spyrakos, Constantine

1987-01-01

A comprehensive parametric study was carried out to establish design guidelines for favorable tradeoffs between damping benefits and the associated stiffness, strength and weight penalties in a rhombic joint. The results are compared with the corresponding tradeoffs for a double-lap joint made of the same materials.

[Restricted motion after total knee arthroplasty].

PubMed

Kucera, T; Urban, K; Karpas, K; Sponer, P

2007-10-01

The aim of the study was to ascertain what proportion of patients undergoing total knee arthroplasty (TKA) complain of restricted knee joint motion, and to investigate options for improvement of this situation. Our evaluation included a group of 796 patients treated with TKA at our department in the period from January 1, 1990, to December 31, 2004. In all cases, a condylar implant with preservation of the posterior cruciate ligaments was used. In addition to medical history, the range of motion, knee joint malalignment and radiological findings were assessed before surgery. After THA, the type of implant and complications, if any, were recorded, and improvement in joint motion was followed up. Based on the results of Kim et al., flexion contracture equal to or higher than 15 degrees and/or flexion less than 75 degrees were made the criteria of stiffness after THA. Patients with restricted THA motion who had aseptic or septic implant loosening were not included. Of the 796 evaluated patients, 32 (4.14 %) showed restricted motion after total knee arthroplasty, as assessed by the established criteria. In 16 patients, stiffness defined by these criteria had existed before surgery, and three patients showed an excessive production of adhesions and heterotopic ossifications. In three patients, the implantation procedure resulted in an elevated level of the original joint line and subsequent development of patella infera and increased tension of the posterior cruciate ligament. Four patients declined physical therapy and, in six, the main cause of stiffness could not be found. Seventeen patients did not require surgical therapy for restricted motion; TKA provided significant pain relief and they considered the range of motion achieved to be sufficient. One patient underwent redress 3 months after surgery, but with no success. Repeated releases of adhesions, replacement of a polyethylene liner and revision surgery of the extensor knee structures were performed in 15 patients. In these, the average value of knee flexion increased by 17 degrees only and, in the patients suffering from excessive adhesion production, this value remained almost unchanged. Revision TKA was carried out in four patients, in whom knee joint flexion increased on average by 35 degrees to achieve an average flexion of 83 degrees. Restricted motion after TKA has been reported to range from 1.3 % to 12.0 %, but consistent criteria have not been set up. In our study it was 4.14 %. In agreement with the literature data, one of the reasons was pre-operative restricted motion, which was recorded in 16 of 32 patients. Similarly, also in our patients, biological predisposition to excessive production of fibrocartilage associated with adhesions in all knee joint compartments was the major therapeutic problem. Intra-operative fractures, ligament tears requiring post-operative fixation and unremoved dorsal osteophytes lead to the restriction of knee joint motion. By inadequate resection of articular surface, the original joint line may be at a higher level; this results in an increased tension of the posterior cruciate ligament and patella infera development, both influencing knee flexion. In our study, three patients were affected. Knee joint stiffness can also develop in patients declining physical therapy or in whom this is not correctly performed, often for insufficient analgesia. In contrast to the data reported in the literature, 17 of 32 patients in this study had no need for surgical treatment of restricted knee joint motion. Redress under general anesthesia was not effective. For markedly restricted motion of the knee joint, reimplantation can be recommended or, in less severe cases, an intervention on adjacent soft tissues. Restricted motion of the knee joint after TKA is difficult to treat and, therefore, prevention is recommended. This should include thorough conservative treatment of gonarthrosis, early indication for surgery, prevention of elevation in the joint line and consistent rehabilitation with appropriate analgesia. For severe stiffness of the knee joint, as evaluated by the criteria of Kim et al., revision arthroplasty can be recommended.

Identification of a parametric, discrete-time model of ankle stiffness.

PubMed

Guarin, Diego L; Jalaleddini, Kian; Kearney, Robert E

2013-01-01

Dynamic ankle joint stiffness defines the relationship between the position of the ankle and the torque acting about it and can be separated into intrinsic and reflex components. Under stationary conditions, intrinsic stiffness can described by a linear second order system while reflex stiffness is described by Hammerstein system whose input is delayed velocity. Given that reflex and intrinsic torque cannot be measured separately, there has been much interest in the development of system identification techniques to separate them analytically. To date, most methods have been nonparametric and as a result there is no direct link between the estimated parameters and those of the stiffness model. This paper presents a novel algorithm for identification of a discrete-time model of ankle stiffness. Through simulations we show that the algorithm gives unbiased results even in the presence of large, non-white noise. Application of the method to experimental data demonstrates that it produces results consistent with previous findings.

Prevention of the Post-traumatic Fibrotic Response in Joints

DTIC Science & Technology

2014-10-01

an experimental model in mice. The American journal of forensic medicine and pathology . 1988; 9(4):310-2. 14 APPENDICES: An abstract...ongoing study addresses the critical clinical problem of posttraumatic joint stiffness, a pathology that reduces the range of motion (ROM) of injured...joints and contributes to the development of osteoarthritis. The fundamental hypothesis that drives the current study is that pathological fibrotic

Substrate Stiffness Regulates Proinflammatory Mediator Production through TLR4 Activity in Macrophages

PubMed Central

Previtera, Michelle L.; Sengupta, Amitabha

2015-01-01

Clinical data show that disease adversely affects tissue elasticity or stiffness. While macrophage activity plays a critical role in driving disease pathology, there are limited data available on the effects of tissue stiffness on macrophage activity. In this study, the effects of substrate stiffness on inflammatory mediator production by macrophages were investigated. Bone marrow–derived macrophages were grown on polyacrylamide gels that mimicked the stiffness of a variety of soft biological tissues. Overall, macrophages grown on soft substrates produced less proinflammatory mediators than macrophages grown on stiff substrates when the endotoxin LPS was added to media. In addition, the pathways involved in stiffness–regulated proinflammation were investigated. The TLR4 signaling pathway was examined by evaluating TLR4, p–NF–κB p65, MyD88, and p–IκBα expression as well as p–NF–κB p65 translocation. Expression and translocation of the various signaling molecules were higher in macrophages grown on stiff substrates than on soft substrates. Furthermore, TLR4 knockout experiments showed that TLR4 activity enhanced proinflammation on stiff substrates. In conclusion, these results suggest that proinflammatory mediator production initiated by TLR4 is mechanically regulated in macrophages. PMID:26710072

Estimation of Quasi-Stiffness of the Human Hip in the Stance Phase of Walking

PubMed Central

Shamaei, Kamran; Sawicki, Gregory S.; Dollar, Aaron M.

2013-01-01

This work presents a framework for selection of subject-specific quasi-stiffness of hip orthoses and exoskeletons, and other devices that are intended to emulate the biological performance of this joint during walking. The hip joint exhibits linear moment-angular excursion behavior in both the extension and flexion stages of the resilient loading-unloading phase that consists of terminal stance and initial swing phases. Here, we establish statistical models that can closely estimate the slope of linear fits to the moment-angle graph of the hip in this phase, termed as the quasi-stiffness of the hip. Employing an inverse dynamics analysis, we identify a series of parameters that can capture the nearly linear hip quasi-stiffnesses in the resilient loading phase. We then employ regression analysis on experimental moment-angle data of 216 gait trials across 26 human adults walking over a wide range of gait speeds (0.75–2.63 m/s) to obtain a set of general-form statistical models that estimate the hip quasi-stiffnesses using body weight and height, gait speed, and hip excursion. We show that the general-form models can closely estimate the hip quasi-stiffness in the extension (R2 = 92%) and flexion portions (R2 = 89%) of the resilient loading phase of the gait. We further simplify the general-form models and present a set of stature-based models that can estimate the hip quasi-stiffness for the preferred gait speed using only body weight and height with an average error of 27% for the extension stage and 37% for the flexion stage. PMID:24349136

Stretching of Active Muscle Elicits Chronic Changes in Multiple Strain Risk Factors.

PubMed

Kay, Anthony David; Richmond, Dominic; Talbot, Chris; Mina, Minas; Baross, Anthony William; Blazevich, Anthony John

2016-07-01

The muscle stretch intensity imposed during "flexibility" training influences the magnitude of joint range of motion (ROM) adaptation. Thus, stretching while the muscle is voluntarily activated was hypothesized to provide a greater stimulus than passive stretching. The effect of a 6-wk program of stretch imposed on an isometrically contracting muscle (i.e., qualitatively similar to isokinetic eccentric training) on muscle-tendon mechanics was therefore studied in 13 healthy human volunteers. Before and after the training program, dorsiflexion ROM, passive joint moment, and maximal isometric plantarflexor moment were recorded on an isokinetic dynamometer. Simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. Training was performed twice weekly and consisted of five sets of 12 maximal isokinetic eccentric contractions at 10°·s. Significant increases (P < 0.01) in ROM (92.7% [14.7°]), peak passive moment (i.e., stretch tolerance; 136.2%), area under the passive moment curve (i.e., energy storage; 302.6%), and maximal isometric plantarflexor moment (51.3%) were observed after training. Although no change in the slope of the passive moment curve (muscle-tendon stiffness) was detected (-1.5%, P > 0.05), a significant increase in tendon stiffness (31.2%, P < 0.01) and a decrease in passive muscle stiffness (-14.6%, P < 0.05) were observed. The substantial positive adaptation in multiple functional and physiological variables that are cited within the primary etiology of muscle strain injury, including strength, ROM, muscle stiffness, and maximal energy storage, indicate that the stretching of active muscle might influence injury risk in addition to muscle function. The lack of change in muscle-tendon stiffness simultaneous with significant increases in tendon stiffness and decreases in passive muscle stiffness indicates that tissue-specific effects were elicited.

Multiscale biomechanical responses of adapted bone-periodontal ligament-tooth fibrous joints

PubMed Central

Jang, Andrew T.; Merkle, Arno; Fahey, Kevin; Gansky, Stuart A.; Ho, Sunita P.

2015-01-01

Reduced functional loads cause adaptations in organs. In this study, temporal adaptations of bone-ligament-tooth fibrous joints to reduced functional loads were mapped using a holistic approach. Systematic studies were performed to evaluate organ-level and tissue-level adaptations in specimens harvested periodically from rats given powder food for 6 months (N = 60 over 8,12,16,20, and 24 weeks). Bone-periodontal ligament (PDL)-tooth fibrous joint adaptation was evaluated by comparing changes in joint stiffness with changes in functional space between the tooth and alveolar bony socket. Adaptations in tissues included mapping changes in the PDL and bone architecture as observed from collagen birefringence, bone hardness and volume fraction in rats fed soft foods (soft diet, SD) compared to those fed hard pellets as a routine diet (hard diet, HD). In situ biomechanical testing on harvested fibrous joints revealed increased stiffness in SD groups (SD:239-605 N/mm) (p<0.05) at 8 and 12 weeks. Increased joint stiffness in early development phase was due to decreased functional space (at 8wks change in functional space was −33 µm, at 12wks change in functional space was −30 µm) and shifts in tissue quality as highlighted by birefringence, architecture and hardness. These physical changes were not observed in joints that were well into function, that is, in rodents older than 12 weeks of age. Significant adaptations in older groups were highlighted by shifts in bone growth (bone volume fraction 24wks: Δ-0.06) and bone hardness (8wks: Δ−0.04 GPa, 16 wks: Δ−0.07 GPa, 24wks: Δ−0.06 GPa). The response rate (N/s) of joints to mechanical loads decreased in SD groups. Results from the study showed that joint adaptation depended on age. The initial form-related adaptation (observed change in functional space) can challenge strain-adaptive nature of tissues to meet functional demands with increasing age into adulthood. The coupled effect between functional space in the bone-PDLtooth complex and strain-adaptive nature of tissues is necessary to accommodate functional demands, and is temporally sensitive despite joint malfunction. From an applied science perspective, we propose that adaptations are registered as functional history in tissues and joints. PMID:26151121

Dynamics of quiet human stance: computer simulations of a triple inverted pendulum model.

PubMed

Günther, Michael; Wagner, Heiko

2016-01-01

For decades, the biomechanical description of quiet human stance has been dominated by the single inverted pendulum (SIP) paradigm. However, in the past few years, the SIP model family has been falsified as an explanatory approach. Double inverted pendulum models have recently proven to be inappropriate. Human topology with three major leg joints suggests in a natural way to examine triple inverted pendulum (TIP) models as an appropriate approach. In this study, we focused on formulating a TIP model that can synthesise stable balancing attractors based on minimalistic sensor information and actuation complexity. The simulated TIP oscillation amplitudes are realistic in vertical direction. Along with the horizontal ankle, knee and hip positions, though, all simulated joint angle amplitudes still exceed the measured ones about threefold. It is likely that they could be eventually brought down to the physiological range by using more sensor information. The TIP systems' eigenfrequency spectra come out as another major result. The eigenfrequencies spread across about 0.1 Hz...20 Hz. Our main result is that joint stiffnesses can be reduced even below statically required values by using an active hip torque balancing strategy. When reducing mono- and bi-articular stiffnesses further down to levels threatening dynamic stability, the spectra indicate a change from torus-like (stable) to strange (chaotic) attractors. Spectra of measured ground reaction forces appear to be strange-attractor-like. We would conclude that TIP models are a suitable starting point to examine more deeply the dynamic character of and the essential structural properties behind quiet human stance. Abbreviations and technical terms Inverted pendulum body exposed to gravity and pivoting in a joint around position of unstable equilibrium (operating point) SIP single inverted pendulum: one rigid body pivoting around fixation to the ground (external joint) DIP double inverted pendulum: two bodies; external and internal joint operate around instability TIP triple inverted pendulum: three bodies; external and both internal joints operate around instability QIP quadruple inverted pendulum: four bodies, foot replaces external joint; all three internal joints operate around instability Eigenfrequency characteristic frequency that a physical system is oscillating at when externally excited at a limited energy level DOF degree of freedom; in mechanics: linear displacement or angle or combination thereof Mono-articular stiffness: coefficient of proportionality between mechanical displacement of a DOF and restoring force/torque component in the respective DOF Bi-articular stiffness coefficient of proportionality between mechanical displacement of a DOF and restoring force/torque component in another DOF GRF ground reaction force HAT segment including head, arms and trunk COM centre of mass COP centre of pressure in the plane of the force platform surface.

Knee joint passive stiffness and moment in sagittal and frontal planes markedly increase with compression.

PubMed

Marouane, H; Shirazi-Adl, A; Adouni, M

2015-01-01

Knee joints are subject to large compression forces in daily activities. Due to artefact moments and instability under large compression loads, biomechanical studies impose additional constraints to circumvent the compression position-dependency in response. To quantify the effect of compression on passive knee moment resistance and stiffness, two validated finite element models of the tibiofemoral (TF) joint, one refined with depth-dependent fibril-reinforced cartilage and the other less refined with homogeneous isotropic cartilage, are used. The unconstrained TF joint response in sagittal and frontal planes is investigated at different flexion angles (0°, 15°, 30° and 45°) up to 1800 N compression preloads. The compression is applied at a novel joint mechanical balance point (MBP) identified as a point at which the compression does not cause any coupled rotations in sagittal and frontal planes. The MBP of the unconstrained joint is located at the lateral plateau in small compressions and shifts medially towards the inter-compartmental area at larger compression forces. The compression force substantially increases the joint moment-bearing capacities and instantaneous angular rigidities in both frontal and sagittal planes. The varus-valgus laxities diminish with compression preloads despite concomitant substantial reductions in collateral ligament forces. While the angular rigidity would enhance the joint stability, the augmented passive moment resistance under compression preloads plays a role in supporting external moments and should as such be considered in the knee joint musculoskeletal models.

High frequency, multi-axis dynamic stiffness analysis of a fractionally damped elastomeric isolator using continuous system theory

NASA Astrophysics Data System (ADS)

Fredette, Luke; Singh, Rajendra

2017-02-01

A spectral element approach is proposed to determine the multi-axis dynamic stiffness terms of elastomeric isolators with fractional damping over a broad range of frequencies. The dynamic properties of a class of cylindrical isolators are modeled by using the continuous system theory in terms of homogeneous rods or Timoshenko beams. The transfer matrix type dynamic stiffness expressions are developed from exact harmonic solutions given translational or rotational displacement excitations. Broadband dynamic stiffness magnitudes (say up to 5 kHz) are computationally verified for axial, torsional, shear, flexural, and coupled stiffness terms using a finite element model. Some discrepancies are found between finite element and spectral element models for the axial and flexural motions, illustrating certain limitations of each method. Experimental validation is provided for an isolator with two cylindrical elements (that work primarily in the shear mode) using dynamic measurements, as reported in the prior literature, up to 600 Hz. Superiority of the fractional damping formulation over structural or viscous damping models is illustrated via experimental validation. Finally, the strengths and limitations of the spectral element approach are briefly discussed.

Relationships between habitual physical activity and osteoarthrosis in ageing women.

PubMed

White, J A; Wright, V; Hudson, A M

1993-11-01

The examination of middle-aged women specialist teachers of physical education, who have undertaken habitual physical activity over many years, demonstrated a lower prevalence of osteoarthrosis in the knee joints, a greater prevalence of degenerative joint disease in the lumbar spine and a similar prevalence of osteoarthrosis in the hips, compared with a closely age-matched group. A further review 12 years later revealed significantly less joint pain and joint stiffness in active women compared with less active controls.

Serum matrix metalloproteinase 3 in detecting remitting seronegative symmetrical synovitis with pitting edema syndrome: A case report.

PubMed

Kenzaka, Tsuneaki; Goda, Ken

2018-05-16

We report a case of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome in a 71-year-old woman. She referred to our hospital with finger stiffness, edema of both hands and feet, pain of bilateral shoulder, wrist, metacarpophalangeal, proximal interphalangeal, and ankle joints. Rheumatoid factor was negative, human leukocyte antigen -B7 antigen was positive. Moreover, matrix metalloproteinase 3 (MMP-3) was high. She was diagnosed with RS3PE syndrome, and treatment with prednisolone (15 mg/d) was started. One week after prednisolone treatment initiation, CRP decreased to negative, and joint pain was almost completely resolved. However, hand stiffness persisted, and MMP-3 level was still high. Thus, prednisolone dose was increased to 20 mg/d, and the stiffness resolved. Twenty days after treatment initiation, MMP-3 was normalized. MMP-3 was more indicative of RS3PE syndrome symptoms than CRP. Thus, MMP-3 seems to be more sensitive to RS3PE syndrome symptoms.

Serum matrix metalloproteinase 3 in detecting remitting seronegative symmetrical synovitis with pitting edema syndrome: A case report

PubMed Central

Kenzaka, Tsuneaki; Goda, Ken

2018-01-01

We report a case of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome in a 71-year-old woman. She referred to our hospital with finger stiffness, edema of both hands and feet, pain of bilateral shoulder, wrist, metacarpophalangeal, proximal interphalangeal, and ankle joints. Rheumatoid factor was negative, human leukocyte antigen -B7 antigen was positive. Moreover, matrix metalloproteinase 3 (MMP-3) was high. She was diagnosed with RS3PE syndrome, and treatment with prednisolone (15 mg/d) was started. One week after prednisolone treatment initiation, CRP decreased to negative, and joint pain was almost completely resolved. However, hand stiffness persisted, and MMP-3 level was still high. Thus, prednisolone dose was increased to 20 mg/d, and the stiffness resolved. Twenty days after treatment initiation, MMP-3 was normalized. MMP-3 was more indicative of RS3PE syndrome symptoms than CRP. Thus, MMP-3 seems to be more sensitive to RS3PE syndrome symptoms. PMID:29774220

Prevention of the Post-traumatic Fibrotic Response in Joints

DTIC Science & Technology

2014-10-01

JJ, Wolman M. Aging of wound healing in an experimental model in mice. The American journal of forensic medicine and pathology . 1988; 9(4):310-2...SUPPLEMENTARY NOTES 14. ABSTRACT The ongoing study addresses the critical clinical problem of posttraumatic joint stiffness, a pathology that reduces...study is that pathological fibrotic response of injured joint tissues may be limited by targeting the formation of collagen fibrils, a main component

Fundamental Principles of Tremor Propagation in the Upper Limb.

PubMed

Davidson, Andrew D; Charles, Steven K

2017-04-01

Although tremor is the most common movement disorder, there exist few effective tremor-suppressing devices, in part because the characteristics of tremor throughout the upper limb are unknown. To clarify, optimally suppressing tremor requires a knowledge of the mechanical origin, propagation, and distribution of tremor throughout the upper limb. Here we present the first systematic investigation of how tremor propagates between the shoulder, elbow, forearm, and wrist. We simulated tremor propagation using a linear, time-invariant, lumped-parameter model relating joint torques and the resulting joint displacements. The model focused on the seven main degrees of freedom from the shoulder to the wrist and included coupled joint inertia, damping, and stiffness. We deliberately implemented a simple model to focus first on the most basic effects. Simulating tremorogenic joint torque as a sinusoidal input, we used the model to establish fundamental principles describing how input parameters (torque location and frequency) and joint impedance (inertia, damping, and stiffness) affect tremor propagation. We expect that the methods and principles presented here will serve as the groundwork for future refining studies to understand the origin, propagation, and distribution of tremor throughout the upper limb in order to enable the future development of optimal tremor-suppressing devices.

Fundamental Principles of Tremor Propagation in the Upper Limb

PubMed Central

Davidson, Andrew D.; Charles, Steven K.

2017-01-01

Although tremor is the most common movement disorder, there exist few effective tremor-suppressing devices, in part because the characteristics of tremor throughout the upper limb are unknown. To clarify, optimally suppressing tremor requires a knowledge of the mechanical origin, propagation, and distribution of tremor throughout the upper limb. Here we present the first systematic investigation of how tremor propagates between the shoulder, elbow, forearm, and wrist. We simulated tremor propagation using a linear, time-invariant, lumped-parameter model relating joint torques and the resulting joint displacements. The model focused on the seven main degrees of freedom from the shoulder to the wrist and included coupled joint inertia, damping, and stiffness. We deliberately implemented a simple model to focus first on the most basic effects. Simulating tremorogenic joint torque as a sinusoidal input, we used the model to establish fundamental principles describing how input parameters (torque location and frequency) and joint impedance (inertia, damping, and stiffness) affect tremor propagation. We expect that the methods and principles presented here will serve as the groundwork for future refining studies to understand the origin, propagation, and distribution of tremor throughout the upper limb in order to enable the future development of optimal tremor-suppressing devices. PMID:27957608

The effects of range-of-motion therapy on the plantar pressures of patients with diabetes mellitus.

PubMed

Goldsmith, Jon R; Lidtke, Roy H; Shott, Susan

2002-10-01

A randomized controlled study of 19 patients with diabetes mellitus (10 men, 9 women) was undertaken to determine the effects of home exercise therapy on joint mobility and plantar pressures. Of the 19 subjects, 9 subjects performed unsupervised active and passive range-of-motion exercises of the joints in their feet. Each subject was evaluated for joint stiffness and peak plantar pressures at the beginning and conclusion of the study. After only 1 month of therapy, a statistically significant average decrease of 4.2% in peak plantar pressures was noted in the subjects performing the range-of-motion exercises. In the control group, an average increase of 4.4% in peak plantar pressures was noted. Although the joint mobility data revealed no statistically significant differences between the groups, there was a trend for a decrease in joint stiffness in the treatment group. The results of this study demonstrate that an unsupervised range-of-motion exercise program can reduce peak plantar pressures in the diabetic foot. Given that high plantar pressures have been linked to diabetic neuropathic ulceration, it may be possible to reduce the risk of such ulceration with this therapy.

A new mathematical neck model for a low-velocity rear-end impact dummy: evaluation of components influencing head kinematics.

PubMed

Linder, A

2000-03-01

A mathematical model of a new rear-end impact dummy neck was implemented using MADYMO. The main goal was to design a model with a human-like response of the first extension motion in the crash event. The new dummy neck was modelled as a series of rigid bodies (representing the seven cervical vertebrae and the uppermost thoracic element, T1) connected by pin joints, and supplemented by two muscle substitutes. The joints had non-linear stiffness characteristics and the muscle elements possessed both elastic stiffness and damping properties. The new model was compared with two neck models with the same number of vertebrae, but without muscle substitutes. The properties of the muscle substitutes and the need of these were evaluated by using three different modified neck models. The motion of T1 in the simulations was prescribed using displacement data obtained from volunteer tests. In a sensitivity analysis of the mathematical model the influence of different factors on the head-neck kinematics was evaluated. The neck model was validated against kinematics data from volunteer tests: linear displacement, angular displacement, and acceleration of the head relative to the upper torso at 7 km/h velocity change. The response of the new model was within the corridor of the volunteer tests for the main part of the time history plot. This study showed that a combination of elastic stiffness and damping in the muscle substitutes, together with a non-linear joint stiffness, resulted in a head-neck response similar to human volunteers, and superior to that of other tested neck models.

The immediate effects of two manual therapy techniques on ankle musculoarticular stiffness and dorsiflexion range of motion in people with chronic ankle rigidity: A randomized clinical trial.

PubMed

Hidalgo, Benjamin; Hall, Toby; Berwart, Mathilde; Biernaux, Elinor; Detrembleur, Christine

2017-12-29

Ankle rigidity is a common musculoskeletal disorder affecting the talocrural joint, which can impair weight-bearing ankle dorsiflexion (WBADF) and daily-life in people with or without history of ankle injuries. Our objective was to compare the immediate effects of efficacy of Mulligan Mobilization with Movement (MWM) and Osteopathic Mobilization (OM) for improving ankle dorsiflexion range of motion (ROM) and musculoarticular stiffness (MAS) in people with chronic ankle dorsiflexion rigidity. A randomized clinical trial with two arms. Patients were recruited by word of mouth and via social network as well as posters, and analyzed in the neuro musculoskeletal laboratory of the "Université Catholique de Louvain-la-Neuve", Brussels, Belgium. 67 men (aged 18-40 years) presenting with potential chronic non-specific and unilateral ankle mobility deficit during WBDF were assessed for eligibility and finally 40 men were included and randomly allocated to single session of either MWM or OM. Two modalities of manual therapy indicated for hypothetic immediate effects in chronic ankle dorsiflexion stiffness, i.e. MWM and OM, were applied during a single session on included patients. Comprised blinding measures of MAS with a specific electromechanical device (namely: Lehmann's device) producing passive oscillatory ankle joint dorsiflexion and with clinical measures of WBADF-ROM as well. A two-way ANOVA revealed a non-significant interaction between both techniques and time for all outcome measures. For measures of MAS: elastic-stiffness (p= 0.37), viscous-stiffness (p= 0.83), total-stiffness (p= 0.58). For WBADF-ROM: toe-wall distance (p= 0.58) and angular ROM (p= 0.68). Small effect sizes between groups were determined with Cohen's d ranging from 0.05 to 0.29. One-way ANOVA demonstrated non-significant difference and small to moderate effects sizes (d= 0.003-0.58) on all outcome measures before and after interventions within both groups. A second two-way ANOVA analyzed the effect of each intervention on the sample categorized according to injury history status, and demonstrated a significant interaction between groups and time only for viscous stiffness (p= 0.04, d=-0.55). A single session of MWM and OM targeting the talocrural joint failed to immediately improve all measures in.

Jumping into the deep-end: results from a pilot impact evaluation of a community-based aquatic exercise program.

PubMed

Barker, Anna L; Talevski, Jason; Morello, Renata T; Nolan, Genevieve A; De Silva, Renee D; Briggs, Andrew M

2016-06-01

This multi-center quasi-experimental pilot study aimed to evaluate changes in pain, joint stiffness, physical function, and quality of life over 12 weeks in adults with musculoskeletal conditions attending 'Waves' aquatic exercise classes. A total of 109 adults (mean age, 65.2 years; range, 24-93 years) with musculoskeletal conditions were recruited across 18 Australian community aquatic centers. The intervention is a peer-led, 45 min, weekly aquatic exercise class including aerobic, strength, flexibility, and balance exercises (n = 67). The study also included a control group of people not participating in Waves or other formal exercise (n = 42). Outcomes were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and EuroQoL five dimensions survey (EQ-5D) at baseline and 12 weeks. Satisfaction with Waves classes was also measured at 12 weeks. Eighty two participants (43 Waves and 39 control) completed the study protocol and were included in the analysis. High levels of satisfaction with classes were reported by Waves participants. Over 90 % of participants reported Waves classes were enjoyable and would recommend classes to others. Waves participants demonstrated improvements in WOMAC and EQ-5D scores however between-group differences did not reach statistical significance. Peer-led aquatic exercise classes appear to improve pain, joint stiffness, physical function and quality of life for people with musculoskeletal conditions. The diverse study sample is likely to have limited the power to detect significant changes in outcomes. Larger studies with an adequate follow-up period are needed to confirm effects.

Generation of the Human Biped Stance by a Neural Controller Able to Compensate Neurological Time Delay

PubMed Central

Jiang, Ping; Chiba, Ryosuke; Takakusaki, Kaoru; Ota, Jun

2016-01-01

The development of a physiologically plausible computational model of a neural controller that can realize a human-like biped stance is important for a large number of potential applications, such as assisting device development and designing robotic control systems. In this paper, we develop a computational model of a neural controller that can maintain a musculoskeletal model in a standing position, while incorporating a 120-ms neurological time delay. Unlike previous studies that have used an inverted pendulum model, a musculoskeletal model with seven joints and 70 muscular-tendon actuators is adopted to represent the human anatomy. Our proposed neural controller is composed of both feed-forward and feedback controls. The feed-forward control corresponds to the constant activation input necessary for the musculoskeletal model to maintain a standing posture. This compensates for gravity and regulates stiffness. The developed neural controller model can replicate two salient features of the human biped stance: (1) physiologically plausible muscle activations for quiet standing; and (2) selection of a low active stiffness for low energy consumption. PMID:27655271

Reliability of metatarsophalangeal and ankle joint torque measurements by an innovative device.

PubMed

Man, Hok-Sum; Leung, Aaron Kam-Lun; Cheung, Jason Tak-Man; Sterzing, Thorsten

2016-07-01

The toe flexor muscles maintain body balance during standing and provide push-off force during walking, running, and jumping. Additionally, they are important contributing structures to maintain normal foot function. Thus, weakness of these muscles may cause poor balance, inefficient locomotion and foot deformities. The quantification of metatarsophalangeal joint (MPJ) stiffness is valuable as it is considered as a confounding factor in toe flexor muscles function. MPJ and ankle joint stiffness measurement is still largely depended on manual skills as current devices do not have good control on alignment, angular joint speed and displacement during measurement. Therefore, this study introduces an innovative dynamometer and protocol procedures for MPJ and ankle Joint torque measurement with precise and reliable foot alignment, angular joint speed and displacement control. Within-day and between-day test-retest experiments on MPJ and ankle joint torque measurement were conducted on ten and nine healthy male subjects respectively. The mean peak torques of MPJ and ankle joint of between-day and within-day measurement were 1.50±0.38Nm/deg and 1.19±0.34Nm/deg. The corresponding torques of the ankle joint were 8.24±2.20Nm/deg and 7.90±3.18Nm/deg respectively. Intraclass-correlation coefficients (ICC) of averaged peak torque of both joints of between-day and within-day test-retest experiments were ranging from 0.91 to 0.96, indicating the innovative device is systematic and reliable for the measurements and can be used for multiple scientific and clinical purposes. Copyright © 2016 Elsevier B.V. All rights reserved.

Case Report: The casting motion to mobilize stiffness technique for rehabilitation after a crush and degloving injury of the hand.

PubMed

Midgley, Robyn

2016-01-01

Case report. This case report describes the use of the casting motion to mobilize stiffness (CMMS) technique in the management of a crush and degloving injury of the hand. The patient was unable to attend multiple hand therapy sessions due to geographic constraints. The CMMS technique involved the application of a nonremovable plaster of paris cast that selectively immobilizes proximal joints in an ideal position while constraining distal joints to direct desired motion over a long period. This uses active motion only. Traditional hand therapy techniques or modalities are not used. This treatment approach was beneficial to the patient as a minimum of 2 appointments per month were needed to regain functional hand use. To document the use of the CMMS technique as an effective treatment approach in the management of a crush and degloving injury of the hand. The CMMS technique was applied to the patient's left (nondominant) hand 8 weeks after injury. The technique's aim was to improve the 30° flexion deformity of the left wrist and flexion contractures of the index, middle, and ring fingers with a total active motion of 0°. Orthotic devices and traditional therapy were applied once joint stiffness was resolved, and a normal pattern of motion was reinstated. At 6 months, substantial improvement was noted in wrist as well as metacarpophalangeal and interphalangeal joints. Total active motion exceeded 170° in all fingers excellent functional outcome resulted as measured with the upper limb functional index short form-10. The upper limb functional index increased from 0% to 55% of preinjury status (or capacity) over the 18 months of therapy. Brief immobilization through casting causes certain functional losses, but these are temporary and reversible. Finger stiffness, edema, and tissue fibrosis were successfully managed with the CMMS technique without the need for attendance at multiple hand therapy sessions. Level V. Copyright © 2016 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Analytical Time-Domain Solution of Plane Wave Propagation Across a Viscoelastic Rock Joint

NASA Astrophysics Data System (ADS)

Zou, Yang; Li, Jianchun; Laloui, Lyesse; Zhao, Jian

2017-10-01

The effects of viscoelastic filled rock joints on wave propagation are of great significance in rock engineering. The solutions in time domain for plane longitudinal ( P-) and transverse ( S-) waves propagation across a viscoelastic rock joint are derived based on Maxwell and Kelvin models which are, respectively, applied to describe the viscoelastic deformational behaviour of the rock joint and incorporated into the displacement discontinuity model (DDM). The proposed solutions are verified by comparing with the previous studies on harmonic waves, which are simulated by sinusoidal incident P- and S-waves. Comparison between the predicted transmitted waves and the experimental data for P-wave propagation across a joint filled with clay is conducted. The Maxwell is found to be more appropriate to describe the filled joint. The parametric studies show that wave propagation is affected by many factors, such as the stiffness and the viscosity of joints, the incident angle and the duration of incident waves. Furthermore, the dependences of the transmission and reflection coefficients on the specific joint stiffness and viscosity are different for the joints with Maxwell and Kelvin behaviours. The alternation of the reflected and transmitted waveforms is discussed, and the application scope of this study is demonstrated by an illustration of the effects of the joint thickness. The solutions are also extended for multiple parallel joints with the virtual wave source method and the time-domain recursive method. For an incident wave with arbitrary waveform, it is convenient to adopt the present approach to directly calculate wave propagation across a viscoelastic rock joint without additional mathematical methods such as the Fourier and inverse Fourier transforms.

Composite sizing and ply orientation for stiffness requirements using a large finite element structural model

NASA Technical Reports Server (NTRS)

Radovcich, N. A.; Gentile, D. P.

1989-01-01

A NASTRAN bulk dataset preprocessor was developed to facilitate the integration of filamentary composite laminate properties into composite structural resizing for stiffness requirements. The NASCOMP system generates delta stiffness and delta mass matrices for input to the flutter derivative program. The flutter baseline analysis, derivative calculations, and stiffness and mass matrix updates are controlled by engineer defined processes under an operating system called CBUS. A multi-layered design variable grid system permits high fidelity resizing without excessive computer cost. The NASCOMP system uses ply layup drawings for basic input. The aeroelastic resizing for stiffness capability was used during an actual design exercise.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukuoka, T.

Many studies have been devoted to investigate how the maximum stress occurring in the bolted joint could be reduced. Patterson and Kenny suggest that a modified nut with a straight bevel at the bearing surface is effective. However, they only dealt with M30, and estimations on the nut geometry had not been necessarily sufficient. In this study, an extensive finite element approach for solving general multi-body contact problem is proposed by incorporating a regularization method into stiffness matrices with singularity involved; thus, numerical analyses are executed to accurately determine the optimal shape of the modified nut for various design factors.more » A modified nut with a curved bevel is also treated, and it is concluded that the modified nuts are significantly effective for bolts with larger nominal diameter and fine pitch, and are practically useful compared to pitch modification and tapered thread methods.« less

A Novel Concept for Safe, Stiffness-Controllable Robot Links.

PubMed

Stilli, Agostino; Wurdemann, Helge A; Althoefer, Kaspar

2017-03-01

The recent decade has seen an astounding increase of interest and advancement in a new field of robotics, aimed at creating structures specifically for the safe interaction with humans. Softness, flexibility, and variable stiffness in robotics have been recognized as highly desirable characteristics for many applications. A number of solutions were proposed ranging from entirely soft robots (such as those composed mainly from soft materials such as silicone), via flexible continuum and snake-like robots, to rigid-link robots enhanced by joints that exhibit an elastic behavior either implemented in hardware or achieved purely by means of intelligent control. Although these are very good solutions paving the path to safe human-robot interaction, we propose here a new approach that focuses on creating stiffness controllability for the linkages between the robot joints. This article proposes a replacement for the traditionally rigid robot link-the new link is equipped with an additional capability of stiffness controllability. With this added feature, a robot can accurately carry out manipulation tasks (high stiffness), but can virtually instantaneously reduce its stiffness when a human is nearby or in contact with the robot. The key point of the invention described here is a robot link made of an airtight chamber formed by a soft and flexible, but high-strain resistant combination of a plastic mesh and silicone wall. Inflated with air to a high pressure, the mesh silicone chamber behaves like a rigid link; reducing the air pressure, softens the link and rendering the robot structure safe. This article investigates a number of link prototypes and shows the feasibility of the new concept. Stiffness tests have been performed, showing that a significant level of stiffness can be achieved-up to 40 N reaction force along the axial direction, for a 25-mm-diameter sample at 60 kPa, at an axial deformation of 5 mm. The results confirm that this novel concept to linkages for robot manipulators exhibits the beam-like behavior of traditional rigid links when fully pressurized and significantly reduced stiffness at low pressure. The proposed concept has the potential to easily create safe robots, augmenting traditional robot designs.

Total knee replacement with tibial tubercle osteotomy in rheumatoid patients with stiff knee.

PubMed

Eid, Ahmed Salem; Nassar, Wael Ahmed Mohamed; Fayyad, Tamer Abdelmeguid Mohamed

2016-11-01

Total knee arthroplasty (TKA) is a well-proven modality that can provide pain relief and restore mobility for rheumatoid arthritis (RA) patients with advanced joint destruction. Patellar ligament avulsion, especially in presence of poor bone quality and knee stiffness, is one of the special considerations that must be addressed in this unique population of patients. This study aimed to determine the functional results in a series of rheumatoid patients with stiff knee and end-stage joint destruction who underwent tibial tubercle osteotomy during TKA. Twenty-three knees in 20 patients (16 women; four men) at a mean age of 54 years with end-stage arthritis and knee stiffness due to RA were operated upon for TKA using tibial tubercle osteotomy as a step during the operation. Patients were reviewed clinically and radiographically with a minimum follow-up of two years. Complications were noted. Hospital for Special Surgery (HSS) score was recorded pre-operatively and at six and 12 months postoperatively. Union occurred at the osteotomy site in 21 of 23 cases. One case had deep venous thrombosis (DVT). There was no infection or periprosthetic fracture, and at last follow-up, no patient required revision. HSS score improved from 46 (15-60) pre-operatively to 85 (71-96) post-operatively. Tibial tubercle osteotomy during TKA in patients with RA and stiff knee is technically demanding yet proved to be effective in improving post-operative range of movement and minimising the complication of patellar ligament avulsion.

Virion stiffness regulates immature HIV-1 entry

PubMed Central

2013-01-01

Background Human immunodeficiency virus type 1 (HIV-1) undergoes a protease-mediated maturation process that is required for its infectivity. Little is known about how the physical properties of viral particles change during maturation and how these changes affect the viral lifecycle. Using Atomic Force Microscopy (AFM), we previously discovered that HIV undergoes a “stiffness switch”, a dramatic reduction in particle stiffness during maturation that is mediated by the viral Envelope (Env) protein. Results In this study, we show that transmembrane-anchored Env cytoplasmic tail (CT) domain is sufficient to regulate the particle stiffness of immature HIV-1. Using this construct expressed in trans with viral Env lacking the CT domain, we show that increasing particle stiffness reduces viral entry activity in immature virions. A similar effect was also observed for immature HIV-1 pseudovirions containing Env from vesicular stomatitis virus. Conclusions This linkage between particle stiffness and viral entry activity illustrates a novel level of regulation for viral replication, providing the first evidence for a biological role of virion physical properties and suggesting a new inhibitory strategy. PMID:23305456

Experimental joint immobilization in guinea pigs. Effects on the knee joint

NASA Technical Reports Server (NTRS)

Marcondesdesouza, J. P.; Machado, F. F.; Sesso, A.; Valeri, V.

1980-01-01

In young and adult guinea pigs, the aftermath experimentally induced by the immobilization of the knee joint in hyperextended forced position was studied. Joint immobilization which varied from one to nine weeks was attained by plaster. Eighty knee joints were examined macro and microscopically. Findings included: (1) muscular hypotrophy and joint stiffness in all animals, directly proportional to the length of immobilization; (2) haemoarthrosis in the first week; (3) intra-articular fibrous tissue proliferation ending up with fibrous ankylosis; (4) hyaline articular cartilage erosions; (5) various degrees of destructive menisci changes. A tentative explanation of the fibrous tissue proliferation and of the cartilage changes is offered.

Four Weeks of Balance Training does not Affect Ankle Joint Stiffness in Subjects with Unilateral Chronic Ankle Instability

PubMed Central

Jain, Tarang Kumar; Wauneka, Clayton N.; Liu, Wen

2016-01-01

Background Balance training has been shown to be effective in preventing ankle sprain recurrences in subjects with chronic ankle instability (CAI) but the biomechanical pathways underlying the clinical outcomes are still unknown. This study was conducted to determine if a 4-week balance training intervention can alter the mechanical characteristics in ankles with CAI. Methods Twenty-two recreationally active subjects with unilateral CAI were randomized to either a control (n = 11, 35.1 ± 9.3 years) or intervention (n = 11, 33.5 ± 6.6 years) group. Subjects in the intervention group were trained on the affected limb with static and dynamic components using a Biodex balance stability system for 4-weeks. The ankle joint stiffness and neutral zone in inversion and eversion directions on the involved and uninvolved limbs was measured at baseline and post-intervention using a dynamometer. Results At baseline, the mean values of the inversion stiffness (0.69 ± 0.37 Nm/degree) in the involved ankle was significantly lower (p < 0.011, 95% CI [0.563, 0.544]) than that of uninvolved contralateral ankle (0.99 ± 0.41 Nm/degree). With the available sample size, the eversion stiffness, inversion neutral zone, and eversion neutral zone were not found to be significantly different between the involved and uninvolved contralateral ankles. The 4-week balance training intervention failed to show any significant effect on the passive ankle stiffness and neutral zones in inversion and eversion. Conclusion Decreased inversion stiffness in the involved chronic unstable ankle was found that of uninvolved contralateral ankle. The 4-week balance training program intervention was ineffective in altering the mechanical characteristics of ankles with CAI. Level of evidence Randomized controlled clinical trial; Level of evidence, 1. PMID:27642647

In vivo biomechanical measurement and haptic simulation of portal placement procedure in shoulder arthroscopic surgery

PubMed Central

Chae, Sanghoon; Jung, Sung-Weon

2018-01-01

A survey of 67 experienced orthopedic surgeons indicated that precise portal placement was the most important skill in arthroscopic surgery. However, none of the currently available virtual reality simulators include simulation / training in portal placement, including haptic feedback of the necessary puncture force. This study aimed to: (1) measure the in vivo force and stiffness during a portal placement procedure in an actual operating room and (2) implement active haptic simulation of a portal placement procedure using the measured in vivo data. We measured the force required for port placement and the stiffness of the joint capsule during portal placement procedures performed by an experienced arthroscopic surgeon. Based on the acquired mechanical property values, we developed a cable-driven active haptic simulator designed to train the portal placement skill and evaluated the validity of the simulated haptics. Ten patients diagnosed with rotator cuff tears were enrolled in this experiment. The maximum peak force and joint capsule stiffness during posterior portal placement procedures were 66.46 (±10.76N) and 2560.82(±252.92) N/m, respectively. We then designed an active haptic simulator using the acquired data. Our cable-driven mechanism structure had a friction force of 3.763 ± 0.341 N, less than 6% of the mean puncture force. Simulator performance was evaluated by comparing the target stiffness and force with the stiffness and force reproduced by the device. R-squared values were 0.998 for puncture force replication and 0.902 for stiffness replication, indicating that the in vivo data can be used to implement a realistic haptic simulator. PMID:29494691

Passive stiffness of coupled wrist and forearm rotations.

PubMed

Drake, Will B; Charles, Steven K

2014-09-01

Coordinated movement requires that the neuromuscular system account and compensate for movement dynamics. One particularly complex aspect of movement dynamics is the interaction that occurs between degrees of freedom (DOF), which may be caused by inertia, damping, and/or stiffness. During wrist rotations, the two DOF of the wrist (flexion-extension and radial-ulnar deviation, FE and RUD) are coupled through interaction torques arising from passive joint stiffness. One important unanswered question is whether the DOF of the forearm (pronation-supination, PS) is coupled to the two DOF of the wrist. Answering this question, and understanding the dynamics of wrist and forearm rotations in general, requires knowledge of the stiffness encountered during rotations involving all three DOF (PS, FE, and RUD). Here we present the first-ever measurement of the passive stiffness encountered during simultaneous wrist and forearm rotations. Using a wrist and forearm robot, we measured coupled wrist and forearm stiffness in 10 subjects and present it as a 3-by-3 stiffness matrix. This measurement of passive wrist and forearm stiffness will enable future studies investigating the dynamics of wrist and forearm rotations, exposing the dynamics for which the neuromuscular system must plan and compensate during movements involving the wrist and forearm.

The effect of short-term isometric training on core/torso stiffness.

PubMed

Lee, Benjamin; McGill, Stuart

2017-09-01

"Core" exercise is a basic part of many physical training regimens with goals ranging from rehabilitation of spine and knee injuries to improving athletic performance. Core stiffness has been proposed to perform several functions including reducing pain by minimising joint micro-movements, and enhancing strength and speed performance. This study probes the links between a training approach and immediate but temporary changes in stiffness. Passive and active stiffness was measured on 24 participants; 12 having little to no experience in core training (inexperienced), and the other 12 being athletes experienced to core training methods; before and after a 15 min bout of isometric core exercises. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed via a quick release mechanism. Short-term isometric core training increased passive and active stiffness in most directions for both inexperienced and experienced participants, passive left lateral bend among experienced participants being the exception (P < 0.05). There was no difference between the inexperienced and experienced groups. The results confirm that the specific isometric training exercise approach tested here can induce immediate changes in core stiffness, in this case following a single session. This may influence performance and injury resilience for a brief period.

Pulsed radiofrequency of the composite nerve supply to the knee joint as a new technique for relieving osteoarthritic pain: a preliminary report.

PubMed

Vas, Lakshmi; Pai, Renuka; Khandagale, Nishigandha; Pattnaik, Manorama

2014-01-01

We report a new technique for pulsed radiofrequency (PRF) of the entire nerve supply of the knee as an option in treating osteoarthritis (OA) of knee. We targeted both sensory and motor nerves supplying all the structures around the knee: joint, muscles, and skin to address the entire nociception and stiffness leading to peripheral and central sensitization in osteoarthritis. Ten patients with pain, stiffness, and loss of function in both knees were treated with ultrasonography (USG) guided PRF of saphenous, tibial, and common peroneal nerves along with subsartorial, peripatellar, and popliteal plexuses. USG guided PRF of the femoral nerve was also done to address the innervation of the quadriceps muscle. Assessment of pain (Numerical Rating Scale [NRS], pain DETECT, knee function [Western Ontario and McMaster Universities Osteoarthritis Index- WOMAC]) were documented pre and post PRF at 3 and 6 months. Knee radiographs (Kellgren-Lawrence [K-L] grading) were done before PRF and one week later. All the patients showed a sustained improvement of NRS, pain DETECT, and WOMAC at 3 and 6 months. The significant improvement of patellar position and tibio-femoral joint space was concordant with the patient's reporting of improvement in stiffness and pain. The sustained pain relief and muscle relaxation enabled the patients to optimize physiotherapy thereby improving endurance training to include the daily activities of life. We conclude that OA knee pain is a product of neuromyopathy and that PRF of the sensory and motor nerves appeared to be a safe, effective, and minimally invasive technique. The reduction of pain and stiffness improved the knee function and probably reduced the peripheral and central sensitization.

Dynamic Analyses Including Joints Of Truss Structures

NASA Technical Reports Server (NTRS)

Belvin, W. Keith

1991-01-01

Method for mathematically modeling joints to assess influences of joints on dynamic response of truss structures developed in study. Only structures with low-frequency oscillations considered; only Coulomb friction and viscous damping included in analysis. Focus of effort to obtain finite-element mathematical models of joints exhibiting load-vs.-deflection behavior similar to measured load-vs.-deflection behavior of real joints. Experiments performed to determine stiffness and damping nonlinearities typical of joint hardware. Algorithm for computing coefficients of analytical joint models based on test data developed to enable study of linear and nonlinear effects of joints on global structural response. Besides intended application to large space structures, applications in nonaerospace community include ground-based antennas and earthquake-resistant steel-framed buildings.

The effect of postoperative passive motion on rotator cuff healing in a rat model.

PubMed

Peltz, Cathryn D; Dourte, Leann M; Kuntz, Andrew F; Sarver, Joseph J; Kim, Soung-Yon; Williams, Gerald R; Soslowsky, Louis J

2009-10-01

Surgical repairs of torn rotator cuff tendons frequently fail. Immobilization has been shown to improve tissue mechanical properties in an animal model of rotator cuff repair, and passive motion has been shown to improve joint mechanics in animal models of flexor tendon repair. Our objective was to determine if daily passive motion would improve joint mechanics in comparison with continuous immobilization in a rat rotator cuff repair model. We hypothesized that daily passive motion would result in improved passive shoulder joint mechanics in comparison with continuous immobilization initially and that there would be no differences in passive joint mechanics or insertion site mechanical properties after four weeks of remobilization. A supraspinatus injury was created and was surgically repaired in sixty-five Sprague-Dawley rats. Rats were separated into three postoperative groups (continuous immobilization, passive motion protocol 1, and passive motion protocol 2) for two weeks before all underwent a remobilization protocol for four weeks. Serial measurements of passive shoulder mechanics (internal and external range of motion and joint stiffness) were made before surgery and at two and six weeks after surgery. After the animals were killed, collagen organization and mechanical properties of the tendon-to-bone insertion site were determined. Total range of motion for both passive motion groups (49% and 45% of the pre-injury values) was less than that for the continuous immobilization group (59% of the pre-injury value) at two weeks and remained significantly less following four weeks of remobilization exercise. Joint stiffness at two weeks was increased for both passive motion groups in comparison with the continuous immobilization group. At both two and six weeks after repair, internal range of motion was significantly decreased whereas external range of motion was not. There were no differences between the groups in terms of collagen organization or mechanical properties. In this model, immediate postoperative passive motion was found to be detrimental to passive shoulder mechanics. We speculate that passive motion results in increased scar formation in the subacromial space, thereby resulting in decreased range of motion and increased joint stiffness. Passive motion had no effect on collagen organization or tendon mechanical properties measured six weeks after surgery.

Reducing vibration transfer from power plants by active methods

NASA Astrophysics Data System (ADS)

Kiryukhin, A. V.; Milman, O. O.; Ptakhin, A. V.

2017-12-01

The possibility of applying the methods of active damping of vibration and pressure pulsations for reducing their transfer from power plants into the environment, the seating, and the industrial premises are considered. The results of experimental works implemented by the authors on the active broadband damping of vibration and dynamic forces after shock-absorption up to 15 dB in the frequency band up to 150 Hz, of water pressure pulsations in the pipeline up to 20 dB in the frequency band up to 600 Hz, and of spatial low-frequency air noise indoors of a diesel generator at discrete frequency up to 20 dB are presented. It is shown that a reduction of vibration transfer through a vibration-isolating junction (expansion joints) of pipelines with liquid is the most complicated and has hardly been developed so far. This problem is essential for vibration isolation of power equipment from the seating and the environment through pipelines with water and steam in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. For improving efficiency, reducing the energy consumption, and decreasing the overall dimensions of equipment, it is advisable to combine the work of an active system with passive damping means, the use of which is not always sufficient. The executive component of the systems of active damping should be placed behind the vibration isolators (expansion joints). It is shown that the existence of working medium and connection of vibration with pressure pulsations in existing designs of pipeline expansion joints lead to growth of vibration stiffness of the expansion joint with the environment by two and more orders as compared with the static stiffness and makes difficulties for using the active methods. For active damping of vibration transfer through expansion joints of pipelines with a liquid, it is necessary to develop expansion joint structures with minimal connection of vibrations and pulsations and minimal vibration stiffness in the specified frequency range. The example of structure of such expansion joint and its test results are presented.

Resonant Column Tests and Nonlinear Elasticity in Simulated Rocks

NASA Astrophysics Data System (ADS)

Sebastian, Resmi; Sitharam, T. G.

2018-01-01

Rocks are generally regarded as linearly elastic even though the manifestations of nonlinearity are prominent. The variations of elastic constants with varying strain levels and stress conditions, disagreement between static and dynamic moduli, etc., are some of the examples of nonlinear elasticity in rocks. The grain-to-grain contact, presence of pores and joints along with other compliant features induce the nonlinear behavior in rocks. The nonlinear elastic behavior of rocks is demonstrated through resonant column tests and numerical simulations in this paper. Resonant column tests on intact and jointed gypsum samples across varying strain levels have been performed in laboratory and using numerical simulations. The paper shows the application of resonant column apparatus to obtain the wave velocities of stiff samples at various strain levels under long wavelength condition, after performing checks and incorporating corrections to the obtained resonant frequencies. The numerical simulation and validation of the resonant column tests using distinct element method are presented. The stiffness reductions of testing samples under torsional and flexural vibrations with increasing strain levels have been analyzed. The nonlinear elastic behavior of rocks is reflected in the results, which is enhanced by the presence of joints. The significance of joint orientation and influence of joint spacing during wave propagation have also been assessed and presented using the numerical simulations. It has been found that rock joints also exhibit nonlinear behavior within the elastic limit.

An Analytical Model for Two-Order Asperity Degradation of Rock Joints Under Constant Normal Stiffness Conditions

NASA Astrophysics Data System (ADS)

Li, Yingchun; Wu, Wei; Li, Bo

2018-05-01

Jointed rock masses during underground excavation are commonly located under the constant normal stiffness (CNS) condition. This paper presents an analytical formulation to predict the shear behaviour of rough rock joints under the CNS condition. The dilatancy and deterioration of two-order asperities are quantified by considering the variation of normal stress. We separately consider the dilation angles of waviness and unevenness, which decrease to zero as the normal stress approaches the transitional stress. The sinusoidal function naturally yields the decay of dilation angle as a function of relative normal stress. We assume that the magnitude of transitional stress is proportionate to the square root of asperity geometric area. The comparison between the analytical prediction and experimental data shows the reliability of the analytical model. All the parameters involved in the analytical model possess explicit physical meanings and are measurable from laboratory tests. The proposed model is potentially practicable for assessing the stability of underground structures at various field scales.

The Load Distribution in Bolted or Riveted Joints in Light-Alloy Structures

NASA Technical Reports Server (NTRS)

Vogt, F.

1947-01-01

This report contains a theoretical discussion of the load distribution in bolted or riveted joints in light-alloy structures which is applicable not only for loads below the limit of proportionality but also for loads above this limit. The theory is developed for double and single shear joints. The methods given are illustrated by numerical examples and the values assumed for the bolt (or rivet) stiffnesses are based partly on theory and partly on known experimental values. It is shown that the load distribution does not vary greatly with the bolt (or rivet) stiffnesses and that for design purposes it is usually sufficient to know their order of magnitude. The theory may also be directly used for spot-welded structures and, with small modifications, for seam-welded structures, The computational work involved in the methods described is simple and may be completed in a reasonable time for most practical problems. A summary of earlier theoretical and experimental investigations on the subject is included in the report.

Time-dependent behavior of rough discontinuities under shearing conditions

NASA Astrophysics Data System (ADS)

Wang, Zhen; Shen, Mingrong; Ding, Wenqi; Jang, Boan; Zhang, Qingzhao

2018-02-01

The mechanical properties of rocks are generally controlled by their discontinuities. In this study, the time-dependent behavior of rough artificial joints under shearing conditions was investigated. Based on Barton’s standard profile lines, samples with artificial joint surfaces were prepared and used to conduct the shear and creep tests. The test results showed that the shear strength of discontinuity was linearly related to roughness, and subsequently an empirical equation was established. The long-term strength of discontinuity can be identified using the inflection point of the isocreep-rate curve, and it was linearly related to roughness. Furthermore, the ratio of long-term and instantaneous strength decreased with the increase of roughness. The shear-stiffness coefficient increased with the increase of shear rate, and the influence of shear rate on the shear stiffness coefficient decreased with the decrease of roughness. Further study of the mechanism revealed that these results could be attributed to the different time-dependent behavior of intact and joint rocks.

Reconstruction of shifting elbow joint compliant characteristics during fast and slow movements.

PubMed

Latash, M L; Gottlieb, G L

1991-01-01

The purpose of this study was to experimentally investigate the applicability of the equilibrium-point hypothesis to the dynamics of single-joint movements. Subjects were trained to perform relatively slow (movement time 600-1000 ms) or fast (movement time 200-300 ms) single-joint elbow flexion movements against a constant extending torque bias. They were instructed to reproduce the same time pattern of central motor command for a series of movements when the external torque could slowly and unpredictably increase, decrease, or remain constant. For fast movements, the total muscle torque was calculated as a sum of external and inertial components. Analysis of the data allowed reconstruction of the elbow joint compliant characteristics at different times during execution of the learned motor command. "Virtual" trajectories of the movements, representing time-varying changes in a central control parameter, were reconstructed and compared with the "actual" trajectories. For slow movements, the actual trajectories lagged behind the virtual ones. There were no consistent changes in the joint stiffness during slow movements. Similar analysis of experiments without voluntary movements demonstrated a lack of changes in the central parameters, supporting the assumption that the subjects were able to keep the same central motor command in spite of externally imposed unexpected torque perturbations. For the fast movements, the virtual trajectories were N-shaped, and the joint stiffness demonstrated a considerable increase near the middle of the movement. These findings contradict an hypothesis of monotonic joint compliant characteristic translation at a nearly constant rate during such movements.

A randomised controlled trial of intra-articular corticosteroid injection of the carpometacarpal joint of the thumb in osteoarthritis

PubMed Central

Meenagh, G; Patton, J; Kynes, C; Wright, G

2004-01-01

Objective: To investigate the efficacy of corticosteroid injections into the carpometacarpal joint of the thumb (CMCJ) in patients with osteoarthritis. Design: A double blind, randomised controlled trial using 40 hospital referred patients with CMCJ osteoarthritis who received intra-articular injections of 5 mg triamcinolone hexacetonide (0.25 ml) or sterile 0.9% saline (0.25 ml). Injections were given under imaging control. Main outcome measures: The primary outcome was improvement in a pain visual analogue score (VAS) of 20% at 24 weeks. In addition patients were assessed at 4, 12, and 24 weeks for joint stiffness, joint tenderness, and physician and patient global assessments. Hand radiographs were evaluated for the degree of CMC joint space narrowing and marginal osteophytes according to the OARSI atlas. Results: Baseline clinical variables were not significantly different between the two treatment groups. There was no improvement in the VAS of pain at 24 weeks. At each assessment point there was no significant difference between the steroid and placebo groups in median values for joint stiffness, joint tenderness, or patient and physician global assessments. Non-parametric analysis of each group individually revealed statistically significant improvements in patient and physician global assessments at weeks 4, 12, and 24 in the placebo group and at weeks 4 and 12 in the steroid group. Conclusions: No clinical benefit was gained from intra-articular steroid injection to the CMCJ in moderate to severe osteoarthritis compared with placebo injection. PMID:15361383

Preliminary Assessment of a Compliant Gait Exoskeleton.

PubMed

Cestari, Manuel; Sanz-Merodio, Daniel; Garcia, Elena

2017-06-01

Current commercial wearable gait exoskeletons contain joints with stiff actuators that cannot adapt to unpredictable environments. These actuators consume a significant amount of energy, and their stiffness may not be appropriate for safe human-machine interactions. Adjustable compliant actuators are being designed and implemented because of their ability to minimize large forces due to shocks, to safely interact with the user, and to store and release energy in passive elastic elements. Introduction of such compliant actuation in gait exoskeletons, however, has been limited by the larger power-to-weight and volume ratio requirement. This article presents a preliminary assessment of the first compliant exoskeleton for children. Compliant actuation systems developed by our research group were integrated into the ATLAS exoskeleton prototype. The resulting device is a compliant exoskeleton, the ATLAS-C prototype. The exoskeleton is coupled with a special standing frame to provide balance while allowing a semi-natural gait. Experiments show that when comparing the behavior of the joints under different stiffness conditions, the inherent compliance of the implemented actuators showed natural adaptability during the gait cycle and in regions of shock absorption. Torque tracking of the joint is achieved, identifying the areas of loading response. The implementation of a state machine in the control of knee motion allowed reutilization of the stored energy during deflection at the end of the support phase to partially propel the leg and achieve a more natural and free swing.

Flurbiprofen

MedlinePlus

Flurbiprofen is used to relieve pain, tenderness, swelling, and stiffness caused by osteoarthritis (arthritis caused by a ... by swelling of the lining of the joints). Flurbiprofen is in a class of medications called NSAIDs. ...

Classical and numerical approaches to determining V-section band clamp axial stiffness

NASA Astrophysics Data System (ADS)

Barrans, Simon M.; Khodabakhshi, Goodarz; Muller, Matthias

2015-01-01

V-band clamp joints are used in a wide range of applications to connect circular flanges, for ducts, pipes and the turbocharger housing. Previous studies and research on V-bands are either purely empirical or analytical with limited applicability on the variety of V-band design and working conditions. In this paper models of the V-band are developed based on the classical theory of solid mechanics and the finite element method to study the behaviour of theV-bands under axial loading conditions. The good agreement between results from the developed FEA and the classical model support the suitability of the latter to modelV-band joints with diameters greater than 110mm under axial loading. The results from both models suggest that the axial stiffness for thisV-band cross section reaches a peak value for V-bands with radius of approximately 150 mmacross a wide range of coefficients of friction. Also, it is shown that the coefficient of friction and the wedge angle have a significant effect on the axial stiffness of V-bands.

Sensitivity of biomechanical outcomes to independent variations of hindfoot and forefoot stiffness in foot prostheses.

PubMed

Adamczyk, Peter Gabriel; Roland, Michelle; Hahn, Michael E

2017-08-01

Many studies have reported the effects of different foot prostheses on gait, but most results cannot be generalized because the prostheses' properties are seldom reported. We varied hindfoot and forefoot stiffness in an experimental foot prosthesis, in increments of 15N/mm, and tested the parametric effects of these variations on treadmill walking in unilateral transtibial amputees, at speeds from 0.7 to 1.5m/s. We computed outcomes such as prosthesis energy return, center of mass (COM) mechanics, ground reaction forces, and joint mechanics, and computed their sensitivity to component stiffness. A stiffer hindfoot led to reduced prosthesis energy return, increased ground reaction force (GRF) loading rate, and greater stance-phase knee flexion and knee extensor moment. A stiffer forefoot resulted in reduced prosthetic-side ankle push-off and COM push-off work, and increased knee extension and knee flexor moment in late stance. The sensitivity parameters obtained from these tests may be useful in clinical prescription and further research into compensatory mechanisms of joint function. Copyright © 2017 Elsevier B.V. All rights reserved.

A target field design of open multi-purpose RF coil for musculoskeletal MR imaging at 3T.

PubMed

Gao, Fei; Zhang, Rui; Zhou, Diange; Wang, Xiaoying; Huang, Kefu; Zhang, Jue

2016-10-01

Musculoskeletal MR imaging under multi-angle situations plays an increasingly important role in assessing joint and muscle tissues system. However, there are still limitations due to the closed structures of most conventional RF coils. In this study, a time-harmonic target-field method was employed to design open multi-purpose coil (OMC) for multi-angle musculoskeletal MR imaging. The phantom imaging results suggested that the proposed OMC could achieve homogeneously distributed magnetic field and high signal-to-noise ratio (SNR) of 239.04±0.83 in the region of interest (ROI). The maximum temperature in the heating hazard test was 16°C lower than the standard regulation, which indicated the security of the designed OMC. Furthermore, to demonstrate the effectiveness of the proposed OMC for musculoskeletal MR imaging, especially for multi-angle imaging, a healthy volunteer was examined for MR imaging of elbow, ankle and knee using OMC. The in vivo imaging results showed that the proposed OMC is effective for MR imaging of musculoskeletal tissues at different body parts, with satisfied B1 field homogeneity and SNR. Moreover, the open structure of the OMC could provide a large joint movement region. The proposed open multi-purpose coil is feasible for musculoskeletal MR imaging, and potentially, it is more suitable for the evaluation of musculoskeletal tissues under multi-angle conditions. Copyright © 2016. Published by Elsevier Inc.

Real-Time Vision-Based Stiffness Mapping †.

PubMed

Faragasso, Angela; Bimbo, João; Stilli, Agostino; Wurdemann, Helge Arne; Althoefer, Kaspar; Asama, Hajime

2018-04-26

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness.

An easily implemented static condensation method for structural sensitivity analysis

NASA Technical Reports Server (NTRS)

Gangadharan, S. N.; Haftka, R. T.; Nikolaidis, E.

1990-01-01

A black-box approach to static condensation for sensitivity analysis is presented with illustrative examples of a cube and a car structure. The sensitivity of the structural response with respect to joint stiffness parameter is calculated using the direct method, forward-difference, and central-difference schemes. The efficiency of the various methods for identifying joint stiffness parameters from measured static deflections of these structures is compared. The results indicate that the use of static condensation can reduce computation times significantly and the black-box approach is only slightly less efficient than the standard implementation of static condensation. The ease of implementation of the black-box approach recommends it for use with general-purpose finite element codes that do not have a built-in facility for static condensation.

Investigation into discretization methods of the six-parameter Iwan model

NASA Astrophysics Data System (ADS)

Li, Yikun; Hao, Zhiming; Feng, Jiaquan; Zhang, Dingguo

2017-02-01

Iwan model is widely applied for the purpose of describing nonlinear mechanisms of jointed structures. In this paper, parameter identification procedures of the six-parameter Iwan model based on joint experiments with different preload techniques are performed. Four kinds of discretization methods deduced from stiffness equation of the six-parameter Iwan model are provided, which can be used to discretize the integral-form Iwan model into a sum of finite Jenkins elements. In finite element simulation, the influences of discretization methods and numbers of Jenkins elements on computing accuracy are discussed. Simulation results indicate that a higher accuracy can be obtained with larger numbers of Jenkins elements. It is also shown that compared with other three kinds of discretization methods, the geometric series discretization based on stiffness provides the highest computing accuracy.

Effect of adhesive stiffness and thickness on stress distributions in structural finger joints

Treesearch

Leslie H. Groom; Robert J. Leichti

1994-01-01

Environmental, political. and socioeconomic actions over the past several years have resulted in a decreased wood supply at a time when there is an increased demand for forest products. This combination of increased demand and decreased supply has forced more emphasis on engineered wood products, a varied category usually connected with adhesively-bonded end joints, of...

Effect of adhesive stiffness and thickness on stress distributions in structural finger joints

Treesearch

Leslie H. Groom; Robert J. Leichti

1994-01-01

Environmental, political, and socioeconomic actions over the past several years have resulted in a decreased wood supply at a time when there is an increased demand for forest products. This combination of increased demand and decreased supply has forced more emphasis on engineered wood products, a varied category usually connected with adhesively-bonded end joints, of...

Joint sparse reconstruction of multi-contrast MRI images with graph based redundant wavelet transform.

PubMed

Lai, Zongying; Zhang, Xinlin; Guo, Di; Du, Xiaofeng; Yang, Yonggui; Guo, Gang; Chen, Zhong; Qu, Xiaobo

2018-05-03

Multi-contrast images in magnetic resonance imaging (MRI) provide abundant contrast information reflecting the characteristics of the internal tissues of human bodies, and thus have been widely utilized in clinical diagnosis. However, long acquisition time limits the application of multi-contrast MRI. One efficient way to accelerate data acquisition is to under-sample the k-space data and then reconstruct images with sparsity constraint. However, images are compromised at high acceleration factor if images are reconstructed individually. We aim to improve the images with a jointly sparse reconstruction and Graph-based redundant wavelet transform (GBRWT). First, a sparsifying transform, GBRWT, is trained to reflect the similarity of tissue structures in multi-contrast images. Second, joint multi-contrast image reconstruction is formulated as a ℓ 2, 1 norm optimization problem under GBRWT representations. Third, the optimization problem is numerically solved using a derived alternating direction method. Experimental results in synthetic and in vivo MRI data demonstrate that the proposed joint reconstruction method can achieve lower reconstruction errors and better preserve image structures than the compared joint reconstruction methods. Besides, the proposed method outperforms single image reconstruction with joint sparsity constraint of multi-contrast images. The proposed method explores the joint sparsity of multi-contrast MRI images under graph-based redundant wavelet transform and realizes joint sparse reconstruction of multi-contrast images. Experiment demonstrate that the proposed method outperforms the compared joint reconstruction methods as well as individual reconstructions. With this high quality image reconstruction method, it is possible to achieve the high acceleration factors by exploring the complementary information provided by multi-contrast MRI.

Estimation of tissue stiffness, reflex activity, optimal muscle length and slack length in stroke patients using an electromyography driven antagonistic wrist model.

PubMed

de Gooijer-van de Groep, Karin L; de Vlugt, Erwin; van der Krogt, Hanneke J; Helgadóttir, Áróra; Arendzen, J Hans; Meskers, Carel G M; de Groot, Jurriaan H

2016-06-01

About half of all chronic stroke patients experience loss of arm function coinciding with increased stiffness, reduced range of motion and a flexed wrist due to a change in neural and/or structural tissue properties. Quantitative assessment of these changes is of clinical importance, yet not trivial. The goal of this study was to quantify the neural and structural properties contributing to wrist joint stiffness and to compare these properties between healthy subjects and stroke patients. Stroke patients (n=32) and healthy volunteers (n=14) were measured using ramp-and-hold rotations applied to the wrist joint by a haptic manipulator. Neural (reflexive torque) and structural (connective tissue stiffness and slack lengths and (contractile) optimal muscle lengths) parameters were estimated using an electromyography driven antagonistic wrist model. Kruskal-Wallis analysis with multiple comparisons was used to compare results between healthy subjects, stroke patients with modified Ashworth score of zero and stroke patients with modified Ashworth score of one or more. Stroke patients with modified Ashworth score of one or more differed from healthy controls (P<0.05) by increased tissue stiffness, increased reflexive torque, decreased optimal muscle length and decreased slack length of connective tissue of the flexor muscles. Non-invasive quantitative analysis, including estimation of optimal muscle lengths, enables to identify neural and non-neural changes in chronic stroke patients. Monitoring these changes in time is important to understand the recovery process and to optimize treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Etodolac

MedlinePlus

Etodolac tablets, capsules, and extended-release (long-acting) tablets are used to relieve pain, tenderness, swelling, and stiffness caused ... swelling of the lining of the joints). Etodolac tablets and capsules are also used to relieve pain ...

Tolmetin

MedlinePlus

... breakdown of the lining of the joints) and rheumatoid arthritis (arthritis caused by swelling of the lining of ... pain, tenderness, swelling, and stiffness caused by juvenile rheumatoid arthritis in children 2 years of age and older. ...

Oxaprozin

MedlinePlus

... breakdown of the lining of the joints) and rheumatoid arthritis (arthritis caused by swelling of the lining of ... pain, tenderness, swelling, and stiffness caused by juvenile rheumatoid arthritis in children 6 years of age and older. ...

Meloxicam

MedlinePlus

... breakdown of the lining of the joints) and rheumatoid arthritis (arthritis caused by swelling of the lining of ... pain, tenderness, swelling, and stiffness caused by juvenile rheumatoid arthritis (a type of arthritis that affects children) in ...

Stiffness and Damping in Postural Control Increase with Age

PubMed Central

Cenciarini, Massimo; Loughlin, Patrick J.; Sparto, Patrick J.; Redfern, Mark S.

2011-01-01

Upright balance is believed to be maintained through active and passive mechanisms, both of which have been shown to be impacted by aging. A compensatory balance response often observed in older adults is increased co-contraction, which is generally assumed to enhance stability by increasing joint stiffness. We investigated the effect of aging on standing balance by fitting body sway data to a previously-developed postural control model that includes active and passive stiffness and damping parameters. Ten young (24 ± 3 y) and seven older (75 ± 5 y) adults were exposed during eyes-closed stance to perturbations consisting of lateral pseudorandom floor tilts. A least-squares fit of the measured body sway data to the postural control model found significantly larger active stiffness and damping model parameters in the older adults. These differences remained significant even after normalizing to account for different body sizes between the young and older adult groups. An age effect was also found for the normalized passive stiffness, but not for the normalized passive damping parameter. This concurrent increase in active stiffness and damping was shown to be more stabilizing than an increase in stiffness alone, as assessed by oscillations in the postural control model impulse response. PMID:19770083

Nuclear Fuel Depletion Analysis Using Matlab Software

NASA Astrophysics Data System (ADS)

Faghihi, F.; Nematollahi, M. R.

Coupled first order IVPs are frequently used in many parts of engineering and sciences. In this article, we presented a code including three computer programs which are joint with the Matlab software to solve and plot the solutions of the first order coupled stiff or non-stiff IVPs. Some engineering and scientific problems related to IVPs are given and fuel depletion (production of the 239Pu isotope) in a Pressurized Water Nuclear Reactor (PWR) are computed by the present code.

Tissue-engineered collateral ligament composite allografts for scapholunate ligament reconstruction: an experimental study.

PubMed

Endress, Ryan; Woon, Colin Y L; Farnebo, Simon J; Behn, Anthony; Bronstein, Joel; Pham, Hung; Yan, Xinrui; Gambhir, Sanjiv S; Chang, James

2012-08-01

In patients with chronic scapholunate (SL) dissociation or dynamic instability, ligament repair is often not possible, and surgical reconstruction is indicated. The ideal graft ligament would recreate both anatomical and biomechanical properties of the dorsal scapholunate ligament (dorsal SLIL). The finger proximal interphalangeal joint (PIP joint) collateral ligament could possibly be a substitute ligament. We harvested human PIP joint collateral ligaments and SL ligaments from 15 cadaveric limbs. We recorded ligament length, width, and thickness, and measured the biomechanical properties (ultimate load, stiffness, and displacement to failure) of native dorsal SLIL, untreated collateral ligaments, decellularized collateral ligaments, and SL repairs with bone-collateral ligament-bone composite collateral ligament grafts. As proof of concept, we then reseeded decellularized bone-collateral ligament-bone composite grafts with green fluorescent protein-labeled adipo-derived mesenchymal stem cells and evaluated them histologically. There was no difference in ultimate load, stiffness, and displacement to failure among native dorsal SLIL, untreated and decellularized collateral ligaments, and SL repairs with tissue-engineered collateral ligament grafts. With pair-matched untreated and decellularized scaffolds, there was no difference in ultimate load or stiffness. However, decellularized ligaments revealed lower displacement to failure compared with untreated ligaments. There was no difference in displacement between decellularized ligaments and native dorsal SLIL. We successfully decellularized grafts with recently described techniques, and they could be similarly reseeded. Proximal interphalangeal joint collateral ligament-based bone-collateral ligament-bone composite allografts had biomechanical properties similar to those of native dorsal SLIL. Decellularization did not adversely affect material properties. These tissue-engineered grafts may offer surgeons another option for reconstruction of chronic SL instability. Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

A nonlinear and fractional derivative viscoelastic model for rail pads in the dynamic analysis of coupled vehicle-slab track systems

NASA Astrophysics Data System (ADS)

Zhu, Shengyang; Cai, Chengbiao; Spanos, Pol D.

2015-01-01

A nonlinear and fractional derivative viscoelastic (FDV) model is used to capture the complex behavior of rail pads. It is implemented into the dynamic analysis of coupled vehicle-slab track (CVST) systems. The vehicle is treated as a multi-body system with 10 degrees of freedom, and the slab track is represented by a three layer Bernoulli-Euler beam model. The model for the rail pads is one dimensional, and the force-displacement relation is based on a superposition of elastic, friction, and FDV forces. This model takes into account the influences of the excitation frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, respectively. The Grünwald representation of the fractional derivatives is employed to numerically solve the fractional and nonlinear equations of motion of the CVST system by means of an explicit integration algorithm. A dynamic analysis of the CVST system exposed to excitations of rail harmonic irregularities is carried out, pointing out the stiffness and damping dependence on the excitation frequency and the displacement amplitude. The analysis indicates that the dynamic stiffness and damping of the rail pads increase with the excitation frequency while they decrease with the displacement amplitude. Furthermore, comparisons between the proposed model and ordinary Kelvin model adopted for the CVST system, under excitations of welded rail joint irregularities and of random track irregularities, are conducted in the time domain as well as in the frequency domain. The proposed model is shown to possess several modeling advantages over the ordinary Kelvin element which overestimates both the stiffness and damping features at high frequencies.

Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness.

PubMed

Mathewson, Margie A; Chambers, Henry G; Girard, Paul J; Tenenhaus, Mayer; Schwartz, Alexandra K; Lieber, Richard L

2014-12-01

Cerebral palsy (CP), caused by an injury to the developing brain, can lead to alterations in muscle function. Subsequently, increased muscle stiffness and decreased joint range of motion are often seen in patients with CP. We examined mechanical and biochemical properties of the gastrocnemius and soleus muscles, which are involved in equinus muscle contracture. Passive mechanical testing of single muscle fibers from gastrocnemius and soleus muscle of patients with CP undergoing surgery for equinus deformity showed a significant increase in fiber stiffness (p<0.01). Bundles of fibers that included their surrounding connective tissues showed no stiffness difference (p=0.28).). When in vivo sarcomere lengths were measured and fiber and bundle stiffness compared at these lengths, both fibers and bundles of patients with CP were predicted to be much stiffer in vivo compared to typically developing (TD) individuals. Interestingly, differences in fiber and bundle stiffness were not explained by typical biochemical measures such as titin molecular weight (a giant protein thought to impact fiber stiffness) or collagen content (a proxy for extracellular matrix amount). We suggest that the passive mechanical properties of fibers and bundles are thus poorly understood. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

The importance of assessment and management of morning stiffness in Asian patients with rheumatoid arthritis: Recommendations from an expert panel.

PubMed

Mok, Chi Chiu; Cha, Hoon Suk; Hidayat, Rudy; Nguyen, Lan Thi Ngoc; Perez, Emmanuel C; Ramachandran, Raveendran; Tsay, Gregory J; Yoo, Dae Hyun

2016-01-01

In patients with rheumatoid arthritis (RA), morning stiffness is linked more to functional disability and pain than disease activity, as assessed by joint counts and markers of inflammation. As part of the Asia Pacific Morning Stiffness in Rheumatoid Arthritis Expert Panel, a group of eight rheumatologists met to formulate consensus points and develop recommendations for the assessment and management of morning stiffness in RA. On the basis of a systematic literature review and expert opinion, a panel of Asian rheumatologists formulated recommendations for the assessment and medical treatment of RA. The panel agreed upon 10 consensus statements on morning stiffness, its assessment and treatment. Specifically, the panel recommended that morning stiffness, pain and impaired morning function should be routinely assessed in clinical practice. Although there are currently no validated tools for these parameters, they should be assessed as part of the patients' reported outcomes in RA. The panel also agreed on the benefits of low-dose glucocorticoids in RA, particularly for the improvement of morning stiffness. These recommendations serve to guide rheumatologists and other stakeholders on the assessment and management of morning stiffness, and help implement the treat-to-target principle in the management of RA. © 2015 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon

PubMed Central

Gill, Jaspret

2018-01-01

Individuals may stand with a range of ankle angles. Furthermore, shoes or floor surfaces may elevate or depress their heels. Here we ask how these situations impact ankle stiffness and balance. We performed two studies (each with 10 participants) in which the triceps surae, Achilles tendon and aponeurosis were stretched either passively, by rotating the support surface, or actively by leaning forward. Participants stood freely on footplates which could rotate around the ankle joint axis. Brief, small stiffness-measuring perturbations (<0.7 deg; 140 ms) were applied at intervals of 4–5 s. In study 1, participants stood at selected angles of forward lean. In study 2, normal standing was compared with passive dorsiflexion induced by 15 deg toes-up tilt of the support surface. Smaller perturbations produced higher stiffness estimates, but for all perturbation sizes stiffness increased with active torque or passive stretch. Sway was minimally affected by stretch or lean, suggesting that this did not underlie the alterations in stiffness. In quiet stance, maximum ankle stiffness is limited by the tendon. As tendon strain increases, it becomes stiffer, causing an increase in overall ankle stiffness, which would explain the effects of leaning. However, stiffness also increased considerably with passive stretch, despite a modest torque increase. We discuss possible explanations for this increase. PMID:29558469

Morphological Computation of Haptic Perception of a Controllable Stiffness Probe.

PubMed

Sornkarn, Nantachai; Dasgupta, Prokar; Nanayakkara, Thrishantha

2016-01-01

When people are asked to palpate a novel soft object to discern its physical properties such as texture, elasticity, and even non-homogeneity, they not only regulate probing behaviors, but also the co-contraction level of antagonistic muscles to control the mechanical impedance of fingers. It is suspected that such behavior tries to enhance haptic perception by regulating the function of mechanoreceptors at different depths of the fingertips and proprioceptive sensors such as tendon and spindle sensors located in muscles. In this paper, we designed and fabricated a novel two-degree of freedom variable stiffness indentation probe to investigate whether the regulation of internal stiffness, indentation, and probe sweeping velocity (PSV) variables affect the accuracy of the depth estimation of stiff inclusions in an artificial silicon phantom using information gain metrics. Our experimental results provide new insights into not only the biological phenomena of haptic perception but also new opportunities to design and control soft robotic probes.

Surgery Considerations for Adults and Children

MedlinePlus

... may be posed by complicating factors such as dental problems (skeletal fragility makes dentitia prone to fracture), cleft palate, joint stiffness or heart valve disease. Anesthesia personnel also need to be aware of ...

Biophysical Regulation of Cell Behavior—Cross Talk between Substrate Stiffness and Nanotopography

PubMed Central

Yang, Yong; Wang, Kai; Gu, Xiaosong; Leong, Kam W.

2017-01-01

The stiffness and nanotopographical characteristics of the extracellular matrix (ECM) influence numerous developmental, physiological, and pathological processes in vivo. These biophysical cues have therefore been applied to modulate almost all aspects of cell behavior, from cell adhesion and spreading to proliferation and differentiation. Delineation of the biophysical modulation of cell behavior is critical to the rational design of new biomaterials, implants, and medical devices. The effects of stiffness and topographical cues on cell behavior have previously been reviewed, respectively; however, the interwoven effects of stiffness and nanotopographical cues on cell behavior have not been well described, despite similarities in phenotypic manifestations. Herein, we first review the effects of substrate stiffness and nanotopography on cell behavior, and then focus on intracellular transmission of the biophysical signals from integrins to nucleus. Attempts are made to connect extracellular regulation of cell behavior with the biophysical cues. We then discuss the challenges in dissecting the biophysical regulation of cell behavior and in translating the mechanistic understanding of these cues to tissue engineering and regenerative medicine. PMID:29071164

Internal rotor friction instability

NASA Technical Reports Server (NTRS)

Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

1990-01-01

The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

Error Modeling and Experimental Study of a Flexible Joint 6-UPUR Parallel Six-Axis Force Sensor.

PubMed

Zhao, Yanzhi; Cao, Yachao; Zhang, Caifeng; Zhang, Dan; Zhang, Jie

2017-09-29

By combining a parallel mechanism with integrated flexible joints, a large measurement range and high accuracy sensor is realized. However, the main errors of the sensor involve not only assembly errors, but also deformation errors of its flexible leg. Based on a flexible joint 6-UPUR (a kind of mechanism configuration where U-universal joint, P-prismatic joint, R-revolute joint) parallel six-axis force sensor developed during the prephase, assembly and deformation error modeling and analysis of the resulting sensors with a large measurement range and high accuracy are made in this paper. First, an assembly error model is established based on the imaginary kinematic joint method and the Denavit-Hartenberg (D-H) method. Next, a stiffness model is built to solve the stiffness matrix. The deformation error model of the sensor is obtained. Then, the first order kinematic influence coefficient matrix when the synthetic error is taken into account is solved. Finally, measurement and calibration experiments of the sensor composed of the hardware and software system are performed. Forced deformation of the force-measuring platform is detected by using laser interferometry and analyzed to verify the correctness of the synthetic error model. In addition, the first order kinematic influence coefficient matrix in actual circumstances is calculated. By comparing the condition numbers and square norms of the coefficient matrices, the conclusion is drawn theoretically that it is very important to take into account the synthetic error for design stage of the sensor and helpful to improve performance of the sensor in order to meet needs of actual working environments.

Error Modeling and Experimental Study of a Flexible Joint 6-UPUR Parallel Six-Axis Force Sensor

PubMed Central

Zhao, Yanzhi; Cao, Yachao; Zhang, Caifeng; Zhang, Dan; Zhang, Jie

2017-01-01

By combining a parallel mechanism with integrated flexible joints, a large measurement range and high accuracy sensor is realized. However, the main errors of the sensor involve not only assembly errors, but also deformation errors of its flexible leg. Based on a flexible joint 6-UPUR (a kind of mechanism configuration where U-universal joint, P-prismatic joint, R-revolute joint) parallel six-axis force sensor developed during the prephase, assembly and deformation error modeling and analysis of the resulting sensors with a large measurement range and high accuracy are made in this paper. First, an assembly error model is established based on the imaginary kinematic joint method and the Denavit-Hartenberg (D-H) method. Next, a stiffness model is built to solve the stiffness matrix. The deformation error model of the sensor is obtained. Then, the first order kinematic influence coefficient matrix when the synthetic error is taken into account is solved. Finally, measurement and calibration experiments of the sensor composed of the hardware and software system are performed. Forced deformation of the force-measuring platform is detected by using laser interferometry and analyzed to verify the correctness of the synthetic error model. In addition, the first order kinematic influence coefficient matrix in actual circumstances is calculated. By comparing the condition numbers and square norms of the coefficient matrices, the conclusion is drawn theoretically that it is very important to take into account the synthetic error for design stage of the sensor and helpful to improve performance of the sensor in order to meet needs of actual working environments. PMID:28961209

Prevention of the Post traumatic Fibrotic Response in Joints

DTIC Science & Technology

2016-12-01

researchers focusing on research associated with post -traumatic joint stiffness. This team has grown from a group of three initial Principal Investigators...The formation of the Translational Research Partnership ensured reaching the stated objective. Two Specific Aims were defined to test the...body weight of rabbits during the initial 8 weeks of the experimental study. During this time the rabbits were treated with tested and control

Design and testing of a novel multi-stroke micropositioning system with variable resolutions.

PubMed

Xu, Qingsong

2014-02-01

Multi-stroke stages are demanded in micro-/nanopositioning applications which require smaller and larger motion strokes with fine and coarse resolutions, respectively. This paper presents the conceptual design of a novel multi-stroke, multi-resolution micropositioning stage driven by a single actuator for each working axis. It eliminates the issue of the interference among different drives, which resides in conventional multi-actuation stages. The stage is devised based on a fully compliant variable stiffness mechanism, which exhibits unequal stiffnesses in different strokes. Resistive strain sensors are employed to offer variable position resolutions in the different strokes. To quantify the design of the motion strokes and coarse/fine resolution ratio, analytical models are established. These models are verified through finite-element analysis simulations. A proof-of-concept prototype XY stage is designed, fabricated, and tested to demonstrate the feasibility of the presented ideas. Experimental results of static and dynamic testing validate the effectiveness of the proposed design.

Regulation of proximal tubular cell differentiation and proliferation in primary culture by matrix stiffness and ECM components.

PubMed

Chen, Wan-Chun; Lin, Hsi-Hui; Tang, Ming-Jer

2014-09-15

To explore whether matrix stiffness affects cell differentiation, proliferation, and transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) in primary cultures of mouse proximal tubular epithelial cells (mPTECs), we used a soft matrix made from monomeric collagen type I-coated polyacrylamide gel or matrigel (MG). Both kinds of soft matrix benefited primary mPTECs to retain tubular-like morphology with differentiation and growth arrest and to evade TGF-β1-induced EMT. However, the potent effect of MG on mPTEC differentiation was suppressed by glutaraldehyde-induced cross-linking and subsequently stiffening MG or by an increasing ratio of collagen in the soft mixed gel. Culture media supplemented with MG also helped mPTECs to retain tubular-like morphology and a differentiated phenotype on stiff culture dishes as soft MG did. We further found that the protein level and activity of ERK were scaled with the matrix stiffness. U-0126, a MEK inhibitor, abolished the stiff matrix-induced dedifferentiation and proliferation. These data suggest that the ERK signaling pathway plays a vital role in matrix stiffness-regulated cell growth and differentiation. Taken together, both compliant property and specific MG signals from the matrix are required for the regulation of epithelial differentiation and proliferation. This study provides a basic understanding of how physical and chemical cues derived from the extracellular matrix regulate the physiological function of proximal tubules and the pathological development of renal fibrosis. Copyright © 2014 the American Physiological Society.

Active stiffness and strength in people with unilateral anterior shoulder instability: a bilateral comparison.

PubMed

Olds, Margie; McNair, Peter; Nordez, Antoine; Cornu, Christophe

2011-01-01

Active muscle stiffness might protect the unstable shoulder from recurrent dislocation. To compare strength and active stiffness in participants with unilateral anterior shoulder instability and to examine the relationship between active stiffness and functional ability. Cross-sectional study. University research laboratory. Participants included 16 males (age range, 16-40 years; height = 179.4 ± 6.1 cm; mass = 79.1 ± 6.8 kg) with 2 or more episodes of unilateral traumatic anterior shoulder instability. Active stiffness and maximal voluntary strength were measured bilaterally in participants. In addition, quality of life, function, and perceived instability were measured using the Western Ontario Stability Index, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, and Single Alpha Numeric Evaluation, respectively. We found less horizontal adduction strength (t(15) = -4.092, P = .001) and less stiffness at 30% (t(14) = -3.796, P = .002) and 50% (t(12) = -2.341, P = .04) maximal voluntary strength in the unstable than stable shoulder. Active stiffness was not correlated with quality of life, function, or perceived instability (r range, 0.0-0.25; P > .05). The observed reduction in stiffness in the unstable shoulder warrants inclusion of exercises in the rehabilitation program to protect the joint from perturbations that might lead to dislocation. The lack of association between active stiffness and quality of life, function, or perceived instability might indicate that stiffness plays a less direct role in shoulder stability.

Purinergic Signaling Regulates the Transforming Growth Factor-β3-Induced Chondrogenic Response of Mesenchymal Stem Cells to Hydrostatic Pressure.

PubMed

Steward, Andrew J; Kelly, Daniel J; Wagner, Diane R

2016-06-01

Although hydrostatic pressure (HP) is known to regulate chondrogenic differentiation of mesenchymal stromal/stem cells (MSCs), improved insight into the mechanotransduction of HP may form the basis for novel tissue engineering strategies. Previously, we demonstrated that matrix stiffness and calcium ion (Ca(++)) mobility regulate the mechanotransduction of HP; however, the mechanisms, by which these Ca(++) signaling pathways are initiated, are currently unknown. The purinergic pathway, in which adenosine triphosphate (ATP) is released and activates P-receptors to initiate Ca(++) signaling, plays a key role in the mechanotransduction of compression, but has yet to be investigated with regard to HP. Therefore, the objective of this study was to investigate the interplay between purinergic signaling, matrix stiffness, and the chondrogenic response of MSCs to HP. Porcine bone marrow-derived MSCs were seeded into soft or stiff agarose hydrogels and subjected to HP (10 MPa at 1 Hz for 4 h/d for 21 days) or kept in free swelling conditions. Stiff constructs were incubated with pharmacological inhibitors of extracellular ATP, P2 receptors, or hemichannels, or without any inhibitors as a control. As with other loading modalities, HP significantly increased ATP release in the control group; however, inhibition of hemichannels completely abrogated this response. The increase in sulfated glycosaminoglycan (sGAG) synthesis and vimentin reorganization observed in the control group in response to HP was suppressed in the presence of all three inhibitors, suggesting that purinergic signaling is involved in the mechanoresponse of MSCs to HP. Interestingly, ATP was released from both soft and stiff hydrogels in response to HP, but HP only enhanced chondrogenesis in the stiff hydrogels, indicating that matrix stiffness may act downstream of purinergic signaling to regulate the mechanoresponse of MSCs to HP. Addition of exogenous ATP did not replicate the effects of HP on chondrogenesis, suggesting that mechanisms other than purinergic signaling also regulate the response of MSCs to HP.

How joint characteristics between a piezoelectric beam and the main structure affect the performance of an energy harvester

NASA Astrophysics Data System (ADS)

Jahani, K.; Rafiei, M. M.; Aghazadeh, P.

2017-09-01

In this paper, the influence of the joint region between a piezoelectric energy harvesting beam and the vibratory main structure is studied. The investigations are conducted in two separate sections, namely numerical and experimental studies. In numerical studies, the effects of nonlinear parameters on generated power are investigated while the joint characteristics the between vibrating base and a piezoelectric energy harvester are taken into consideration. A unimorph beam with a tip mass and a nonlinear piezoelectric layer that undergoes a large-amplitude deflection is considered as an energy harvester. By applying the Euler-Lagrange equation and Gauss’s law the mechanical and electrical equations of motion are obtained, respectively. The excitation frequency is assumed to be close to the first natural frequency. Thus, a unimodal response is considered to be like that of a system with a single degree of freedom (SDOF). The joint between the vibrating main structure and the cantilevered beam is then added to the SDOF model. The joint characteristics are simulated with a light mass, mj , linear spring stiffness, kj , and equivalent viscous damper, cj . In two scenarios, i.e. with a rigid joint and with a flexible one, a numerical approach is followed to investigate the effects of each nonlinear parameter of the harvester (stiffness, damping and piezoelectric coefficient) on the harvested power. In experimental studies, the influence of a bolted joining technique and a flexible adhesive bonding method on the harvested power is investigated. The results achieved experimentally confirm those obtained numerically, i.e. a stiffer joint leads to a greater power produced by the harvester. In other words, neglecting the joint characteristics will cause the performance (maximum output power and the range of excitation frequency) of the harvester to be overestimated in numerical simulations.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

PubMed

Bezci, Semih E; Eleswarapu, Ananth; Klineberg, Eric O; O'Connell, Grace D

2018-02-12

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

A stochastic Iwan-type model for joint behavior variability modeling

NASA Astrophysics Data System (ADS)

Mignolet, Marc P.; Song, Pengchao; Wang, X. Q.

2015-08-01

This paper focuses overall on the development and validation of a stochastic model to describe the dissipation and stiffness properties of a bolted joint for which experimental data is available and exhibits a large scatter. An extension of the deterministic parallel-series Iwan model for the characterization of the force-displacement behavior of joints is first carried out. This new model involves dynamic and static coefficients of friction differing from each other and a broadly defined distribution of Jenkins elements. Its applicability is next investigated using the experimental data, i.e. stiffness and dissipation measurements obtained in harmonic testing of 9 nominally identical bolted joints. The model is found to provide a very good fit of the experimental data for each bolted joint notwithstanding the significant variability of their behavior. This finding suggests that this variability can be simulated through the randomization of only the parameters of the proposed Iwan-type model. The distribution of these parameters is next selected based on maximum entropy concepts and their corresponding parameters, i.e. the hyperparameters of the model, are identified using a maximum likelihood strategy. Proceeding with a Monte Carlo simulation of this stochastic Iwan model demonstrates that the experimental data fits well within the uncertainty band corresponding to the 5th and 95th percentiles of the model predictions which well supports the adequacy of the modeling effort.

Analysis of polyethylene terephthalate PET plastic bottle jointing system using finite element method (FEM)

NASA Astrophysics Data System (ADS)

Zaidi, N. A.; Rosli, Muhamad Farizuan; Effendi, M. S. M.; Abdullah, Mohamad Hariri

2017-09-01

For almost all injection molding applications of Polyethylene Terephthalate (PET) plastic was analyzed the strength, durability and stiffness of properties by using Finite Element Method (FEM) for jointing system of wood furniture. The FEM was utilized for analyzing the PET jointing system for Oak and Pine as wood based material of furniture. The difference pattern design of PET as wood jointing furniture gives the difference value of strength furniture itself. The results show the wood specimen with grooves and eclipse pattern design PET jointing give lower global estimated error is 28.90%, compare to the rectangular and non-grooves wood specimen of global estimated error is 63.21%.

Real-Time Vision-Based Stiffness Mapping †

PubMed Central

Althoefer, Kaspar; Asama, Hajime

2018-01-01

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness. PMID:29701704

Single and Multiple Object Tracking Using a Multi-Feature Joint Sparse Representation.

PubMed

Hu, Weiming; Li, Wei; Zhang, Xiaoqin; Maybank, Stephen

2015-04-01

In this paper, we propose a tracking algorithm based on a multi-feature joint sparse representation. The templates for the sparse representation can include pixel values, textures, and edges. In the multi-feature joint optimization, noise or occlusion is dealt with using a set of trivial templates. A sparse weight constraint is introduced to dynamically select the relevant templates from the full set of templates. A variance ratio measure is adopted to adaptively adjust the weights of different features. The multi-feature template set is updated adaptively. We further propose an algorithm for tracking multi-objects with occlusion handling based on the multi-feature joint sparse reconstruction. The observation model based on sparse reconstruction automatically focuses on the visible parts of an occluded object by using the information in the trivial templates. The multi-object tracking is simplified into a joint Bayesian inference. The experimental results show the superiority of our algorithm over several state-of-the-art tracking algorithms.

Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures.

PubMed

Vigdorchik, Jonathan M; Esquivel, Amanda O; Jin, Xin; Yang, King H; Onwudiwe, Ndidi A; Vaidya, Rahul

2012-09-27

We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model. Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons The mean displacement at the pubic symphysis was 20, 9 and 0.8 mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P = 0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P = 0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups. Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used.

Novel compliant actuator for wearable robotics applications.

PubMed

Claros, M; Soto, R; Rodríguez, J J; Cantú, C; Contreras-Vidal, José L

2013-01-01

In the growing fields of wearable robotics, rehabilitation robotics, prosthetics, and walking robots, variable impedance and force actuators are being designed and implemented because of their ability to dynamically modulate the intrinsic viscoelastic properties such as stiffness and damping. This modulation is crucial to achieve an efficient and safe human-robot interaction that could lead to electronically generate useful emergent dynamical behaviors. In this work we propose a novel actuation system in which is implemented a control scheme based on equilibrium forces for an active joint capable to provide assistance/resistance as needed and also achieve minimal mechanical impedance when tracking the movement of the user limbs. The actuation system comprises a DC motor with a built in speed reducer, two force-sensing resistors (FSR), a mechanism which transmits to the FSRs the torque developed in the joint and a controller which regulate the amount of energy that is delivered to the DC motor. The proposed system showed more impedance reduction, by the effect of the controlled contact forces, compared with the ones in the reviewed literature.

Quantitative evaluations of ankle spasticity and stiffness in neurological disorders using manual spasticity evaluator.

PubMed

Peng, Qiyu; Park, Hyung-Soon; Shah, Parag; Wilson, Nicole; Ren, Yupeng; Wu, Yi-Ning; Liu, Jie; Gaebler-Spira, Deborah J; Zhang, Li-Qun

2011-01-01

Spasticity and contracture are major sources of disability in people with neurological impairments that have been evaluated using various instruments: the Modified Ashworth Scale, tendon reflex scale, pendulum test, mechanical perturbations, and passive joint range of motion (ROM). These measures generally are either convenient to use in clinics but not quantitative or they are quantitative but difficult to use conveniently in clinics. We have developed a manual spasticity evaluator (MSE) to evaluate spasticity/contracture quantitatively and conveniently, with ankle ROM and stiffness measured at a controlled low velocity and joint resistance and Tardieu catch angle measured at several higher velocities. We found that the Tardieu catch angle was linearly related to the velocity, indicating that increased resistance at higher velocities was felt at further stiffer positions and, thus, that the velocity dependence of spasticity may also be position-dependent. This finding indicates the need to control velocity in spasticity evaluation, which is achieved with the MSE. Quantitative measurements of spasticity, stiffness, and ROM can lead to more accurate characterizations of pathological conditions and outcome evaluations of interventions, potentially contributing to better healthcare services for patients with neurological disorders such as cerebral palsy, spinal cord injury, traumatic brain injury, and stroke.

The mechanism of bolt loading

NASA Technical Reports Server (NTRS)

Lee, H. M.

1992-01-01

It is shown that the mechanism of bolt loading for preloaded fasteners can be effectively portrayed through simple spring models and some algebraic manipulations. Understanding schematically what is involved in such joints provides insight into the distribution of loads. The developed equations confirm that for both symmetric and nonsymmetric joints the loading plane factor and the stiffness factor directly affect the load seen in preloaded fasteners. The manner in which an external loading is transferred through the joint can be explained as energy dissipated in the various springs of both the abutment and the bolt itself.

What makes patients aware of their artificial knee joint?

PubMed

Loth, F L; Liebensteiner, M C; Giesinger, J M; Giesinger, K; Bliem, H R; Holzner, B

2018-01-08

Joint awareness was recently introduced as a new concept for outcome assessment after total knee arthroplasty (TKA). Findings from qualitative and psychometric studies suggest that joint awareness is a distinct concept especially relevant to patients with good surgical outcome and patients at late follow-up time points. The aim of this study was to improve the understanding of the concept of joint awareness by identifying situations in which patients are aware of their artificial knee joint and to investigate what bodily sensations and psychological factors raise a patient's awareness of her/his knee. In addition, we evaluated the relative importance of patient-reported outcome parameters that are commonly assessed in orthopaedics. Qualitative interviews were conducted with patients being at least 12 months after TKA. The interviews focused on when, where and for what reasons patients were aware of their artificial knee joint. To evaluate the relative importance of 'joint awareness' after TKA among nine commonly assessed outcome parameters (e.g. pain or stiffness), we collected importance ratings ('0' indicating no importance at all and '10' indicating high importance). We conducted interviews with 40 TKA patients (mean age 69.0 years; 65.0% female). Joint awareness was found to be frequently triggered by kneeling on the floor (30%), climbing stairs (25%), and starting up after resting (25%). Patients reported joint awareness to be related to activities of daily living (68%), specific movements (60%), or meteoropathy (18%). Sensations causing joint awareness included pain (45%) or stiffness (15%). Psychological factors raising a patient's awareness of his/her knee comprised for example feelings of insecurity (15%), and fears related to revision surgeries, inflammations or recurring pain (8%). Patients' importance ratings of outcome parameters were generally high and did not allow differentiating clearly among them. We have identified a wide range of situations, activities, movements and psychological factors contributing to patients' awareness of their artificial knee joints. This improves the understanding of the concept of joint awareness and of a patient's perception of his/her artificial knee joint. The diversity of sensations and factors raising patient's awareness of their joint encourages taking a broader perspective on outcome after TKA.

Is stiffness related to athletic groin pain?

PubMed

Gore, S J; Franklyn-Miller, A; Richter, C; Falvey, E C; King, E; Moran, K

2018-06-01

Athletic groin pain (AGP) is a common injury prevalent in field sports. One biomechanical measure that may be of importance for injury risk is stiffness. To date however, stiffness has not been examined in AGP. The primary aim was to determine whether AGP affects vertical and joint stiffness and if so, whether successful rehabilitation is associated with a change in stiffness. Sixty-five male patients with AGP and fifty male controls were recruited to this study. Assessment included a biomechanical examination of stiffness during a lateral hurdle hop test. Subjects with AGP were tested pre- and post-rehabilitation, while controls were tested once. AGP subjects were cleared for return to play in a median time of 9.14 weeks (5.14-29.0). Stiffness was significantly different at pre-rehabilitation in comparison with controls for four of the ten stiffness values examined: ankle plantar flexor, knee extensor, hip abductor, and vertical stiffness (P < .05, D = 0.36-0.79). Despite clearance for return to play, of these four variables, only hip abductor stiffness changed significantly from pre- to post-rehabilitation (P = .05, D = 0.35) to become non-significantly different to the uninjured group (P = .18, D = 0.26). These findings suggest that hip abductor stiffness may represent a target for AGP rehabilitation. Conversely, given the clearance for return to play, the lower sagittal plane and vertical stiffness in the AGP group in comparison with the uninjured controls likely represents either a compensatory mechanism to reduce the risk of further injury or a consequence of neuromuscular detraining. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Adjustable hinge permits movement of knee in plaster cast

NASA Technical Reports Server (NTRS)

Maley, W. E.

1967-01-01

Metal knee hinge with an adjustable sleeve worn on the outside of a leg cast facilitates movement of the knee joint. This helps eliminate stiffness of the knee and eliminates bulkiness and adjustment difficulty.

Bonded joint and method. [for reducing peak shear stress in adhesive bonds

NASA Technical Reports Server (NTRS)

Sainsbury-Carter, J. B. (Inventor)

1974-01-01

An improved joint is described for reducing the peak shear stress in adhesive bonds when adhesives are used to bond two materials which are in a lapped relationship and which differ in value of modulus of elasticity. An insert placed between the adhesive and one of the two materials acts to cushion the discontinuity of material stiffness thereby reducing the peak shear stress in the adhesive bond.

Hand Surgery In World War II. Medical Department, United States Army,

DTIC Science & Technology

1955-09-01

Few of these patients presented deep cicatrices , latent infection was minimal, and as a rule the position of function was maintained. DEBARKATION...HOSPITAL 217 Many patients were received with large dorsal cicatrices which, although healed, were unstable. Joints and tendons not directly injured by...burns were frequently damaged by constriction and immobility because of superimposed cicatrices . Joint stiffness was likely to be even more pronounced

Implications of low mechanical impedance in upper limb reaching motion.

PubMed

Popescu, Florin C; Rymeri, W Zev

2003-10-01

The equilibrium point hypothesis (EPH), much discussed in recent years, is central in a class of theories that posits an important role for muscular mechanical and reflex properties in the control of voluntary movement. We review briefly the findings of our studies testing the idea of equifinality, a major tenet of the EPH, which predicts that terminal limb position will be achieved regardless of transient perturbations in initial position or during ongoing movement. Our observations do not support this prediction of equifinality. We also report our findings that joint viscosity and elastic stiffness estimated during ballistic motion are unexpectedly low, limiting their potential contributions to the regulation either of limb movement trajectory or of limb stability. Taken together, our results imply that neuromuscular mechanical properties are unlikely to be used for regulating voluntary motion, and that other control strategies, most notably the use of feedforward controllers in which muscles act as force generators acting primarily on inertial loads, are more consistent with our observations.

Hospital For Special Surgery/Immune System REgulation In Musculoskeletal Disorders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eric Meffre; Lionel Ivashkiv

2007-08-20

Inflammation on musculoskeletal disorders such as rheumatoid arthritis (RA) is the result of dysregulation of the immune system. When the immune system, which maintains the integrity of the organism in an environment rich in infectious microbes, becomes misdirected toward components of one’s own tissue, autoimmune disease can result with autoantibodies contributing to the inflammation and tissue damage. RA is a chronic autoimmune disease marked by severe inflammation that causes pain, swelling, stiffness and loss of function in the joints, which is estimated to affect 1 percent of the US adult population. Furthermore, autoimmune diseases, which affect women at a highermore » rate, are the fourth largest cause of disability among women in the US and among the top ten causes of death. The long range goal of this study is to elucidate the mechanisms that regulate the generation of autoantibodies by B cells in normal individuals and in patients with autoimmune diseases and provide insights into potential therapeutic interventions.« less

The influence of muscles on knee flexion during the swing phase of gait.

PubMed

Piazza, S J; Delp, S L

1996-06-01

Although the movement of the leg during swing phase is often compared to the unforced motion of a compound pendulum, the muscles of the leg are active during swing and presumably influence its motion. To examine the roles of muscles in determining swing phase knee flexion, we developed a muscle-actuated forward dynamic simulation of the swing phase of normal gait. Joint angles and angular velocities at toe-off were derived from experimental measurements, as were pelvis motions and muscle excitations. Joint angles and joint moments resulting from the simulation corresponded to experimental measurements made during normal gait. Muscular joint moments and initial joint angular velocities were altered to determine the effects of each upon peak knee flexion in swing phase. As expected, the simulation demonstrated that either increasing knee extension moment or decreasing toe-off knee flexion velocity decreased peak knee flexion. Decreasing hip flexion moment or increasing toe-off hip flexion velocity also caused substantial decreases in peak knee flexion. The rectus femoris muscle played an important role in regulating knee flexion; removal of the rectus femoris actuator from the model resulted in hyperflexion of the knee, whereas an increase in the excitation input to the rectus femoris actuator reduced knee flexion. These findings confirm that reduced knee flexion during the swing phase (stiff-knee gait) may be caused by overactivity of the rectus femoris. The simulations also suggest that weakened hip flexors and stance phase factors that determine the angular velocities of the knee and hip at toe-off may be responsible for decreased knee flexion during swing phase.

The use of self-report questions to examine the prevalence of musculoskeletal problems: a test-retest study.

PubMed

Gill, Tiffany K; Tucker, Graeme R; Avery, Jodie C; Shanahan, E Michael; Menz, Hylton B; Taylor, Anne W; Adams, Robert J; Hill, Catherine L

2016-02-24

Case definition has long been an issue for comparability of results obtained for musculoskeletal pain prevalence, however the test-retest reliability of questions used to determine joint pain prevalence has not been examined. The objective of this study was to determine question reliability and the impact of question wording, ordering and the time between questions on responses. A Computer Assisted Telephone Interviewing (CATI) survey was used to re-administer questions collected as part of a population-based longitudinal cohort study. On two different occasions questions were asked of the same sample of 203 community dwelling respondents (which were initially randomly selected) aged 18 years and over at two time points 14 to 27 days apart (average 15 days). Reliability of the questions was assessed using Cohen's kappa (κ) and intraclass correlation coefficient (ICC) and whether question wording and period effects existed was assessed using a crossover design. The self-reported prevalence of doctor diagnosed arthritis demonstrated excellent reliability (κ = 0.84 and κ = 0.79 for questionnaires 1 and 2 respectively). The reliability of questions relating to musculoskeletal pain and/or stiffness ranged from moderate to excellent for both types of questions, that is, those related to ever having joint pain on most days for at least a month (κ = 0.52 to κ = 0.95) and having pain and/or stiffness on most days for the last month (κ = 0.52 to κ = 0.90). However there was an effect of question wording on the results obtained for hand, foot and back pain and/or stiffness indicating that the area of pain may influence prevalence estimates. Joint pain and stiffness questions are reliable and can be used to determine prevalence. However, question wording and pain area may impact on estimates with issues such as pain perception and effect on activities playing a possible role in the recall of musculoskeletal pain.

Balance disorders caused by running and jumping occurring in young basketball players.

PubMed

Struzik, Artur; Zawadzki, Jerzy; Pietraszewski, Bogdan

2015-01-01

Body balance, as one of the coordination abilities,is a desirable variable for basketball players as regards the necessity of efficient responses in constantly changing situations on a basketball court. The aim of this study was to check whether physical activity in the form of running and jumping influences variables characterizing the process of keeping body balance of a basketball player in the standing position. The research was conducted on 11 young basketball players. The measurements were taken with a Kistler force plate. Apart from commonly registered COP displacements, an additional variable describing the process of keeping body balance by a basketball player was ankle joint stiffness on the basis of which an "Index of Balance-Stiffness" (IB-S) was created. Statistically significant differences were obtained for the maximum COP displacements and ankle joint stiffness between measurements of balance in the standing position before and after the employed movement tasks whereas there were no statistically significant differences for the aforementioned variables describing the process of keeping balance between measurements after running and after jumping. The research results indicate that the employed movement activities brought about significant changes in the process of keeping balance of basketball player in the standing position which, after the run performed, remain on a similar level to the series of jumps being performed. The authors attempted to establish an index based on the stiffness which yields a possibility to perceive each basketball player as an individual person in the process of keeping balance.

Biomechanical comparisons of single- and double-legged drop jumps with changes in drop height.

PubMed

Wang, L-I; Peng, H-T

2014-06-01

The purpose of this study was to compare the biomechanics of single- and double-legged drop jumps (SDJ vs. DDJ) with changes in drop height. Jumping height, ground contact time, reactive strength index, ground reaction force, loading rate of ground reaction force, joint power and stiffness were measured in 12 male college students during SDJ from 20-, 30-, 40-, and 50-cm heights and DDJ from of 20- and 40-cm heights. The peak impact force was increased with the incremental drop height during SDJs. The jumping height and leg and ankle stiffness of SDJ30 were greater than those of SDJ40 and SDJ50. The knee and hip stiffnesses of SDJ30 were greater than those of SDJ50. The impact forces of SDJ30-50 were greater than those of DDJ40. The leg, ankle, knee and hip joint stiffnesses of SDJ20-30 were greater than those of DDJ20 and DDJ40. The propulsive forces of SDJ20-50 were greater than those of DDJ20 and DDJ40. The jumping height of SDJ30 was greater than that of DDJ20. Drop height of 30 cm was recommended during single-legged drop jump with the best biomechanical benefit. Single-legged drop jump from 20-30 cm could provide comparable intensity to double-legged drop jump from 40 cm. © Georg Thieme Verlag KG Stuttgart · New York.

Mechanical properties of hyaline and repair cartilage studied by nanoindentation.

PubMed

Franke, O; Durst, K; Maier, V; Göken, M; Birkholz, T; Schneider, H; Hennig, F; Gelse, K

2007-11-01

Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.

Stiffness is more than just duration and severity: a qualitative exploration in people with rheumatoid arthritis

PubMed Central

Dures, Emma; Kirwan, John; Pollock, Jon; Baker, Gill; Edmunds, Avis; Hewlett, Sarah

2015-01-01

Objective. Stiffness is internationally recognized as an important indicator of inflammatory activity in RA but is poorly understood and difficult to measure. The aim of this study was to explore the experience of stiffness from the patient perspective. Methods. Semi-structured interviews conducted with 16 RA patients were analysed independently by researchers and pat.ient partners using inductive thematic analysis. Results. Six themes were identified. Part of having RA identified stiffness as a normal consequence of RA, perceived as associated with disease-related aspects such as fluctuating disease activity, other RA symptoms and disease duration. Local and widespread highlighted stiffness occurring not only in joints, but also over the whole body, being more widespread during the morning or flare. Linked to behaviour and environment illustrated factors that influence stiffness, including movement, medications and weather. Highly variable captured the fluctuating nature of stiffness within and between patients and in relation to temporality, duration and intensity. Impacts on daily life emphasized the effect of stiffness on a range of domains, including physical function, quality of life, psychological well-being, activities of daily living and participation in work and leisure activities. Requires self-management detailed self-management strategies targeting both the symptom and its consequences. Conclusion. Patients’ experiences of stiffness were varied, complex and not exclusive to the morning period. Importantly, stiffness was reported in terms of impact rather than the traditional measurement concepts of severity or duration. Based on these findings, further research is needed to develop a patient-centred measure that adequately reflects inflammatory activity. PMID:25231178

Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players.

PubMed

Serpell, Benjamin G; Scarvell, Jennie M; Pickering, Mark R; Ball, Nick B; Perriman, Diana; Warmenhoven, John; Smith, Paul N

2016-01-01

Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL. This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data. There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=-0.05; p=0.89, and r=-0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001). Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity.

Correlations among measures of knee stiffness, gait performance and complaints in individuals with knee osteoarthritis.

PubMed

Oatis, Carol A; Wolff, Edward F; Lockard, Margery A; Michener, Lori A; Robbins, Steven J

2013-03-01

Stiffness is a common complaint in individuals with knee osteoarthritis and is a component of the osteoarthritis diagnosis. Yet the relationship between stiffness and function is poorly understood and methods to quantify stiffness are limited. Using a cross-sectional observational design with 66 subjects with knee osteoarthritis, stiffness and damping coefficients were calculated from a relaxed knee oscillation procedure. Gait parameters were measured using an electronic walkway. Self-reported pain, stiffness, and function were measured with the Western Ontario and McMaster Osteoarthritis Index. Correlation and Alexander's normalized-t approximation analyses were used to assess associations among the variables. Subset analysis was performed on subjects with and without tibiofemoral joint crepitus. Slight to moderate correlations existed between stiffness and damping coefficients and most gait parameters ((| r |=0.30-0.56; P<.05) and between Western Ontario and McMaster Osteoarthritis Index scores and all gait parameters (| r |=0.35-0.62; P<.05). The damping coefficient was only slightly associated with patient-rated Western Ontario and McMaster Osteoarthritis Index stiffness subscale scores. Subset analysis revealed significant correlations that differed between those with and without crepitus. These findings suggest that laboratory measured stiffness and damping coefficients, Western Ontario and McMaster Osteoarthritis Index scores and gait-related measurements assess different aspects related to movement in individuals with knee osteoarthritis. Stiffness and damping coefficients may offer the ability to explain gait changes in the knee that are independent of a person's perceptions particularly in the early stages of the disease. Copyright © 2013 Elsevier Ltd. All rights reserved.

Long-term exposure to airborne particles and arterial stiffness: the Multi-Ethnic Study of Atherosclerosis (MESA).

PubMed

O'Neill, Marie S; Diez-Roux, Ana V; Auchincloss, Amy H; Shen, Mingwu; Lima, João A; Polak, Joseph F; Barr, R Graham; Kaufman, Joel; Jacobs, David R

2011-06-01

Increased arterial stiffness could represent an intermediate subclinical outcome in the mechanistic pathway underlying associations between average long-term pollution exposure and cardiovascular events. We hypothesized that 20 years of exposure to particulate matter (PM) ≤ 2.5 and 10 μm in aerodynamic diameter (PM2.5 and PM10, respectively) would be positively associated with arterial stiffness in 3,996 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) who were seen at six U.S. study sites. We assigned pollution exposure during two decades preceding a clinical exam (2000-2002) using observed PM10 from monitors nearest participants' residences and PM10 and PM2.5 imputed from a space-time model. We examined three log-transformed arterial stiffness outcome measures: Young's modulus (YM) from carotid artery ultrasound and large (C1) and small (C2) artery vessel compliance from the radial artery pulse wave. All associations are expressed per 10 μg/m3 increment in PM and were adjusted for weather, age, sex, race, glucose, triglycerides, diabetes, waist:hip ratio, seated mean arterial pressure, smoking status, pack-years, cigarettes per day, environmental tobacco smoke, and physical activity. C1 and C2 models were further adjusted for heart rate, weight, and height. Long-term average particle exposure was not associated with greater arterial stiffness measured by YM, C1, or C2, and the few associations observed were not robust across metrics and adjustment schemes. Long-term particle mass exposure did not appear to be associated with greater arterial stiffness in this study sample.

Foot Health

MedlinePlus

... straight across and not too short Your foot health can be a clue to your overall health. For example, joint stiffness could mean arthritis. Tingling ... foot checks are an important part of your health care. If you have foot problems, be sure ...

Hunter syndrome

MedlinePlus

... from joint stiffness) Tests may include: Enzyme study Genetic testing for a change in the iduronate sulfatase gene ... genetic carrier and are considering having children ... who have a family history of MPS II. Prenatal testing is available. Carrier testing for female relatives of ...

Gout

MedlinePlus

... red, hot and stiff joints. Gout happens when uric acid builds up in your body. Uric acid comes from the breakdown of substances called purines. ... liver, dried beans and peas, and anchovies. Normally, uric acid dissolves in the blood. It passes through the ...

Morphological Computation of Haptic Perception of a Controllable Stiffness Probe

PubMed Central

Sornkarn, Nantachai; Dasgupta, Prokar; Nanayakkara, Thrishantha

2016-01-01

When people are asked to palpate a novel soft object to discern its physical properties such as texture, elasticity, and even non-homogeneity, they not only regulate probing behaviors, but also the co-contraction level of antagonistic muscles to control the mechanical impedance of fingers. It is suspected that such behavior tries to enhance haptic perception by regulating the function of mechanoreceptors at different depths of the fingertips and proprioceptive sensors such as tendon and spindle sensors located in muscles. In this paper, we designed and fabricated a novel two-degree of freedom variable stiffness indentation probe to investigate whether the regulation of internal stiffness, indentation, and probe sweeping velocity (PSV) variables affect the accuracy of the depth estimation of stiff inclusions in an artificial silicon phantom using information gain metrics. Our experimental results provide new insights into not only the biological phenomena of haptic perception but also new opportunities to design and control soft robotic probes. PMID:27257814

Angular Deformities of the Lower Limb in Children

PubMed Central

Espandar, Ramin; Mortazavi, Seyed Mohammad-Javad; Baghdadi, Taghi

2010-01-01

Angular deformities of the lower limbs are common during childhood. In most cases this represents a variation in the normal growth pattern and is an entirely benign condition. Presence of symmetrical deformities and absence of symptoms, joint stiffness, systemic disorders or syndromes indicates a benign condition with excellent long-term outcome. In contrast, deformities which are asymmetrical and associated with pain, joint stiffness, systemic disorders or syndromes may indicate a serious underlying cause and require treatment. Little is known about the relationship between sport participation and body adaptations during growth. Intense soccer participation increases the degree of genu varum in males from the age of 16. Since, according to some investigations, genu varum predisposes individuals to more injuries, efforts to reduce the development of genu varum in soccer players are warranted. In this article major topics of angular deformities of the knees in pediatric population are practically reviewed. PMID:22375192

Numerical and experimental analysis of a vibration isolator equipped with a negative stiffness system

NASA Astrophysics Data System (ADS)

Palomares, E.; Nieto, A. J.; Morales, A. L.; Chicharro, J. M.; Pintado, P.

2018-02-01

This paper presents a Negative Stiffness System (NSS) based on a set of two double-acting pneumatic linear actuators (PLA). The NSS is added to a system with a single degree of freedom, which consists of a sprung mass and a pneumatic spring. One end of each PLA is jointed to the sprung mass while the other end is jointed to the vibrating frame. In addition, the PLAs are symmetrically arranged so that they remain horizontal while the sprung mass is in static conditions. When the rear chamber is pressurised, the vertical component of the force applied by the PLAs will work against the pneumatic spring reducing the dynamic resonance frequency of the overall system. Experimental tests and simulations showed improvements regarding sprung mass isolation in comparison to the passive system without NSS, decreasing the resonance frequency by up to 58 % and improving the vibration attenuation for different experimental excitations.

Role of inhibition of osteogenesis function by Sema4D/Plexin-B1 signaling pathway in skeletal fluorosis in vitro.

PubMed

Liu, Xiao-li; Song, Jing; Liu, Ke-jian; Wang, Wen-peng; Xu, Chang; Zhang, Yu-zeng; Liu, Yun

2015-10-01

Skeletal fluorosis is a chronically metabolic bone disease with extensive hyperostosis osteosclerosis caused by long time exposure to fluoride. Skeletal fluorosis brings about a series of abnormal changes of the extremity, such as joint pain, joint stiffness, bone deformity, etc. Differentiation and maturation of osteoblasts were regulated by osteoclasts via Sema4D/Plexin-B1 signaling pathway. Furthermore, the differentiation and maturation of osteoclasts are conducted by osteoblasts via RANKL/RANK/OPG pathway. Both of these processes form a feedback circuit which is a key link in skeletal fluorosis. In this study, an osteoblast-osteoclast co-culture model in vitro was developed to illustrate the mechanism of skeletal fluorosis. With the increase of fluoride concentration, the expression level of Sema4D was decreased and TGF-β1 was increased continuously. OPG/RANKL mRNA level, however, increased gradually. On the basis of that, the inhibition of Sema4D/Plexin-B1/RhoA/ROCK signaling pathway caused by fluoride promoted the level of TGF-β1 and activated the proliferation of osteoblasts. In addition, osteroprotegerin (OPG) secreted by osteoblasts was up-regulated by fluoride. The competitive combination of OPG and RANKL was strengthened and the combination of RANKL and RANK was hindered. And then the differentiation and maturation of osteoclasts were inhibited, and bone absorption was weakened, leading to skeletal fluorosis.

Fatigue and Fracture Characterization of GlasGridRTM Reinforced Asphalt Concrete Pavement

NASA Astrophysics Data System (ADS)

Safavizadeh, Seyed Amirshayan

The purpose of this research is to develop an experimental and analytical framework for describing, modeling, and predicting the reflective cracking patterns and crack growth rates in GlasGridRTM-reinforced asphalt pavements. In order to fulfill this objective, the effects of different interfacial conditions (mixture and tack coat type, and grid opening size) on reflective cracking-related failure mechanisms and the fatigue and fracture characteristics of fiberglass grid-reinforced asphalt concrete beams were studied by means of four- and threepoint bending notched beam fatigue tests (NBFTs) and cyclic and monotonic interface shear tests. The digital image correlation (DIC) technique was utilized for obtaining the displacement and strain contours of specimen surfaces during each test. The DIC analysis results were used to develop crack tip detection methods that were in turn used to determine interfacial crack lengths in the shear tests, and vertical and horizontal (interfacial) crack lengths in the notched beam fatigue tests. Linear elastic fracture mechanics (LEFM) principles were applied to the crack length data to describe the crack growth. In the case of the NBFTs, a finite element (FE) code was developed and used for modeling each beam at different stages of testing and back-calculating the stress intensity factors (SIFs) for the vertical and horizontal cracks. The local effect of reinforcement on the stiffness of the system at a vertical crack-interface intersection or the resistance of the grid system to the deflection differential at the joint/crack (hereinafter called joint stiffness) for GlasGrid-reinforced asphalt concrete beams was determined by implementing a joint stiffness parameter into the finite element code. The strain level dependency of the fatigue and fracture characteristics of the GlasGrid-reinforced beams was studied by performing four-point bending notched beam fatigue tests at strain levels of 600, 750, and 900 microstrain. These beam tests were conducted at 15°C, 20°C, and 23°C, with the main focus being to find the characteristics at 20°C. The results obtained from the tests at the different temperatures were used to investigate the effects of temperature on the reflective cracking performance of the gridreinforced beam specimens. The temperature tests were also used to investigate the validity of the time-temperature superposition (t-TS) principle in shear and the beam fatigue performance of the grid-reinforced specimens. The NBFT results suggest that different interlayer conditions do not reflect a unique failure mechanism, and thus, in order to predict and model the performance of grid-reinforced pavement, all the mechanisms involved in weakening its structural integrity, including damage within the asphalt layers and along the interface, must be considered. The shear and beam fatigue test results suggest that the grid opening size, interfacial bond quality, and mixture type play important roles in the reflective cracking performance of GlasGrid-reinforced asphalt pavements. According to the NBTF results, GlasGrid reinforcement retards reflective crack growth by stiffening the composite system and introducing a joint stiffness parameter. The results also show that the higher the bond strength and interlayer stiffness values, the higher the joint stiffness and retardation effects. The t-TS studies proved the validity of this principle in terms of the reflective crack growth of the grid-reinforced beam specimens and the shear modulus and shear strength of the grid-reinforced interfaces.

Transcriptome profiling of Pinus radiata juvenile wood with contrasting stiffness identifies putative candidate genes involved in microfibril orientation and cell wall mechanics

PubMed Central

2011-01-01

Background The mechanical properties of wood are largely determined by the orientation of cellulose microfibrils in secondary cell walls. Several genes and their allelic variants have previously been found to affect microfibril angle (MFA) and wood stiffness; however, the molecular mechanisms controlling microfibril orientation and mechanical strength are largely uncharacterised. In the present study, cDNA microarrays were used to compare gene expression in developing xylem with contrasting stiffness and MFA in juvenile Pinus radiata trees in order to gain further insights into the molecular mechanisms underlying microfibril orientation and cell wall mechanics. Results Juvenile radiata pine trees with higher stiffness (HS) had lower MFA in the earlywood and latewood of each ring compared to low stiffness (LS) trees. Approximately 3.4 to 14.5% out of 3, 320 xylem unigenes on cDNA microarrays were differentially regulated in juvenile wood with contrasting stiffness and MFA. Greater variation in MFA and stiffness was observed in earlywood compared to latewood, suggesting earlywood contributes most to differences in stiffness; however, 3-4 times more genes were differentially regulated in latewood than in earlywood. A total of 108 xylem unigenes were differentially regulated in juvenile wood with HS and LS in at least two seasons, including 43 unigenes with unknown functions. Many genes involved in cytoskeleton development and secondary wall formation (cellulose and lignin biosynthesis) were preferentially transcribed in wood with HS and low MFA. In contrast, several genes involved in cell division and primary wall synthesis were more abundantly transcribed in LS wood with high MFA. Conclusions Microarray expression profiles in Pinus radiata juvenile wood with contrasting stiffness has shed more light on the transcriptional control of microfibril orientation and the mechanical properties of wood. The identified candidate genes provide an invaluable resource for further gene function and association genetics studies aimed at deepening our understanding of cell wall biomechanics with a view to improving the mechanical properties of wood. PMID:21962175

Ankle Joint Angle and Lower Leg Musculotendinous Unit Responses to Cryotherapy.

PubMed

Akehi, Kazuma; Long, Blaine C; Warren, Aric J; Goad, Carla L

2016-09-01

Akehi, K, Long, BC, Warren, AJ, and Goad, CL. Ankle joint angle and lower leg musculotendinous unit responses to cryotherapy. J Strength Cond Res 30(9): 2482-2492, 2016-The use of cold application has been debated for its influence on joint range of motion (ROM) and stiffness. The purpose of this study was to determine whether a 30-minute ice bag application to the plantarflexor muscles or ankle influences passive ankle dorsiflexion ROM and lower leg musculotendinous stiffness (MTS). Thirty-five recreationally active college-aged individuals with no history of lower leg injury 6 months before data collection volunteered. On each testing day, we measured maximum passive ankle dorsiflexion ROM (°) and plantarflexor torque (N·m) on an isokinetic dynamometer to calculate the passive plantarflexor MTS (N·m per degree) at 4 joint angles before, during, and after a treatment. Surface electromyography amplitudes (μV), and skin surface and ambient air temperature (°C) were also measured. Subjects received an ice bag to the posterior lower leg, ankle joint, or nothing for 30 minutes in different days. Ice bag application to the lower leg and ankle did not influence passive ROM (F(12,396) = 0.67, p = 0.78). Passive torque increased after ice bag application to the lower leg (F(12,396) = 2.21, p = 0.011). Passive MTS at the initial joint angle increased after ice bag application to the lower leg (F(12,396) = 2.14, p = 0.014) but not at the other joint angles (p > 0.05). Surface electromyography amplitudes for gastrocnemius and soleus muscles increased after ice application to the lower leg (F(2,66) = 5.61, p = 0.006; F(12,396) = 3.60, p < 0.001). Ice bag application to the lower leg and ankle joint does not alter passive dorsiflexion ROM but increases passive ankle plantarflexor torque in addition to passive ankle plantarflexor MTS at the initial joint angle.

Can chronic stretching change the muscle-tendon mechanical properties? A review.

PubMed

Freitas, S R; Mendes, B; Le Sant, G; Andrade, R J; Nordez, A; Milanovic, Z

2018-03-01

It is recognized that stretching is an effective method to chronically increase the joint range of motion. However, the effects of stretching training on the muscle-tendon structural properties remain unclear. This systematic review with meta-analysis aimed to determine whether chronic stretching alter the muscle-tendon structural properties. Published papers regarding longitudinal stretching (static, dynamic and/or PNF) intervention (either randomized or not) in humans of any age and health status, with more than 2 weeks in duration and at least 2 sessions per week, were searched in PubMed, PEDro, ScienceDirect and ResearchGate databases. Structural or mechanical variables from joint (maximal tolerated passive torque or resistance to stretch) or muscle-tendon unit (muscle architecture, stiffness, extensibility, shear modulus, volume, thickness, cross-sectional area, and slack length) were extracted from those papers. A total of 26 studies were selected, with a duration ranging from 3 to 8 weeks, and an average total time under stretching of 1165 seconds per week. Small effects were seen for maximal tolerated passive torque, but trivial effects were seen for joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness. A large heterogeneity was seen for most of the variables. Stretching interventions with 3- to 8-week duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Exploring novel objective functions for simulating muscle coactivation in the neck.

PubMed

Mortensen, J; Trkov, M; Merryweather, A

2018-04-11

Musculoskeletal modeling allows for analysis of individual muscles in various situations. However, current techniques to realistically simulate muscle response when significant amounts of intentional coactivation is required are inadequate. This would include stiffening the neck or spine through muscle coactivation in preparation for perturbations or impacts. Muscle coactivation has been modeled previously in the neck and spine using optimization techniques that seek to maximize the joint stiffness by maximizing total muscle activation or muscle force. These approaches have not sought to replicate human response, but rather to explore the possible effects of active muscle. Coactivation remains a challenging feature to include in musculoskeletal models, and may be improved by extracting optimization objective functions from experimental data. However, the components of such an objective function must be known before fitting to experimental data. This study explores the effect of components in several objective functions, in order to recommend components to be used for fitting to experimental data. Four novel approaches to modeling coactivation through optimization techniques are presented, two of which produce greater levels of stiffness than previous techniques. Simulations were performed using OpenSim and MATLAB cooperatively. Results show that maximizing the moment generated by a particular muscle appears analogous to maximizing joint stiffness. The approach of optimizing for maximum moment generated by individual muscles may be a good candidate for developing objective functions that accurately simulate muscle coactivation in complex joints. This new approach will be the focus of future studies with human subjects. Copyright © 2018 Elsevier Ltd. All rights reserved.

Determination of torque-limits for human and cat lumbar spine specimens during displacement-controlled physiological motions.

PubMed

Ianuzzi, Allyson; Pickar, Joel G; Khalsa, Partap S

2009-01-01

Quadruped animal models have been validated and used as biomechanical models for the lumbar spine. The biomechanics of the cat lumbar spine has not been well characterized, even though it is a common model used in neuromechanical studies. Compare the physiological ranges of motion and determine torque-limits for cat and human lumbar spine specimens during physiological motions. Biomechanics study. Cat and human lumbar spine specimens. Intervertebral angle (IVA), joint moment, yield point, torque-limit, and correlation coefficients. Cat (L2-sacrum) and human (T12-sacrum) lumbar spine specimens were mechanically tested to failure during displacement-controlled extension (E), lateral bending (LB), and axial rotation (AR). Single trials consisted of 10 cycles (10mm/s or 5 degrees /s) to a target displacement where the magnitude of the target displacement was increased for subsequent trials until failure occurred. Whole-lumbar stiffness, torque at yield point, and joint stiffness were determined. Scaling relationships were established using equations analogous to those that describe the load response of elliptically shaped beams. IVA magnitudes for cat and human lumbar spines were similar during physiological motions. Human whole-lumbar and joint stiffness magnitudes were significantly greater than those for cat spine specimens (p<.05). Torque-limits were also greater for humans compared with cats. Scaling relationships with high correlation (R(2) greater than 0.77) were established during later LB and AR. The current study defined "physiological ranges of movement" for human and cat lumbar spine specimens during displacement-controlled testing, and should be observed in future biomechanical studies conducted under displacement control.

Coexistence of Ankylosing Spondylitis and Klinefelter's Syndrome

PubMed Central

Kobak, Şenol; Yalçin, Murat; Karadeniz, Muamer; Oncel, Guray

2013-01-01

Ankylosing spondylitis is a chronic inflammatory disease characterized by inflammatory lower back pain and morning stiffness and accompanied by spine and sacroiliac joint involvement. Klinefelter's syndrome is a genetic condition that only affects males. Affected males have an extra X chromosome. This paper reports a 30-years-old male on followup with the diagnosis of Klinefelters syndrome. The patient admitted with complaints of inflammatory lower back, and neck pain and morning stiffness and was diagnosed with ankylosing spondylitis. Nonsteroidal anti-inflammatory drug and salazopyrine treatment resulted in significant regression in his complaints. PMID:23762731

Coexistence of Ankylosing Spondylitis and Klinefelter's Syndrome.

PubMed

Kobak, Senol; Yalçin, Murat; Karadeniz, Muamer; Oncel, Guray

2013-01-01

Ankylosing spondylitis is a chronic inflammatory disease characterized by inflammatory lower back pain and morning stiffness and accompanied by spine and sacroiliac joint involvement. Klinefelter's syndrome is a genetic condition that only affects males. Affected males have an extra X chromosome. This paper reports a 30-years-old male on followup with the diagnosis of Klinefelters syndrome. The patient admitted with complaints of inflammatory lower back, and neck pain and morning stiffness and was diagnosed with ankylosing spondylitis. Nonsteroidal anti-inflammatory drug and salazopyrine treatment resulted in significant regression in his complaints.

Cellular pressure and volume regulation and implications for cell mechanics

NASA Astrophysics Data System (ADS)

Jiang, Hongyuan; Sun, Sean

2013-03-01

In eukaryotic cells, small changes in cell volume can serve as important signals for cell proliferation, death and migration. Volume and shape regulation also directly impacts the mechanics of the cell and multi-cellular tissues. Recent experiments found that during mitosis, eukaryotic cells establish a preferred steady volume and pressure, and the steady volume and pressure can robustly adapt to large osmotic shocks. Here we develop a mathematical model of cellular pressure and volume regulation, incorporating essential elements such as water permeation, mechano-sensitive channels, active ion pumps and active stresses in the actomyosin cortex. The model can fully explain the available experimental data, and predicts the cellular volume and pressure for several models of cell cortical mechanics. Furthermore, we show that when cells are subjected to an externally applied load, such as in an AFM indentation experiment, active regulation of volume and pressure leads to complex cellular response. We found the cell stiffness highly depends on the loading rate, which indicates the transport of water and ions might contribute to the observed viscoelasticity of cells.

Extracellular matrix stiffness causes systematic variations in proliferation and chemosensitivity in myeloid leukemias.

PubMed

Shin, Jae-Won; Mooney, David J

2016-10-25

Extracellular matrix stiffness influences biological functions of some tumors. However, it remains unclear how cancer subtypes with different oncogenic mutations respond to matrix stiffness. In addition, the relevance of matrix stiffness to in vivo tumor growth kinetics and drug efficacy remains elusive. Here, we designed 3D hydrogels with physical parameters relevant to hematopoietic tissues and adapted them to a quantitative high-throughput screening format to facilitate mechanistic investigations into the role of matrix stiffness on myeloid leukemias. Matrix stiffness regulates proliferation of some acute myeloid leukemia types, including MLL-AF9 + MOLM-14 cells, in a biphasic manner by autocrine regulation, whereas it decreases that of chronic myeloid leukemia BCR-ABL + K-562 cells. Although Arg-Gly-Asp (RGD) integrin ligand and matrix softening confer resistance to a number of drugs, cells become sensitive to drugs against protein kinase B (PKB or AKT) and rapidly accelerated fibrosarcoma (RAF) proteins regardless of matrix stiffness when MLL-AF9 and BCR-ABL are overexpressed in K-562 and MOLM-14 cells, respectively. By adapting the same hydrogels to a xenograft model of extramedullary leukemias, we confirm the pathological relevance of matrix stiffness in growth kinetics and drug sensitivity against standard chemotherapy in vivo. The results thus demonstrate the importance of incorporating 3D mechanical cues into screening for anticancer drugs.

Motor control: the importance of stiffness.

PubMed

Hooper, Scott L

2006-04-18

An octopus brings food grasped by a tentacle to its mouth by bending the tentacle around a joint formed by stiffened distal and proximal tentacle muscles, and thus may use motor control strategies analogous to those in animals with articulated limbs.

Adhesive-bonded scarf and stepped-lap joints

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1973-01-01

Continuum mechanics solutions are derived for the static load-carrying capacity of scarf and stepped-lap adhesive-bonded joints. The analyses account for adhesive plasticity and adherend stiffness imbalance and thermal mismatch. The scarf joint solutions include a simple algebraic formula which serves as a close lower bound, within a small fraction of a per cent of the true answer for most practical geometries and materials. Digital computer programs were developed and, for the stepped-lap joints, the critical adherend and adhesive stresses are computed for each step. The scarf joint solutions exhibit grossly different behavior from that for double-lap joints for long overlaps inasmuch as that the potential bond shear strength continues to increase with indefinitely long overlaps on the scarf joints. The stepped-lap joint solutions exhibit some characteristics of both the scarf and double-lap joints. The stepped-lap computer program handles arbitrary (different) step lengths and thickness and the solutions obtained have clarified potentially weak design details and the remedies. The program has been used effectively to optimize the joint proportions.

Characterization of a compliant multi-layer system for tactile sensing with enhanced sensitivity and range

NASA Astrophysics Data System (ADS)

Chen, Ying; Yu, Miao; Bruck, Hugh A.; Smela, Elisabeth

2018-06-01

To allow robots to interact with humans via touch, new sensing concepts are needed that can detect a wide range of potential interactions and cover the body of a robot. In this paper, a skin-inspired multi-layer tactile sensing architecture is presented and characterized. The structure consists of stretchable piezoresistive strain-sensing layers over foam layers of different stiffness, allowing for both sufficient sensitivity and pressure range for human contacts. Strip-shaped sensors were used in this architecture to produce a deformation response proportional to pressure. The roles of the foam layers were elucidated by changing their stiffness and thickness, allowing the development of a geometric model to account for indenter interactions with the structure. The advantage of this architecture over other approaches is the ability to easily tune performance by adjusting the stiffness or thickness of the foams to tailor the response for different applications. Since viscoelastic materials were used, the temporal effects were also investigated.

Hypothyroidism presenting as destructive arthropathy of the fingers.

PubMed Central

Gerster, J. C.; Quadri, P.; Saudan, Y.

1985-01-01

A patient presenting with destructive arthropathy of the proximal interphalangeal (PIP) joints of the hands is described. She was initially believed to have rheumatoid arthritis but non-steroidal anti-inflammatory drugs were of no help. The patient was subsequently found to have hypothyroidism and erosive osteoarthritis of the fingers. Joint swelling, pain and stiffness responded dramatically to thyroid hormone substitution. The PIP joint spaces reappeared on the radiographs within 9 months. This case suggest that hypothyroidism may induce destructive arthropathy of the finger joints. As thyroxine replacement may reverse the rheumatic complaints, hypothyroidism should be considered in the differential diagnosis of a destructive arthropathy of unclear aetiology. Images Figure 1 Figure 2 PMID:3983045

Adaptive velocity-based six degree of freedom load control for real-time unconstrained biomechanical testing.

PubMed

Lawless, I M; Ding, B; Cazzolato, B S; Costi, J J

2014-09-22

Robotic biomechanics is a powerful tool for further developing our understanding of biological joints, tissues and their repair. Both velocity-based and hybrid force control methods have been applied to biomechanics but the complex and non-linear properties of joints have limited these to slow or stepwise loading, which may not capture the real-time behaviour of joints. This paper presents a novel force control scheme combining stiffness and velocity based methods aimed at achieving six degree of freedom unconstrained force control at physiological loading rates. Copyright © 2014 Elsevier Ltd. All rights reserved.

Clinical study of Agnikarma and Panchatikta Guggulu in the management of Sandhivata (osteoartheritis of knee joint).

PubMed

Sharma, Aneesh Vasudeva; Dudhamal, Tukaram Sambhaji; Gupta, Sanjay Kumar; Mahanta, Vyasadeva

2016-01-01

Sandhivata is a disease described under Vatavyadhi and resembles osteoarthritis (OA) in respect to etiology, pathology, and clinical features. Knee joints are more prone to be affected by this disease because it is the most frequently involved joint in daily works. Acharya Sushruta has indicated Agnikarma , when severe pain occurs in Twak , Mamsa , Sira, Snayu , Sandhi , and Asthi due to Vata Prakopa . Panchatikta Guggulu is a formulation mentioned in Chakradatta and Bhaishajya Ratnavali in the context of Kushtha Roga where it is also indicated for Sandhigata Vata and Asthigata Vata . The aim of this study is to evaluate the comparative effect of Agnikarma alone and Agnikarma along with Panchatikta Guggulu orally in Janugata Sandhivata (OA of knee joint). Thirty-three patients of Janugata Sandhivata were registered and randomly divided into two groups. In Group A ( n = 18), Agnikarma was done with Panchadhatu Shalaka once every week for one month while in Group B ( n = 15), Agnikarma along with Panchatikta Guggulu orally was given for one month. Weekly assessment was done for relief in Sandhishula (pain), Sparshaasahyata (tenderness), Sandhisphutana (crepitus), Sandhigraha (stiffness) by subjective gradation, and range of movement (ROM) was recorded in research proforma. In Sandhishula , 86% relief was found in Group A whereas 77.78% relief was obtained in Group B. Sparshaasahyata was reduced by 69% in Group A while 87.78% in Group B. Nearly 39% improvement was seen in Sandhisphutana in Group A while 46.67% in Group B. In Sandhigraha , 63% relief was obtained in each of the groups. The patients got relief from the pain after first sitting of Agnikarma in both the groups. The relief was sustained for more than 3 months in most of the patients. There was no significant difference in radiological findings before and after treatment in both the groups. It was concluded that Agnikarma is effective in the management of pain in the Sandhivata . However, the addition of Panchatikta Guggulu in the treatment provides better efficacy on joint stiffness and crepitus. Further analysis showed that better relief in pain was observed in Group A while relief in tenderness, crepitus, and stiffness was found better in Group B.

Design/Analysis of Metal/Composite Bonded Joints for Survivability at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Bartoszyk, Andrew E.

2004-01-01

A major design and analysis challenge for the JWST ISM structure is the metal/composite bonded joints that will be required to survive down to an operational ultra-low temperature of 30K (-405 F). The initial and current baseline design for the plug-type joint consists of a titanium thin walled fitting (1-3mm thick) bonded to the interior surface of an M555/954-6 composite truss square tube with an axially stiff biased lay-up. Metallic fittings are required at various nodes of the truss structure to accommodate instrument and lift-point bolted interfaces. Analytical experience and design work done on metal/composite bonded joints at temperatures below liquid nitrogen are limited and important analysis tools, material properties, and failure criteria for composites at cryogenic temperatures are virtually nonexistent. Increasing the challenge is the difficulty in testing for these required tools and parameters at 30K. A preliminary finite element analysis shows that failure due to CTE mismatch between the biased composite and titanium or aluminum is likely. Failure is less likely with Invar, however an initial mass estimate of Invar fittings demonstrates that Invar is not an automatic alternative. In order to gain confidence in analyzing and designing the ISM joints, a comprehensive joint development testing program has been planned and is currently running. The test program is designed for the correlation of the analysis methodology, including tuning finite element model parameters, and developing a composite failure criterion for the effect of multi-axial composite stresses on the strength of a bonded joint at 30K. The testing program will also consider stress mitigation using compliant composite layers and potential strength degradation due to multiple thermal cycles. Not only will the finite element analysis be correlated to the test data, but the FEA will be used to guide the design of the test. The first phase of the test program has been completed and the preliminary analysis has been revisited based on the test data In this work, we present an overview of the test plan, results today, and resulting design improvements.

A novel multi-item joint replenishment problem considering multiple type discounts.

PubMed

Cui, Ligang; Zhang, Yajun; Deng, Jie; Xu, Maozeng

2018-01-01

In business replenishment, discount offers of multi-item may either provide different discount schedules with a single discount type, or provide schedules with multiple discount types. The paper investigates the joint effects of multiple discount schemes on the decisions of multi-item joint replenishment. In this paper, a joint replenishment problem (JRP) model, considering three discount (all-unit discount, incremental discount, total volume discount) offers simultaneously, is constructed to determine the basic cycle time and joint replenishment frequencies of multi-item. To solve the proposed problem, a heuristic algorithm is proposed to find the optimal solutions and the corresponding total cost of the JRP model. Numerical experiment is performed to test the algorithm and the computational results of JRPs under different discount combinations show different significance in the replenishment cost reduction.

Reduced complexity of multi-track joint 2-D Viterbi detectors for bit-patterned media recording channel

NASA Astrophysics Data System (ADS)

Myint, L. M. M.; Warisarn, C.

2017-05-01

Two-dimensional (2-D) interference is one of the prominent challenges in ultra-high density recording system such as bit patterned media recording (BPMR). The multi-track joint 2-D detection technique with the help of the array-head reading can tackle this problem effectively by jointly processing the multiple readback signals from the adjacent tracks. Moreover, it can robustly alleviate the impairments due to track mis-registration (TMR) and media noise. However, the computational complexity of such detectors is normally too high and hard to implement in a reality, even for a few multiple tracks. Therefore, in this paper, we mainly focus on reducing the complexity of multi-track joint 2-D Viterbi detector without paying a large penalty in terms of the performance. We propose a simplified multi-track joint 2-D Viterbi detector with a manageable complexity level for the BPMR's multi-track multi-head (MTMH) system. In the proposed method, the complexity of detector's trellis is reduced with the help of the joint-track equalization method which employs 1-D equalizers and 2-D generalized partial response (GPR) target. Moreover, we also examine the performance of a full-fledged multi-track joint 2-D detector and the conventional 2-D detection. The results show that the simplified detector can perform close to the full-fledge detector, especially when the system faces high media noise, with the significant low complexity.

Past matrix stiffness primes epithelial cells and regulates their future collective migration through a mechanical memory.

PubMed

Nasrollahi, Samila; Walter, Christopher; Loza, Andrew J; Schimizzi, Gregory V; Longmore, Gregory D; Pathak, Amit

2017-11-01

During morphogenesis and cancer metastasis, grouped cells migrate through tissues of dissimilar stiffness. Although the influence of matrix stiffness on cellular mechanosensitivity and motility are well-recognized, it remains unknown whether these matrix-dependent cellular features persist after cells move to a new microenvironment. Here, we interrogate whether priming of epithelial cells by a given matrix stiffness influences their future collective migration on a different matrix - a property we refer to as the 'mechanical memory' of migratory cells. To prime cells on a defined matrix and track their collective migration onto an adjoining secondary matrix of dissimilar stiffness, we develop a modular polyacrylamide substrate through step-by-step polymerization of different PA compositions. We report that epithelial cells primed on a stiff matrix migrate faster, display higher actomyosin expression, form larger focal adhesions, and retain nuclear YAP even after arriving onto a soft secondary matrix, as compared to their control behavior on a homogeneously soft matrix. Priming on a soft ECM causes a reverse effect. The depletion of YAP dramatically reduces this memory-dependent migration. Our results present a previously unidentified regulation of mechanosensitive collective cell migration by past matrix stiffness, in which mechanical memory depends on YAP activity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Space Station alpha joint bearing

NASA Technical Reports Server (NTRS)

Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

1987-01-01

Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

Mechanical behaviour of hamstring muscles in low-back pain patients and control subjects.

PubMed

Tafazzoli, F; Lamontagne, M

1996-01-01

The purpose of this study was to measure and compare the passive elastic moment, the stiffness and the damping coefficient of the hip joint, as functions of the hip and knee joint angles in men with and without low-back pain. Two conventional tests, the straight-leg-raising test and the trunk forward flexion, were also performed and compared between these subjects. The passive elastic moment was measured using an isokinetic device in the passive mode. This device raised the lower limb from the horizontal position to the straight-leg-raising angle at a slow and constant angular velocity. A custom-made splint connected with the lever arm of the isokinetic device maintained the knee in extension and the ankle in the neutral position. The damping coefficient of the hip joint was measured for 0, 15, 45, 60, 75 and 90% of straight leg raising angle of each subject, using the suspension method based on small oscillation theory. To ensure that muscles were inactive during the passive hip moment tests, muscle activity was monitored with surface EMG. The stiffness was computed as the ratio of the change in passive elastic moment to the change in the hip angle. The passive elastic moment, the stiffness and the normalized trunk flexion were significantly different between the two groups respectively. There was, however, no difference between the two groups in the results of straight-leg-raise and damping coefficient of the hip. The passive elastic moment was a nonlinear function of the hip flexion angle and showed large intersubject differences, especially as the joint limit was approached. The damping coefficient was a polynomial function of the hip flexion angle. The measured variables were analysed using a discriminant function and it was shown that the two groups were clearly discriminable in a meaningful manner.

Effects of walkbot gait training on kinematics, kinetics, and clinical gait function in paraplegia and quadriplegia.

PubMed

Hwang, Jongseok; Shin, Yongil; Park, Ji-Ho; Cha, Young Joo; You, Joshua Sung H

2018-04-07

The robotic-assisted gait training (RAGT) system has gained recognition as an innovative, effective paradigm to improve functional ambulation and activities of daily living in spinal cord injury and stroke. However, the effects of the Walkbot robotic-assisted gait training system with a specialized hip-knee-ankle actuator have never been examined in the paraplegia and quadriplegia population. The aim of this study was to determine the long-term effects of Walkbot training on clinical for hips and knee stiffness in individuals with paraplegia or quadriplegia. Nine adults with subacute or chronic paraplegia resulting from spinal cord injury or quadriplegia resulting from cerebral vascular accident (CVA) and/or hypoxia underwent progressive conventional gait retraining combined with the Walkbot RAGT for 5 days/week over an average of 43 sessions for 8 weeks. Clinical outcomes were measured with the Functional Ambulation Category (FAC), Modified Rankin Scale (MRS), Korean version of the Modified Barthel Index (K-MBI), Modified Ashworth Scale (MAS). Kinetic and kinematic data were collected via a built-in Walkbot program. Wilcoxon signed-rank tests showed significant positive intervention effects on K-MBI, maximal hip flexion and extension, maximal knee flexion, active torque in the knee joint, resistive torque, and stiffness in the hip joint (P <  0.05). These findings suggest that the Walkbot RAGT was effective for improving knee and hip kinematics and the active knee joint moment while decreasing hip resistive force. These improvements were associated with functional recovery in gait, balance, mobility and daily activities. These findings suggest that the Walkbot RAGT was effective for improving knee and hip kinematics and the active knee joint moment while decreasing hip resistive force. This is the first clinical evidence for intensive, long-term effects of the Walkbot RAGT on active or resistive moments and stiffness associated with spasticity and functional mobility in individuals with subacute or chronic paraplegia or quadriplegia who had reached a plateau in motor recovery after conventional therapy.

The influence of artificially increased trunk stiffness on the balance recovery after a trip.

PubMed

van der Burg, J C E; Pijnappels, M; van Dieën, J H

2007-07-01

Falls occur frequently in the growing population of elderly. Since trunk control is critical for maintaining balance, the higher trunk stiffness in elderly people compared to the general population has been associated with their increased fall-risk. Theoretically, trunk stiffness may be beneficial for balance recovery in walking, i.e. after a trip. A stiff joint may provide a torque that restricts the perturbation effects and thereby reduces the probability of a fall. The aim of this study was to test whether trunk stiffness impaired or assisted balance recovery after a trip during walking. An orthopedic corset was used to simulate trunk stiffness in 11 young male adults. Subjects walked over a platform, with or without the corset on, and were occasionally tripped over a hidden obstacle. Kinematics of the tripping reaction were measured. Initial trunk accelerations were significantly attenuated by the corset, which indicates a positive effect of the stiffening corset. However, no subsequent effects on peak trunk inclination and on the peak moment arm of gravity on the trunk were found. The pattern of trunk motion allowed ample time for triggered or voluntary muscle responses to be generated, before a substantial inclination occurred. It appears that such active responses were sufficient in the young subjects tested to obtain a similar net effect with or without the increased trunk stiffness induced by the corset.

On the stiffness analysis of a cable driven leg exoskeleton.

PubMed

Sanjeevi, N S S; Vashista, Vineet

2017-07-01

Robotic systems are being used for gait rehabilitation of patients with neurological disorder. These devices are externally powered to apply external forces on human limbs to assist the leg motion. Patients while walking with these devices adapt their walking pattern in response to the applied forces. The efficacy of a rehabilitation paradigm thus depends on the human-robot interaction. A cable driven leg exoskeleton (CDLE) use actuated cables to apply external joint torques on human leg. Cables are lightweight and flexible but can only be pulled, thus a CDLE requires redundant cables. Redundancy in CDLE can be utilized to appropriately tune a robot's performance. In this work, we present the stiffness analysis of CDLE. Different stiffness performance indices are established to study the role of system parameters in improving the human-robot interaction.

Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players

PubMed Central

Serpell, Benjamin G; Scarvell, Jennie M; Pickering, Mark R; Ball, Nick B; Perriman, Diana; Warmenhoven, John; Smith, Paul N

2016-01-01

Background Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL. Methods This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data. Results There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=−0.05; p=0.89, and r=−0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001). Conclusions Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity. PMID:27900192

A comparison and update of direct kinematic-kinetic models of leg stiffness in human running.

PubMed

Liew, Bernard X W; Morris, Susan; Masters, Ashleigh; Netto, Kevin

2017-11-07

Direct kinematic-kinetic modelling currently represents the "Gold-standard" in leg stiffness quantification during three-dimensional (3D) motion capture experiments. However, the medial-lateral components of ground reaction force and leg length have been neglected in current leg stiffness formulations. It is unknown if accounting for all 3D would alter healthy biologic estimates of leg stiffness, compared to present direct modelling methods. This study compared running leg stiffness derived from a new method (multiplanar method) which includes all three Cartesian axes, against current methods which either only include the vertical axis (line method) or only the plane of progression (uniplanar method). Twenty healthy female runners performed shod overground running at 5.0 m/s. Three-dimensional motion capture and synchronised in-ground force plates were used to track the change in length of the leg vector (hip joint centre to centre of pressure) and resultant projected ground reaction force. Leg stiffness was expressed as dimensionless units, as a percentage of an individual's bodyweight divided by standing leg length (BW/LL). Leg stiffness using the line method was larger than the uniplanar method by 15.6%BW/LL (P < .001), and multiplanar method by 24.2%BW/LL (P < .001). Leg stiffness from the uniplanar method was larger than the multiplanar method by 8.5%BW/LL (6.5 kN/m) (P < .001). The inclusion of medial-lateral components significantly increased leg deformation magnitude, accounting for the reduction in leg stiffness estimate with the multiplanar method. Given that limb movements typically occur in 3D, the new multiplanar method provides the most complete accounting of all force and length components in leg stiffness calculation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Regional variation in the mechanical properties of the vertebral column during lateral bending in Morone saxatilis

PubMed Central

Nowroozi, B. N.; Brainerd, E. L.

2012-01-01

Unlike mammalian, disc-shaped intervertebral joints (IVJs), the IVJs in fishes are biconid structures, filled with fluid and thought to act as hydrostatic hinge joints during swimming. However, it remains unclear which IVJ structures are dominant in mechanical resistance to forces in fishes, and whether variation in these tissues might impact the function of the vertebral column along its length. Here, we measured the dynamic mechanical behaviour of IVJs from striped bass, Morone saxatilis. During lateral bending, angular stiffness was significantly lower in the caudal and cervical regions, relative to the abdominal region. The neutral zone, defined as the range of motion (ROM) at bending moments less than 0.001 Nm, was longer in the caudal relative to the abdominal IVJs. Hysteresis was 30–40% in all regions, suggesting that IVJs may play a role in energy dissipation during swimming. Cutting the vertical septum had no statistically significant effect, but cutting the encapsulating tissues caused a sharp decline in angular stiffness and a substantial increase in ROM and hysteresis. We conclude that stiffness decreases and ROM increases from cranial to caudal in striped bass, and that the encapsulating tissues play a prominent role in mechanical variation along the length of the vertebral column. PMID:22552920

Regional variation in the mechanical properties of the vertebral column during lateral bending in Morone saxatilis.

PubMed

Nowroozi, B N; Brainerd, E L

2012-10-07

Unlike mammalian, disc-shaped intervertebral joints (IVJs), the IVJs in fishes are biconid structures, filled with fluid and thought to act as hydrostatic hinge joints during swimming. However, it remains unclear which IVJ structures are dominant in mechanical resistance to forces in fishes, and whether variation in these tissues might impact the function of the vertebral column along its length. Here, we measured the dynamic mechanical behaviour of IVJs from striped bass, Morone saxatilis. During lateral bending, angular stiffness was significantly lower in the caudal and cervical regions, relative to the abdominal region. The neutral zone, defined as the range of motion (ROM) at bending moments less than 0.001 Nm, was longer in the caudal relative to the abdominal IVJs. Hysteresis was 30-40% in all regions, suggesting that IVJs may play a role in energy dissipation during swimming. Cutting the vertical septum had no statistically significant effect, but cutting the encapsulating tissues caused a sharp decline in angular stiffness and a substantial increase in ROM and hysteresis. We conclude that stiffness decreases and ROM increases from cranial to caudal in striped bass, and that the encapsulating tissues play a prominent role in mechanical variation along the length of the vertebral column.

Flexible Elements in the Mechanisms of Weaving Machines

NASA Astrophysics Data System (ADS)

Žák, J.

Weaving machines use several mechanisms to produce a fabric; their relative (mutual) position is exactly defined at any point of working cycle and must be maintained as accurately as possible. From that, it results some requirements on their design, such as stiffness of the joint frame, synchronization of their drives, accuracy and stiffness of particular links of those mechanisms and minimization of the clearances between them. In this paper, we have attempted to outline the possibility of replacing the binary links by using the flexible mechanism elements. In this step, we always removed one rotary constraint at least which is necessary when using a binary link, i.e., a rod, pitman or connecting rod. In practice, it means reducing the number of bearings which have a limited service life, require maintenance and when using them we cannot avoid the formation of clearances. In the case of a slay of the CAMEL weaving machine, it was furthermore possible to use the deformation energy to a relief of the drive, its better regulation and an overall reduction of energy consumption. Although this procedure is not subject to the use of special materials, there can be advantageously used fiber composites whose certain features make the design of such mechanisms easy to a great extent.

Crack Damage Parameters and Dilatancy of Artificially Jointed Granite Samples Under Triaxial Compression

NASA Astrophysics Data System (ADS)

Walton, G.; Alejano, L. R.; Arzua, J.; Markley, T.

2018-06-01

A database of post-peak triaxial test results was created for artificially jointed planes introduced in cylindrical compression samples of a Blanco Mera granite. Aside from examining the artificial jointing effect on major rock and rock mass parameters such as stiffness, peak strength and residual strength, other strength parameters related to brittle cracking and post-yield dilatancy were analyzed. Crack initiation and crack damage values for both the intact and artificially jointed samples were determined, and these damage envelopes were found to be notably impacted by the presence of jointing. The data suggest that with increased density of jointing, the samples transition from a combined matrix damage and joint slip yielding mechanism to yield dominated by joint slip. Additionally, post-yield dilation data were analyzed in the context of a mobilized dilation angle model, and the peak dilation angle was found to decrease significantly when there were joints in the samples. These dilatancy results are consistent with hypotheses in the literature on rock mass dilatancy.

Solder creep-fatigue interactions with flexible leaded parts

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.; Wen, L. C.; Mon, G. R.; Jetter, E.

1992-01-01

With flexible leaded parts, the solder-joint failure process involves a complex interplay of creep and fatigue mechanisms. To better understand the role of creep in typical multi-hour cyclic loading conditions, a specialized non-linear finite-element creep simulation computer program has been formulated. The numerical algorithm includes the complete part-lead-solder-PWB system, accounting for strain-rate dependence of creep on applied stress and temperature, and the role of the part-lead dimensions and flexibility that determine the total creep deflection (solder strain range) during stress relaxation. The computer program has been used to explore the effects of various solder creep-fatigue parameters such as lead height and stiffness, thermal-cycle test profile, and part/board differential thermal expansion properties. One of the most interesting findings is the strong presence of unidirectional creep-ratcheting that occurs during thermal cycling due to temperature dominated strain-rate effects. To corroborate the solder fatigue model predictions, a number of carefully controlled thermal-cycle tests have been conducted using special bimetallic test boards.

Assessing the Relative Contributions of Active Ankle and Knee Assistance to the Walking Mechanics of Transfemoral Amputees Using a Powered Prosthesis

PubMed Central

Simon, Ann M.; Hargrove, Levi J.

2016-01-01

Powered knee-ankle prostheses are capable of providing net-positive mechanical energy to amputees. Yet, there are limitless ways to deliver this energy throughout the gait cycle. It remains largely unknown how different combinations of active knee and ankle assistance affect the walking mechanics of transfemoral amputees. This study assessed the relative contributions of stance phase knee swing initiation, increasing ankle stiffness and powered plantarflexion as three unilateral transfemoral amputees walked overground at their self-selected walking speed. Five combinations of knee and ankle conditions were evaluated regarding the kinematics and kinetics of the amputated and intact legs using repeated measures analyses of variance. We found eliminating active knee swing initiation or powered plantarflexion was linked to increased compensations of the ipsilateral hip joint during the subsequent swing phase. The elimination of knee swing initiation or powered plantarflexion also led to reduced braking ground reaction forces of the amputated and intact legs, and influenced both sagittal and frontal plane loading of the intact knee joint. Gradually increasing prosthetic ankle stiffness influenced the shape of the prosthetic ankle plantarflexion moment, more closely mirroring the intact ankle moment. Increasing ankle stiffness also corresponded to increased prosthetic ankle power generation (despite a similar maximum stiffness value across conditions) and increased braking ground reaction forces of the amputated leg. These findings further our understanding of how to deliver assistance with powered knee-ankle prostheses and the compensations that occur when specific aspects of assistance are added/removed. PMID:26807889

Reinforcement of mono- and bi-layer poly(ethylene glycol) hydrogels with a fibrous collagen scaffold

PubMed Central

Kinneberg, K. R. C.; Nelson, A.; Stender, M.; Aziz, A. H.; Mozdzen, L. C.; Harley, B. A. C.; Bryant, S. J.; Ferguson, V. L.

2015-01-01

Biomaterial-based tissue engineering strategies hold great promise for osteochondral tissue repair. Yet significant challenges remain in joining highly dissimilar materials to achieve a biomimetic, mechanically robust design for repairing interfaces between soft tissue and bone. This study sought to improve interfacial properties and function in a bilayer, multi-phase hydrogel interpenetrated with a fibrous collagen scaffold. ‘Soft’ 10% (w/w) and ‘stiff’ 30% (w/w) PEGDM was formed into mono- or bilayer hydrogels possessing a sharp diffusional interface. Hydrogels were evaluated as single- (hydrogel only) or multi-phase (hydrogel+fibrous scaffold penetrating throughout the stiff layer and extending >500μm into the soft layer). Including a fibrous scaffold into both soft and stiff single-phase hydrogels significantly increased tangent modulus and toughness and decreased lateral expansion under compressive loading. In multi-phase hydrogels, finite element simulations predict substantially reduced stress and strain gradients across the soft—stiff hydrogel interface. When combining two low moduli constituent material, composites theory poorly predicts the observed, large modulus increases. These results suggest material structure associated with the fibrous scaffold penetrating within the PEG hydrogel as the major contributor to improved properties and function – the hydrogel bore compressive loads and the 3D fibrous scaffold was loaded in tension thus resisting lateral expansion. PMID:26001970

On the Value of Estimating Human Arm Stiffness during Virtual Teleoperation with Robotic Manipulators

PubMed Central

Buzzi, Jacopo; Ferrigno, Giancarlo; Jansma, Joost M.; De Momi, Elena

2017-01-01

Teleoperated robotic systems are widely spreading in multiple different fields, from hazardous environments exploration to surgery. In teleoperation, users directly manipulate a master device to achieve task execution at the slave robot side; this interaction is fundamental to guarantee both system stability and task execution performance. In this work, we propose a non-disruptive method to study the arm endpoint stiffness. We evaluate how users exploit the kinetic redundancy of the arm to achieve stability and precision during the execution of different tasks with different master devices. Four users were asked to perform two planar trajectories following virtual tasks using both a serial and a parallel link master device. Users' arm kinematics and muscular activation were acquired and combined with a user-specific musculoskeletal model to estimate the joint stiffness. Using the arm kinematic Jacobian, the arm end-point stiffness was derived. The proposed non-disruptive method is capable of estimating the arm endpoint stiffness during the execution of virtual teleoperated tasks. The obtained results are in accordance with the existing literature in human motor control and show, throughout the tested trajectory, a modulation of the arm endpoint stiffness that is affected by task characteristics and hand speed and acceleration. PMID:29018319

Associations of passive muscle stiffness, muscle stretch tolerance, and muscle slack angle with range of motion: individual and sex differences.

PubMed

Miyamoto, Naokazu; Hirata, Kosuke; Miyamoto-Mikami, Eri; Yasuda, Osamu; Kanehisa, Hiroaki

2018-05-29

Joint range of motion (ROM) is an important parameter for athletic performance and muscular injury risk. Nonetheless, a complete description of muscular factors influencing ROM among individuals and between men and women is lacking. We examined whether passive muscle stiffness (evaluated by angle-specific muscle shear modulus), tolerance to muscle stretch (evaluated by muscle shear modulus at end-ROM), and muscle slack angle of the triceps surae are associated with the individual variability and sex difference in dorsiflexion ROM, using ultrasound shear wave elastography. For men, ROM was negatively correlated to passive muscle stiffness of the medial and lateral gastrocnemius in a tensioned state and positively to tolerance to muscle stretch in the medial gastrocnemius. For women, ROM was only positively correlated to tolerance to muscle stretch in all muscles but not correlated to passive muscle stiffness. Muscle slack angle was not correlated to ROM in men and women. Significant sex differences were observed only for dorsiflexion ROM and passive muscle stiffness in a tensioned state. These findings suggest that muscular factors associated with ROM are different between men and women. Furthermore, the sex difference in dorsiflexion ROM might be attributed partly to that in passive muscle stiffness of plantar flexors.

The SiC hardware of the Sentinel-2 multi spectral instrument

NASA Astrophysics Data System (ADS)

Bougoin, Michel; Lavenac, Jérôme

2017-11-01

The Sentinel-2 mission is a major part of the GMES (Global Monitoring for Environment and Security) program which has been set up by the European Union, on a joint initiative with the European Space Agency. A pair of identical satellites will observe the earth from a sun-synchronous orbit at 786 km altitude. Astrium is the prime contractor of the satellites and their payload. The MultiSpectral Instrument features a "all-SiC" TMA (Three Mirror Anastygmat) telescope. MSI will provide optical images in 13 spectral bands, in the visible and also the near infra-red range, with a 10 to 60 m resolution and a 290 km wide swath. The Boostec® SiC material is used mainly for its high specific stiffness (Youngs modulus / density) and its high thermal stability (thermal conductivity / coefficient of thermal expansion) which allow to reduce the distortions induced by thermo-elastic stresses. Its high mechanical properties as well as the relevant technology enable to make not only the mirrors but also the structure which holds them and the elements of the focal plane (including some detectors packaging). Due to the required large size, accuracy and shape complexity, developing and manufacturing some of these SiC parts required innovative manufacturing approach. It is reviewed in the present paper.

Experimental parameter identification of a multi-scale musculoskeletal model controlled by electrical stimulation: application to patients with spinal cord injury.

PubMed

Benoussaad, Mourad; Poignet, Philippe; Hayashibe, Mitsuhiro; Azevedo-Coste, Christine; Fattal, Charles; Guiraud, David

2013-06-01

We investigated the parameter identification of a multi-scale physiological model of skeletal muscle, based on Huxley's formulation. We focused particularly on the knee joint controlled by quadriceps muscles under electrical stimulation (ES) in subjects with a complete spinal cord injury. A noninvasive and in vivo identification protocol was thus applied through surface stimulation in nine subjects and through neural stimulation in one ES-implanted subject. The identification protocol included initial identification steps, which are adaptations of existing identification techniques to estimate most of the parameters of our model. Then we applied an original and safer identification protocol in dynamic conditions, which required resolution of a nonlinear programming (NLP) problem to identify the serial element stiffness of quadriceps. Each identification step and cross validation of the estimated model in dynamic condition were evaluated through a quadratic error criterion. The results highlighted good accuracy, the efficiency of the identification protocol and the ability of the estimated model to predict the subject-specific behavior of the musculoskeletal system. From the comparison of parameter values between subjects, we discussed and explored the inter-subject variability of parameters in order to select parameters that have to be identified in each patient.

[Distal soft-tissue procedure in hallux valgus deformity].

PubMed

Arbab, D; Wingenfeld, C; Frank, D; Bouillon, B; König, D P

2016-04-01

Distal, lateral soft tissue release to restore mediolateral balance of the first metatarsophalangeal (MTP) joint in hallux valgus deformity. Incision of the adductor hallucis tendon from the fibular sesamoid, the lateral capsule, the lateral collateral ligament, and the lateral metatarsosesamoid ligament. Hallux valgus deformities or recurrent hallux valgus deformities with an incongruent MTP joint. General medical contraindications to surgical interventions. Painful stiffness of the MTP joint, osteonecrosis, congruent joint. Relative contraindications: connective tissue diseases (Marfan syndrome, Ehler-Danlos syndrome). Longitudinal, dorsal incision in the first intermetatarsal web space between the first and second MTP joint. Blunt dissection and identification of the adductor hallucis tendon. Release of the adductor tendon from the fibular sesamoid. Incision of the lateral capsule, the lateral collateral ligament, and the lateral metatarsosesamoid ligament. Postoperative management depends on bony correction. In joint-preserving procedures, dressing for 3 weeks in corrected position. Subsequently hallux valgus orthosis at night and a toe spreader for a further 3 months. Passive mobilization of the first MTP joint. Postoperative weight-bearing according to the osteotomy. A total of 31 patients with isolated hallux valgus deformity underwent surgery with a Chevron and Akin osteotomy and a distal medial and lateral soft tissue balancing. The mean preoperative intermetatarsal (IMA) angle was 12.3° (range 11-15°); the hallux valgus (HV) angle was 28.2° (25-36°). The mean follow-up was 16.4 months (range 12-22 months). The mean postoperative IMA correction ranged between 2 and 7° (mean 5.2°); the mean HV correction was 15.5° (range 9-21°). In all, 29 patients (93%) were satisfied or very satisfied with the postoperative outcome, while 2 patients (7%) were not satisfied due to one delayed wound healing and one recurrent hallux valgus deformity. There were no infections, clinical and radiological signs of avascular necrosis of the metatarsal head, overcorrection with hallux varus deformity, or significant stiffness of the first MTP joint.

The design of and chronic tissue response to a composite nerve electrode with patterned stiffness.

PubMed

Freeberg, M J; Stone, M A; Triolo, R J; Tyler, D J

2017-06-01

As neural interfaces demonstrate success in chronic applications, a novel class of reshaping electrodes with patterned regions of stiffness will enable application to a widening range of anatomical locations. Patterning stiff regions and flexible regions of the electrode enables nerve reshaping while accommodating anatomical constraints of various implant locations ranging from peripheral nerves to spinal and autonomic plexi. Introduced is a new composite electrode enabling patterning of regions of various electrode mechanical properties. The initial demonstration of the composite's capability is the composite flat interface nerve electrode (C-FINE). The C-FINE is constructed from a sandwich of patterned PEEK within layers of pliable silicone. The shape of the PEEK provides a desired pattern of stiffness: stiff across the width of the nerve to reshape the nerve, but flexible along its length to allow for bending with the nerve. This is particularly important in anatomical locations near joints or organs, and in constrained compartments. We tested pressure and volume design constraints in vitro to verify that the C-FINE can attain a safe cuff-to-nerve ratio (CNR) without impeding intraneural blood flow. We measured nerve function as well as nerve and axonal morphology following 3 month implantation of the C-FINE without wires on feline peripheral nerves in anatomically constrained areas near mobile joints and major blood vessels in both the hind and fore limbs. In vitro inflation tests showed effective CNRs (1.93  ±  0.06) that exceeded the industry safety standard of 1.5 at an internal pressure of 20 mmHg. This is less than the 30 mmHg shown to induce loss of conduction or compromise blood flow. Implanted cats showed no changes in physiology or electrophysiology. Behavioral signs were normal suggesting healthy nerves. Motor nerve conduction velocity and compound motor action potential did not change significantly between implant and explant (p  >  0.15 for all measures). Axonal density and myelin sheath thickness was not significantly different within the electrode compared to sections greater than 2 cm proximal to implanted cuffs (p  >  0.14 for all measures). We present the design and verification of a novel nerve cuff electrode, the C-FINE. Laminar manufacturing processes allow C-FINE stiffness to be configured for specific applications. Here, the central region in the configuration tested is stiff to reshape or conform to the target nerve, while edges are highly flexible to bend along its length. The C-FINE occupies less volume than other NCEs, making it suitable for implantation in highly mobile locations near joints. Design constraints during simulated transient swelling were verified in vitro. Maintenance of nerve health in various challenging anatomical locations (sciatic and median/ulnar nerves) was verified in a chronic feline model in vivo.

The design of and chronic tissue response to a composite nerve electrode with patterned stiffness

NASA Astrophysics Data System (ADS)

Freeberg, M. J.; Stone, M. A.; Triolo, R. J.; Tyler, D. J.

2017-06-01

Objective. As neural interfaces demonstrate success in chronic applications, a novel class of reshaping electrodes with patterned regions of stiffness will enable application to a widening range of anatomical locations. Patterning stiff regions and flexible regions of the electrode enables nerve reshaping while accommodating anatomical constraints of various implant locations ranging from peripheral nerves to spinal and autonomic plexi. Approach. Introduced is a new composite electrode enabling patterning of regions of various electrode mechanical properties. The initial demonstration of the composite’s capability is the composite flat interface nerve electrode (C-FINE). The C-FINE is constructed from a sandwich of patterned PEEK within layers of pliable silicone. The shape of the PEEK provides a desired pattern of stiffness: stiff across the width of the nerve to reshape the nerve, but flexible along its length to allow for bending with the nerve. This is particularly important in anatomical locations near joints or organs, and in constrained compartments. We tested pressure and volume design constraints in vitro to verify that the C-FINE can attain a safe cuff-to-nerve ratio (CNR) without impeding intraneural blood flow. We measured nerve function as well as nerve and axonal morphology following 3 month implantation of the C-FINE without wires on feline peripheral nerves in anatomically constrained areas near mobile joints and major blood vessels in both the hind and fore limbs. Main Results. In vitro inflation tests showed effective CNRs (1.93  ±  0.06) that exceeded the industry safety standard of 1.5 at an internal pressure of 20 mmHg. This is less than the 30 mmHg shown to induce loss of conduction or compromise blood flow. Implanted cats showed no changes in physiology or electrophysiology. Behavioral signs were normal suggesting healthy nerves. Motor nerve conduction velocity and compound motor action potential did not change significantly between implant and explant (p  >  0.15 for all measures). Axonal density and myelin sheath thickness was not significantly different within the electrode compared to sections greater than 2 cm proximal to implanted cuffs (p  >  0.14 for all measures). Significance. We present the design and verification of a novel nerve cuff electrode, the C-FINE. Laminar manufacturing processes allow C-FINE stiffness to be configured for specific applications. Here, the central region in the configuration tested is stiff to reshape or conform to the target nerve, while edges are highly flexible to bend along its length. The C-FINE occupies less volume than other NCEs, making it suitable for implantation in highly mobile locations near joints. Design constraints during simulated transient swelling were verified in vitro. Maintenance of nerve health in various challenging anatomical locations (sciatic and median/ulnar nerves) was verified in a chronic feline model in vivo.

Characteristics of Extra Narrow Gap Weld of HSLA Steel Welded by Single-Seam per Layer Pulse Current GMA Weld Deposition

NASA Astrophysics Data System (ADS)

Agrawal, B. P.; Ghosh, P. K.

2017-03-01

Butt weld joints are produced using pulse current gas metal arc welding process by employing the technique of centrally laid multi-pass single-seam per layer weld deposition in extra narrow groove of thick HSLA steel plates. The weld joints are prepared by using different combination of pulse parameters. The selection of parameter of pulse current gas metal arc welding is done considering a summarized influence of simultaneously interacting pulse parameters defined by a dimensionless hypothetical factor ϕ. The effect of diverse pulse parameters on the characteristics of weld has been studied. Weld joint is also prepared by using commonly used multi-pass multi-seam per layer weld deposition in conventional groove. The extra narrow gap weld joints have been found much superior to the weld joint prepared by multi-pass multi-seam per layer deposition in conventional groove with respect to its metallurgical characteristics and mechanical properties.

Loss of miR-203 regulates cell shape and matrix adhesion through ROBO1/Rac/FAK in response to stiffness

PubMed Central

Le, Lily Thao-Nhi; Cazares, Oscar; Mouw, Janna K.; Chatterjee, Sharmila; Macias, Hector; Moran, Angel; Ramos, Jillian; Keely, Patricia J.; Weaver, Valerie M.

2016-01-01

Breast tumor progression is accompanied by changes in the surrounding extracellular matrix (ECM) that increase stiffness of the microenvironment. Mammary epithelial cells engage regulatory pathways that permit dynamic responses to mechanical cues from the ECM. Here, we identify a SLIT2/ROBO1 signaling circuit as a key regulatory mechanism by which cells sense and respond to ECM stiffness to preserve tensional homeostasis. We observed that Robo1 ablation in the developing mammary gland compromised actin stress fiber assembly and inhibited cell contractility to perturb tissue morphogenesis, whereas SLIT2 treatment stimulated Rac and increased focal adhesion kinase activity to enhance cell tension by maintaining cell shape and matrix adhesion. Further investigation revealed that a stiff ECM increased Robo1 levels by down-regulating miR-203. Consistently, patients whose tumor expressed a low miR-203/high Robo1 expression pattern exhibited a better overall survival prognosis. These studies show that cells subjected to stiffened environments up-regulate Robo1 as a protective mechanism that maintains cell shape and facilitates ECM adherence. PMID:26975850

Exercise through Menopause.

ERIC Educational Resources Information Center

Stuhr, Robyn M.

2002-01-01

Menopause is associated with many different health effects and symptoms. This paper explains that regular exercise can play a critical role in protecting health and battling the increased risk of cardiovascular disease, osteoporosis, pelvic floor atrophy, and joint stiffness associated with menopause. Exercise programs for menopausal women should…

Long term type 1 diabetes is associated with hand pain, disability and stiffness but not with structural hand osteoarthritis features – The Dialong hand study

PubMed Central

Magnusson, Karin; Bech Holte, Kristine; Juel, Niels Gunnar; Brox, Jens Ivar; Hagen, Kåre Birger; Haugen, Ida Kristin; Berg, Tore Julsrud

2017-01-01

Objective To explore whether having long-term type 1 diabetes (>45 years) is associated with a higher prevalence of radiographic hand OA, erosive hand OA and increased hand pain, disability and stiffness. Methods In total N = 96 persons with type 1 diabetes diagnosed before 1970 were included (mean [SD] age: 62.2 [7.4], mean [SD] HbA1c: 7.43 [0.80] and N = 49 [51%] men). Regular measurements of their HbA1c were obtained till 2015. We included N = 69 healthy controls without any diabetes (mean [SD] age: 63.0 [7.0], mean [SD] HbA1c: 5.41 [0.32], N = 29 [42%] men). The groups were compared for radiographic hand OA (Kellgren-Lawrence grade ≥2 in ≥1 joint) and erosive hand OA (central erosions in ≥1 joint), Australian/Canadian index (AUSCAN) for hand pain, disability and stiffness using regression analyses adjusted for age, sex, educational level and waist circumference. Results We found no associations between having long term type 1 diabetes and more prevalent radiographic hand OA (OR = 0.83, 95% CI = 0.38–1.81). We found a trend towards higher prevalence of erosive hand OA in diabetes patients (OR = 2.96, 95% CI = 0.82–10.64). Strong and consistent associations were observed between long term type 1 diabetes and increased hand pain (B = 2.78, 95% CI = 1.65–3.91), disability (B = 5.30, 95% CI = 3.48–7.12) and stiffness (B = 2.00, 95% CI = 1.33–2.67). These associations were particularly strong for women and participants below the median age of 61 years. Conclusion Long-term type 1 diabetes was not associated with radiographic hand OA, but was strongly associated with hand pain, disability and stiffness. The association between diabetes and erosive hand OA warrants further investigation. PMID:28510594

A springy pendulum could describe the swing leg kinetics of human walking.

PubMed

Song, Hyunggwi; Park, Heewon; Park, Sukyung

2016-06-14

The dynamics of human walking during various walking conditions could be qualitatively captured by the springy legged dynamics, which have been used as a theoretical framework for bipedal robotics applications. However, the spring-loaded inverted pendulum model describes the motion of the center of mass (CoM), which combines the torso, swing and stance legs together and does not explicitly inform us as to whether the inter-limb dynamics share the springy legged dynamics characteristics of the CoM. In this study, we examined whether the swing leg dynamics could also be represented by springy mechanics and whether the swing leg stiffness shows a dependence on gait speed, as has been observed in CoM mechanics during walking. The swing leg was modeled as a spring-loaded pendulum hinged at the hip joint, which is under forward motion. The model parameters of the loaded mass were adopted from body parameters and anthropometric tables, whereas the free model parameters for the rest length of the spring and its stiffness were estimated to best match the data for the swing leg joint forces. The joint forces of the swing leg were well represented by the springy pendulum model at various walking speeds with a regression coefficient of R(2)>0.8. The swing leg stiffness increased with walking speed and was correlated with the swing frequency, which is consistent with previous observations from CoM dynamics described using the compliant leg. These results suggest that the swing leg also shares the springy dynamics, and the compliant walking model could be extended to better present swing leg dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs

PubMed Central

Hirai, Hiroaki; Miyazaki, Fumio; Naritomi, Hiroaki; Koba, Keitaro; Oku, Takanori; Uno, Kanna; Uemura, Mitsunori; Nishi, Tomoki; Kageyama, Masayuki; Krebs, Hermano Igo

2015-01-01

Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist–antagonist (AA) muscle pairs may provide insight into such transformations, especially for a reference frame in the muscle space. In this study, we examined the AA concept using the following explanatory variables: the AA ratio, which is related to the equilibrium-joint angle, and the AA sum, which is associated with joint stiffness. We formulated muscle synergies as a function of AA sums, positing that muscle synergies are composite units of mechanical impedance. The AA concept can be regarded as another form of the equilibrium-point (EP) hypothesis, and it can be extended to the concept of EP-based synergies. We introduce, here, a novel tool for analyzing the neurological and motor functions underlying human movements and review some initial insights from our results about the relationships between muscle synergies, endpoint stiffness, and virtual trajectories (time series of EP). Our results suggest that (1) muscle synergies reflect an invariant balance in the co-activation of AA muscle pairs; (2) each synergy represents the basis for the radial, tangential, and null movements of the virtual trajectory in the polar coordinates centered on the specific joint at the base of the body; and (3) the alteration of muscle synergies (for example, due to spasticity or rigidity following neurological injury) results in significant distortion of endpoint stiffness and concomitant virtual trajectories. These results indicate that muscle synergies (i.e., the balance of muscle mechanical impedance) are essential for motor control. PMID:26636079

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs.

PubMed

Hirai, Hiroaki; Miyazaki, Fumio; Naritomi, Hiroaki; Koba, Keitaro; Oku, Takanori; Uno, Kanna; Uemura, Mitsunori; Nishi, Tomoki; Kageyama, Masayuki; Krebs, Hermano Igo

2015-01-01

Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist-antagonist (AA) muscle pairs may provide insight into such transformations, especially for a reference frame in the muscle space. In this study, we examined the AA concept using the following explanatory variables: the AA ratio, which is related to the equilibrium-joint angle, and the AA sum, which is associated with joint stiffness. We formulated muscle synergies as a function of AA sums, positing that muscle synergies are composite units of mechanical impedance. The AA concept can be regarded as another form of the equilibrium-point (EP) hypothesis, and it can be extended to the concept of EP-based synergies. We introduce, here, a novel tool for analyzing the neurological and motor functions underlying human movements and review some initial insights from our results about the relationships between muscle synergies, endpoint stiffness, and virtual trajectories (time series of EP). Our results suggest that (1) muscle synergies reflect an invariant balance in the co-activation of AA muscle pairs; (2) each synergy represents the basis for the radial, tangential, and null movements of the virtual trajectory in the polar coordinates centered on the specific joint at the base of the body; and (3) the alteration of muscle synergies (for example, due to spasticity or rigidity following neurological injury) results in significant distortion of endpoint stiffness and concomitant virtual trajectories. These results indicate that muscle synergies (i.e., the balance of muscle mechanical impedance) are essential for motor control.

Association between use of self-prescribed complementary and alternative medicine and menopause-related symptoms: a cross-sectional study.

PubMed

Peng, Wenbo; Sibbritt, David W; Hickman, Louise; Adams, Jon

2015-10-01

To examine the association between self-prescribed complementary and alternative medicine use and menopause-related symptoms, stratified by menopausal status. Data were obtained from a cross-sectional survey of a nationally representative sample of 10,011 menopausal women from the Australian Longitudinal Study on Women's Health, conducted in 2010. Multivariable logistic regression models were applied to identify if the use of selected self-prescribed complementary and alternative medicine was significantly associated with a range of menopause-related symptoms. Vitamins/minerals were more likely to be used by natural menopausal women experiencing anxiety (adjusted OR=1.20) and/or stiff/painful joints (adjusted OR=1.16). Yoga/meditation was more likely to be used by women with hysterectomy (adjusted OR=1.76) or natural menopausal women (adjusted OR=1.38) experiencing anxiety. Herbal medicines were more likely to be used by natural menopausal women experiencing anxiety (adjusted OR=1.22), tiredness (adjusted OR=1.20), and/or stiff/painful joints (adjusted OR=1.17), and by women with oophorectomy experiencing tiredness (adjusted OR=1.45). Aromatherapy oils were more likely to be used by natural menopausal women experiencing night sweats (adjusted OR=1.25) and by women with hysterectomy experiencing anxiety (adjusted OR=2.02). Chinese medicines were more likely to be used by women with oophorectomy experiencing stiff/painful joints (adjusted OR=4.06) and/or palpitations (adjusted OR=3.06). Our study will help improve the patient-provider communication regarding complementary and alternative medicine use for menopause, and we conclude that menopausal status should be taken into account by providers for menopause care. The women's experience and motivations of such use warrant further research. Copyright © 2015 Elsevier Ltd. All rights reserved.

Test and analysis of Celion 3000/PMR-15, graphite/polyimide bonded composite joints: Data report

NASA Technical Reports Server (NTRS)

Cushman, J. B.; Mccleskey, S. F.; Ward, S. H.

1982-01-01

Standard single lap, double lap and symmetric step lap bonded joints of Celion 3000/PMR-15 graphite/polyimide composite were evaluated. Composite to composite and composite to titanium joints were tested at 116 K (-250 F), 294 K (70 F) and 561 K (550 F). Joint parameters evaluated are lap length, adherend thickness, adherend axial stiffness, lamina stacking sequence and adherend tapering. Advanced joint concepts were examined to establish the change in performance of preformed adherends, scalloped adherends and hybrid systems. The material properties of the high temperature adhesive, designated A7F, used for bonding were established. The bonded joint tests resulted in interlaminar shear or peel failures of the composite and there were very few adhesive failures. Average test results agree with expected performance trends for the various test parameters. Results of finite element analyses and of test/analysis correlations are also presented.

Interfacial contact stiffness of fractal rough surfaces.

PubMed

Zhang, Dayi; Xia, Ying; Scarpa, Fabrizio; Hong, Jie; Ma, Yanhong

2017-10-09

In this work we describe a theoretical model that predicts the interfacial contact stiffness of fractal rough surfaces by considering the effects of elastic and plastic deformations of the fractal asperities. We also develop an original test rig that simulates dovetail joints for turbo machinery blades, which can fine tune the normal contact load existing between the contacting surfaces of the blade root. The interfacial contact stiffness is obtained through an inverse identification method in which finite element simulations are fitted to the experimental results. Excellent agreement is observed between the contact stiffness predicted by the theoretical model and by the analogous experimental results. We demonstrate that the contact stiffness is a power law function of the normal contact load with an exponent α within the whole range of fractal dimension D(1 < D < 2). We also show that for 1 < D < 1.5 the Pohrt-Popov behavior (α = 1/(3 - D)) is valid, however for 1.5 < D < 2, the exponent α is different and equal to 2(D - 1)/D. The diversity between the model developed in the work and the Pohrt-Popov one is explained in detail.

Predictive Behavior of a Computational Foot/Ankle Model through Artificial Neural Networks.

PubMed

Chande, Ruchi D; Hargraves, Rosalyn Hobson; Ortiz-Robinson, Norma; Wayne, Jennifer S

2017-01-01

Computational models are useful tools to study the biomechanics of human joints. Their predictive performance is heavily dependent on bony anatomy and soft tissue properties. Imaging data provides anatomical requirements while approximate tissue properties are implemented from literature data, when available. We sought to improve the predictive capability of a computational foot/ankle model by optimizing its ligament stiffness inputs using feedforward and radial basis function neural networks. While the former demonstrated better performance than the latter per mean square error, both networks provided reasonable stiffness predictions for implementation into the computational model.

A quantitative method for evaluating inferior glenohumeral joint stiffness using ultrasonography.

PubMed

Tsai, Wen-Wei; Lee, Ming-Yih; Yeh, Wen-Lin; Cheng, Shih-Chung; Soon, Kok-Soon; Lei, Kin Fong; Lin, Wen-Yen

2013-02-01

Subluxation of the affected shoulder in post-stroke patients is associated with nerve disorders and muscle fatigue. Clinicians must be able to accurately and reliably measure inferior glenohumeral subluxation in patients to provide appropriate treatment. However, quantitative methods for evaluating the laxity and stiffness of the glenohumeral joint (GHJ) are still being developed. The aim of this study was to develop a new protocol for evaluating the laxity and stiffness of the inferior GHJ using ultrasonography under optimal testing conditions and to investigate changes in the GHJ from a commercially available humerus brace and shoulder brace. Multistage inferior displacement forces were applied to create a glide between the most cephalad point on the visible anterosuperior surface of the humeral head and coracoid process in seven healthy volunteers. GHJ stiffness was defined as the slope of the linear regression line between the glides and different testing loads. The testing conditions were defined by different test loading mechanisms (n=2), shoulder constraining conditions (n=2), and loading modes (n=4). The optimal testing condition was defined as the condition with the least residual variance of measured laxity to the calculated stiffness under different testing loads. A paired t-test was used to compare the laxity and stiffness of the inferior GHJ using different braces. No significant difference was identified between the two test loading mechanisms (t=0.218, p=0.831) and two shoulder constraining conditions (t=-0.235, p=0.818). We concluded that ultrasonographic laxity measurements performed using a pulley set loading mechanism was as reliable as direct loading. Additionally, constraining the unloaded shoulder was proposed due to the lower mean residual variance value. Moreover, pulling the elbow downward with loading on the upper arm was suggested, as pulling the elbow downward with the elbow flexed and loading on the forearm may overestimate stiffness and pain in the inferior GHJ at the loading point due to friction between the wide belt and skin. Furthermore, subjects wearing a humerus brace with a belt, which creates the effect of lifting the humerus toward the acromion, had greater GHJ stiffness compared to subjects wearing a shoulder brace without a belt to lift the humerus under the proposed testing conditions. This study provides experimental evidence that shoulder braces may reduce GHJ laxity under an external load, implying that the use of a humeral brace can prevent subluxation in post-stroke patients. The resulting optimal testing conditions for measuring the laxity and stiffness of the GHJ is to constrain the unloaded shoulder and bend the loaded arm at the elbow with loading on the upper arm using a pulley system. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

A Biomechanical Simulation of the Effect of the Extrinsic Flexor Muscles on Finger Joint Flexion

DTIC Science & Technology

2001-10-25

vol. 44, pp. 493-504, 1997. [8] A.B. Leger and T.E. Milner, “The effect of eccentric exercise on intrinsic and reflex stiffness in the human hand...line of action of the tendons and the effective moment arms. After a certain point, the FDP tendon became slack, while the FDS tendon remained...link chain with three revolute joints and four links was created to model the index finger. The tendons from the extrinsic flexor muscles were

Tailored metal matrix composites for high-temperature performance

NASA Technical Reports Server (NTRS)

Morel, M. R.; Saravanos, D. A.; Chamis, C. C.

1992-01-01

A multi-objective tailoring methodology is presented to maximize stiffness and load carrying capacity of a metal matrix cross-ply laminated at elevated temperatures. The fabrication process and fiber volume ratio are used as the design variables. A unique feature is the concurrent effects from fabrication, residual stresses, material nonlinearity, and thermo-mechanical loading on the laminate properties at the post-fabrication phase. For a (0/90)(sub s) graphite/copper laminate, strong coupling was observed between the fabrication process, laminate characteristics, and thermo-mechanical loading. The multi-objective tailoring was found to be more effective than single objective tailoring. Results indicate the potential to increase laminate stiffness and load carrying capacity by controlling the critical parameters of the fabrication process and the laminate.

Juvenile hyaline fibromatosis: a case report and review of literature.

PubMed

Ribeiro, Sandra Lúcia; Guedes, Erilane L; Botan, Valeria; Barbosa, Alessandra; Freitas, Ernani J

2009-01-01

Juvenile hyaline fibromatosis (JHF) is a rare disease with autosomal recessive inheritance that occurs mainly in childhood and is characterized by the deposition of amorphous hyaline material in the skin and other organs. There are approximately 70 cases reported in the literature. Herein we describe the case of a 14-month-old boy with multiple cutaneous nodules around small and large joints, papulous skin lesions, hyperpigmented plaques and nodules in the perianal region, flexion contractures and stiffness of joints and diffuse osteoporosis. Symptoms were present since the second month of life. Histopathologic studies of joint nodulations demonstrated the presence of hyaline material, confirming the diagnosis of juvenile hyaline fibromatosis.

Endothelial permeability is controlled by spatially defined cytoskeletal mechanics: atomic force microscopy force mapping of pulmonary endothelial monolayer.

PubMed

Birukova, Anna A; Arce, Fernando T; Moldobaeva, Nurgul; Dudek, Steven M; Garcia, Joe G N; Lal, Ratnesh; Birukov, Konstantin G

2009-03-01

Actomyosin contraction directly regulates endothelial cell (EC) permeability, but intracellular redistribution of cytoskeletal tension associated with EC permeability is poorly understood. We used atomic force microscopy (AFM), EC permeability assays, and fluorescence microscopy to link barrier regulation, cell remodeling, and cytoskeletal mechanical properties in EC treated with barrier-protective as well as barrier-disruptive agonists. Thrombin, vascular endothelial growth factor, and hydrogen peroxide increased EC permeability, disrupted cell junctions, and induced stress fiber formation. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, hepatocyte growth factor, and iloprost tightened EC barriers, enhanced peripheral actin cytoskeleton and adherens junctions, and abolished thrombin-induced permeability and EC remodeling. AFM force mapping and imaging showed differential distribution of cell stiffness: barrier-disruptive agonists increased stiffness in the central region, and barrier-protective agents decreased stiffness in the center and increased it at the periphery. Attenuation of thrombin-induced permeability correlates well with stiffness changes from the cell center to periphery. These results directly link for the first time the patterns of cell stiffness with specific EC permeability responses.

Composite alginate gels for tunable cellular microenvironment mechanics

NASA Astrophysics Data System (ADS)

Khavari, Adele; Nydén, Magnus; Weitz, David A.; Ehrlicher, Allen J.

2016-08-01

The mechanics of the cellular microenvironment can be as critical as biochemistry in directing cell behavior. Many commonly utilized materials derived from extra-cellular-matrix create excellent scaffolds for cell growth, however, evaluating the relative mechanical and biochemical effects independently in 3D environments has been difficult in frequently used biopolymer matrices. Here we present 3D sodium alginate hydrogel microenvironments over a physiological range of stiffness (E = 1.85 to 5.29 kPa), with and without RGD binding sites or collagen fibers. We use confocal microscopy to measure the growth of multi-cellular aggregates (MCAs), of increasing metastatic potential in different elastic moduli of hydrogels, with and without binding factors. We find that the hydrogel stiffness regulates the growth and morphology of these cell clusters; MCAs grow larger and faster in the more rigid environments similar to cancerous breast tissue (E = 4-12 kPa) as compared to healthy tissue (E = 0.4-2 kpa). Adding binding factors from collagen and RGD peptides increases growth rates, and change maximum MCA sizes. These findings demonstrate the utility of these independently tunable mechanical/biochemistry gels, and that mechanical confinement in stiffer microenvironments may increase cell proliferation.

A parallel algorithm for generation and assembly of finite element stiffness and mass matrices

NASA Technical Reports Server (NTRS)

Storaasli, O. O.; Carmona, E. A.; Nguyen, D. T.; Baddourah, M. A.

1991-01-01

A new algorithm is proposed for parallel generation and assembly of the finite element stiffness and mass matrices. The proposed assembly algorithm is based on a node-by-node approach rather than the more conventional element-by-element approach. The new algorithm's generality and computation speed-up when using multiple processors are demonstrated for several practical applications on multi-processor Cray Y-MP and Cray 2 supercomputers.

Contribution of sensory feedback to plantar flexor muscle activation during push-off in adults with cerebral palsy.

PubMed

Frisk, Rasmus F; Jensen, Peter; Kirk, Henrik; Bouyer, Laurent J; Lorentzen, Jakob; Nielsen, Jens B

2017-12-01

Exaggerated sensory activity has been assumed to contribute to functional impairment following lesion of the central motor pathway. However, recent studies have suggested that sensory contribution to muscle activity during gait is reduced in stroke patients and children with cerebral palsy (CP). We investigated whether this also occurs in CP adults and whether daily treadmill training is accompanied by alterations in sensory contribution to muscle activity. Seventeen adults with CP and 12 uninjured individuals participated. The participants walked on a treadmill while a robotized ankle-foot orthosis applied unload perturbations at the ankle, thereby removing sensory feedback naturally activated during push-off. Reduction of electromyographic (EMG) activity in the soleus muscle caused by unloads was compared and related to kinematics and ankle joint stiffness measurements. Similar measures were obtained after 6 wk of gait training. We found that sensory contribution to soleus EMG activation was reduced in CP adults compared with uninjured adults. The lowest contribution of sensory feedback was found in participants with lowest maximal gait speed. This was related to increased ankle plantar flexor stiffness. Six weeks of gait training did not alter the contribution of sensory feedback. We conclude that exaggerated sensory activity is unlikely to contribute to impaired gait in CP adults, because sensory contribution to muscle activity during gait was reduced compared with in uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait so that a larger part of plantar flexor muscle activity must be generated by descending motor commands. NEW & NOTEWORTHY Findings suggest that adults with cerebral palsy have less contribution of sensory feedback to ongoing soleus muscle activation during push-off than uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait, and/or sensory feedback is less integrated with central motor commands in the activation of spinal motor neurons. Consequently, muscle activation must to a larger extent rely on descending drive, which is already decreased because of the cerebral lesion. Copyright © 2017 the American Physiological Society.

Estimation of continuous multi-DOF finger joint kinematics from surface EMG using a multi-output Gaussian Process.

PubMed

Ngeo, Jimson; Tamei, Tomoya; Shibata, Tomohiro

2014-01-01

Surface electromyographic (EMG) signals have often been used in estimating upper and lower limb dynamics and kinematics for the purpose of controlling robotic devices such as robot prosthesis and finger exoskeletons. However, in estimating multiple and a high number of degrees-of-freedom (DOF) kinematics from EMG, output DOFs are usually estimated independently. In this study, we estimate finger joint kinematics from EMG signals using a multi-output convolved Gaussian Process (Multi-output Full GP) that considers dependencies between outputs. We show that estimation of finger joints from muscle activation inputs can be improved by using a regression model that considers inherent coupling or correlation within the hand and finger joints. We also provide a comparison of estimation performance between different regression methods, such as Artificial Neural Networks (ANN) which is used by many of the related studies. We show that using a multi-output GP gives improved estimation compared to multi-output ANN and even dedicated or independent regression models.

Design Study for the Asteroid Redirect Vehicle (ARV) Composite Primary Bulkhead

NASA Technical Reports Server (NTRS)

Cressman, Thomas O.; Paddock, David A.

2017-01-01

A design study was undertaken of a carbon fiber primary bulkhead for a large solar electric propulsion (SEP) spacecraft. The bulkhead design, supporting up to 16 t of xenon propellant, progressed from one consisting of many simple parts with many complex joints, to one consisting of a few complex parts with a few simple joints. The unique capabilities of composites led to a topology that transitioned loads from bending to in-plane tension and shear, with low part count. This significantly improved bulkhead manufacturability, cost, and mass. The stiffness-driven structure utilized high-modulus M55J fiber unidirectional prepregs. A full-scale engineering demonstration unit (EDU) of the concept was used to demonstrate manufacturability of the concept. Actual labor data was obtained, which could be extrapolated to a full bulkhead. The effort demonstrated the practicality of using high-modulus fiber (HMF) composites for unique shape topologies that minimize mass and cost. The lessons are applicable to primary and secondary aerospace structures that are stiffness driven.

Free vibrations of a pultruded GFRP frame with different rotational stiffnesses of bolted joints

NASA Astrophysics Data System (ADS)

Boscato, G.; Russo, S.

2013-01-01

Experimental and numerical results for the dynamic response of an all-FRP (fiber-reinforced polymer) twodimensional frame in free vibration are presented. The frame was assembled of pultruded glass-fiber-reinforced polymer (GFRP) profiles and bolted beam-to-column connections with GFRP angles. To give a variable rotational stiffness to the four beam-to-column major-axis joints, all bolts were tightened by a constant torque of 10, 25, or 40 N · m. Experimental measurements were performed on the three configurations to identify the natural frequencies of the first vibration mode in the plane of the frame and to determine the ability of each structure to dissipate the initial acceleration imposed on it through damping. The results obtained are compared with analytical and finite-element calculations. It was found that an increased bolt torque improved the dynamic response of the GFRP frame by reducing its vibration time and maximum displacements and by enhancing its dissipation capacity.

Macrophage involvement affects matrix stiffness-related influences on cell osteogenesis under three-dimensional culture conditions.

PubMed

He, Xiao-Tao; Wu, Rui-Xin; Xu, Xin-Yue; Wang, Jia; Yin, Yuan; Chen, Fa-Ming

2018-04-15

Accumulating evidence indicates that the physicochemical properties of biomaterials exert profound influences on stem cell fate decisions. However, matrix-based regulation selected through in vitro analyses based on a given cell population do not genuinely reflect the in vivo conditions, in which multiple cell types are involved and interact dynamically. This study constitutes the first investigation of how macrophages (Mφs) in stiffness-tunable transglutaminase cross-linked gelatin (TG-gel) affect the osteogenesis of bone marrow-derived mesenchymal stem cells (BMMSCs). When a single cell type was cultured, low-stiffness TG-gels promoted BMMSC proliferation, whereas high-stiffness TG-gels supported cell osteogenic differentiation. However, Mφs in high-stiffness TG-gels were more likely to polarize toward the pro-inflammatory M1 phenotype. Using either conditioned medium (CM)-based incubation or Transwell-based co-culture, we found that Mφs encapsulated in the low-stiffness matrix exerted a positive effect on the osteogenesis of co-cultured BMMSCs. Conversely, Mφs in high-stiffness TG-gels negatively affected cell osteogenic differentiation. When both cell types were cultured in the same TG-gel type and placed into the Transwell system, the stiffness-related influences of Mφs on BMMSCs were significantly altered; both the low- and high-stiffness matrix induced similar levels of BMMSC osteogenesis. Although the best material parameter for synergistically affecting Mφs and BMMSCs remains unknown, our data suggest that Mφ involvement in the co-culture system alters previously identified material-related influences on BMMSCs, such as matrix stiffness-related effects, which were identified based on a culture system involving a single cell type. Such Mφ-stem cell interactions should be considered when establishing proper matrix parameter-associated cell regulation in the development of biomimetic biomaterials for regenerative applications. The substrate stiffness of a scaffold plays critical roles in modulating both reparative cells, such as mesenchymal stem cells (MSCs), and immune cells, such as macrophages (Mφs). Although the influences of material stiffness on either Mφs or MSCs, have been extensively described, how the two cell types respond to matrix cues to dynamically affect each other in a three-dimensional (3D) biosystem remains largely unknown. Here, we report our findings that, in a platform wherein Mφs and bone marrow-derived MSCs coexist, matrix stiffness can influence stem cell fate through both direct matrix-associated regulation and indirect Mφ-based modulation. Our data support future studies of the MSC-Mφ-matrix interplay in the 3D context to optimize matrix parameters for the development of the next biomaterial. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Muscular contribution to low-back loading and stiffness during standard and suspended push-ups.

PubMed

Beach, Tyson A C; Howarth, Samuel J; Callaghan, Jack P

2008-06-01

Push-up exercises are normally performed to challenge muscles that span upper extremity joints. However, it is also recognized that push-ups provide an effective abdominal muscle challenge, especially when the hands are in contact with a labile support surface. The purpose of this study was to compare trunk muscle activation levels and resultant intervertebral joint (IVJ) loading when standard and suspended push-ups were performed, and to quantify and compare the contribution of trunk muscles to IVJ rotational stiffness in both exercises. Eleven recreationally trained male volunteers performed sets of standard and suspended push-ups. Upper body kinematic, kinetic, and EMG data were collected and input into a 3D biomechanical model of the lumbar torso to quantify lumbar IVJ loading and the contributions of trunk muscles to IVJ rotational stiffness. When performing suspended push-ups, muscles of the abdominal wall and the latissimus dorsi were activated to levels that were significantly greater than those elicited when performing standard push-ups (p<.05). As a direct result of these increased activation levels, model-predicted muscle forces increased and consequently led to significantly greater mean (p=.0008) and peak (p=.0012) lumbar IVJ compressive forces when performing suspended push-ups. Also directly resulting from the increased activation levels of the abdominal muscles and the latissimus dorsi during suspended push-ups was increased muscular contribution to lumbar IVJ rotational stiffness (p<.05). In comparison to the standard version of the exercise, suspended push-ups appear to provide a superior abdominal muscle challenge. However, for individuals unable to tolerate high lumbar IVJ compressive loads, potential benefits gained by incorporating suspended push-ups into their resistance training regimen may be outweighed by the risk of overloading low-back tissues.

A simple model for the prediction of the discrete stiffness states of a homogeneous electrostatically tunable multi-layer beam

NASA Astrophysics Data System (ADS)

Bergamini, A.; Christen, R.; Motavalli, M.

2007-04-01

The adaptive modification of the mechanical properties of structures has been described as a key to a number of new or enhanced technologies, ranging from prosthetics to aerospace applications. Previous work reported the electrostatic tuning of the bending stiffness of simple sandwich structures by modifying the shear stress transfer parameters at the interface between faces and the compliant core of the sandwich. For this purpose, the choice of a sandwich structure presented considerable experimental advantages, such as the ability to obtain a large increase in stiffness by activating just two interfaces between the faces and the core of the beam. The hypothesis the development of structures with tunable bending stiffness is based on, is that by applying a normal stress at the interface between two layers of a multi-layer structure it is possible to transfer shear stresses from one layer to the other by means of adhesion or friction forces. The normal stresses needed to generate adhesion or friction can be generated by an electrostatic field across a dielectric layer interposed between the layers of a structure. The shear stress in the cross section of the structure (e.g. a beam) subjected to bending forces is transferred in full, if sufficiently large normal stresses and an adequate friction coefficient at the interface are given. Considering beams with a homogeneous cross-section, in which all layers are made of the same material and have the same width, eliminates the need to consider parameters such as the shear modulus of the material and the shear stiffness of the core, thus making the modelling work easier and the results more readily understood. The goal of the present work is to describe a numerical model of a homogeneous multi-layer beam. The model is validated against analytical solutions for the extreme cases of interaction at the interface (no friction and a high level of friction allowing for full shear stress transfer). The obtained model is used to better understand the processes taking place at the interfaces between layers, demonstrate the existence of discrete stiffness states and to find guidance for the selection of suitable dielectric layers for the generation of the electrostatic normal stresses needed for the shear stress transfer at the interface.

An Investigation of the Tensile Strength of a Composite-To-Metal Adhesive Joint

NASA Astrophysics Data System (ADS)

Tsouvalis, Nicholas G.; Karatzas, Vassilios A.

2011-04-01

The present study examines the feasibility of a simple concept composite-to-metal butt joint through the performance of both numerical and experimental studies. The composite part is made of glass/epoxy unidirectional layers made with the vacuum bag method. The geometry of the joint is typical for marine applications and corresponds to a low stiffness ratio. Two major parameters are investigated, namely the overlap length and the surface preparation of the steel adherent. Manufacturing of specimens and the procedure of the tensile tests are described in detail, giving hints for obtaining a better quality joint. Axial elongation and strains at various places of the joint were monitored and also numerically calculated. The tests revealed that the joint is quite effective, irrespectively of the steel surface preparation method. The failure loads are comparable and in some cases superior to other corresponding values found in the literature. The numerical models proved to adequately predict the structural response of the joint up to the loading where debonding starts.

Design Methodology for Scarf Repairs to Composite Structures

DTIC Science & Technology

2006-08-01

particularly for laminates containing unidirectional ( tape ) plies, where the variation in stiffness along the scarf is significant. (a) A scarf...London. p. 610-666. 5. Lubkin, J.L., A theory of adhesive scarf joints. Journal of Applied Mechanics, 1956. July 1957: p. 255-260. 6. Erdogan , F

Effects of phyllotaxy on biomechanical properties of stems of Cercis occidentalis (Fabaceae).

PubMed

Caringella, Marissa A; Bergman, Brett A; Stanfield, Ryan C; Ewers, Madeleine M; Bobich, Edward G; Ewers, Frank W

2014-01-01

Phyllotaxy, the arrangement of leaves on a stem, may impact the mechanical properties of woody stems several years after the leaves have been shed. We explored mechanical properties of a plant with alternate distichous phyllotaxy, with a row of leaves produced on each side of the stem, to determine whether the nodes behave as spring-like joints. Flexural stiffness of 1 cm diameter woody stems was measured in four directions with an Instron mechanical testing system; the xylem of the stems was then cut into node (former leaf junction) and nonnode segments for measurement of xylem density. Stems had 20% greater flexural stiffness in the plane perpendicular to the original leaf placement than in the parallel plane. The xylem in the node region was more flexible, but it had significantly greater tissue density than adjacent regions, contradicting the usual correlation between wood density and stiffness. Nodes can behave as spring-like joints in woody plants. For plagiotropic shoots, distichous phyllotaxy results in stems that resist up-and-down bending more than lateral back-and-forth movement. Thus, they may more effectively absorb applied loads from fruits, animals, wind, rain, and snow and resist stresses due to gravity without cracking and breaking. Under windy conditions, nodes may improve damping by absorbing vibrational energy and thus reducing oscillation damage. The effect of plant nodes also has biomimetic design implications for architects and material engineers.

Uncontrolled Manifold Reference Feedback Control of Multi-Joint Robot Arms

PubMed Central

Togo, Shunta; Kagawa, Takahiro; Uno, Yoji

2016-01-01

The brain must coordinate with redundant bodies to perform motion tasks. The aim of the present study is to propose a novel control model that predicts the characteristics of human joint coordination at a behavioral level. To evaluate the joint coordination, an uncontrolled manifold (UCM) analysis that focuses on the trial-to-trial variance of joints has been proposed. The UCM is a nonlinear manifold associated with redundant kinematics. In this study, we directly applied the notion of the UCM to our proposed control model called the “UCM reference feedback control.” To simplify the problem, the present study considered how the redundant joints were controlled to regulate a given target hand position. We considered a conventional method that pre-determined a unique target joint trajectory by inverse kinematics or any other optimization method. In contrast, our proposed control method generates a UCM as a control target at each time step. The target UCM is a subspace of joint angles whose variability does not affect the hand position. The joint combination in the target UCM is then selected so as to minimize the cost function, which consisted of the joint torque and torque change. To examine whether the proposed method could reproduce human-like joint coordination, we conducted simulation and measurement experiments. In the simulation experiments, a three-link arm with a shoulder, elbow, and wrist regulates a one-dimensional target of a hand through proposed method. In the measurement experiments, subjects performed a one-dimensional target-tracking task. The kinematics, dynamics, and joint coordination were quantitatively compared with the simulation data of the proposed method. As a result, the UCM reference feedback control could quantitatively reproduce the difference of the mean value for the end hand position between the initial postures, the peaks of the bell-shape tangential hand velocity, the sum of the squared torque, the mean value for the torque change, the variance components, and the index of synergy as well as the human subjects. We concluded that UCM reference feedback control can reproduce human-like joint coordination. The inference for motor control of the human central nervous system based on the proposed method was discussed. PMID:27462215

Motor Inhibition Affects the Speed But Not Accuracy of Aimed Limb Movements in an Insect

PubMed Central

Calas-List, Delphine; Clare, Anthony J.; Komissarova, Alexandra; Nielsen, Thomas A.

2014-01-01

When reaching toward a target, human subjects use slower movements to achieve higher accuracy, and this can be accompanied by increased limb impedance (stiffness, viscosity) that stabilizes movements against motor noise and external perturbation. In arthropods, the activity of common inhibitory motor neurons influences limb impedance, so we hypothesized that this might provide a mechanism for speed and accuracy control of aimed movements in insects. We recorded simultaneously from excitatory leg motor neurons and from an identified common inhibitory motor neuron (CI1) in locusts that performed natural aimed scratching movements. We related limb movement kinematics to recorded motor activity and demonstrate that imposed alterations in the activity of CI1 influenced these kinematics. We manipulated the activity of CI1 by injecting depolarizing or hyperpolarizing current or killing the cell using laser photoablation. Naturally higher levels of inhibitory activity accompanied faster movements. Experimentally biasing the firing rate downward, or stopping firing completely, led to slower movements mediated by changes at several joints of the limb. Despite this, we found no effect on overall movement accuracy. We conclude that inhibitory modulation of joint stiffness has effects across most of the working range of the insect limb, with a pronounced effect on the overall velocity of natural movements independent of their accuracy. Passive joint forces that are greatest at extreme joint angles may enhance accuracy and are not affected by motor inhibition. PMID:24872556

Investigating the role of radixin in modulation of stereocilia length and stiffness

NASA Astrophysics Data System (ADS)

Prasad, Sonal; Fridberger, Anders

2018-05-01

Mammalian hearing depends on deflection of stereocilia on the sensory outer hair cells of the inner ear. Previous data indicate that the stiffness of outer hair cell stereocilia are actively regulated. The molecular mechanism that regulate the deflection of stereocilia are presently less known. The aim of the study is to investigate the mechanistic pathway that underlie the stiffness modulation of outer hair cell stereocilia. Our hypothesis is that the membrane-cytoskeleton linker protein radixin, which is present at high concentration in stereocilia, could contribute to stiffness regulation. To test this hypothesis, we use the radixin blocker DX-52-1 which binds strongly and specifically to radixin. Time-resolved confocal imaging was used to visualize the sound-evoked motion of stereocilia in a semi-intact preparation of the guinea pig temporal bone. Cochlear microphonic potentials were also measured, using electrodes positioned in scala media. We found that the DX-52-1 inhibitor leads to an increase in stereocilia movements and decline in the amplitude of the cochlear microphonic potential. However, DX-52-1 caused a paradoxical increase in electromotility. These results suggest that radixin has a functionally important regulatory role in the mature inner ear.

Modeling Progressive Failure of Bonded Joints Using a Single Joint Finite Element

NASA Technical Reports Server (NTRS)

Stapleton, Scott E.; Waas, Anthony M.; Bednarcyk, Brett A.

2010-01-01

Enhanced finite elements are elements with an embedded analytical solution which can capture detailed local fields, enabling more efficient, mesh-independent finite element analysis. In the present study, an enhanced finite element is applied to generate a general framework capable of modeling an array of joint types. The joint field equations are derived using the principle of minimum potential energy, and the resulting solutions for the displacement fields are used to generate shape functions and a stiffness matrix for a single joint finite element. This single finite element thus captures the detailed stress and strain fields within the bonded joint, but it can function within a broader structural finite element model. The costs associated with a fine mesh of the joint can thus be avoided while still obtaining a detailed solution for the joint. Additionally, the capability to model non-linear adhesive constitutive behavior has been included within the method, and progressive failure of the adhesive can be modeled by using a strain-based failure criteria and re-sizing the joint as the adhesive fails. Results of the model compare favorably with experimental and finite element results.

Pericellular plasma clot negates the influence of scaffold stiffness on chondrogenic differentiation.

PubMed

Arora, Aditya; Kothari, Anjaney; Katti, Dhirendra S

2016-12-01

Matrix stiffness is known to play a pivotal role in cellular differentiation. Studies have shown that soft scaffolds (<2-3kPa) promote cellular aggregation and chondrogenesis, whereas, stiffer ones (>10kPa) show poor chondrogenesis in vitro. In this work we investigated if fibrin matrix from clotted blood can act as a soft surrogate which nullifies the influence of the underlying stiff scaffold, thus promoting chondrogenesis irrespective of bulk scale scaffold stiffness. For this we performed in vitro chondrogenesis on soft (∼1.5kPa) and stiff (∼40kPa) gelatin scaffolds in the presence and absence of pericellular plasma clot. Our results demonstrated that in absence of pericellular plasma clot, chondrocytes showed efficient condensation and cartilaginous matrix secretion only on soft scaffolds, whereas, in presence of pericellular plasma clot, cell rounding and cartilaginous matrix secretion was observed in both soft and stiff scaffolds. More specifically, significantly higher collagen II, chondroitin sulfate and aggrecan deposition was observed in soft scaffolds, and soft and stiff scaffolds with pericellular plasma clot as compared to stiff scaffolds without pericellular plasma clot. Moreover, collagen type I, a fibrocartilage/bone marker was significantly higher only in stiff scaffolds without plasma clot. Therefore, it can be concluded that chondrocytes surrounded by a soft fibrin network were unable to sense the stiffness of the underlying scaffold/substrate and hence facilitate chondrogenesis even on stiff scaffolds. This understanding can have significant implications in the design of scaffolds for cartilage tissue engineering. Cell fate is influenced by the mechanical properties of cell culture substrates. Outside the body, cartilage progenitor cells express significant amounts of cartilage-specific markers on soft scaffolds but not on stiff scaffolds. However, when implanted in joints, stiff scaffolds show equivalent expression of markers as seen in soft scaffolds. This disparity in existing literature prompted our study. Our results suggest that encapsulation of cells in a soft plasma clot, present in any surgical intervention, prevents their perception of stiffness of the underlying scaffold, and hence the ability to distinguish between soft and stiff scaffolds vanishes. This finding would aid the design of new scaffolds that elicit cartilage-like biochemical properties while simultaneously being mechanically comparable to cartilage tissue. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Feedback-controlled and programmed stretching of the ankle plantarflexors and dorsiflexors in stroke: effects of a 4-week intervention program.

PubMed

Selles, Ruud W; Li, Xiaoyan; Lin, Fang; Chung, Sun G; Roth, Elliot J; Zhang, Li-Qun

2005-12-01

To investigate the effect of repeated feedback-controlled and programmed "intelligent" stretching of the ankle plantar- and dorsiflexors to treat subjects with ankle spasticity and/or contracture in stroke. Noncontrolled trial. Institutional research center. Subjects with spasticity and/or contracture after stroke. Stretching of the plantar- and dorsiflexors of the ankle 3 times a week for 45 minutes during a 4-week period by using a feedback-controlled and programmed stretching device. Passive and active range of motion (ROM), muscle strength, joint stiffness, joint viscous damping, reflex excitability, comfortable walking speed, and subjective experiences of the subjects. Significant improvements were found in the passive ROM, maximum voluntary contraction, ankle stiffness, and comfortable walking speed. The visual analog scales indicated very positive subjective evaluation in terms of the comfort of stretching and the effect on their involved ankle. Repeated feedback-controlled or intelligent stretching had a positive influence on the joint properties of the ankle with spasticity and/or contracture after stroke. The stretching device may be an effective and safe alternative to manual passive motion treatment by a therapist and has potential to be used to repeatedly and regularly stretch the ankle of subjects with spasticity and/or contracture without daily involvement of clinicians or physical therapists.

Sensitivity analysis of primary resonances and bifurcations of a controlled piecewise-smooth system with negative stiffness

NASA Astrophysics Data System (ADS)

Huang, Dongmei; Xu, Wei

2017-11-01

In this paper, the combination of the cubic nonlinearity and time delay is proposed to improve the performance of a piecewise-smooth (PWS) system with negative stiffness. Dynamical properties, feedback control performance and symmetry-breaking bifurcation are mainly considered for a PWS system with negative stiffness under nonlinear position and velocity feedback control. For the free vibration system, the homoclinic-like orbits are firstly derived. Then, the amplitude-frequency response of the controlled system is obtained analytically in aspect of the Lindstedt-Poincaré method and the method of multiple scales, which is also verified through the numerical results. In this regard, a softening-type behavior, which directly leads to the multi-valued responses, is illustrated over the negative position feedback. Especially, the five-valued responses in which three branches of them are stable are found. And complex multi-valued characteristics are also observed in the force-amplitude responses. Furthermore, for explaining the effectiveness of feedback control, the equivalent damping and stiffness are also introduced. Sensitivity of the system response to the feedback gain and time delay is comprehensively considered and interesting dynamical properties are found. Relatively, from the perspective of suppressing the maximum amplitude and controlling the resonance stability, the selection of the feedback parameters is discussed. Finally, the symmetry-breaking bifurcation and chaotic motion are considered.

Radial stiffness improvement of a flywheel system using multi-surface superconducting levitation

NASA Astrophysics Data System (ADS)

Basaran, Sinan; Sivrioglu, Selim

2017-03-01

The goal of this research study is the maximization of the levitation force in a flywheel system by the use of more than one permanent magnet with a single ring-shaped HTS material. An analytical model for the radial stiffness of the ring HTS-PM is derived using the frozen image approach. The experimental works are carried out for different polarizations of the permanent magnets, and radial stiffness values are obtained from the radial force measurements. The rotational test of the flywheel system is also realized for different cases. Finally, natural frequencies of the flywheel superconducting magnetic bearing system are experimentally obtained for different combinations of the permanent magnets using a frequency analyzer.

Aging impairs smooth muscle-mediated regulation of aortic stiffness: a defect in shock absorption function?

PubMed Central

Gao, Yuan Z.; Saphirstein, Robert J.; Yamin, Rina; Suki, Bela

2014-01-01

Increased aortic stiffness is an early and independent biomarker of cardiovascular disease. Here we tested the hypothesis that vascular smooth muscle cells (VSMCs) contribute significantly to aortic stiffness and investigated the mechanisms involved. The relative contributions of VSMCs, focal adhesions (FAs), and matrix to stiffness in mouse aorta preparations at optimal length and with confirmed VSMC viability were separated by the use of small-molecule inhibitors and activators. Using biomechanical methods designed for minimal perturbation of cellular function, we directly quantified changes with aging in aortic material stiffness. An alpha adrenoceptor agonist, in the presence of NG-nitro-l-arginine methyl ester (l-NAME) to remove interference of endothelial nitric oxide, increases stiffness by 90–200% from baseline in both young and old mice. Interestingly, increases are robustly suppressed by the Src kinase inhibitor PP2 in young but not old mice. Phosphotyrosine screening revealed, with aging, a biochemical signature of markedly impaired agonist-induced FA remodeling previously associated with Src signaling. Protein expression measurement confirmed a decrease in Src expression with aging. Thus we report here an additive model for the in vitro biomechanical components of the mouse aortic wall in which 1) VSMCs are a surprisingly large component of aortic stiffness at physiological lengths and 2) regulation of the VSMC component through FA signaling and hence plasticity is impaired with aging, diminishing the aorta's normal shock absorption function in response to stressors. PMID:25128168

Reverse Dynamization: Influence of Fixator Stiffness on the Mode and Efficiency of Large-Bone-Defect Healing at Different Doses of rhBMP-2.

PubMed

Glatt, Vaida; Bartnikowski, Nicole; Quirk, Nicholas; Schuetz, Michael; Evans, Christopher

2016-04-20

Reverse dynamization is a technology for enhancing the healing of osseous defects. With use of an external fixator, the axial stiffness across the defect is initially set low and subsequently increased. The purpose of the study described in this paper was to explore the efficacy of reverse dynamization under different conditions. Rat femoral defects were stabilized with external fixators that allowed the stiffness to be modulated on living animals. Recombinant human bone morphogenetic protein-2 (rhBMP-2) was implanted into the defects on a collagen sponge. Following a dose-response experiment, 5.5 μg of rhBMP-2 was placed into the defect under conditions of very low (25.4-N/mm), low (114-N/mm), medium (185-N/mm), or high (254-N/mm) stiffness. Reverse dynamization was evaluated with 2 different starting stiffnesses: low (114 N/mm) and very low (25.4 N/mm). In both cases, high stiffness (254 N/mm) was imposed after 2 weeks. Healing was assessed with radiographs, micro-computed tomography (μCT), histological analysis, and mechanical testing. In the absence of dynamization, the medium-stiffness fixators provided the best healing. Reverse dynamization starting with very low stiffness was detrimental to healing. However, with low initial stiffness, reverse dynamization considerably improved healing with minimal residual cartilage, enhanced cortication, increased mechanical strength, and smaller callus. Histological analysis suggested that, in all cases, healing provoked by rhBMP-2 occurred by endochondral ossification. These data confirm the potential utility of reverse dynamization as a way of improving bone healing but indicate that the stiffness parameters need to be selected carefully. Reverse dynamization may reduce the amount of rhBMP-2 needed to induce healing of recalcitrant osseous lesions, reduce the time to union, and decrease the need for prolonged external fixation. Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.

Developing a multi-joint upper limb exoskeleton robot for diagnosis, therapy, and outcome evaluation in neurorehabilitation.

PubMed

Ren, Yupeng; Kang, Sang Hoon; Park, Hyung-Soon; Wu, Yi-Ning; Zhang, Li-Qun

2013-05-01

Arm impairments in patients post stroke involve the shoulder, elbow and wrist simultaneously. It is not very clear how patients develop spasticity and reduced range of motion (ROM) at the multiple joints and the abnormal couplings among the multiple joints and the multiple degrees-of-freedom (DOF) during passive movement. It is also not clear how they lose independent control of individual joints/DOFs and coordination among the joints/DOFs during voluntary movement. An upper limb exoskeleton robot, the IntelliArm, which can control the shoulder, elbow, and wrist, was developed, aiming to support clinicians and patients with the following integrated capabilities: 1) quantitative, objective, and comprehensive multi-joint neuromechanical pre-evaluation capabilities aiding multi-joint/DOF diagnosis for individual patients; 2) strenuous and safe passive stretching of hypertonic/deformed arm for loosening up muscles/joints based on the robot-aided diagnosis; 3) (assistive/resistive) active reaching training after passive stretching for regaining/improving motor control ability; and 4) quantitative, objective, and comprehensive neuromechanical outcome evaluation at the level of individual joints/DOFs, multiple joints, and whole arm. Feasibility of the integrated capabilities was demonstrated through experiments with stroke survivors and healthy subjects.

The optimal design of UAV wing structure

NASA Astrophysics Data System (ADS)

Długosz, Adam; Klimek, Wiktor

2018-01-01

The paper presents an optimal design of UAV wing, made of composite materials. The aim of the optimization is to improve strength and stiffness together with reduction of the weight of the structure. Three different types of functionals, which depend on stress, stiffness and the total mass are defined. The paper presents an application of the in-house implementation of the evolutionary multi-objective algorithm in optimization of the UAV wing structure. Values of the functionals are calculated on the basis of results obtained from numerical simulations. Numerical FEM model, consisting of different composite materials is created. Adequacy of the numerical model is verified by results obtained from the experiment, performed on a tensile testing machine. Examples of multi-objective optimization by means of Pareto-optimal set of solutions are presented.

Measurement of the UH-60A Hub Large Rotor Test Apparatus Control System Stiffness

NASA Technical Reports Server (NTRS)

Kufeld, Robert M.

2014-01-01

This purpose of this report is to provides details of the measurement of the control system stiffness of the UH-60A rotor hub mounted on the Large Rotor Test Apparatus (UH-60A/LRTA). The UH-60A/LRTA was used in the 40- by 80-Foot Wind Tunnel to complete the full-scale wind tunnel test portion of the NASA / ARMY UH-60A Airloads Program. This report describes the LRTA control system and highlights the differences between the LRTA and UH-60A aircraft. The test hardware, test setup, and test procedures are also described. Sample results are shown, including the azimuthal variation of the measured control system stiffness for three different loadings and two different dynamic actuator settings. Finally, the azimuthal stiffness is converted to fixed system values using multi-blade transformations for input to comprehensive rotorcraft prediction codes.

Exercise Helps Ease Arthritis Pain and Stiffness

MedlinePlus

... you control your weight Enhance your quality of life Improve your balance Though you might think exercise will aggravate your ... involved. Your doctor or a physical therapist can work with you to find the exercise plan that gives you the most benefit with the least aggravation of your joint pain. ...

BioMot exoskeleton - Towards a smart wearable robot for symbiotic human-robot interaction.

PubMed

Bacek, Tomislav; Moltedo, Marta; Langlois, Kevin; Prieto, Guillermo Asin; Sanchez-Villamanan, Maria Carmen; Gonzalez-Vargas, Jose; Vanderborght, Bram; Lefeber, Dirk; Moreno, Juan C

2017-07-01

This paper presents design of a novel modular lower-limb gait exoskeleton built within the FP7 BioMot project. Exoskeleton employs a variable stiffness actuator in all 6 joints, a directional-flexibility structure and a novel physical humanrobot interfacing, which allows it to deliver the required output while minimally constraining user's gait by providing passive degrees of freedom. Due to modularity, the exoskeleton can be used as a full lower-limb orthosis, a single-joint orthosis in any of the three joints, and a two-joint orthosis in a combination of any of the two joints. By employing a simple torque control strategy, the exoskeleton can be used to deliver user-specific assistance, both in gait rehabilitation and in assisting people suffering musculoskeletal impairments. The result of the presented BioMot efforts is a low-footprint exoskeleton with powerful compliant actuators, simple, yet effective torque controller and easily adjustable flexible structure.

Concrete pedestals for high-performance semiconductor production equipment

NASA Astrophysics Data System (ADS)

Vogen, Wayne; Franklin, Craig L.; Morneault, Joseph

1999-09-01

Concrete pedestals have many vibration and stiffness characteristics that make them a superior choice for sensitive semiconductor production equipment including scanners, scanning electron microscopes, focused ion beam millers and optical inspection equipment. Among the advantages of concrete pedestals are high inherent damping, monolithic construction that eliminates low stiffness joints common in steep pedestals, ability to reuse and ease of installation. Steel pedestals that have plates attached to the top of the frame are easily excited by acoustic excitation, especially in the range from 50 Hertz to 400 Hertz. Concrete pedestals do not suffer from this phenomenon because of the high mass and damping of the top surface.

Design of a 6-DOF upper limb rehabilitation exoskeleton with parallel actuated joints.

PubMed

Chen, Yanyan; Li, Ge; Zhu, Yanhe; Zhao, Jie; Cai, Hegao

2014-01-01

In this paper, a 6-DOF wearable upper limb exoskeleton with parallel actuated joints which perfectly mimics human motions is proposed. The upper limb exoskeleton assists the movement of physically weak people. Compared with the existing upper limb exoskeletons which are mostly designed using a serial structure with large movement space but small stiffness and poor wearable ability, a prototype for motion assistance based on human anatomy structure has been developed in our design. Moreover, the design adopts balls instead of bearings to save space, which simplifies the structure and reduces the cost of the mechanism. The proposed design also employs deceleration processes to ensure that the transmission ratio of each joint is coincident.

Adhesive-bonded double-lap joints. [analytical solutions for static load carrying capacity

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1973-01-01

Explicit analytical solutions are derived for the static load carrying capacity of double-lap adhesive-bonded joints. The analyses extend the elastic solution Volkersen and cover adhesive plasticity, adherend stiffness imbalance and thermal mismatch between the adherends. Both elastic-plastic and bi-elastic adhesive representations lead to the explicit result that the influence of the adhesive on the maximum potential bond strength is defined uniquely by the strain energy in shear per unit area of bond. Failures induced by peel stresses at the ends of the joint are examined. This failure mode is particularly important for composite adherends. The explicit solutions are sufficiently simple to be used for design purposes

76 FR 69161 - Airworthiness Directives; Bombardier, Inc. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-08

...: A number of reports of aileron control stiffness have been received on Bombardier Regional Jet... determined that an additional maintenance task is required. * * * [A]ileron control stiffness during flight... methods: Federal eRulemaking Portal: Go to http://www.regulations.gov . Follow the instructions for...

Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility

PubMed Central

Ng, Mei Rosa; Besser, Achim

2012-01-01

The mechanical microenvironment is known to influence single-cell migration; however, the extent to which mechanical cues affect collective migration of adherent cells is not well understood. We measured the effects of varying substrate compliance on individual cell migratory properties in an epithelial wound-healing assay. Increasing substrate stiffness increased collective cell migration speed, persistence, and directionality as well as the coordination of cell movements. Dynamic analysis revealed that wounding initiated a wave of motion coordination from the wound edge into the sheet. This was accompanied by a front-to-back gradient of myosin-II activation and establishment of cell polarity. The propagation was faster and farther reaching on stiff substrates, indicating that substrate stiffness affects the transmission of directional cues. Manipulation of myosin-II activity and cadherin–catenin complexes revealed that this transmission is mediated by coupling of contractile forces between neighboring cells. Thus, our findings suggest that the mechanical environment integrates in a feedback with cell contractility and cell–cell adhesion to regulate collective migration. PMID:23091067

Baseline predictors of aortic stiffness progression among multi-ethnic Asians with type 2 diabetes.

PubMed

Moh, Mei Chung; Sum, Chee Fang; Tavintharan, Subramaniam; Ang, Keven; Lee, Simon Biing Ming; Tang, Wern Ee; Lim, Su Chi

2017-05-01

This 3-year prospective study aimed to identify baseline parameters that predicted the progression of carotid-femoral pulse wave velocity (cf-PWV), which was used to evaluate aortic stiffness, among Singapore's multi-ethnic Asians with type 2 diabetes (T2DM). The cf-PWV was measured by the gold-standard tonometry method in 994 T2DM subjects at baseline and follow-up. The annual rate of cf-PWV change was calculated, and individuals above the 90 th percentile with rate≥1.42 m/s per year were regarded as rapid progressors (n = 104). In a subgroup analysis of subjects with normal cf-PWV at 1 st visit (n = 611), incident aortic stiffness was defined as follow-up cf-PWV≥10 m/s (n = 188). The total cohort (mean age:57 ± 10 years; 53.4% Chinese, 20.4% Malay, 22.9% Indian, 3.2% 'Others') displayed a median annual cf-PWV progression rate of 0.2 m/s. Adjusted multivariate regression analyses showed that baseline age, cf-PWV and body mass index (BMI) constantly predicted follow-up cf-PWV, annual cf-PWV progression rate, rapid cf-PWV progression, and incident aortic stiffness. Paradoxically, lower baseline cf-PWV was associated with elevated annual cf-PWV progression rate and rapid progressors. This inverse relationship remained significant across ethnicities after ethnic stratification. Higher BMI independently predicted cf-PWV progression in Chinese and Indians, but not in Malay and 'Others' ethnic groups. Increased age was a significant predictor in Chinese and 'Others' ethnicities. We demonstrated that baseline BMI is a modifiable independent risk factor of cf-PWV progression and incident aortic stiffness. Therefore, better obesity management may impede aortic stiffness in Singapore's T2DM patients, especially in the Chinese and Indians. Copyright © 2017. Published by Elsevier B.V.

Articular cartilage. Part II. The osteoarthritic joint.

PubMed

Muehleman, C; Arsenis, C H

1995-05-01

Articular hyaline cartilage, though a metabolically active tissue, has limited capacity for repair. Though the integrity of the cartilage is dependent upon a certain level of force placed upon it, excessive force leads to damage. It is when the breakdown of the cartilage exceeds the capacity of the cartilage for repair that osteoarthritis results. At present, pharmacologic treatment of osteoarthritis is focused toward the control of pain and stiffness. This treatment, however, masks the symptoms of the disease and effectively allows the patient to do further damage to the joint.

Management of proximal interphalangeal joint injuries

PubMed Central

Freiberg, Arnis

2007-01-01

Injuries to the proximal interphalangeal joint are common but frequently missed. They are often overtreated by prolonged immobilization, resulting in stiffness, which may be permanent. The purpose of the present article is to briefly review the relevant anatomy and biomechanics, present an approach to physical examination and diagnosis, and propose a practical clinical classification. The treatment of the most severe injury – the intra-articular fracture dislocation – is controversial. The various treatment options are discussed, based on personal experience and a review of the literature. A list of relevant references is presented. PMID:19554177

External rotation elastic bands at the lower limb decrease rearfoot eversion during walking: a preliminary proof of concept

PubMed Central

Souza, Thales R.; Araújo, Vanessa L.; Silva, Paula L.; Carvalhais, Viviane O. C.; Resende, Renan A.; Fonseca, Sérgio T.

2016-01-01

ABSTRACT Background Reducing rearfoot eversion is a commonly desired effect in clinical practice to prevent or treat musculoskeletal dysfunction. Interventions that pull the lower limb into external rotation may reduce rearfoot eversion. Objective This study investigated whether the use of external rotation elastic bands, of different levels of stiffness, will decrease rearfoot eversion during walking. We hypothesized that the use of elastic bands would decrease rearfoot eversion and that the greater the band stiffness, the greater the eversion reduction. Method Seventeen healthy participants underwent three-dimensional kinematic analysis of the rearfoot and shank. The participants walked on a treadmill with and without high- and low-stiffness bands. Frontal-plane kinematics of the rearfoot-shank joint complex was obtained during the stance phase of walking. Repeated-measures ANOVAs were used to compare discrete variables that described rearfoot eversion-inversion: mean eversion-inversion; eversion peak; and eversion-inversion range of motion. Results The low-stiffness and high-stiffness bands significantly decreased eversion and increased mean eversion-inversion (p≤0.037) and eversion peak (p≤0.006) compared with the control condition. Both bands also decreased eversion-inversion range of motion (p≤0.047) compared with control by reducing eversion. The high-stiffness band condition was not significantly different from the low-stiffness band condition for any variables (p≥0.479). Conclusion The results indicated that the external rotation bands decreased rearfoot eversion during walking. This constitutes preliminary experimental evidence suggesting that increasing external rotation moments at the lower limb may reduce rearfoot eversion, which needs further testing. PMID:27849289

Importance of mechanics and kinematics in determining the stiffness contribution of the vertebral column during body-caudal-fin swimming in fishes.

PubMed

Nowroozi, Bryan N; Brainerd, Elizabeth L

2014-02-01

Whole-body stiffness in fishes has important consequences for swimming mode, speed and efficiency, but the contribution of vertebral column stiffness to whole-body stiffness is unclear. In our opinion, this lack of clarity is due in part to the lack of studies that have measured both in vitro mechanical properties of the vertebral column as well as in vivo vertebral kinematics in the same species. Some lack of clarity may also come from real variation in the mechanical role of the vertebral column across species. Previous studies, based on either mechanics or kinematics alone, suggest species-specific variation in vertebral column locomotor function that ranges from highly stiff regimes that contribute greatly to whole-body stiffness, and potentially act as a spring, to highly compliant regimes that only prohibit excessive flexion of the intervertebral joints. We review data collected in combined investigations of both mechanics and kinematics of three species, Myxine glutinosa, Acipenser transmontanus, and Morone saxatilis, to illustrate how mechanical testing within the context of the in vivo kinematics more clearly distinguishes the role of the vertebral column in each species. In addition, we identify species for which kinematic data are available, but mechanical data are lacking. We encourage further investigation of these species to fill these mechanical data gaps. Finally, we hope these future combined analyses will identify certain morphological, mechanical, or kinematic parameters that might be associated with certain vertebral column functional regimes with respect to body stiffness. Copyright © 2013 Elsevier GmbH. All rights reserved.

Joint stability characteristics of the ankle complex in female athletes with histories of lateral ankle sprain, part II: clinical experience using arthrometric measurement.

PubMed

Kovaleski, John E; Heitman, Robert J; Gurchiek, Larry R; Hollis, J M; Liu, Wei; Pearsall, Albert W

2014-01-01

This is part II of a 2-part series discussing stability characteristics of the ankle complex. In part I, we used a cadaver model to examine the effects of sectioning the lateral ankle ligaments on anterior and inversion motion and stiffness of the ankle complex. In part II, we wanted to build on and apply these findings to the clinical assessment of ankle-complex motion and stiffness in a group of athletes with a history of unilateral ankle sprain. To examine ankle-complex motion and stiffness in a group of athletes with reported history of lateral ankle sprain. Cross-sectional study. University research laboratory. Twenty-five female college athletes (age = 19.4 ± 1.4 years, height = 170.2 ± 7.4 cm, mass = 67.3 ± 10.0 kg) with histories of unilateral ankle sprain. All ankles underwent loading with an ankle arthrometer. Ankles were tested bilaterally. The dependent variables were anterior displacement, anterior end-range stiffness, inversion rotation, and inversion end-range stiffness. Anterior displacement of the ankle complex did not differ between the uninjured and sprained ankles (P = .37), whereas ankle-complex rotation was greater for the sprained ankles (P = .03). The sprained ankles had less anterior and inversion end-range stiffness than the uninjured ankles (P < .01). Changes in ankle-complex laxity and end-range stiffness were detected in ankles with histories of sprain. These results indicate the presence of altered mechanical characteristics in the soft tissues of the sprained ankles.

Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading.

PubMed

Eiken, Ola; Mekjavic, Igor B; Kölegård, Roger

2014-03-01

Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness was determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-week period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50%. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 weeks of sustained horizontal bedrest, induced threefold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.

Nonlinear Conservation Laws and Finite Volume Methods

NASA Astrophysics Data System (ADS)

Leveque, Randall J.

Introduction Software Notation Classification of Differential Equations Derivation of Conservation Laws The Euler Equations of Gas Dynamics Dissipative Fluxes Source Terms Radiative Transfer and Isothermal Equations Multi-dimensional Conservation Laws The Shock Tube Problem Mathematical Theory of Hyperbolic Systems Scalar Equations Linear Hyperbolic Systems Nonlinear Systems The Riemann Problem for the Euler Equations Numerical Methods in One Dimension Finite Difference Theory Finite Volume Methods Importance of Conservation Form - Incorrect Shock Speeds Numerical Flux Functions Godunov's Method Approximate Riemann Solvers High-Resolution Methods Other Approaches Boundary Conditions Source Terms and Fractional Steps Unsplit Methods Fractional Step Methods General Formulation of Fractional Step Methods Stiff Source Terms Quasi-stationary Flow and Gravity Multi-dimensional Problems Dimensional Splitting Multi-dimensional Finite Volume Methods Grids and Adaptive Refinement Computational Difficulties Low-Density Flows Discrete Shocks and Viscous Profiles Start-Up Errors Wall Heating Slow-Moving Shocks Grid Orientation Effects Grid-Aligned Shocks Magnetohydrodynamics The MHD Equations One-Dimensional MHD Solving the Riemann Problem Nonstrict Hyperbolicity Stiffness The Divergence of B Riemann Problems in Multi-dimensional MHD Staggered Grids The 8-Wave Riemann Solver Relativistic Hydrodynamics Conservation Laws in Spacetime The Continuity Equation The 4-Momentum of a Particle The Stress-Energy Tensor Finite Volume Methods Multi-dimensional Relativistic Flow Gravitation and General Relativity References

Multi-Plane High Speed Balancing Techniques and the Use of a High Specific Stiffness Ti-Borsic Material for Vibration Control.

DTIC Science & Technology

1980-02-01

maneuver conditions, and transmit the net axial thrust force between the turbine and fan sections due to pressure and aero dynamic gas loads . 49 Lm...stiffness composite material shaft. Both~~ balancing demonstration and the composite shaft design ad as their objective the management of small turbofan ...CONFIGURATIONS 99 LIST OF ILLUSTRATIONS Figure Title Page 1 High Speed Balancing Program Schedule 4 2 Teledyne CAE Model 471-11DX Turbofan Engine

A Materials Approach in the Development of Multi-Threat Warfighter Head Protection

DTIC Science & Technology

2008-12-01

TUSJp TYSlp ’--- --"IO,,5083-="" H13 .’ (AI) ’AZ31B-H2’",(~",),,-- __ Figure 6. Specific Strength of Mg vs. Al Alloy Armor Plate of current interest because...perfonnance in metal alloys, and higher stiffness typically contributes to enhanced energy absorption upon ballistic impact ; therefore, one would predict...Helmets, and ballistic helmets in particular. have not been dominated by stiffness requirements but rather other properties (e.g., crash, impact

Regulation of matrix stiffness on the epithelial-mesenchymal transition of breast cancer cells under hypoxia environment

NASA Astrophysics Data System (ADS)

Lv, Yonggang; Chen, Can; Zhao, Boyuan; Zhang, Xiaomei

2017-06-01

Substrate stiffness and hypoxia are associated with tumor development and progression, respectively. However, the synergy of them on the biological behavior of human breast cancer cell is still largely unknown. This study explored how substrate stiffness regulates the cell phenotype, viability, and epithelial-mesenchymal transition (EMT) of human breast cancer cells MCF-7 under hypoxia (1% O2). TRITC-phalloidin staining showed that MCF-7 cells transformed from round to irregular polygon with stiffness increase either in normoxia or hypoxia. While being accompanied with the upward tendency from a 0.5- to a 20-kPa substrate, the percentage of cell apoptosis was significantly higher in hypoxia than that in normoxia, especially on the 20-kPa substrate. Additionally, it was hypoxia, but not normoxia, that promoted the EMT of MCF-7 by upregulating hypoxia-inducible factor-1α (HIF-1α), vimentin, Snail 1, and matrix metalloproteinase 2 (MMP 2) and 9 (MMP 9), and downregulating E-cadherin simultaneously regardless of the change of substrate stiffness. In summary, this study discovered that hypoxia and stiffer substrate (20 kPa) could synergistically induce phenotype change, apoptosis, and EMT of MCF-7 cells. Results of this study have an important significance on further exploring the synergistic effect of stiffness and hypoxia on the EMT of breast cancer cells and its molecular mechanism.

Associations between yoga practice and joint problems: a cross-sectional survey among 9151 Australian women.

PubMed

Lauche, Romy; Schumann, Dania; Sibbritt, David; Adams, Jon; Cramer, Holger

2017-07-01

Yoga exercises have been associated with joint problems recently, indicating that yoga practice might be potentially dangerous for joint health. This study aimed to analyse whether regular yoga practice is associated with the frequency of joint problems in upper middle-aged Australian women. Women aged 62-67 years from the Australian Longitudinal Study on Women's Health (ALSWH) were questioned in 2013 whether they experienced regular joint pain or problems in the past 12 months and whether they regularly practiced yoga. Associations of joint problems with yoga practice were analysed using Chi-squared tests and multiple logistic regression modelling. Of 9151 women, 29.8% reported regular problems with stiff or painful joints, and 15.2, 11.9, 18.1 and 15.9% reported regular problems with shoulders, hips, knees and feet, respectively, in the past 12 months. Yoga was practiced sometimes by 10.1% and often by 8.4% of women. Practicing yoga was not associated with upper or lower limb joint problems. No association between yoga practice and joint problems has been identified. Further studies are warranted for conclusive judgement of benefits and safety of yoga in relation to joint problems.

The cyclic fatigue behavior of adhesive joints

NASA Astrophysics Data System (ADS)

Kinloch, A. J.; Toh, T.

1995-06-01

In the last six months we have: (1) Concentrated our efforts on the fatigue failure of carbon-fiber PEEK/AFl63 lap joints, and in particular we have started to predict the life time of single-lap joints under cyclic fatigue loading. The analysis is based on data obtained from double cantilever beam (DCB) fracture mechanics tests; (2) Further, we have been successful in measuring the rate of crack growth in lap joints during fatigue fracture using ultrasonic scanning; (3) Preliminary test data on the static fracture of glass-fiber reinforced poly(phenylene sulphide) (PPS)/AF163 joints have also been studied; and (4) A comparison has been made in computing the critical strain energy release rate G(sub c) for the glass-fiber PPS/AF163 joints based on the compliance method, beam theory and corrected beam theory. The last method accounts for large non-linear deflections and the associated crack root rotations along with the necessary corrections for the increase in stiffness introduced by the presence of end blocks.

Bio-inspired flexible joints with passive feathering for robotic fish pectoral fins.

PubMed

Behbahani, Sanaz Bazaz; Tan, Xiaobo

2016-05-04

In this paper a novel flexible joint is proposed for robotic fish pectoral fins, which enables a swimming behavior emulating the fin motions of many aquatic animals. In particular, the pectoral fin operates primarily in the rowing mode, while undergoing passive feathering during the recovery stroke to reduce hydrodynamic drag on the fin. The latter enables effective locomotion even with symmetric base actuation during power and recovery strokes. A dynamic model is developed to facilitate the understanding and design of the joint, where blade element theory is used to calculate the hydrodynamic forces on the pectoral fins, and the joint is modeled as a paired torsion spring and damper. Experimental results on a robotic fish prototype are presented to illustrate the effectiveness of the joint mechanism, validate the proposed model, and indicate the utility of the proposed model for the optimal design of joint depth and stiffness in achieving the trade-off between swimming speed and mechanical efficiency.

Dietary potassium regulates vascular calcification and arterial stiffness.

PubMed

Sun, Yong; Byon, Chang Hyun; Yang, Youfeng; Bradley, Wayne E; Dell'Italia, Louis J; Sanders, Paul W; Agarwal, Anupam; Wu, Hui; Chen, Yabing

2017-10-05

Vascular calcification is a risk factor that predicts adverse cardiovascular complications of several diseases including atherosclerosis. Reduced dietary potassium intake has been linked to cardiovascular diseases such as hypertension and incidental stroke, although the underlying molecular mechanisms remain largely unknown. Using the ApoE-deficient mouse model, we demonstrated for the first time to our knowledge that reduced dietary potassium (0.3%) promoted atherosclerotic vascular calcification and increased aortic stiffness, compared with normal (0.7%) potassium-fed mice. In contrast, increased dietary potassium (2.1%) attenuated vascular calcification and aortic stiffness. Mechanistically, reduction in the potassium concentration to the lower limit of the physiological range increased intracellular calcium, which activated a cAMP response element-binding protein (CREB) signal that subsequently enhanced autophagy and promoted vascular smooth muscle cell (VSMC) calcification. Inhibition of calcium signals and knockdown of either CREB or ATG7, an autophagy regulator, attenuated VSMC calcification induced by low potassium. Consistently, elevated autophagy and CREB signaling were demonstrated in the calcified arteries from low potassium diet-fed mice as well as aortic arteries exposed to low potassium ex vivo. These studies established a potentially novel causative role of dietary potassium intake in regulating atherosclerotic vascular calcification and stiffness, and uncovered mechanisms that offer opportunities to develop therapeutic strategies to control vascular disease.

Dietary potassium regulates vascular calcification and arterial stiffness

PubMed Central

Sun, Yong; Byon, Chang Hyun; Yang, Youfeng; Bradley, Wayne E.; Dell’Italia, Louis J.; Agarwal, Anupam; Wu, Hui

2017-01-01

Vascular calcification is a risk factor that predicts adverse cardiovascular complications of several diseases including atherosclerosis. Reduced dietary potassium intake has been linked to cardiovascular diseases such as hypertension and incidental stroke, although the underlying molecular mechanisms remain largely unknown. Using the ApoE-deficient mouse model, we demonstrated for the first time to our knowledge that reduced dietary potassium (0.3%) promoted atherosclerotic vascular calcification and increased aortic stiffness, compared with normal (0.7%) potassium–fed mice. In contrast, increased dietary potassium (2.1%) attenuated vascular calcification and aortic stiffness. Mechanistically, reduction in the potassium concentration to the lower limit of the physiological range increased intracellular calcium, which activated a cAMP response element–binding protein (CREB) signal that subsequently enhanced autophagy and promoted vascular smooth muscle cell (VSMC) calcification. Inhibition of calcium signals and knockdown of either CREB or ATG7, an autophagy regulator, attenuated VSMC calcification induced by low potassium. Consistently, elevated autophagy and CREB signaling were demonstrated in the calcified arteries from low potassium diet–fed mice as well as aortic arteries exposed to low potassium ex vivo. These studies established a potentially novel causative role of dietary potassium intake in regulating atherosclerotic vascular calcification and stiffness, and uncovered mechanisms that offer opportunities to develop therapeutic strategies to control vascular disease. PMID:28978809

Noninvasively measuring oxygen saturation of human finger-joint vessels by multi-transducer functional photoacoustic tomography

NASA Astrophysics Data System (ADS)

Deng, Zijian; Li, Changhui

2016-06-01

Imaging small blood vessels and measuring their functional information in finger joint are still challenges for clinical imaging modalities. In this study, we developed a multi-transducer functional photoacoustic tomography (PAT) system and successfully imaged human finger-joint vessels from ˜1 mm to <0.2 mm in diameter. In addition, the oxygen saturation (SO2) values of these vessels were also measured. Our results demonstrate that PAT can provide both anatomical and functional information of individual finger-joint vessels with different sizes, which might help the study of finger-joint diseases, such as rheumatoid arthritis.

Finite Element Analysis of Increasing Column Section and CFRP Reinforcement Method under Different Axial Compression Ratio

NASA Astrophysics Data System (ADS)

Jinghai, Zhou; Tianbei, Kang; Fengchi, Wang; Xindong, Wang

2017-11-01

Eight less stirrups in the core area frame joints are simulated by ABAQUS finite element numerical software. The composite reinforcement method is strengthened with carbon fiber and increasing column section, the axial compression ratio of reinforced specimens is 0.3, 0.45 and 0.6 respectively. The results of the load-displacement curve, ductility and stiffness are analyzed, and it is found that the different axial compression ratio has great influence on the bearing capacity of increasing column section strengthening method, and has little influence on carbon fiber reinforcement method. The different strengthening schemes improve the ultimate bearing capacity and ductility of frame joints in a certain extent, composite reinforcement joints strengthening method to improve the most significant, followed by increasing column section, reinforcement method of carbon fiber reinforced joints to increase the minimum.

Fuzzy variable impedance control based on stiffness identification for human-robot cooperation

NASA Astrophysics Data System (ADS)

Mao, Dachao; Yang, Wenlong; Du, Zhijiang

2017-06-01

This paper presents a dynamic fuzzy variable impedance control algorithm for human-robot cooperation. In order to estimate the intention of human for co-manipulation, a fuzzy inference system is set up to adjust the impedance parameter. Aiming at regulating the output fuzzy universe based on the human arm’s stiffness, an online stiffness identification method is developed. A drag interaction task is conducted on a 5-DOF robot with variable impedance control. Experimental results demonstrate that the proposed algorithm is superior.

Multi-component lightweight gearwheels with deep-drawn wheel body for automotive applications

NASA Astrophysics Data System (ADS)

Benkert, Tim; Hiller, Maria; Volk, Wolfram

2017-09-01

Multi-component gearwheels offer great lightweight opportunities for automotive applications. An assembly of a gear ring and a wheel body joined by press fit replaces the monolithic gearwheel. To save weight, the wheel body uses lightweight design. This lightweight design influences the assembled gearwheel’s mechanical properties like stiffness, weight and torque capacity. Further, the wheel body material influences the mentioned properties as well. In this paper, the effects of the lightweight wheel body manufactured by deep-drawing on the mechanical properties of the assembled gearwheel are investigated. Three different wheel body designs are examined regarding their stiffness and weight compared to a reference gearwheel. Using the best design, the influence of five materials with increasing yield strength on the maximum torque the gearwheel can transmit is studied. All research is done virtually using Abaqus 6.12-3.

Modeling, simulation and optimization approaches for design of lightweight car body structures

NASA Astrophysics Data System (ADS)

Kiani, Morteza

Simulation-based design optimization and finite element method are used in this research to investigate weight reduction of car body structures made of metallic and composite materials under different design criteria. Besides crashworthiness in full frontal, offset frontal, and side impact scenarios, vibration frequencies, static stiffness, and joint rigidity are also considered. Energy absorption at the component level is used to study the effectiveness of carbon fiber reinforced polymer (CFRP) composite material with consideration of different failure criteria. A global-local design strategy is introduced and applied to multi-objective optimization of car body structures with CFRP components. Multiple example problems involving the analysis of full-vehicle crash and body-in-white models are used to examine the effect of material substitution and the choice of design criteria on weight reduction. The results of this study show that car body structures that are optimized for crashworthiness alone may not meet the vibration criterion. Moreover, optimized car body structures with CFRP components can be lighter with superior crashworthiness than the baseline and optimized metallic structures.

Structural design and static analysis of a double-ring deployable truss for mesh antennas

NASA Astrophysics Data System (ADS)

Xu, Yan; Guan, Fuling; Chen, Jianjun; Zheng, Yao

2012-12-01

This paper addresses the structural design, the deployment control design, the static analysis and the model testing of a new double-ring deployable truss that is intended for large mesh antennas. This deployable truss is a multi-DOF (degree-of-freedom), over-constrained mechanism. Two kinds of deployable basic elements were introduced, as well as a process to synthesise the structure of the deployable truss. The geometric equations were formulated to determine the length of each strut, including the effects of the joint size. A DOF evaluation showed that the mechanism requires two active cables and requires deployment control. An open-loop control system was designed to control the rotational velocities of two motors. The structural stiffness of the truss was assessed by static analysis that considered the effects of the constraint condition and the pre-stress of the passive cables. A 4.2-metre demonstration model of an antenna was designed and fabricated. The geometry and the deployment behaviour of the double-ring truss were validated by the experiments using this model.

Continuous Passive Motion Provides Good Pain Control in Patients with Adhesive Capsulitis

ERIC Educational Resources Information Center

Dundar, Umit; Toktas, Hasan; Cakir, Tuncay; Evcik, Deniz; Kavuncu, Vural

2009-01-01

Painful stiffening of the shoulder, "frozen shoulder" is a common cause of shoulder pain and disability. Continuous passive motion (CPM) is an established method of preventing joint stiffness and of overcoming it. A randomized, comparative prospective clinical trial was planned to compare the early response with different rehabilitation…

Effect of spine motion on mobility in quadruped running

NASA Astrophysics Data System (ADS)

Chen, Dongliang; Liu, Qi; Dong, Litao; Wang, Hong; Zhang, Qun

2014-11-01

Most of current running quadruped robots have similar construction: a stiff body and four compliant legs. Many researches have indicated that the stiff body without spine motion is a main factor in limitation of robots' mobility. Therefore, investigating spine motion is very important to build robots with better mobility. A planar quadruped robot is designed based on cheetahs' morphology. There is a spinal driving joint in the body of the robot. When the spinal driving joint acts, the robot has spine motion; otherwise, the robot has not spine motion. Six group prototype experiments with the robot are carried out to study the effect of spine motion on mobility. In each group, there are two comparative experiments: the spinal driving joint acts in one experiment but does not in the other experiment. The results of the prototype experiments indicate that the average speeds of the robot with spine motion are 8.7%-15.9% larger than those of the robot without spine motion. Furthermore, a simplified sagittal plane model of quadruped mammals is introduced. The simplified model also has a spinal driving joint. Using a similar process as the prototype experiments, six group simulation experiments with the simplified model are conducted. The results of the simulation experiments show that the maximum rear leg horizontal thrusts of the simplified mode with spine motion are 68.2%-71.3% larger than those of the simplified mode without spine motion. Hence, it is found that spine motion can increase the average running speed and the intrinsic reason of speed increase is the improvement of the maximum rear leg horizontal thrust.

Multifunctional Lattices with Low Thermal Expansion and Low Thermal Conductivity

NASA Astrophysics Data System (ADS)

Xu, Hang; Liu, Lu; Pasini, Damiano

Systems in space are vulnerable to large temperature changes when travelling into and out of the Earth's shadow. Variations in temperature can lead to undesired geometric changes in susceptible applications requiring very fine precision. In addition, temperature-sensitive electronic equipment hosted in a satellite needs adequate thermal-control to guarantee a moderate ambient temperature. To address these specifications, materials with low coefficient of thermal expansion (CTE) and low coefficient of thermal conductivity (CTC) over a wide range of temperatures are often sought, especially for bearing components in satellites. Besides low CTE and low CTC, these materials should also provide desirable stiffness, strength and extraordinarily low mass. This work presents ultralightweight bi-material lattices with tunable CTE and CTC, besides high stiffness and strength. We show that the compensation of the thermal expansion and joint rotation at the lattice joints can be used as an effective strategy to tailor thermomechanical performance. Proof-of-concept lattices are fabricated from Al and Ti alloy sheets via a simple snap-fit technique and vacuum brazing, and their CTE and CTC are assessed via a combination of experiments and theory. Corresponding Author.

Global Gene Expression Differences in Joints of Mice with Divergent Post Traumatic Osteoarthritis Phenotypes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kibui, J.

Osteoarthritis (OA) is a debilitating joint disease characterized by cartilage degradation which prompts pain, stiffness and swelling. Contributing factors include age, genetics, obesity, injury and overuse of joints. OA is defined by an acute phase and a chronic phase whereby inflammation and degeneration of articular cartilage and other tissues is followed by joint pain and limited mobility. Patients remain asymptomatic until substantial joint damage has occurred and therefore rely on long term surgical joint replacement and pain management as their sole treatment options. For this reason, there is an increasing need to identify early stage osteoarthritis biomarkers. Our study aimedmore » to identify and characterize gene expression variances in 3 different mouse strains (STR/ort, C57BL/6 and MRL/MpJ) with different susceptibility to post traumatic osteoarthritis (PTOA). Through RNA sequence analysis of whole knee joint RNA, we identified differentially expressed genes associated with the initial stages of PTOA in relation to mice with divergent phenotypes. These results will help elucidate potential mechanisms responsible for PTOA outcomes.« less

Equilibrium-point control of human elbow-joint movement under isometric environment by using multichannel functional electrical stimulation

PubMed Central

Matsui, Kazuhiro; Hishii, Yasuo; Maegaki, Kazuya; Yamashita, Yuto; Uemura, Mitsunori; Hirai, Hiroaki; Miyazaki, Fumio

2014-01-01

Functional electrical stimulation (FES) is considered an effective technique for aiding quadriplegic persons. However, the human musculoskeletal system has highly non-linearity and redundancy. It is thus difficult to stably and accurately control limbs using FES. In this paper, we propose a simple FES method that is consistent with the motion-control mechanism observed in humans. We focus on joint motion by a pair of agonist-antagonist muscles of the musculoskeletal system, and define the “electrical agonist-antagonist muscle ratio (EAA ratio)” and “electrical agonist-antagonist muscle activity (EAA activity)” in light of the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, respectively, to extract the equilibrium point and joint stiffness from electromyography (EMG) signals. These notions, the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, are based on the hypothesis that the equilibrium point and stiffness of the agonist-antagonist motion system are controlled by the central nervous system. We derived the transfer function between the input EAA ratio and force output of the end-point. We performed some experiments in an isometric environment using six subjects. This transfer-function model is expressed as a cascade-coupled dead time element and a second-order system. High-speed, high-precision, smooth control of the hand force were achieved through the agonist-antagonist muscle stimulation pattern determined by this transfer function model. PMID:24987326

Equilibrium-point control of human elbow-joint movement under isometric environment by using multichannel functional electrical stimulation.

PubMed

Matsui, Kazuhiro; Hishii, Yasuo; Maegaki, Kazuya; Yamashita, Yuto; Uemura, Mitsunori; Hirai, Hiroaki; Miyazaki, Fumio

2014-01-01

Functional electrical stimulation (FES) is considered an effective technique for aiding quadriplegic persons. However, the human musculoskeletal system has highly non-linearity and redundancy. It is thus difficult to stably and accurately control limbs using FES. In this paper, we propose a simple FES method that is consistent with the motion-control mechanism observed in humans. We focus on joint motion by a pair of agonist-antagonist muscles of the musculoskeletal system, and define the "electrical agonist-antagonist muscle ratio (EAA ratio)" and "electrical agonist-antagonist muscle activity (EAA activity)" in light of the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, respectively, to extract the equilibrium point and joint stiffness from electromyography (EMG) signals. These notions, the agonist-antagonist muscle ratio and agonist-antagonist muscle activity, are based on the hypothesis that the equilibrium point and stiffness of the agonist-antagonist motion system are controlled by the central nervous system. We derived the transfer function between the input EAA ratio and force output of the end-point. We performed some experiments in an isometric environment using six subjects. This transfer-function model is expressed as a cascade-coupled dead time element and a second-order system. High-speed, high-precision, smooth control of the hand force were achieved through the agonist-antagonist muscle stimulation pattern determined by this transfer function model.

Nonlinear Analysis of Bonded Composite Single-LAP Joints

NASA Technical Reports Server (NTRS)

Oterkus, E.; Barut, A.; Madenci, E.; Smeltzer, S. S.; Ambur, D. R.

2004-01-01

This study presents a semi-analytical solution method to analyze the geometrically nonlinear response of bonded composite single-lap joints with tapered adherend edges under uniaxial tension. The solution method provides the transverse shear and normal stresses in the adhesive and in-plane stress resultants and bending moments in the adherends. The method utilizes the principle of virtual work in conjunction with von Karman s nonlinear plate theory to model the adherends and the shear lag model to represent the kinematics of the thin adhesive layer between the adherends. Furthermore, the method accounts for the bilinear elastic material behavior of the adhesive while maintaining a linear stress-strain relationship in the adherends. In order to account for the stiffness changes due to thickness variation of the adherends along the tapered edges, their in-plane and bending stiffness matrices are varied as a function of thickness along the tapered region. The combination of these complexities results in a system of nonlinear governing equilibrium equations. This approach represents a computationally efficient alternative to finite element method. Comparisons are made with corresponding results obtained from finite-element analysis. The results confirm the validity of the solution method. The numerical results present the effects of taper angle, adherend overlap length, and the bilinear adhesive material on the stress fields in the adherends, as well as the adhesive, of a single-lap joint

Habitual Minimalist Shod Running Biomechanics and the Acute Response to Running Barefoot.

PubMed

Tam, Nicholas; Darragh, Ian A J; Divekar, Nikhil V; Lamberts, Robert P

2017-09-01

The aim of the study was to determine whether habitual minimalist shoe runners present with purported favorable running biomechanithat reduce running injury risk such as initial loading rate. Eighteen minimalist and 16 traditionally cushioned shod runners were assessed when running both in their preferred training shoe and barefoot. Ankle and knee joint kinetics and kinematics, initial rate of loading, and footstrike angle were measured. Sagittal ankle and knee joint stiffness were also calculated. Results of a two-factor ANOVA presented no group difference in initial rate of loading when participants were running either shod or barefoot; however, initial loading rate increased for both groups when running barefoot (p=0.008). Differences in footstrike angle were observed between groups when running shod, but not when barefoot (minimalist:8.71±8.99 vs. traditional: 17.32±11.48 degrees, p=0.002). Lower ankle joint stiffness was found in both groups when running barefoot (p=0.025). These findings illustrate that risk factors for injury potentially differ between the two groups. Shoe construction differences do change mechanical demands, however, once habituated to the demands of a given shoe condition, certain acute favorable or unfavorable responses may be moderated. The purported benefits of minimalist running shoes in mimicking habitual barefoot running is questioned, and risk of injury may not be attenuated. © Georg Thieme Verlag KG Stuttgart · New York.

A structurally adaptive space crane concept for assembling space systems on orbit

NASA Technical Reports Server (NTRS)

Dorsey, John T.; Sutter, Thomas R.; Wu, K. C.

1992-01-01

A space crane concept is presented which is based on erectable truss hardware to achieve high stiffness and low mass booms and articulating-truss joints which can be assembled on orbit. The hardware is characterized by linear load-deflection response and is structurally predictable. The crane can be reconfigured into different geometries to meet future assembly requirements. Articulating-truss joint concepts with significantly different geometries are analyzed and found to have similar static and dynamic performance, which indicates that criteria other than structural and kinematic performance can be used to select a joint. Passive damping and an open-loop preshaped command input technique greatly enhance the structural damping in the space crane and may preclude the need for an active vibrations suppression system.

Mechanical Impedance of the Non-loaded Lower Leg with Relaxed Muscles in the Transverse Plane

PubMed Central

Ficanha, Evandro Maicon; Ribeiro, Guilherme Aramizo; Rastgaar, Mohammad

2015-01-01

This paper describes the protocols and results of the experiments for the estimation of the mechanical impedance of the humans’ lower leg in the External–Internal direction in the transverse plane under non-load bearing condition and with relaxed muscles. The objectives of the estimation of the lower leg’s mechanical impedance are to facilitate the design of passive and active prostheses with mechanical characteristics similar to the humans’ lower leg, and to define a reference that can be compared to the values from the patients suffering from spasticity. The experiments were performed with 10 unimpaired male subjects using a lower extremity rehabilitation robot (Anklebot, Interactive Motion Technologies, Inc.) capable of applying torque perturbations to the foot. The subjects were in a seated position, and the Anklebot recorded the applied torques and the resulting angular movement of the lower leg. In this configuration, the recorded dynamics are due mainly to the rotations of the ankle’s talocrural and the subtalar joints, and any contribution of the tibiofibular joints and knee joint. The dynamic mechanical impedance of the lower leg was estimated in the frequency domain with an average coherence of 0.92 within the frequency range of 0–30 Hz, showing a linear correlation between the displacement and the torques within this frequency range under the conditions of the experiment. The mean magnitude of the stiffness of the lower leg (the impedance magnitude averaged in the range of 0–1 Hz) was determined as 4.9 ± 0.74 Nm/rad. The direct estimation of the quasi-static stiffness of the lower leg results in the mean value of 5.8 ± 0.81 Nm/rad. An analysis of variance shows that the estimated values for the stiffness from the two experiments are not statistically different. PMID:26697424

Changes in biomechanical properties of glenohumeral joint capsules with adhesive capsulitis by repeated capsule-preserving hydraulic distensions with saline solution and corticosteroid.

PubMed

Koh, Eun S; Chung, Sun G; Kim, Tae Uk; Kim, Hee Chan

2012-12-01

To investigate whether capsule-preserving hydraulic distension with saline solution and corticosteroid for adhesive capsulitis induces biomechanical alterations in glenohumeral joint capsules along with clinical improvements. A case series. University outpatient clinic of physical medicine and rehabilitation. Eighteen patients with unilateral adhesive capsulitis. INTERVENTION AND MAIN OUTCOME MEASUREMENTS: Three hydraulic distensions with saline solution and corticosteroid were performed with 1-month intervals. To avoid rupturing capsules, all distensions were monitored by using real-time pressure-volume curves. Stiffness, maximal volume capacity, and pressure at the maximal volume capacity of the capsule were measured at each intervention. Clinical parameters, such as pain and range of motion, were recorded before, 3 days after, and 1 month after each distension. Stiffness decreased (47.6 ± 27.1 mm Hg/mL to 31.7 ± 18.4 mm Hg/mL to 24.2 ± 14.0 mm Hg/mL, mean SD) and maximal volume capacity increased (18.8 ± 7.3 mL to 20.5 ± 7.5 mL to 24.2 ± 7.0 mL, mean SD) significantly (P = .001 for both) at each repeated hydraulic distension. Pressure at the maximal volume capacity tended to decrease, but the decrements were not statistically significant (P = .662). The clinical parameters were significantly improved throughout and 1 month after the 3 repeat procedures (P < .05 for all). Capsule-preserving hydraulic distension changed the biomechanical properties of the glenohumeral joint capsule, lessening the stiffness and enlarging the volume capacity. These alterations were accompanied by improved range of motion and relief of pain. Repeated capsule-preserving hydraulic distension with saline solution and corticosteroid would be useful to treat adhesive capsulitis and to evaluate the treatment results. Copyright © 2012 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Dynamic response characteristics of steel portal frames having semi-rigid joints under sinusoidal wave excitation

NASA Astrophysics Data System (ADS)

Bhatti, Abdul Qadir

2017-12-01

To demonstrate the characteristics of the nonlinear response of steel frames, an elastic dynamic response analysis of the semi-rigid frame is performed under the harmonic wave. The semi-rigid contact is represented by the alternating spring which is given stiffness by a three-parameter energy model which approaches the hysterical curve by hardening model. The properties of spectra and hysteric curves are presented. This study shows that (1) the greater the acceleration input capacitance the smaller the instant connection capability and the smaller is the response. (2) However, by allowing an extreme increase in capacitance input acceleration, response spectra can be increased as the contact stiffness results near zero.

The effect of ankle foot orthosis stiffness on the energy cost of walking: a simulation study.

PubMed

Bregman, D J J; van der Krogt, M M; de Groot, V; Harlaar, J; Wisse, M; Collins, S H

2011-11-01

In stroke and multiple sclerosis patients, gait is frequently hampered by a reduced ability to push-off with the ankle caused by weakness of the plantar-flexor muscles. To enhance ankle push-off and to decrease the high energy cost of walking, spring-like carbon-composite Ankle Foot Orthoses are frequently prescribed. However, it is unknown what Ankle Foot Orthoses stiffness should be used to obtain the most efficient gait. The aim of this simulation study was to gain insights into the effect of variation in Ankle Foot Orthosis stiffness on the amount of energy stored in the Ankle Foot Orthosis and the energy cost of walking. We developed a two-dimensional forward-dynamic walking model with a passive spring at the ankle representing the Ankle Foot Orthosis and two constant torques at the hip for propulsion. We varied Ankle Foot Orthosis stiffness while keeping speed and step length constant. We found an optimal stiffness, at which the energy delivered at the hip joint was minimal. Energy cost decreased with increasing energy storage in the ankle foot orthosis, but the most efficient gait did not occur with maximal energy storage. With maximum storage, push-off occurred too late to reduce the impact of the contralateral leg with the floor. Maximum return prior to foot strike was also suboptimal, as push-off occurred too early and its effects were subsequently counteracted by gravity. The optimal Ankle Foot Orthosis stiffness resulted in significant push-off timed just prior to foot strike and led to greater ankle plantar-flexion velocity just before contralateral foot strike. Our results suggest that patient energy cost might be reduced by the proper choice of Ankle Foot Orthosis stiffness. Copyright © 2011 Elsevier Ltd. All rights reserved.

Joint Stability Characteristics of the Ankle Complex in Female Athletes With Histories of Lateral Ankle Sprain, Part II: Clinical Experience Using Arthrometric Measurement

PubMed Central

Kovaleski, John E.; Heitman, Robert J.; Gurchiek, Larry R.; Hollis, J. M.; Liu, Wei; IV, Albert W. Pearsall

2014-01-01

Context: This is part II of a 2-part series discussing stability characteristics of the ankle complex. In part I, we used a cadaver model to examine the effects of sectioning the lateral ankle ligaments on anterior and inversion motion and stiffness of the ankle complex. In part II, we wanted to build on and apply these findings to the clinical assessment of ankle-complex motion and stiffness in a group of athletes with a history of unilateral ankle sprain. Objective: To examine ankle-complex motion and stiffness in a group of athletes with reported history of lateral ankle sprain. Design: Cross-sectional study. Setting: University research laboratory. Patients or Other Participants: Twenty-five female college athletes (age = 19.4 ± 1.4 years, height = 170.2 ± 7.4 cm, mass = 67.3 ± 10.0 kg) with histories of unilateral ankle sprain. Intervention(s): All ankles underwent loading with an ankle arthrometer. Ankles were tested bilaterally. Main Outcome Measure(s): The dependent variables were anterior displacement, anterior end-range stiffness, inversion rotation, and inversion end-range stiffness. Results: Anterior displacement of the ankle complex did not differ between the uninjured and sprained ankles (P = .37), whereas ankle-complex rotation was greater for the sprained ankles (P = .03). The sprained ankles had less anterior and inversion end-range stiffness than the uninjured ankles (P < .01). Conclusions: Changes in ankle-complex laxity and end-range stiffness were detected in ankles with histories of sprain. These results indicate the presence of altered mechanical characteristics in the soft tissues of the sprained ankles. PMID:24568223

Temporary ipsilateral stiff shoulder after operative fixation of distal radial fractures.

PubMed

Cha, Soo Min; Shin, Hyun Dae; Hwang, Sung Jin

2017-06-01

This study was conducted to identify variables affecting the development of temporary stiff shoulder after operative fixation for distal radial fractures (DRF). The study retrospectively analyzed 167 patients who had undergone internal fixation using volar locking plate for DRF between 2010 and 2013. Group 1 was denoted as the "normal group," and group 2 was denoted as the "stiff shoulder group." Basic demographic factors evaluated included age, sex, bone mineral density (BMD), and the dominancy. Also investigated were radiologic variables, including concurrent fractures of the styloid process, positive ulnar variances, classification of DRF, and morphologic type of the distal radioulnar joint. Finally, the type of plate, methods used for postoperative protection, and time of union were analyzed. Group 1 consisted of 114 patients, and group 2 consisted of 53 patients. On overall univariate analysis, BMD, hand dominancy, and the protective methods after plating were significantly different between the 2 groups. On multivariate analysis, a lower BMD and injury on the nondominant side were significant factors for shoulder stiffness. Stiffness was significantly higher in patients with a mean BMD < -2.6 than in patients with a mean BMD ≥ -2.6. At the final follow-up, all of the 53 patients in group 2 were relieved of the symptoms of a stiff shoulder. A lower BMD and injury on the nondominant distal radius were distinct factors for the development of a stiff shoulder after operative fixation in DRF. Fortunately, nonoperative treatments, such as stretching exercises/injections, were useful for the relief of these symptoms in the short-term follow-up. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

The Relationship Between Shoulder Stiffness and Rotator Cuff Healing: A Study of 1,533 Consecutive Arthroscopic Rotator Cuff Repairs.

PubMed

McNamara, William J; Lam, Patrick H; Murrell, George A C

2016-11-16

Retear and stiffness are not uncommon outcomes of rotator cuff repair. The purpose of this study was to evaluate the relationship between rotator cuff repair healing and shoulder stiffness. A total of 1,533 consecutive shoulders had an arthroscopic rotator cuff repair by a single surgeon. Patients assessed their shoulder stiffness using a Likert scale preoperatively and at 1, 6, 12, and 24 weeks (6 months) postoperatively, and examiners evaluated passive range of motion preoperatively and at 6, 12, and 24 weeks postoperatively. Repair integrity was determined by ultrasound evaluation at 6 months. After rotator cuff repair, there was an overall significant loss of patient-ranked and examiner-assessed shoulder motion at 6 weeks compared with preoperative measurements (p < 0.0001), a partial recovery at 12 weeks, and a full recovery at 24 weeks. Shoulders that were stiff before surgery were more likely to be stiff at 6, 12, and, to a lesser extent, 24 weeks after surgery (r = 0.10 to 0.31; p < 0.0001). A stiffer shoulder at 6 and 12 weeks (but not 24 weeks) postoperatively correlated with better rotator cuff integrity at 6 months postoperatively (r = 0.11 to 0.18; p < 0.001). The retear rate of patients with ≤20° of external rotation at 6 weeks postoperatively was 7%, while the retear rate of patients with >20° of external rotation at 6 weeks was 15% (p < 0.001). In patients who developed stiffness after surgery, a rotator cuff repair was more likely to heal. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.

Net ankle quasi-stiffness is influenced by walking speed but not age for older adult women.

PubMed

Collins, John D; Arch, Elisa S; Crenshaw, Jeremy R; Bernhardt, Kathie A; Khosla, Sundeep; Amin, Shreyasee; Kaufman, Kenton R

2018-03-26

Insufficient plantar flexor resistance due to plantar flexor weakness, an impairment common in patient populations, causes substantial gait deficits. The bending stiffness of passive-dynamic ankle-foot orthoses (PD-AFOs) has the capacity to replace lost plantar flexor resistance. Many patients who are prescribed PD-AFOs are older adults. While PD-AFO bending stiffness should be customized for patients, a method to objectively prescribe this stiffness does not exist. Quantifying natural plantar flexor resistance during non-pathological gait could provide a reference value for objectively prescribing PD-AFO bending stiffness. This study investigated the effect of age on plantar flexor resistance in 113 participants above the age of 65 years. We did so while also considering the confounding influence of gait speed, an aspect known to be reduced with old age. Ambulatory, community-dwelling older adult women (ages 65-91 years) with no current or recent lower-extremity injuries or surgeries underwent an instrumented gait analysis at a self-selected speed. Plantar flexor resistance was quantified via net ankle quasi-stiffness (NAS) defined as the slope of ankle joint moment-angle curve during late stance. showed that NAS was not significantly influenced by age (r = -0.11, p = 0.12), and that the confounding factor of walking speed had a significant, positive relationship with NAS (r = 0.59, p < 0.001). By determining that gait speed, not age, is related to NAS in older adults, this study represents the initial step towards objectively prescribing PD-AFO bending stiffness to achieve a targeted gait speed for older adults with plantar flexor weakness. Copyright © 2018 Elsevier B.V. All rights reserved.

Defining the mechanical properties of a spring-hinged ankle foot orthosis to assess its potential use in children with spastic cerebral palsy.

PubMed

Kerkum, Yvette L; Brehm, Merel-Anne; Buizer, Annemieke I; van den Noort, Josien C; Becher, Jules G; Harlaar, Jaap

2014-12-01

A rigid ventral shelf ankle foot orthosis (AFO) may improve gait in children with spastic cerebral palsy (SCP) whose gait is characterized by excessive knee flexion in stance. However, these AFOs can also impede ankle range of motion (ROM) and thereby inhibit push-off power. A more spring-like AFO can enhance push-off and may potentially reduce walking energy cost. The recent development of an adjustable spring-hinged AFO now allows adjustment of AFO stiffness, enabling tuning toward optimal gait performance. This study aims to quantify the mechanical properties of this spring-hinged AFO for each of its springs and settings. Using an AFO stiffness tester, two AFO hinges and their accompanying springs were measured. The springs showed a stiffness range of 0.01-1.82 N · m · deg(-1). The moment-threshold increased with increasing stiffness (1.13-12.1 N · m), while ROM decreased (4.91-16.5°). Energy was returned by all springs (11.5-116.3 J). These results suggest that the two stiffest available springs should improve joint kinematics and enhance push-off in children with SCP walking with excessive knee flexion.

Text Mining the Biomedical Literature

DTIC Science & Technology

2007-11-05

activities, and repeating past mistakes, or 3) agencies not participating in joint efforts that would fully exploit each agency’s strengths...research and joint projects (multi- department, multi-agency, multi-national, and government-industry) appropriate? • Is the balance among single...overall database taxonomy, i.e., are there any concepts missing from any of the databases, and even if not, do all the concepts bear the same

Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab.

PubMed

Chapple, W D

1997-09-01

Reflex activation of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, was studied using sinusoidal and stochastic longitudinal vibration of the muscle while recording the length and force of the muscle and the spike times of three exciter motoneurons. In the absence of vibration, the interspike interval histograms of the two larger motoneurons were bimodal; cutting sensory nerves containing most of the mechanoreceptor input removed the short interval peak in the histogram, indicating that the receptors are important in maintaining tonic firing. Vibration of the muscle evoked a reflex increase in motoneuron frequency that habituated after an initial peak but remained above control levels for the duration of stimulation. Motoneuron frequency increased with root mean square (rms) stimulus amplitude. Average stiffness during stimulation was about two times the stiffness of passive muscle. The reflex did not alter muscle dynamics. Estimated transfer functions were calculated from the fast Fourier transform of length and force signals. Coherence was >0.9 for the frequency range of 3-35 Hz. Stiffness magnitude gradually increased over this range in both reflex activated and passive muscle; phase was between 10 and 20 degrees. Reflex stiffness decreased with increasing stimulus amplitudes, but at larger amplitudes, this decrease was much less pronounced; in this range stiffness was regulated by the reflex. The sinusoidal frequency at which reflex bursts were elicited was approximately 6 Hz, consistent with previous measurements using ramp stretch. During reflex excitation, there was an increase in amplitude of the short interval peak in the interspike interval histogram; this was reduced when the majority of afferent pathways was removed. A phase histogram of motoneuron firing during sinusoidal vibration had a peak at approximately 110 ms, also suggesting that an important component of the reflex is via direct projections from the mechanoreceptors. These results are consistent with the hypothesis that a robust feedforward regulation of abdominal stiffness during continuous disturbances is achieved by mechanoreceptors signalling the absolute value of changing forces; habituation of the reflex, its high-threshold for low frequency disturbances and the activation kinetics of the muscle further modify reflex dynamics.

Mechanical stiffness of TMJ condylar cartilage increases after artificial aging by ribose.

PubMed

Mirahmadi, Fereshteh; Koolstra, Jan Harm; Lobbezoo, Frank; van Lenthe, G Harry; Ghazanfari, Samaneh; Snabel, Jessica; Stoop, Reinout; Everts, Vincent

2018-03-01

Aging is accompanied by a series of changes in mature tissues that influence their properties and functions. Collagen, as one of the main extracellular components of cartilage, becomes highly crosslinked during aging. In this study, the aim was to examine whether a correlation exists between collagen crosslinking induced by artificial aging and mechanical properties of the temporomandibular joint (TMJ) condyle. To evaluate this hypothesis, collagen crosslinks were induced using ribose incubation. Porcine TMJ condyles were incubated for 7 days with different concentrations of ribose. The compressive modulus and stiffness ratio (incubated versus control) was determined after loading. Glycosaminoglycan and collagen content, and the number of crosslinks were analyzed. Tissue structure was visualized by microscopy using different staining methods. Concomitant with an increasing concentration of ribose, an increase of collagen crosslinks was found. The number of crosslinks increased almost 50 fold after incubation with the highest concentration of ribose. Simultaneously, the stiffness ratio of the samples showed a significant increase after incubation with the ribose. Pearson correlation analyses showed a significant positive correlation between the overall stiffness ratio and the crosslink level; the higher the number of crosslinks the higher the stiffness. The present model, in which ribose was used to mimic certain aspects of age-related changes, can be employed as an in vitro model to study age-related mechanical changes in the TMJ condyle. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metatarsal Osteotomies: Complications.

PubMed

Reddy, Veerabhadra Babu

2018-03-01

Metatarsal osteotomies can be divided into proximal and distal. The proximal osteotomies, such as the oblique, segmental, set cut, and Barouk-Rippstein-Toullec (BRT) osteotomy, all provide the ability to significantly change the position of the metatarsal head without violating the joint. These osteotomies, however, have a high rate of nonunion when done without internal fixation and can lead to transfer metatarsalgia when done without regard to the parabola of metatarsal head position. Distal osteotomies such as the Weil and Helal offer superior healing but have an increased incidence of recurrent metatarsalgia, joint stiffness, and floating toe. Copyright © 2017 Elsevier Inc. All rights reserved.

Janus Kinase Inhibitors for the Treatment of Rheumatoid Arthritis.

PubMed

Turan, Senir; Walker, Scot

2017-11-01

Rheumatoid arthritis (RA) is a disease where the immune system attacks the linings of the joints, resulting in joint pain, stiffness, swelling, and destruction. Although many products are available for the treatment of RA, limitations such as adverse reactions and tolerance greatly affect adherence. Many of the current biologic disease-modifying antirheumatic drugs on the market are injectables, leaving a void to be filled for a product that can be taken orally. The most advanced of these approaches, the Janus kinase (JAK) inhibitors, are oral drugs that have not only made a breakthrough in RA, but also other skin conditions.

Improvements for the stability of heavy-haul couplers with arc surface contact

NASA Astrophysics Data System (ADS)

Wu, Guosong; Wang, Huang; Yao, Yuan

2018-03-01

To investigate the stability mechanism of heavy-haul couplers with arc surface contact, the geometry and force analysis were conducted according to the friction circle theory. To improve the stability of the coupler, four improvements were proposed, which are increasing the secondary lateral stiffness of locomotives, adding a restoring bumpstop at the end of the coupler, increasing the arc surfaces radii and changing the clearance and stiffness of secondary lateral stopping block. A multi-body dynamics model with four heavy-haul locomotives and three detailed couplers were established to simulate the emergency braking. In addition, the coupler yaw instability was tested to investigate the effects of relevant parameters on the coupler stability. The results show that increasing the secondary lateral stiffness of locomotives, adding a bumpstop with a smaller bumpstop gap, increasing the arc surfaces radii, increasing the stiffness and decreasing the clearance of secondary lateral stopping block are conducive to improving the stability of the coupler with arc surface contact.

Cell motility regulation on a stepped micro pillar array device (SMPAD) with a discrete stiffness gradient.

PubMed

Lee, Sujin; Hong, Juhee; Lee, Junghoon

2016-02-28

Our tissues consist of individual cells that respond to the elasticity of their environment, which varies between and within tissues. To better understand mechanically driven cell migration, it is necessary to manipulate the stiffness gradient across a substrate. Here, we have demonstrated a new variant of the microfabricated polymeric pillar array platform that can decouple the stiffness gradient from the ECM protein area. This goal is achieved via a "stepped" micro pillar array device (SMPAD) in which the contact area with the cell was kept constant while the diameter of the pillar bodies was altered to attain the proper mechanical stiffness. Using double-step SU-8 mold fabrication, the diameter of the top of every pillar was kept uniform, whereas that of the bottom was changed, to achieve the desired substrate rigidity. Fibronectin was immobilized on the pillar tops, providing a focal adhesion site for cells. C2C12, HeLa and NIH3T3 cells were cultured on the SMPAD, and the motion of the cells was observed by time-lapse microscopy. Using this simple platform, which produces a purely physical stimulus, we observed that various types of cell behavior are affected by the mechanical stimulus of the environment. We also demonstrated directed cell migration guided by a discrete rigidity gradient by varying stiffness. Interestingly, cell velocity was highest at the highest stiffness. Our approach enables the regulation of the mechanical properties of the polymeric pillar array device and eliminates the effects of the size of the contact area. This technique is a unique tool for studying cellular motion and behavior relative to various stiffness gradients in the environment.

3D Printed Multimaterial Microfluidic Valve.

PubMed

Keating, Steven J; Gariboldi, Maria Isabella; Patrick, William G; Sharma, Sunanda; Kong, David S; Oxman, Neri

2016-01-01

We present a novel 3D printed multimaterial microfluidic proportional valve. The microfluidic valve is a fundamental primitive that enables the development of programmable, automated devices for controlling fluids in a precise manner. We discuss valve characterization results, as well as exploratory design variations in channel width, membrane thickness, and membrane stiffness. Compared to previous single material 3D printed valves that are stiff, these printed valves constrain fluidic deformation spatially, through combinations of stiff and flexible materials, to enable intricate geometries in an actuated, functionally graded device. Research presented marks a shift towards 3D printing multi-property programmable fluidic devices in a single step, in which integrated multimaterial valves can be used to control complex fluidic reactions for a variety of applications, including DNA assembly and analysis, continuous sampling and sensing, and soft robotics.

Modeling Anisotropic Elastic Wave Propagation in Jointed Rock Masses

NASA Astrophysics Data System (ADS)

Hurley, R.; Vorobiev, O.; Ezzedine, S. M.; Antoun, T.

2016-12-01

We present a numerical approach for determining the anisotropic stiffness of materials with nonlinearly-compliant joints capable of sliding. The proposed method extends existing ones for upscaling the behavior of a medium with open cracks and inclusions to cases relevant to natural fractured and jointed rocks, where nonlinearly-compliant joints can undergo plastic slip. The method deviates from existing techniques by incorporating the friction and closure states of the joints, and recovers an anisotropic elastic form in the small-strain limit when joints are not sliding. We present the mathematical formulation of our method and use Representative Volume Element (RVE) simulations to evaluate its accuracy for joint sets with varying complexity. We then apply the formulation to determine anisotropic elastic constants of jointed granite found at the Nevada Nuclear Security Site (NNSS) where the Source Physics Experiments (SPE), a campaign of underground chemical explosions, are performed. Finally, we discuss the implementation of our numerical approach in a massively parallel Lagrangian code Geodyn-L and its use for studying wave propagation from underground explosions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Numerical Investigation of the Dynamic Properties of Intermittent Jointed Rock Models Subjected to Cyclic Uniaxial Compression

NASA Astrophysics Data System (ADS)

Liu, Yi; Dai, Feng; Zhao, Tao; Xu, Nu-wen

2017-01-01

Intermittent jointed rocks, which exist in a myriad of engineering projects, are extraordinarily susceptible to cyclic loadings. Understanding the dynamic fatigue properties of jointed rocks is necessary for evaluating the stability of rock engineering structures. This study numerically investigated the influences of cyclic loading conditions (i.e., frequency, maximum stress and amplitude) and joint geometric configurations (i.e., dip angle, persistency and interspace) on the dynamic fatigue mechanisms of jointed rock models. A reduction model of stiffness and strength was first proposed, and then, sixteen cyclic uniaxial loading tests with distinct loading parameters and joint geometries were simulated. Our results indicate that the reduction model can effectively reproduce the hysteresis loops and the accumulative plastic deformation of jointed rocks in the cyclic process. Both the loading parameters and the joint geometries significantly affect the dynamic properties, including the irreversible strain, damage evolution, dynamic residual strength and fatigue life. Three failure modes of jointed rocks, which are principally controlled by joint geometries, occur in the simulations: splitting failure through the entire rock sample, sliding failure along joint planes and mixed failure, which are principally controlled by joint geometries. Furthermore, the progressive failure processes of the jointed rock samples are numerically observed, and the different loading stages can be distinguished by the relationship between the number of broken bonds and the axial stress.

Multi-channel EEG-based sleep stage classification with joint collaborative representation and multiple kernel learning.

PubMed

Shi, Jun; Liu, Xiao; Li, Yan; Zhang, Qi; Li, Yingjie; Ying, Shihui

2015-10-30

Electroencephalography (EEG) based sleep staging is commonly used in clinical routine. Feature extraction and representation plays a crucial role in EEG-based automatic classification of sleep stages. Sparse representation (SR) is a state-of-the-art unsupervised feature learning method suitable for EEG feature representation. Collaborative representation (CR) is an effective data coding method used as a classifier. Here we use CR as a data representation method to learn features from the EEG signal. A joint collaboration model is established to develop a multi-view learning algorithm, and generate joint CR (JCR) codes to fuse and represent multi-channel EEG signals. A two-stage multi-view learning-based sleep staging framework is then constructed, in which JCR and joint sparse representation (JSR) algorithms first fuse and learning the feature representation from multi-channel EEG signals, respectively. Multi-view JCR and JSR features are then integrated and sleep stages recognized by a multiple kernel extreme learning machine (MK-ELM) algorithm with grid search. The proposed two-stage multi-view learning algorithm achieves superior performance for sleep staging. With a K-means clustering based dictionary, the mean classification accuracy, sensitivity and specificity are 81.10 ± 0.15%, 71.42 ± 0.66% and 94.57 ± 0.07%, respectively; while with the dictionary learned using the submodular optimization method, they are 80.29 ± 0.22%, 71.26 ± 0.78% and 94.38 ± 0.10%, respectively. The two-stage multi-view learning based sleep staging framework outperforms all other classification methods compared in this work, while JCR is superior to JSR. The proposed multi-view learning framework has the potential for sleep staging based on multi-channel or multi-modality polysomnography signals. Copyright © 2015 Elsevier B.V. All rights reserved.

Flexural Stiffness of Myosin Va Subdomains as Measured from Tethered Particle Motion

PubMed Central

Michalek, Arthur J.; Kennedy, Guy G.; Warshaw, David M.; Ali, M. Yusuf

2015-01-01

Myosin Va (MyoVa) is a processive molecular motor involved in intracellular cargo transport on the actin cytoskeleton. The motor's processivity and ability to navigate actin intersections are believed to be governed by the stiffness of various parts of the motor's structure. Specifically, changes in calcium may regulate motor processivity by altering the motor's lever arm stiffness and thus its interhead communication. In order to measure the flexural stiffness of MyoVa subdomains, we use tethered particle microscopy, which relates the Brownian motion of fluorescent quantum dots, which are attached to various single- and double-headed MyoVa constructs bound to actin in rigor, to the motor's flexural stiffness. Based on these measurements, the MyoVa lever arm and coiled-coil rod domain have comparable flexural stiffness (0.034 pN/nm). Upon addition of calcium, the lever arm stiffness is reduced 40% as a result of calmodulins potentially dissociating from the lever arm. In addition, the flexural stiffness of the full-length MyoVa construct is an order of magnitude less stiff than both a single lever arm and the coiled-coil rod. This suggests that the MyoVa lever arm-rod junction provides a flexible hinge that would allow the motor to maneuver cargo through the complex intracellular actin network. PMID:26770194

Use of an elastic transarticular external fixator construct for immobilization of the elbow joint.

PubMed

Vedrine, Bertrand

2017-04-01

Transarticular external skeletal fixation usually involves rigid bars that result in a stable but stiff joint. This study describes the technique and the outcome of an elastic transarticular external fixator (ETEF) applied to the elbow joint. Four cases of elbow luxation with collateral ligament injuries were managed with closed reduction and application of an ETEF to maintain the reduction. A triceps tendon avulsion was surgically managed before applying an ETEF. The clinical outcome was considered excellent in 2 cats, good in 2 dogs (1 elbow luxation and the avulsion of the triceps tendon), and poor in 1 dog presented for elbow luxation and a permanent neurological defect. The procedure was rapid, easy to perform, and inexpensive. All animals except the one with a neurological defect had an early return to weight bearing. This method maintains extension of the joint while permitting its motion thereby promoting rehabilitation.

Applied Joint-Space Torque and Stiffness Control of Tendon-Driven Fingers

NASA Technical Reports Server (NTRS)

Abdallah, Muhammad E.; Platt, Robert, Jr.; Wampler, Charles W.; Hargrave, Brian

2010-01-01

Existing tendon-driven fingers have applied force control through independent tension controllers on each tendon, i.e. in the tendon-space. The coupled kinematics of the tendons, however, cause such controllers to exhibit a transient coupling in their response. This problem can be resolved by alternatively framing the controllers in the joint-space of the manipulator. This work presents a joint-space torque control law that demonstrates both a decoupled and significantly faster response than an equivalent tendon-space formulation. The law also demonstrates greater speed and robustness than comparable PI controllers. In addition, a tension distribution algorithm is presented here to allocate forces from the joints to the tendons. It allocates the tensions so that they satisfy both an upper and lower bound, and it does so without requiring linear programming or open-ended iterations. The control law and tension distribution algorithm are implemented on the robotic hand of Robonaut-2.

Use of an elastic transarticular external fixator construct for immobilization of the elbow joint

PubMed Central

Vedrine, Bertrand

2017-01-01

Transarticular external skeletal fixation usually involves rigid bars that result in a stable but stiff joint. This study describes the technique and the outcome of an elastic transarticular external fixator (ETEF) applied to the elbow joint. Four cases of elbow luxation with collateral ligament injuries were managed with closed reduction and application of an ETEF to maintain the reduction. A triceps tendon avulsion was surgically managed before applying an ETEF. The clinical outcome was considered excellent in 2 cats, good in 2 dogs (1 elbow luxation and the avulsion of the triceps tendon), and poor in 1 dog presented for elbow luxation and a permanent neurological defect. The procedure was rapid, easy to perform, and inexpensive. All animals except the one with a neurological defect had an early return to weight bearing. This method maintains extension of the joint while permitting its motion thereby promoting rehabilitation. PMID:28373726

Nonlinear Modeling of Joint Dominated Structures

NASA Technical Reports Server (NTRS)

Chapman, J. M.

1990-01-01

The development and verification of an accurate structural model of the nonlinear joint-dominated NASA Langley Mini-Mast truss are described. The approach is to characterize the structural behavior of the Mini-Mast joints and struts using a test configuration that can directly measure the struts' overall stiffness and damping properties, incorporate this data into the structural model using the residual force technique, and then compare the predicted response with empirical data taken by NASA/LaRC during the modal survey tests of the Mini-Mast. A new testing technique, referred to as 'link' testing, was developed and used to test prototype struts of the Mini-Masts. Appreciable nonlinearities including the free-play and hysteresis were demonstrated. Since static and dynamic tests performed on the Mini-Mast also exhibited behavior consistent with joints having free-play and hysteresis, nonlinear models of the Mini-Mast were constructed and analyzed. The Residual Force Technique was used to analyze the nonlinear model of the Mini-Mast having joint free-play and hysteresis.

Multi-Objective Lake Superior Regulation

NASA Astrophysics Data System (ADS)

Asadzadeh, M.; Razavi, S.; Tolson, B.

2011-12-01

At the direction of the International Joint Commission (IJC) the International Upper Great Lakes Study (IUGLS) Board is investigating possible changes to the present method of regulating the outflows of Lake Superior (SUP) to better meet the contemporary needs of the stakeholders. In this study, a new plan in the form of a rule curve that is directly interpretable for regulation of SUP is proposed. The proposed rule curve has 18 parameters that should be optimized. The IUGLS Board is also interested in a regulation strategy that considers potential effects of climate uncertainty. Therefore, the quality of the rule curve is assessed simultaneously for multiple supply sequences that represent various future climate scenarios. The rule curve parameters are obtained by solving a computationally intensive bi-objective simulation-optimization problem that maximizes the total increase in navigation and hydropower benefits of the new regulation plan and minimizes the sum of all normalized constraint violations. The objective and constraint values are obtained from a Microsoft Excel based Shared Vision Model (SVM) that compares any new SUP regulation plan with the current regulation policy. The underlying optimization problem is solved by a recently developed, highly efficient multi-objective optimization algorithm called Pareto Archived Dynamically Dimensioned Search (PA-DDS). To further improve the computational efficiency of the simulation-optimization problem, the model pre-emption strategy is used in a novel way to avoid the complete evaluation of regulation plans with low quality in both objectives. Results show that the generated rule curve is robust and typically more reliable when facing unpredictable climate conditions compared to other SUP regulation plans.

Reliability formulation for the strength and fire endurance of glued-laminated beams

Treesearch

D. A. Bender

A model was developed for predicting the statistical distribution of glued-laminated beam strength and stiffness under normal temperature conditions using available long span modulus of elasticity data, end joint tension test data, and tensile strength data for laminating-grade lumber. The beam strength model predictions compared favorably with test data for glued-...

Design and fabrication of MEMS devices using the integration of MUMPs, trench-refilled molding, DRIE and bulk silicon etching processes

NASA Astrophysics Data System (ADS)

Wu, Mingching; Fang, Weileun

2005-03-01

This work integrates multi-depth DRIE etching, trench-refilled molding, two poly-Si layers MUMPs and bulk releasing to improve the variety and performance of MEMS devices. In summary, the present fabrication process, named MOSBE II, has three merits. First, this process can monolithically fabricate and integrate poly-Si thin-film structures with different thicknesses and stiffnesses, such as the flexible spring and the stiff mirror plate. Second, multi-depth structures, such as vertical comb electrodes, are available from the DRIE processes. Third, a cavity under the micromachined device is provided by the bulk silicon etching process, so that a large out-of-plane motion is allowed. In application, an optical scanner driven by the self-aligned vertical comb actuator was demonstrated. The poly-Si micromachined components fabricated by MOSBE II can further integrate with the MUMPs devices to establish a more powerful MOEMS platform.

Mechanical testing of internal fixation devices: A theoretical and practical examination of current methods.

PubMed

Grant, Caroline A; Schuetz, Michael; Epari, Devakar

2015-11-26

Successful healing of long bone fractures is dependent on the mechanical environment created within the fracture, which in turn is dependent on the fixation strategy. Recent literature reports have suggested that locked plating devices are too stiff to reliably promote healing. However, in vitro testing of these devices has been inconsistent in both method of constraint and reported outcomes, making comparisons between studies and the assessment of construct stiffness problematic. Each of the methods previously used in the literature were assessed for their effect on the bending of the sample and concordant stiffness. The choice of outcome measures used in in vitro fracture studies was also assessed. Mechanical testing was conducted on seven hole locked plated constructs in each method for comparison. Based on the assessment of each method the use of spherical bearings, ball joints or similar is suggested at both ends of the sample. The use of near and far cortex movement was found to be more comprehensive and more accurate than traditional centrally calculated interfragmentary movement values; stiffness was found to be highly susceptible to the accuracy of deformation measurements and constraint method, and should only be used as a within study comparison method. The reported stiffness values of locked plate constructs from in vitro mechanical testing is highly susceptible to testing constraints and output measures, with many standard techniques overestimating the stiffness of the construct. This raises the need for further investigation into the actual mechanical behaviour within the fracture gap of these devices. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rotational stiffness of American football shoes affects ankle biomechanics and injury severity.

PubMed

Button, Keith D; Braman, Jerrod E; Davison, Mark A; Wei, Feng; Schaeffer, Maureen C; Haut, Roger C

2015-06-01

While previous studies have investigated the effect of shoe-surface interaction on injury risk, few studies have examined the effect of rotational stiffness of the shoe. The hypothesis of the current study was that ankles externally rotated to failure in shoes with low rotational stiffness would allow more talus eversion than those in shoes with a higher rotational stiffness, resulting in less severe injury. Twelve (six pairs) cadaver lower extremities were externally rotated to gross failure while positioned in 20 deg of pre-eversion and 20 deg of predorsiflexion by fixing the distal end of the foot, axially loading the proximal tibia, and internally rotating the tibia. One ankle in each pair was constrained by an American football shoe with a stiff upper, while the other was constrained by an American football shoe with a flexible upper. Experimental bone motions were input into specimen-specific computational models to examine levels of ligament elongation to help understand mechanisms of ankle joint failure. Ankles in flexible shoes allowed 6.7±2.4 deg of talus eversion during rotation, significantly greater than the 1.7±1.0 deg for ankles in stiff shoes (p = 0.01). The significantly greater eversion in flexible shoes was potentially due to a more natural response of the ankle during rotation, possibly affecting the injuries that were produced. All ankles failed by either medial ankle injury or syndesmotic injury, or a combination of both. Complex (more than one ligament or bone) injuries were noted in 4 of 6 ankles in stiff shoes and 1 of 6 ankles in flexible shoes. Ligament elongations from the computational model validated the experimental injury data. The current study suggested flexibility (or rotational stiffness) of the shoe may play an important role in both the severity of ankle injuries for athletes.

An L-stable method for solving stiff hydrodynamics

NASA Astrophysics Data System (ADS)

Li, Shengtai

2017-07-01

We develop a new method for simulating the coupled dynamics of gas and multi-species dust grains. The dust grains are treated as pressure-less fluids and their coupling with gas is through stiff drag terms. If an explicit method is used, the numerical time step is subject to the stopping time of the dust particles, which can become extremely small for small grains. The previous semi-implicit method [1] uses second-order trapezoidal rule (TR) on the stiff drag terms and it works only for moderately small size of the dust particles. This is because TR method is only A-stable not L-stable. In this work, we use TR-BDF2 method [2] for the stiff terms in the coupled hydrodynamic equations. The L-stability of TR-BDF2 proves essential in treating a number of dust species. The combination of TR-BDF2 method with the explicit discretization of other hydro terms can solve a wide variety of stiff hydrodynamics equations accurately and efficiently. We have implemented our method in our LA-COMPASS (Los Alamos Computational Astrophysics Suite) package. We have applied the code to simulate some dusty proto-planetary disks and obtained very good match with astronomical observations.

Modeling and dynamic properties of dual-chamber solid and liquid mixture vibration isolator

NASA Astrophysics Data System (ADS)

Li, F. S.; Chen, Q.; Zhou, J. H.

2016-07-01

The dual-chamber solid and liquid mixture (SALiM) vibration isolator, mainly proposed for vibration isolation of heavy machines with low frequency, consists of four principle parts: SALiM working media including elastic elements and incompressible oil, multi-layers bellows container, rigid reservoir and the oil tube connecting the two vessels. The isolation system under study is governed by a two-degrees-of-freedom (2-DOF) nonlinear equation including quadratic damping. Simplifying the nonlinear damping into viscous damping, the equivalent stiffness and damping model is derived from the equation for the response amplitude. Theoretical analysis and numerical simulation reveal that the isolator's stiffness and damping have multiple properties with different parameters, among which the effects of exciting frequency, vibrating amplitude, quadratic damping coefficient and equivalent stiffness of the two chambers on the isolator's dynamics are discussed in depth. Based on the boundary characteristics of stiffness and damping and the main causes for stiffness hardening effect, improvement strategies are proposed to obtain better dynamic properties. At last, experiments were implemented and the test results were generally consistent with the theoretical ones, which verified the reliability of the nonlinear dynamic model.

Investigation of In Vivo skin stiffness anisotropy in breast cancer related lymphoedema.

PubMed

Coutts, L V; Miller, N R; Mortimer, P S; Bamber, J C

2016-01-04

There is a limited range of suitable measurement techniques for detecting and assessing breast cancer related lymphoedema (BCRL). This study investigated the suitability of using skin stiffness measurements, with a particular focus on the variation in stiffness with measurement direction (known as anisotropy). In addition to comparing affected tissue with the unaffected tissue on the corresponding site on the opposite limb, volunteers without BCRL were tested to establish the normal variability in stiffness anisotropy between these two corresponding regions of skin on each opposite limb. Multi-directional stiffness was measured with an Extensometer, within the higher stiffness region that skin typically displays at high applied strains, using a previously established protocol developed by the authors. Healthy volunteers showed no significant difference in anisotropy between regions of skin on opposite limbs (mean decrease of 4.7 +/-2.5% between non-dominant and dominant arms), whereas BCRL sufferers showed a significant difference between limbs (mean decrease of 51.0+/-16.3% between unaffected and affected arms). A large difference in anisotropy was apparent even for those with recent onset of the condition, indicating that the technique may have potential to be useful for early detection. This difference also appeared to increase with duration since onset. Therefore, measurement of stiffness anisotropy has potential value for the clinical assessment and diagnosis of skin conditions such as BCRL. The promising results justify a larger study with a larger number of participants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Multi-joint postural behavior in patients with knee osteoarthritis.

PubMed

Turcot, Katia; Sagawa, Yoshimasa; Hoffmeyer, Pierre; Suvà, Domizio; Armand, Stéphane

2015-12-01

Previous studies have demonstrated balance impairment in patients with knee osteoarthritis (OA). Although it is currently accepted that postural control depends on multi-joint coordination, no study has previously considered this postural strategy in patients suffering from knee OA. The objectives of this study were to investigate the multi-joint postural behavior in patients with knee OA and to evaluate the association with clinical outcomes. Eighty-seven patients with knee OA and twenty-five healthy elderly were recruited to the study. A motion analysis system and two force plates were used to investigate the joint kinematics (trunk and lower body segments), the lower body joint moments, the vertical ground reaction force ratio and the center of pressure (COP) during a quiet standing task. Pain, functional capacity and quality of life status were also recorded. Patients with symptomatic and severe knee OA adopt a more flexed posture at all joint levels in comparison with the control group. A significant difference in the mean ratio was found between groups, showing an asymmetric weight distribution in patients with knee OA. A significant decrease in the COP range in the anterior-posterior direction was also observed in the group of patients. Only small associations were observed between postural impairments and clinical outcomes. This study brings new insights regarding the postural behavior of patients with severe knee OA during a quiet standing task. The results confirm the multi-joint asymmetric posture adopted by this population. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural characterization of a first-generation articulated-truss joint for space crane application

NASA Technical Reports Server (NTRS)

Sutter, Thomas R.; Wu, K. Chauncey; Riutort, Kevin T.; Laufer, Joseph B.; Phelps, James E.

1992-01-01

A first-generation space crane articulated-truss joint was statically and dynamically characterized in a configuration that approximated an operational environment. The articulated-truss joint was integrated into a test-bed for structural characterization. Static characterization was performed by applying known loads and measuring the corresponding deflections to obtain load-deflection curves. Dynamic characterization was performed using modal testing to experimentally determine the first six mode shapes, frequencies, and modal damping values. Static and dynamic characteristics were also determined for a reference truss that served as a characterization baseline. Load-deflection curves and experimental frequency response functions are presented for the reference truss and the articulated-truss joint mounted in the test-bed. The static and dynamic experimental results are compared with analytical predictions obtained from finite element analyses. Load-deflection response is also presented for one of the linear actuators used in the articulated-truss joint. Finally, an assessment is presented for the predictability of the truss hardware used in the reference truss and articulated-truss joint based upon hardware stiffness properties that were previously obtained during the Precision Segmented Reflector (PSR) Technology Development Program.

Stiffness and strength of fiber reinforced polymer composite bridge deck systems

NASA Astrophysics Data System (ADS)

Zhou, Aixi

This research investigates two principal characteristics that are of primary importance in Fiber Reinforced Polymer (FRP) bridge deck applications: STIFFNESS and STRENGTH. The research was undertaken by investigating the stiffness and strength characteristics of the multi-cellular FRP bridge deck systems consisting of pultruded FRP shapes. A systematic analysis procedure was developed for the stiffness analysis of multi-cellular FRP deck systems. This procedure uses the Method of Elastic Equivalence to model the cellular deck as an equivalent orthotropic plate. The procedure provides a practical method to predict the equivalent orthotropic plate properties of cellular FRP decks. Analytical solutions for the bending analysis of single span decks were developed using classical laminated plate theory. The analysis procedures can be extended to analyze continuous FRP decks. It can also be further developed using higher order plate theories. Several failure modes of the cellular FRP deck systems were recorded and analyzed through laboratory and field tests and Finite Element Analysis (FEA). Two schemes of loading patches were used in the laboratory test: a steel patch made according to the ASSHTO's bridge testing specifications; and a tire patch made from a real truck tire reinforced with silicon rubber. The tire patch was specially designed to simulate service loading conditions by modifying real contact loading from a tire. Our research shows that the effects of the stiffness and contact conditions of loading patches are significant in the stiffness and strength testing of FRP decks. Due to the localization of load, a simulated tire patch yields larger deflection than the steel patch under the same loading level. The tire patch produces significantly different failure compared to the steel patch: a local bending mode with less damage for the tire patch; and a local punching-shear mode for the steel patch. A deck failure function method is proposed for predicting the failure of FRP decks. Using developed laminated composite theories and FEA techniques, a strength analysis procedure containing ply-level information was proposed and detailed for FRP deck systems. The behavior of the deck's unsupported (free) edges was also investigated using ply-level FEA.

Dietary variation and mechanical properties of articular cartilage in the temporomandibular joint: implications for the role of plasticity in mechanobiology and pathobiology.

PubMed

Ravosa, Matthew J; Kane, Robert J

2017-10-01

Due to their nature as tissue composites, skeletal joints pose an additional challenge in terms of evaluating the functional significance of morphological variation in their bony and cartilaginous components in response to altered loading conditions. Arguably, this complexity requires more direct means of investigating joint plasticity and performance than typically employed to analyze macro- and micro-anatomical phenomena. To address a significant gap in our understanding of the plasticity of the mammalian temporomandibular joint (TMJ), we investigated the histology and mechanical properties of condylar articular cartilage in rabbits subjected to long-term variation in diet-induced masticatory stresses, specifically cyclical loading. Three cohorts of male weanlings were raised for six months on different diets until adulthood. Following euthanasia, the TMJ condyles on one side were dissected away, fixed, decalcified, dehydrated, embedded and sectioned. Safranin O staining was employed to identify variation in proteoglycan content, which in turn was used to predict patterns of articular cartilage stiffness in contralateral condylar specimens for each treatment group. Hematoxylin and eosin staining was used to quantify diet-induced changes in chondrocyte hypertrophy and cellularity. Mechanical tests document significant decreases in articular cartilage stiffness corresponding to patterns of extracellular matrix relative protein abundance in rabbits subjected to greater cyclical loading. This indicates that TMJs routinely subjected to higher masticatory stresses due to a challenging diet eventually develop postnatal decreases in the ability to counter compressive loads during postcanine biting and chewing. These findings provide novel information regarding TMJ performance, with broader implications about the costs and benefits of phenotypic plasticity as well as implications for how such biological processes affect connective tissue mechanobiology and pathobiology. Copyright © 2017 Elsevier GmbH. All rights reserved.

Relationship between activation of ankle muscles and quasi-joint stiffness in early and middle stances during gait in patients with hemiparesis.

PubMed

Sekiguchi, Yusuke; Muraki, Takayuki; Tanaka, Naofumi; Izumi, Shin-Ichi

2015-09-01

It is unclear whether muscle contraction is necessary to increase quasi-joint stiffness (QJS) of the ankle joint during gait in patients with hemiparesis. The purpose of the present study was to investigate the relationship between QJS and muscle activation at the ankle joint in the stance phase during gait in patients with hemiparesis. Spatiotemporal and kinetic gait parameters and activation of the medial head of the gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) muscles were measured using a 3-dimensional motion analysis system and surface electromyography, in 21 patients with hemiparesis due to stroke and 10 healthy individuals. In the early stance, the QJS on the paretic side (PS) of patients was greater than that on the non-PS (p<0.05) and not significantly correlated with activation of the three muscles. In the middle stance, the QJS on the PS was lower than that on the non-PS (p<0.05) and that on the right side of controls (p<0.001), which was positively correlated with activation of the MG (r=0.51, p<0.05) and SOL (r=0.49, p<0.05). In the patients with hemiparesis, plantarflexor activation may not contribute to QJS in the early stance. On the other hand, QJS in the middle stance may be attributed to activation of the MG and SOL. Our findings suggest that activation of the MG and SOL in the middle stance on the PS may require to be enhanced to increase QJS during gait in patients with hemiparesis. Copyright © 2015 Elsevier B.V. All rights reserved.

Air Land Sea Bulletin

DTIC Science & Technology

2014-11-01

conducting multi-Service and joint force operations. Status: Current TACTICAL RADIOS Multi-Service Communications Procedures for Tactical Radios in a Joint...Techniques, and Proce- dures Package for Ultra High Frequency Military Satellite Communications Distribution Restricted 9 AUG 13 ATP 6-02.90 MCRP 3... Communicating within the Information Environment......................................................................30 IN HOUSE Current ALSA MTTP

Nuclear Lamin-A Scales with Tissue Stiffness and Enhances Matrix-Directed Differentiation

PubMed Central

Swift, Joe; Ivanovska, Irena L.; Buxboim, Amnon; Harada, Takamasa; Dingal, P. C. Dave P.; Pinter, Joel; Pajerowski, J. David; Spinler, Kyle R.; Shin, Jae-Won; Tewari, Manorama; Rehfeldt, Florian; Speicher, David W.; Discher, Dennis E.

2014-01-01

Tissues can be soft like fat, which bears little stress, or stiff like bone, which sustains high stress, but whether there is a systematic relationship between tissue mechanics and differentiation is unknown. Here, proteomics analyses revealed that levels of the nucleoskeletal protein lamin-A scaled with tissue elasticity, E, as did levels of collagens in the extracellular matrix that determine E. Stem cell differentiation into fat on soft matrix was enhanced by low lamin-A levels, whereas differentiation into bone on stiff matrix was enhanced by high lamin-A levels. Matrix stiffness directly influenced lamin-A protein levels, and, although lamin-A transcription was regulated by the vitamin A/retinoic acid (RA) pathway with broad roles in development, nuclear entry of RA receptors was modulated by lamin-A protein. Tissue stiffness and stress thus increase lamin-A levels, which stabilize the nucleus while also contributing to lineage determination. PMID:23990565

A preliminary case series evaluating the safety and immediate to short-term clinical benefits of joint mobilization in hemophilic arthritis of the lower limb.

PubMed

Scaddan, Emma; Rowell, John; O'Leary, Shaun

2017-09-01

Arthritis resulting from recurrent intra-articular bleeding in individuals with hemophilia can be severely debilitating due to joint pain and stiffness with subsequent loss of mobility and function. Very limited studies have investigated the potential benefits of joint mobilization for this condition. This case series is a preliminary investigation of safety, as well as immediate and short-term clinical benefits, associated with gentle knee and ankle joint mobilization in people with hemophilic arthropathy. A single intervention of joint mobilization was applied to the affected knees and/or ankles of 16 individuals with severe or moderate hemophilia within a public hospital setting. Adverse events, as well as immediate (pain-free passive joint range, Timed Up and Go Test with maximum pain numerical rating scale) and short-term (Lower Extremity Functional Scale) effects of the intervention were evaluated with a repeated measures ANOVA. There were no adverse events. An immediate significant increase was observed in pain-free passive ankle joint range of motion ( p  < 0.05) following the joint mobilization intervention. The findings of this case series suggest that gentle joint mobilization techniques may be safely considered as part of a multimodal management approach for hemophilic arthropathy.

[Clinical randomized study of bee-sting therapy for rheumatoid arthritis].

PubMed

Liu, Xi-De; Zhang, Jin-Lu; Zheng, Han-Guang; Liu, Feng-Yun; Chen, Ying

2008-06-01

To observe the clinical effect of bee-sting (venom) therapy in the treatment of rheumatoid arthritis (RA). One hundred RA patients were randomly divided into medication (control) group and bee-venom group, with 50 cases in each. Patients of control group were treated with oral administration of Methotrexate (MTX, 7.5 mg/w), Sulfasalazine (0.5 g,t. i.d.), Meloxicam (Mobic,7. 5 mg, b. i. d.); and those of bee-venom group treated with Bee-sting of Ashi-points and the above-mentioned Western medicines. Ashi-points were selected according to the position of RA and used as the main acupoints, supplemented with other acupoints according to syndrome differentiation. The treatment was given once every other day and all the treatments lasted for 3 months. Compared with pre-treatment, scores of joint swelling degree, joint activity, pain, and pressing pain, joint-swelling number, grasp force, 15 m-walking duration, morning stiff duration in bee-venom group and medication group were improved significantly (P<0.05, 0.01). Comparison between two groups showed that after the therapy, scores of joint swelling, pain and pressing pain, joint-swelling number and morning stiff duration, and the doses of the administered MTX and Mobic in bee-venom group were all significantly lower than those in medication group (P<0.05, 0.01); whereas the grasp force in been-venom group was markedly higher than that in medication group (P<0.05). In addition, the relapse rate of bee-venom group was obviously lower than that of medication group (P<0.05; 12% vs 32%). Combined application of bee-venom therapy and medication is superior to simple use of medication in relieving RA, and when bee-sting therapy used, the commonly-taken doses of western medicines may be reduced, and the relapse rate gets lower.

[Correlations Between Joint Proprioception, Muscle Strength, and Functional Ability in Patients with Knee Osteoarthritis].

PubMed

Chen, Yoa; Yu, Yong; He, Cheng-qi

2015-11-01

To establish correlations between joint proprioception, muscle flexion and extension peak torque, and functional ability in patients with knee osteoarthritis (OA). Fifty-six patients with symptomatic knee OA were recruited in this study. Both proprioceptive acuity and muscle strength were measured using the isomed-2000 isokinetic dynamometer. Proprioceptive acuity was evaluated by establishing the joint motion detection threshold (JMDT). Muscle strength was evaluated by Max torque (Nm) and Max torque/weight (Nm/ kg). Functional ability was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index physical function (WOMAC-PF) questionnaire. Correlational analyses were performed between proprioception, muscle strength, and functional ability. A multiple stepwise regression model was established, with WOMAC-PF as dependent variable and patient age, body mass index (BMI), visual analogue scale (VAS)-score, mean grade for Kellgren-Lawrance of both knees, mean strength for quadriceps and hamstring muscles of both knees, and mean JMDT of both knees as independent variables. Poor proprioception (high JMDT) was negatively correlated with muscle strength (P<0.05). There was no significant correlation between knee proprioception (high JMDT) and joint pain (WOMAC pain score), and between knee proprioception (high JMDT) and joint stiffness (WOMAC stiffness score). Poor proprioception (high JMDT) was correlated with limitation in functional ability (WOMAC physical function score r=0.659, P<0.05). WOMAC score was correlated with poor muscle strength (quadriceps muscle strength r = -0.511, P<0.05, hamstring muscle strength r = -0.408, P<0.05). The multiple stepwise regression model showed that high JMDT C standard partial regression coefficient (B) = 0.385, P<0.50 and high VAS-scale score (B=0.347, P<0.05) were significant predictors of WOMAC-PF score. Patients with poor proprioception is associated with poor muscle strength and limitation in functional ability. Patients with symptomatic OA of knees commonly endure with moderate to considerable dysfunction, which is associated with poor proprioception (high JMDT) and high VAS-scale score.

Functional Capacity in Adults With Cerebral Palsy: Lower Limb Muscle Strength Matters.

PubMed

Gillett, Jarred G; Lichtwark, Glen A; Boyd, Roslyn N; Barber, Lee A

2018-05-01

To investigate the relation between lower limb muscle strength, passive muscle properties, and functional capacity outcomes in adults with cerebral palsy (CP). Cross-sectional study. Tertiary institution biomechanics laboratory. Adults with spastic-type CP (N=33; mean age, 25y; range, 15-51y; mean body mass, 70.15±21.35kg) who were either Gross Motor Function Classification System (GMFCS) level I (n=20) or level II (n=13). Not applicable. Six-minute walk test (6MWT) distance (m), lateral step-up (LSU) test performance (total repetitions), timed up-stairs (TUS) performance (s), maximum voluntary isometric strength of plantar flexors (PF) and dorsiflexors (DF) (Nm.kg -1 ), and passive ankle joint and muscle stiffness. Maximum isometric PF strength independently explained 61% of variance in 6MWT performance, 57% of variance in LSU test performance, and 50% of variance in TUS test performance. GMFCS level was significantly and independently related to all 3 functional capacity outcomes, and age was retained as a significant independent predictor of LSU and TUS test performance. Passive medial gastrocnemius muscle fascicle stiffness and ankle joint stiffness were not significantly related to functional capacity measures in any of the multiple regression models. Low isometric PF strength was the most important independent variable related to distance walked on the 6MWT, fewer repetitions on the LSU test, and slower TUS test performance. These findings suggest lower isometric muscle strength contributes to the decline in functional capacity in adults with CP. Copyright © 2018 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Olympic weightlifting training causes different knee muscle-coactivation adaptations compared with traditional weight training.

PubMed

Arabatzi, Fotini; Kellis, Eleftherios

2012-08-01

The purpose of this study was to compare the effects of an Olympic weightlifting (OL) and traditional weight (TW) training program on muscle coactivation around the knee joint during vertical jump tests. Twenty-six men were assigned randomly to 3 groups: the OL (n = 9), the TW (n = 9), and Control (C) groups (n = 8). The experimental groups trained 3 d · wk(-1) for 8 weeks. Electromyographic (EMG) activity from the rectus femoris and biceps femoris, sagittal kinematics, vertical stiffness, maximum height, and power were collected during the squat jump, countermovement jump (CMJ), and drop jump (DJ), before and after training. Knee muscle coactivation index (CI) was calculated for different phases of each jump by dividing the antagonist EMG activity by the agonist. Analysis of variance showed that the CI recorded during the preactivation and eccentric phases of all the jumps increased in both training groups. The OL group showed a higher stiffness and jump height adaptation than the TW group did (p < 0.05). Further, the OL showed a decrease or maintenance of the CI recorded during the propulsion phase of the CMJ and DJs, which is in contrast to the increase in the CI observed after TW training (p < 0.05). The results indicated that the altered muscle activation patterns about the knee, coupled with changes of leg stiffness, differ between the 2 programs. The OL program improves jump performance via a constant CI, whereas the TW training caused an increased CI, probably to enhance joint stability.

Correlation between Mechanical Properties of the Ankle Muscles and Postural Sway during the Menstrual Cycle.

PubMed

Yim, JongEun; Petrofsky, Jerrold; Lee, Haneul

2018-03-01

Ankle and foot injuries are common among athletes and physically active individuals. The most common residual disability, ankle sprain, is characterized by instability along with postural sway. If the supporting structures around a joint become lax, posture stability and balance are also affected. Previous studies have examined muscle stiffness and elasticity and postural sway separately; however, the relationship between these factors is yet unknown. It is well known that the levels of sex hormones, especially estrogen, change in women over the phase of the menstrual cycle. Therefore, this study examined the relationship between the mechanical properties of tissue and balance activity using a non-invasive digital palpation device to determine if they undergo any changes over the menstrual cycle in young women. Sixteen young women with regular menstrual cycles completed the study. Tone, stiffness, and elasticity of the ankle muscles (lateral gastrocnemius, peroneus longus, and tibialis anterior) were measured using a non-invasive digital palpation device. Postural sway was recorded while the participants performed balance tasks during ovulation and menstruation. Significantly greater posture sway characteristics and ankle muscle elasticity were found during ovulation than during menstruation; lower tone and stiffness of the ankle muscles were observed at ovulation (p < 0.05). Additionally, weak-to-strong relationships between ankle muscle mechanical properties and postural sway characteristics were found (p < 0.05). These results suggest the effect of estrogen on human connective tissues. We therefore postulate that estrogen increases joint and muscle laxity and affects posture stability according to the phase of the menstrual cycle.

Movement coordination patterns between the foot joints during walking.

PubMed

Arnold, John B; Caravaggi, Paolo; Fraysse, François; Thewlis, Dominic; Leardini, Alberto

2017-01-01

In 3D gait analysis, kinematics of the foot joints are usually reported via isolated time histories of joint rotations and no information is provided on the relationship between rotations at different joints. The aim of this study was to identify movement coordination patterns in the foot during walking by expanding an existing vector coding technique according to an established multi-segment foot and ankle model. A graphical representation is also described to summarise the coordination patterns of joint rotations across multiple patients. Three-dimensional multi-segment foot kinematics were recorded in 13 adults during walking. A modified vector coding technique was used to identify coordination patterns between foot joints involving calcaneus, midfoot, metatarsus and hallux segments. According to the type and direction of joints rotations, these were classified as in-phase (same direction), anti-phase (opposite directions), proximal or distal joint dominant. In early stance, 51 to 75% of walking trials showed proximal-phase coordination between foot joints comprising the calcaneus, midfoot and metatarsus. In-phase coordination was more prominent in late stance, reflecting synergy in the simultaneous inversion occurring at multiple foot joints. Conversely, a distal-phase coordination pattern was identified for sagittal plane motion of the ankle relative to the midtarsal joint, highlighting the critical role of arch shortening to locomotor function in push-off. This study has identified coordination patterns between movement of the calcaneus, midfoot, metatarsus and hallux by expanding an existing vector cording technique for assessing and classifying coordination patterns of foot joints rotations during walking. This approach provides a different perspective in the analysis of multi-segment foot kinematics, and may be used for the objective quantification of the alterations in foot joint coordination patterns due to lower limb pathologies or following injuries.

Self-aligning exoskeleton hip joint: Kinematic design with five revolute, three prismatic and one ball joint.

PubMed

Beil, Jonas; Marquardt, Charlotte; Asfour, Tamim

2017-07-01

Kinematic compatibility is of paramount importance in wearable robotic and exoskeleton design. Misalignments between exoskeletons and anatomical joints of the human body result in interaction forces which make wearing the exoskeleton uncomfortable and even dangerous for the human. In this paper we present a kinematically compatible design of an exoskeleton hip to reduce kinematic incompatibilities, so called macro- and micro-misalignments, between the human's and exoskeleton's joint axes, which are caused by inter-subject variability and articulation. The resulting design consists of five revolute, three prismatic and one ball joint. Design parameters such as range of motion and joint velocities are calculated based on the analysis of human motion data acquired by motion capture systems. We show that the resulting design is capable of self-aligning to the human hip joint in all three anatomical planes during operation and can be adapted along the dorsoventral and mediolateral axis prior to operation. Calculation of the forward kinematics and FEM-simulation considering kinematic and musculoskeletal constraints proved sufficient mobility and stiffness of the system regarding the range of motion, angular velocity and torque admissibility needed to provide 50 % assistance for an 80 kg person.

3D Printed Multimaterial Microfluidic Valve

PubMed Central

Patrick, William G.; Sharma, Sunanda; Kong, David S.; Oxman, Neri

2016-01-01

We present a novel 3D printed multimaterial microfluidic proportional valve. The microfluidic valve is a fundamental primitive that enables the development of programmable, automated devices for controlling fluids in a precise manner. We discuss valve characterization results, as well as exploratory design variations in channel width, membrane thickness, and membrane stiffness. Compared to previous single material 3D printed valves that are stiff, these printed valves constrain fluidic deformation spatially, through combinations of stiff and flexible materials, to enable intricate geometries in an actuated, functionally graded device. Research presented marks a shift towards 3D printing multi-property programmable fluidic devices in a single step, in which integrated multimaterial valves can be used to control complex fluidic reactions for a variety of applications, including DNA assembly and analysis, continuous sampling and sensing, and soft robotics. PMID:27525809

Vibration Control Using a State Observer that Considers Disturbances of a Golf Swing Robot

NASA Astrophysics Data System (ADS)

Hoshino, Yohei; Kobayashi, Yukinori; Yamada, Gen

In this paper, optimal control of a golf swing robot that is used to evaluate the performance of golf clubs is described. The robot has two joints, a rigid link and a flexible link that is a golf club. A mathematical model of the golf club is derived by Hamilton’s principle in consideration of bending and torsional stiffness and in consideration of eccentricity of the center of gravity of the club head on the shaft axis. A linear quadratic regulator (LQR) that considers the vibration of the club shaft is used to stop the robot during the follow-through. Since the robot moves fast and has strong non-linearity, an ordinary state observer for a linear system cannot accurately estimate the states of the system. A state observer that considers disturbances accurately estimates the state variables that cannot be measured. The results of numerical simulation are compared with experimental results obtained by using a swing robot.