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Sample records for bipedal walking mechanism

  1. The Basic Mechanics of Bipedal Walking Lead to Asymmetric Behavior

    PubMed Central

    Gregg, Robert D.; Degani, Amir; Dhaher, Yasin; Lynch, Kevin M.

    2014-01-01

    This paper computationally investigates whether gait asymmetries can be attributed in part to basic bipedal mechanics independent of motor control. Using a symmetrical rigid-body model known as the compass-gait biped, we show that changes in environmental or physiological parameters can facilitate asymmetry in gait kinetics at fast walking speeds. In the environmental case, the asymmetric family of high-speed gaits is in fact more stable than the symmetric family of low-speed gaits. These simulations suggest that lower extremity mechanics might play a direct role in functional and pathological asymmetries reported in human walking, where velocity may be a common variable in the emergence and growth of asymmetry. PMID:22275657

  2. On the Mechanics of Functional Asymmetry in Bipedal Walking

    PubMed Central

    Dhaher, Yasin Y.; Degani, Amir; Lynch, Kevin M.

    2014-01-01

    This paper uses two symmetrical models, the passive compass-gait biped and a five-link 3D biped, to computationally investigate the cause and function of gait asymmetry. We show that for a range of slope angles during passive 2D walking and mass distributions during controlled 3D walking, these models have asymmetric walking patterns between the left and right legs due to the phenomenon of spontaneous symmetry-breaking. In both cases a stable asymmetric family of gaits emerges from a symmetric family of gaits as the total energy increases (e.g., fast speeds). The ground reaction forces of each leg reflect different roles, roughly corresponding to support, propulsion, and motion control as proposed by the hypothesis of functional asymmetry in able-bodied human walking. These results suggest that body mechanics, independent of neurophysiological mechanisms such as leg dominance, may contribute to able-bodied gait asymmetry. PMID:22328168

  3. Design of a bipedal walking robot

    NASA Astrophysics Data System (ADS)

    Pratt, Jerry; Krupp, Ben

    2008-04-01

    We present the mechanical design of a bipedal walking robot named M2V2, as well as control strategies to be implemented for walking and balance recovery. M2V2 has 12 actuated degrees of freedom in the lower body: three at each hip, one at each knee, and two at each ankle. Each degree of freedom is powered by a force controllable Series Elastic Actuator. These actuators provide high force fidelity and low impedance, allowing for control techniques that exploit the natural dynamics of the robot. The walking and balance recovery controllers will use the concepts of Capture Points and the Capture Region in order to decide where to step. A Capture Point is a point on the ground in which a biped can step to in order to stop, and the Capture Region is the locus of such points.

  4. Theories of bipedal walking: an odyssey.

    PubMed

    Vaughan, Christopher L

    2003-04-01

    In this paper six theories of bipedal walking, and the evidence in support of the theories, are reviewed. They include: evolution, minimising energy consumption, maturation in children, central pattern generators, linking control and effect, and robots on two legs. Specifically, the six theories posit that: (1) bipedalism is the fundamental evolutionary adaptation that sets hominids--and therefore humans--apart from other primates; (2) locomotion is the translation of the centre of gravity along a pathway requiring the least expenditure of energy; (3) when a young child takes its first few halting steps, his or her biomechanical strategy is to minimise the risk of falling; (4) a dedicated network of interneurons in the spinal cord generates the rhythm and cyclic pattern of electromyographic signals that give rise to bipedal gait; (5) bipedal locomotion is generated through global entrainment of the neural system on the one hand, and the musculoskeletal system plus environment on the other; and (6) powered dynamic gait in a bipedal robot can be realised only through a strategy which is based on stability and real-time feedback control. The published record suggests that each of the theories has some measure of support. However, it is important to note that there are other important theories of locomotion which have not been covered in this review. Despite such omissions, this odyssey has explored the wide spectrum of bipedal walking, from its origins through to the integration of the nervous, muscular and skeletal systems.

  5. The mechanical effectiveness of erect and "bent-hip, bent-knee" bipedal walking in Australopithecus afarensis.

    PubMed

    Crompton, R H; Yu, L; Weijie, W; Günther, M; Savage, R

    1998-07-01

    It is universally accepted that the postcranial skeleton of the early hominid Australopithecus afarensis shows adaptations, or at least exaptations, towards bipedalism. However, there continues to be a debate concerning the likely form of terrestrial bipedality: whether gait was erect, like our own, or "bent-hip, bent-knee" like the bipedalism of living chimpanzees. In this study we use predictive dynamic modelling to assess the mechanical effectiveness of AL-288-1 under both hypotheses, on the basis of data on segment proportions from the literature. AL-288-1's proportions are incompatible with the kinematics of chimpanzee bipedalism, but compatible with the kinematics of either erect or "bent-hip, bent-knee" human gait. In the latter case, neither the ankle nor the knee joint would have contributed substantial mechanical work to propulsion of the body, and net energy absorption is predicted for these joints, which would have resulted in increased heat load. Such an ineffective gait is unlikely to have lead to selection for "bipedal" features in the postcranial skeleton.

  6. Development of bipedal walking in humans and chimpanzees: a comparative study.

    PubMed

    Kimura, Tasuku; Yaguramaki, Naoko

    2009-01-01

    Development of bipedal walking from the very early stage of walking was studied longitudinally in infant humans and chimpanzees. In contrast to adults, infants of neither species could walk steadily and rhythmically step by step. Short braking duration and small recovery of mechanical energy were demonstrated in infants of both species. The trunk was inclined forwards, the extension of lower limb joints was limited and the accelerating force was not strongly activated. Potential energy was not efficiently used in progression. Walking in adult chimpanzees still showed a forward-inclined trunk, short braking duration, small recovery of energy and large variance of parameters compared to the unique human adult bipedalism. The locomotor characteristics of presumed pre-bipedal ancestors are discussed.

  7. Origin of human bipedalism: The knuckle-walking hypothesis revisited.

    PubMed

    Richmond, B G; Begun, D R; Strait, D S

    2001-01-01

    Some of the most long-standing questions in paleoanthropology concern how and why human bipedalism evolved. Over the last century, many hypotheses have been offered on the mode of locomotion from which bipedalism originated. Candidate ancestral adaptations include monkey-like arboreal or terrestrial quadrupedalism, gibbon- or orangutan-like (or other forms of) climbing and suspension, and knuckle-walking. This paper reviews the history of these hypotheses, outlines their predictions, and assesses them in light of current phylogenetic, comparative anatomical, and fossil evidence. The functional significance of characteristics of the shoulder and arm, elbow, wrist, and hand shared by African apes and humans, including their fossil relatives, most strongly supports the knuckle-walking hypothesis, which reconstructs the ancestor as being adapted to knuckle-walking and arboreal climbing. Future fossil discoveries, and a clear understanding of anthropoid locomotor anatomy, are required to ultimately test these hypotheses. If knuckle-walking was an important component of the behavioral repertoire of the prebipedal human ancestor, then we can reject scenarios on the origin of bipedalism that rely on a strictly arboreal ancestor. Moreover, paleoenvironmental data associated with the earliest hominins, and their close relatives, contradict hypotheses that place the agents of selection for bipedality in open savanna habitats. Existing hypotheses must explain why bipedalism would evolve from an ancestor that was already partly terrestrial. Many food acquisition and carrying hypotheses remain tenable in light of current evidence.

  8. Theoretical analysis of the state of balance in bipedal walking.

    PubMed

    Firmani, Flavio; Park, Edward J

    2013-04-01

    This paper presents a theoretical analysis based on classic mechanical principles of balance of forces in bipedal walking. Theories on the state of balance have been proposed in the area of humanoid robotics and although the laws of classical mechanics are equivalent to both humans and humanoid robots, the resulting motion obtained with these theories is unnatural when compared to normal human gait. Humanoid robots are commonly controlled using the zero moment point (ZMP) with the condition that the ZMP cannot exit the foot-support area. This condition is derived from a physical model in which the biped must always walk under dynamically balanced conditions, making the centre of pressure (CoP) and the ZMP always coincident. On the contrary, humans follow a different strategy characterized by a 'controlled fall' at the end of the swing phase. In this paper, we present a thorough theoretical analysis of the state of balance and show that the ZMP can exit the support area, and its location is representative of the imbalance state characterized by the separation between the ZMP and the CoP. Since humans exhibit this behavior, we also present proof-of-concept results of a single subject walking on an instrumented treadmill at different speeds (from slow 0.7 m/s to fast 2.0 m/s walking with increments of 0.1 m/s) with the motion recorded using an optical motion tracking system. In order to evaluate the experimental results of this model, the coefficient of determination (R2) is used to correlate the measured ground reaction forces and the resultant of inertial and gravitational forces (anteroposterior R² = 0.93, mediolateral R² = 0.89, and vertical R² = 0.86) indicating that there is a high correlation between the measurements. The results suggest that the subject exhibits a complete dynamically balanced gait during slow speeds while experiencing a controlled fall (end of swing phase) with faster speeds. This is quantified with the root-mean-square deviation (RMSD

  9. Segment and joint angles of hind limb during bipedal and quadrupedal walking of the bonobo (Pan paniscus).

    PubMed

    D'Août, Kristiaan; Aerts, Peter; De Clercq, Dirk; De Meester, Koen; Van Elsacker, Linda

    2002-09-01

    We describe segment angles (trunk, thigh, shank, and foot) and joint angles (hip, knee, and ankle) for the hind limbs of bonobos walking bipedally ("bent-hip bent-knee walking," 17 sequences) and quadrupedally (33 sequences). Data were based on video recordings (50 Hz) of nine subjects in a lateral view, walking at voluntary speed. The major differences between bipedal and quadrupedal walking are found in the trunk, thigh, and hip angles. During bipedal walking, the trunk is approximately 33-41 degrees more erect than during quadrupedal locomotion, although it is considerably more bent forward than in normal human locomotion. Moreover, during bipedal walking, the hip has a smaller range of motion (by 12 degrees ) and is more extended (by 20-35 degrees ) than during quadrupedal walking. In general, angle profiles in bonobos are much more variable than in humans. Intralimb phase relationships of subsequent joint angles show that hip-knee coordination is similar for bipedal and quadrupedal walking, and resembles the human pattern. The coordination between knee and ankle differs much more from the human pattern. Based on joint angles observed throughout stance phase and on the estimation of functional leg length, an efficient inverted pendulum mechanism is not expected in bonobos.

  10. a Novel Sideway Stability Control Method for Bipedal Walking Robot

    NASA Astrophysics Data System (ADS)

    Jo, H. Siswoyo; Mir-Nasiri, N.

    2011-06-01

    This paper presents a novel sensing and balancing method for bipedal walking robot. The proposed method involves the design of semi-rigid ankle joint to facilitate the responsive and accurate measurement of the sideway (sagittal) instability of the walking robot. The use of double balancing mass and the developed control algorithms provide a constant sideway stability of the robot while it walks in forward direction. The smooth legs trajectory planning then can be implemented successfully regardless of the robot sideway stability condition. The developed method is able to decouple the walking algorithms from the robot stability issues. Furthermore, the use of two different masses for the balancing helps to improve response time and efficiency of the balancing system. In this paper, the proposed method is tested on the simplified model of a robot balancing on its single leg and the feasibility of the method is confirmed by the simulation results obtained with MATLAB Simulink tools.

  11. Parallel elastic elements improve energy efficiency on the STEPPR bipedal walking robot

    DOE PAGES

    Mazumdar, Anirban; Spencer, Steven J.; Hobart, Clinton; ...

    2016-11-23

    This study describes how parallel elastic elements can be used to reduce energy consumption in the electric motor driven, fully-actuated, STEPPR bipedal walking robot without compromising or significantly limiting locomotive behaviors. A physically motivated approach is used to illustrate how selectively-engaging springs for hip adduction and ankle flexion predict benefits for three different flat ground walking gaits: human walking, human-like robot walking and crouched robot walking. Based on locomotion data, springs are designed and substantial reductions in power consumption are demonstrated using a bench dynamometer. These lessons are then applied to STEPPR (Sandia Transmission-Efficient Prototype Promoting Research), a fully actuatedmore » bipedal robot designed to explore the impact of tailored joint mechanisms on walking efficiency. Featuring high-torque brushless DC motors, efficient low-ratio transmissions, and high fidelity torque control, STEPPR provides the ability to incorporate novel joint-level mechanisms without dramatically altering high level control. Unique parallel elastic designs are incorporated into STEPPR, and walking data shows that hip adduction and ankle flexion springs significantly reduce the required actuator energy at those joints for several gaits. These results suggest that parallel joint springs offer a promising means of supporting quasi-static joint torques due to body mass during walking, relieving motors of the need to support these torques and substantially improving locomotive energy efficiency.« less

  12. Parallel elastic elements improve energy efficiency on the STEPPR bipedal walking robot

    SciTech Connect

    Mazumdar, Anirban; Spencer, Steven J.; Hobart, Clinton; Salton, Jonathan; Quigley, Morgan; Wu, Tingfan; Bertrand, Sylvain; Pratt, Jerry; Buerger, Stephen P.

    2016-11-23

    This study describes how parallel elastic elements can be used to reduce energy consumption in the electric motor driven, fully-actuated, STEPPR bipedal walking robot without compromising or significantly limiting locomotive behaviors. A physically motivated approach is used to illustrate how selectively-engaging springs for hip adduction and ankle flexion predict benefits for three different flat ground walking gaits: human walking, human-like robot walking and crouched robot walking. Based on locomotion data, springs are designed and substantial reductions in power consumption are demonstrated using a bench dynamometer. These lessons are then applied to STEPPR (Sandia Transmission-Efficient Prototype Promoting Research), a fully actuated bipedal robot designed to explore the impact of tailored joint mechanisms on walking efficiency. Featuring high-torque brushless DC motors, efficient low-ratio transmissions, and high fidelity torque control, STEPPR provides the ability to incorporate novel joint-level mechanisms without dramatically altering high level control. Unique parallel elastic designs are incorporated into STEPPR, and walking data shows that hip adduction and ankle flexion springs significantly reduce the required actuator energy at those joints for several gaits. These results suggest that parallel joint springs offer a promising means of supporting quasi-static joint torques due to body mass during walking, relieving motors of the need to support these torques and substantially improving locomotive energy efficiency.

  13. Exploring Toe Walking in a Bipedal Robot

    NASA Astrophysics Data System (ADS)

    Smith, James Andrew; Seyfarth, Andre

    The design and development of locomotory subsystems such as legs is a key issue in the broader topic of autonomous mobile systems. Simplification of substructures, sensing, actuation and control can aid to better understand the dynamics of legged locomotion and will make the implementation of legs in engineered systems more effective. This paper examines recent results in the development of toe walking on the JenaWalker II robot. The robot is shown, while supported on a treadmill, to be capable of accelerating from 0 to over 0.6 m/s without adjustment of control parameters such as hip actuator sweep frequency or amplitude. The resulting stable motion is due to the adaptability of the passive structures incorporated into the legs. The roles of the individual muscletendon groups are examined and a potential configuration for future heel-toe trials is suggested.

  14. Using intelligent controller to enhance the walking stability of bipedal walking robot

    NASA Astrophysics Data System (ADS)

    Hsieh, Tsung-Che; Chang, Chia-Der

    2016-07-01

    This paper is to improve the stability issue of the bipedal walking robot. The study of robot's pivot joint constructs the driver system to control the implementation. First, a Proportion-Integral-Derivative (PID) controller is designed by which is used the concept of tuning parameter to achieve the stability of the system. Second, Fuzzy controller and tradition PID controller is used to maintain output. It improved original PID controller efficacy. Finally, Artificial Neuro-Fuzzy Inference System (ANFIS) is utilized which is made the controller to achieve self-studying and modify the effect which is completed by the intelligent controller. It improved bipedal robot's stability control of realization. The result is verified that the walking stability of the bipedal walking robot in Matlab/Simulink. The intelligent controller has achieved the desired position of motor joint and the target stability performance.

  15. Collision-based mechanics of bipedal hopping.

    PubMed

    Gutmann, Anne K; Lee, David V; McGowan, Craig P

    2013-08-23

    The muscle work required to sustain steady-speed locomotion depends largely upon the mechanical energy needed to redirect the centre of mass and the degree to which this energy can be stored and returned elastically. Previous studies have found that large bipedal hoppers can elastically store and return a large fraction of the energy required to hop, whereas small bipedal hoppers can only elastically store and return a relatively small fraction. Here, we consider the extent to which large and small bipedal hoppers (tammar wallabies, approx. 7 kg, and desert kangaroo rats, approx. 0.1 kg) reduce the mechanical energy needed to redirect the centre of mass by reducing collisions. We hypothesize that kangaroo rats will reduce collisions to a greater extent than wallabies since kangaroo rats cannot elastically store and return as high a fraction of the mechanical energy of hopping as wallabies. We find that kangaroo rats use a significantly smaller collision angle than wallabies by employing ground reaction force vectors that are more vertical and center of mass velocity vectors that are more horizontal and thereby reduce their mechanical cost of transport. A collision-based approach paired with tendon morphometry may reveal this effect more generally among bipedal runners and quadrupedal trotters.

  16. Collision-based mechanics of bipedal hopping

    PubMed Central

    Gutmann, Anne K.; Lee, David V.; McGowan, Craig P.

    2013-01-01

    The muscle work required to sustain steady-speed locomotion depends largely upon the mechanical energy needed to redirect the centre of mass and the degree to which this energy can be stored and returned elastically. Previous studies have found that large bipedal hoppers can elastically store and return a large fraction of the energy required to hop, whereas small bipedal hoppers can only elastically store and return a relatively small fraction. Here, we consider the extent to which large and small bipedal hoppers (tammar wallabies, approx. 7 kg, and desert kangaroo rats, approx. 0.1 kg) reduce the mechanical energy needed to redirect the centre of mass by reducing collisions. We hypothesize that kangaroo rats will reduce collisions to a greater extent than wallabies since kangaroo rats cannot elastically store and return as high a fraction of the mechanical energy of hopping as wallabies. We find that kangaroo rats use a significantly smaller collision angle than wallabies by employing ground reaction force vectors that are more vertical and center of mass velocity vectors that are more horizontal and thereby reduce their mechanical cost of transport. A collision-based approach paired with tendon morphometry may reveal this effect more generally among bipedal runners and quadrupedal trotters. PMID:23843217

  17. Surprising trunk rotational capabilities in chimpanzees and implications for bipedal walking proficiency in early hominins.

    PubMed

    Thompson, Nathan E; Demes, Brigitte; O'Neill, Matthew C; Holowka, Nicholas B; Larson, Susan G

    2015-10-06

    Human walking entails coordinated out-of-phase axial rotations of the thorax and pelvis. A long-held assumption is that this ability relies on adaptations for trunk flexibility present in humans, but not in chimpanzees, other great apes, or australopithecines. Here we use three-dimensional kinematic analyses to show that, contrary to current thinking, chimpanzees walking bipedally rotate their lumbar and thoracic regions in a manner similar to humans. This occurs despite differences in the magnitude of trunk motion, and despite morphological differences in truncal 'rigidity' between species. These results suggest that, like humans and chimpanzees, early hominins walked with upper body rotations that countered pelvic rotation. We demonstrate that even if early hominins walked with pelvic rotations 50% larger than humans, they may have accrued the energetic and mechanical benefits of out-of-phase thoracic rotations. This would have allowed early hominins to reduce work and locomotor cost, improving walking efficiency early in hominin evolution.

  18. Three-dimensional kinematics of the pelvis and hind limbs in chimpanzee (Pan troglodytes) and human bipedal walking.

    PubMed

    O'Neill, Matthew C; Lee, Leng-Feng; Demes, Brigitte; Thompson, Nathan E; Larson, Susan G; Stern, Jack T; Umberger, Brian R

    2015-09-01

    The common chimpanzee (Pan troglodytes) is a facultative biped and our closest living relative. As such, the musculoskeletal anatomies of their pelvis and hind limbs have long provided a comparative context for studies of human and fossil hominin locomotion. Yet, how the chimpanzee pelvis and hind limb actually move during bipedal walking is still not well defined. Here, we describe the three-dimensional (3-D) kinematics of the pelvis, hip, knee and ankle during bipedal walking and compare those values to humans walking at the same dimensionless and dimensional velocities. The stride-to-stride and intraspecific variations in 3-D kinematics were calculated using the adjusted coefficient of multiple correlation. Our results indicate that humans walk with a more stable pelvis than chimpanzees, especially in tilt and rotation. Both species exhibit similar magnitudes of pelvis list, but with segment motion that is opposite in phasing. In the hind limb, chimpanzees walk with a more flexed and abducted limb posture, and substantially exceed humans in the magnitude of hip rotation during a stride. The average stride-to-stride variation in joint and segment motion was greater in chimpanzees than humans, while the intraspecific variation was similar on average. These results demonstrate substantial differences between human and chimpanzee bipedal walking, in both the sagittal and non-sagittal planes. These new 3-D kinematic data are fundamental to a comprehensive understanding of the mechanics, energetics and control of chimpanzee bipedalism. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Surprising trunk rotational capabilities in chimpanzees and implications for bipedal walking proficiency in early hominins

    PubMed Central

    Thompson, Nathan E.; Demes, Brigitte; O'Neill, Matthew C.; Holowka, Nicholas B.; Larson, Susan G.

    2015-01-01

    Human walking entails coordinated out-of-phase axial rotations of the thorax and pelvis. A long-held assumption is that this ability relies on adaptations for trunk flexibility present in humans, but not in chimpanzees, other great apes, or australopithecines. Here we use three-dimensional kinematic analyses to show that, contrary to current thinking, chimpanzees walking bipedally rotate their lumbar and thoracic regions in a manner similar to humans. This occurs despite differences in the magnitude of trunk motion, and despite morphological differences in truncal ‘rigidity' between species. These results suggest that, like humans and chimpanzees, early hominins walked with upper body rotations that countered pelvic rotation. We demonstrate that even if early hominins walked with pelvic rotations 50% larger than humans, they may have accrued the energetic and mechanical benefits of out-of-phase thoracic rotations. This would have allowed early hominins to reduce work and locomotor cost, improving walking efficiency early in hominin evolution. PMID:26441046

  20. Effects of electrical noise to a knee joint on quiet bipedal stance and treadmill walking.

    PubMed

    Kimura, T; Taki, C; Shiozawa, N; Kouzaki, M

    2013-01-01

    The present study assessed whether an unperceivable, noise-like electrical stimulation of a knee joint enhances the stability of quiet bipedal stance and treadmill walking in young subjects. The results showed that the slow postural sway measures in quiet bipedal stance were significantly reduced by the electrical noise (P<0.05). In the treadmill walking, low frequency component (below 1 Hz) of mediolateral acceleration, measured at the third lumbar vertebra, significantly decreased with the electrical noise (P<0.05), while there were no changes in the anteroposterior and vertical directions. These results indicate that the electrical noise to a knee joint can be applied to enhance postural control in quiet bipedal stance and treadmill walking.

  1. The dynamics of hylobatid bipedalism: evidence for an energy-saving mechanism?

    PubMed

    Vereecke, Evie E; D'Août, Kristiaan; Aerts, Peter

    2006-08-01

    When gibbons travel through the forest canopy, brachiation is alternated with short bipedal bouts over horizontal boughs. We know, from previous research, that brachiation is a very efficient locomotor mode that makes use of a pendulum-like exchange of energy, but to date, nothing is known about the dynamics of hylobatid bipedalism. We wondered if gibbons also make use of an efficient gait mechanism during bipedal locomotion. To investigate this, we calculated oscillations of the centre of mass (COM), energy fluctuations, recovery rates and power outputs from the 3D ground reaction forces. These ground reaction forces were collected during spontaneous bipedal locomotion of four untrained white-handed gibbons (Hylobates lar) over an instrumented walkway (with an AMTI force plate). Excursions of the COM are relatively large during hylobatid bipedalism and the fluctuations of potential and kinetic energy are largely in-phase. Together with the low inverted pendulum recovery rates, this points to a spring-mass mechanism during bipedal locomotion. Although the well-developed Achilles tendon of gibbons seems to be a good candidate for the storage and recoil of elastic energy, this is not supported by kinematical data of the ankle joint. Instead, we suggest that the knee extensor muscle tendon unit functions as an energy-saving mechanism during hylobatid bipedalism, but detailed anatomical data is needed to confirm this suggestion. At low speeds gibbons use either pendular or spring mechanics, but a clear gait transition as seen in most quadrupedal mammals is absent. At moderate to high velocities, gibbons use a bouncing gait, generally without aerial phases. This supports the view that aerial phases are not a prerequisite for spring-mass mechanics and reinforces the claim that duty factor alone should not be used to distinguish between a walk and run.

  2. Extracting Kinematic Parameters for Monkey Bipedal Walking from Cortical Neuronal Ensemble Activity

    PubMed Central

    Fitzsimmons, Nathan A.; Lebedev, Mikhail A.; Peikon, Ian D.; Nicolelis, Miguel A. L.

    2009-01-01

    The ability to walk may be critically impacted as the result of neurological injury or disease. While recent advances in brain–machine interfaces (BMIs) have demonstrated the feasibility of upper-limb neuroprostheses, BMIs have not been evaluated as a means to restore walking. Here, we demonstrate that chronic recordings from ensembles of cortical neurons can be used to predict the kinematics of bipedal walking in rhesus macaques – both offline and in real time. Linear decoders extracted 3D coordinates of leg joints and leg muscle electromyograms from the activity of hundreds of cortical neurons. As more complex patterns of walking were produced by varying the gait speed and direction, larger neuronal populations were needed to accurately extract walking patterns. Extraction was further improved using a switching decoder which designated a submodel for each walking paradigm. We propose that BMIs may one day allow severely paralyzed patients to walk again. PMID:19404411

  3. Simulation Studies of Bipedal Walking on the Moon and Mars

    NASA Astrophysics Data System (ADS)

    Yamada, Shin; Ohshima, Hiroshi; Yamaguchi, Tomofumi; Narukawa, Terumasa; Takahashi, Masaki; Hase, Kimitaka; Liu, Meigen; Mukai, Chiaki

    In order to walk upright on the Moon or Mars without falling, a specific walking strategy to account for altered gravitational conditions must be verified. We have therefore been studying changes in the kinematics of walking at different gravitational loads using a body weight suspension system. Our simulation consisted of three gravitational conditions: 1 g (Earth); 1/3 g (Mars); and 1/6 g (the Moon). Surface EMG recordings were taken from the leg muscles of subjects walking on a treadmill. Cadence, stance phase duration, and step length were calculated from the walking velocity and steps. Subsequent experiments revealed that muscle activity and the duration of the double support phase decreased as simulated gravity was reduced. These changes are apparently caused not only by the direct effects of unloading but also by kinematic adaptations to the same. It can be said that humans walk slowly with a shortened stride and elongated stance phase in order to adjust to low gravitational conditions. One major limitation of our study that may have affected walking stability was the fact that the suspension system was fixed to an immovable frame. We have begun further studies using a newer movable body weight suspension system to achieve more realistic simulations.

  4. Chimpanzee and human midfoot motion during bipedal walking and the evolution of the longitudinal arch of the foot.

    PubMed

    Holowka, Nicholas B; O'Neill, Matthew C; Thompson, Nathan E; Demes, Brigitte

    2017-03-01

    The longitudinal arch of the human foot is commonly thought to reduce midfoot joint motion to convert the foot into a rigid lever during push off in bipedal walking. In contrast, African apes have been observed to exhibit midfoot dorsiflexion following heel lift during terrestrial locomotion, presumably due to their possession of highly mobile midfoot joints. This assumed dichotomy between human and African ape midfoot mobility has recently been questioned based on indirect assessments of in vivo midfoot motion, such as plantar pressure and cadaver studies; however, direct quantitative analyses of African ape midfoot kinematics during locomotion remain scarce. Here, we used high-speed motion capture to measure three-dimensional foot kinematics in two male chimpanzees and five male humans walking bipedally at similar dimensionless speeds. We analyzed 10 steps per chimpanzee subject and five steps per human subject, and compared ranges of midfoot motion between species over stance phase, as well as within double- and single-limb support periods. Contrary to expectations, humans used a greater average range of midfoot motion than chimpanzees over the full duration of stance. This difference was driven by humans' dramatic plantarflexion and adduction of the midfoot joints during the second double-limb support period, which likely helps the foot generate power during push off. However, chimpanzees did use slightly but significantly more midfoot dorsiflexion than humans in the single limb-support period, during which heel lift begins. These results indicate that both stiffness and mobility are important to longitudinal arch function, and that the human foot evolved to utilize both during push off in bipedal walking. Thus, the presence of human-like midfoot joint morphology in fossil hominins should not be taken as indicating foot rigidity, but may signify the evolution of pedal anatomy conferring enhanced push off mechanics. Copyright © 2016 Elsevier Ltd. All rights

  5. Mechanisms for the acquisition of habitual bipedality: are there biomechanical reasons for the acquisition of upright bipedal posture?

    PubMed

    Preuschoft, Holger

    2004-05-01

    Morphology and biomechanics are linked by causal morphogenesis ('Wolff's law') and the interplay of mutations and selection (Darwin's 'survival of the fittest'). Thus shape-based selective pressures can be determined. In both cases we need to know which biomechanical factors lead to skeletal adaptation, and which ones exert selective pressures on body shape. Each bone must be able to sustain the greatest regularly occurring loads. Smaller loads are unlikely to lead to adaptation of morphology. The highest loads occur primarily in posture and locomotion, simply because of the effect of body weight (or its multiple). In the skull, however, it is biting and chewing that result in the greatest loads. Body shape adapted for an arboreal lifestyle also smooths the way towards bipedality. Hindlimb dominance, length of the limbs in relation to the axial skeleton, grasping hands and feet, mass distribution (especially of the limb segments), thoracic shape, rib curvatures, and the position of the centre of gravity are the adaptations to arboreality that also pre-adapt for bipedality. Five divergent locomotor/morphological types have evolved from this base: arm-swinging in gibbons, forelimb-dominated slow climbing in orangutans, quadrupedalism/climbing in the African apes, an unknown mix of climbing and bipedal walking in australopithecines, and the remarkably endurant bipedal walking of humans. All other apes are also facultative bipeds, but it is the biomechanical characteristics of bipedalism in orangutans, the most arboreal great ape, which is closest to that in humans. If not evolutionary accident, what selective factor can explain why two forms adopted bipedality? Most authors tend to connect bipedal locomotion with some aspect of progressively increasing distance between trees because of climatic changes. More precise factors, in accordance with biomechanical requirements, include stone-throwing, thermoregulation or wading in shallow water. Once bipedality has been

  6. Mechanisms for the acquisition of habitual bipedality: are there biomechanical reasons for the acquisition of upright bipedal posture?

    PubMed Central

    Preuschoft, Holger

    2004-01-01

    Morphology and biomechanics are linked by causal morphogenesis (‘Wolff's law’) and the interplay of mutations and selection (Darwin's ‘survival of the fittest’). Thus shape-based selective pressures can be determined. In both cases we need to know which biomechanical factors lead to skeletal adaptation, and which ones exert selective pressures on body shape. Each bone must be able to sustain the greatest regularly occurring loads. Smaller loads are unlikely to lead to adaptation of morphology. The highest loads occur primarily in posture and locomotion, simply because of the effect of body weight (or its multiple). In the skull, however, it is biting and chewing that result in the greatest loads. Body shape adapted for an arboreal lifestyle also smooths the way towards bipedality. Hindlimb dominance, length of the limbs in relation to the axial skeleton, grasping hands and feet, mass distribution (especially of the limb segments), thoracic shape, rib curvatures, and the position of the centre of gravity are the adaptations to arboreality that also pre-adapt for bipedality. Five divergent locomotor/morphological types have evolved from this base: arm-swinging in gibbons, forelimb-dominated slow climbing in orang-utans, quadrupedalism/climbing in the African apes, an unknown mix of climbing and bipedal walking in australopithecines, and the remarkably endurant bipedal walking of humans. All other apes are also facultative bipeds, but it is the biomechanical characteristics of bipedalism in orang-utans, the most arboreal great ape, which is closest to that in humans. If not evolutionary accident, what selective factor can explain why two forms adopted bipedality? Most authors tend to connect bipedal locomotion with some aspect of progressively increasing distance between trees because of climatic changes. More precise factors, in accordance with biomechanical requirements, include stone-throwing, thermoregulation or wading in shallow water. Once bipedality has

  7. An analysis of leg joint synergy during bipedal walking in Japanese macaques.

    PubMed

    Kaichida, Shoko; Hashizume, Yoshimitsu; Ogihara, Naomichi; Nishii, Jun

    2011-01-01

    We analyzed bipedal locomotion of Japanese macaques from the view point of leg joint synergy by the UCM (Uncontrolled manifold) analysis in order to examine how and when hip, knee and ankle joints cooperate so as to suppress the variances of the toe position relative to the hip position. Our results showed that joint synergy is exploited at some moments during walking. For instance, the variance of the vertical toe position was suppressed by joint synergy when the tip of the finger passes its lowest position from the ground. Some characteristics of the synergy pattern of macaques have been also reported in human walking, on the other hand, some differences between humans and macaques were found. For instance, high degree of joint synergy that suppresses the variance of hip height was observed around the end of stance phase in human walking, but such synergy was weak in macaques. The results suggest that different control strategies are used in bipedal walking of macaques and humans.

  8. Decentralized Feedback Controllers for Robust Stabilization of Periodic Orbits of Hybrid Systems: Application to Bipedal Walking

    PubMed Central

    Hamed, Kaveh Akbari; Gregg, Robert D.

    2016-01-01

    This paper presents a systematic algorithm to design time-invariant decentralized feedback controllers to exponentially and robustly stabilize periodic orbits for hybrid dynamical systems against possible uncertainties in discrete-time phases. The algorithm assumes a family of parameterized and decentralized nonlinear controllers to coordinate interconnected hybrid subsystems based on a common phasing variable. The exponential and H2 robust stabilization problems of periodic orbits are translated into an iterative sequence of optimization problems involving bilinear and linear matrix inequalities. By investigating the properties of the Poincaré map, some sufficient conditions for the convergence of the iterative algorithm are presented. The power of the algorithm is finally demonstrated through designing a set of robust stabilizing local nonlinear controllers for walking of an underactuated 3D autonomous bipedal robot with 9 degrees of freedom, impact model uncertainties, and a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg. PMID:28959117

  9. The lower limb and mechanics of walking in Australopithecus sediba.

    PubMed

    DeSilva, Jeremy M; Holt, Kenneth G; Churchill, Steven E; Carlson, Kristian J; Walker, Christopher S; Zipfel, Bernhard; Berger, Lee R

    2013-04-12

    The discovery of a relatively complete Australopithecus sediba adult female skeleton permits a detailed locomotor analysis in which joint systems can be integrated to form a comprehensive picture of gait kinematics in this late australopith. Here we describe the lower limb anatomy of Au. sediba and hypothesize that this species walked with a fully extended leg and with an inverted foot during the swing phase of bipedal walking. Initial contact of the lateral foot with the ground resulted in a large pronatory torque around the joints of the foot that caused extreme medial weight transfer (hyperpronation) into the toe-off phase of the gait cycle (late pronation). These bipedal mechanics are different from those often reconstructed for other australopiths and suggest that there may have been several forms of bipedalism during the Plio-Pleistocene.

  10. Locomotion in bonobos (Pan paniscus): differences and similarities between bipedal and quadrupedal terrestrial walking, and a comparison with other locomotor modes.

    PubMed

    D'Août, K; Vereecke, E; Schoonaert, K; De Clercq, D; Van Elsacker, L; Aerts, P

    2004-05-01

    One of the great ongoing debates in palaeo-anthropology is when, and how, hominids acquired habitual bipedal locomotion. The newly adopted bipedal gait and the ancestral quadrupedal gait are most often considered as very distinct, with each habitual locomotor mode showing corresponding anatomical adaptations. Bonobos (Pan paniscus), along with common chimpanzees (P. troglodytes), are the closest living relatives to humans and their locomotion is valuable for comparison with other primates, and to gain an insight in the acquisition of human bipedalism. Bonobos are habitual quadrupeds, but they also engage in bipedal locomotion, both on terrestrial and in arboreal substrates. In terms of kinematics and dynamics, the contrast between bipedal and quadrupedal walking seems to be more subtle than one might expect. Apart from the trunk being approximately 37 degrees more erect during bipedal locomotion, the leg movements are rather similar. Apart from the heel, plantar pressure distributions show subtle differences between bipedal and quadrupedal locomotion. Regardless, variability is high, and various intermediate forms of locomotion (e.g. tripedal walking) exist both in captivity and in the wild. Moreover, there is overlap between the characteristics of walking and other locomotor modes, as we show with new data of walking on an inclined pole and of vertical squat jumps. We suggest that there is great overlap between the many locomotor modes in bonobos, and that the required polyvalence is reflected in their anatomy. This may hamper the development of one highly specialized gait (i.e. bipedalism), which would constrain performance of the other types of locomotion.

  11. Locomotion in bonobos (Pan paniscus): differences and similarities between bipedal and quadrupedal terrestrial walking, and a comparison with other locomotor modes

    PubMed Central

    D’Août, K; Vereecke, E; Schoonaert, K; De Clercq, D; Van Elsacker, L; Aerts, P

    2004-01-01

    One of the great ongoing debates in palaeo-anthropology is when, and how, hominids acquired habitual bipedal locomotion. The newly adopted bipedal gait and the ancestral quadrupedal gait are most often considered as very distinct, with each habitual locomotor mode showing corresponding anatomical adaptations. Bonobos (Pan paniscus), along with common chimpanzees (P. troglodytes), are the closest living relatives to humans and their locomotion is valuable for comparison with other primates, and to gain an insight in the acquisition of human bipedalism. Bonobos are habitual quadrupeds, but they also engage in bipedal locomotion, both on terrestrial and in arboreal substrates. In terms of kinematics and dynamics, the contrast between bipedal and quadrupedal walking seems to be more subtle than one might expect. Apart from the trunk being approximately 37° more erect during bipedal locomotion, the leg movements are rather similar. Apart from the heel, plantar pressure distributions show subtle differences between bipedal and quadrupedal locomotion. Regardless, variability is high, and various intermediate forms of locomotion (e.g. tripedal walking) exist both in captivity and in the wild. Moreover, there is overlap between the characteristics of walking and other locomotor modes, as we show with new data of walking on an inclined pole and of vertical squat jumps. We suggest that there is great overlap between the many locomotor modes in bonobos, and that the required polyvalence is reflected in their anatomy. This may hamper the development of one highly specialized gait (i.e. bipedalism), which would constrain performance of the other types of locomotion. PMID:15198700

  12. Energy transformation during erect and 'bent-hip, bent-knee' walking by humans with implications for the evolution of bipedalism.

    PubMed

    Wang, W J; Crompton, R H; Li, Y; Gunther, M M

    2003-05-01

    We have previously reported that predictive dynamic modeling suggests that the 'bent-hip, bent-knee' gait, which some attribute to Australopithecus afarensis AL-288-1, would have been much more expensive in mechanical terms for this hominid than an upright gait. Normal walking by modern adult humans owes much of its efficiency to conservation of energy by transformation between its potential and kinetic states. These findings suggest the question if, and to what extent, energy transformation exists in 'bent-hip, bent-knee' gait. This study calculates energy transformation in humans walking upright, at three different speeds, and walking 'bent-hip, bent-knee'. Kinematic data were gathered from video sequences and kinetic (ground reaction force) data from synchronous forceplate measurement. Applying Newtonian mechanics to our experimental data, the fluctuations of kinetic and potential energy in the body centre of mass were obtained and the effects of energy transformation evaluated and compared. In erect walking the fluctuations of two forms of energy are indeed largely out-of-phase, so that energy transformation occurs and total energy is conserved. In 'bent-hip, bent-knee' walking, however, the fluctuations of the kinetic and potential energy are much more in-phase, so that energy transformation occurs to a much lesser extent. Among all modes of walking the highest energy recovery is obtained in subjectively 'comfortable' walking, the next highest in subjectively 'fast' or 'slow' walking, and the least lowest in 'bent-hip, bent-knee' walking. The results imply that if 'bent-hip, bent-knee' gait was indeed habitually practiced by early bipedal hominids, a very substantial (and in our view as yet unidentified) selective advantage would have had to accrue, to offset the selective disadvantages of 'bent-hip, bent-knee' gait in terms of energy transformation.

  13. Sensor Data Fusion for Body State Estimation in a Bipedal Robot and Its Feedback Control Application for Stable Walking

    PubMed Central

    Chen, Ching-Pei; Chen, Jing-Yi; Huang, Chun-Kai; Lu, Jau-Ching; Lin, Pei-Chun

    2015-01-01

    We report on a sensor data fusion algorithm via an extended Kalman filter for estimating the spatial motion of a bipedal robot. Through fusing the sensory information from joint encoders, a 6-axis inertial measurement unit and a 2-axis inclinometer, the robot’s body state at a specific fixed position can be yielded. This position is also equal to the CoM when the robot is in the standing posture suggested by the detailed CAD model of the robot. In addition, this body state is further utilized to provide sensory information for feedback control on a bipedal robot with walking gait. The overall control strategy includes the proposed body state estimator as well as the damping controller, which regulates the body position state of the robot in real-time based on instant and historical position tracking errors. Moreover, a posture corrector for reducing unwanted torque during motion is addressed. The body state estimator and the feedback control structure are implemented in a child-size bipedal robot and the performance is experimentally evaluated. PMID:25734644

  14. Sensor data fusion for body state estimation in a bipedal robot and its feedback control application for stable walking.

    PubMed

    Chen, Ching-Pei; Chen, Jing-Yi; Huang, Chun-Kai; Lu, Jau-Ching; Lin, Pei-Chun

    2015-02-27

    We report on a sensor data fusion algorithm via an extended Kalman filter for estimating the spatial motion of a bipedal robot. Through fusing the sensory information from joint encoders, a 6-axis inertial measurement unit and a 2-axis inclinometer, the robot's body state at a specific fixed position can be yielded. This position is also equal to the CoM when the robot is in the standing posture suggested by the detailed CAD model of the robot. In addition, this body state is further utilized to provide sensory information for feedback control on a bipedal robot with walking gait. The overall control strategy includes the proposed body state estimator as well as the damping controller, which regulates the body position state of the robot in real-time based on instant and historical position tracking errors. Moreover, a posture corrector for reducing unwanted torque during motion is addressed. The body state estimator and the feedback control structure are implemented in a child-size bipedal robot and the performance is experimentally evaluated.

  15. Analysis of joint force and torque for the human and non-human ape foot during bipedal walking with implications for the evolution of the foot

    PubMed Central

    Wang, Weijie; Abboud, Rami J; Günther, Michael M; Crompton, Robin H

    2014-01-01

    The feet of apes have a different morphology from those of humans. Until now, it has merely been assumed that the morphology seen in humans must be adaptive for habitual bipedal walking, as the habitual use of bipedal walking is generally regarded as one of the most clear-cut differences between humans and apes. This study asks simply whether human skeletal proportions do actually enhance foot performance during human-like bipedalism, by examining the influence of foot proportions on force, torque and work in the foot joints during simulated bipedal walking. Skeletons of the common chimpanzee, orangutan, gorilla and human were represented by multi-rigid-body models, where the components of the foot make external contact via finite element surfaces. The models were driven by identical joint motion functions collected from experiments on human walking. Simulated contact forces between the ground and the foot were found to be reasonably comparable with measurements made during human walking using pressure- and force-platforms. Joint force, torque and work in the foot were then predicted. Within the limitations of our model, the results show that during simulated human-like bipedal walking, (1) the human and non-human ape (NHA) feet carry similar joint forces, although the distributions of the forces differ; (2) the NHA foot incurs larger joint torques than does the human foot, although the human foot has higher values in the first tarso-metatarsal and metatarso-phalangeal joints, whereas the NHA foot incurs higher values in the lateral digits; and (3) total work in the metatarso-phalangeal joints is lower in the human foot than in the NHA foot. The results indicate that human foot proportions are indeed well suited to performance in normal human walking. PMID:24925580

  16. A neural network with central pattern generators entrained by sensory feedback controls walking of a bipedal model.

    PubMed

    Li, Wei; Szczecinski, Nicholas Stephen; Quinn, Roger D

    2017-07-27

    A neuromechanical simulation of a planar, bipedal walking robot has been developed. It is constructed as a simplified, planar musculoskeletal model of the biomechanics of the human lower body. The controller consists of a dynamic neural network with central pattern generators (CPGs) entrained by force and movement sensory feedback to generate appropriate muscle forces for walking. The CPG model is a two-level architecture, which consists of separate rhythm generator (RG) and pattern formation (PF) networks. The biped model walks stably in the sagittal plane without inertial sensors or a centralized posture controller or a "baby walker" to help overcome gravity. Its gait is similar to humans' and it walks at speeds from 0.850 m/s up to 1.289 m/s with leg length of 0.84 m. The model walks over small unknown steps (6% of leg length) and up and down 5° slopes without any additional higher level control actions. © 2017 IOP Publishing Ltd.

  17. Reactive and anticipatory control of posture and bipedal locomotion in a nonhuman primate.

    PubMed

    Mori, Futoshi; Nakajima, Katsumi; Tachibana, Atsumichi; Takasu, Chijiko; Mori, Masahiro; Tsujimoto, Toru; Tsukada, Hideo; Mori, Shigemi

    2004-01-01

    Bipedal locomotion is a common daily activity. Despite its apparent simplicity, it is a complex set of movements that requires the integrated neural control of multiple body segments. We have recently shown that the juvenile Japanese monkey, M. fuscata, can be operant-trained to walk bipedally on moving treadmill. It can control the body axis and lower limb movements when confronted by a change in treadmill speed. M. fuscata can also walk bipedally on a slanted treadmill. Furthermore, it can learn to clear an obstacle attached to the treadmill's belt. When failing to clear the obstacle, the monkey stumbles but quickly corrects its posture and the associated movements of multiple motor segments to again resume smooth bipedal walking. These results give indication that in learning to walk bipedally, M. fuscata transforms relevant visual, vestibular, proprioceptive, and exteroceptive sensory inputs into commands that engage both anticipatory and reactive motor mechanisms. Both mechanisms are essential for meeting external demands imposed upon posture and locomotion.

  18. A walk along DNA using bipedal migration of a dynamic and covalent crosslinker

    NASA Astrophysics Data System (ADS)

    Fakhari, Fazel; Rokita, Steven E.

    2014-11-01

    DNA has previously served as an excellent scaffold for molecular transport based on its non-covalent base pairing to assemble both stationary and mobile elements. Use of DNA can now be extended to transport systems based on reversible covalent chemistry. Autonomous and bipedal-like migration of crosslinking within helical DNA is made possible by tandem exchange of a quinone methide intermediate. In this report, net transport is illustrated to proceed over 10 base pairs. This process is driven towards its equilibrium distribution of crosslinks and consumes neither the walker nor the track irreversibly. Successful migration requires an electron-rich quinone methide to promote its regeneration and a continuous array of nucleophilic sites along its DNA track. Accordingly, net migration can be dramatically influenced by the presence of noncanonical structures within duplex DNA as demonstrated with a backbone nick and extrahelical bulge.

  19. Locomotor energetics and leg length in hominid bipedality.

    PubMed

    Kramer, P A; Eck, G G

    2000-05-01

    Because bipedality is the quintessential characteristic of Hominidae, researchers have compared ancient forms of bipedality with modern human gait since the first clear evidence of bipedal australopithecines was unearthed over 70 years ago. Several researchers have suggested that the australopithecine form of bipedality was transitional between the quadrupedality of the African apes and modern human bipedality and, consequently, inefficient. Other researchers have maintained that australopithecine bipedality was identical to that of Homo. But is it reasonable to require that all forms of hominid bipedality must be the same in order to be optimized? Most attempts to evaluate the locomotor effectiveness of the australopithecines have, unfortunately, assumed that the locomotor anatomy of modern humans is the exemplar of consummate bipedality. Modern human anatomy is, however, the product of selective pressures present in the particular milieu in which Homo arose and it is not necessarily the only, or even the most efficient, bipedal solution possible. In this report, we investigate the locomotion of Australopithecus afarensis, as represented by AL 288-1, using standard mechanical analyses. The osteological anatomy of AL 288-1 and movement profiles derived from modern humans are applied to a dynamic model of a biped, which predicts the mechanical power required by AL 288-1 to walk at various velocities. This same procedure is used with the anatomy of a composite modern woman and a comparison made. We find that AL 288-1 expends less energy than the composite woman when locomoting at walking speeds. This energetic advantage comes, however, at a price: the preferred transition speed (from a walk to a run) of AL 288-1 was lower than that of the composite woman. Consequently, the maximum daily range of AL 288-1 may well have been substantially smaller than that of modern people. The locomotor anatomy of A. afarensis may have been optimized for a particular ecological niche

  20. The mechanics of the gibbon foot and its potential for elastic energy storage during bipedalism.

    PubMed

    Vereecke, Evie E; Aerts, Peter

    2008-12-01

    The mechanics of the modern human foot and its specialization for habitual bipedalism are well understood. The windlass mechanism gives it the required stability for propulsion generation, and flattening of the arch and stretching of the plantar aponeurosis leads to energy saving. What is less well understood is how an essentially flat and mobile foot, as found in protohominins and extant apes, functions during bipedalism. This study evaluates the hypothesis that an energy-saving mechanism, by stretch and recoil of plantar connective tissues, is present in the mobile gibbon foot and provides a two-dimensional analysis of the internal joint mechanics of the foot during spontaneous bipedalism of gibbons using a four-link segment foot model. Available force and pressure data are combined with detailed foot kinematics, recorded with a high-speed camera at 250 Hz, to calculate the external joint moments at the metatarsophalangeal (MP), tarsometatarsal (TM) and talocrural (TC) joints. In addition, instantaneous joint powers are estimated to obtain insight into the propulsion-generating capacities of the internal foot joints. It is found that, next to a wide range of motion at the TC joint, substantial motion is observed at the TM and MP joint, underlining the importance of using a multi-segment foot model in primate gait analyses. More importantly, however, this study shows that although a compliant foot is less mechanically effective for push-off than a ;rigid' arched foot, it can contribute to the generation of propulsion in bipedal locomotion via stretch and recoil of the plantarflexor tendons and plantar ligaments.

  1. Controlled Reduction with Unactuated Cyclic Variables: Application to 3D Bipedal Walking with Passive Yaw Rotation

    PubMed Central

    Righetti, Ludovic

    2014-01-01

    This paper shows that viscous damping can shape momentum conservation laws in a manner that stabilizes yaw rotation and enables steering for underactuated 3D walking. We first show that unactuated cyclic variables can be controlled by passively shaped conservation laws given a stabilizing controller in the actuated coordinates. We then exploit this result to realize controlled geometric reduction with multiple unactuated cyclic variables. We apply this underactuated control strategy to a five-link 3D biped to produce exponentially stable straight-ahead walking and steering in the presence of passive yawing. PMID:25554709

  2. Controlled Reduction with Unactuated Cyclic Variables: Application to 3D Bipedal Walking with Passive Yaw Rotation.

    PubMed

    Gregg, Robert D; Righetti, Ludovic

    2013-10-01

    This paper shows that viscous damping can shape momentum conservation laws in a manner that stabilizes yaw rotation and enables steering for underactuated 3D walking. We first show that unactuated cyclic variables can be controlled by passively shaped conservation laws given a stabilizing controller in the actuated coordinates. We then exploit this result to realize controlled geometric reduction with multiple unactuated cyclic variables. We apply this underactuated control strategy to a five-link 3D biped to produce exponentially stable straight-ahead walking and steering in the presence of passive yawing.

  3. Exploiting Inherent Robustness and Natural Dynamics in the Control of Bipedal Walking Robots

    DTIC Science & Technology

    2000-06-01

    9.2.4 Multi-Joint Muscle Groups Animals have muscles which cross several joints [ Kapandji (1982)]. For example, the gastrocnemius activates both the...Walking Control of a Biped Robot Along a Potential Energy Conserving Orbit’, IEEE Transactions on Robotics and Automation 6(1), 431–438. Kapandji , I. A

  4. Mechatronic Wearable Exoskeletons for Bionic Bipedal Standing and Walking: A New Synthetic Approach.

    PubMed

    Onose, Gelu; Cârdei, Vladimir; Crăciunoiu, Ştefan T; Avramescu, Valeriu; Opriş, Ioan; Lebedev, Mikhail A; Constantinescu, Marian Vladimir

    2016-01-01

    During the last few years, interest has been growing to mechatronic and robotic technologies utilized in wearable powered exoskeletons that assist standing and walking. The available literature includes single-case reports, clinical studies conducted in small groups of subjects, and several recent systematic reviews. These publications have fulfilled promotional and marketing objectives but have not yet resulted in a fully optimized, practical wearable exoskeleton. Here we evaluate the progress and future directions in this field from a joint perspective of health professionals, manufacturers, and consumers. We describe the taxonomy of existing technologies and highlight the main improvements needed for the development and functional optimization of the practical exoskeletons.

  5. Mechatronic Wearable Exoskeletons for Bionic Bipedal Standing and Walking: A New Synthetic Approach

    PubMed Central

    Onose, Gelu; Cârdei, Vladimir; Crăciunoiu, Ştefan T.; Avramescu, Valeriu; Opriş, Ioan; Lebedev, Mikhail A.; Constantinescu, Marian Vladimir

    2016-01-01

    During the last few years, interest has been growing to mechatronic and robotic technologies utilized in wearable powered exoskeletons that assist standing and walking. The available literature includes single-case reports, clinical studies conducted in small groups of subjects, and several recent systematic reviews. These publications have fulfilled promotional and marketing objectives but have not yet resulted in a fully optimized, practical wearable exoskeleton. Here we evaluate the progress and future directions in this field from a joint perspective of health professionals, manufacturers, and consumers. We describe the taxonomy of existing technologies and highlight the main improvements needed for the development and functional optimization of the practical exoskeletons. PMID:27746711

  6. Formation mechanism of a basin of attraction for passive dynamic walking induced by intrinsic hyperbolicity

    NASA Astrophysics Data System (ADS)

    Obayashi, Ippei; Aoi, Shinya; Tsuchiya, Kazuo; Kokubu, Hiroshi

    2016-06-01

    Passive dynamic walking is a useful model for investigating the mechanical functions of the body that produce energy-efficient walking. The basin of attraction is very small and thin, and it has a fractal-like shape; this explains the difficulty in producing stable passive dynamic walking. The underlying mechanism that produces these geometric characteristics was not known. In this paper, we consider this from the viewpoint of dynamical systems theory, and we use the simplest walking model to clarify the mechanism that forms the basin of attraction for passive dynamic walking. We show that the intrinsic saddle-type hyperbolicity of the upright equilibrium point in the governing dynamics plays an important role in the geometrical characteristics of the basin of attraction; this contributes to our understanding of the stability mechanism of bipedal walking.

  7. A Bipedal DNA Brownian Motor with Coordinated Legs

    PubMed Central

    Omabegho, Tosan; Sha, Ruojie

    2012-01-01

    A significant challenge in engineering molecular motors is designing mechanisms to coordinate the motion between multiple domains of the motor so as to bias random motion. For bipedal motors, this challenge takes the form of coordinating the movement of the biped’s legs, so they can move in a synchronized fashion. To address this problem, we have constructed an autonomous DNA bipedal nanorobot that coordinates the action of its two legs by coupling room temperature thermal energy with the catalysis of metastable DNA fuel strand hybrids. This coupling leads to a chemically ratcheted unidirectional walk along a DNA track. By crosslinking aliquots of the walker covalently to its track in successive walking states, we demonstrate that the walker can complete a full walking cycle on a track whose length could be extended for longer walks. PMID:19342582

  8. Chimpanzee locomotor energetics and the origin of human bipedalism

    PubMed Central

    Sockol, Michael D.; Raichlen, David A.; Pontzer, Herman

    2007-01-01

    Bipedal walking is evident in the earliest hominins [Zollikofer CPE, Ponce de Leon MS, Lieberman DE, Guy F, Pilbeam D, et al. (2005) Nature 434:755–759], but why our unique two-legged gait evolved remains unknown. Here, we analyze walking energetics and biomechanics for adult chimpanzees and humans to investigate the long-standing hypothesis that bipedalism reduced the energy cost of walking compared with our ape-like ancestors [Rodman PS, McHenry HM (1980) Am J Phys Anthropol 52:103–106]. Consistent with previous work on juvenile chimpanzees [Taylor CR, Rowntree VJ (1973) Science 179:186–187], we find that bipedal and quadrupedal walking costs are not significantly different in our sample of adult chimpanzees. However, a more detailed analysis reveals significant differences in bipedal and quadrupedal cost in most individuals, which are masked when subjects are examined as a group. Furthermore, human walking is ≈75% less costly than both quadrupedal and bipedal walking in chimpanzees. Variation in cost between bipedal and quadrupedal walking, as well as between chimpanzees and humans, is well explained by biomechanical differences in anatomy and gait, with the decreased cost of human walking attributable to our more extended hip and a longer hindlimb. Analyses of these features in early fossil hominins, coupled with analyses of bipedal walking in chimpanzees, indicate that bipedalism in early, ape-like hominins could indeed have been less costly than quadrupedal knucklewalking. PMID:17636134

  9. Compass gait mechanics account for top walking speeds in ducks and humans

    PubMed Central

    Usherwood, James R.; Szymanek, Katie L.; Daley, Monica A.

    2010-01-01

    The constraints to maximum walking speed and the underlying cause of the walk-run transition remains controversial. However, the motions of the body and legs can be reduced to a few mechanical principles, which, if valid, impose simple physics-based limits to walking speed. Bipedal walking may be viewed as a vaulting gait, with the centre of mass passing over a stiff stance leg (an ‘inverted pendulum’), while the swing leg swings forward (as a pendulum). At its simplest, this forms a ‘compass gait’ walker, which has a maximum walking speed constrained by simple mechanics: walk too fast, or with too high a step length, and gravity fails to keep the stance foot attached to the floor. But how useful is such an extremely reductionist model? Here, we report measurements on a range of duck breeds as example unspecialized, non-planar, crouch-limbed walkers, and contrast these findings with previous measurements on humans, using the theoretical framework of compass gait walking. Ducks walked as inverted pendulums with near-passive swing-legs up to relative velocities around 0.5, remarkably consistent with the theoretical model. In contrast, top walking speeds in humans cannot be achieved with passive swing legs: humans, while still constrained by compass gait mechanics, extend their envelope of walking speeds by using relatively high step frequencies. Therefore, the capacity to drive the swing leg forward by walking humans may be a specialization for walking, allowing near-passive vaulting of the centre of mass at walking speeds 4/3 that possible with a passive (duck-like) swing leg. PMID:19011215

  10. Bipedal animals, and their differences from humans

    PubMed Central

    Alexander, R McN

    2004-01-01

    Humans, birds and (occasionally) apes walk bipedally. Humans, birds, many lizards and (at their highest speeds) cockroaches run bipedally. Kangaroos, some rodents and many birds hop bipedally, and jerboas and crows use a skipping gait. This paper deals only with walking and running bipeds. Chimpanzees walk with their knees bent and their backs sloping forward. Most birds walk and run with their backs and femurs sloping at small angles to the horizontal, and with their knees bent. These differences from humans make meaningful comparisons of stride length, duty factor, etc., difficult, even with the aid of dimensionless parameters that would take account of size differences, if dynamic similarity were preserved. Lizards and cockroaches use wide trackways. Humans exert a two-peaked pattern of force on the ground when walking, and an essentially single-peaked pattern when running. The patterns of force exerted by apes and birds are never as markedly two-peaked as in fast human walking. Comparisons with quadrupedal mammals of the same body mass show that human walking is relatively economical of metabolic energy, and human running is expensive. Bipedal locomotion is remarkably economical for wading birds, and expensive for geese and penguins. PMID:15198697

  11. Mechanical design of walking machines.

    PubMed

    Arikawa, Keisuke; Hirose, Shigeo

    2007-01-15

    The performance of existing actuators, such as electric motors, is very limited, be it power-weight ratio or energy efficiency. In this paper, we discuss the method to design a practical walking machine under this severe constraint with focus on two concepts, the gravitationally decoupled actuation (GDA) and the coupled drive. The GDA decouples the driving system against the gravitational field to suppress generation of negative power and improve energy efficiency. On the other hand, the coupled drive couples the driving system to distribute the output power equally among actuators and maximize the utilization of installed actuator power. First, we depict the GDA and coupled drive in detail. Then, we present actual machines, TITAN-III and VIII, quadruped walking machines designed on the basis of the GDA, and NINJA-I and II, quadruped wall walking machines designed on the basis of the coupled drive. Finally, we discuss walking machines that travel on three-dimensional terrain (3D terrain), which includes the ground, walls and ceiling. Then, we demonstrate with computer simulation that we can selectively leverage GDA and coupled drive by walking posture control.

  12. Bipedal locomotion in granular media

    NASA Astrophysics Data System (ADS)

    Kingsbury, Mark; Zhang, Tingnan; Goldman, Daniel

    Bipedal walking, locomotion characterized by alternating swing and double support phase, is well studied on ground where feet do not penetrate the substrate. On granular media like sand however, intrusion and extrusion phases also occur. In these phases, relative motion of the two feet requires that one or both feet slip through the material, degrading performance. To study walking in these phases, we designed and studied a planarized bipedal robot (1.6 kg, 42 cm) that walked in a fluidized bed of poppy seeds. We also simulated the robot in a multibody software environment (Chrono) using granular resistive force theory (RFT) to calculate foot forces. In experiment and simulation, the robot experienced slip during the intrusion phase, with the experiment presenting additional slip due to motor control error during the double support phase. This exaggerated slip gave insight (through analysis of ground reaction forces in simulation) into how slip occurs when relative motion exists between the two feet in the granular media, where the foot with higher relative drag forces (from its instantaneous orientation, rotation, relative direction of motion, and depth) remains stationary. With this relationship, we generated walking gaits for the robot to walk with minimal slip.

  13. Bipedality in chimpanzee (Pan troglodytes) and bonobo (Pan paniscus): testing hypotheses on the evolution of bipedalism.

    PubMed

    Videan, Elaine N; McGrew, W C

    2002-06-01

    A host of ecological, anatomical, and physiological selective pressures are hypothesized to have played a role in the evolution of hominid bipedalism. A referential model, based on the chimpanzee (Pan troglodytes) and bonobo (Pan paniscus), was used to test through experimental manipulation four hypotheses on the evolution of hominid bipedalism. The introduction of food piles (Carry hypothesis) increased locomotor bipedality in both species. Neither the introduction of branches (Display hypothesis) nor the construction of visual barriers (Vigilance hypothesis) altered bipedality in either species. Introduction of raised foraging structures (Forage hypothesis) increased postural bipedality in chimpanzees. These experimental manipulations provided support for carrying of portable objects and foraging on elevated food-items as plausible mechanisms that shaped bipedalism in hominids.

  14. Underwater bipedal locomotion by octopuses in disguise.

    PubMed

    Huffard, Christine L; Boneka, Farnis; Full, Robert J

    2005-03-25

    Here we report bipedal movement with a hydrostatic skeleton. Two species of octopus walk on two alternating arms using a rolling gait and appear to use the remaining six arms for camouflage. Octopus marginatus resembles a coconut, and Octopus (Abdopus) aculeatus, a clump of floating algae. Using underwater video, we analyzed the kinematics of their strides. Each arm was on the sand for more than half of the stride, qualifying this behavior as a form of walking.

  15. Form and function of the human and chimpanzee forefoot: implications for early hominin bipedalism

    PubMed Central

    Fernández, Peter J.; Holowka, Nicholas B.; Demes, Brigitte; Jungers, William L.

    2016-01-01

    During bipedal walking, modern humans dorsiflex their forefoot at the metatarsophalangeal joints (MTPJs) prior to push off, which tightens the plantar soft tissues to convert the foot into a stiff propulsive lever. Particular features of metatarsal head morphology such as “dorsal doming” are thought to facilitate this stiffening mechanism. In contrast, chimpanzees are believed to possess MTPJ morphology that precludes high dorsiflexion excursions during terrestrial locomotion. The morphological affinity of the metatarsal heads has been used to reconstruct locomotor behavior in fossil hominins, but few studies have provided detailed empirical data to validate the assumed link between morphology and function at the MTPJs. Using three-dimensional kinematic and morphometric analyses, we show that humans push off with greater peak dorsiflexion angles at all MTPJs than do chimpanzees during bipedal and quadrupedal walking, with the greatest disparity occurring at MTPJ 1. Among MTPJs 2–5, both species exhibit decreasing peak angles from medial to lateral. This kinematic pattern is mirrored in the morphometric analyses of metatarsal head shape. Analyses of Australopithecus afarensis metatarsals reveal morphology intermediate between humans and chimpanzees, suggesting that this species used different bipedal push-off kinematics than modern humans, perhaps resulting in a less efficient form of bipedalism. PMID:27464580

  16. Three-dimensional kinematics of capuchin monkey bipedalism.

    PubMed

    Demes, Brigitte

    2011-05-01

    Capuchin monkeys are known to use bipedalism when transporting food items and tools. The bipedal gait of two capuchin monkeys in the laboratory was studied with three-dimensional kinematics. Capuchins progress bipedally with a bent-hip, bent-knee gait. The knee collapses into flexion during stance and the hip drops in height. The knee is also highly flexed during swing to allow the foot which is plantarflexed to clear the ground. The forefoot makes first contact at touchdown. Stride frequency is high, and stride length and limb excursion low. Hind limb retraction is limited, presumably to reduce the pitch moment of the forward-leaning trunk. Unlike human bipedalism, the bipedal gait of capuchins is not a vaulting gait, and energy recovery from pendulum-like exchanges is unlikely. It extends into speeds at which humans and other animals run, but without a human-like gait transition. In this respect it resembles avian bipedal gaits. It remains to be tested whether energy is recovered through cyclic elastic storage and release as in bipedal birds at higher speeds. Capuchin bipedalism has many features in common with the facultative bipedalism of other primates which is further evidence for restrictions on a fully upright striding gait in primates that transition to bipedalism. It differs from the facultative bipedalism of other primates in the lack of an extended double-support phase and short aerial phases at higher speeds that make it a run by kinematic definition. This demonstrates that facultative bipedalism of quadrupedal primates need not necessarily be a walking gait.

  17. Adaptations for economical bipedal running: the effect of limb structure on three-dimensional joint mechanics

    PubMed Central

    Rubenson, Jonas; Lloyd, David G.; Heliams, Denham B.; Besier, Thor F.; Fournier, Paul A.

    2011-01-01

    The purpose of this study was to examine the mechanical adaptations linked to economical locomotion in cursorial bipeds. We addressed this question by comparing mass-matched humans and avian bipeds (ostriches), which exhibit marked differences in limb structure and running economy. We hypothesized that the nearly 50 per cent lower energy cost of running in ostriches is a result of: (i) lower limb-swing mechanical power, (ii) greater stance-phase storage and release of elastic energy, and (iii) lower total muscle power output. To test these hypotheses, we used three-dimensional joint mechanical measurements and a simple model to estimate the elastic and muscle contributions to joint work and power. Contradictory to our first hypothesis, we found that ostriches and humans generate the same amounts of mechanical power to swing the limbs at a similar self-selected running speed, indicating that limb swing probably does not contribute to the difference in energy cost of running between these species. In contrast, we estimated that ostriches generate 120 per cent more stance-phase mechanical joint power via release of elastic energy compared with humans. This elastic mechanical power occurs nearly exclusively at the tarsometatarso-phalangeal joint, demonstrating a shift of mechanical power generation to distal joints compared with humans. We also estimated that positive muscle fibre power is 35 per cent lower in ostriches compared with humans, and is accounted for primarily by higher capacity for storage and release of elastic energy. Furthermore, our analysis revealed much larger frontal and internal/external rotation joint loads during ostrich running than in humans. Together, these findings support the hypothesis that a primary limb structure specialization linked to economical running in cursorial species is an elevated storage and release of elastic energy in tendon. In the ostrich, energy-saving specializations may also include passive frontal and internal

  18. Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics

    PubMed Central

    Raichlen, David A.; Gordon, Adam D.; Harcourt-Smith, William E. H.; Foster, Adam D.; Haas, Wm. Randall

    2010-01-01

    Background Debates over the evolution of hominin bipedalism, a defining human characteristic, revolve around whether early bipeds walked more like humans, with energetically efficient extended hind limbs, or more like apes with flexed hind limbs. The 3.6 million year old hominin footprints at Laetoli, Tanzania represent the earliest direct evidence of hominin bipedalism. Determining the kinematics of Laetoli hominins will allow us to understand whether selection acted to decrease energy costs of bipedalism by 3.6 Ma. Methodology/Principal Findings Using an experimental design, we show that the Laetoli hominins walked with weight transfer most similar to the economical extended limb bipedalism of humans. Humans walked through a sand trackway using both extended limb bipedalism, and more flexed limb bipedalism. Footprint morphology from extended limb trials matches weight distribution patterns found in the Laetoli footprints. Conclusions These results provide us with the earliest direct evidence of kinematically human-like bipedalism currently known, and show that extended limb bipedalism evolved long before the appearance of the genus Homo. Since extended-limb bipedalism is more energetically economical than ape-like bipedalism, energy expenditure was likely an important selection pressure on hominin bipeds by 3.6 Ma. PMID:20339543

  19. Origin of bipedalism.

    PubMed

    Prost, J H

    1980-02-01

    Human and chimpanzee locomotor behaviors are described and compared using field patterns derived from measurements of the motions at the joints. Field patterns of human and ape bipedalism are so different that it is doubted whether the nonhuman type could ever have been a precursor of the human type. Chimpanzee quadrupedal vertical climbing and human bipedalism are, on the other hand, similar and a particular variety of this kind of climbing probably was the precursor of human bipedalism. Animals adapted to this variation would have had some brachiation-like morphological traits in their pectoral limbs and some hominid-like morphological traits in their pelvic limbs, traits anticipating the human condition. The australopithecines possessed these traits and must have been adapted to arboreal quadrupedal vertical climbing, having the capacity, at the same time, to perform facultative terrestrial bipedalism, moving on the ground in a manner visually identical to that of humans.

  20. Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees

    PubMed Central

    Demes, Brigitte; Richmond, Brian G.

    2016-01-01

    Bipedalism is a key adaptation that shaped human evolution, yet the timing and nature of its evolution remain unclear. Here we use new experimentally based approaches to investigate the locomotor mechanics preserved by the famous Pliocene hominin footprints from Laetoli, Tanzania. We conducted footprint formation experiments with habitually barefoot humans and with chimpanzees to quantitatively compare their footprints to those preserved at Laetoli. Our results show that the Laetoli footprints are morphologically distinct from those of both chimpanzees and habitually barefoot modern humans. By analysing biomechanical data that were collected during the human experiments we, for the first time, directly link differences between the Laetoli and modern human footprints to specific biomechanical variables. We find that the Laetoli hominin probably used a more flexed limb posture at foot strike than modern humans when walking bipedally. The Laetoli footprints provide a clear snapshot of an early hominin bipedal gait that probably involved a limb posture that was slightly but significantly different from our own, and these data support the hypothesis that important evolutionary changes to hominin bipedalism occurred within the past 3.66 Myr. PMID:27488647

  1. Vaulting mechanics successfully predict decrease in walk-run transition speed with incline.

    PubMed

    Hubel, Tatjana Y; Usherwood, James R

    2013-04-23

    There is an ongoing debate about the reasons underlying gait transition in terrestrial locomotion. In bipedal locomotion, the 'compass gait', a reductionist model of inverted pendulum walking, predicts the boundaries of speed and step length within which walking is feasible. The stance of the compass gait is energetically optimal-at walking speeds-owing to the absence of leg compression/extension; completely stiff limbs perform no work during the vaulting phase. Here, we extend theoretical compass gait vaulting to include inclines, and find good agreement with previous observations of changes in walk-run transition speed (approx. 1% per 1% incline). We measured step length and frequency for humans walking either on the level or up a 9.8 per cent incline and report preferred walk-run, walk-compliant-walk and maximum walk-run transition speeds. While the measured 'preferred' walk-run transition speed lies consistently below the predicted maximum walking speeds, and 'actual' maximum walking speeds are clearly above the predicted values, the onset of compliant walking in level as well as incline walking occurs close to the predicted values. These findings support the view that normal human walking is constrained by the physics of vaulting, but preferred absolute walk-run transition speeds may be influenced by additional factors.

  2. Resolving head rotation for human bipedalism.

    PubMed

    Fitzpatrick, Richard C; Butler, Jane E; Day, Brian L

    2006-08-08

    Alignment of the body to the gravitational vertical is considered to be the key to human bipedalism. However, changes to the semicircular canals during human evolution suggest that the sense of head rotation that they provide is important for modern human bipedal locomotion. When walking, the canals signal a mix of head rotations associated with path turns, balance perturbations, and other body movements. It is uncertain how the brain uses this information. Here, we show dual roles for the semicircular canals in balance control and navigation control. We electrically evoke a head-fixed virtual rotation signal from semicircular canal nerves as subjects walk in the dark with their head held in different orientations. Depending on head orientation, we can either steer walking by "remote control" or produce balance disturbances. This shows that the brain resolves the canal signal according to head posture into Earth-referenced orthogonal components and uses rotations in vertical planes to control balance and rotations in the horizontal plane to navigate. Because the semicircular canals are concerned with movement rather than detecting vertical alignment, this result shows the importance of movement control and agility rather than precise vertical alignment of the body for human bipedalism.

  3. Acquisition of bipedalism: the Miocene hominoid record and modern analogues for bipedal protohominids

    PubMed Central

    Nakatsukasa, Masato

    2004-01-01

    The well-known fossil hominoid Proconsul from the Early Miocene of Kenya was a non-specialized arboreal quadruped with strong pollicial/hallucial assisted grasping capability. It lacked most of the suspensory specializations acquired in living hominoids. Nacholapithecus, however, from the Middle Miocene of Kenya, although in part sharing with Proconsul the common primitive anatomical body design, was more specialized for orthograde climbing, ‘hoisting’ and bridging, with the glenoid fossae of the scapula probably being cranially orientated, the forelimbs proportionally large, and very long toes. Its tail loss suggests relatively slow movement, although tail loss may already have occurred in Proconsul. Nacholapithecus-like positional behaviour might thus have been a basis for development of more suspensory specialized positional behaviour in later hominoids. Unfortunately, after 13 Ma, there is a gap in the hominoid postcranial record in Africa until 6 Ma. Due to this gap, a scenario for later locomotor evolution prior to the divergence of Homo and Pan cannot be determined with certainty. The time gap also causes difficulties when we seek to determine polarities of morphological traits in very early hominids. Interpretation of the form–function relationships of postcranial features in incipient hominids will be difficult because it is predicted that they had incorporated bipedalism only moderately into their total positional repertoires. However, Japanese macaques, which are trained in traditional bipedal performance, may provide useful hints about bipedal adaptation in the protohominids. Kinematic analyses revealed that these macaques walked bipedally with a longer stride and lower stride frequency than used by ordinary macaques, owing to a more extended posture of the hindlimb joints. The body centre of gravity rises during the single-support phase of stance. Energetic studies of locomotion in these bipedal macaques revealed that energetic expenditure was 20

  4. Relationship between quantum walks and relativistic quantum mechanics

    SciTech Connect

    Chandrashekar, C. M.; Banerjee, Subhashish; Srikanth, R.

    2010-06-15

    Quantum walk models have been used as an algorithmic tool for quantum computation and to describe various physical processes. This article revisits the relationship between relativistic quantum mechanics and the quantum walks. We show the similarities of the mathematical structure of the decoupled and coupled forms of the discrete-time quantum walk to that of the Klein-Gordon and Dirac equations, respectively. In the latter case, the coin emerges as an analog of the spinor degree of freedom. Discrete-time quantum walk as a coupled form of the continuous-time quantum walk is also shown by transforming the decoupled form of the discrete-time quantum walk to the Schroedinger form. By showing the coin to be a means to make the walk reversible and that the Dirac-like structure is a consequence of the coin use, our work suggests that the relativistic causal structure is a consequence of conservation of information. However, decoherence (modeled by projective measurements on position space) generates entropy that increases with time, making the walk irreversible and thereby producing an arrow of time. The Lieb-Robinson bound is used to highlight the causal structure of the quantum walk to put in perspective the relativistic structure of the quantum walk, the maximum speed of walk propagation, and earlier findings related to the finite spread of the walk probability distribution. We also present a two-dimensional quantum walk model on a two-state system to which the study can be extended.

  5. Human bipedalism and body-mass index.

    PubMed

    Yi, Su Do; Noh, Jae Dong; Minnhagen, Petter; Song, Mi-Young; Chon, Tae-Soo; Kim, Beom Jun

    2017-06-16

    Body-mass index, abbreviated as BMI and given by M/H (2) with the mass M and the height H, has been widely used as a useful proxy to measure a general health status of a human individual. We generalise BMI in the form of M/H (p) and pursue to answer the question of the value of p for populations of animal species including human. We compare values of p for several different datasets for human populations with the ones obtained for other animal populations of fish, whales, and land mammals. All animal populations but humans analyzed in our work are shown to have p ≈ 3 unanimously. In contrast, human populations are different: As young infants grow to become toddlers and keep growing, the sudden change of p is observed at about one year after birth. Infants younger than one year old exhibit significantly larger value of p than two, while children between one and five years old show p ≈ 2, sharply different from other animal species. The observation implies the importance of the upright posture of human individuals. We also propose a simple mechanical model for a human body and suggest that standing and walking upright should put a clear division between bipedal human (p ≈ 2) and other animals (p ≈ 3).

  6. Mechanism And Control Of The Quadruped Walking Robot

    NASA Astrophysics Data System (ADS)

    Adachi, Hironori; Nakano, Eiji; Koyachi, Noriho

    1987-10-01

    This paper provides a description of the quadruped walking robot "TURTLE-1". A new link mechanism named ASTBALLEM is used for the legs of this robot. With this mechanism highly rigid and easily controllable legs are constructed. Each leg has two degrees of freedom and is driven by two DC servo motors. The motion of the legs is controlled by a micro computer and various gaits are generated. Static stability is maintained as the robot walks. Moreover, its walk is quasi-dynamic; that is, it has a manner of walking that has a two legged supporting period.

  7. Early Permian bipedal reptile.

    PubMed

    Berman, D S; Reisz, R R; Scott, D; Henrici, A C; Sumida, S S; Martens, T

    2000-11-03

    A 290-million-year-old reptilian skeleton from the Lower Permian (Asselian) of Germany provides evidence of abilities for cursorial bipedal locomotion, employing a parasagittal digitigrade posture. The skeleton is of a small bolosaurid, Eudibamus cursoris, gen. et sp. nov. and confirms the widespread distribution of Bolosauridae across Laurasia during this early stage of amniote evolution. E. cursoris is the oldest known representative of Parareptilia, a major clade of reptiles.

  8. Complementary mechanisms for upright balance during walking

    PubMed Central

    Fettrow, Tyler D.; Thompson, Elizabeth D.; Agada, Peter; McFadyen, Bradford J.; Jeka, John J.

    2017-01-01

    Lateral balance is a critical factor in keeping the human body upright during walking. Two important mechanisms for balance control are the stepping strategy, in which the foot placement is changed in the direction of a sensed fall to modulate how the gravitational force acts on the body, and the lateral ankle strategy, in which the body mass is actively accelerated by an ankle torque. Currently, there is minimal evidence about how these two strategies complement one another to achieve upright balance during locomotion. We use Galvanic vestibular stimulation (GVS) to induce the sensation of a fall at heel-off during gait initiation. We found that young healthy adults respond to the illusory fall using both the lateral ankle strategy and the stepping strategy. The stance foot center of pressure (CoP) is shifted in the direction of the perceived fall by ≈2.5 mm, starting ≈247 ms after stimulus onset. The foot placement of the following step is shifted by ≈15 mm in the same direction. The temporal delay between these two mechanisms suggests that they independently contribute to upright balance during locomotion, potentially in a serially coordinated manner. Modeling results indicate that without the lateral ankle strategy, a much larger step width is required to maintain upright balance, suggesting that the small but early CoP shift induced by the lateral ankle strategy is critical for upright stability during locomotion. The relative importance of each mechanism and how neurological disorders may affect their implementation remain an open question. PMID:28234936

  9. Disparity and convergence in bipedal archosaur locomotion

    PubMed Central

    Bates, K. T.; Schachner, E. R.

    2012-01-01

    This study aims to investigate functional disparity in the locomotor apparatus of bipedal archosaurs. We use reconstructions of hindlimb myology of extant and extinct archosaurs to generate musculoskeletal biomechanical models to test hypothesized convergence between bipedal crocodile-line archosaurs and dinosaurs. Quantitative comparison of muscle leverage supports the inference that bipedal crocodile-line archosaurs and non-avian theropods had highly convergent hindlimb myology, suggesting similar muscular mechanics and neuromuscular control of locomotion. While these groups independently evolved similar musculoskeletal solutions to the challenges of parasagittally erect bipedalism, differences also clearly exist, particularly the distinct hip and crurotarsal ankle morphology characteristic of many pseudosuchian archosaurs. Furthermore, comparative analyses of muscle design in extant archosaurs reveal that muscular parameters such as size and architecture are more highly adapted or optimized for habitual locomotion than moment arms. The importance of these aspects of muscle design, which are not directly retrievable from fossils, warns against over-extrapolating the functional significance of anatomical convergences. Nevertheless, links identified between posture, muscle moments and neural control in archosaur locomotion suggest that functional interpretations of osteological changes in limb anatomy traditionally linked to postural evolution in Late Triassic archosaurs could be constrained through musculoskeletal modelling. PMID:22112652

  10. The human foot and heel-sole-toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?

    PubMed

    Usherwood, J R; Channon, A J; Myatt, J P; Rankin, J W; Hubel, T Y

    2012-10-07

    Mechanically, the most economical gait for slow bipedal locomotion requires walking as an 'inverted pendulum', with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic 'M'-shaped vertical ground reaction forces of walking in humans reflect this impulse-vault-impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the 'M'-shaped walking ground reaction force profile does not require the plantigrade human foot or heel-sole-toe stance; it is maintained in tip-toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure--with ground-contacting heel behind ankle and toes in front--enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel-sole-toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all--largely avoiding the 'cost of muscle force'--during the passive vaulting phase.

  11. The human foot and heel–sole–toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?

    PubMed Central

    Usherwood, J. R.; Channon, A. J.; Myatt, J. P.; Rankin, J. W.; Hubel, T. Y.

    2012-01-01

    Mechanically, the most economical gait for slow bipedal locomotion requires walking as an ‘inverted pendulum’, with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic ‘M’-shaped vertical ground reaction forces of walking in humans reflect this impulse–vault–impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the ‘M’-shaped walking ground reaction force profile does not require the plantigrade human foot or heel–sole–toe stance; it is maintained in tip–toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure—with ground-contacting heel behind ankle and toes in front—enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel–sole–toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all—largely avoiding the ‘cost of muscle force’—during the passive vaulting phase. PMID:22572024

  12. 4. Band Wheel and Walking Beam Mechanism, Including Remains of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Band Wheel and Walking Beam Mechanism, Including Remains of Frame Belt House, Looking Southeast - David Renfrew Oil Rig, East side of Connoquenessing Creek, 0.4 mile North of confluence with Thorn Creek, Renfrew, Butler County, PA

  13. Planning energy-efficient bipedal locomotion on patterned terrain

    NASA Astrophysics Data System (ADS)

    Zamani, Ali; Bhounsule, Pranav A.; Taha, Ahmad

    2016-05-01

    Energy-efficient bipedal walking is essential in realizing practical bipedal systems. However, current energy-efficient bipedal robots (e.g., passive-dynamics-inspired robots) are limited to walking at a single speed and step length. The objective of this work is to address this gap by developing a method of synthesizing energy-efficient bipedal locomotion on patterned terrain consisting of stepping stones using energy-efficient primitives. A model of Cornell Ranger (a passive-dynamics inspired robot) is utilized to illustrate our technique. First, an energy-optimal trajectory control problem for a single step is formulated and solved. The solution minimizes the Total Cost Of Transport (TCOT is defined as the energy used per unit weight per unit distance travelled) subject to various constraints such as actuator limits, foot scuffing, joint kinematic limits, ground reaction forces. The outcome of the optimization scheme is a table of TCOT values as a function of step length and step velocity. Next, we parameterize the terrain to identify the location of the stepping stones. Finally, the TCOT table is used in conjunction with the parameterized terrain to plan an energy-efficient stepping strategy.

  14. Arboreality, terrestriality and bipedalism

    PubMed Central

    Crompton, Robin Huw; Sellers, William I.; Thorpe, Susannah K. S.

    2010-01-01

    The full publication of Ardipithecus ramidus has particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be run in silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage. PMID:20855304

  15. Arboreality, terrestriality and bipedalism.

    PubMed

    Crompton, Robin Huw; Sellers, William I; Thorpe, Susannah K S

    2010-10-27

    The full publication of Ardipithecus ramidus has particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be run in silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage.

  16. Mechanical work and efficiency in level walking and running

    PubMed Central

    Cavagna, G. A.; Kaneko, M.

    1977-01-01

    1. The mechanical power spent to accelerate the limbs relative to the trunk in level walking and running, Ẇint, has been measured at various `constant' speeds (3-33 km/hr) with the cinematographic procedure used by Fenn (1930a) at high speeds of running. 2. Ẇint increases approximately as the square of the speed of walking and running. For a given speed Ẇint is greater in walking than in running. 3. In walking above 3 km/hr, Ẇint is greater than the power spent to accelerate and lift the centre of mass of the body at each step, Ẇext (measured by Cavagna, Thys & Zamboni, 1976b). In running Ẇint < Ẇext up to about 20 km/hr, whereas at higher speeds Ẇint > Ẇext. 4. The total work done by the muscles was calculated as Wtot = ǀWintǀ + ǀWextǀ. Except that at the highest speeds of walking, the total work done per unit distance Wtot/km is greater in running than in walking. 5. The efficiency of positive work was measured from the ratio Wtot/Net energy expenditure: this is greater than 0·25 indicating that both in walking and in running the muscles utilize, during shortening, some energy stored during a previous phase of negative work (stretching). 6. In walking the efficiency reaches a maximum (0·35-0·40) at intermediate speeds, as may be expected from the properties of the contractile component of muscle. In running the efficiency increases steadily with speed (from 0·45 to 0·70-0·80) suggesting that positive work derives mainly from the passive recoil of muscle elastic elements and to a lesser extent from the active shortening of the contractile machinery. These findings are consistent with the different mechanics of the two exercises. PMID:874922

  17. Summary of Human Ankle Mechanical Impedance During Walking.

    PubMed

    Lee, Hyunglae; Rouse, Elliott J; Krebs, Hermano Igo

    2016-01-01

    The human ankle joint plays a critical role during walking and understanding the biomechanical factors that govern ankle behavior and provides fundamental insight into normal and pathologically altered gait. Previous researchers have comprehensively studied ankle joint kinetics and kinematics during many biomechanical tasks, including locomotion; however, only recently have researchers been able to quantify how the mechanical impedance of the ankle varies during walking. The mechanical impedance describes the dynamic relationship between the joint position and the joint torque during perturbation, and is often represented in terms of stiffness, damping, and inertia. The purpose of this short communication is to unify the results of the first two studies measuring ankle mechanical impedance in the sagittal plane during walking, where each study investigated differing regions of the gait cycle. Rouse et al. measured ankle impedance from late loading response to terminal stance, where Lee et al. quantified ankle impedance from pre-swing to early loading response. While stiffness component of impedance increases significantly as the stance phase of walking progressed, the change in damping during the gait cycle is much less than the changes observed in stiffness. In addition, both stiffness and damping remained low during the swing phase of walking. Future work will focus on quantifying impedance during the "push off" region of stance phase, as well as measurement of these properties in the coronal plane.

  18. Modular control of human walking: Adaptations to altered mechanical demands

    PubMed Central

    McGowan, Craig P.; Neptune, Richard R.; Clark, David J.; Kautz, Steven A.

    2009-01-01

    Studies have shown that the nervous system may adopt a control scheme in which synergistic muscle groups are controlled by common excitation patters, or modules, to simplify the coordination of movement tasks such as walking. A recent computer modeling and simulation study of human walking using experimentally derived modules as the control inputs provided evidence that individual modules are associated with specific biomechanical subtasks, such as generating body support and forward propulsion. The present study tests whether the modules identified during normal walking could produce simulations of walking when the mechanical demands were substantially altered. Walking simulations were generated that emulated human subjects who had their body weight and/or body mass increased and decreased by 25%. By scaling the magnitude of five module patterns, the simulation could emulate the subjects’ response to each condition by simply scaling the mechanical output from modules associated with specific biomechanical subtasks. Specifically, the modules associated with providing body support increased (decreased) their contribution to the vertical ground reaction force when body weight was increased (decreased), and the module associated with providing forward propulsion increased its contribution to the positive anterior-posterior ground reaction force and positive trunk power when the body mass was increased. The modules that contribute to controlling leg swing were unaffected by the perturbations. These results support the idea that the nervous system may use a modular control strategy and that flexible modulation of module recruitment intensity may be sufficient to meet large changes in mechanical demand. PMID:19879583

  19. Summary of Human Ankle Mechanical Impedance During Walking

    PubMed Central

    Rouse, Elliott J.; Krebs, Hermano Igo

    2016-01-01

    The human ankle joint plays a critical role during walking and understanding the biomechanical factors that govern ankle behavior and provides fundamental insight into normal and pathologically altered gait. Previous researchers have comprehensively studied ankle joint kinetics and kinematics during many biomechanical tasks, including locomotion; however, only recently have researchers been able to quantify how the mechanical impedance of the ankle varies during walking. The mechanical impedance describes the dynamic relationship between the joint position and the joint torque during perturbation, and is often represented in terms of stiffness, damping, and inertia. The purpose of this short communication is to unify the results of the first two studies measuring ankle mechanical impedance in the sagittal plane during walking, where each study investigated differing regions of the gait cycle. Rouse et al. measured ankle impedance from late loading response to terminal stance, where Lee et al. quantified ankle impedance from pre-swing to early loading response. While stiffness component of impedance increases significantly as the stance phase of walking progressed, the change in damping during the gait cycle is much less than the changes observed in stiffness. In addition, both stiffness and damping remained low during the swing phase of walking. Future work will focus on quantifying impedance during the “push off” region of stance phase, as well as measurement of these properties in the coronal plane. PMID:27766187

  20. The Cost of Leg Forces in Bipedal Locomotion: A Simple Optimization Study

    PubMed Central

    Rebula, John R.; Kuo, Arthur D.

    2015-01-01

    Simple optimization models show that bipedal locomotion may largely be governed by the mechanical work performed by the legs, minimization of which can automatically discover walking and running gaits. Work minimization can reproduce broad aspects of human ground reaction forces, such as a double-peaked profile for walking and a single peak for running, but the predicted peaks are unrealistically high and impulsive compared to the much smoother forces produced by humans. The smoothness might be explained better by a cost for the force rather than work produced by the legs, but it is unclear what features of force might be most relevant. We therefore tested a generalized force cost that can penalize force amplitude or its n-th time derivative, raised to the p-th power (or p-norm), across a variety of combinations for n and p. A simple model shows that this generalized force cost only produces smoother, human-like forces if it penalizes the rate rather than amplitude of force production, and only in combination with a work cost. Such a combined objective reproduces the characteristic profiles of human walking (R2 = 0.96) and running (R2 = 0.92), more so than minimization of either work or force amplitude alone (R2 = −0.79 and R2 = 0.22, respectively, for walking). Humans might find it preferable to avoid rapid force production, which may be mechanically and physiologically costly. PMID:25707000

  1. Locomotor versatility in the white-handed gibbon (Hylobates lar): a spatiotemporal analysis of the bipedal, tripedal, and quadrupedal gaits.

    PubMed

    Vereecke, Evie E; D'Août, Kristiaan; Aerts, Peter

    2006-05-01

    This study gives a qualitative and quantitative description of the different terrestrial locomotor modes of a group of white-handed gibbons (Hylobates lar) from the Wild Animal Park Planckendael, Belgium. The gibbons were filmed during voluntary locomotion on a grassy and smooth substrate and on a pole. These video images allowed us to define seven different gait types, based on spatial and temporal footfall patterns. Consequent digitization of the video images (n = 254) yielded duty factors, stride lengths, and stride frequencies of the fore- and hind limbs during locomotion at a wide range of speeds. These spatiotemporal gait characteristics were regressed against velocity, and the regression lines of the different gait types were compared. In addition, gibbon bipedalism was compared with bonobo (Pan paniscus) and human bipedalism. Gibbons appear to be very versatile animals, using a bipedal, tripedal, or quadrupedal gait during terrestrial travel with an overlapping speed range. The spatiotemporal characteristics of these gaits are largely similar, although they have clearly distinct footfall patterns. Bipedal walking on the pole is slightly different from terrestrial bipedalism, but differences between substrate types (grass vs. catwalk) are subtle. During bipedalism, gibbons increase both stride length and frequency to increase speed, just as humans and bonobos do, but at a given speed, gibbons take relatively larger strides at lower rates. Bipedal walking in gibbons also appears to be relatively fast-gibbons could keep on walking at speeds where humans have to start running. Apparently, adaptations for arboreal locomotion have not constrained the terrestrial locomotor abilities of gibbons. This may indicate that the step from an arboreal ancestral ape to a terrestrial, upright bipedal hominin might not be difficult and that structural specializations are not a prerequisite for adopting a (non-habitual) bipedal gait.

  2. First steps of bipedality in hominids: evidence from the atelid and proconsulid pelvis

    PubMed Central

    Machnicki, Allison L.; Spurlock, Linda B.; Strier, Karen B.

    2016-01-01

    Upright walking absent a bent-hip-bent-knee gait requires lumbar lordosis, a ubiquitous feature in all hominids for which it can be observed. Its first appearance is therefore a central problem in human evolution. Atelids, which use the tail during suspension, exhibit demonstrable lordosis and can achieve full extension of their hind limbs during terrestrial upright stance. Although obviously homoplastic with hominids, the pelvic mechanisms facilitating lordosis appear largely similar in both taxa with respect to abbreviation of upper iliac height coupled with broad sacral alae. Both provide spatial separation of the most caudal lumbar(s) from the iliac blades. A broad sacrum is therefore a likely facet of earliest hominid bipedality. All tailed monkeys have broad alae. By contrast all extant apes have very narrow sacra, which promote “trapping” of their most caudal lumbars to achieve lower trunk rigidity during suspension. The alae in the tailless proconsul Ekembo nyanzae appear to have been quite broad, a character state that may have been primitive in Miocene hominoids not yet adapted to suspension and, by extension, exaptive for earliest bipedality in the hominid/panid last common ancestor. This hypothesis receives strong support from other anatomical systems preserved in Ardipithecus ramidus. PMID:26793418

  3. First steps of bipedality in hominids: evidence from the atelid and proconsulid pelvis.

    PubMed

    Machnicki, Allison L; Spurlock, Linda B; Strier, Karen B; Reno, Philip L; Lovejoy, C Owen

    2016-01-01

    Upright walking absent a bent-hip-bent-knee gait requires lumbar lordosis, a ubiquitous feature in all hominids for which it can be observed. Its first appearance is therefore a central problem in human evolution. Atelids, which use the tail during suspension, exhibit demonstrable lordosis and can achieve full extension of their hind limbs during terrestrial upright stance. Although obviously homoplastic with hominids, the pelvic mechanisms facilitating lordosis appear largely similar in both taxa with respect to abbreviation of upper iliac height coupled with broad sacral alae. Both provide spatial separation of the most caudal lumbar(s) from the iliac blades. A broad sacrum is therefore a likely facet of earliest hominid bipedality. All tailed monkeys have broad alae. By contrast all extant apes have very narrow sacra, which promote "trapping" of their most caudal lumbars to achieve lower trunk rigidity during suspension. The alae in the tailless proconsul Ekembo nyanzae appear to have been quite broad, a character state that may have been primitive in Miocene hominoids not yet adapted to suspension and, by extension, exaptive for earliest bipedality in the hominid/panid last common ancestor. This hypothesis receives strong support from other anatomical systems preserved in Ardipithecus ramidus.

  4. Locomotor requirements for bipedal locomotion: a Delphi survey.

    PubMed

    Hedman, Lois Deming; Morris, David M; Graham, Cecilia L; Brown, Cynthia J; Ford, Matthew P; Ingram, Debbie A; Hilliard, Marjorie J; Salzman, Alice J

    2014-01-01

    Bipedal locomotor control requirements may be useful as classifications for walking dysfunction because they go beyond gait analysis to address all issues contributing to walking dysfunction. The objective of this study was to determine whether locomotor experts could achieve consensus about the requirements for bipedal locomotion. Locomotor experts from physical therapy and other related professions participated in an electronic mail Delphi survey. Experts recommended additions, deletions, rewording, and merges for 15 proposed locomotor requirements in round 1. In rounds 2 and 3, panelists commented on and rated the validity, mutual exclusiveness, and understandability of each requirement. Consensus was defined a priori as: (1) 75% or more panelists agree or strongly agree that a requirement is valid, mutually exclusive, and understandable in round 3; (2) no difference between round 2 and 3 ratings with kappa coefficients ≥.60; and (3) a reduction in panelists who commented and convergence of comments between rounds 1 and 3. Content analysis and nonparametric statistics were used. Fifty-eight panelists reached full consensus on 5 locomotor requirements (Initiation, Termination, Anticipatory Dynamic Balance, Multi-Task Capacity, and Walking Confidence) and partial consensus for 7 other requirements. There were no significant differences in ratings between rounds 2 and 3, and there was a decrease in the percentage of panelists who commented between rounds 1 and 3. The study's 6-month time frame may have contributed to panelist attrition. Locomotor experts achieved consensus on several bipedal locomotor requirements. With validation, these requirements can provide the framework for a clinically feasible and systematic diagnostic tool for physical therapists to categorize locomotor problems and standardize intervention for walking dysfunction.

  5. Central pattern generators for bipedal locomotion.

    PubMed

    Pinto, Carla M A; Golubitsky, Martin

    2006-09-01

    Golubitsky, Stewart, Buono and Collins proposed two models for the achitecture of central pattern generators (CPGs): one for bipeds (which we call leg) and one for quadrupeds (which we call quad). In this paper we use symmetry techniques to classify the possible spatiotemporal symmetries of periodic solutions that can exist in leg (there are 10 nontrivial types) and we explore the possibility that coordinated arm/leg rhythms can be understood, on the CPG level, by a small breaking of the symmetry in quad, which leads to a third CPG architecture arm. Rhythms produced by leg correspond to the bipedal gaits of walk, run, two-legged hop, two-legged jump, skip, gallop, asymmetric hop, and one-legged hop. We show that breaking the symmetry between fore and hind limbs in quad, which yields the CPG arm, leads to periodic solution types whose associated leg rhythms correspond to seven of the eight leg gaits found in leg; the missing biped gait is the asymmetric hop. However, when arm/leg coordination rhythms are considered, we find the correct rhythms only for the biped gaits of two-legged hop, run, and gallop. In particular, the biped gait walk, along with its arm rhythms, cannot be obtained by a small breaking of symmetry of any quadruped gait supported by quad.

  6. Elastic Coupling in Bipedally Crawling Cells

    NASA Astrophysics Data System (ADS)

    Loosley, Alex; Tang, Jay

    2012-02-01

    Periodic shape changes during cell migration are recorded in fast moving fish epithelial keratocytes where sticking and slipping at opposite sides of the cell's broad trailing edge generate bipedal locomotion and oscillatory lateral displacement of the nucleus. We use a two-dimensional finite element model to study the mechanical coupling, adhesion forces, and cell shapes that recapitulate the dynamics of these crawling cells. The model consists of elastically coupled point-like elements representing regions of the cell: leading edge, opposite sides of the trailing edge, and the nucleus. Based on simple assumptions, such as cell symmetry and localization of each element to a specific cellular region, we determine that there are only four viable permutations of elastic couplings between these four elements. We compare the four configurations and find that centralized elastic coupling to the cell nucleus and wide aspect ratio of the shape is necessary to mechanically generate realistic bipedal shape dynamics and lateral displacement of the nucleus. We suggest one configuration that is most realistic. The dynamics of this configuration are strongly dependent on the elasticity between peripheral elements, but not on the elasticity between these elements and the nucleus.

  7. Brief communication: arboreal bipedalism in Bwindi chimpanzees.

    PubMed

    Stanford, Craig B

    2002-09-01

    Evidence of the form and function of bipedal behavior in nonhuman primates provides critical evidence to test theories about the origins of hominid bipedalism. Bipedalism has long been considered an evolutionarily interesting but rare behavior in wild chimpanzees. During May 2001, chimpanzees of the Ruhija community in the Bwindi Impenetrable National Park, Uganda, engaged in an exceptional frequency of arboreal bipedalism when feeding in large Ficus trees. Seventy-eight bipedal bouts of at least 5 sec duration were recorded for the entire community (0.49 bouts/hr), with a mean duration of 13.7 sec (+/-1.6 sec). The animals employed many variations on the bipedal postural theme, ranging from erect standing on the largest substrates while grasping overhead limbs for support, to standing on one leg while suspending the other leg in space, to extended-lean standing, in which bipedal standing transitioned into horizontal arm-leg suspension as the animal reached for more distant fruits. Bipedalism was used as part of a behavioral repertoire that integrated brachiation, four-limbed suspension, and forelimb-supported standing for effective small-fruit foraging. These observations suggest that under certain ecological conditions, arboreal bipedalism can be an important posture for wild chimpanzees, and may have been an important behavioral precursor to full terrestrial bipedalism. Copyright 2002 Wiley-Liss, Inc.

  8. Generation of human bipedal locomotion by a bio-mimetic neuro-musculo-skeletal model.

    PubMed

    Ogihara, N; Yamazaki, N

    2001-01-01

    To emulate the actual neuro-control mechanism of human bipedal locomotion, an anatomically and physiologically based neuro-musculo-skeletal model is developed. The human musculo-skeletal system is constructed as seven rigid links in a sagittal plane, with a total of nine principal muscles. The nervous system consists of an alpha motoneuron and proprioceptors such as a muscle spindle and a Golgi tendon organ for each muscle. At the motoneurons, feedback signals from the proprioceptors are integrated with the signal induced by foot-ground contact and input from the rhythm pattern generator; a muscle activation signal is produced accordingly. Weights of connection in the neural network are optimized using a genetic algorithm, thus maximizing walking distance and minimizing energy consumption. The generated walking pattern is in remarkably good agreement with that of actual human walking, indicating that the locomotory pattern could be generated automatically, according to the musculoskeletal structures and the connections of the peripheral nervous system, particularly due to the reciprocal innervation in the muscle spindles. Using the proposed model, the flow of sensory-motor information during locomotion is estimated and a possible neuro-control mechanism is discussed.

  9. Bipedalism in lizards: whole-body modelling reveals a possible spandrel.

    PubMed Central

    Aerts, Peter; Van Damme, Raoul; D'Août, Kristiaan; Van Hooydonck, Bieke

    2003-01-01

    This paper illustrates how simple mechanical models based on morphological, ethological, ecological and phylogenetic data can add to discussions in evolutionary biology. Bipedal locomotion has evolved on numerous occasions in lizards. Traits that appear repeatedly in independent evolutionary lines are often considered adaptive, but the exact advantages of bipedal locomotion in lizards remain debated. Earlier claims that bipedalism would increase maximal running speed or would be energetically advantageous have been questioned. Here, we use 'whole body' mechanical modelling to provide an alternative solution to the riddle. The starting point is the intermittent running style combined with the need for a high manoeuvrability characterizing many small lizard species. Manoeuvrability benefits from a caudal shift of the centre of mass of the body (body-COM), because forces to change the heading and to align the body to this new heading do not conflict with each other. The caudally situated body-COM, however, might result in a lift of the front part of the body when accelerating (intermittent style), thus resulting in bipedal running bouts. Based on a momentum-impulse approach the effect of acceleration is quantified for a mechanical model, a virtual lizard (three segments) based on the morphometrics of Acanthodactylus erythrurus (a small lacertid lizard). Biologically relevant input (dimensions, inertial properties, step cycle information, etc.) results in an important lift of the front part of the body and observable distances passively covered bipedally as a consequence of the acceleration. In this way, no functional explanation of the phenomenon of lizard bipedalism is required and bipedalism can probably be considered non-adaptive in many cases. This does not exclude, however, some species that may have turned this consequence to their benefit. For instance, instantaneous manipulation of the position of the centre of the body-COM allows stable, persisting bipedal

  10. Mechanical Energy Recovery during Walking in Patients with Parkinson Disease

    PubMed Central

    Dipaola, Mariangela; Pavan, Esteban E.; Cattaneo, Andrea; Frazzitta, Giuseppe; Pezzoli, Gianni; Cavallari, Paolo; Frigo, Carlo A.

    2016-01-01

    The mechanisms of mechanical energy recovery during gait have been thoroughly investigated in healthy subjects, but never described in patients with Parkinson disease (PD). The aim of this study was to investigate whether such mechanisms are preserved in PD patients despite an altered pattern of locomotion. We consecutively enrolled 23 PD patients (mean age 64±9 years) with bilateral symptoms (H&Y ≥II) if able to walk unassisted in medication-off condition (overnight suspension of all dopaminergic drugs). Ten healthy subjects (mean age 62±3 years) walked both at their ‘preferred’ and ‘slow’ speeds, to match the whole range of PD velocities. Kinematic data were recorded by means of an optoelectronic motion analyzer. For each stride we computed spatio-temporal parameters, time-course and range of motion (ROM) of hip, knee and ankle joint angles. We also measured kinetic (Wk), potential (Wp), total (WtotCM) energy variations and the energy recovery index (ER). Along with PD progression, we found a significant correlation of WtotCM and Wp with knee ROM and in particular with knee extension in terminal stance phase. Wk and ER were instead mainly related to gait velocity. In PD subjects, the reduction of knee ROM significantly diminished both Wp and WtotCM. Rehabilitation treatments should possibly integrate passive and active mobilization of knee to prevent a reduction of gait-related energetic components. PMID:27258183

  11. Mechanical Energy Recovery during Walking in Patients with Parkinson Disease.

    PubMed

    Dipaola, Mariangela; Pavan, Esteban E; Cattaneo, Andrea; Frazzitta, Giuseppe; Pezzoli, Gianni; Cavallari, Paolo; Frigo, Carlo A; Isaias, Ioannis U

    2016-01-01

    The mechanisms of mechanical energy recovery during gait have been thoroughly investigated in healthy subjects, but never described in patients with Parkinson disease (PD). The aim of this study was to investigate whether such mechanisms are preserved in PD patients despite an altered pattern of locomotion. We consecutively enrolled 23 PD patients (mean age 64±9 years) with bilateral symptoms (H&Y ≥II) if able to walk unassisted in medication-off condition (overnight suspension of all dopaminergic drugs). Ten healthy subjects (mean age 62±3 years) walked both at their 'preferred' and 'slow' speeds, to match the whole range of PD velocities. Kinematic data were recorded by means of an optoelectronic motion analyzer. For each stride we computed spatio-temporal parameters, time-course and range of motion (ROM) of hip, knee and ankle joint angles. We also measured kinetic (Wk), potential (Wp), total (WtotCM) energy variations and the energy recovery index (ER). Along with PD progression, we found a significant correlation of WtotCM and Wp with knee ROM and in particular with knee extension in terminal stance phase. Wk and ER were instead mainly related to gait velocity. In PD subjects, the reduction of knee ROM significantly diminished both Wp and WtotCM. Rehabilitation treatments should possibly integrate passive and active mobilization of knee to prevent a reduction of gait-related energetic components.

  12. Bipedal tool use strengthens chimpanzee hand preferences

    PubMed Central

    Braccini, Stephanie; Lambeth, Susan; Schapiro, Steve; Fitch, W. Tecumseh

    2015-01-01

    The degree to which non-human primate behavior is lateralized, at either individual or population levels, remains controversial. We investigated the relationship between hand preference and posture during tool use in chimpanzees (Pan troglodytes) during bipedal tool use. We experimentally induced tool use in a supported bipedal posture, an unsupported bipedal posture, and a seated posture. Neither bipedal tool use nor these supported conditions have been previously evaluated in apes. The hypotheses tested were 1) bipedal posture will increase the strength of hand preference, and 2) a bipedal stance, without the use of one hand for support, will elicit a right hand preference. Results supported the first, but not the second hypothesis: bipedalism induced the subjects to become more lateralized, but not in any particular direction. Instead, it appears that subtle pre-existing lateral biases, to either the right or left, were emphasized with increasing postural demands. This result has interesting implications for theories of the evolution of tool use and bipedalism, as the combination of bipedalism and tool use may have helped drive extreme lateralization in modern humans, but cannot alone account for the preponderance of right-handedness. PMID:20089294

  13. Virtual Slope Control of a Forward Dynamic Bipedal Walker

    PubMed Central

    Russell, S.; Granata, K. P.; Sheth, P.

    2006-01-01

    Active joint torques are the primary source of power and control in dynamic walking motion. However the amplitude, rate, timing and phasic behavior of the joint torques necessary to achieve a natural and stable performance are difficult to establish. The goal of this study was to demonstrate the feasibility and stable behavior of an actively controlled bipedal walking simulation wherein the natural system dynamics were preserved by an active, nonlinear, state-feedback controller patterned after passive downhill walking. A two degree-of-freedom, forward-dynamic simulation was implemented with active joint torques applied at the hip joints and stance leg ankle. Kinematic trajectories produced by the active walker were similar to passive dynamic walking with active joint torques influenced by prescribed walking velocity. The control resulted in stable steady-state gait patterns, i.e. eigenvalue magnitudes of the stride function were less than one. The controller coefficient analogous to the virtual slope was modified to successfully control average walking velocity. Furture developments are necessary to expand the range of walking velocities. PMID:15868794

  14. Whole body mechanics of stealthy walking in cats.

    PubMed

    Bishop, Kristin L; Pai, Anita K; Schmitt, Daniel

    2008-01-01

    The metabolic cost associated with locomotion represents a significant part of an animal's metabolic energy budget. Therefore understanding the ways in which animals manage the energy required for locomotion by controlling muscular effort is critical to understanding limb design and the evolution of locomotor behavior. The assumption that energetic economy is the most important target of natural selection underlies many analyses of steady animal locomotion, leading to the prediction that animals will choose gaits and postures that maximize energetic efficiency. Many quadrupedal animals, particularly those that specialize in long distance steady locomotion, do in fact reduce the muscular contribution required for walking by adopting pendulum-like center of mass movements that facilitate exchange between kinetic energy (KE) and potential energy (PE). However, animals that are not specialized for long distance steady locomotion may face a more complex set of requirements, some of which may conflict with the efficient exchange of mechanical energy. For example, the "stealthy" walking style of cats may demand slow movements performed with the center of mass close to the ground. Force plate and video data show that domestic cats (Felis catus, Linnaeus, 1758) have lower mechanical energy recovery than mammals specialized for distance. A strong negative correlation was found between mechanical energy recovery and diagonality in the footfalls and there was also a negative correlation between limb compression and diagonality of footfalls such that more crouched postures tended to have greater diagonality. These data show a previously unrecognized mechanical relationship in which crouched postures are associated with changes in footfall pattern which are in turn related to reduced mechanical energy recovery. Low energy recovery was not associated with decreased vertical oscillations of the center of mass as theoretically predicted, but rather with posture and footfall pattern

  15. Kinematics and dynamics analysis of a quadruped walking robot with parallel leg mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Sang, Lingfeng; Hu, Xing; Zhang, Dianfan; Yu, Hongnian

    2013-09-01

    It is desired to require a walking robot for the elderly and the disabled to have large capacity, high stiffness, stability, etc. However, the existing walking robots cannot achieve these requirements because of the weight-payload ratio and simple function. Therefore, Improvement of enhancing capacity and functions of the walking robot is an important research issue. According to walking requirements and combining modularization and reconfigurable ideas, a quadruped/biped reconfigurable walking robot with parallel leg mechanism is proposed. The proposed robot can be used for both a biped and a quadruped walking robot. The kinematics and performance analysis of a 3-UPU parallel mechanism which is the basic leg mechanism of a quadruped walking robot are conducted and the structural parameters are optimized. The results show that performance of the walking robot is optimal when the circumradius R, r of the upper and lower platform of leg mechanism are 161.7 mm, 57.7 mm, respectively. Based on the optimal results, the kinematics and dynamics of the quadruped walking robot in the static walking mode are derived with the application of parallel mechanism and influence coefficient theory, and the optimal coordination distribution of the dynamic load for the quadruped walking robot with over-determinate inputs is analyzed, which solves dynamic load coupling caused by the branches’ constraint of the robot in the walk process. Besides laying a theoretical foundation for development of the prototype, the kinematics and dynamics studies on the quadruped walking robot also boost the theoretical research of the quadruped walking and the practical applications of parallel mechanism.

  16. The calcaneus of Australopithecus afarensis and its implications for the evolution of bipedality.

    PubMed

    Latimer, B; Lovejoy, C O

    1989-03-01

    Calcanei from African apes, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that occurred in this bone as a result of the transition to terrestrial bipedality. Features analyzed include the cross-sectional area and volume of the calcaneal tuber, the geometry and orientation of the articular surfaces, and the surface topography of the calcaneal corpus. Calcaneal morphology is unequivocal in its partitioning of quadrupedal pongids and bipedal hominids.

  17. The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals.

    PubMed

    Persons, W Scott; Currie, Philip J

    2017-02-27

    Bipedalism is a trait basal to, and widespread among, dinosaurs. It has been previously argued that bipedalism arose in the ancestors of dinosaurs for the function of freeing the forelimbs to serve as predatory weapons. However, this argument does not explain why bipedalism was retained among numerous herbivorous groups of dinosaurs. We argue that bipedalism arose in the dinosaur line for the purpose of enhanced cursoriality. Modern facultatively bipedal lizards offer an analog for the first stages in the evolution of dinosaurian bipedalism. Many extant lizards assume a bipedal stance while attempting to flee predators at maximum speed. Bipedalism, when combined with a caudofemoralis musculature, has cursorial advantages because the caudofemoralis provides a greater source of propulsion to the hindlimbs than is generally available to the forelimbs. That cursorial advantage explains the relative abundance of cursorial facultative bipeds and obligate bipeds among fossil diapsids and the relative scarcity of either among mammals. Having lost their caudofemoralis in the Permian, perhaps in the context of adapting to a fossorial lifestyle, the mammalian line has been disinclined towards bipedalism, but, having never lost the caudofemoralis of their ancestors, cursorial avemetatarsalians (bird-line archosaurs) were naturally inclined towards bipedalism.

  18. Adaptation mechanism of interlimb coordination in human split-belt treadmill walking through learning of foot contact timing: a robotics study

    PubMed Central

    Fujiki, Soichiro; Aoi, Shinya; Funato, Tetsuro; Tomita, Nozomi; Senda, Kei; Tsuchiya, Kazuo

    2015-01-01

    Human walking behaviour adaptation strategies have previously been examined using split-belt treadmills, which have two parallel independently controlled belts. In such human split-belt treadmill walking, two types of adaptations have been identified: early and late. Early-type adaptations appear as rapid changes in interlimb and intralimb coordination activities when the belt speeds of the treadmill change between tied (same speed for both belts) and split-belt (different speeds for each belt) configurations. By contrast, late-type adaptations occur after the early-type adaptations as a gradual change and only involve interlimb coordination. Furthermore, interlimb coordination shows after-effects that are related to these adaptations. It has been suggested that these adaptations are governed primarily by the spinal cord and cerebellum, but the underlying mechanism remains unclear. Because various physiological findings suggest that foot contact timing is crucial to adaptive locomotion, this paper reports on the development of a two-layered control model for walking composed of spinal and cerebellar models, and on its use as the focus of our control model. The spinal model generates rhythmic motor commands using an oscillator network based on a central pattern generator and modulates the commands formulated in immediate response to foot contact, while the cerebellar model modifies motor commands through learning based on error information related to differences between the predicted and actual foot contact timings of each leg. We investigated adaptive behaviour and its mechanism by split-belt treadmill walking experiments using both computer simulations and an experimental bipedal robot. Our results showed that the robot exhibited rapid changes in interlimb and intralimb coordination that were similar to the early-type adaptations observed in humans. In addition, despite the lack of direct interlimb coordination control, gradual changes and after-effects in the

  19. Adaptation mechanism of interlimb coordination in human split-belt treadmill walking through learning of foot contact timing: a robotics study.

    PubMed

    Fujiki, Soichiro; Aoi, Shinya; Funato, Tetsuro; Tomita, Nozomi; Senda, Kei; Tsuchiya, Kazuo

    2015-09-06

    Human walking behaviour adaptation strategies have previously been examined using split-belt treadmills, which have two parallel independently controlled belts. In such human split-belt treadmill walking, two types of adaptations have been identified: early and late. Early-type adaptations appear as rapid changes in interlimb and intralimb coordination activities when the belt speeds of the treadmill change between tied (same speed for both belts) and split-belt (different speeds for each belt) configurations. By contrast, late-type adaptations occur after the early-type adaptations as a gradual change and only involve interlimb coordination. Furthermore, interlimb coordination shows after-effects that are related to these adaptations. It has been suggested that these adaptations are governed primarily by the spinal cord and cerebellum, but the underlying mechanism remains unclear. Because various physiological findings suggest that foot contact timing is crucial to adaptive locomotion, this paper reports on the development of a two-layered control model for walking composed of spinal and cerebellar models, and on its use as the focus of our control model. The spinal model generates rhythmic motor commands using an oscillator network based on a central pattern generator and modulates the commands formulated in immediate response to foot contact, while the cerebellar model modifies motor commands through learning based on error information related to differences between the predicted and actual foot contact timings of each leg. We investigated adaptive behaviour and its mechanism by split-belt treadmill walking experiments using both computer simulations and an experimental bipedal robot. Our results showed that the robot exhibited rapid changes in interlimb and intralimb coordination that were similar to the early-type adaptations observed in humans. In addition, despite the lack of direct interlimb coordination control, gradual changes and after-effects in the

  20. Automaticity of walking: functional significance, mechanisms, measurement and rehabilitation strategies

    PubMed Central

    Clark, David J.

    2015-01-01

    Automaticity is a hallmark feature of walking in adults who are healthy and well-functioning. In the context of walking, “automaticity” refers to the ability of the nervous system to successfully control typical steady state walking with minimal use of attention-demanding executive control resources. Converging lines of evidence indicate that walking deficits and disorders are characterized in part by a shift in the locomotor control strategy from healthy automaticity to compensatory executive control. This is potentially detrimental to walking performance, as an executive control strategy is not optimized for locomotor control. Furthermore, it places excessive demands on a limited pool of executive reserves. The result is compromised ability to perform basic and complex walking tasks and heightened risk for adverse mobility outcomes including falls. Strategies for rehabilitation of automaticity are not well defined, which is due to both a lack of systematic research into the causes of impaired automaticity and to a lack of robust neurophysiological assessments by which to gauge automaticity. These gaps in knowledge are concerning given the serious functional implications of compromised automaticity. Therefore, the objective of this article is to advance the science of automaticity of walking by consolidating evidence and identifying gaps in knowledge regarding: (a) functional significance of automaticity; (b) neurophysiology of automaticity; (c) measurement of automaticity; (d) mechanistic factors that compromise automaticity; and (e) strategies for rehabilitation of automaticity. PMID:25999838

  1. Biped walking robot based on a 2-UPU+2-UU parallel mechanism

    NASA Astrophysics Data System (ADS)

    Miao, Zhihuai; Yao, Yan'an; Kong, Xianwen

    2014-03-01

    Existing biped robots mainly fall into two categories: robots with left and right feet and robots with upper and lower feet. The load carrying capability of a biped robot is quite limited since the two feet of a walking robot supports the robot alternatively during walking. To improve the load carrying capability, a novel biped walking robot is proposed based on a 2-UPU+2-UU parallel mechanism. The biped walking robot is composed of two identical platforms(feet) and four limbs, including two UPU(universal-prismatic-universal serial chain) limbs and two UU limbs. To enhance its terrain adaptability like articulated vehicles, the two feet of the biped walking robot are designed as two vehicles in detail. The conditions that the geometric parameters of the feet must satisfy are discussed. The degrees-of-freedom of the mechanism is analyzed by using screw theory. Gait analysis, kinematic analysis and stability analysis of the mechanism are carried out to verify the structural design parameters. The simulation results validate the feasibility of walking on rugged terrain. Experiments with a physical prototype show that the novel biped walking robot can walk stably on smooth terrain. Due to its unique feet design and high stiffness, the biped walking robot may adapt to rugged terrain and is suitable for load-carrying.

  2. Dynamic Simulation and Analysis of Human Walking Mechanism

    NASA Astrophysics Data System (ADS)

    Azahari, Athirah; Siswanto, W. A.; Ngali, M. Z.; Salleh, S. Md.; Yusup, Eliza M.

    2017-01-01

    Behaviour such as gait or posture may affect a person with the physiological condition during daily activities. The characteristic of human gait cycle phase is one of the important parameter which used to described the human movement whether it is in normal gait or abnormal gait. This research investigates four types of crouch walking (upright, interpolated, crouched and severe) by simulation approach. The assessment are conducting by looking the parameters of hamstring muscle joint, knee joint and ankle joint. The analysis results show that based on gait analysis approach, the crouch walking have a weak pattern of walking and postures. Short hamstring and knee joint is the most influence factor contributing to the crouch walking due to excessive hip flexion that typically accompanies knee flexion.

  3. Single Session of Functional Electrical Stimulation-Assisted Walking Produces Corticomotor Symmetry Changes Related to Changes in Poststroke Walking Mechanics.

    PubMed

    Palmer, Jacqueline A; Hsiao, HaoYuan; Wright, Tamara; Binder-Macleod, Stuart A

    2017-05-01

    Recent research demonstrated that the symmetry of corticomotor drive with the paretic and nonparetic plantarflexor muscles was related to the biomechanical ankle moment strategy that people with chronic stroke used to achieve their greatest walking speeds. Rehabilitation strategies that promote corticomotor balance might improve poststroke walking mechanics and enhance functional ambulation. The study objectives were to test the effectiveness of a single session of gait training using functional electrical stimulation (FES) to improve plantarflexor corticomotor symmetry and plantarflexion ankle moment symmetry and to determine whether changes in corticomotor symmetry were related to changes in ankle moment symmetry within the session. This was a repeated-measures crossover study. On separate days, 20 people with chronic stroke completed a session of treadmill walking either with or without the use of FES of their ankle dorsi- and plantarflexor muscles. We calculated plantarflexor corticomotor symmetry using transcranial magnetic stimulation and plantarflexion ankle moment symmetry during walking between the paretic and the nonparetic limbs before and after each session. We compared changes and tested relationships between corticomotor symmetry and ankle moment symmetry following each session. Following the session with FES, there was an increase in plantarflexor corticomotor symmetry that was related to the observed increase in ankle moment symmetry. In contrast, following the session without FES, there were no changes in corticomotor symmetry or ankle moment symmetry. No stratification was made on the basis of lesion size, location, or clinical severity. These findings demonstrate, for the first time (to our knowledge), the ability of a single session of gait training with FES to induce positive corticomotor plasticity in people in the chronic stage of stroke recovery. They also provide insight into the neurophysiologic mechanisms underlying improvements in

  4. The how and why of arm swing during human walking.

    PubMed

    Meyns, Pieter; Bruijn, Sjoerd M; Duysens, Jacques

    2013-09-01

    Humans walk bipedally, and thus, it is unclear why they swing their arms. In this paper, we will review the mechanisms and functions of arm swinging in human gait. First, we discuss the potential advantages of having swinging arms. Second, we go into the detail on the debate whether arm swing is arising actively or passively, where we will conclude that while a large part of arm swinging is mechanically passive, there is an active contribution of muscles (i.e. an activity that is not merely caused by stretch reflexes). Third, we describe the possible function of the active muscular contribution to arm swinging in normal gait, and discuss the possibility that a Central Pattern Generator (CPG) generates this activity. Fourth, we discuss examples from pathological cases, in which arm swinging is affected. Moreover, using the ideas presented, we suggest ways in which arm swing may be used as a therapeutic aid. We conclude that (1) arm swing should be seen as an integral part of human bipedal gait, arising mostly from passive movements, which are stabilized by active muscle control, which mostly originates from locomotor circuits in the central nervous system (2) arm swinging during normal bipedal gait most likely serves to reduce energy expenditure and (3) arm swinging may be of therapeutic value.

  5. Haptic feedback helps bipedal coordination.

    PubMed

    Roelofsen, Eefje G J; Bosga, Jurjen; Rosenbaum, David A; Nijhuis-van der Sanden, Maria W G; Hullegie, Wim; van Cingel, Robert; Meulenbroek, Ruud G J

    2016-10-01

    The present study investigated whether special haptic or visual feedback would facilitate the coordination of in-phase, cyclical feet movements of different amplitudes. Seventeen healthy participants sat with their feet on sliding panels that were moved externally over the same or different amplitudes. The participants were asked to generate simultaneous knee flexion-extension movements, or to let their feet be dragged, resulting in reference foot displacements of 150 mm and experimental foot displacements of 150, 120, or 90 mm. Four types of feedback were given: (1) special haptic feedback, involving actively following the motions of the sliders manipulated by two confederates, (2) haptic feedback resulting from passive motion, (3) veridical visual feedback, and (4) enhanced visual feedback. Both with respect to amplitude assimilation effects, correlations and standard deviation of relative phase, the results showed that enhanced visual feedback did not facilitate bipedal independence, but haptic feedback with active movement did. Implications of the findings for movement rehabilitation contexts are discussed.

  6. Tuataras and salamanders show that walking and running mechanics are ancient features of tetrapod locomotion

    PubMed Central

    Reilly, Stephen M; McElroy, Eric J; Andrew Odum, R; Hornyak, Valerie A

    2006-01-01

    The lumbering locomotor behaviours of tuataras and salamanders are the best examples of quadrupedal locomotion of early terrestrial vertebrates. We show they use the same walking (out-of-phase) and running (in-phase) patterns of external mechanical energy fluctuations of the centre-of-mass known in fast moving (cursorial) animals. Thus, walking and running centre-of-mass mechanics have been a feature of tetrapods since quadrupedal locomotion emerged over 400 million years ago. When walking, these sprawling animals save external mechanical energy with the same pendular effectiveness observed in cursorial animals. However, unlike cursorial animals (that change footfall patterns and mechanics with speed), tuataras and salamanders use only diagonal couplet gaits and indifferently change from walking to running mechanics with no significant change in total mechanical energy. Thus, the change from walking to running is not related to speed and the advantage of walking versus running is unclear. Furthermore, lumbering mechanics in primitive tetrapods is reflected in having total mechanical energy driven by potential energy (rather than kinetic energy as in cursorial animals) and relative centre-of-mass displacements an order of magnitude greater than cursorial animals. Thus, large vertical displacements associated with lumbering locomotion in primitive tetrapods may preclude their ability to increase speed. PMID:16777753

  7. Muscle force production during bent-knee, bent-hip walking in humans.

    PubMed

    Foster, Adam D; Raichlen, David A; Pontzer, Herman

    2013-09-01

    Researchers have long debated the locomotor posture used by the earliest bipeds. While many agree that by 3-4 Ma (millions of years ago), hominins walked with an extended-limb human style of bipedalism, researchers are still divided over whether the earliest bipeds walked like modern humans, or walked with a more bent-knee, bent-hip (BKBH) ape-like form of locomotion. Since more flexed postures are associated with higher energy costs, reconstructing early bipedal mechanics has implications for the selection pressures that led to upright walking. The purpose of this study is to determine how modern human anatomy functions in BKBH walking to clarify the links between morphology and energy costs in different mechanical regimes. Using inverse dynamics, we calculated muscle force production at the major limb joints in humans walking in two modes, both with extended limbs and BKBH. We found that in BKBH walking, humans must produce large muscle forces at the knee to support body weight, leading to higher estimated energy costs. However, muscle forces at the hip remained similar in BKBH and extended limb walking, suggesting that anatomical adaptations for hip extension in humans do not necessarily diminish the effective mechanical advantage at the hip in more flexed postures. We conclude that the key adaptations for economical walking, regardless of joint posture, seem to center on maintaining low muscle forces at the hip, primarily by keeping low external moments at the hip. We explore the implications of these results for interpreting locomotor energetics in early hominins, including australopithecines and Ardipithecus ramidus.

  8. The pendular mechanism does not determine the optimal speed of loaded walking on gradients.

    PubMed

    Gomeñuka, Natalia Andrea; Bona, Renata Luisa; da Rosa, Rodrigo Gomes; Peyré-Tartaruga, Leonardo Alexandre

    2016-06-01

    The pendular mechanism does not act as a primary mechanism in uphill walking due to the monotonic behavior of the mechanical energies of the center of mass. Nevertheless, recent evidence shows that there is an important minimization of energy expenditure by the pendular mechanism during walking on uphill gradients. In this study, we analyzed the optimum speed (OPT) of loaded human walking and the pendulum-like determining variables (Recovery R, Instantaneous pendular re-conversion Rint, and Congruity percentage %Cong). Ten young men walked on a treadmill at five different speeds and at three different treadmill incline gradients (0, +7 and +15%), with and without a load carried in their backpacks. We used indirect calorimetry and 3D motion analysis, and all of the data were analyzed by computational algorithms. Rint increased at higher speeds and decreased with increasing gradient. R and %Cong decreased with increasing gradient and increased with speed, independent of load. Thus, energy conversion by the pendular mechanism during walking on a 15% gradient is supported, and although this mechanism can explain the maintenance of OPT at low walking speeds, the pendular mechanism does not fully explain the energy minimization at higher speeds.

  9. The role of physical activity in changes in walking mechanics with age.

    PubMed

    Boyer, Katherine A; Andriacchi, Thomas P; Beaupre, Gary S

    2012-05-01

    While age-related declines in walking mechanics have been documented, it remains unclear if changes in walking mechanics with age occur as a natural consequence of aging and to what extent these changes are related to a reduction in fitness and physical activity with aging. The study aim was to determine if the walking mechanics of an older (>50) yet highly active population are different from a younger population (<40). Gait mechanics data for 79 middle-aged (50-64 yrs) and 54 older (65-80 yrs) individuals with ≥ 7500 steps/day, based on a 7 day activity monitoring history, and 33 younger adults (ages 18-40) were collected. The older subjects did not reduce self-selected walking speed relative to the younger subjects. However, the walking speed was maintained by increasing cadence while reducing stride-length for middle-aged and older subjects. Middle-aged and older adults had less ankle dorsi-flexion landing at heel-strike and older adults also had less plantar flexion at toe-off. Small decreases in the ankle dorsi-flexion moments (p=0.019, p=0.008) and increases in the hip extension moments (p=0.004, p=0.005) were found for two normalized walking speeds for the middle-aged and older adults compared to the young adults. These results provide quantitative evidence that increased activity with aging can mitigate declines in walking performance and mechanics with age. The high volume of walking activity in the older subjects did not fully prevent changes in gait mechanics, but may have minimized the magnitude of age-related changes on ambulatory function relative to other reports of older inactive subjects. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Spinopelvic pathways to bipedality: why no hominids ever relied on a bent-hip–bent-knee gait

    PubMed Central

    Lovejoy, C. Owen; McCollum, Melanie A.

    2010-01-01

    Until recently, the last common ancestor of African apes and humans was presumed to resemble living chimpanzees and bonobos. This was frequently extended to their locomotor pattern leading to the presumption that knuckle-walking was a likely ancestral pattern, requiring bipedality to have emerged as a modification of their bent-hip-bent-knee gait used during erect walking. Research on the development and anatomy of the vertebral column, coupled with new revelations from the fossil record (in particular, Ardipithecus ramidus), now demonstrate that these presumptions have been in error. Reassessment of the potential pathway to early hominid bipedality now reveals an entirely novel sequence of likely morphological events leading to the emergence of upright walking. PMID:20855303

  11. Spinopelvic pathways to bipedality: why no hominids ever relied on a bent-hip-bent-knee gait.

    PubMed

    Lovejoy, C Owen; McCollum, Melanie A

    2010-10-27

    Until recently, the last common ancestor of African apes and humans was presumed to resemble living chimpanzees and bonobos. This was frequently extended to their locomotor pattern leading to the presumption that knuckle-walking was a likely ancestral pattern, requiring bipedality to have emerged as a modification of their bent-hip-bent-knee gait used during erect walking. Research on the development and anatomy of the vertebral column, coupled with new revelations from the fossil record (in particular, Ardipithecus ramidus), now demonstrate that these presumptions have been in error. Reassessment of the potential pathway to early hominid bipedality now reveals an entirely novel sequence of likely morphological events leading to the emergence of upright walking.

  12. Split-belt Treadmill Walking Alters Lower Extremity Frontal Plane Mechanics.

    PubMed

    Roper, Jaimie A; Roemmich, Ryan T; Tillman, Mark D; Terza, Matthew J; Hass, Chris J

    2017-01-13

    Interventions that manipulate gait speed may also affect the control of frontal plane mechanics. Expanding the current knowledge of frontal plane adaptations during split-belt treadmill walking could advance our understanding of the influence of asymmetries in gait speed on frontal plane mechanics and provide insight into the breadth of adaptations required by split-belt walking. Thirteen young, healthy participants, free from lower extremity injury walked on a split-belt treadmill with belts moving simultaneously at different speeds. We examined frontal plane mechanics of the ankle, knee, and hip joints during split-belt walking, as well as medio-lateral ground reaction forces (ML-GRF). We did not observe alterations in the frontal mechanics produced during early or late adaptation of split-belt walking when compared to conditions where the belts moved together. We did observe that ML-GRF and hip moment impulse of the fast limb increased over time with adaptation to split-belt walking. These results suggest this modality may provide a unique therapy for individuals with gait pathologies, impairments, or compensation(s).

  13. Preferred gait and walk-run transition speeds in ostriches measured using GPS-IMU sensors.

    PubMed

    Daley, Monica A; Channon, Anthony J; Nolan, Grant S; Hall, Jade

    2016-10-15

    The ostrich (Struthio camelus) is widely appreciated as a fast and agile bipedal athlete, and is a useful comparative bipedal model for human locomotion. Here, we used GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and developed a quantitative method for distinguishing walking and running using accelerometry. We compared freely selected gait-speed distributions with previous laboratory measures of gait dynamics and energetics. We also measured the walk-run and run-walk transition speeds and compared them with those reported for humans. We found that ostriches prefer to walk remarkably slowly, with a narrow walking speed distribution consistent with minimizing cost of transport (CoT) according to a rigid-legged walking model. The dimensionless speeds of the walk-run and run-walk transitions are slower than those observed in humans. Unlike humans, ostriches transition to a run well below the mechanical limit necessitating an aerial phase, as predicted by a compass-gait walking model. When running, ostriches use a broad speed distribution, consistent with previous observations that ostriches are relatively economical runners and have a flat curve for CoT against speed. In contrast, horses exhibit U-shaped curves for CoT against speed, with a narrow speed range within each gait for minimizing CoT. Overall, the gait dynamics of ostriches moving freely over natural terrain are consistent with previous lab-based measures of locomotion. Nonetheless, ostriches, like humans, exhibit a gait-transition hysteresis that is not explained by steady-state locomotor dynamics and energetics. Further study is required to understand the dynamics of gait transitions. © 2016. Published by The Company of Biologists Ltd.

  14. Gait Evaluation of Overground Walking and Treadmill Walking Using Compass-Type Walking Model

    NASA Astrophysics Data System (ADS)

    Nagata, Yousuke; Yamamoto, Masayoshi; Funabiki, Shigeyuki

    A treadmill is a useful apparatus for the gait training and evaluation. However, many differences are reported between treadmill and overground walking. Experimental comparisons of the muscle activity of the leg and the heart rate have been carried out. However, the dynamic comparison has not been performed. The dynamic evaluation of the overground walking and the treadmill walking using a compass-type walking model (CTWM) which is a simple bipedal walking model, then their comparison is discussed. It is confirmed that the walking simulation using the CTWM can simulate the difference of that walk, it is clarified that there are the differences of the kick impulse on the ground and the turning impulse of the foot to the variation of the belt speed and then differences are the main factor of two walking.

  15. Torque-stiffness-controlled dynamic walking with central pattern generators.

    PubMed

    Huang, Yan; Vanderborght, Bram; Van Ham, Ronald; Wang, Qining

    2014-12-01

    Walking behavior is modulated by controlling joint torques in most existing passivity-based bipeds. Controlled Passive Walking with adaptable stiffness exhibits controllable natural motions and energy efficient gaits. In this paper, we propose torque-stiffness-controlled dynamic bipedal walking, which extends the concept of Controlled Passive Walking by introducing structured control parameters and a bio-inspired control method with central pattern generators. The proposed walking paradigm is beneficial in clarifying the respective effects of the external actuation and the internal natural dynamics. We present a seven-link biped model to validate the presented walking. Effects of joint torque and joint stiffness on gait selection, walking performance and walking pattern transitions are studied in simulations. The work in this paper develops a new solution of motion control of bipedal robots with adaptable stiffness and provides insights of efficient and sophisticated walking gaits of humans.

  16. Froude and the contribution of naval architecture to our understanding of bipedal locomotion.

    PubMed

    Vaughan, Christopher L; O'Malley, Mark J

    2005-04-01

    It is fascinating to think that the ideas of two 19th century naval architects could offer useful insights for 21st century scientists contemplating the exploration of our planetary system or monitoring the long-term effects of a neurosurgical procedure on gait. The Froude number, defined as Fr = v2/gL, where v is velocity, g is gravitational acceleration and L is a characteristic linear dimension (such as leg length), has found widespread application in the biomechanics of bipedal locomotion. This review of two parameters, Fr and dimensionless velocity beta = (Fr)1/2, that have served as the criterion for dynamic similarity, has been arranged in two parts: (I) historical development, including the contributions by William Froude and his son Edmund, two ship designers who lived more than 130 years ago, the classic insights of D'Arcy Wentworth Thompson who, in his magnum opus On Growth and Form, espoused the connection between mathematics and biology, and the pioneering efforts of Robert McNeill Alexander, who popularised the application of Fr to animal locomotion; and (II) selected applications, including a comparison of walking for people of different heights, exploring the effects of different gravitational fields on human locomotion, establishing the impact of pathology and the benefits of treatment, and understanding the walking patterns of bipedal robots. Although not all applications of Fr to locomotion have been covered, the review offers an important historical context for all researchers of bipedal gait, and extends the idea of dimensionless scaling of gait parameters.

  17. Obesity does not increase External Mechanical Work per kilogram body mass during Walking

    PubMed Central

    Browning, Raymond C.; McGowan, Craig P.; Kram, Rodger

    2009-01-01

    Walking is the most common type of physical activity prescribed for the treatment of obesity. The net metabolic rate during level walking (Watts/kg) is ~10% greater in obese vs. normal weight adults. External mechanical work (Wext) is one of the primary determinants of the metabolic cost of walking, but the effects of obesity on Wext have not been clearly established. The purpose of this study was to compare Wext between obese and normal weight adults across a range of walking speeds. We hypothesized that Wext (J/step) would be greater in obese adults but Wext normalized to body mass would be similar in obese and normal weight adults. We collected right leg three-dimensional ground reaction forces (GRF) while twenty adults (10 obese, BMI=35.6 kg/m2 and 10 normal weight, BMI=22.1 kg/m2) walked on a level, dual-belt force measuring treadmill at six speeds (0.50–1.75 m/s). We used the individual limb method (ILM) to calculate external work done on the center of mass. Absolute Wext (J/step) was greater in obese vs. normal weight adults at each walking speed, but relative Wext (J/step/kg) was similar between the groups. Step frequencies were not different. These results suggest that Wext is not responsible for the greater metabolic cost of walking (W/kg) in moderately obese adults. PMID:19646701

  18. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation

    PubMed Central

    Gruss, Laura Tobias; Schmitt, Daniel

    2015-01-01

    The fossil record of the human pelvis reveals the selective priorities acting on hominin anatomy at different points in our evolutionary history, during which mechanical requirements for locomotion, childbirth and thermoregulation often conflicted. In our earliest upright ancestors, fundamental alterations of the pelvis compared with non-human primates facilitated bipedal walking. Further changes early in hominin evolution produced a platypelloid birth canal in a pelvis that was wide overall, with flaring ilia. This pelvic form was maintained over 3–4 Myr with only moderate changes in response to greater habitat diversity, changes in locomotor behaviour and increases in brain size. It was not until Homo sapiens evolved in Africa and the Middle East 200 000 years ago that the narrow anatomically modern pelvis with a more circular birth canal emerged. This major change appears to reflect selective pressures for further increases in neonatal brain size and for a narrow body shape associated with heat dissipation in warm environments. The advent of the modern birth canal, the shape and alignment of which require fetal rotation during birth, allowed the earliest members of our species to deal obstetrically with increases in encephalization while maintaining a narrow body to meet thermoregulatory demands and enhance locomotor performance. PMID:25602067

  19. Skipping vs. running as the bipedal gait of choice in hypogravity.

    PubMed

    Pavei, Gaspare; Biancardi, Carlo M; Minetti, Alberto E

    2015-07-01

    Hypogravity challenges bipedal locomotion in its common forms. However, as previously theoretically and empirically suggested, humans can rely on "skipping," a less common gait available as a functional analog (perhaps a vestigium) of quadrupedal gallop, to confidently move when gravity is much lower than on Earth. We set up a 17-m-tall cavaedium (skylight shaft) with a bungee rubber body-suspension system and a treadmill to investigate the metabolic cost and the biomechanics of low-gravity (Mars, Moon) locomotion. Although skipping is never more metabolically economical than running, the difference becomes marginal at lunar gravities, with both bouncing gaits approaching values of walking on Earth (cost ≈ 2 J · kg(-1)· m(-1)). Nonmetabolic factors may thus be allowed to dominate the choice of skipping on the Moon. On the basis of center of pressure measurements and body segments kinetics, we can speculate that these factors may include a further reduction of mechanical work to move the limbs when wearing space suits and a more effective motor control during the ground (regoliths)-boot interaction. Copyright © 2015 the American Physiological Society.

  20. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation.

    PubMed

    Gruss, Laura Tobias; Schmitt, Daniel

    2015-03-05

    The fossil record of the human pelvis reveals the selective priorities acting on hominin anatomy at different points in our evolutionary history, during which mechanical requirements for locomotion, childbirth and thermoregulation often conflicted. In our earliest upright ancestors, fundamental alterations of the pelvis compared with non-human primates facilitated bipedal walking. Further changes early in hominin evolution produced a platypelloid birth canal in a pelvis that was wide overall, with flaring ilia. This pelvic form was maintained over 3-4 Myr with only moderate changes in response to greater habitat diversity, changes in locomotor behaviour and increases in brain size. It was not until Homo sapiens evolved in Africa and the Middle East 200 000 years ago that the narrow anatomically modern pelvis with a more circular birth canal emerged. This major change appears to reflect selective pressures for further increases in neonatal brain size and for a narrow body shape associated with heat dissipation in warm environments. The advent of the modern birth canal, the shape and alignment of which require fetal rotation during birth, allowed the earliest members of our species to deal obstetrically with increases in encephalization while maintaining a narrow body to meet thermoregulatory demands and enhance locomotor performance.

  1. The transition between walking and running in humans: metabolic and mechanical aspects at different gradients.

    PubMed

    Minetti, A E; Ardigò, L P; Saibene, F

    1994-03-01

    Five subjects walked and ran at overlapping speeds and different gradients on a motorized treadmill. At each gradient the speed was obtained at which walking and running have the same metabolic cost (Sm) and the speed of spontaneous (Ss) transition between the two gaits was measured. Ss was found to be statistically lower than Sm at all gradients, the difference being in the range of 0.5-0.9 km h-1. The motion analysis of walking reveals that at all gradients and at increasing speed: (1) the percentage of recovery, an index of mechanical energy saving related to the pendulum-like characteristic of walking, decreases; (2) the lower limb spread reaches a limit in walking; and consequently (3) both the stride frequency and the internal mechanical work, due to limb acceleration in relation to the body centre of mass, increase much more in walking than in running. Switching to a run, although implying a higher frequency, makes the internal work decrease as a result of the lower limb spread. In this paper several influences, such as the 'ratings of perceived exertion' (RPE), on the choice of beginning to run when it is more economical to walk, are discussed. A tentative hypothesis on the determinants of Ss, which is emphasized to be a speed which has to be studied in detail but is generally avoided in locomotion, is based on a comfort criterion from peripheric afferences and is reflected by the fact that at Ss a running stride costs as much as a walking stride.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. A wrist-walker exhibiting no "Uner Tan Syndrome": a theory for possible mechanisms of human devolution toward the atavistic walking patterns.

    PubMed

    Tan, Uner

    2007-01-01

    transition from quadrupedality to bipedality. That is, the activity of the philogenetically youngest supraspinal centers for bipedal walking responsible for suppression of the older supraspinal centers for quadrupedal gait may be interrupted at the atavistic level due to genetic and/or environmental factors. Consequently, it is assumed that these individuals prefer their natural wrist-walking to move around more quickly and efficiently.

  3. Metabolic cost, mechanical work, and efficiency during normal walking in obese and normal-weight children.

    PubMed

    Huang, Liang; Chen, Peijie; Zhuang, Jie; Walt, Sharon

    2013-12-01

    This study aimed to investigate the influence of childhood obesity on energetic cost during normal walking and to determine if obese children choose a walking strategy optimizing their gait pattern. Sixteen obese children with no functional abnormalities were matched by age and gender with 16 normal-weight children. All participants were asked to walk along a nearly circular track 30 m in length at a self-selected speed. Spatiotemporal data, kinematics, and ground reaction force were collected during walking using a three-dimensional motion analysis system. Metabolic cost was collected by a portable gas analyzer simultaneously. The mechanical energy expenditure (MEE) was 72.7% higher in obese children than in normal-weight children. The net metabolic cost was 65.7% higher in obese children. No difference was found in the metabolic rate (J x kg(-1) x m(-1)), normalized MEE (J x kg(-1) x m(-1)) and mechanical efficiency between the obese and normal-weight groups. The obese children walked with a 0.15 m/s slower walking speed, 10.0% shorter cadence, and 30.9% longer double-support phase compared with normal-weight children. In addition, no differences were found in the mediolateral and vertical body center of mass displacement. Body mass played a dominant role in the total metabolic and mechanical cost per stride. Obese children may adopt a walking strategy to avoid an increase in the metabolic cost and the mechanical work required to move their excess body mass.

  4. Decoding bipedal locomotion from the rat sensorimotor cortex

    NASA Astrophysics Data System (ADS)

    Rigosa, J.; Panarese, A.; Dominici, N.; Friedli, L.; van den Brand, R.; Carpaneto, J.; DiGiovanna, J.; Courtine, G.; Micera, S.

    2015-10-01

    Objective. Decoding forelimb movements from the firing activity of cortical neurons has been interfaced with robotic and prosthetic systems to replace lost upper limb functions in humans. Despite the potential of this approach to improve locomotion and facilitate gait rehabilitation, decoding lower limb movement from the motor cortex has received comparatively little attention. Here, we performed experiments to identify the type and amount of information that can be decoded from neuronal ensemble activity in the hindlimb area of the rat motor cortex during bipedal locomotor tasks. Approach. Rats were trained to stand, step on a treadmill, walk overground and climb staircases in a bipedal posture. To impose this gait, the rats were secured in a robotic interface that provided support against the direction of gravity and in the mediolateral direction, but behaved transparently in the forward direction. After completion of training, rats were chronically implanted with a micro-wire array spanning the left hindlimb motor cortex to record single and multi-unit activity, and bipolar electrodes into 10 muscles of the right hindlimb to monitor electromyographic signals. Whole-body kinematics, muscle activity, and neural signals were simultaneously recorded during execution of the trained tasks over multiple days of testing. Hindlimb kinematics, muscle activity, gait phases, and locomotor tasks were decoded using offline classification algorithms. Main results. We found that the stance and swing phases of gait and the locomotor tasks were detected with accuracies as robust as 90% in all rats. Decoded hindlimb kinematics and muscle activity exhibited a larger variability across rats and tasks. Significance. Our study shows that the rodent motor cortex contains useful information for lower limb neuroprosthetic development. However, brain-machine interfaces estimating gait phases or locomotor behaviors, instead of continuous variables such as limb joint positions or speeds

  5. Biomechanics of running indicates endothermy in bipedal dinosaurs.

    PubMed

    Pontzer, Herman; Allen, Vivian; Hutchinson, John R

    2009-11-11

    One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals. Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary. Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced "avian" lung structure and high locomotor costs.

  6. Reading from a Head-Fixed Display during Walking: Adverse Effects of Gaze Stabilization Mechanisms.

    PubMed

    Borg, Olivier; Casanova, Remy; Bootsma, Reinoud J

    2015-01-01

    Reading performance during standing and walking was assessed for information presented on earth-fixed and head-fixed displays by determining the minimal duration during which a numerical time stimulus needed to be presented for 50% correct naming answers. Reading from the earth-fixed display was comparable during standing and walking, with optimal performance being attained for visual character sizes in the range of 0.2° to 1°. Reading from the head-fixed display was impaired for small (0.2-0.3°) and large (5°) visual character sizes, especially during walking. Analysis of head and eye movements demonstrated that retinal slip was larger during walking than during standing, but remained within the functional acuity range when reading from the earth-fixed display. The detrimental effects on performance of reading from the head-fixed display during walking could be attributed to loss of acuity resulting from large retinal slip. Because walking activated the angular vestibulo-ocular reflex, the resulting compensatory eye movements acted to stabilize gaze on the information presented on the earth-fixed display but destabilized gaze from the information presented on the head-fixed display. We conclude that the gaze stabilization mechanisms that normally allow visual performance to be maintained during physical activity adversely affect reading performance when the information is presented on a display attached to the head.

  7. Reading from a Head-Fixed Display during Walking: Adverse Effects of Gaze Stabilization Mechanisms

    PubMed Central

    Borg, Olivier; Casanova, Remy; Bootsma, Reinoud J.

    2015-01-01

    Reading performance during standing and walking was assessed for information presented on earth-fixed and head-fixed displays by determining the minimal duration during which a numerical time stimulus needed to be presented for 50% correct naming answers. Reading from the earth-fixed display was comparable during standing and walking, with optimal performance being attained for visual character sizes in the range of 0.2° to 1°. Reading from the head-fixed display was impaired for small (0.2-0.3°) and large (5°) visual character sizes, especially during walking. Analysis of head and eye movements demonstrated that retinal slip was larger during walking than during standing, but remained within the functional acuity range when reading from the earth-fixed display. The detrimental effects on performance of reading from the head-fixed display during walking could be attributed to loss of acuity resulting from large retinal slip. Because walking activated the angular vestibulo-ocular reflex, the resulting compensatory eye movements acted to stabilize gaze on the information presented on the earth-fixed display but destabilized gaze from the information presented on the head-fixed display. We conclude that the gaze stabilization mechanisms that normally allow visual performance to be maintained during physical activity adversely affect reading performance when the information is presented on a display attached to the head. PMID:26053622

  8. Robots in human biomechanics--a study on ankle push-off in walking.

    PubMed

    Renjewski, Daniel; Seyfarth, André

    2012-09-01

    In biomechanics, explanatory template models are used to identify the basic mechanisms of human locomotion. However, model predictions often lack verification in a realistic environment. We present a method that uses template model mechanics as a blueprint for a bipedal robot and a corresponding computer simulation. The hypotheses derived from template model studies concerning the function of heel-off in walking are analysed and discrepancies between the template model and its real-world anchor are pointed out. Neither extending the ground clearance of the swinging leg nor an impact reduction at touch-down as an effect of heel lifting was supported by the experiments. To confirm the relevance of the experimental findings, a comparison of robot data to human walking data is discussed and we speculate on an alternative explanation of heel-off in human walking, i.e. that the push-off powers the following leg swing.

  9. Giant Galapagos tortoises walk without inverted pendulum mechanical-energy exchange.

    PubMed

    Zani, Peter A; Gottschall, Jinger S; Kram, Rodger

    2005-04-01

    Animals must perform mechanical work during walking, but most conserve substantial mechanical energy via an inverted-pendulum-like mechanism of energy recovery in which fluctuations of kinetic energy (KE) and gravitational potential energy (GPE) are of similar magnitude and 180 degrees out of phase. The greatest energy recovery typically occurs at intermediate speeds. Tortoises are known for their slow speeds, which we anticipated would lead to small fluctuations in KE. To have an effective exchange of mechanical energy using the inverted-pendulum mechanism, tortoises would need to walk with only small changes in GPE corresponding to vertical center-of-mass (COM) fluctuations of < 0.5 mm. Thus, we hypothesized that giant Galapagos tortoises would not conserve substantial mechanical energy using the inverted-pendulum mechanism. We studied five adult giant Galapagos tortoises Geochelone elephantopus (mean mass=142 kg; range= 103-196 kg). Walking speed was extremely slow (0.16+/-0.052 m s(-1); mean +/- 1 s.d.). The fluctuations in kinetic energy (8.1+/-3.98 J stride(-1)) were only one-third as large as the fluctuations in gravitational potential energy (22.7+/-8.04 J stride(-1)). In addition, these energies fluctuated nearly randomly and were only sporadically out of phase. Because of the dissimilar amplitudes and inconsistent phase relationships of these energies, tortoises conserved little mechanical energy during steady walking, recovering only 29.8+/-3.77% of the mechanical energy (range=13-52%). Thus, giant Galapagos tortoises do not utilize effectively an inverted-pendulum mechanism of energy conservation. Nonetheless, the mass-specific external mechanical work required per distance (0.41+/-0.092 J kg(-1) m(-1)) was not different from most other legged animals. Other turtle species use less than half as much metabolic energy to walk as other terrestrial animals of similar mass. It is not yet known if Galapagos tortoises are economical walkers. Nevertheless

  10. Gradual mechanics-dependent adaptation of medial gastrocnemius activity during human walking

    PubMed Central

    Wellinghoff, Molly A.; Bunchman, Alison M.

    2013-01-01

    While performing a simple bouncing task, humans modify their preferred movement period and pattern of plantarflexor activity in response to changes in system mechanics. Over time, the preferred movement pattern gradually adapts toward the resonant frequency. The purpose of the present experiments was to determine whether humans undergo a similar process of gradually adapting their stride period and plantarflexor activity after a change in mechanical demand while walking. Participants walked on a treadmill while we measured stride period and plantarflexor activity (medial gastrocnemius and soleus). Plantarflexor activity during stance was divided into a storage phase (30–65% stance) and a return phase (65–100% stance) based on when the Achilles tendon has previously been shown to store and return mechanical energy. Participants walked either on constant inclines (0%, 1%, 5%, 9%) or on a variable incline (0–1%) for which they were unaware of the incline changes. For variable-incline trials, participants walked under both single-task and dual-task conditions in order to vary the cognitive load. Both stride period and plantarflexor activity increased at steeper inclines. During single-task walking, small changes in incline were followed by gradual adaptation of storage-phase medial gastrocnemius activity. However, this adaptation was not present during dual-task walking, indicating some level of cognitive involvement. The observed adaptation may be the result of using afferent feedback in order to optimize the contractile conditions of the plantarflexors during the stance phase. Such adaptation could serve to improve metabolic economy but may be limited in clinical populations with disrupted proprioception. PMID:24335207

  11. Gradual mechanics-dependent adaptation of medial gastrocnemius activity during human walking.

    PubMed

    Wellinghoff, Molly A; Bunchman, Alison M; Dean, Jesse C

    2014-03-01

    While performing a simple bouncing task, humans modify their preferred movement period and pattern of plantarflexor activity in response to changes in system mechanics. Over time, the preferred movement pattern gradually adapts toward the resonant frequency. The purpose of the present experiments was to determine whether humans undergo a similar process of gradually adapting their stride period and plantarflexor activity after a change in mechanical demand while walking. Participants walked on a treadmill while we measured stride period and plantarflexor activity (medial gastrocnemius and soleus). Plantarflexor activity during stance was divided into a storage phase (30-65% stance) and a return phase (65-100% stance) based on when the Achilles tendon has previously been shown to store and return mechanical energy. Participants walked either on constant inclines (0%, 1%, 5%, 9%) or on a variable incline (0-1%) for which they were unaware of the incline changes. For variable-incline trials, participants walked under both single-task and dual-task conditions in order to vary the cognitive load. Both stride period and plantarflexor activity increased at steeper inclines. During single-task walking, small changes in incline were followed by gradual adaptation of storage-phase medial gastrocnemius activity. However, this adaptation was not present during dual-task walking, indicating some level of cognitive involvement. The observed adaptation may be the result of using afferent feedback in order to optimize the contractile conditions of the plantarflexors during the stance phase. Such adaptation could serve to improve metabolic economy but may be limited in clinical populations with disrupted proprioception.

  12. Mechanical energy assessment of adult with Down syndrome during walking with obstacle avoidance.

    PubMed

    Salami, Firooz; Vimercati, Sara Laura; Rigoldi, Chiara; Taebi, Amirtaha; Albertini, Giorgio; Galli, Manuela

    2014-08-01

    The aim of this study is analyzing the differences between plane walking and stepping over an obstacle for two groups of healthy people and people with Down syndrome and then, evaluating the movement efficiency between the groups by comprising of their mechanical energy exchanges. 39 adults including two groups of 21 people with Down syndrome (age: 21.6 ± 7 years) and 18 healthy people (age: 25.1 ± 2.4 years) participated in this research. The test has been done in two conditions, first in plane walking and second in walking with an obstacle (10% of the subject's height). The gait data were acquired using quantitative movement analysis, composed of an optoelectronic system (Elite2002, BTS) with eight infrared cameras. Mechanical energy exchanges are computed by dedicated software and finally the data including spatiotemporal parameters, mechanical energy parameters and energy recovery of gait cycle are analyzed by statistical software to find significant differences. Regards to spatiotemporal parameters velocity and step length are lower in people with Down syndrome. Mechanical energy parameters particularly energy recovery does not change from healthy people to people with Down syndrome. However, there are some differences in inter-group through plane walking to obstacle avoidance and it means people with Down syndrome probably use their residual abilities in the most efficient way to achieve the main goal of an efficient energy recovery.

  13. The energetic costs of load-carrying and the evolution of bipedalism.

    PubMed

    Watson, J C; Payne, R C; Chamberlain, A T; Jones, R K; Sellers, W I

    2008-05-01

    The evolution of habitual bipedalism is still a fundamental yet unsolved question for paleoanthropologists, and carrying is popular as an explanation for both the early adoption of upright walking and as a positive selection pressure once a terrestrial lifestyle had been adopted. However, to support or reject any hypothesis that suggests carrying efficiency was an important selective pressure, we need quantitative data on the costs of different forms of carrying behavior, especially infant-carrying since reduction in the grasping capabilities of the foot would have prevented infants from clinging on for long durations. In this study, we tested the hypothesis that the mode of load carriage influences the energetic cost of locomotion. Oxygen consumption was measured in seven female participants walking at a constant speed while carrying four different 10-kg loads (a weighted vest, 5-kg dumbbells carried in each hand, a mannequin infant carried on one hip, and a 10-kg dumbbell carried in a single hand). Oxygen consumption was also measured during unloaded standing and unloaded walking. The results show that the weighted vest requires the least amount of energy of the four types of carrying and that, for this condition, humans are as efficient as mammals in general. The balanced load was carried with approximately the predicted energy cost. However, the asymmetrical conditions were considerably less efficient, indicating that, unless infant-carrying was the adaptive response to a strong environmental selection pressure, this behavior is unlikely to have been the precursor to the evolution of bipedalism.

  14. Paleoanthropology: When hobbits (slowly) walked the earth.

    PubMed

    Culotta, Elizabeth

    2008-04-25

    At the recent American Association of Physical Anthropology meetings, a researcher described the foot bones of an 18,000-year-old Indonesian skeleton known as the "hobbit." The tiny hominin would not have walked like we do, he said, and may offer "a window into a primitive bipedal foot."

  15. Gait-specific energetics contributes to economical walking and running in emus and ostriches

    PubMed Central

    Watson, Rebecca R.; Rubenson, Jonas; Coder, Lisa; Hoyt, Donald F.; Propert, Matthew W. G.; Marsh, Richard L.

    2011-01-01

    A widely held assumption is that metabolic rate (Ėmet) during legged locomotion is linked to the mechanics of different gaits and this linkage helps explain the preferred speeds of animals in nature. However, despite several prominent exceptions, Ėmet of walking and running vertebrates has been nearly uniformly characterized as increasing linearly with speed across all gaits. This description of locomotor energetics does not predict energetically optimal speeds for minimal cost of transport (Ecot). We tested whether large bipedal ratite birds (emus and ostriches) have gait-specific energetics during walking and running similar to those found in humans. We found that during locomotion, emus showed a curvilinear relationship between Ėmet and speed during walking, and both emus and ostriches demonstrated an abrupt change in the slope of Ėmet versus speed at the gait transition with a linear increase during running. Similar to human locomotion, the minimum net Ecot calculated after subtracting resting metabolism was lower in walking than in running in both species. However, the difference in net Ecot between walking and running was less than is found in humans because of a greater change in the slope of Ėmet versus speed at the gait transition, which lowers the cost of running for the avian bipeds. For emus, we also show that animals moving freely overground avoid a range of speeds surrounding the gait-transition speed within which the Ecot is large. These data suggest that deviations from a linear relation of metabolic rate and speed and variations in transport costs with speed are more widespread than is often assumed, and provide new evidence that locomotor energetics influences the choice of speed in bipedal animals. The low cost of transport for walking is probably ecologically important for emus and ostriches because they spend the majority of their active day walking, and thus the energy used for locomotion is a large part of their daily energy budget. PMID

  16. Biomechanical walking mechanisms underlying the metabolic reduction caused by an autonomous exoskeleton.

    PubMed

    Mooney, Luke M; Herr, Hugh M

    2016-01-28

    Ankle exoskeletons can now reduce the metabolic cost of walking in humans without leg disability, but the biomechanical mechanisms that underlie this augmentation are not fully understood. In this study, we analyze the energetics and lower limb mechanics of human study participants walking with and without an active autonomous ankle exoskeleton previously shown to reduce the metabolic cost of walking. We measured the metabolic, kinetic and kinematic effects of wearing a battery powered bilateral ankle exoskeleton. Six participants walked on a level treadmill at 1.4 m/s under three conditions: exoskeleton not worn, exoskeleton worn in a powered-on state, and exoskeleton worn in a powered-off state. Metabolic rates were measured with a portable pulmonary gas exchange unit, body marker positions with a motion capture system, and ground reaction forces with a force-plate instrumented treadmill. Inverse dynamics were then used to estimate ankle, knee and hip torques and mechanical powers. The active ankle exoskeleton provided a mean positive power of 0.105 ± 0.008 W/kg per leg during the push-off region of stance phase. The net metabolic cost of walking with the active exoskeleton (3.28 ± 0.10 W/kg) was an 11 ± 4 % (p = 0.019) reduction compared to the cost of walking without the exoskeleton (3.71 ± 0.14 W/kg). Wearing the ankle exoskeleton significantly reduced the mean positive power of the ankle joint by 0.033 ± 0.006 W/kg (p = 0.007), the knee joint by 0.042 ± 0.015 W/kg (p = 0.020), and the hip joint by 0.034 ± 0.009 W/kg (p = 0.006). This study shows that the ankle exoskeleton does not exclusively reduce positive mechanical power at the ankle joint, but also mitigates positive power at the knee and hip. Furthermore, the active ankle exoskeleton did not simply replace biological ankle function in walking, but rather augmented the total (biological + exoskeletal) ankle moment and power. This study

  17. The effect of walking speed on muscle function and mechanical energetics.

    PubMed

    Neptune, Richard R; Sasaki, Kotaro; Kautz, Steven A

    2008-07-01

    Modulating speed over a large range is important in walking, yet understanding how the neuromotor patterns adapt to the changing energetic demands of different speeds is not well understood. The purpose of this study was to identify functional and energetic adaptations in individual muscles in response to walking at faster steady-state speeds using muscle-actuated forward dynamics simulations. The simulation data were invariant with speed as to whether muscles contributed to trunk support, forward propulsion or leg swing. Trunk support (vertical acceleration) was provided primarily by the hip and knee extensors in early stance and the plantar flexors in late stance, while trunk propulsion (horizontal acceleration) was provided primarily by the soleus and rectus femoris in late stance, and these muscle contributions all systematically increased with speed. The results also highlighted the importance of initiating and controlling leg swing as there was a dramatic increase at the higher walking speeds in iliopsoas muscle work to accelerate the leg in pre- and early swing, and an increase in the biarticular hamstring muscle work to decelerate the leg in late swing. In addition, walking near self-selected speeds (1.2m/s) improves the utilization of elastic energy storage and recovery in the uniarticular ankle plantar flexors and reduces negative fiber work, when compared to faster or slower speeds. These results provide important insight into the neuromotor mechanisms underlying speed regulation in walking and provide the foundation on which to investigate the influence of walking speed on various neuromotor measures of interest in pathological populations.

  18. Mechanical and energetic consequences of reduced ankle plantar-flexion in human walking

    PubMed Central

    Huang, Tzu-wei P.; Shorter, Kenneth A.; Adamczyk, Peter G.; Kuo, Arthur D.

    2015-01-01

    ABSTRACT The human ankle produces a large burst of ‘push-off’ mechanical power late in the stance phase of walking, reduction of which leads to considerably poorer energy economy. It is, however, uncertain whether the energetic penalty results from poorer efficiency when the other leg joints substitute for the ankle's push-off work, or from a higher overall demand for work due to some fundamental feature of push-off. Here, we show that greater metabolic energy expenditure is indeed explained by a greater demand for work. This is predicted by a simple model of walking on pendulum-like legs, because proper push-off reduces collision losses from the leading leg. We tested this by experimentally restricting ankle push-off bilaterally in healthy adults (N=8) walking on a treadmill at 1.4 m s−1, using ankle–foot orthoses with steel cables limiting motion. These produced up to ∼50% reduction in ankle push-off power and work, resulting in up to ∼50% greater net metabolic power expenditure to walk at the same speed. For each 1 J reduction in ankle work, we observed 0.6 J more dissipative collision work by the other leg, 1.3 J more positive work from the leg joints overall, and 3.94 J more metabolic energy expended. Loss of ankle push-off required more positive work elsewhere to maintain walking speed; this additional work was performed by the knee, apparently at reasonably high efficiency. Ankle push-off may contribute to walking economy by reducing dissipative collision losses and thus overall work demand. PMID:26385330

  19. The effect of walking speed on muscle function and mechanical energetics

    PubMed Central

    Neptune, Richard R.; Sasaki, Kotaro; Kautz, Steven A.

    2008-01-01

    Modulating speed over a large range is important in walking, yet understanding how the neuromotor patterns adapt to the changing energetic demands of different speeds is not well understood. The purpose of this study was to identify functional and energetic adaptations in individual muscles in response to walking at faster steady-state speeds using muscle-actuated forward dynamics simulations. The simulation data were invariant with speed as to whether muscles contributed to trunk support, forward propulsion or leg swing. Trunk support (vertical acceleration) was provided primarily by the hip and knee extensors in early stance and the plantar flexors in late stance, while trunk propulsion (horizontal acceleration) was provided primarily by the soleus and rectus femoris in late stance, and these muscle contributions all systematically increased with speed. The results also highlighted the importance of initiating and controlling leg swing as there was a dramatic increase at the higher walking speeds in iliopsoas muscle work to accelerate the leg in pre- and early swing, and an increase in the biarticular hamstring muscle work to decelerate the leg in late swing. In addition, walking near self-selected speeds (1.2 m/s) improves the utilization of elastic energy storage and recovery in the uniarticular ankle plantar flexors and reduces negative fiber work, when compared to faster or slower speeds. These results provide important insight into the neuromotor mechanisms underlying speed regulation in walking and provide the foundation on which to investigate the influence of walking speed on various neuromotor measures of interest in pathological populations. PMID:18158246

  20. Soft Tissue Deformations Contribute to the Mechanics of Walking in Obese Adults

    PubMed Central

    Fu, Xiao-Yu; Zelik, Karl E.; Board, Wayne J.; Browning, Raymond C.; Kuo, Arthur D.

    2014-01-01

    Obesity not only adds to the mass that must be carried during walking, but also changes body composition. Although extra mass causes roughly proportional increases in musculoskeletal loading, less well understood is the effect of relatively soft and mechanically compliant adipose tissue. Purpose To estimate the work performed by soft tissue deformations during walking. The soft tissue would be expected to experience damped oscillations, particularly from high force transients following heel strike, and could potentially change the mechanical work demands for walking. Method We analyzed treadmill walking data at 1.25 m/s for 11 obese (BMI > 30 kg/m2) and 9 non-obese (BMI < 30 kg/m2) adults. The soft tissue work was quantified with a method that compares the work performed by lower extremity joints as derived using assumptions of rigid body segments, with that estimated without rigid body assumptions. Results Relative to body mass, obese and non-obese individuals perform similar amounts of mechanical work. But negative work performed by soft tissues was significantly greater in obese individuals (p= 0.0102), equivalent to about 0.36 J/kg vs. 0.27 J/kg in non-obese individuals. The negative (dissipative) work by soft tissues occurred mainly after heel strike, and for obese individuals was comparable in magnitude to the total negative work from all of the joints combined (0.34 J/kg vs. 0.33 J/kg for obese and non-obese adults, respectively). Although the joints performed a relatively similar amount of work overall, obese individuals performed less negative work actively at the knee. Conclusion The greater proportion of soft tissues in obese individuals results in substantial changes in the amount, location, and timing of work, and may also impact metabolic energy expenditure during walking. PMID:25380475

  1. Foot mechanics during the first six years of independent walking.

    PubMed

    Samson, William; Dohin, Bruno; Desroches, Guillaume; Chaverot, Jean-Luc; Dumas, Raphaël; Cheze, Laurence

    2011-04-29

    Recognition of the changes during gait that occur normally as a part of growth is essential to prevent mislabeling those changes from adult gait as evidence of gait pathology. Currently, in the literature, the definition of a mature age for ankle joint dynamics is controversial (i.e., between 5 and 10 years). Moreover, the mature age of the metatarsophalangeal (MP) joint, which is essential for the functioning of the foot, has not been defined in the literature. Thus, the objective of the present study explored foot mechanics (ankle and MP joints) in young children to define a mature age of foot function. Forty-two healthy children between 1 and 6 years of age and eight adults were measured during gait. The ground reaction force (GRF), the MP and ankle joint angles, moments, powers, and 3D angles between the joint moment and the joint angular velocity vectors (3D angle α(M.ω)) were processed and compared between four age groups (2, 3.5, 5 and adults). Based on statistical analysis, the MP joint biomechanical parameters were similar between children (older than 2 years) and adults, hinting at a quick maturation of this joint mechanics. The ankle joint parameters and the GRFs (except for the frontal plane) showed an adult-like pattern in 5-year-old children. Some ankle joint parameters, such as the joint power and the 3D angle α(M.ω) still evolved significantly until 3.5 years. Based on these results, it would appear that foot maturation during gait is fully achieved at 5 years. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Mechanical and energetic consequences of rolling foot shape in human walking

    PubMed Central

    Adamczyk, Peter G.; Kuo, Arthur D.

    2013-01-01

    SUMMARY During human walking, the center of pressure under the foot progresses forward smoothly during each step, creating a wheel-like motion between the leg and the ground. This rolling motion might appear to aid walking economy, but the mechanisms that may lead to such a benefit are unclear, as the leg is not literally a wheel. We propose that there is indeed a benefit, but less from rolling than from smoother transitions between pendulum-like stance legs. The velocity of the body center of mass (COM) must be redirected in that transition, and a longer foot reduces the work required for the redirection. Here we develop a dynamic walking model that predicts different effects from altering foot length as opposed to foot radius, and test it by attaching rigid, arc-like foot bottoms to humans walking with fixed ankles. The model suggests that smooth rolling is relatively insensitive to arc radius, whereas work for the step-to-step transition decreases approximately quadratically with foot length. We measured the separate effects of arc-foot length and radius on COM velocity fluctuations, work performed by the legs and metabolic cost. Experimental data (N=8) show that foot length indeed has much greater effect on both the mechanical work of the step-to-step transition (23% variation, P=0.04) and the overall energetic cost of walking (6%, P=0.03) than foot radius (no significant effect, P>0.05). We found the minimum metabolic energy cost for an arc foot length of approximately 29% of leg length, roughly comparable to human foot length. Our results suggest that the foot's apparently wheel-like action derives less benefit from rolling per se than from reduced work to redirect the body COM. PMID:23580717

  3. A stability-based mechanism for hysteresis in the walk-trot transition in quadruped locomotion.

    PubMed

    Aoi, Shinya; Katayama, Daiki; Fujiki, Soichiro; Tomita, Nozomi; Funato, Tetsuro; Yamashita, Tsuyoshi; Senda, Kei; Tsuchiya, Kazuo

    2013-04-06

    Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk-trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk-trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics.

  4. Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs

    PubMed Central

    Pontzer, Herman; Allen, Vivian; Hutchinson, John R.

    2009-01-01

    Background One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals. Methodology/Principal Findings Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary. Conclusions/Significance Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced “avian” lung structure and high locomotor costs. PMID:19911059

  5. 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

    2017-08-15

    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.

  6. Dynamic stability of human walking in visually and mechanically destabilizing environments.

    PubMed

    McAndrew, Patricia M; Wilken, Jason M; Dingwell, Jonathan B

    2011-02-24

    Understanding how humans remain stable during challenging locomotor activities is critical to developing effective tests to diagnose patients with increased fall risk. This study determined if different continuous low-amplitude perturbations would induce specific measureable changes in measures of dynamic stability during walking. We applied continuous pseudo-random oscillations of either the visual scene or support surface in either the anterior-posterior or mediolateral directions to subjects walking in a virtual environment with speed-matched optic flow. Floquet multipliers and short-term local divergence exponents both increased (indicating greater instability) during perturbed walking. These responses were generally much stronger for body movements occurring in the same directions as the applied perturbations. Likewise, subjects were more sensitive to both visual and mechanical perturbations applied in the mediolateral direction than to those applied in the anterior-posterior direction, consistent with previous experiments and theoretical predictions. These responses were likewise consistent with subjects' anecdotal perceptions of which perturbation conditions were most challenging. Contrary to the Floquet multipliers and short-term local divergence exponents, which both increased, long-term local divergence exponents decreased during perturbed walking. However, this was consistent with specific changes in the mean log divergence curves, which indicated that subjects' movements reached their maximum local divergence limits more quickly during perturbed walking. Overall, the Floquet multipliers were less sensitive, but reflected greater specificity in their responses to the different perturbation conditions. Conversely, the short-term local divergence exponents exhibited less specificity in their responses, but were more sensitive measures of instability in general. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. Stability of an underactuated bipedal gait.

    PubMed

    Mukherjee, S; Sangwan, V; Taneja, A; Seth, B

    2007-01-01

    A self-excited biped walking mechanism consisting of two legs that are connected in series at the hip joint through a servomotor is studied as a cyclic system with collisions. A torque proportional to angle between the shank of the swinging leg and the vertical is seen to sustain a gait. Each leg has a thigh and a shank connected at a passive knee joint that has a knee stopper restricting hyperextension similar to the human knee. A mathematical model for the dynamics of the system including the impact equations is used to analyse the stability of the system through examination of phase plane plots. Attractor lines along which the system approaches stability have been identified. A leg length for optimal stability has been identified. The biological basis for the proposed system has been identified by comparison with human gait.

  8. Muscle and prosthesis contributions to amputee walking mechanics: a modeling study.

    PubMed

    Silverman, Anne K; Neptune, Richard R

    2012-08-31

    Unilateral, below-knee amputees have altered gait mechanics, which can significantly affect their mobility. Below-knee amputees lose the functional use of the ankle muscles, which are critical during walking to provide body support, forward propulsion, leg-swing initiation and mediolateral balance. Thus, either muscles must compensate or the prosthesis must provide the functional tasks normally provided by the ankle muscles. Three-dimensional (3D) forward dynamics simulations of amputee and non-amputee walking were generated to identify muscle and prosthesis contributions to amputee walking mechanics, including the subtasks of body support, forward propulsion, leg-swing initiation and mediolateral balance. Results showed that the prosthesis provided body support in the absence of the ankle muscles. The prosthesis contributed to braking from early to mid-stance and propulsion in late stance. The prosthesis also functioned like the uniarticular soleus muscle by transferring energy from the residual leg to the trunk to provide trunk propulsion. The residual-leg vasti and rectus femoris reduced their contributions to braking in early stance, which mitigated braking from the prosthesis during this period. The prosthesis did not replace the function of the gastrocnemius, which normally generates energy to the leg to initiate swing. As a result, lower overall energy was delivered to the residual leg. The prosthesis also acted to accelerate the body laterally in the absence of the ankle muscles. These results provide further insight into muscle and prosthesis function in below-knee amputee walking and can help guide rehabilitation methods and device designs to improve amputee mobility. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Neuromusculoskeletal computer modeling and simulation of upright, straight-legged, bipedal locomotion of Australopithecus afarensis (A.L. 288-1).

    PubMed

    Nagano, Akinori; Umberger, Brian R; Marzke, Mary W; Gerritsen, Karin G M

    2005-01-01

    The skeleton of Australopithecus afarensis (A.L. 288-1, better known as "Lucy") is by far the most complete record of locomotor morphology of early hominids currently available. Even though researchers agree that the postcranial skeleton of Lucy shows morphological features indicative of bipedality, only a few studies have investigated Lucy's bipedal locomotion itself. Lucy's energy expenditure during locomotion has been the topic of much speculation, but has not been investigated, except for several estimates derived from experimental data collected on other animals. To gain further insights into how Lucy may have walked, we generated a full three-dimensional (3D) reconstruction and forward-dynamic simulation of upright bipedal locomotion of this ancient human ancestor. Laser-scanned 3D bone geometries were combined with state-of-the-art neuromusculoskeletal modeling and simulation techniques from computational biomechanics. A detailed full 3D neuromusculoskeletal model was developed that encompassed all major bones, joints (10), and muscles (52) of the lower extremity. A model of muscle force and heat production was used to actuate the musculoskeletal system, and to estimate total energy expenditure during locomotion. Neural activation profiles for each of the 52 muscles that produced a single step of locomotion, while at the same time minimizing the energy consumed per meter traveled, were searched through numerical optimization. The numerical optimization resulted in smooth locomotor kinematics, and the predicted energy expenditure was appropriate for upright bipedal walking in an individual of Lucy's body size.

  10. The pelvis and femur of Ardipithecus ramidus: the emergence of upright walking.

    PubMed

    Lovejoy, C Owen; Suwa, Gen; Spurlock, Linda; Asfaw, Berhane; White, Tim D

    2009-10-02

    The femur and pelvis of Ardipithecus ramidus have characters indicative of both upright bipedal walking and movement in trees. Consequently, bipedality in Ar. ramidus was more primitive than in later Australopithecus. Compared with monkeys and Early Miocene apes such as Proconsul, the ilium in Ar. ramidus is mediolaterally expanded, and its sacroiliac joint is located more posteriorly. These changes are shared with some Middle and Late Miocene apes as well as with African apes and later hominids. However, in contrast to extant apes, bipedality in Ar. ramidus was facilitated by craniocaudal shortening of the ilium and enhanced lordotic recurvature of the lower spine. Given the predominant absence of derived traits in other skeletal regions of Ar. ramidus, including the forelimb, these adaptations were probably acquired shortly after divergence from our last common ancestor with chimpanzees. They therefore bear little or no functional relationship to the highly derived suspension, vertical climbing, knuckle-walking, and facultative bipedality of extant African apes.

  11. Effect of end-stage hip, knee, and ankle osteoarthritis on walking mechanics.

    PubMed

    Schmitt, Daniel; Vap, Alexander; Queen, Robin M

    2015-09-01

    This study tested the hypothesis that the presence of isolated ankle (A-OA; N=30), knee (K-OA; N=20), or hip (H-OA; N=30) osteoarthritis (OA) compared to asymptomatic controls (N=15) would lead to mechanical changes in the affected joint but also in all other lower limb joints and gait overall. Stride length, stance and swing times, as well as joint angles and moments at the hip, knee, and ankle were derived from 3-D kinematic and kinetic data collected from seven self-selected speed walking trial. Values were compared across groups using a 1×4 ANCOVA, covarying for walking speed. With walking speed controlled, the results indicated a reduction in hip and knee extension and ankle plantar flexion in accordance with the joint affected. In addition, OA in one joint had strong effects on other joints. In both H-OA and K-OA groups the hip never passed into extension, and A-OA subjects significantly changed hip kinematics to compensate for lack of plantar flexion. Finally, OA in any joint led to lower peak vertical forces as well as extension and plantar flexion moments compared to controls. The presence of end-stage OA at various lower extremity joints results in compensatory gait mechanics that cause movement alterations throughout the lower extremity. This work reinforces our understanding of the complex interaction of joints of the lower limb and the importance of focusing on the mechanics of the entire lower limb when considering gait disability and potential interventions in patients with isolated OA.

  12. Compensatory mechanisms in below-knee amputee gait in response to increasing steady-state walking speeds.

    PubMed

    Silverman, Anne K; Fey, Nicholas P; Portillo, Albert; Walden, Judith G; Bosker, Gordon; Neptune, Richard R

    2008-11-01

    Compensatory mechanisms in below-knee amputee gait are necessary due to the functional loss of the ankle muscles, especially at higher walking speeds when the mechanical energetic demands of walking are greater. The objective of this study was to examine amputee anterior/posterior (A/P) ground reaction force (GRF) impulses and joint kinetics across a wide range of steady-state walking speeds to further understand the compensatory mechanisms used by below-knee amputees. We hypothesized that amputees would rely more on their intact leg to generate greater propulsion relative to the residual leg, which would result in greater GRF asymmetry between legs as walking speed increased. Amputee and control subject kinematic and kinetic data were collected during overground walking at four different speeds. Group (n=14) average amputee data showed no significant differences in braking or propulsive GRF impulse ratios, except the propulsive ratio at 0.9 m/s, indicating that the subjects maintained their initial levels of GRF asymmetry when walking faster. Therefore, our hypothesis was not supported (i.e., walking faster does not increase GRF loading asymmetry). The primary compensatory mechanism was greater positive residual leg hip joint power and work in early stance, which led to increased propulsion from the residual leg as walking speed increased. In addition, amputees had reduced residual leg positive knee work in early stance, suggesting increased output from the biarticular hamstrings. Thus, increasing residual leg hip extensor strength and output may be a useful mechanism to reduce GRF loading asymmetry between the intact and residual legs.

  13. Finite element analysis of sliding distance and contact mechanics of hip implant under dynamic walking conditions.

    PubMed

    Gao, Yongchang; Jin, Zhongmin; Wang, Ling; Wang, Manyi

    2015-06-01

    An explicit finite element method was developed to predict the dynamic behavior of the contact mechanics for a hip implant under normal walking conditions. Two key parameters of mesh sensitivity and time steps were examined to balance the accuracy and computational cost. Both the maximum contact pressure and accumulated sliding distance showed good agreement with those in the previous studies using the implicit finite element analysis and analytical methods. Therefore, the explicit finite element method could be used to predict the contact pressure and accumulated sliding distance for an artificial hip joint simultaneously in dynamic manner.

  14. Walking at non-constant speeds: mechanical work, pendular transduction, and energy congruity.

    PubMed

    Balbinot, G

    2017-05-01

    Although almost half of all walking bouts in urban environments consist of less than 12 consecutive steps and several day-to-day gait activities contain transient gait responses, in most studies gait analysis is performed at steady-state. This study aimed to analyze external (Wext ) and internal mechanical work (Wint ), pendulum-like mechanics, and elastic energy usage during constant and non-constant speeds. The mechanical work, pendular transduction, and energy congruity (an estimate of storage and release of elastic energy) during walking were computed using two force platforms. We found that during accelerating gait (+NCS) energy recovery is maintained, besides extra W(+)ext , for decelerating gait (-NCS) poor energy recovery was counterbalanced by W(-)ext and C% predominance. We report an increase in elastic energy usage with speed (4-11%). Both W(-)ext and %C suggests that elastic energy usage is higher at faster speeds and related to -NCS (≈20% of elastic energy usage). This study was the first to show evidences of elastic energy usage during constant and non-constant speeds.

  15. Mechanisms underpinning use of new walking and cycling infrastructure in different contexts: mixed-method analysis.

    PubMed

    Sahlqvist, Shannon; Goodman, Anna; Jones, Tim; Powell, Jane; Song, Yena; Ogilvie, David

    2015-02-21

    Few studies have evaluated the effects of infrastructural improvements to promote walking and cycling. Even fewer have explored how the context and mechanisms of such interventions may interact to produce their outcomes. This mixed-method analysis forms part of the UK iConnect study, which aims to evaluate new walking and cycling routes at three sites - Cardiff, Kenilworth and Southampton. Applying a complementary follow-up approach, we first identified differences in awareness and patterns of use of the infrastructure in survey data from a cohort of adult residents at baseline in spring 2010 (n = 3516) and again one (n = 1849) and two (n = 1510) years later following completion of the infrastructural projects (Analysis 1). We subsequently analysed data from 17 semi-structured interviews with key informants to understand how the new schemes might influence walking and cycling (Analysis 2a). In parallel, we analysed cohort survey data on environmental perceptions (Analysis 2b). We integrated these two datasets to interpret differences across the sites consistent with a theoretical framework that hypothesised that the schemes would improve connectivity and the social environment. After two years, 52% of Cardiff respondents reported using the infrastructure compared with 37% in Kenilworth and 22% in Southampton. Patterns of use did not vary substantially between sites. 17% reported using the new infrastructure for transport, compared with 39% for recreation. Environmental perceptions at baseline were generally unfavourable, with the greatest improvements in Cardiff. Qualitative data revealed that all schemes had a recreational focus to varying extents, that the visibility of schemes to local people might be an important mechanism driving use and that the scale and design of the schemes and the contrast they presented with existing infrastructure may have influenced their use. The dominance of recreational uses may have reflected the specific local goals of

  16. Step length asymmetry is representative of compensatory mechanisms used in post-stroke hemiparetic walking.

    PubMed

    Allen, Jessica L; Kautz, Steven A; Neptune, Richard R

    2011-04-01

    Post-stroke hemiparetic subjects walk with asymmetrical step lengths that are highly variable between subjects and may be indicative of the underlying impairments and compensatory mechanisms used. The goal of this study was to determine if post-stroke hemiparetic subjects grouped by step length asymmetry have similar abnormal walking biomechanics compared to non-impaired walkers. Kinematic and ground reaction force data were recorded from 55 hemiparetic subjects walking at their self-selected speed and 21 age and speed-matched non-impaired control subjects. Hemiparetic subjects were grouped by paretic step ratio, which was calculated as the paretic step-length divided by the sum of paretic and nonparetic step-lengths, into high (>0.535), symmetric (0.535-0.465) and low (<0.465) groups. Non-parametric Wilcoxin signed-rank tests were used to test for differences in joint kinetic measures between hemiparetic groups and speed-matched control subjects during late single-leg stance and pre-swing. The paretic leg ankle moment impulse was reduced in all hemiparetic subjects regardless of their paretic step ratio. The high group had increased nonparetic leg ankle plantarflexor and knee extensor moment impulses, the symmetric group had increased hip flexor moment impulses on both the paretic and nonparetic leg and the low group had no additional significant differences in joint moment impulses. These results suggest that the direction of asymmetry can be used to identify both the degree of paretic plantarflexor impairment and the compensatory mechanisms used by post-stroke hemiparetic subjects. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Step Length Asymmetry is Representative of Compensatory Mechanisms Used in Post-Stroke Hemiparetic Walking

    PubMed Central

    Allen, Jessica L.; Kautz, Steven A.; Neptune, Richard R.

    2011-01-01

    Post-stroke hemiparetic subjects walk with asymmetrical step lengths that are highly variable between subjects and may be indicative of the underlying impairments and compensatory mechanisms used. The goal of this study was to determine if post-stroke hemiparetic subjects grouped by step length asymmetry have similar abnormal walking biomechanics compared to non-impaired walkers. Kinematic and ground reaction force data were recorded from 55 hemiparetic subjects walking at their self-selected speed and 21 age and speed-matched non-impaired control subjects. Hemiparetic subjects were grouped by paretic step ratio, which was calculated as the paretic step-length divided by the sum of paretic and nonparetic step-lengths, into high (>0.535), symmetric (0.535–0.465) and low (<0.465) groups. Non-parametric Wilcoxin signed-rank tests were used to test for differences in joint kinetic measures between hemiparetic groups and speed-matched control subjects during late single-leg stance and pre-swing. The paretic leg ankle moment impulse was reduced in all hemiparetic subjects regardless of their paretic step ratio. The high group had increased nonparetic leg ankle plantarflexor and knee extensor moment impulses, the symmetric group had increased hip flexor moment impulses on both the paretic and nonparetic leg and the low group had no additional significant differences in joint moment impulses. These results suggest that the direction of asymmetry can be used to identify both the degree of paretic plantarflexor impairment and the compensatory mechanisms used by post-stroke hemiparetic subjects. PMID:21316240

  18. Common motor mechanisms support body load in serially homologous legs of cockroaches in posture and walking.

    PubMed

    Quimby, Laura A; Amer, Ayman S; Zill, Sasha N

    2006-03-01

    We studied the mechanisms underlying support of body load in posture and walking in serially homologous legs of cockroaches. Activities of the trochanteral extensor muscle in the front or middle legs were recorded neurographically while animals were videotaped. Body load was increased via magnets attached to the thorax and varied through a coil below the substrate. In posture, tonic firing of the slow trochanteral extensor motoneuron (Ds) in each leg was strongly modulated by changing body load. Rapid load increases produced decreases in body height and sharp increments in extensor firing. The peak of extensor activity more closely approximated the maximum velocity of body displacement than the body position. In walking, extensor bursts in front and middle legs were initiated during swing and continued into the stance phase. Moderate tonic increases in body load elicited similar, specific, phase dependent changes in both legs: extensor firing was not altered in swing but was higher after foot placement in stance. These motor adjustments to load are not anticipatory but apparently depend upon sensory feedback. These data are consistent with previous findings in the hind legs and support the idea that body load is countered by common motor mechanisms in serially homologous legs.

  19. Introduction to Focus Issue: Bipedal Locomotion-From Robots to Humans

    NASA Astrophysics Data System (ADS)

    Milton, John G.

    2009-06-01

    Running and walking, collectively referred to as bipedal locomotion, represent self-organized behaviors generated by a spatially distributed dynamical system operating under the constraint that a person must be able to move without falling down. The organizing principles involve both forces actively regulated by the nervous system and those generated passively by the biomechanical properties of the musculoskeletal system and the environment in which the movements occur. With the development of modern motion capture and electrophysiological techniques it has become possible to explore the dynamical interplay between the passive and active controllers of locomotion in a manner that directly compares observation to predictions made by relevant mathematical and computer models. Consequently, many of the techniques initially developed to study nonlinear dynamical systems, including stability analyses, phase resetting and entrainment properties of limit cycles, and fractal and multifractal analysis, have come to play major roles in guiding progress. This Focus Issue discusses bipedal locomotion from the point of view of dynamical systems theory with the goal of stimulating discussion between the dynamical systems, physics, biomechanics, and neuroscience communities.

  20. Introduction to focus issue: bipedal locomotion--from robots to humans.

    PubMed

    Milton, John G

    2009-06-01

    Running and walking, collectively referred to as bipedal locomotion, represent self-organized behaviors generated by a spatially distributed dynamical system operating under the constraint that a person must be able to move without falling down. The organizing principles involve both forces actively regulated by the nervous system and those generated passively by the biomechanical properties of the musculoskeletal system and the environment in which the movements occur. With the development of modern motion capture and electrophysiological techniques it has become possible to explore the dynamical interplay between the passive and active controllers of locomotion in a manner that directly compares observation to predictions made by relevant mathematical and computer models. Consequently, many of the techniques initially developed to study nonlinear dynamical systems, including stability analyses, phase resetting and entrainment properties of limit cycles, and fractal and multifractal analysis, have come to play major roles in guiding progress. This Focus Issue discusses bipedal locomotion from the point of view of dynamical systems theory with the goal of stimulating discussion between the dynamical systems, physics, biomechanics, and neuroscience communities.

  1. Compliant bipedal model with the center of pressure excursion associated with oscillatory behavior of the center of mass reproduces the human gait dynamics.

    PubMed

    Jung, Chang Keun; Park, Sukyung

    2014-01-03

    Although the compliant bipedal model could reproduce qualitative ground reaction force (GRF) of human walking, the model with a fixed pivot showed overestimations in stance leg rotation and the ratio of horizontal to vertical GRF. The human walking data showed a continuous forward progression of the center of pressure (CoP) during the stance phase and the suspension of the CoP near the forefoot before the onset of step transition. To better describe human gait dynamics with a minimal expense of model complexity, we proposed a compliant bipedal model with the accelerated pivot which associated the CoP excursion with the oscillatory behavior of the center of mass (CoM) with the existing simulation parameter and leg stiffness. Owing to the pivot acceleration defined to emulate human CoP profile, the arrival of the CoP at the limit of the stance foot over the single stance duration initiated the step-to-step transition. The proposed model showed an improved match of walking data. As the forward motion of CoM during single stance was partly accounted by forward pivot translation, the previously overestimated rotation of the stance leg was reduced and the corresponding horizontal GRF became closer to human data. The walking solutions of the model ranged over higher speed ranges (~1.7 m/s) than those of the fixed pivoted compliant bipedal model (~1.5m/s) and exhibited other gait parameters, such as touchdown angle, step length and step frequency, comparable to the experimental observations. The good matches between the model and experimental GRF data imply that the continuous pivot acceleration associated with CoM oscillatory behavior could serve as a useful framework of bipedal model.

  2. Characterization of the mechanical properties of backpacks and their influence on the energetics of walking.

    PubMed

    Foissac, Matthieu; Millet, Guillaume Y; Geyssant, André; Freychat, Philippe; Belli, Alain

    2009-01-19

    The objectives of the experiment were (i) to characterize the mechanical properties of backpacks and (ii) to study the influence of a flexible backpack on the energetics and kinematics of walking. Twelve subjects walked at different speeds on a treadmill with each of two backpacks loaded with 25% bodyweight, with either a rigid or a flexible link between the body attachment and the suspended loads. A single degree of freedom linear model of the link between the pack and the trunk was used to calculate the stiffness and damping coefficient of the two backpacks. The oxygen consumption (VO2) and the vertical acceleration of both the backpack and trunk were measured. The vertical excursion of the pack given by the model was significantly correlated with that actually measured (R=0.87, p<0.001). At 3.7 and 4.5 km h(-1) the flexible pack induced lower acceleration peaks (respectively -22% and -8%; p<0.05) and tended to reduce VO2 (p=0.055 at 4.5 km h(-1)) compared with the rigid one. At 5.2 and 6 km h(-1) both the accelerative forces and VO2 increased with the flexible pack (p<0.05) mainly because of the high vertical movement of the pack. It was concluded that a simple model can be used to predict the vertical excursion of the pack and that a flexible backpack can provide energetic benefits when its oscillations are nearly in phase with those of the trunk. However, any resonance effect can lead to a modified walking pattern and an increased metabolic cost.

  3. Biased motion and molecular motor properties of bipedal spiders.

    PubMed

    Samii, Laleh; Linke, Heiner; Zuckermann, Martin J; Forde, Nancy R

    2010-02-01

    Molecular spiders are synthetic molecular motors featuring multiple legs that each can interact with a substrate through binding and cleavage. Experimental studies suggest the motion of the spider in a matrix is biased toward uncleaved substrates and that spider properties such as processivity can be altered by changing the binding strength of the legs to substrate [R. Pei, S. K. Taylor, D. Stefanovic, S. Rudchenko, T. E. Mitchell, and M. N. Stojanovic, J. Am. Chem. Soc. 128, 12693 (2006)]. We investigate the origin of biased motion and molecular motor properties of bipedal spiders using Monte Carlo simulations. Our simulations combine a realistic chemical kinetic model, hand-over-hand or inchworm modes of stepping, and the use of a one-dimensional track. We find that stronger binding to substrate, cleavage and spider detachment from the track are contributing mechanisms to population bias. We investigate the contributions of stepping mechanism to speed, randomness parameter, processivity, coupling, and efficiency, and comment on how these molecular motor properties can be altered by changing experimentally tunable kinetic parameters.

  4. Biased motion and molecular motor properties of bipedal spiders

    NASA Astrophysics Data System (ADS)

    Samii, Laleh; Linke, Heiner; Zuckermann, Martin J.; Forde, Nancy R.

    2010-02-01

    Molecular spiders are synthetic molecular motors featuring multiple legs that each can interact with a substrate through binding and cleavage. Experimental studies suggest the motion of the spider in a matrix is biased toward uncleaved substrates and that spider properties such as processivity can be altered by changing the binding strength of the legs to substrate [R. Pei, S. K. Taylor, D. Stefanovic, S. Rudchenko, T. E. Mitchell, and M. N. Stojanovic, J. Am. Chem. Soc. 128, 12693 (2006)]. We investigate the origin of biased motion and molecular motor properties of bipedal spiders using Monte Carlo simulations. Our simulations combine a realistic chemical kinetic model, hand-over-hand or inchworm modes of stepping, and the use of a one-dimensional track. We find that stronger binding to substrate, cleavage and spider detachment from the track are contributing mechanisms to population bias. We investigate the contributions of stepping mechanism to speed, randomness parameter, processivity, coupling, and efficiency, and comment on how these molecular motor properties can be altered by changing experimentally tunable kinetic parameters.

  5. Effects of walking in deep venous thrombosis: a new integrated solid and fluid mechanics model.

    PubMed

    López, Josep M; Fortuny, Gerard; Puigjaner, Dolors; Herrero, Joan; Marimon, Francesc; Garcia-Bennett, Josep

    2016-08-09

    Deep venous thrombosis (DVT) is a common disease. Large thrombi in venous vessels cause bad blood circulation and pain; and when a blood clot detaches from a vein wall, it causes an embolism whose consequences range from mild to fatal. Walking is recommended to DVT patients as a therapeutical complement. In this study the mechanical effects of walking on a specific patient of DVT were simulated by means of an unprecedented integration of 3 elements: a real geometry, a biomechanical model of body tissues, and a computational fluid dynamics study. A set of computed tomography images of a patient's leg with a thrombus in the popliteal vein was employed to reconstruct a geometry model. Then a biomechanical model was used to compute the new deformed geometry of the vein as a function of the fiber stretch level of the semimembranosus muscle. Finally, a computational fluid dynamics study was performed to compute the blood flow and the wall shear stress (WSS) at the vein and thrombus walls. Calculations showed that either a lengthening or shortening of the semimembranosus muscle led to a decrease of WSS levels up to 10%. Notwithstanding, changes in blood viscosity properties or blood flow rate may easily have a greater impact in WSS.

  6. Biomechanical modeling and sensitivity analysis of bipedal running ability. I. Extant taxa.

    PubMed

    Hutchinson, John R

    2004-10-01

    I used a simple mathematical model of the inverse dynamics of locomotion to estimate the minimum muscle masses required to maintain quasi-static equilibrium about the four main limb joints at mid-stance of fast running. Models of 10 extant taxa (a human, a kangaroo, two lizards, an alligator, and five birds) were analyzed in various bipedal poses to examine how anatomy, size, limb orientation, and other model parameters influence running ability. I examined how the muscle masses required for fast running compare to the muscle masses that are actually able to exert moments about the hip, knee, ankle, and toe joints, to see how support ability varies across the limb. I discuss the assumptions and limitations of the models, using sensitivity analysis to see how widely the results differed with feasible parameter input values. Even with a wide range of input values, the models validated the analysis procedure. Animals that are known to run bipedally were calculated as able to preserve quasi-static equilibrium about their hindlimb joints at mid-stance, whereas non-bipedal runners (iguanas and alligators) were recognized as having too little muscle mass to run quickly in bipedal poses. Thus, this modeling approach should be reliable for reconstructing running ability in extinct bipeds such as nonavian dinosaurs. The models also elucidated how key features are important for bipedal running capacity, such as limb orientation, muscle moment arms, muscle fascicle lengths, and body size. None of the animals modeled had extensor muscle masses acting about any one joint that were 7% or more of their body mass, which provides a reasonable limit for how much muscle mass is normally apportioned within a limb to act about a particular joint. The models consistently showed that a key biomechanical limit on running ability is the capacity of ankle extensors to generate sufficiently large joint moments. Additionally, the analysis reveals how large ratite birds remain excellent runners

  7. Mechanics of slope walking in the cat: quantification of muscle load, length change, and ankle extensor EMG patterns.

    PubMed

    Gregor, Robert J; Smith, D Webb; Prilutsky, Boris I

    2006-03-01

    Unexpected changes in flexor-extensor muscle activation synergies during slope walking in the cat have been explained previously by 1) a reorganization of circuitry in the central pattern generator or 2) altered muscle and cutaneous afferent inputs to motoneurons that modulate their activity. The aim of this study was to quantify muscle length changes, muscle loads, and ground reaction forces during downslope, level, and upslope walking in the cat. These mechanical variables are related to feedback from muscle length and force, and paw pad cutaneous afferents, and differences in these variables between the slope walking conditions could provide additional insight into possible mechanisms of the muscle control. Kinematics, ground reaction forces, and EMG were recorded while cats walked on a walkway in three conditions: downslope (-26.6 deg), level (0 deg), and upslope (26.6 deg). The resultant joint moments were calculated using inverse dynamics analysis; length and velocity of major hindlimb muscle-tendon units (MTUs) were calculated using a geometric model and calculated joint angles. It was found that during stance in downslope walking, the MTU stretch of ankle and knee extensors and MTU peak stretch velocities of ankle extensors were significantly greater than those in level or upslope conditions, whereas forces applied to the paw pad and peaks of ankle and hip extensor moments were significantly smaller. The opposite was true for upslope walking. It was suggested that these differences between upslope and downslope walking might affect motion-dependent feedback, resulting in muscle activity changes recorded here or reported in the literature.

  8. External Mechanical Work and Pendular Energy Transduction of Overground and Treadmill Walking in Adolescents with Unilateral Cerebral Palsy.

    PubMed

    Zollinger, Marie; Degache, Francis; Currat, Gabriel; Pochon, Ludmila; Peyrot, Nicolas; Newman, Christopher J; Malatesta, Davide

    2016-01-01

    Motor impairments affect functional abilities and gait in children and adolescents with cerebral palsy (CP). Improving their walking is an essential objective of treatment, and the use of a treadmill for gait analysis and training could offer several advantages in adolescents with CP. However, there is a controversy regarding the similarity between treadmill and overground walking both for gait analysis and training in children and adolescents. The aim of this study was to compare the external mechanical work and pendular energy transduction of these two types of gait modalities at standard and preferred walking speeds in adolescents with unilateral cerebral palsy (UCP) and typically developing (TD) adolescents matched on age, height and body mass. Spatiotemporal parameters, external mechanical work and pendular energy transduction of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 10 UCP (14.2 ± 1.7 year) and 10 TD (14.1 ± 1.9 year) adolescents during treadmill and overground walking at standard and preferred speeds. The treadmill induced almost identical mechanical changes to overground walking in TD adolescents and those with UCP, with the exception of potential and kinetic vertical and lateral mechanical works, which are both significantly increased in the overground-treadmill transition only in UCP (P < 0.05). Adolescents with UCP have a reduced adaptive capacity in absorbing and decelerating the speed created by a treadmill (i.e., dynamic stability) compared to TD adolescents. This may have an important implication in rehabilitation programs that assess and train gait by using a treadmill in adolescents with UCP.

  9. External Mechanical Work and Pendular Energy Transduction of Overground and Treadmill Walking in Adolescents with Unilateral Cerebral Palsy

    PubMed Central

    Zollinger, Marie; Degache, Francis; Currat, Gabriel; Pochon, Ludmila; Peyrot, Nicolas; Newman, Christopher J.; Malatesta, Davide

    2016-01-01

    Purpose: Motor impairments affect functional abilities and gait in children and adolescents with cerebral palsy (CP). Improving their walking is an essential objective of treatment, and the use of a treadmill for gait analysis and training could offer several advantages in adolescents with CP. However, there is a controversy regarding the similarity between treadmill and overground walking both for gait analysis and training in children and adolescents. The aim of this study was to compare the external mechanical work and pendular energy transduction of these two types of gait modalities at standard and preferred walking speeds in adolescents with unilateral cerebral palsy (UCP) and typically developing (TD) adolescents matched on age, height and body mass. Methods: Spatiotemporal parameters, external mechanical work and pendular energy transduction of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 10 UCP (14.2 ± 1.7 year) and 10 TD (14.1 ± 1.9 year) adolescents during treadmill and overground walking at standard and preferred speeds. Results: The treadmill induced almost identical mechanical changes to overground walking in TD adolescents and those with UCP, with the exception of potential and kinetic vertical and lateral mechanical works, which are both significantly increased in the overground-treadmill transition only in UCP (P < 0.05). Conclusions: Adolescents with UCP have a reduced adaptive capacity in absorbing and decelerating the speed created by a treadmill (i.e., dynamic stability) compared to TD adolescents. This may have an important implication in rehabilitation programs that assess and train gait by using a treadmill in adolescents with UCP. PMID:27148062

  10. Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking.

    PubMed

    Jackson, Rachel W; Dembia, Christopher L; Delp, Scott L; Collins, Steven H

    2017-06-01

    The goal of this study was to gain insight into how ankle exoskeletons affect the behavior of the plantarflexor muscles during walking. Using data from previous experiments, we performed electromyography-driven simulations of musculoskeletal dynamics to explore how changes in exoskeleton assistance affected plantarflexor muscle-tendon mechanics, particularly for the soleus. We used a model of muscle energy consumption to estimate individual muscle metabolic rate. As average exoskeleton torque was increased, while no net exoskeleton work was provided, a reduction in tendon recoil led to an increase in positive mechanical work performed by the soleus muscle fibers. As net exoskeleton work was increased, both soleus muscle fiber force and positive mechanical work decreased. Trends in the sum of the metabolic rates of the simulated muscles correlated well with trends in experimentally observed whole-body metabolic rate (R(2)=0.9), providing confidence in our model estimates. Our simulation results suggest that different exoskeleton behaviors can alter the functioning of the muscles and tendons acting at the assisted joint. Furthermore, our results support the idea that the series tendon helps reduce positive work done by the muscle fibers by storing and returning energy elastically. We expect the results from this study to promote the use of electromyography-driven simulations to gain insight into the operation of muscle-tendon units and to guide the design and control of assistive devices. © 2017. Published by The Company of Biologists Ltd.

  11. Metabolic Cost, Mechanical Work, and Efficiency during Normal Walking in Obese and Normal-Weight Children

    ERIC Educational Resources Information Center

    Huang, Liang; Chen, Peijie; Zhuang, Jie; Zhang, Yanxin; Walt, Sharon

    2013-01-01

    Purpose: This study aimed to investigate the influence of childhood obesity on energetic cost during normal walking and to determine if obese children choose a walking strategy optimizing their gait pattern. Method: Sixteen obese children with no functional abnormalities were matched by age and gender with 16 normal-weight children. All…

  12. Metabolic Cost, Mechanical Work, and Efficiency during Normal Walking in Obese and Normal-Weight Children

    ERIC Educational Resources Information Center

    Huang, Liang; Chen, Peijie; Zhuang, Jie; Zhang, Yanxin; Walt, Sharon

    2013-01-01

    Purpose: This study aimed to investigate the influence of childhood obesity on energetic cost during normal walking and to determine if obese children choose a walking strategy optimizing their gait pattern. Method: Sixteen obese children with no functional abnormalities were matched by age and gender with 16 normal-weight children. All…

  13. Resuspension of allergen-containing particles under mechanical and aerodynamic disturbances from human walking

    NASA Astrophysics Data System (ADS)

    Gomes, C.; Freihaut, J.; Bahnfleth, W.

    This study presents and develops a controlled and characterized method to explore the influence of specific occupant activity on the aerosolization of allergen-containing particles. Indoor allergen-related diseases are primarily inhalation sensitized and developed, suggesting an aerobiological pathway of allergen-containing carrier particles from dust reservoir to occupant respiration. But the pathways are not well understood or quantified. The influence of occupant walking on particle aerosolization is simulated by a system in which complex floor disturbances are deconvoluted into aerodynamic and mechanical components. Time resolved particle size distributions are measured for particles resuspended from representative samples of flooring materials and different types of floor disturbances in an environmentally controlled experimental chamber. Results indicate aerodynamic disturbances, relative to mechanical, dominate the particle resuspension behavior. Dust type, dust load and floor type showed marginal influences on a normalized surface loading basis. Humidity effects were not clear since during experiments the floor samples may not have reached moisture partitioning equilibrium with the controlled air humidity. Average resuspension rates ranged from 10 -7 to 10 -3 min -1, having phenomenological consistency with previous, large room or chamber investigations, suggesting the method can be utilized to develop a database for particle resuspension rates.

  14. Are There Sex Differences in Knee Cartilage Composition and Walking Mechanics in Healthy and Osteoarthritis Populations?

    PubMed

    Kumar, Deepak; Souza, Richard B; Subburaj, Karupppasamy; MacLeod, Toran D; Singh, Justin; Calixto, Nathaniel E; Nardo, Lorenzo; Link, Thomas M; Li, Xiaojuan; Lane, Nancy E; Majumdar, Sharmila

    2015-08-01

    Women are at a greater risk for knee osteoarthritis (OA), but reasons for this greater risk in women are not well understood. It may be possible that differences in cartilage composition and walking mechanics are related to greater OA risk in women. (1) Do women have higher knee cartilage and meniscus T1ρ than men in young healthy, middle-aged non-OA and OA populations? (2) Do women exhibit greater static and dynamic (during walking) knee loading than men in young healthy, middle-aged non-OA and OA populations? Data were collected from three cohorts: (1) young active (<35 years) (20 men, 13 women); (2) middle-aged (≥35 years) without OA (Kellgren-Lawrence [KL] grade < 2) (43 men, 65 women); and (3) middle-aged with OA (KL>1) (18 men, 25 women). T1ρ and T2 relaxation times for cartilage in the medial knee, lateral knee, and patellofemoral compartments and medial and lateral menisci were quantified with 3.0-T MRI. A subset of the participants underwent three-dimensional motion capture during walking for calculation of peak knee flexion and adduction moments, flexion and adduction impulses, and peak adduction angle. Differences in MR, radiograph, and gait parameters between men and women were compared in the three groups separately using multivariate analysis of variance. Women had higher lateral articular cartilage T1ρ (men=40.5 [95% confidence interval {CI}, 38.8-42.3] ms; women=43.3 [95% CI, 41.9-44.7] ms; p=0.017) and patellofemoral T1ρ (men=44.4 [95% CI, 42.6-46.3] ms; women=48.4 [95% CI, 46.9-50.0] ms; p=0.002) in the OA group; and higher lateral meniscus T1ρ in the young group (men=15.3 [95% CI, 14.7-16.0] ms; women=16.4 [95% CI, 15.6-17.2] ms; p=0.045). The peak adduction moment in the second half of stance was lower in women in the middle-aged (men=2.05 [95% CI, 1.76-2.34] %BW*Ht; women=1.66 [95% CI, 1.44-1.89] %BW*Ht; p=0.037) and OA (men=2.34 [95% CI, 1.76-2.91] %BW*Ht; women=1.42 [95% CI, 0.89-1.94] %BW*Ht; p=0.022) groups. Static varus from

  15. Human Odometry Verifies the Symmetry Perspective on Bipedal Gaits

    ERIC Educational Resources Information Center

    Turvey, M. T.; Harrison, Steven J.; Frank, Till D.; Carello, Claudia

    2012-01-01

    Bipedal gaits have been classified on the basis of the group symmetry of the minimal network of identical differential equations (alias "cells") required to model them. Primary gaits are characterized by dihedral symmetry, whereas secondary gaits are characterized by a lower, cyclic symmetry. This fact was used in a test of human…

  16. Human Odometry Verifies the Symmetry Perspective on Bipedal Gaits

    ERIC Educational Resources Information Center

    Turvey, M. T.; Harrison, Steven J.; Frank, Till D.; Carello, Claudia

    2012-01-01

    Bipedal gaits have been classified on the basis of the group symmetry of the minimal network of identical differential equations (alias "cells") required to model them. Primary gaits are characterized by dihedral symmetry, whereas secondary gaits are characterized by a lower, cyclic symmetry. This fact was used in a test of human…

  17. Effect of carrying a weighted backpack on lung mechanics during treadmill walking in healthy men.

    PubMed

    Dominelli, Paolo B; Sheel, A William; Foster, Glen E

    2012-06-01

    Weighted backpacks are used extensively in recreational and occupational settings, yet their effects on lung mechanics during acute exercise is poorly understood. The purpose of this study was to determine the effects of different backpack weights on lung mechanics and breathing patterns during treadmill walking. Subjects (n = 7, age = 28 ± 6 years), completed two 2.5-min exercise stages for each backpack condition [no backpack (NP), an un-weighted backpack (NW) or a backpack weighing 15, 25 or 35 kg]. A maximal expiratory flow volume curve was generated for each backpack condition and an oesophageal balloon catheter was used to estimate pleural pressure. The 15, 25 and 35 kg backpacks caused a 3, 5 and 8% (P < 0.05) reduction in forced vital capacity compared with the NP condition, respectively. For the same exercise stage, the power of breathing (POB) requirement was higher in the 35 kg backpack compared to NP (32 ± 4.3 vs. 88 ± 9.0 J min(-1), P < 0.05; respectively). Independent of changes in minute ventilation, end-expiratory lung volume decreased as backpack weight increased. As backpack weight increased, there was a concomitant decline in calculated maximal ventilation, a rise in minute ventilation, and a resultant greater utilization of maximal available ventilation. In conclusion, wearing a weighted backpack during an acute bout of exercise altered operational lung volumes; however, adaptive changes in breathing mechanics may have minimized changes in the required POB such that at an iso-ventilation, wearing a backpack weighing up to 35 kg does not increase the POB requirement.

  18. Effects of prolonged walking on neural and mechanical components of stretch responses in the human soleus muscle

    PubMed Central

    Cronin, Neil J; Ishikawa, Masaki; af Klint, Richard; Komi, Paavo V; Avela, Janne; Sinkjaer, Thomas; Voigt, Michael

    2009-01-01

    After repeated passive stretching, tendinous tissue compliance increases in the human soleus (SOL) muscle–tendon unit. During movement, such changes would have important consequences for neural and mechanical stretch responses. This study examined the existence of such effects in response to a 75 min walking intervention. Eleven healthy subjects walked on a treadmill at 4 km h−1 with a robotic stretch device attached to the left leg. Ultrasonography was used to measure SOL fascicle lengths, and surface EMG activity was recorded in the SOL and tibialis anterior (TA) muscles. Perturbations of 6 deg were imposed at three different measurement intervals: Pre (immediately before the walking intervention), Mid (after approximately 30 min of walking) and Post (immediately after the intervention). Between the Pre–Mid and Mid–Post intervals, subjects walked for 30 min at a gradient of 3%. After the intervention, the amplitude and velocity of fascicle stretch both decreased (by 46 and 59%, respectively; P < 0.001) in response to a constant external perturbation, as did short (33%; P < 0.01) and medium (25%; P < 0.01) latency stretch reflex amplitudes. A faster perturbation elicited at the end of the protocol resulted in a recovery of fascicle stretch velocities and short latency reflex amplitudes to the pre-exercise values. These findings suggest that repeated stretching and shortening of a muscle–tendon unit can induce short-term structural changes in the tendinous tissues during human walking. The data also highlight the effect of these changes on neural feedback from muscle sensory afferents. PMID:19622608

  19. Effects of prolonged walking on neural and mechanical components of stretch responses in the human soleus muscle.

    PubMed

    Cronin, Neil J; Ishikawa, Masaki; Af Klint, Richard; Komi, Paavo V; Avela, Janne; Sinkjaer, Thomas; Voigt, Michael

    2009-09-01

    After repeated passive stretching, tendinous tissue compliance increases in the human soleus (SOL) muscle-tendon unit. During movement, such changes would have important consequences for neural and mechanical stretch responses. This study examined the existence of such effects in response to a 75 min walking intervention. Eleven healthy subjects walked on a treadmill at 4 km h(1) with a robotic stretch device attached to the left leg. Ultrasonography was used to measure SOL fascicle lengths, and surface EMG activity was recorded in the SOL and tibialis anterior (TA) muscles. Perturbations of 6 deg were imposed at three different measurement intervals: Pre (immediately before the walking intervention), Mid (after approximately 30 min of walking) and Post (immediately after the intervention). Between the Pre-Mid and Mid-Post intervals, subjects walked for 30 min at a gradient of 3%. After the intervention, the amplitude and velocity of fascicle stretch both decreased (by 46 and 59%, respectively; P < 0.001) in response to a constant external perturbation, as did short (33%; P < 0.01) and medium (25%; P < 0.01) latency stretch reflex amplitudes. A faster perturbation elicited at the end of the protocol resulted in a recovery of fascicle stretch velocities and short latency reflex amplitudes to the pre-exercise values. These findings suggest that repeated stretching and shortening of a muscle-tendon unit can induce short-term structural changes in the tendinous tissues during human walking. The data also highlight the effect of these changes on neural feedback from muscle sensory afferents.

  20. Age-related neuromuscular adaptation does not affect the mechanical efficiency of lower limbs during walking.

    PubMed

    Monaco, V; Micera, S

    2012-07-01

    Ageing involves modifications of the locomotor system which is believed to increase energy consumption. This study aimed at verifying whether neuromuscular adaptation due to ageing, in conjunction with age-related modifications of the muscle-tendon actuators, involves greater muscle-tendon workload. Ten young and 7 elderly healthy subjects were assessed using gait analysis while walking at comparable speed. Planar models of muscle-driven locomotion, accounting for 14 muscles grouped into 9 equivalent actuators, were developed. Muscle-tendon forces were estimated by using the inverse-dynamic based static optimization where cost functions were tuned to capture the different muscle co-activation between groups. Following this, tendon and muscle shortening/lengthening was computed, and muscle-tendon work was estimated and compared between groups. Results showed that both groups produced comparable muscle mechanical work, though shared differently among muscles. In particular, young subjects showed a greater workload of ankle plantaflexor muscles and older subjects used greater eccentric energy at the knee extensors during stance phase. Moreover, young people used more elastic energy than older people. These findings suggest that the combination adaptation due to ageing, in conjunction with age-related modifications of the muscle-tendon actuators, do not significantly increase the overall energetic output of locomotion. Moreover, the motor control system appears to be characterised by a degree of adaptation which allows older individuals to achieve biomechanical efficiency comparable to younger subjects. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Avoidance of overheating and selection for both hair loss and bipedality in hominins.

    PubMed

    Ruxton, Graeme D; Wilkinson, David M

    2011-12-27

    Two frequently debated aspects of hominin evolution are the development of upright bipedal stance and reduction in body hair. It has long been argued, on the basis of heat-balance models, that thermoregulation might have been important in the evolution of both of these traits. Previous models were based on a stationary individual standing in direct sunlight; here we extend this approach to consider a walking hominin, having argued that walking is more thermally challenging than remaining still. Further, stationary activities may be more compatible with shade seeking than activities (such as foraging) involving travel across the landscape. Our model predictions suggest that upright stance probably evolved for nonthermoregulatory reasons. However, the thermoregulatory explanation for hair loss was supported. Specifically, we postulate progressive hair loss being selected and this allowing individuals to be active in hot, open environments initially around dusk and dawn without overheating. Then, as our ancestors' hair loss increased and sweating ability improved over evolutionary time, the fraction of the day when they could remain active in such environments extended. Our model suggests that only when hair loss and sweating ability reach near-modern human levels could hominins have been active in the heat of the day in hot, open environments.

  2. The gaits of primates: center of mass mechanics in walking, cantering and galloping ring-tailed lemurs, Lemur catta.

    PubMed

    O'Neill, Matthew C; Schmitt, Daniel

    2012-05-15

    Most primates, including lemurs, have a broad range of locomotor capabilities, yet much of the time, they walk at slow speeds and amble, canter or gallop at intermediate and fast speeds. Although numerous studies have investigated limb function during primate quadrupedalism, how the center of mass (COM) moves is not well understood. Here, we examined COM energy, work and power during walking, cantering and galloping in ring-tailed lemurs, Lemur catta (N=5), over a broad speed range (0.43-2.91 m s(-1)). COM energy recoveries were substantial during walking (35-71%) but lower during canters and gallops (10-51%). COM work, power and collisional losses increased with speed. The positive COM works were 0.625 J kg(-1) m(-1) for walks and 1.661 J kg(-1) m(-1) for canters and gallops, which are in the middle range of published values for terrestrial animals. Although some discontinuities in COM mechanics were evident between walking and cantering, there was no apparent analog to the trot-gallop transition across the intermediate and fast speed range (dimensionless v>0.75, Fr>0.5). A phenomenological model of a lemur cantering and trotting at the same speed shows that canters ensure continuous contact of the body with the substrate while reducing peak vertical COM forces, COM stiffness and COM collisions. We suggest that cantering, rather than trotting, at intermediate speeds may be tied to the arboreal origins of the Order Primates. These data allow us to better understand the mechanics of primate gaits and shed new light on primate locomotor evolution.

  3. Quadriceps and hamstrings morphology is related to walking mechanics and knee cartilage MRI relaxation times in young adults.

    PubMed

    Kumar, Deepak; Subburaj, Karupppasamy; Lin, Wilson; Karampinos, Dimitrios C; McCulloch, Charles E; Li, Xiaojuan; Link, Thomas M; Souza, Richard B; Majumdar, Sharmila

    2013-12-01

    Controlled laboratory study using a cross-sectional design. To analyze the relationship of quadriceps-hamstrings and medial-lateral quadriceps anatomical cross-sectional area (ACSA) ratios with knee loads during walking and articular and meniscal cartilage composition in young, healthy subjects. Muscle forces affect knee loading during walking, but it is not known if muscle morphology is associated with walking mechanics and cartilage composition in young subjects. Forty-two knees from 27 young, healthy, active volunteers (age, 20-35 years; body mass index, <28 kg/m(2)) underwent 3-T magnetic resonance imaging (MRI) and 3-D motion capture. Standard MRI sequences were used for articular and meniscal cartilage T1rho and T2 relaxation times and for quadriceps and hamstrings muscle ACSA. Frontal plane kinetics during the stance phase of walking was calculated. Generalized estimating equation models were used to identify muscle variables that predicted MRI and gait parameters. Quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were positively related to frontal plane loading (β = .21-.54, P≤.006), global articular cartilage relaxation times (β = .22-.28, P≤.041), and the medial-lateral ratio of meniscus T1rho relaxation time (β = .26-.36, P≤.049). The medial-lateral quadriceps ACSA ratio was positively related to global meniscus T1rho relaxation times (β = .30, P = .046). Higher quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were associated with higher frontal plane loading during walking and with articular and meniscal cartilage T1rho and T2 relaxation times. These findings highlight the relationships between different knee tissues and knee mechanics in young, healthy individuals.

  4. Quadriceps and Hamstrings Morphology Is Related to Walking Mechanics and Knee Cartilage MRI Relaxation Times in Young Adults

    PubMed Central

    KUMAR, DEEPAK; SUBBURAJ, KARUPPPASAMY; LIN, WILSON; KARAMPINOS, DIMITRIOS C.; MCCULLOCH, CHARLES E.; LI, XIAOJUAN; LINK, THOMAS M.; SOUZA, RICHARD B.; MAJUMDAR, SHARMILA

    2015-01-01

    STUDY DESIGN Controlled laboratory study using a cross-sectional design. OBJECTIVES To analyze the relationship of quadriceps-hamstrings and medial-lateral quadriceps anatomical cross-sectional area (ACSA) ratios with knee loads during walking and articular and meniscal cartilage composition in young, healthy subjects. BACKGROUND Muscle forces affect knee loading during walking, but it is not known if muscle morphology is associated with walking mechanics and cartilage composition in young subjects. METHODS Forty-two knees from 27 young, healthy, active volunteers (age, 20-35 years; body mass index, <28 kg/m2) underwent 3-T magnetic resonance imaging (MRI) and 3-D motion capture. Standard MRI sequences were used for articular and meniscal cartilage T1rho and T2 relaxation times and for quadriceps and hamstrings muscle ACSA. Frontal plane kinetics during the stance phase of walking was calculated. Generalized estimating equation models were used to identify muscle variables that predicted MRI and gait parameters. RESULTS Quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were positively related to frontal plane loading (β = .27-.54, P≤.006), global articular cartilage relaxation times (β = .22-.28, P≤.041), and the medial-lateral ratio of meniscus T1rho relaxation time (β = .26-.36, P≤.049). The medial-lateral quadriceps ACSA ratio was positively related to global meniscus T1rho relaxation times (β = .30, P = .046). CONCLUSION Higher quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were associated with higher frontal plane loading during walking and with articular and meniscal cartilage T1rho and T2 relaxation times. These findings highlight the relationships between different knee tissues and knee mechanics in young, healthy individuals. PMID:24175607

  5. 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.

  6. Effects of toe-out and toe-in gait with varying walking speeds on knee joint mechanics and lower limb energetics.

    PubMed

    Khan, Soobia Saad; Khan, Saad Jawaid; Usman, Juliana

    2017-03-01

    Toe-out/-in gait has been prescribed in reducing knee joint load to medial knee osteoarthritis patients. This study focused on the effects of toe-out/-in at different walking speeds on first peak knee adduction moment (fKAM), second peak KAM (sKAM), knee adduction angular impulse (KAAI), net mechanical work by lower limb as well as joint-level contribution to the total limb work during level walking. Gait analysis of 20 healthy young adults was done walking at pre-defined normal (1.18m/s), slow (0.85m/s) and fast (1.43m/s) walking speeds with straight-toe (natural), toe-out (15°>natural) and toe-in (15°walking speeds (highest at normal speed) while toe-in gait reduced fKAM at all speeds (highest at fast walking speed). Toeing-in reduced KAAI at all speeds while toeing-out affected KAAI only at normal speed. Increasing walking speed generally increased fKAM for all foot positions, but it did not affect sKAM considerably. Slowing down the speed, increased KAAI significantly at all foot positions except for toe-in. At slow walking speed, hip and knee joints were found to be major energy contributors for toe-in and toe-out respectively. At higher walking speeds, these contributions were switched. The ankle joint remained unaffected by changing walking speeds and foot progression angles. Toe-out/-in gait modifications affected knee joint kinetics and lower limb energetics at all walking speeds. However, their effects were inconsistent at different speeds. Therefore, walking speed should be taken into account when prescribing toe-out/-in gait.

  7. Human bipedal instability in tree canopy environments is reduced by "light touch" fingertip support.

    PubMed

    Johannsen, L; Coward, S R L; Martin, G R; Wing, A M; Casteren, A van; Sellers, W I; Ennos, A R; Crompton, R H; Thorpe, S K S

    2017-04-25

    Whether tree canopy habitats played a sustained role in the ecology of ancestral bipedal hominins is unresolved. Some argue that arboreal bipedalism was prohibitively risky for hominins whose increasingly modern anatomy prevented them from gripping branches with their feet. Balancing on two legs is indeed challenging for humans under optimal conditions let alone in forest canopy, which is physically and visually highly dynamic. Here we quantify the impact of forest canopy characteristics on postural stability in humans. Viewing a movie of swaying branches while standing on a branch-like bouncy springboard destabilised the participants as much as wearing a blindfold. However "light touch", a sensorimotor strategy based on light fingertip support, significantly enhanced their balance and lowered their thigh muscle activity by up to 30%. This demonstrates how a light touch strategy could have been central to our ancestor's ability to avoid falls and reduce the mechanical and metabolic cost of arboreal feeding and movement. Our results may also indicate that some adaptations in the hand that facilitated continued access to forest canopy may have complemented, rather than opposed, adaptations that facilitated precise manipulation and tool use.

  8. Fossils, feet and the evolution of human bipedal locomotion

    PubMed Central

    Harcourt-Smith, W E H; Aiello, L C

    2004-01-01

    We review the evolution of human bipedal locomotion with a particular emphasis on the evolution of the foot. We begin in the early twentieth century and focus particularly on hypotheses of an ape-like ancestor for humans and human bipedal locomotion put forward by a succession of Gregory, Keith, Morton and Schultz. We give consideration to Morton's (1935) synthesis of foot evolution, in which he argues that the foot of the common ancestor of modern humans and the African apes would be intermediate between the foot of Pan and Hylobates whereas the foot of a hypothetical early hominin would be intermediate between that of a gorilla and a modern human. From this base rooted in comparative anatomy of living primates we trace changing ideas about the evolution of human bipedalism as increasing amounts of postcranial fossil material were discovered. Attention is given to the work of John Napier and John Robinson who were pioneers in the interpretation of Plio-Pleistocene hominin skeletons in the 1960s. This is the period when the wealth of evidence from the southern African australopithecine sites was beginning to be appreciated and Olduvai Gorge was revealing its first evidence for Homo habilis. In more recent years, the discovery of the Laetoli footprint trail, the AL 288-1 (A. afarensis) skeleton, the wealth of postcranial material from Koobi Fora, the Nariokotome Homo ergaster skeleton, Little Foot (Stw 573) from Sterkfontein in South Africa, and more recently tantalizing material assigned to the new and very early taxa Orrorin tugenensis, Ardipithecus ramidus and Sahelanthropus tchadensis has fuelled debate and speculation. The varying interpretations based on this material, together with changing theoretical insights and analytical approaches, is discussed and assessed in the context of new three-dimensional morphometric analyses of australopithecine and Homo foot bones, suggesting that there may have been greater diversity in human bipedalism in the earlier phases

  9. Fossils, feet and the evolution of human bipedal locomotion.

    PubMed

    Harcourt-Smith, W E H; Aiello, L C

    2004-05-01

    We review the evolution of human bipedal locomotion with a particular emphasis on the evolution of the foot. We begin in the early twentieth century and focus particularly on hypotheses of an ape-like ancestor for humans and human bipedal locomotion put forward by a succession of Gregory, Keith, Morton and Schultz. We give consideration to Morton's (1935) synthesis of foot evolution, in which he argues that the foot of the common ancestor of modern humans and the African apes would be intermediate between the foot of Pan and Hylobates whereas the foot of a hypothetical early hominin would be intermediate between that of a gorilla and a modern human. From this base rooted in comparative anatomy of living primates we trace changing ideas about the evolution of human bipedalism as increasing amounts of postcranial fossil material were discovered. Attention is given to the work of John Napier and John Robinson who were pioneers in the interpretation of Plio-Pleistocene hominin skeletons in the 1960s. This is the period when the wealth of evidence from the southern African australopithecine sites was beginning to be appreciated and Olduvai Gorge was revealing its first evidence for Homo habilis. In more recent years, the discovery of the Laetoli footprint trail, the AL 288-1 (A. afarensis) skeleton, the wealth of postcranial material from Koobi Fora, the Nariokotome Homo ergaster skeleton, Little Foot (Stw 573) from Sterkfontein in South Africa, and more recently tantalizing material assigned to the new and very early taxa Orrorin tugenensis, Ardipithecus ramidus and Sahelanthropus tchadensis has fuelled debate and speculation. The varying interpretations based on this material, together with changing theoretical insights and analytical approaches, is discussed and assessed in the context of new three-dimensional morphometric analyses of australopithecine and Homo foot bones, suggesting that there may have been greater diversity in human bipedalism in the earlier phases

  10. In search of the pitching momentum that enables some lizards to sustain bipedal running at constant speeds

    PubMed Central

    Van Wassenbergh, Sam; Aerts, Peter

    2013-01-01

    The forelimbs of lizards are often lifted from the ground when they start sprinting. Previous research pointed out that this is a consequence of the propulsive forces from the hindlimbs. However, despite forward acceleration being hypothesized as necessary to lift the head, trunk and forelimbs, some species of agamids, teiids and basilisks sustain running in a bipedal posture at a constant speed for a relatively long time. Biomechanical modelling of steady bipedal running in the agamid Ctenophorus cristatus now shows that a combination of three mechanisms must be present to generate the angular impulse needed to cancel or oppose the effect of gravity. First, the trunk must be lifted significantly to displace the centre of mass more towards the hip joint. Second, the nose-up pitching moment resulting from aerodynamic forces exerted at the lizard's surface must be taken into account. Third, the vertical ground-reaction forces at the hindlimb must show a certain degree of temporal asymmetry with higher forces closer to the instant of initial foot contact. Such asymmetrical vertical ground-reaction force profiles, which differ from the classical spring-mass model of bipedal running, seem inherent to the windmilling, splayed-legged running style of lizards. PMID:23658116

  11. In search of the pitching momentum that enables some lizards to sustain bipedal running at constant speeds.

    PubMed

    Van Wassenbergh, Sam; Aerts, Peter

    2013-07-06

    The forelimbs of lizards are often lifted from the ground when they start sprinting. Previous research pointed out that this is a consequence of the propulsive forces from the hindlimbs. However, despite forward acceleration being hypothesized as necessary to lift the head, trunk and forelimbs, some species of agamids, teiids and basilisks sustain running in a bipedal posture at a constant speed for a relatively long time. Biomechanical modelling of steady bipedal running in the agamid Ctenophorus cristatus now shows that a combination of three mechanisms must be present to generate the angular impulse needed to cancel or oppose the effect of gravity. First, the trunk must be lifted significantly to displace the centre of mass more towards the hip joint. Second, the nose-up pitching moment resulting from aerodynamic forces exerted at the lizard's surface must be taken into account. Third, the vertical ground-reaction forces at the hindlimb must show a certain degree of temporal asymmetry with higher forces closer to the instant of initial foot contact. Such asymmetrical vertical ground-reaction force profiles, which differ from the classical spring-mass model of bipedal running, seem inherent to the windmilling, splayed-legged running style of lizards.

  12. Early, Prehospital Activation of the Walking Blood Bank Based on Mechanism of Injury Improves Time to Fresh Whole Blood Transfusion.

    PubMed

    Bassett, Aaron K; Auten, Jonathan D; Zieber, Tara J; Lunceford, Nicole L

    2016-01-01

    Balanced component therapy (BCT) remains the mainstay in trauma resuscitation of the critically battle injured. In austere medical environments, access to packed red blood cells, apheresis platelets, and fresh frozen plasma is often limited. Transfusion of warm, fresh whole blood (FWB) has been used to augment limited access to full BCT in these settings. The main limitation of FWB is that it is not readily available for transfusion on casualty arrival. This small case series evaluates the impact early, mechanism-of-injury (MOI)-based, preactivation of the walking blood bank has on time to transfusion. We report an average time of 18 minutes to FWB transfusion from patient arrival. Early activation of the walking blood bank based on prehospital MOI may further reduce the time to FWB transfusion. 2016.

  13. Contributions of knee swing initiation and ankle plantar flexion to the walking mechanics of amputees using a powered prosthesis.

    PubMed

    Ingraham, Kimberly A; Fey, Nicholas P; Simon, Ann M; Hargrove, Levi J

    2014-01-01

    Recently developed powered prostheses are capable of producing near-physiological joint torque at the knee and/or ankle joints. Based on previous studies of biological joint impedance and the mechanics of able-bodied gait, an impedance-based controller has been developed for a powered knee and ankle prosthesis that integrates knee swing initiation and powered plantar flexion in late stance with increasing ankle stiffness throughout stance. In this study, five prosthesis configuration conditions were tested to investigate the individual contributions of each sub-strategy to the overall walking mechanics of four unilateral transfemoral amputees as they completed a clinical 10-m walk test using a powered knee and ankle prosthesis. The baseline condition featured constant ankle stiffness and no swing initiation or powered plantar flexion. The four remaining conditions featured knee swing initiation alone (SI) or in combination with powered plantar flexion (SI+PF), increasing ankle stiffness (SI+IK), or both (SI+PF+IK). Self-selected walking speed did not significantly change between conditions, although subjects tended to walk the slowest in the baseline condition compared to conditions with swing initiation. The addition of powered plantar flexion resulted in significantly higher ankle power generation in late stance irrespective of ankle stiffness. The inclusion of swing initiation resulted in a significantly more flexed knee at toe off and a significantly higher average extensor knee torque following toe off. Identifying individual contributions of intrinsic control strategies to prosthesis biomechanics could help inform the refinement of impedance-based prosthesis controllers and simplify future designs of prostheses and lower-limb assistive devices alike.

  14. Systematic variation of prosthetic foot spring affects center-of-mass mechanics and metabolic cost during walking.

    PubMed

    Zelik, Karl E; Collins, Steven H; Adamczyk, Peter G; Segal, Ava D; Klute, Glenn K; Morgenroth, David C; Hahn, Michael E; Orendurff, Michael S; Czerniecki, Joseph M; Kuo, Arthur D

    2011-08-01

    Lower-limb amputees expend more energy to walk than non-amputees and have an elevated risk of secondary disabilities. Insufficient push-off by the prosthetic foot may be a contributing factor. We aimed to systematically study the effect of prosthetic foot mechanics on gait, to gain insight into fundamental prosthetic design principles. We varied a single parameter in isolation, the energy-storing spring in a prototype prosthetic foot, the controlled energy storage and return (CESR) foot, and observed the effect on gait. Subjects walked on the CESR foot with three different springs. We performed parallel studies on amputees and on non-amputees wearing prosthetic simulators. In both groups, spring characteristics similarly affected ankle and body center-of-mass (COM) mechanics and metabolic cost. Softer springs led to greater energy storage, energy return, and prosthetic limb COM push-off work. But metabolic energy expenditure was lowest with a spring of intermediate stiffness, suggesting biomechanical disadvantages to the softest spring despite its greater push-off. Disadvantages of the softest spring may include excessive heel displacements and COM collision losses. We also observed some differences in joint kinetics between amputees and non-amputees walking on the prototype foot. During prosthetic push-off, amputees exhibited reduced energy transfer from the prosthesis to the COM along with increased hip work, perhaps due to greater energy dissipation at the knee. Nevertheless, the results indicate that spring compliance can contribute to push-off, but with biomechanical trade-offs that limit the degree to which greater push-off might improve walking economy. © 2011 IEEE

  15. Systematic variation of prosthetic foot spring affects center-of-mass mechanics and metabolic cost during walking

    PubMed Central

    Zelik, Karl E.; Collins, Steven H.; Adamczyk, Peter G.; Segal, Ava D.; Klute, Glenn K.; Morgenroth, David C.; Hahn, Michael E.; Orendurff, Michael S.; Czerniecki, Joseph M.; Kuo, Arthur D.

    2014-01-01

    Lower-limb amputees expend more energy to walk than non-amputees and have an elevated risk of secondary disabilities. Insufficient push-off by the prosthetic foot may be a contributing factor. We aimed to systematically study the effect of prosthetic foot mechanics on gait, to gain insight into fundamental prosthetic design principles. We varied a single parameter in isolation, the energy-storing spring in a prototype prosthetic foot, the Controlled Energy Storage and Return (CESR) foot, and observed the effect on gait. Subjects walked on the CESR foot with three different springs. We performed parallel studies on amputees and on non-amputees wearing prosthetic simulators. In both groups, spring characteristics similarly affected ankle and body center-of-mass (COM) mechanics and metabolic cost. Softer springs led to greater energy storage, energy return and prosthetic limb COM push-off work. But metabolic energy expenditure was lowest with a spring of intermediate stiffness, suggesting biomechanical disadvantages to the softest spring despite its greater push-off. Disadvantages of the softest spring may include excessive heel displacements and COM collision losses. We also observed some differences in joint kinetics between amputees and non-amputees walking on the prototype foot. During prosthetic push-off, amputees exhibited reduced energy transfer from the prosthesis to the COM along with increased hip work, perhaps due to greater energy dissipation at the knee. Nevertheless, the results indicate that spring compliance can contribute to push-off, but with biomechanical trade-offs that limit the degree to which greater push-off might improve walking economy. PMID:21708509

  16. [Bipedalism in birds, a determining feature for their adaptive success].

    PubMed

    Abourachid, Anick

    2006-01-01

    The birds are flying animals but they are also basically bipeds. The theropod dinosaurs, precursors of the birds, were already cursorial bipeds. Because the body structure was modelled by aerodynamical constraints during the evolution, all birds, even those that do not fly anymore, share a typical avian body shape. The osteological differences between birds are more adjustments than deep disruptions. Nevertheless, the birds are very diversified in their way of life and habitat. Yet, the hind limbs of the birds are surprisingly efficient in many manners, such as taking off, landing, swimming and walking. The limb structures adaptability to the various tasks require different mechanical fitness or device such as shock absorber during landing, or thrusters during tacking off. Moreover, almost all birds can walk, even if they have another locomotor specialization, as swimming or flying. Depending on the specialization, the gait features of the walk and the kinematics pattern are slightly modified. The functional adaptability of their hind limb structure may be a key to the evolutive success of the birds.

  17. A simple model to estimate plantarflexor muscle-tendon mechanics and energetics during walking with elastic ankle exoskeletons

    PubMed Central

    Sawicki, Gregory S.; Khan, Nabil S.

    2016-01-01

    Goal A recent experiment demonstrated that when humans wear unpowered elastic ankle exoskeletons with intermediate spring stiffness they can reduce their metabolic energy cost to walk by ~7%. Springs that are too compliant or too stiff have little benefit. The purpose of this study was to use modeling and simulation to explore the muscle-level mechanisms for the ‘sweet-spot’ in stiffness during exoskeleton assisted walking. Methods We developed a simple lumped, uniarticular musculoskeletal model of the plantarflexors operating in parallel with an elastic ‘exo-tendon’. Using an inverse approach with constrained kinematics and kinetics, we rapidly simulated human walking over a range of exoskeleton stiffness values and examined the underlying neuromechanics and energetics of the biological plantarflexors. Results Stiffer ankle exoskeleton springs resulted in larger decreases in plantarflexor muscle forces, activations and metabolic energy consumption. However, in the process of unloading the compliant biological muscle-tendon unit (MTU), the muscle fascicles (CE) experienced larger excursions that negatively impacted series elastic element (SEE) recoil that is characteristic of a tuned ‘catapult mechanism’. Conclusion The combination of disrupted muscle-tendon dynamics and the need to produce compensatory forces/moments to maintain overall net ankle moment invariance could explain the ‘sweet spot’ in metabolic performance at intermediate ankle exoskeleton stiffness. Future work will aim to provide experimental evidence to support the model predictions presented here using ultrasound imaging of muscle-level dynamics during walking with elastic ankle exoskeletons. Significance Engineers must account for the muscle-level effects of exoskeleton designs in order to achieve maximal performance objectives. PMID:26485350

  18. [Walking abnormalities in children].

    PubMed

    Segawa, Masaya

    2010-11-01

    Walking is a spontaneous movement termed locomotion that is promoted by activation of antigravity muscles by serotonergic (5HT) neurons. Development of antigravity activity follows 3 developmental epochs of the sleep-wake (S-W) cycle and is modulated by particular 5HT neurons in each epoch. Activation of antigravity activities occurs in the first epoch (around the age of 3 to 4 months) as restriction of atonia in rapid eye movement (REM) stage and development of circadian S-W cycle. These activities strengthen in the second epoch, with modulation of day-time sleep and induction of crawling around the age of 8 months and induction of walking by 1 year. Around the age of 1 year 6 months, absence of guarded walking and interlimb cordination is observed along with modulation of day-time sleep to once in the afternoon. Bipedal walking in upright position occurs in the third epoch, with development of a biphasic S-W cycle by the age of 4-5 years. Patients with infantile autism (IA), Rett syndrome (RTT), or Tourette syndrome (TS) show failure in the development of the first, second, or third epoch, respectively. Patients with IA fail to develop interlimb coordination; those with RTT, crawling and walking; and those with TS, walking in upright posture. Basic pathophysiology underlying these condition is failure in restricting atonia in REM stage; this induces dysfunction of the pedunculopontine nucleus and consequently dys- or hypofunction of the dopamine (DA) neurons. DA hypofunction in the developing brain, associated with compensatory upward regulation of the DA receptors causes psychobehavioral disorders in infancy (IA), failure in synaptogenesis in the frontal cortex and functional development of the motor and associate cortexes in late infancy through the basal ganglia (RTT), and failure in functional development of the prefrontal cortex through the basal ganglia (TS). Further, locomotion failure in early childhood causes failure in development of functional

  19. Predictive Walking-Age Health Analyzer.

    PubMed

    Mandal, Priyanka; Tank, Krishna; Monday, Tapas; Chen, Chih-Hung; Deen, M Jamal

    2017-02-09

    A simple, low-power and wearable health analyzer for early identification and management of some diseases is presented. To achieve this goal, we propose a walking pattern analysis system that uses features such as speed, energy, turn ratio, and bipedal behavior to characterize and classify individuals in distinct walking-ages. A database is constructed from 74 healthy young adults in the age range of 18 to 60 years using the combination of inertial signals from an accelerometer and a gyroscope on a level path including turns. An efficient advanced signal decomposition method called improved complete ensemble empirical mode decomposition with adaptive noise (Improved CEEMDAN) was used for feature extraction. Analyses show that the gait of healthy able-bodied individuals exhibits a natural bipedal asymmetry to a certain level depending on the activity-type and age, which relate to individual's functional attributes rather than pathological gait. The analysis of turn ratio, a measure of activity-transition9 energy change and stability, indicated turning to be less locally stable than straight-line walking making it a more reliable measure for determining falls and other health issues. Extracted features were used to analyze two distinct walking-age groups of the healthy young adults based on their walking pattern, classifying 18-45 years old individuals in one group and 46-60 years old in the other group. Our proposed simple, inexpensive walking analyzer system can be easily used as an ambulatory screening tool by clinicians to identify at risk population at the early onset of some diseases.

  20. Locomotion: Why We Walk the Way We Walk.

    PubMed

    Bertram, John E A

    2015-09-21

    The way we walk determines the energetic investment needed. Humans spontaneously alter their walking style to exploit energetic opportunities. New research demonstrates the sensitivity and timing of this optimization and opens the door to discovering the underlying mechanisms.

  1. Neural Computation Scheme of Compound Control: Tacit Learning for Bipedal Locomotion

    NASA Astrophysics Data System (ADS)

    Shimoda, Shingo; Kimura, Hidenori

    The growing need for controlling complex behaviors of versatile robots working in unpredictable environment has revealed the fundamental limitation of model-based control strategy that requires precise models of robots and environments before their operations. This difficulty is fundamental and has the same root with the well-known frame problem in artificial intelligence. It has been a central long standing issue in advanced robotics, as well as machine intelligence, to find a prospective clue to attack this fundamental difficulty. The general consensus shared by many leading researchers in the related field is that the body plays an important role in acquiring intelligence that can conquer unknowns. In particular, purposeful behaviors emerge during body-environment interactions with the help of an appropriately organized neural computational scheme that can exploit what the environment can afford. Along this line, we propose a new scheme of neural computation based on compound control which represents a typical feature of biological controls. This scheme is based on classical neuron models with local rules that can create macroscopic purposeful behaviors. This scheme is applied to a bipedal robot and generates the rhythm of walking without any model of robot dynamics and environments.

  2. "Far" and "Near" Visual Acuity While Walking and the Collective Contributions of Non-Ocular Mechanisms to Gaze Stabilization

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; vanEmmerik, Richard E. A.; Bloomberg, Jacob J.

    2006-01-01

    Gaze stabilization was quantified in subjects (n=11) as they walked on a motorized treadmill (1.8 m/s) and viewed visual targets at two viewing distances. A "far" target was positioned at 4 m (FAR) in front of the subject and the "near" target was placed at a distance of 0.5 m (NEAR). A direct measure of visual acuity was used to assess the overall effectiveness of the gaze stabilization system. The contributions of nonocular mechanisms to the gaze goal were also quantified using a measure of the distance between the subject and point in space where fixation of the visual target would require the least eye movement amplitude (i.e. the head fixation distance (HFD)). Kinematic variables mirrored those of previous investigations with the vertical trunk translation and head pitch signals, and the lateral translation and head yaw signals maintaining what appear as antiphase relationships. However, an investigation of the temporal relationships between the maxima and minima of the vertical translation and head pitch signals show that while the maximum in vertical translation occurs at the point of the minimum head pitch signal, the inverse is not true. The maximum in the head pitch signal lags the vertical translation minimum by an average of greater than 12 percent of the step cycle time. Three HFD measures, one each for data in the sagittal and transverse planes, and one that combined the movements from both planes, all revealed changes between the FAR and NEAR target viewing conditions. This reorganization of the nonocular degrees of freedom while walking was consistent with a strategy to reduce the magnitude of the eye movements required when viewing the NEAR target. Despite this reorganization, acuity measures show that image stabilization is not occurring while walking and viewing the NEAR target. Group means indicate that visual acuity is not affected while walking in the FAR condition, but a decrement of 0.15 logMAR (i.e. 1.5 eye chart lines) exists between the

  3. The evolution of bipedal running in lizards suggests a consequential origin may be exploited in later lineages.

    PubMed

    Clemente, Christofer J

    2014-08-01

    The origin of bipedal locomotion in lizards is unclear. Modeling studies have suggested that bipedalism may be an exaptation, a byproduct of features originally designed to increase maneuverability, which were only later exploited. Measurement of the body center of mass (BCOM) in 124 species of lizards confirms a significant rearward shift among bipedal lineages. Further racetrack trials showed a significant acceleration threshold between bipedal and quadrupedal runs. These suggest good general support for a passive bipedal model, in which the combination of these features lead to passive lifting of the front of the body. However, variation in morphology could only account for 56% of the variation in acceleration thresholds, suggesting that dynamics have a significant influence on bipedalism. Deviation from the passive bipedal model was compared with node age, supporting an increase in the influence of dynamics over time. Together, these results show that bipedalism may have first arisen as a consequence of acceleration and a rearward shift in the BCOM, but subsequent linages have exploited this consequence to become bipedal more often, suggesting that bipedalism in lizards may convey some advantage. Exploitation of bipedalism was also associated with increased rates of phenotypic diversity, suggesting exploiting bipedalism may promote adaptive radiation. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  4. The influence of energy storage and return foot stiffness on walking mechanics and muscle activity in below-knee amputees.

    PubMed

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

    2011-12-01

    Below-knee amputees commonly experience asymmetrical gait patterns and develop comorbidities in their intact and residual legs. Carbon fiber prosthetic feet have been developed to minimize these asymmetries by utilizing elastic energy storage and return to provide body support, forward propulsion and leg swing initiation. However, how prosthetic foot stiffness influences walking characteristics is not well-understood. The purpose of this study was to identify the influence of foot stiffness on kinematics, kinetics, muscle activity, prosthetic energy storage and return, and mechanical efficiency during amputee walking. A comprehensive biomechanical analysis was performed on 12 unilateral below-knee amputees. Subjects walked overground at 1.2 m/s with three prosthetic feet of varying keel and heel stiffness levels, which were created using additive manufacturing. As stiffness decreased, peak residual and intact leg ankle angles and residual leg knee flexion angle increased. The residual and intact leg braking ground reaction forces and knee extensor moments, residual leg vastus and gluteus medius activity, and intact leg vastus and rectus femoris activity also increased. The second vertical ground reaction force peak and hamstring activity in the residual leg and first vertical ground reaction force peak in the intact leg decreased. In addition, prosthetic energy storage and return increased and mechanical efficiency decreased as stiffness decreased. Decreasing foot stiffness can increase prosthesis range of motion, mid-stance energy storage and late-stance energy return, but the net contributions to forward propulsion and swing initiation may be limited as additional muscle activity to provide body support becomes necessary. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. A novel robot for imposing perturbations during overground walking: mechanism, control and normative stepping responses.

    PubMed

    Olenšek, Andrej; Zadravec, Matjaž; Matjačić, Zlatko

    2016-06-11

    The most common approach to studying dynamic balance during walking is by applying perturbations. Previous studies that investigated dynamic balance responses predominantly focused on applying perturbations in frontal plane while walking on treadmill. The goal of our work was to develop balance assessment robot (BAR) that can be used during overground walking and to assess normative balance responses to perturbations in transversal plane in a group of neurologically healthy individuals. BAR provides three passive degrees of freedom (DoF) and three actuated DoF in pelvis that are admittance-controlled in such a way that the natural movement of pelvis is not significantly affected. In this study BAR was used to assess normative balance responses in neurologically healthy individuals by applying linear perturbations in frontal and sagittal planes and angular perturbations in transversal plane of pelvis. One way repeated measure ANOVA was used to statistically evaluate the effect of selected perturbations on stepping responses. Standard deviations of assessed responses were similar in unperturbed and perturbed walking. Perturbations in frontal direction evoked substantial pelvis displacement and caused statistically significant effect on step length, step width and step time. Likewise, perturbations in sagittal plane also caused statistically significant effect on step length, step width and step time but with less explicit impact on pelvis movement in frontal plane. On the other hand, except from substantial pelvis rotation angular perturbations did not have substantial effect on pelvis movement in frontal and sagittal planes while statistically significant effect was noted only in step length and step width after perturbation in clockwise direction. Results indicate that the proposed device can repeatedly reproduce similar experimental conditions. Results also suggest that "stepping strategy" is the dominant strategy for coping with perturbations in frontal plane

  6. Walking cavity solitons

    SciTech Connect

    Skryabin, Dmitry V.; Champneys, Alan R.

    2001-06-01

    A family of walking solitons is obtained for the degenerate optical parametric oscillator below threshold. The loss-driven mechanism of velocity selection for these structures is described analytically and numerically. Our approach is based on understanding the role played by the field momentum and generic symmetry properties and, therefore, it can be easily generalized to other dissipative multicomponent models with walk off.

  7. Comparison of inverse-dynamics musculo-skeletal models of AL 288-1 Australopithecus afarensis and KNM-WT 15000 Homo ergaster to modern humans, with implications for the evolution of bipedalism.

    PubMed

    Wang, Weijie; Crompton, Robin H; Carey, Tanya S; Günther, Michael M; Li, Yu; Savage, Russell; Sellers, Williams I

    2004-12-01

    Size and proportions of the postcranial skeleton differ markedly between Australopithecus afarensis and Homo ergaster, and between the latter and modern Homo sapiens. This study uses computer simulations of gait in models derived from the best-known skeletons of these species (AL 288-1, Australopithecus afarensis, 3.18 million year ago) and KNM-WT 15000 (Homo ergaster, 1.5-1.8 million year ago) compared to models of adult human males and females, to estimate the required muscle power during bipedal walking, and to compare this with those in modern humans. Skeletal measurements were carried out on a cast of KNM-WT 15000, but for AL 288-1 were taken from the literature. Muscle attachments were applied to the models based on their position relative to the bone in modern humans. Joint motions and moments from experiments on human walking were input into the models to calculate muscle stress and power. The models were tested in erect walking and 'bent-hip bent-knee' gait. Calculated muscle forces were verified against EMG activity phases from experimental data, with reference to reasonable activation/force delays. Calculated muscle powers are reasonably comparable to experimentally derived metabolic values from the literature, given likely values for muscle efficiency. The results show that: 1) if evaluated by the power expenditure per unit of mass (W/kg) in walking, AL 288-1 and KNM-WT 15000 would need similar power to modern humans; however, 2) with distance-specific parameters as the criteria, AL 288-1 would require to expend relatively more muscle power (W/kg.m(-1)) in comparison to modern humans. The results imply that in the evolution of bipedalism, body proportions, for example those of KNM-WT 15000, may have evolved to obtain an effective application of muscle power to bipedal walking over a long distance, or at high speed.

  8. Laughter as an approach to vocal evolution: The bipedal theory.

    PubMed

    Provine, Robert R

    2017-02-01

    Laughter is a simple, stereotyped, innate, human play vocalization that is ideal for the study of vocal evolution. The basic approach of describing the act of laughter and when we do it has revealed a variety of phenomena of social, linguistic, and neurological significance. Findings include the acoustic structure of laughter, the minimal voluntary control of laughter, the punctuation effect (which describes the placement of laughter in conversation and indicates the dominance of speech over laughter), and the role of laughter in human matching and mating. Especially notable is the use of laughter to discover why humans can speak and other apes cannot. Quadrupeds, including our primate ancestors, have a 1:1 relation between breathing and stride because their thorax must absorb forelimb impacts during running. The direct link between breathing and locomotion limits vocalizations to short, simple utterances, such as the characteristic panting chimpanzee laugh (one sound per inward or outward breath). The evolution of bipedal locomotion freed the respiration system of its support function during running, permitting greater breath control and the selection for human-type laughter (a parsed exhalation), and subsequently the virtuosic, sustained, expiratory vocalization of speech. This is the basis of the bipedal theory of speech evolution.

  9. Climbing, brachiation, and terrestrial quadrupedalism: historical precursors of hominid bipedalism.

    PubMed

    Gebo, D L

    1996-09-01

    The vertical-climbing account of the evolution of locomotor behavior and morphology in hominid ancestry is reexamined in light of recent behavioral, anatomical, and paleontological findings and a more firmly established phylogeny for the living apes. The behavioral record shows that African apes, when arboreal, are good vertical climbers, and that locomotion during traveling best separates the living apes into brachiators (gibbons), scrambling/ climbing/brachiators (orangutans), and terrestrial quadrupeds (gorillas and chimpanzees). The paleontological record documents frequent climbing as an ancestral catarrhine ability, while a reassessment of the morphology of the torso and forelimb in living apes and Atelini suggests that their shared unique morphological pattern is best explained by brachiation and forelimb suspensory positional behavior. Further, evidence from the hand and foot points to a terrestrial quadrupedal phase in hominoid evolution prior to the adoption of bipedalism. The evolution of positional behavior from early hominoids to hominids appears to have begun with an arboreal quadrupedal-climbing phase and proceeded though an orthograde, brachiating, forelimb-suspensory phase, which was in turn followed by arboreal and terrestrial quadrupedal phases prior to the advent of hominid bipedality. The thesis that protohominids climbed down from the trees to become terrestrial bipeds needs to be reexamined in light of a potentially long history of terrestriality in the ancestral protohominid.

  10. A Control Framework for Anthropomorphic Biped Walking Based on Stabilizing Feedforward Trajectories.

    PubMed

    Rezazadeh, Siavash; Gregg, Robert D

    2016-10-01

    Although dynamic walking methods have had notable successes in control of bipedal robots in the recent years, still most of the humanoid robots rely on quasi-static Zero Moment Point controllers. This work is an attempt to design a highly stable controller for dynamic walking of a human-like model which can be used both for control of humanoid robots and prosthetic legs. The method is based on using time-based trajectories that can induce a highly stable limit cycle to the bipedal robot. The time-based nature of the controller motivates its use to entrain a model of an amputee walking, which can potentially lead to a better coordination of the interaction between the prosthesis and the human. The simulations demonstrate the stability of the controller and its robustness against external perturbations.

  11. A Control Framework for Anthropomorphic Biped Walking Based on Stabilizing Feedforward Trajectories

    PubMed Central

    Rezazadeh, Siavash; Gregg, Robert D.

    2016-01-01

    Although dynamic walking methods have had notable successes in control of bipedal robots in the recent years, still most of the humanoid robots rely on quasi-static Zero Moment Point controllers. This work is an attempt to design a highly stable controller for dynamic walking of a human-like model which can be used both for control of humanoid robots and prosthetic legs. The method is based on using time-based trajectories that can induce a highly stable limit cycle to the bipedal robot. The time-based nature of the controller motivates its use to entrain a model of an amputee walking, which can potentially lead to a better coordination of the interaction between the prosthesis and the human. The simulations demonstrate the stability of the controller and its robustness against external perturbations. PMID:28239504

  12. Influence of patellar position on the knee extensor mechanism in normal and crouched walking.

    PubMed

    Lenhart, Rachel L; Brandon, Scott C E; Smith, Colin R; Novacheck, Tom F; Schwartz, Michael H; Thelen, Darryl G

    2017-01-25

    Patella alta is common in cerebral palsy, especially in patients with crouch gait. Correction of patella alta has been advocated in the treatment of crouch, however the appropriate degree of correction and the implications for knee extensor function remain unclear. Therefore, the goal of this study was to assess the impact of patellar position on quadriceps and patellar tendon forces during normal and crouch gait. To this end, a lower extremity musculoskeletal model with a novel 12 degree of freedom knee joint was used to simulate normal gait in a healthy child, as well as mild (23 deg min knee flexion in stance), moderate (41 deg), and severe (67 deg) crouch gait in three children with cerebral palsy. The simulations revealed that quadriceps and patellar tendon forces increase dramatically with crouch, and are modulated by patellar position. For example with a normal patellar tendon position, peak patellar tendon forces were 0.7 times body weight in normal walking, but reached 2.2, 3.2 and 5.4 times body weight in mild, moderate and severe crouch. Moderate patella alta acted to reduce quadriceps and patellar tendon loads in crouch gait, due to an enhancement of the patellar tendon moment arms with alta in a flexed knee. In contrast, patella baja reduced the patellar tendon moment arm in a flexed knee and thus induced an increase in the patellar tendon loads needed to walk in crouch. Functionally, these results suggest that patella baja could also compromise knee extensor function for other flexed knee activities such as chair rise and stair climbing. The findings are important to consider when using surgical approaches for correcting patella alta in children who exhibit crouch gait patterns. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Multiple phylogenetically distinct events shaped the evolution of limb skeletal morphologies associated with bipedalism in the jerboas

    PubMed Central

    Moore, Talia Y.; Organ, Chris L.; Edwards, Scott V.; Biewener, Andrew A.; Tabin, Clifford J.; Jenkins, Farish A.; Cooper, Kimberly L.

    2016-01-01

    SUMMARY Recent rapid advances in experimental biology have expanded the opportunity for interdisciplinary investigations of the evolution of form and function in non-traditional model species. However, historical divisions of philosophy and methodology between evolutionary/organismal biologists and developmental geneticists often preclude an effective merging of disciplines. In an effort to overcome these divisions, we take advantage of the extraordinary morphological diversity of the rodent superfamily Dipodoidea, including the bipedal jerboas, to experimentally study the developmental mechanisms and biomechanical performance of a remarkably divergent limb structure. Here, we place multiple limb character states in a locomotor and phylogenetic context. While obligate bipedalism arose once in the ancestor of extant jerboas, we find that digit loss, metatarsal fusion, between limb proportions, and within hindlimb proportions all evolved independently of one another. Digit loss occurred three times through at least two distinct developmental mechanisms, and elongation of the hindlimb relative to the forelimb is not simply due to growth mechanisms that change proportions within the hindlimb. Furthermore, we find strong evidence for punctuated evolution of allometric scaling of hindlimb elements during the radiation of Dipodoidea. Our work demonstrates the value of leveraging the evolutionary history of a clade to establish criteria for identifying the developmental genetic mechanisms of morphological diversification. PMID:26455300

  14. Multiple phylogenetically distinct events shaped the evolution of limb skeletal morphologies associated with bipedalism in the jerboas.

    PubMed

    Moore, Talia Y; Organ, Chris L; Edwards, Scott V; Biewener, Andrew A; Tabin, Clifford J; Jenkins, Farish A; Cooper, Kimberly L

    2015-11-02

    Recent rapid advances in experimental biology have expanded the opportunity for interdisciplinary investigations of the evolution of form and function in non-traditional model species. However, historical divisions of philosophy and methodology between evolutionary/organismal biologists and developmental geneticists often preclude an effective merging of disciplines. In an effort to overcome these divisions, we take advantage of the extraordinary morphological diversity of the rodent superfamily Dipodoidea, including the bipedal jerboas, to experimentally study the developmental mechanisms and biomechanical performance of a remarkably divergent limb structure. Here, we place multiple limb character states in a locomotor and phylogenetic context. Whereas obligate bipedalism arose just once in the ancestor of extant jerboas, we find that digit loss, metatarsal fusion, between-limb proportions, and within-hindlimb proportions all evolved independently of one another. Digit loss occurred three times through at least two distinct developmental mechanisms, and elongation of the hindlimb relative to the forelimb is not simply due to growth mechanisms that change proportions within the hindlimb. Furthermore, we find strong evidence for punctuated evolution of allometric scaling of hindlimb elements during the radiation of Dipodoidea. Our work demonstrates the value of leveraging the evolutionary history of a clade to establish criteria for identifying the developmental genetic mechanisms of morphological diversification.

  15. The evolution of bipedalism in jerboas (rodentia: Dipodoidea): origin in humid and forested environments.

    PubMed

    Wu, Shaoyuan; Zhang, Fuchun; Edwards, Scott V; Wu, Wenyu; Ye, Jie; Bi, Shundong; Ni, Xijun; Quan, Cheng; Meng, Jin; Organ, Chris L

    2014-07-01

    Mammalian bipedalism has long been thought to have arisen in response to arid and open environments. Here, we tested whether bipedalism coevolved with environmental changes using molecular and paleontological data from the rodent superfamily Dipodoidea and statistical methods for reconstructing ancestral characteristics and past climates. Our results show that the post-Late Miocene aridification exerted selective pressures on tooth shape, but not on leg length of bipedal jerboas. Cheek tooth crown height has increased since the Late Miocene, but the hind limb/head-body length ratios remained stable and high despite the environmental change from humid and forested to arid and open conditions, rather than increasing from low to high as predicted by the arid-bipedalism hypothesis. The decoupling of locomotor and dental character evolution indicates that bipedalism evolved under selective pressure different from that of dental hypsodonty in jerboas. We reconstructed the habitats of early jerboas using floral and faunal data, and the results show that the environments in which bipedalism evolved were forested. Our results suggest that bipedalism evolved as an adaptation to humid woodlands or forests for vertical jumping. Running at high speeds is likely a by-product of selection for jumping, which became advantageous in open environments later on.

  16. Leg mechanics contribute to establishing swing phase trajectories during memory-guided stepping movements in walking cats: a computational analysis

    PubMed Central

    Pearson, Keir G.; Arbabzada, Naik; Gramlich, Rod; Shinya, Masahiro

    2015-01-01

    When quadrupeds stop walking after stepping over a barrier with their forelegs, the memory of barrier height and location is retained for many minutes. This memory is subsequently used to guide hind leg movements over the barrier when walking is resumed. The upslope of the initial trajectory of hind leg paw movements is strongly dependent on the initial location of the paw relative to the barrier. In this study, we have attempted to determine whether mechanical factors contribute significantly in establishing the slope of the paw trajectories by creating a four-link biomechanical model of a cat hind leg and driving this model with a variety of joint-torque profiles, including average torques for a range of initial paw positions relative to the barrier. Torque profiles for individual steps were determined by an inverse dynamic analysis of leg movements in three normal cats. Our study demonstrates that limb mechanics can contribute to establishing the dependency of trajectory slope on the initial position of the paw relative to the barrier. However, an additional contribution of neuronal motor commands was indicated by the fact that the simulated slopes of paw trajectories were significantly less than the observed slopes. A neuronal contribution to the modification of paw trajectories was also revealed by our observations that both the magnitudes of knee flexor muscle EMG bursts and the initial knee flexion torques depended on initial paw position. Previous studies have shown that a shift in paw position prior to stepping over a barrier changes the paw trajectory to be appropriate for the new paw position. Our data indicate that both mechanical and neuronal factors contribute to this updating process, and that any shift in leg position during the delay period modifies the working memory of barrier location. PMID:26441625

  17. Leg mechanics contribute to establishing swing phase trajectories during memory-guided stepping movements in walking cats: a computational analysis.

    PubMed

    Pearson, Keir G; Arbabzada, Naik; Gramlich, Rod; Shinya, Masahiro

    2015-01-01

    When quadrupeds stop walking after stepping over a barrier with their forelegs, the memory of barrier height and location is retained for many minutes. This memory is subsequently used to guide hind leg movements over the barrier when walking is resumed. The upslope of the initial trajectory of hind leg paw movements is strongly dependent on the initial location of the paw relative to the barrier. In this study, we have attempted to determine whether mechanical factors contribute significantly in establishing the slope of the paw trajectories by creating a four-link biomechanical model of a cat hind leg and driving this model with a variety of joint-torque profiles, including average torques for a range of initial paw positions relative to the barrier. Torque profiles for individual steps were determined by an inverse dynamic analysis of leg movements in three normal cats. Our study demonstrates that limb mechanics can contribute to establishing the dependency of trajectory slope on the initial position of the paw relative to the barrier. However, an additional contribution of neuronal motor commands was indicated by the fact that the simulated slopes of paw trajectories were significantly less than the observed slopes. A neuronal contribution to the modification of paw trajectories was also revealed by our observations that both the magnitudes of knee flexor muscle EMG bursts and the initial knee flexion torques depended on initial paw position. Previous studies have shown that a shift in paw position prior to stepping over a barrier changes the paw trajectory to be appropriate for the new paw position. Our data indicate that both mechanical and neuronal factors contribute to this updating process, and that any shift in leg position during the delay period modifies the working memory of barrier location.

  18. The Advantage of Standing Up to Fight and the Evolution of Habitual Bipedalism in Hominins

    PubMed Central

    Carrier, David R.

    2011-01-01

    Background Many quadrupedal species stand bipedally on their hindlimbs to fight. This posture may provide a performance advantage by allowing the forelimbs to strike an opponent with the range of motion that is intrinsic to high-speed running, jumping, rapid braking and turning; the range of motion over which peak force and power can be produced. Methodology/Principal Findings To test the hypothesis that bipedal (i.e., orthograde) posture provides a performance advantage when striking with the forelimbs, I measured the force and energy produced when human subjects struck from “quadrupedal” (i.e., pronograde) and bipedal postures. Downward and upward directed striking energy was measured with a custom designed pendulum transducer. Side and forward strikes were measured with a punching bag instrumented with an accelerometer. When subjects struck downward from a bipedal posture the work was 43.70±12.59% (mean ± S.E.) greater than when they struck from a quadrupedal posture. Similarly, 47.49±17.95% more work was produced when subjects struck upward from a bipedal stance compared to a quadrupedal stance. Importantly, subjects did 229.69±44.19% more work in downward than upward directed strikes. During side and forward strikes the force impulses were 30.12±3.68 and 43.04±9.00% greater from a bipedal posture than a quadrupedal posture, respectively. Conclusions/Significance These results indicate that bipedal posture does provide a performance advantage for striking with the forelimbs. The mating systems of great apes are characterized by intense male-male competition in which conflict is resolved through force or the threat of force. Great apes often fight from bipedal posture, striking with both the fore- and hindlimbs. These observations, plus the findings of this study, suggest that sexual selection contributed to the evolution of habitual bipedalism in hominins. PMID:21611167

  19. A novel elastic force-field to influence mediolateral foot placement during walking.

    PubMed

    Nyberg, Elizabeth; Broadway, Jordan; Finetto, Christian; Dean, Jesse

    2016-12-01

    Bipedal gait can be stabilized through mechanically-appropriate mediolateral foot placement, although this strategy is disrupted in a subset of neurologically injured individuals with balance deficits. The goal of the present work was to develop a device to influence mediolateral foot placement during treadmill walking. We created a novel force-field using a combination of passive elasticity and active control; wires in series with extension springs run parallel to the treadmill belts and can be rapidly repositioned to exert mediolateral forces on the legs of users. This mechanical structure creates a channel-like force landscape that resists displacements of each leg away from its prescribed mediolateral position, producing near-linear effective mediolateral stiffness. The depth of these force-field channels can be predictably controlled by manipulating extension spring initial tension. In human testing, we found that the force-field can effectively "get-out-of-the-way" when desired, closely following the mediolateral leg trajectory with a delay of approximately 110 ms. The force-field can also encourage users to adjust their mediolateral foot placement in order to walk with either narrower or wider steps, without interfering with forward gait progression. Future work will test whether this novel device can help retrain a stable gait pattern in clinical populations.

  20. Potential vascular mechanisms of ramipril induced increases in walking ability in patients with intermittent claudication.

    PubMed

    Ahimastos, Anna A; Latouche, Celine; Natoli, Alaina K; Reddy-luthmoodoo, Medini; Golledge, Jonathan; Kingwell, Bronwyn A

    2014-03-28

    We recently reported that ramipril more than doubled maximum walking times in patients with peripheral artery disease with intermittent claudication. Our aim was to conduct exploratory analyses of the effects of ramipril therapy on circulating biomarkers of angiogenesis/arteriogenesis, thrombosis, inflammation, and leukocyte adhesion in patients with intermittent claudication. One hundred sixty-five patients with intermittent claudication (mean, 65.3 [SD, 6.7] years) were administered ramipril 10 mg per day (n=82) or matching placebo (n=83) for 24 weeks in a randomized, double-blind study. Plasma biomarkers of angiogenesis/arteriogenesis (vascular endothelial growth factor-A, fibroblast growth factor-2), thrombosis (D-dimer, von Willebrand factor, thrombin-antithrombin III), inflammation (high-sensitivity C-reactive protein, osteopontin), and leukocyte adhesion (soluble vascular cell adhesion molecule-1, soluble intracellular adhesion molecule-1) were measured at baseline and 24 weeks. Relative to placebo, ramipril was associated with increases in vascular endothelial growth factor-A by 38% (95% confidence interval [CI], 34%-42%) and fibroblast growth factor-2 by 64% (95% CI, 44-85%; P<0.001 for both), and reductions in D-dimer by 24% (95% CI, -30% to -18%), von Willebrand factor by 22% (95% CI, -35% to -9%), thrombin-antithrombin III by 16% (95% CI, -19% to -13%), high-sensitivity C-reactive protein by 13% (95% CI, -14% to -9%), osteopontin by 12% (95% CI, -14% to -10%), soluble vascular cell adhesion molecule-1 by 14% (95% CI, -18% to -10%), and soluble intracellular adhesion molecule-1 by 15% (95% CI, -17% to -13%; all P<0.001). With the exception of von Willebrand factor, all the above changes correlated significantly with the change in maximum walking time (P=0.02-0.001) in the group treated with ramipril. Ramipril is associated with an increase in the biomarkers of angiogenesis/arteriogenesis and reduction in the markers of thrombosis, inflammation, and

  1. A synthetic small molecule that can walk down a track

    NASA Astrophysics Data System (ADS)

    von Delius, Max; Geertsema, Edzard M.; Leigh, David A.

    2010-02-01

    Although chemists have made small-molecule rotary motors, to date there have been no reports of small-molecule linear motors. Here we describe the synthesis and operation of a 21-atom two-legged molecular unit that is able to walk up and down a four-foothold molecular track. High processivity is conferred by designing the track-binding interactions of the two feet to be labile under different sets of conditions such that each foot can act as a temporarily fixed pivot for the other. The walker randomly and processively takes zero or one step along the track using a `passing-leg' gait each time the environment is switched between acid and base. Replacing the basic step with a redox-mediated, disulfide-exchange reaction directionally transports the bipedal molecules away from the minimum-energy distribution by a Brownian ratchet mechanism. The ultimate goal of such studies is to produce artificial, linear molecular motors that move directionally along polymeric tracks to transport cargoes and perform tasks in a manner reminiscent of biological motor proteins.

  2. Application of random walk concept to the cyclic diffusion mechanisms for self-diffusion in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Tiwari, G. P.; Mehrotra, R. S.; Iijima, Y.

    2014-02-01

    Huntington-Elcock-McCombie (HEM) mechanism involving six consecutive and correlated jumps, a triple-defect mechanism (TDM) involving three correlated jumps and an anti-structure bridge (ASB) mechanism invoking the migration of an anti-structure atom are the three mechanisms currently in vogue to explain the self- and solute diffusion in intermetallic compounds. Among them, HEM and TDM are cyclic in nature. The HEM and TDM constitute the theme of the present article. The concept of random walk is applied to them and appropriate expressions for the diffusion coefficient are derived. These equations are then employed to estimate activation energies for self-diffusion via HEM and TDM processes and compared with the available experimental data on activation energy for self-diffusion in intermetallic compounds. The resulting activation energies do not favour HEM and TDM for the self-diffusion in intermetallic compounds. A comparison of the sum of experimentally determined activation energies for vacancy formation and migration with the activation energies for self-diffusion determined from radioactive tracer method favours the conventional monovacancy-mediated process for self-diffusion in intermetallic compounds.

  3. Electrical noise to a knee joint stabilizes quiet bipedal stance.

    PubMed

    Kimura, Tetsuya; Kouzaki, Motoki

    2013-04-01

    Studies have shown that a minute, noise-like electrical stimulation (ES) of a lower limb joint stabilizes one-legged standing (OS), possibly due to the noise-enhanced joint proprioception. To demonstrate the practical utility of this finding, we assessed whether the bipedal stance (BS), relatively stable and generally employed in daily activities, is also stabilized by the same ES method. Twelve volunteers maintained quiet BS with or without an unperceivable, noise-like ES of a knee joint. The results showed that the average amplitude, peak-to-peak amplitude, and standard deviation of the foot center of pressure in the anteroposterior direction were significantly attenuated by the ES (P<0.05). These results indicate that the BS also can be stabilized by an unperceivable, noise-like ES of a knee joint.

  4. Anticipating bipedalism: trabecular organization in the newborn ilium

    PubMed Central

    Cunningham, Craig A; Black, Sue M

    2009-01-01

    Trabecular bone structural organization is considered to be predominantly influenced by localized temporal forces which act to maintain and remodel the trabecular architecture into a biomechanically optimal configuration. In the adult pelvis, the most significant remodelling forces are believed to be those generated during bipedal locomotion. However, during the fetal and neonatal period the pelvic complex is non-weight bearing and, as such, structural organization of iliac trabecular bone cannot reflect direct stance-related forces. In this study, micro-computed tomography scans from 28 neonatal ilia were analysed, using a whole bone approach, to investigate the trabecular characteristics present within specific volumes of interest relevant to density gradients highlighted in a previous radiographic study. Analysis of the structural indices bone volume fraction, trabecular thickness, trabecular spacing and trabecular number was carried out to quantitatively investigate structural composition. Quantification of the neonatal trabecular structure reinforced radiographic observations by highlighting regions of significant architectural form which grossly parallel architectural differences in the adult pattern but which have previously been attributed to stance-related forces. It is suggested that the seemingly organized rudimentary scaffold observed in the neonatal ilium may be attributable to other non-weight bearing anatomical interactions or even to a predetermined genetic blueprint. It must also be postulated that whilst the observed patterning may be indicative of a predetermined inherent template, early non-weight bearing and late stance-related locomotive influences may subsequently be superimposed upon this scaffolding and perhaps reinforced and likely remodelled at a later age. Ultimately, the analysis of this fundamental primary pattern has core implications for understanding the earliest changes in pelvic trabecular architecture and provides a baseline

  5. Development and Feasibility Assessment of a Rotational Orthosis for Walking with Arm Swing

    PubMed Central

    Fang, Juan; Xie, Qing; Yang, Guo-Yuan; Xie, Le

    2017-01-01

    Interlimb neural coupling might underlie human bipedal locomotion, which is reflected in the fact that people swing their arms synchronously with leg movement in normal gait. Therefore, arm swing should be included in gait training to provide coordinated interlimb performance. The present study aimed to develop a Rotational Orthosis for Walking with Arm Swing (ROWAS), and evaluate its feasibility from the perspectives of implementation, acceptability and responsiveness. We developed the mechanical structures of the ROWAS system in SolidWorks, and implemented the concept in a prototype. Normal gait data were used as the reference performance of the shoulder, hip, knee and ankle joints of the prototype. The ROWAS prototype was tested for function assessment and further evaluated using five able-bodied subjects for user feedback. The ROWAS prototype produced coordinated performance in the upper and lower limbs, with joint profiles similar to those occurring in normal gait. The subjects reported a stronger feeling of walking with arm swing than without. The ROWAS system was deemed feasible according to the formal assessment criteria. PMID:28203142

  6. Development and Feasibility Assessment of a Rotational Orthosis for Walking with Arm Swing.

    PubMed

    Fang, Juan; Xie, Qing; Yang, Guo-Yuan; Xie, Le

    2017-01-01

    Interlimb neural coupling might underlie human bipedal locomotion, which is reflected in the fact that people swing their arms synchronously with leg movement in normal gait. Therefore, arm swing should be included in gait training to provide coordinated interlimb performance. The present study aimed to develop a Rotational Orthosis for Walking with Arm Swing (ROWAS), and evaluate its feasibility from the perspectives of implementation, acceptability and responsiveness. We developed the mechanical structures of the ROWAS system in SolidWorks, and implemented the concept in a prototype. Normal gait data were used as the reference performance of the shoulder, hip, knee and ankle joints of the prototype. The ROWAS prototype was tested for function assessment and further evaluated using five able-bodied subjects for user feedback. The ROWAS prototype produced coordinated performance in the upper and lower limbs, with joint profiles similar to those occurring in normal gait. The subjects reported a stronger feeling of walking with arm swing than without. The ROWAS system was deemed feasible according to the formal assessment criteria.

  7. Body fat assessment by a new bipedal bioimpedance instrument in normal weight and obese women.

    PubMed

    Hainer, V; Kunesová, M; Parízková, J; Stich, V; Horejs, J; Müller, L

    1995-01-01

    The aim of the study was to evaluate a new bioimpedance method for assessment of body fat employing bipedal electrodes instead of those attached to both upper and lower extremities. The new analyzer (TBF-105, Tanita Corp., Tokyo, Japan) enables simultaneous measurements of body weight and total body resistance in a subject standing on the stainless steel electrodes. The instrument was tested in both normal weight and obese women. Fat mass estimated by bipedal bioimpedance was highly correlated with that determined by hydrodensitometry (n = 145, r = 0.945, p < 0.001). Fat mass estimated by bipedal bioimpedance significantly correlated not only with subcutaneous fat measured as a sum of 10 skinfolds (r = 0.758, p < 0.001) but also with visceral fat determined as an area on CT scan (r = 0.780, p < 0.001). Anthropometric variables did not substantially influence the differences revealed in fat mass determined by bipedal bioimpedance and by densitometry. An overestimation of total fat mass by bipedal bioimpedance has not been revealed in severely obese individuals, even in those with higher fat accumulation in the limb region. In conclusion, our data have demonstrated that the new bioimpedance instrument employing bipedal electrodes represents a reliable tool for rapid body fat assessment in both normal weight and obese women.

  8. The Recovery of Walking in Stroke Patients: A Review

    ERIC Educational Resources Information Center

    Jang, Sung Ho

    2010-01-01

    We reviewed the literature on walking recovery of stroke patients as it relates to the following subjects: epidemiology of walking dysfunction, recovery course of walking, and recovery mechanism of walking (neural control of normal walking, the evaluation methods for leg motor function, and motor recovery mechanism of leg). The recovery of walking…

  9. The Recovery of Walking in Stroke Patients: A Review

    ERIC Educational Resources Information Center

    Jang, Sung Ho

    2010-01-01

    We reviewed the literature on walking recovery of stroke patients as it relates to the following subjects: epidemiology of walking dysfunction, recovery course of walking, and recovery mechanism of walking (neural control of normal walking, the evaluation methods for leg motor function, and motor recovery mechanism of leg). The recovery of walking…

  10. Walking with insects: molecular mechanisms behind parasitic manipulation of host behaviour.

    PubMed

    van Houte, Stineke; Ros, Vera I D; van Oers, Monique M

    2013-07-01

    Parasitic infections are often followed by changes in host behaviour. Numerous and exquisite examples of such behavioural alterations are known, covering a broad spectrum of parasites and hosts. Most descriptions of such parasite-induced changes in host behaviour are observational reports, while experimentally confirmed examples of parasite genes inducing these changes are limited. In this study, we review changes in invertebrate host behaviour observed upon infection by parasites and discuss such changes in an evolutionary context. We then explore possible mechanisms involved in parasite-induced changes in host behaviour. Genes and pathways known to play a role in invertebrate behaviour are reviewed, and we hypothesize how parasites (may) affect these pathways. This review provides the state of the art in this exciting, interdisciplinary field by exploring possible pathways triggered in hosts, suggesting methodologies to unravel the molecular mechanisms that lead to changes in host behaviour. © 2013 John Wiley & Sons Ltd.

  11. The Human Shoulder Suspension Apparatus: A Causal Explanation for Bilateral Asymmetry and a Fresh Look at the Evolution of Human Bipedality.

    PubMed

    Osborn, Michelle L; Homberger, Dominique G

    2015-09-01

    The combination of large mastoid processes and clavicles is unique to humans, but the biomechanical and evolutionary significance of their special configuration is poorly understood. As part of the newly conceptualized shoulder suspension apparatus, the mastoid processes and clavicles are shaped by forces exerted by the musculo-fascial components of the cleidomastoid and clavotrapezius muscles as they suspend the shoulders from the head. Because both skeletal elements develop during infancy in tandem with the attainment of an upright posture, increased manual dexterity, and the capacity for walking, we hypothesized that the same forces would have shaped them as the shoulder suspension apparatus evolved in ancestral humans in tandem with an upright posture, increased manual dexterity, and bipedality with swinging arms. Because the shoulder suspension apparatus is subjected to asymmetrical forces from handedness, we predicted that its skeletal features would grow asymmetrically. We used this prediction to test our hypothesis in a natural experiment to correlate the size of the skeletal features with the forces exerted on them. We (1) measured biomechanically relevant bony features within the shoulder suspension apparatus in 101 male human specimens (62 of known handedness); and (2) modeled and analyzed the forces within the shoulder suspension apparatus from X-ray CT data. We identified eight right-handed characters and demonstrated the causal relationship between these right-handed characters and the magnitude and direction of forces acting on them. Our data suggest that the presence of the shoulder suspension apparatus in humans was a necessary precondition for human bipedality.

  12. Mechanical energy oscillations of two brachiation gaits: measurement and simulation.

    PubMed

    Bertram, J E; Chang, Y H

    2001-08-01

    How do arm-swinging apes locomote effectively over a variety of speeds? One way to reduce the metabolic energy cost of locomotion is to transfer energy between reversible mechanical modes. In terrestrial animals, at least two transfer mechanisms have been identified: 1) a pendulum-like mechanism for walking, with exchange between gravitational potential energy and translational kinetic energy, and 2) a spring-like mechanism for running, where the elastic strain energy of stretched muscle and tendon is largely returned to reaccelerate the animal. At slower speeds, a brachiator will always have at least one limb in contact with the support, similar to the overlap of foot contact in bipedal walking. At faster speeds, brachiators exhibit an aerial phase, similar to that seen in bipedal running. Are there two distinct brachiation gaits even though the animal appears to simply swing beneath its overhead support? If so, are different exchange mechanisms employed? Our kinetic analysis of brachiation in a white-handed gibbon (Hylobates lar) indicates that brachiation is indeed comprised of two mechanically distinct gaits. At slower speeds in "continuous contact" brachiation, the gibbon utilizes a simple pendulum-like transfer of mechanical energy within each stride. At faster speeds in "ricochetal" brachiation, translational and rotational kinetic energy are exchanged in a novel "whip-like" transfer. We propose that brachiators utilize the transfer between translational and rotational kinetic energy to control the dynamics of their swing. This maneuver may allow muscle action at the shoulder to control the transfer and adjust the ballistic portion of the step to meet the requirements for the next hand contact. Copyright 2001 Wiley-Liss, Inc.

  13. Towards bipedal behavior on a quadrupedal platform using optimal control

    NASA Astrophysics Data System (ADS)

    Topping, T. Turner; Vasilopoulos, Vasileios; De, Avik; Koditschek, Daniel E.

    2016-05-01

    This paper explores the applicability of a Linear Quadratic Regulator (LQR) controller design to the problem of bipedal stance on the Minitaur [1] quadrupedal robot. Restricted to the sagittal plane, this behavior exposes a three degree of freedom (DOF) double inverted pendulum with extensible length that can be projected onto the familiar underactuated revolute-revolute "Acrobot" model by assuming a locked prismatic DOF, and a pinned toe. While previous work has documented the successful use of local LQR control to stabilize a physical Acrobot, simulations reveal that a design very similar to those discussed in the past literature cannot achieve an empirically viable controller for our physical plant. Experiments with a series of increasingly close physical facsimiles leading to the actual Minitaur platform itself corroborate and underscore the physical Minitaur platform corroborate and underscore the implications of the simulation study. We conclude that local LQR-based linearized controller designs are too fragile to stabilize the physical Minitaur platform around its vertically erect equilibrium and end with a brief assessment of a variety of more sophisticated nonlinear control approaches whose pursuit is now in progress.

  14. Enforced bipedal downhill running induces Achilles tendinosis in rats.

    PubMed

    Ng, Gabriel Yin-Fat; Chung, Polly Yee-Man; Wang, Jenny Shijie; Cheung, Roy Tsz-Hei

    2011-01-01

    Enforced downhill running has been reported to induce tendinosis in the rat supraspinatus tendon but similar exercise failed to induce Achilles tendinosis in this animal. Due to the presence of acromial arch in the shoulder, accessing the supraspinatus tendon with physical modalities is difficult; thus this model may not be suitable for studying the treatment for tendinosis. To develop a rat model for Achilles tendinosis, we tested 14 mature Sprague-Dawley rats by dividing them into 2 groups of 7 each. The experimental group was subjected to a daily enforced downhill bipedal running program by suspending their upper bodies so that they ran with their hind limbs on a treadmill for 1 hr/day for 8 weeks. The downward inclination was 20 degrees and the speed was 17 m/min. The animals in the control group did not undergo any exercise. After 8 weeks, the Achilles tendons were harvested and subjected to histological and biomechanical analysis. Histological examination revealed tenocyte proliferation, change in tenocytes appearance, and collagen bundle disintegration in the running group. The biomechanical testing revealed significant decrease in stiffness (p = 0.002) and ultimate tensile strength (p = 0.016) in the running group than in the control group. Both the histological and biomechanical findings are suggestive of changes in the tendon of the running group that resembled the pathological changes of tendinosis in human. This new model of Achilles tendinosis in rat will be useful for studying the etiology and subsequent management strategies of this condition.

  15. A three-dimensional human walking model

    NASA Astrophysics Data System (ADS)

    Yang, Q. S.; Qin, J. W.; Law, S. S.

    2015-11-01

    A three-dimensional human bipedal walking model with compliant legs is presented in this paper. The legs are modeled with time-variant dampers, and the model is able to characterize the gait pattern of an individual using a minimal set of parameters. Feedback control, for both the forward and lateral movements, is implemented to regulate the walking performance of the pedestrian. The model provides an improvement over classic invert pendulum models. Numerical studies were undertaken to investigate the effects of leg stiffness and attack angle. Simulation results show that when walking at a given speed, increasing the leg stiffness with a constant attack angle results in a longer step length, a higher step frequency, a faster walking speed and an increase in both the peak vertical and lateral ground reaction forces. Increasing the attack angle with a constant leg stiffness results in a higher step frequency, a decrease in the step length, an increase in the total energy of the system and a decrease in both the peak vertical and lateral ground reaction forces.

  16. Modified walking shoes for knee osteoarthritis: Mechanisms for reductions in the knee adduction moment.

    PubMed

    Kean, Crystal O; Bennell, Kim L; Wrigley, Tim V; Hinman, Rana S

    2013-08-09

    The objective of this study was to examine mechanisms underpinning the reduction in knee adduction moment (KAM) and changes in frontal plane knee-ground reaction force (GRF) lever arm with a modified shoe that incorporates both a variable-stiffness sole and lateral wedging. Thirty individuals with symptomatic knee osteoarthritis (OA) and 30 overweight asymptomatic individuals underwent gait analyses wearing modified and standard shoes. In both groups, there was a decrease in the lever arm (p<0.001), and a lateral shift in the center of pressure (COP) offset (p ≤ 0.001). There was no change in frontal plane or medial-lateral GRF magnitudes, lateral trunk lean or stance duration in either group. There was no significant change in the frontal plane hip-knee-ankle angle in the OA group but a significant decrease in the overweight group (p=0.003). In both groups, changes in lever arm and frontal plane GRF magnitude predicted change in peak KAM (p<0.01), but only change in lever arm predicted change in KAM impulse (p<0.001). In the OA group, changes in COP offset and medial-lateral GRF magnitude predicted change in lever arm (p<0.05), whereas changes in trunk lean and hip-knee-ankle angle predicted change in lever arm in the overweight group (p=0.01). In conclusion, the change in lever arm contributed the most to explaining change in KAM parameters with modified shoes. The change in the lever arm was driven by changes evident at the foot in the OA participants (COP and medial-lateral GRF), and by more proximal changes (hip-knee-ankle angle and trunk lean) in the overweight group.

  17. Reflex Control of Robotic Gait Using Human Walking Data

    PubMed Central

    Macleod, Catherine A.; Meng, Lin; Conway, Bernard A.; Porr, Bernd

    2014-01-01

    Control of human walking is not thoroughly understood, which has implications in developing suitable strategies for the retraining of a functional gait following neurological injuries such as spinal cord injury (SCI). Bipedal robots allow us to investigate simple elements of the complex nervous system to quantify their contribution to motor control. RunBot is a bipedal robot which operates through reflexes without using central pattern generators or trajectory planning algorithms. Ground contact information from the feet is used to activate motors in the legs, generating a gait cycle visually similar to that of humans. Rather than developing a more complicated biologically realistic neural system to control the robot's stepping, we have instead further simplified our model by measuring the correlation between heel contact and leg muscle activity (EMG) in human subjects during walking and from this data created filter functions transferring the sensory data into motor actions. Adaptive filtering was used to identify the unknown transfer functions which translate the contact information into muscle activation signals. Our results show a causal relationship between ground contact information from the heel and EMG, which allows us to create a minimal, linear, analogue control system for controlling walking. The derived transfer functions were applied to RunBot II as a proof of concept. The gait cycle produced was stable and controlled, which is a positive indication that the transfer functions have potential for use in the control of assistive devices for the retraining of an efficient and effective gait with potential applications in SCI rehabilitation. PMID:25347544

  18. Walking Problems

    MedlinePlus

    ... Parkinson's disease Diseases such as arthritis or multiple sclerosis Vision or balance problems Treatment of walking problems depends on the cause. Physical therapy, surgery, or mobility aids may help.

  19. Foot trajectory approximation using the pendulum model of walking.

    PubMed

    Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A; Hunt, Kenneth J

    2014-01-01

    Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.

  20. Joint loads in marsupial ankles reflect habitual bipedalism versus quadrupedalism.

    PubMed

    Carlson, Kristian J; Jashashvili, Tea; Houghton, Kimberley; Westaway, Michael C; Patel, Biren A

    2013-01-01

    Joint surfaces of limb bones are loaded in compression by reaction forces generated from body weight and musculotendon complexes bridging them. In general, joints of eutherian mammals have regions of high radiodensity subchondral bone that are better at resisting compressive forces than low radiodensity subchondral bone. Identifying similar form-function relationships between subchondral radiodensity distribution and joint load distribution within the marsupial postcranium, in addition to providing a richer understanding of marsupial functional morphology, can serve as a phylogenetic control in evaluating analogous relationships within eutherian mammals. Where commonalities are established across phylogenetic borders, unifying principles in mammalian physiology, morphology, and behavior can be identified. Here, we assess subchondral radiodensity patterns in distal tibiae of several marsupial taxa characterized by different habitual activities (e.g., locomotion). Computed tomography scanning, maximum intensity projection maps, and pixel counting were used to quantify radiodensity in 41 distal tibiae of bipedal (5 species), arboreal quadrupedal (4 species), and terrestrial quadrupedal (5 species) marsupials. Bipeds (Macropus and Wallabia) exhibit more expansive areas of high radiodensity in the distal tibia than arboreal (Dendrolagus, Phascolarctos, and Trichosurus) or terrestrial quadrupeds (Sarcophilus, Thylacinus, Lasiorhinus, and Vombatus), which may reflect the former carrying body weight only through the hind limbs. Arboreal quadrupeds exhibit smallest areas of high radiodensity, though they differ non-significantly from terrestrial quadrupeds. This could indicate slightly more compliant gaits by arboreal quadrupeds compared to terrestrial quadrupeds. The observed radiodensity patterns in marsupial tibiae, though their statistical differences disappear when controlling for phylogeny, corroborate previously documented patterns in primates and xenarthrans

  1. Joint Loads in Marsupial Ankles Reflect Habitual Bipedalism versus Quadrupedalism

    PubMed Central

    Carlson, Kristian J.; Jashashvili, Tea; Houghton, Kimberley; Westaway, Michael C.; Patel, Biren A.

    2013-01-01

    Joint surfaces of limb bones are loaded in compression by reaction forces generated from body weight and musculotendon complexes bridging them. In general, joints of eutherian mammals have regions of high radiodensity subchondral bone that are better at resisting compressive forces than low radiodensity subchondral bone. Identifying similar form-function relationships between subchondral radiodensity distribution and joint load distribution within the marsupial postcranium, in addition to providing a richer understanding of marsupial functional morphology, can serve as a phylogenetic control in evaluating analogous relationships within eutherian mammals. Where commonalities are established across phylogenetic borders, unifying principles in mammalian physiology, morphology, and behavior can be identified. Here, we assess subchondral radiodensity patterns in distal tibiae of several marsupial taxa characterized by different habitual activities (e.g., locomotion). Computed tomography scanning, maximum intensity projection maps, and pixel counting were used to quantify radiodensity in 41 distal tibiae of bipedal (5 species), arboreal quadrupedal (4 species), and terrestrial quadrupedal (5 species) marsupials. Bipeds (Macropus and Wallabia) exhibit more expansive areas of high radiodensity in the distal tibia than arboreal (Dendrolagus, Phascolarctos, and Trichosurus) or terrestrial quadrupeds (Sarcophilus, Thylacinus, Lasiorhinus, and Vombatus), which may reflect the former carrying body weight only through the hind limbs. Arboreal quadrupeds exhibit smallest areas of high radiodensity, though they differ non-significantly from terrestrial quadrupeds. This could indicate slightly more compliant gaits by arboreal quadrupeds compared to terrestrial quadrupeds. The observed radiodensity patterns in marsupial tibiae, though their statistical differences disappear when controlling for phylogeny, corroborate previously documented patterns in primates and xenarthrans

  2. Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor.

    PubMed

    Kivell, Tracy L; Schmitt, Daniel

    2009-08-25

    Despite decades of debate, it remains unclear whether human bipedalism evolved from a terrestrial knuckle-walking ancestor or from a more generalized, arboreal ape ancestor. Proponents of the knuckle-walking hypothesis focused on the wrist and hand to find morphological evidence of this behavior in the human fossil record. These studies, however, have not examined variation or development of purported knuckle-walking features in apes or other primates, data that are critical to resolution of this long-standing debate. Here we present novel data on the frequency and development of putative knuckle-walking features of the wrist in apes and monkeys. We use these data to test the hypothesis that all knuckle-walking apes share similar anatomical features and that these features can be used to reliably infer locomotor behavior in our extinct ancestors. Contrary to previous expectations, features long-assumed to indicate knuckle-walking behavior are not found in all African apes, show different developmental patterns across species, and are found in nonknuckle-walking primates as well. However, variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla). The presence of purported knuckle-walking features in the hominin wrist can thus be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor occupying the ecological niche common to all living apes.

  3. Analysis on the Load Carrying Mechanism Integrated as Heterogeneous Co-operative Manipulator in a Walking Wheelchair

    NASA Astrophysics Data System (ADS)

    Rajay Vedaraj, I. S.; Jain, Ritika; Rao, B. V. A.

    2014-07-01

    used for climbing stairs with three leg design and anlaysis were also done on the mechanism integrated to the system. Kinematics of the legs are analysed separately and the legs are designed to carry a maximum of 175kgs, which is sustained by the center leg and shared by the dual wing legs equally during the walking phase. In the proposed design, screwjack mechanism is used as the central leg to share the load and thus the analysis on the load sharing capability of the whole system is analysed and concluded in terms of failure modes.

  4. 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

  5. Energy efficient walking with central pattern generators: from passive dynamic walking to biologically inspired control.

    PubMed

    Verdaasdonk, B W; Koopman, H F J M; van der Helm, F C T

    2009-07-01

    Like human walking, passive dynamic walking-i.e. walking down a slope with no actuation except gravity-is energy efficient by exploiting the natural dynamics. In the animal world, neural oscillators termed central pattern generators (CPGs) provide the basic rhythm for muscular activity in locomotion. We present a CPG model, which automatically tunes into the resonance frequency of the passive dynamics of a bipedal walker, i.e. the CPG model exhibits resonance tuning behavior. Each leg is coupled to its own CPG, controlling the hip moment of force. Resonance tuning above the endogenous frequency of the CPG-i.e. the CPG's eigenfrequency-is achieved by feedback of both limb angles to their corresponding CPG, while integration of the limb angles provides resonance tuning at and below the endogenous frequency of the CPG. Feedback of the angular velocity of both limbs to their corresponding CPG compensates for the time delay in the loop coupling each limb to its CPG. The resonance tuning behavior of the CPG model allows the gait velocity to be controlled by a single parameter, while retaining the energy efficiency of passive dynamic walking.

  6. Dual processing of visual rotation for bipedal stance control.

    PubMed

    Day, Brian L; Muller, Timothy; Offord, Joanna; Di Giulio, Irene

    2016-10-01

    component decreased with faster visual rotation, while the later component increased. Furthermore, the decrease in size of the early component was not achieved by a simple attenuation of gain, but by a change in its temporal structure. We conclude that the two components represent expressions of different motor functions, both pertinent to the control of bipedal stance. We propose that the early response stems from the balance control system attempting to minimise unintended body motion, while the later response arises from the postural control system attempting to align the body with gravity. © 2016 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

  7. Experimental verification of a computational technique for determining ground reactions in human bipedal stance.

    PubMed

    Audu, Musa L; Kirsch, Robert F; Triolo, Ronald J

    2007-01-01

    We have developed a three-dimensional (3D) biomechanical model of human standing that enables us to study the mechanisms of posture and balance simultaneously in various directions in space. Since the two feet are on the ground, the system defines a kinematically closed-chain which has redundancy problems that cannot be resolved using the laws of mechanics alone. We have developed a computational (optimization) technique that avoids the problems with the closed-chain formulation thus giving users of such models the ability to make predictions of joint moments, and potentially, muscle activations using more sophisticated musculoskeletal models. This paper describes the experimental verification of the computational technique that is used to estimate the ground reaction vector acting on an unconstrained foot while the other foot is attached to the ground, thus allowing human bipedal standing to be analyzed as an open-chain system. The computational approach was verified in terms of its ability to predict lower extremity joint moments derived from inverse dynamic simulations performed on data acquired from four able-bodied volunteers standing in various postures on force platforms. Sensitivity analyses performed with model simulations indicated which ground reaction force (GRF) and center of pressure (COP) components were most critical for providing better estimates of the joint moments. Overall, the joint moments predicted by the optimization approach are strongly correlated with the joint moments computed using the experimentally measured GRF and COP (0.78 < or = r(2) < or = 0.99,median,0.96) with a best-fit that was not statistically different from a straight line with unity slope (experimental=computational results) for postures of the four subjects examined. These results indicate that this model-based technique can be relied upon to predict reasonable and consistent estimates of the joint moments using the predicted GRF and COP for most standing postures.

  8. The relationship between speed, contact time and peak plantar pressure in terrestrial walking of bonobos.

    PubMed

    Vereecke, Evie; D'Août, Kristiaan; De Clercq, Dirk; Van Elsacker, Linda; Aerts, Peter

    2004-01-01

    The aim of this paper is twofold. Firstly, we investigate whether contact times, as recorded by pedobarographic systems during quadrupedal and bipedal walking of bonobos, can be used to reliably calculate actual velocities, by applying formulae based on lateral-view video recordings. Secondly, we investigate the effect of speed on peak plantar pressures during bipedal and quadrupedal walking of the bonobo. Data were obtained from 4 individuals from a group of bonobos at the Animal Park Planckendael. From our study, we can conclude that both walking speeds calculated from contact times and lower leg length or simply from recorded contact times are good estimators for walking speed, when direct observation of the latter is impossible. Further, it was found that effects of speed on peak plantar pressures and vertical forces are absent or at least subtle in comparison to a large variation in pressure patterns. In bonobos, the same pressure patterns are used at all walking speeds, and, in consequence, we do not expect major changes in foot function.

  9. How is sagittal balance acquired during bipedal gait acquisition? Comparison of neonatal and adult pelves in three dimensions. Evolutionary implications.

    PubMed

    Tardieu, Christine; Bonneau, Noémie; Hecquet, Jérôme; Boulay, Christophe; Marty, Catherine; Legaye, Jean; Duval-Beaupère, Geneviève

    2013-08-01

    We compare adult and intact neonatal pelves, using a pelvic sagittal variable, the angle of sacral incidence, which presents significant correlations with vertebral curvature in adults and plays an important role in sagittal balance of the trunk on the lower limbs. Since the lumbar curvature develops in the child in association with gait acquisition, we expect a change in this angle during growth which could contribute to the acquisition of sagittal balance. To understand the mechanisms underlying the sagittal balance in the evolution of human bipedalism, we also measure the angle of incidence of hominid fossils. Fourty-seven landmarks were digitized on 50 adult and 19 intact neonatal pelves. We used a three-dimensional model of the pelvis (DE-VISU program) which calculates the angle of sacral incidence and related functional variables. Cross-sectional data from newborns and adults show that the angle of sacral incidence increases and becomes negatively correlated with the sacro-acetabular distance. During ontogeny the sacrum becomes curved, tends to sink down between the iliac blades as a wedge and moves backward in the sagittal plane relative to the acetabula, thus contributing to the backwards displacement of the center of gravity of the trunk. A chain of correlations links the degree of the sacral slope and of the angle of incidence, which is tightly linked with the lumbar lordosis. We sketch a model showing the coordinated changes occurring in the pelvis and vertebral column during the acquisition of bipedalism in infancy. In the australopithecine pelves, Sts 14 and AL 288-1, and in the Homo erectus Gona pelvis the angle of sacral incidence reaches the mean values of humans. Discussing the incomplete pelves of Ardipithecus ramidus, Australopithecus sediba and the Nariokotome Boy, we suggest how the functional linkage between pelvis and spine, observed in humans, could have emerged during hominid evolution.

  10. Neural decoding of treadmill walking from noninvasive electroencephalographic signals

    PubMed Central

    Presacco, Alessandro; Goodman, Ronald; Forrester, Larry

    2011-01-01

    Chronic recordings from ensembles of cortical neurons in primary motor and somatosensory areas in rhesus macaques provide accurate information about bipedal locomotion (Fitzsimmons NA, Lebedev MA, Peikon ID, Nicolelis MA. Front Integr Neurosci 3: 3, 2009). Here we show that the linear and angular kinematics of the ankle, knee, and hip joints during both normal and precision (attentive) human treadmill walking can be inferred from noninvasive scalp electroencephalography (EEG) with decoding accuracies comparable to those from neural decoders based on multiple single-unit activities (SUAs) recorded in nonhuman primates. Six healthy adults were recorded. Participants were asked to walk on a treadmill at their self-selected comfortable speed while receiving visual feedback of their lower limbs (i.e., precision walking), to repeatedly avoid stepping on a strip drawn on the treadmill belt. Angular and linear kinematics of the left and right hip, knee, and ankle joints and EEG were recorded, and neural decoders were designed and optimized with cross-validation procedures. Of note, the optimal set of electrodes of these decoders were also used to accurately infer gait trajectories in a normal walking task that did not require subjects to control and monitor their foot placement. Our results indicate a high involvement of a fronto-posterior cortical network in the control of both precision and normal walking and suggest that EEG signals can be used to study in real time the cortical dynamics of walking and to develop brain-machine interfaces aimed at restoring human gait function. PMID:21768121

  11. Neural decoding of treadmill walking from noninvasive electroencephalographic signals.

    PubMed

    Presacco, Alessandro; Goodman, Ronald; Forrester, Larry; Contreras-Vidal, Jose Luis

    2011-10-01

    Chronic recordings from ensembles of cortical neurons in primary motor and somatosensory areas in rhesus macaques provide accurate information about bipedal locomotion (Fitzsimmons NA, Lebedev MA, Peikon ID, Nicolelis MA. Front Integr Neurosci 3: 3, 2009). Here we show that the linear and angular kinematics of the ankle, knee, and hip joints during both normal and precision (attentive) human treadmill walking can be inferred from noninvasive scalp electroencephalography (EEG) with decoding accuracies comparable to those from neural decoders based on multiple single-unit activities (SUAs) recorded in nonhuman primates. Six healthy adults were recorded. Participants were asked to walk on a treadmill at their self-selected comfortable speed while receiving visual feedback of their lower limbs (i.e., precision walking), to repeatedly avoid stepping on a strip drawn on the treadmill belt. Angular and linear kinematics of the left and right hip, knee, and ankle joints and EEG were recorded, and neural decoders were designed and optimized with cross-validation procedures. Of note, the optimal set of electrodes of these decoders were also used to accurately infer gait trajectories in a normal walking task that did not require subjects to control and monitor their foot placement. Our results indicate a high involvement of a fronto-posterior cortical network in the control of both precision and normal walking and suggest that EEG signals can be used to study in real time the cortical dynamics of walking and to develop brain-machine interfaces aimed at restoring human gait function.

  12. Tail autotomy affects bipedalism but not sprint performance in a cursorial Mediterranean lizard.

    PubMed

    Savvides, Pantelis; Stavrou, Maria; Pafilis, Panayiotis; Sfenthourakis, Spyros

    2017-02-01

    Running is essential in all terrestrial animals mainly for finding food and mates and escaping from predators. Lizards employ running in all their everyday functions, among which defense stands out. Besides flight, tail autotomy is another very common antipredatory strategy within most lizard families. The impact of tail loss to sprint performance seems to be species dependent. In some lizard species, tail shedding reduces sprint speed, in other species, increases it, and, in a few species, speed is not affected at all. Here, we aimed to clarify the effect of tail autotomy on the sprint performance of a cursorial lizard with particular adaptations for running, such as bipedalism and spike-like protruding scales (fringes) on the toepads that allow high speed on sandy substrates. We hypothesized that individuals that performed bipedalism, and have more and larger fringes, would achieve higher sprint performance. We also anticipated that tail shedding would affect sprint speed (though we were not able to define in what way because of the unpredictable effects that tail loss has on different species). According to our results, individuals that ran bipedally were faster; limb length and fringe size had limited effects on sprint performance whereas tail autotomy affected quadrupedal running only in females. Nonetheless, tail loss significantly affected bipedalism: the ability for running on hindlimbs was completely lost in all adult individuals and in 72.3% of juveniles.

  13. Tail autotomy affects bipedalism but not sprint performance in a cursorial Mediterranean lizard

    NASA Astrophysics Data System (ADS)

    Savvides, Pantelis; Stavrou, Maria; Pafilis, Panayiotis; Sfenthourakis, Spyros

    2017-02-01

    Running is essential in all terrestrial animals mainly for finding food and mates and escaping from predators. Lizards employ running in all their everyday functions, among which defense stands out. Besides flight, tail autotomy is another very common antipredatory strategy within most lizard families. The impact of tail loss to sprint performance seems to be species dependent. In some lizard species, tail shedding reduces sprint speed, in other species, increases it, and, in a few species, speed is not affected at all. Here, we aimed to clarify the effect of tail autotomy on the sprint performance of a cursorial lizard with particular adaptations for running, such as bipedalism and spike-like protruding scales (fringes) on the toepads that allow high speed on sandy substrates. We hypothesized that individuals that performed bipedalism, and have more and larger fringes, would achieve higher sprint performance. We also anticipated that tail shedding would affect sprint speed (though we were not able to define in what way because of the unpredictable effects that tail loss has on different species). According to our results, individuals that ran bipedally were faster; limb length and fringe size had limited effects on sprint performance whereas tail autotomy affected quadrupedal running only in females. Nonetheless, tail loss significantly affected bipedalism: the ability for running on hindlimbs was completely lost in all adult individuals and in 72.3% of juveniles.

  14. The influence of wind resistance in running and walking and the mechanical efficiency of work against horizontal or vertical forces

    PubMed Central

    Pugh, L. G. C. E.

    1971-01-01

    1. O2 intakes were determined on subjects running and walking at various constant speeds, (a) against wind of up to 18·5 m/sec (37 knots) in velocity, and (b) on gradients ranging from 2 to 8%. 2. In running and walking against wind, O2 intakes increased as the square of wind velocity. 3. In running on gradients the relation of O2 intake and lifting work was linear and independent of speed. In walking on gradients the relation was linear at work rates above 300 kg m/min, but curvilinear at lower work rates. 4. In a 65 kg athlete running at 4·45 m/sec (marathon speed) V̇O2 increased from 3·0 l./min with minimal wind to 5·0 l./min at a wind velocity of 18·5 m/sec. The corresponding values for a 75 kg subject walking at 1·25 m/sec were 0·8 l./min with minimal wind and 3·1 l./min at a wind velocity of 18·5 m/sec. 5. Direct measurements of wind pressure on shapes of similar area to one of the subjects yielded higher values than those predicted from the relation of wind velocity and lifting work at equal O2 intakes. Horizontal work against wind was more efficient than vertical work against gravity. 6. The energy cost of overcoming air resistance in track running may be 7·5% of the total energy cost at middle distance speed and 13% at sprint speed. Running 1 m behind another runner virtually eliminated air resistance and reduced V̇O2 by 6·5% at middle distance speed. PMID:5574828

  15. When Human Walking is a Random Walk

    NASA Astrophysics Data System (ADS)

    Hausdorff, J. M.

    1998-03-01

    The complex, hierarchical locomotor system normally does a remarkable job of controlling an inherently unstable, multi-joint system. Nevertheless, the stride interval --- the duration of a gait cycle --- fluctuates from one stride to the next, even under stationary conditions. We used random walk analysis to study the dynamical properties of these fluctuations under normal conditions and how they change with disease and aging. Random walk analysis of the stride-to-stride fluctuations of healthy, young adult men surprisingly reveals a self-similar pattern: fluctuations at one time scale are statistically similar to those at multiple other time scales (Hausdorff et al, J Appl Phsyiol, 1995). To study the stability of this fractal property, we analyzed data obtained from healthy subjects who walked for 1 hour at their usual pace, as well as at slower and faster speeds. The stride interval fluctuations exhibited long-range correlations with power-law decay for up to a thousand strides at all three walking rates. In contrast, during metronomically-paced walking, these long-range correlations disappeared; variations in the stride interval were uncorrelated and non-fractal (Hausdorff et al, J Appl Phsyiol, 1996). To gain insight into the mechanism(s) responsible for this fractal property, we examined the effects of aging and neurological impairment. Using detrended fluctuation analysis (DFA), we computed α, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. α was significantly lower in healthy elderly subjects compared to young adults (p < .003) and in subjects with Huntington's disease, a neuro-degenerative disorder of the central nervous system, compared to disease-free controls (p < 0.005) (Hausdorff et al, J Appl Phsyiol, 1997). α was also significantly related to degree of functional impairment in subjects with Huntington's disease (r=0.78). Recently, we have observed that just as

  16. Quantum random walks without walking

    SciTech Connect

    Manouchehri, K.; Wang, J. B.

    2009-12-15

    Quantum random walks have received much interest due to their nonintuitive dynamics, which may hold the key to a new generation of quantum algorithms. What remains a major challenge is a physical realization that is experimentally viable and not limited to special connectivity criteria. We present a scheme for walking on arbitrarily complex graphs, which can be realized using a variety of quantum systems such as a Bose-Einstein condensate trapped inside an optical lattice. This scheme is particularly elegant since the walker is not required to physically step between the nodes; only flipping coins is sufficient.

  17. Hand before foot? Cortical somatotopy suggests manual dexterity is primitive and evolved independently of bipedalism

    PubMed Central

    Hashimoto, Teruo; Ueno, Kenichi; Ogawa, Akitoshi; Asamizuya, Takeshi; Suzuki, Chisato; Cheng, Kang; Tanaka, Michio; Taoka, Miki; Iwamura, Yoshiaki; Suwa, Gen; Iriki, Atsushi

    2013-01-01

    People have long speculated whether the evolution of bipedalism in early hominins triggered tool use (by freeing their hands) or whether the necessity of making and using tools encouraged the shift to upright gait. Either way, it is commonly thought that one led to the other. In this study, we sought to shed new light on the origins of manual dexterity and bipedalism by mapping the neural representations in the brain of the fingers and toes of living people and monkeys. Contrary to the ‘hand-in-glove’ notion outlined above, our results suggest that adaptations underlying tool use evolved independently of those required for human bipedality. In both humans and monkeys, we found that each finger was represented separately in the primary sensorimotor cortex just as they are physically separated in the hand. This reflects the ability to use each digit independently, as required for the complex manipulation involved in tool use. The neural mapping of the subjects’ toes differed, however. In the monkeys, the somatotopic representation of the toes was fused, showing that the digits function predominantly as a unit in general grasping. Humans, by contrast, had an independent neurological representation of the big toe (hallux), suggesting association with bipedal locomotion. These observations suggest that the brain circuits for the hand had advanced beyond simple grasping, whereas our primate ancestors were still general arboreal quadrupeds. This early adaptation laid the foundation for the evolution of manual dexterity, which was preserved and enhanced in hominins. In hominins, a separate adaptation, involving the neural separation of the big toe, apparently occurred with bipedality. This accords with the known fossil evidence, including the recently reported hominin fossils which have been dated to 4.4 million years ago. PMID:24101627

  18. Wading for food the driving force of the evolution of bipedalism?

    PubMed

    Kuliukas, Algis

    2002-01-01

    Evidence is accumulating that suggests that the large human brain is most likely to have evolved in littoral and estuarine habitats rich in naturally occurring essential fatty acids. This paper adds further weight to this view, suggesting that another key human trait, our bipedality might also be best explained as an adaptation to a water-side niche. Evidence is provided here that extant apes, although preferring to keep dry, go into water when driven to do so by hunger. The anecdotal evidence has suggested that they tend to do this bipedally. Here, a new empirical study of captive bonobos found them to exhibit 2% or less bipedality on the ground or in trees but over 90% when wading in water to collect food. The skeletal morphology of AL 288-1 ("Lucy") is shown to indicate a strong ability to abduct and adduct the femur. These traits, together with a remarkably platypelloid pelvis, have not yet been adequately explained by terrestrial or arboreal models for early bipedalism but are consistent with those expected in an ape that adopted a specialist side-to-side 'ice-skating' or sideways wading mode. It is argued that this explanation of A. afarensis locomotor morphology is more parsimonious than others which have plainly failed to produce a consensus. Microwear evidence of Australopithecus dentition is also presented as evidence that the drive for such a wading form of locomotion might well have been waterside foods. This model obtains further support from the paleo-habitats of the earliest known bipeds, which are consistent with the hypothesis that wading contributed to the adaptive pressure towards bipedality.

  19. Hand before foot? Cortical somatotopy suggests manual dexterity is primitive and evolved independently of bipedalism.

    PubMed

    Hashimoto, Teruo; Ueno, Kenichi; Ogawa, Akitoshi; Asamizuya, Takeshi; Suzuki, Chisato; Cheng, Kang; Tanaka, Michio; Taoka, Miki; Iwamura, Yoshiaki; Suwa, Gen; Iriki, Atsushi

    2013-11-19

    People have long speculated whether the evolution of bipedalism in early hominins triggered tool use (by freeing their hands) or whether the necessity of making and using tools encouraged the shift to upright gait. Either way, it is commonly thought that one led to the other. In this study, we sought to shed new light on the origins of manual dexterity and bipedalism by mapping the neural representations in the brain of the fingers and toes of living people and monkeys. Contrary to the 'hand-in-glove' notion outlined above, our results suggest that adaptations underlying tool use evolved independently of those required for human bipedality. In both humans and monkeys, we found that each finger was represented separately in the primary sensorimotor cortex just as they are physically separated in the hand. This reflects the ability to use each digit independently, as required for the complex manipulation involved in tool use. The neural mapping of the subjects' toes differed, however. In the monkeys, the somatotopic representation of the toes was fused, showing that the digits function predominantly as a unit in general grasping. Humans, by contrast, had an independent neurological representation of the big toe (hallux), suggesting association with bipedal locomotion. These observations suggest that the brain circuits for the hand had advanced beyond simple grasping, whereas our primate ancestors were still general arboreal quadrupeds. This early adaptation laid the foundation for the evolution of manual dexterity, which was preserved and enhanced in hominins. In hominins, a separate adaptation, involving the neural separation of the big toe, apparently occurred with bipedality. This accords with the known fossil evidence, including the recently reported hominin fossils which have been dated to 4.4 million years ago.

  20. Does Bipedality Predict the Group-Level Manual Laterality in Mammals?

    PubMed Central

    Giljov, Andrey; Karenina, Karina; Malashichev, Yegor

    2012-01-01

    Background Factors determining patterns of laterality manifestation in mammals remain unclear. In primates, the upright posture favours the expression of manual laterality across species, but may have little influence within a species. Whether the bipedalism acts the same in non-primate mammals is unknown. Our recent findings in bipedal and quadrupedal marsupials suggested that differences in laterality pattern, as well as emergence of manual specialization in evolution might depend on species-specific body posture. Here, we evaluated the hypothesis that the postural characteristics are the key variable shaping the manual laterality expression across mammalian species. Methodology/Principal Findings We studied forelimb preferences in a most bipedal marsupial, brush-tailed bettong, Bettongia penicillata in four different types of unimanual behavior. The significant left-forelimb preference at the group level was found in all behaviours studied. In unimanual feeding on non-living food, catching live prey and nest-material collecting, all or most subjects were lateralized, and among lateralized bettongs a significant majority displayed left-forelimb bias. Only in unimanual supporting of the body in the tripedal stance the distribution of lateralized and non-lateralized individuals did not differ from chance. Individual preferences were consistent across all types of behaviour. The direction or the strength of forelimb preferences were not affected by the animals’ sex. Conclusions/Significance Our findings support the hypothesis that the expression of manual laterality depends on the species-typical postural habit. The interspecies comparison illustrates that in marsupials the increase of bipedality corresponds with the increase of the degree of group-level forelimb preference in a species. Thus, bipedalism can predict pronounced manual laterality at both intra- and interspecific levels in mammals. We also conclude that quadrupedal position in biped species can

  1. Does bipedality predict the group-level manual laterality in mammals?

    PubMed

    Giljov, Andrey; Karenina, Karina; Malashichev, Yegor

    2012-01-01

    Factors determining patterns of laterality manifestation in mammals remain unclear. In primates, the upright posture favours the expression of manual laterality across species, but may have little influence within a species. Whether the bipedalism acts the same in non-primate mammals is unknown. Our recent findings in bipedal and quadrupedal marsupials suggested that differences in laterality pattern, as well as emergence of manual specialization in evolution might depend on species-specific body posture. Here, we evaluated the hypothesis that the postural characteristics are the key variable shaping the manual laterality expression across mammalian species. We studied forelimb preferences in a most bipedal marsupial, brush-tailed bettong, Bettongia penicillata in four different types of unimanual behavior. The significant left-forelimb preference at the group level was found in all behaviours studied. In unimanual feeding on non-living food, catching live prey and nest-material collecting, all or most subjects were lateralized, and among lateralized bettongs a significant majority displayed left-forelimb bias. Only in unimanual supporting of the body in the tripedal stance the distribution of lateralized and non-lateralized individuals did not differ from chance. Individual preferences were consistent across all types of behaviour. The direction or the strength of forelimb preferences were not affected by the animals' sex. Our findings support the hypothesis that the expression of manual laterality depends on the species-typical postural habit. The interspecies comparison illustrates that in marsupials the increase of bipedality corresponds with the increase of the degree of group-level forelimb preference in a species. Thus, bipedalism can predict pronounced manual laterality at both intra- and interspecific levels in mammals. We also conclude that quadrupedal position in biped species can slightly hinder the expression of manual laterality, but the evoked biped

  2. Comparison of nonmicroprocessor knee mechanism versus C-Leg on Prosthesis Evaluation Questionnaire, stumbles, falls, walking tests, stair descent, and knee preference.

    PubMed

    Kahle, Jason T; Highsmith, M Jason; Hubbard, Sandra L

    2008-01-01

    This study compared subjects' performance with a nonmicroprocessor knee mechanism (NMKM) versus a C-Leg on nine clinically repeatable evaluative measures. We recorded data on subjects' performance while they used an accommodated NMKM and, following a 90-day accommodation period, the C-Leg in a convenience sample of 19 transfemoral (TF) amputees (mean age 51 +/- 19) from an outpatient prosthetic clinic. We found that use of the C-Leg improved function in all outcomes: (1) Prosthesis Evaluation Questionnaire scores increased 20% (p = 0.007), (2) stumbles decreased 59% (p = 0.006), (3) falls decreased 64% (p = 0.03), (4) 75 m self-selected walking speed on even terrain improved 15% (p = 0.03), (5) 75 m fastest possible walking speed (FPWS) on even terrain improved 12% (p = 0.005), (6) 38 m FPWS on uneven terrain improved 21% (p < 0.001), (7) 6 m FPWS on even terrain improved 17% (p = 0.001), (8) Montreal Rehabilitation Performance Profile Performance Composite Scores for stair descent increased for 12 subjects, and (9) the C-Leg was preferred over the NMKM by 14 subjects. Four limited community ambulators (Medicare Functional Classification Level [MFCL] K2) increased their ambulatory functional level to unlimited community ambulation (MFCL K3). Objective evaluative clinical measures are vital for justifying the medical necessity of knee mechanisms for TF amputees. Use of the C-Leg improves performance and quality of life and can increase MFCL and community ambulation level.

  3. Phase-dependent reversal of the crossed conditioning effect on the soleus Hoffmann reflex from cutaneous afferents during walking in humans.

    PubMed

    Suzuki, Shinya; Nakajima, Tsuyoshi; Futatsubashi, Genki; Mezzarane, Rinaldo A; Ohtsuka, Hiroyuki; Ohki, Yukari; Komiyama, Tomoyoshi

    2016-02-01

    We previously demonstrated that non-noxious electrical stimulation of the cutaneous nerve innervating the contralateral foot modified the excitability of the Hoffmann (H-) reflex in the soleus muscle (SOL) in a task-dependent manner during standing and walking in humans. To date, however, it remains unclear how the crossed conditioning effect on the SOL H-reflex from the contralateral foot is modified during the various phases of walking. We sought to answer this question in the present study. The SOL H-reflex was evoked in healthy volunteers by an electrical test stimulation (TS) of the right (ipsilateral) posterior tibial nerve at five different phases during treadmill walking (4 km/h). A non-noxious electrical stimulation was delivered to the superficial peroneal nerve of the left (contralateral) ankle ~100 ms before the TS as a conditioning stimulation (CS). This CS significantly suppressed the H-reflex amplitude during the early stance phase, whereas the same CS significantly facilitated the H-reflex amplitude during the late stance phase. The CS alone did not produce detectable changes in the full-wave rectified electromyogram of the SOL. This result indicates that presynaptic mechanisms driven by the activation of low-threshold cutaneous afferents in the contralateral foot play a role in regulating the transmission between the Ia terminal and motoneurons in a phase-dependent manner. The modulation pattern of the crossed conditioning effect on the SOL H-reflex may be functionally relevant for the left-right coordination of leg movements during bipedal walking.

  4. Mechanical Perturbations of the Walking Surface Reveal Unaltered Axial Trunk Stiffness in Chronic Low Back Pain Patients

    PubMed Central

    Meijer, Onno G.

    2016-01-01

    Introduction Patients with chronic low back pain (CLBP) often demonstrate altered timing of thorax rotations in the transverse plane during gait. Increased axial trunk stiffness has been claimed to cause this movement pattern. Objectives The objective of this study was to assess whether axial trunk stiffness is increased in gait in CLBP patients. Methods 15 CLBP patients and 15 healthy controls walked on a treadmill that imposed rotational perturbations in the transverse plane. The effect of these perturbations on transverse pelvis, thorax and trunk (thorax relative to pelvis) rotations was evaluated in terms of residual rotations, i.e., the deviation of these movements from the unperturbed patterns. In view of the heterogeneity of the CLBP group, we additionally performed a subgroup comparison between seven patients and seven controls with maximal between-group contrast for timing of thorax rotations. Results Rotations of the walking surface had a clear effect on transverse pelvis, thorax and trunk rotations in all groups. No significant between-group differences on residual transverse pelvis, thorax and trunk rotations were observed. Conclusion Axial trunk stiffness in gait does not appear to be increased in CLBP. Altered timing of thorax rotations in CLBP does not seem to be a result of increased axial trunk stiffness. PMID:27310528

  5. The influence of push-off timing in a robotic ankle-foot prosthesis on the energetics and mechanics of walking.

    PubMed

    Malcolm, Philippe; Quesada, Roberto E; Caputo, Joshua M; Collins, Steven H

    2015-02-22

    Robotic ankle-foot prostheses that provide net positive push-off work can reduce the metabolic rate of walking for individuals with amputation, but benefits might be sensitive to push-off timing. Simple walking models suggest that preemptive push-off reduces center-of-mass work, possibly reducing metabolic rate. Studies with bilateral exoskeletons have found that push-off beginning before leading leg contact minimizes metabolic rate, but timing was not varied independently from push-off work, and the effects of push-off timing on biomechanics were not measured. Most lower-limb amputations are unilateral, which could also affect optimal timing. The goal of this study was to vary the timing of positive prosthesis push-off work in isolation and measure the effects on energetics, mechanics and muscle activity. We tested 10 able-bodied participants walking on a treadmill at 1.25 m · s(-1). Participants wore a tethered ankle-foot prosthesis emulator on one leg using a rigid boot adapter. We programmed the prosthesis to apply torque bursts that began between 46% and 56% of stride in different conditions. We iteratively adjusted torque magnitude to maintain constant net positive push-off work. When push-off began at or after leading leg contact, metabolic rate was about 10% lower than in a condition with Spring-like prosthesis behavior. When push-off began before leading leg contact, metabolic rate was not different from the Spring-like condition. Early push-off led to increased prosthesis-side vastus medialis and biceps femoris activity during push-off and increased variability in step length and prosthesis loading during push-off. Prosthesis push-off timing had no influence on intact-side leg center-of-mass collision work. Prosthesis push-off timing, isolated from push-off work, strongly affected metabolic rate, with optimal timing at or after intact-side heel contact. Increased thigh muscle activation and increased human variability appear to have caused the lack

  6. The biomechanics of walking shape the use of visual information during locomotion over complex terrain

    PubMed Central

    Matthis, Jonathan Samir; Barton, Sean L.; Fajen, Brett R.

    2015-01-01

    The aim of this study was to examine how visual information is used to control stepping during locomotion over terrain that demands precision in the placement of the feet. More specifically, we sought to determine the point in the gait cycle at which visual information about a target is no longer needed to guide accurate foot placement. Subjects walked along a path while stepping as accurately as possible on a series of small, irregularly spaced target footholds. In various conditions, each of the targets became invisible either during the step to the target or during the step to the previous target. We found that making targets invisible after toe off of the step to the target had little to no effect on stepping accuracy. However, when targets disappeared during the step to the previous target, foot placement became less accurate and more variable. The findings suggest that visual information about a target is used prior to initiation of the step to that target but is not needed to continuously guide the foot throughout the swing phase. We propose that this style of control is rooted in the biomechanics of walking, which facilitates an energetically efficient strategy in which visual information is primarily used to initialize the mechanical state of the body leading into a ballistic movement toward the target foothold. Taken together with previous studies, the findings suggest the availability of visual information about the terrain near a particular step is most essential during the latter half of the preceding step, which constitutes a critical control phase in the bipedal gait cycle. PMID:25788704

  7. The biomechanics of walking shape the use of visual information during locomotion over complex terrain.

    PubMed

    Matthis, Jonathan Samir; Barton, Sean L; Fajen, Brett R

    2015-03-18

    The aim of this study was to examine how visual information is used to control stepping during locomotion over terrain that demands precision in the placement of the feet. More specifically, we sought to determine the point in the gait cycle at which visual information about a target is no longer needed to guide accurate foot placement. Subjects walked along a path while stepping as accurately as possible on a series of small, irregularly spaced target footholds. In various conditions, each of the targets became invisible either during the step to the target or during the step to the previous target. We found that making targets invisible after toe off of the step to the target had little to no effect on stepping accuracy. However, when targets disappeared during the step to the previous target, foot placement became less accurate and more variable. The findings suggest that visual information about a target is used prior to initiation of the step to that target but is not needed to continuously guide the foot throughout the swing phase. We propose that this style of control is rooted in the biomechanics of walking, which facilitates an energetically efficient strategy in which visual information is primarily used to initialize the mechanical state of the body leading into a ballistic movement toward the target foothold. Taken together with previous studies, the findings suggest the availability of visual information about the terrain near a particular step is most essential during the latter half of the preceding step, which constitutes a critical control phase in the bipedal gait cycle. © 2015 ARVO.

  8. An analysis of the mechanisms for reducing the knee adduction moment during walking using a variable stiffness shoe in subjects with knee osteoarthritis.

    PubMed

    Jenkyn, Thomas R; Erhart, Jennifer C; Andriacchi, Thomas P

    2011-04-29

    Variable stiffness shoes that have a stiffer lateral than medial sole may reduce the external knee adduction moment (EKAM) and pain during walking in patients with medial compartment knee osteoarthritis (OA). However, the mechanism by which EKAM may be reduced in the OA knee with this intervention remains unclear. Three hypotheses were tested in this study: (1) The reduction in EKAM during walking with the variable stiffness shoe is associated with a reduction in GRF magnitude and/or (2) frontal plane lever arm. (3) A reduction in frontal plane lever arm occurs either by moving the center of pressure laterally under the shoe and/or by dynamically reducing the medial component of GRF. Thirty-two subjects (20 male, 12 female; age: 58.7 ± 9.3 years; height: 1.62 ± 0.08 m; mass: 81.3 ± 14.6 kg) with medial compartment knee osteoarthritis were studied walking in a gait laboratory. The frontal plane lever arm was significantly reduced (1.62%, 0.07%ht, p=0.02) on the affected side while the magnitude of the GRF was not significantly changed. The reduction in the lever arm was weakly correlated with a medial shift in the COP. However, the combined medial shift in the COP and reduction in the medial GRF explained 50% of the change of the frontal plane lever arm. These results suggest that the medial shift in the COP at the foot produced by the intervention shoe stimulates an adaptive dynamic response during gait that reduces the frontal plane lever arm.

  9. The walking robot project

    NASA Technical Reports Server (NTRS)

    Williams, P.; Sagraniching, E.; Bennett, M.; Singh, R.

    1991-01-01

    A walking robot was designed, analyzed, and tested as an intelligent, mobile, and a terrain adaptive system. The robot's design was an application of existing technologies. The design of the six legs modified and combines well understood mechanisms and was optimized for performance, flexibility, and simplicity. The body design incorporated two tripods for walking stability and ease of turning. The electrical hardware design used modularity and distributed processing to drive the motors. The software design used feedback to coordinate the system and simple keystrokes to give commands. The walking machine can be easily adapted to hostile environments such as high radiation zones and alien terrain. The primary goal of the leg design was to create a leg capable of supporting a robot's body and electrical hardware while walking or performing desired tasks, namely those required for planetary exploration. The leg designers intent was to study the maximum amount of flexibility and maneuverability achievable by the simplest and lightest leg design. The main constraints for the leg design were leg kinematics, ease of assembly, degrees of freedom, number of motors, overall size, and weight.

  10. Oreopithecus was a bipedal ape after all: Evidence from the iliac cancellous architecture

    PubMed Central

    Rook, Lorenzo; Bondioli, Luca; Köhler, Meike; Moyà-Solà, Salvador; Macchiarelli, Roberto

    1999-01-01

    Textural properties and functional morphology of the hip bone cancellous network of Oreopithecus bambolii, a 9- to 7-million-year-old Late Miocene hominoid from Italy, provide insights into the postural and locomotor behavior of this fossil ape. Digital image processing of calibrated hip bone radiographs reveals the occurrence of trabecular features, which, in humans and fossil hominids, are related to vertical support of the body weight, i.e., to bipedality. PMID:10411955

  11. Ischial Form as an Indicator of Bipedal Kinematics in Early Hominins: A Test Using Extant Anthropoids.

    PubMed

    Lewton, Kristi L; Scott, Jeremiah E

    2017-05-01

    Human ischia contrast with those of great apes in being craniocaudally short and dorsally projecting. This configuration is thought to facilitate greater hip extension in humans during bipedal locomotion. This link has been used to infer kinematics in early hominins, but the consequences of variation in ischial configuration for gait remain uncertain. Kinematic data for a limited sample of extant nonhuman primates demonstrate that there is variation in hip extension in these taxa during bipedal behaviors-specifically, Hylobates and Ateles are capable of greater extension than Pan and Macaca. In this study, we tested the hypothesis that ischial length and orientation are functionally linked with hip extension during bipedalism among these taxa. As expected, humans have the shortest ischia, followed by gibbons, spider monkeys, chimpanzees, and macaques. Our predictions for ischial orientation are not supported, however: macaques, gibbons, and spider monkeys do not vary in this trait, and they have ischia that are less dorsally angled than that of the chimpanzee. The results for ischium length provide limited support for the idea that the early hominin Ardipithecus ramidus, with its long, caudally oriented ischium was not capable of humanlike extended-hip bipedalism, and that the ischial shortening observed in post-Ardipithecus hominins reflects a shift toward a more humanlike gait. In contrast, while our results do not necessarily refute a link between ischial orientation and hip extension in hominins, they do not provide comparative support, making changes in ischial orientation in this part of the fossil record more difficult to interpret. Anat Rec, 300:845-858, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. Technicolor walks at the LHC

    SciTech Connect

    Belyaev, Alexander; Foadi, Roshan; Frandsen, Mads T.; Jaervinen, Matti; Sannino, Francesco; Pukhov, Alexander

    2009-02-01

    We analyze the potential of the Large Hadron Collider (LHC) to observe signatures of phenomenologically viable walking technicolor models. We study and compare the Drell-Yan and vector boson fusion mechanisms for the production of composite heavy vectors. We find that the heavy vectors are most easily produced and detected via the Drell-Yan processes. The composite Higgs phenomenology is also studied. If technicolor walks at the LHC, its footprints will be visible and our analysis will help in uncovering them.

  13. Performance and three-dimensional kinematics of bipedal lizards during obstacle negotiation.

    PubMed

    Olberding, Jeffrey P; McBrayer, Lance D; Higham, Timothy E

    2012-01-15

    Bipedal running is common among lizard species, but although the kinematics and performance of this gait have been well characterized, the advantages in biologically relevant situations are still unclear. Obstacle negotiation is a task that is ecologically relevant to many animals while moving at high speeds, such as during bipedal running, yet little is known about how obstacles impact locomotion and performance. We examined the effects of obstacle negotiation on the kinematics and performance of lizards during bipedal locomotion. We quantified three-dimensional kinematics from high-speed video (500 Hz) of six-lined racerunners (Aspidoscelis sexlineata) running on a 3 m racetrack both with and without an obstacle spanning the width of the track. The lizards did not alter their kinematics prior to contacting the obstacle. Although contact with the obstacle caused changes to the hindlimb kinematics, mean forward speed did not differ between treatments. The deviation of the vertical position of the body center of mass did not differ between treatments, suggesting that in the absence of a cost to overall performance, lizards forgo maintaining normal kinematics while negotiating obstacles in favor of a steady body center of mass height to avoid destabilizing locomotion.

  14. Optimal bipedal interactions with dynamic terrain: synthesis and analysis via nonlinear programming

    NASA Astrophysics Data System (ADS)

    Hubicki, Christian; Goldman, Daniel; Ames, Aaron

    In terrestrial locomotion, gait dynamics and motor control behaviors are tuned to interact efficiently and stably with the dynamics of the terrain (i.e. terradynamics). This controlled interaction must be particularly thoughtful in bipeds, as their reduced contact points render them highly susceptible to falls. While bipedalism under rigid terrain assumptions is well-studied, insights for two-legged locomotion on soft terrain, such as sand and dirt, are comparatively sparse. We seek an understanding of how biological bipeds stably and economically negotiate granular media, with an eye toward imbuing those abilities in bipedal robots. We present a trajectory optimization method for controlled systems subject to granular intrusion. By formulating a large-scale nonlinear program (NLP) with reduced-order resistive force theory (RFT) models and jamming cone dynamics, the optimized motions are informed and shaped by the dynamics of the terrain. Using a variant of direct collocation methods, we can express all optimization objectives and constraints in closed-form, resulting in rapid solving by standard NLP solvers, such as IPOPT. We employ this tool to analyze emergent features of bipedal locomotion in granular media, with an eye toward robotic implementation.

  15. Two families with quadrupedalism, mental retardation, no speech, and infantile hypotonia (Uner Tan Syndrome Type-II); a novel theory for the evolutionary emergence of human bipedalism

    PubMed Central

    Tan, Uner

    2014-01-01

    Two consanguineous families with Uner Tan Syndrome (UTS) were analyzed in relation to self-organizing processes in complex systems, and the evolutionary emergence of human bipedalism. The cases had the key symptoms of previously reported cases of UTS, such as quadrupedalism, mental retardation, and dysarthric or no speech, but the new cases also exhibited infantile hypotonia and are designated UTS Type-II. There were 10 siblings in Branch I and 12 siblings in Branch II. Of these, there were seven cases exhibiting habitual quadrupedal locomotion (QL): four deceased and three living. The infantile hypotonia in the surviving cases gradually disappeared over a period of years, so that they could sit by about 10 years, crawl on hands and knees by about 12 years. They began walking on all fours around 14 years, habitually using QL. Neurological examinations showed normal tonus in their arms and legs, no Babinski sign, brisk tendon reflexes especially in the legs, and mild tremor. The patients could not walk in a straight line, but (except in one case) could stand up and maintain upright posture with truncal ataxia. Cerebello-vermial hypoplasia and mild gyral simplification were noted in their MRIs. The results of the genetic analysis were inconclusive: no genetic code could be identified as the triggering factor for the syndrome in these families. Instead, the extremely low socio-economic status of the patients was thought to play a role in the emergence of UTS, possibly by epigenetically changing the brain structure and function, with a consequent selection of ancestral neural networks for QL during locomotor development. It was suggested that UTS may be regarded as one of the unpredictable outcomes of self-organization within a complex system. It was also noted that the prominent feature of this syndrome, the diagonal-sequence habitual QL, generated an interference between ipsilateral hands and feet, as in non-human primates. It was suggested that this may have been

  16. Two families with quadrupedalism, mental retardation, no speech, and infantile hypotonia (Uner Tan Syndrome Type-II); a novel theory for the evolutionary emergence of human bipedalism.

    PubMed

    Tan, Uner

    2014-01-01

    Two consanguineous families with Uner Tan Syndrome (UTS) were analyzed in relation to self-organizing processes in complex systems, and the evolutionary emergence of human bipedalism. The cases had the key symptoms of previously reported cases of UTS, such as quadrupedalism, mental retardation, and dysarthric or no speech, but the new cases also exhibited infantile hypotonia and are designated UTS Type-II. There were 10 siblings in Branch I and 12 siblings in Branch II. Of these, there were seven cases exhibiting habitual quadrupedal locomotion (QL): four deceased and three living. The infantile hypotonia in the surviving cases gradually disappeared over a period of years, so that they could sit by about 10 years, crawl on hands and knees by about 12 years. They began walking on all fours around 14 years, habitually using QL. Neurological examinations showed normal tonus in their arms and legs, no Babinski sign, brisk tendon reflexes especially in the legs, and mild tremor. The patients could not walk in a straight line, but (except in one case) could stand up and maintain upright posture with truncal ataxia. Cerebello-vermial hypoplasia and mild gyral simplification were noted in their MRIs. The results of the genetic analysis were inconclusive: no genetic code could be identified as the triggering factor for the syndrome in these families. Instead, the extremely low socio-economic status of the patients was thought to play a role in the emergence of UTS, possibly by epigenetically changing the brain structure and function, with a consequent selection of ancestral neural networks for QL during locomotor development. It was suggested that UTS may be regarded as one of the unpredictable outcomes of self-organization within a complex system. It was also noted that the prominent feature of this syndrome, the diagonal-sequence habitual QL, generated an interference between ipsilateral hands and feet, as in non-human primates. It was suggested that this may have been

  17. Effect of walking speed on the gait of king penguins: An accelerometric approach.

    PubMed

    Willener, Astrid S T; Handrich, Yves; Halsey, Lewis G; Strike, Siobhán

    2015-12-21

    Little is known about non-human bipedal gaits. This is probably due to the fact that most large animals are quadrupedal and that non-human bipedal animals are mostly birds, whose primary form of locomotion is flight. Very little research has been conducted on penguin pedestrian locomotion with the focus instead on their associated high energy expenditure. In animals, tri-axial accelerometers are frequently used to estimate physiological energy cost, as well as to define the behaviour pattern of a species, or the kinematics of swimming. In this study, we showed how an accelerometer-based technique could be used to determine the biomechanical characteristics of pedestrian locomotion. Eight king penguins, which represent the only family of birds to have an upright bipedal gait, were trained to walk on a treadmill. The trunk tri-axial accelerations were recorded while the bird was walking at four different speeds (1.0, 1.2, 1.4 and 1.6km/h), enabling the amplitude of dynamic body acceleration along the three axes (amplitude of DBAx, DBAy and DBAz), stride frequency, waddling and leaning amplitude, as well as the leaning angle to be defined. The magnitude of the measured variables showed a significant increase with increasing speed, apart from the backwards angle of lean, which decreased with increasing speed. The variability of the measured variables also showed a significant increase with speed apart from the DBAz amplitude, the waddling amplitude, and the leaning angle, where no significant effect of the walking speed was found. This paper is the first approach to describe 3D biomechanics with an accelerometer on wild animals, demonstrating the potential of this technique.

  18. A model-experiment comparison of system dynamics for human walking and running.

    PubMed

    Lipfert, Susanne W; Günther, Michael; Renjewski, Daniel; Grimmer, Sten; Seyfarth, Andre

    2012-01-07

    The human musculo-skeletal system comprises high complexity which makes it difficult to identify underlying basic principles of bipedal locomotion. To tackle this challenge, a common approach is to strip away complexity and formulate a reductive model. With utter simplicity a bipedal spring-mass model gives good predictions of the human gait dynamics, however, it has not been fully investigated whether center of mass motion over time of walking and running is comparable between the model and the human body over a wide range of speed. To test the model's ability in this respect, we compare sagittal center of mass trajectories of model and human data for speeds ranging from 0.5 m/s to 4 m/s. For simulations, system parameters and initial conditions are extracted from experimental observations of 28 subjects. The leg parameters stiffness and length are extracted from functional fitting to the subjects' leg force-length curves. With small variations of the touch-down angle of the leg and the vertical position of the center of mass at apex, we find successful spring-mass simulations for moderate walking and medium running speeds. Predictions of the sagittal center of mass trajectories and ground reaction forces are good, but their amplitudes are overestimated, while contact time is underestimated. At faster walking speeds and slower running speeds we do not find successful model locomotion with the extent of allowed parameter variation. We conclude that the existing limitations may be improved by adding complexity to the model.

  19. A multi-scale finite element model for investigation of chondrocyte mechanics in normal and medial meniscectomy human knee joint during walking.

    PubMed

    Tanska, Petri; Mononen, Mika E; Korhonen, Rami K

    2015-06-01

    Mechanical signals experienced by chondrocytes (articular cartilage cells) modulate cell synthesis and cartilage health. Multi-scale modeling can be used to study how forces are transferred from joint surfaces through tissues to chondrocytes. Therefore, estimation of chondrocyte behavior during certain physical activities, such as walking, could provide information about how cells respond to normal and abnormal loading in joints. In this study, a 3D multi-scale model was developed for evaluating chondrocyte and surrounding peri- and extracellular matrix responses during gait loading within healthy and medial meniscectomy knee joints. The knee joint geometry was based on MRI, whereas the input used for gait loading was obtained from the literature. Femoral and tibial cartilages were modeled as fibril-reinforced poroviscoelastic materials, whereas menisci were considered as transversely isotropic. Fluid pressures in the chondrocyte and cartilage tissue increased up to 2MPa (an increase of 30%) in the meniscectomy joint compared to the normal, healthy joint. The elevated level of fluid pressure was observed during the entire stance phase of gait. A medial meniscectomy caused substantially larger (up to 60%) changes in maximum principal strains in the chondrocyte compared to those in the peri- or extracellular matrices. Chondrocyte volume or morphology did not change substantially due to a medial meniscectomy. Current findings suggest that during walking chondrocyte deformations are not substantially altered due to a medial meniscectomy, while abnormal joint loading exposes chondrocytes to elevated levels of fluid pressure and maximum principal strains (compared to strains in the peri- or extracellular matrices). These might contribute to cell viability and the onset of osteoarthritis.

  20. Greater Mechanical Loading During Walking Is Associated With Less Collagen Turnover in Individuals With Anterior Cruciate Ligament Reconstruction.

    PubMed

    Pietrosimone, Brian; Blackburn, J Troy; Harkey, Matthew S; Luc, Brittney A; Hackney, Anthony C; Padua, Darin A; Driban, Jeffrey B; Spang, Jeffrey T; Jordan, Joanne M

    2016-02-01

    Individuals who have sustained an anterior cruciate ligament (ACL) injury and undergo ACL reconstruction (ACLR) are at higher risk of developing knee osteoarthritis. It is hypothesized that altered knee loading may influence the underlying joint metabolism and hasten development of posttraumatic knee osteoarthritis. To explore the associations between serum biomarkers of cartilage metabolism and peak vertical ground-reaction force (vGRF) and vGRF loading rate in the injured and uninjured limbs of individuals with ACLR. Descriptive laboratory study. Patients with a history of a primary unilateral ACLR who had returned to unrestricted physical activity (N = 19) participated in the study. Resting blood was collected from each participant before completing 5 walking gait trials at a self-selected comfortable speed. Peak vGRF was extracted for both limbs during the first 50% of the stance phase of gait, and the linear vGRF loading rate was determined between heel strike and peak vGRF. Sera were assessed for collagen breakdown (collagen type II cleavage product [C2C]) and synthesis (collagen type II C-propeptide [CPII]), as well as aggrecan concentrations, via commercially available specific enzyme-linked immunosorbent assays. Pearson product-moment correlations (r) and Spearman rank-order correlations (ρ) were used to evaluate associations between loading characteristics and biomarkers of cartilage metabolism. Lower C2C:CPII ratios were associated with higher peak vGRF in the injured limb (ρ = -0.59, uncorrected P = .007). There were no significant associations between peak vGRF or linear vGRF loading rate and CPII, C2C, or aggrecan serum concentrations. Lower C2C:CPII ratios were associated with higher peak vGRF in the ACLR limb during gait, suggesting that higher peak loading in the ACLR limb is related to lower type II collagen breakdown relative to type II collagen synthesis. These data suggest that type II collagen synthesis may be higher relative to the amount

  1. The Walk Poem.

    ERIC Educational Resources Information Center

    Padgett, Ron

    2000-01-01

    Discusses the long history of writing poems about a walk, noting many titles. Notes four basic types of walk poems and includes one by American poet Bill Zavatksy, called "Class Walk With Notebooks After Storm." Offers numerous brief ideas for both the writing and the form of walk poems. (SR)

  2. The Walk Poem.

    ERIC Educational Resources Information Center

    Padgett, Ron

    2000-01-01

    Discusses the long history of writing poems about a walk, noting many titles. Notes four basic types of walk poems and includes one by American poet Bill Zavatksy, called "Class Walk With Notebooks After Storm." Offers numerous brief ideas for both the writing and the form of walk poems. (SR)

  3. Fire-Walking

    ERIC Educational Resources Information Center

    Willey, David

    2010-01-01

    This article gives a brief history of fire-walking and then deals with the physics behind fire-walking. The author has performed approximately 50 fire-walks, took the data for the world's hottest fire-walk and was, at one time, a world record holder for the longest fire-walk (www.dwilley.com/HDATLTW/Record_Making_Firewalks.html). He currently…

  4. Fire-Walking

    ERIC Educational Resources Information Center

    Willey, David

    2010-01-01

    This article gives a brief history of fire-walking and then deals with the physics behind fire-walking. The author has performed approximately 50 fire-walks, took the data for the world's hottest fire-walk and was, at one time, a world record holder for the longest fire-walk (www.dwilley.com/HDATLTW/Record_Making_Firewalks.html). He currently…

  5. Feeding strategies as revealed by the section moduli of the humerus bones in bipedal theropod dinosaurs

    NASA Astrophysics Data System (ADS)

    Lee, Scott; Richards, Zachary

    2015-03-01

    The section modulus of a bone is a measure of its ability to resist bending torques. Carnivorous dinosaurs presumably had strong arm bones to hold struggling prey during hunting. Some theropods are believed to have become herbivorous and such animals would not have needed such strong arms. In this work, the section moduli of the humerus bones of bipedal theropod dinosaurs (from Microvenator celer to Tyrannosaurus rex) are studied to determine the maximum bending loads their arms could withstand. The results show that bending strength is not of uniform importance to these magnificent animals. The predatory theropods had strong arms for use in hunting. In contrast, the herbivorous dinosaurs had weaker arms.

  6. Positive messaging promotes walking in older adults

    PubMed Central

    Notthoff, Nanna; Carstensen, Laura L.

    2014-01-01

    Walking is among the most cost-effective and accessible means of exercise. Mounting evidence suggests that walking may help to maintain physical and cognitive independence in old age by preventing a variety of health problems. However, older Americans fall far short of meeting the daily recommendations for walking. In two studies, we examined whether considering older adults’ preferential attention to positive information may effectively enhance interventions aimed at promoting walking. In Study 1, we compared the effectiveness of positive, negative, and neutral messages to encourage walking (as measured with pedometers). Older adults who were informed about the benefits of walking walked more than those who were informed about the negative consequences of failing to walk, whereas younger adults were unaffected by framing valence. In Study 2, we examined within-person change in walking in older adults in response to positively- or negatively-framed messages over a 28-day period. Once again, positively-framed messages more effectively promoted walking than negatively-framed messages, and the effect was sustained across the intervention period. Together, these studies suggest that consideration of age-related changes in preferences for positive and negative information may inform the design of effective interventions to promote healthy lifestyles. Future research is needed to examine the mechanisms underlying the greater effectiveness of positively as opposed to negatively framed messages and the generalizability of findings to other intervention targets and other subpopulations of older adults. PMID:24956001

  7. Stochastic surface walking reaction sampling for resolving heterogeneous catalytic reaction network: A revisit to the mechanism of water-gas shift reaction on Cu

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Jie; Shang, Cheng; Liu, Zhi-Pan

    2017-10-01

    Heterogeneous catalytic reactions on surface and interfaces are renowned for ample intermediate adsorbates and complex reaction networks. The common practice to reveal the reaction mechanism is via theoretical computation, which locates all likely transition states based on the pre-guessed reaction mechanism. Here we develop a new theoretical method, namely, stochastic surface walking (SSW)-Cat method, to resolve the lowest energy reaction pathway of heterogeneous catalytic reactions, which combines our recently developed SSW global structure optimization and SSW reaction sampling. The SSW-Cat is automated and massively parallel, taking a rough reaction pattern as input to guide reaction search. We present the detailed algorithm, discuss the key features, and demonstrate the efficiency in a model catalytic reaction, water-gas shift reaction on Cu(111) (CO + H2O → CO2 + H2). The SSW-Cat simulation shows that water dissociation is the rate-determining step and formic acid (HCOOH) is the kinetically favorable product, instead of the observed final products, CO2 and H2. It implies that CO2 and H2 are secondary products from further decomposition of HCOOH at high temperatures. Being a general purpose tool for reaction prediction, the SSW-Cat may be utilized for rational catalyst design via large-scale computations.

  8. Specializations in the lumbosacral vertebral canal and spinal cord of birds: evidence of a function as a sense organ which is involved in the control of walking.

    PubMed

    Necker, Reinhold

    2006-05-01

    Birds are bipedal animals with a center of gravity rostral to the insertion of the hindlimbs. This imposes special demands on keeping balance when moving on the ground. Recently, specializations in the lumbosacral region have been suggested to function as a sense organ of equilibrium which is involved in the control of walking. Morphological, electrophysiological, behavioral and embryological evidence for such a function is reviewed. Birds have two nearly independent kinds of locomotion and it is suggested that two different sense organs play an important role in their respective control: the vestibular organ during flight and the lumbosacral system during walking.

  9. From bipedalism to bicyclism: evolution in energetics and biomechanics of historic bicycles.

    PubMed

    Minetti, A E; Pinkerton, J; Zamparo, P

    2001-07-07

    We measured the metabolic cost (C) and mechanical work of riding historic bicycles at different speeds: these bicycles included the Hobby Horse (1820s), the Boneshaker (1860s), the High Wheeler (1870s), the Rover (1880s), the Safety (1890s) and a modern bicycle (1980s) as a mean of comparison. The rolling resistance and air resistance of each vehicle were assessed. The mechanical internal work (W(INT)) was measured from three-dimensional motion analysis of the Hobby Horse and modern bicycle moving on a treadmill at different speeds. The equation obtained from the modern bicycle data was applied to the other vehicles. We found the following results. (i) Apart from the Rover, which was introduced for safety reasons, every newly invented bicycle improved metabolic economy. (ii) The rolling resistance decreased with subsequent designs while the frontal area and, hence, aerodynamic drag was fairly constant (except for the High Wheeler). (iii) The saddle-assisted body weight relief (which was inaugurated by the Hobby Horse) was responsible for most of the reduction in metabolic cost compared with walking or running. Further reductions in C were due to decreases in stride/pedalling frequency and, hence, W(INT) at the same speeds. (iv) The introduction of gear ratios allowed the use of pedalling frequencies that optimize the power/contraction velocity properties of the propulsive muscles. As a consequence, net mechanical efficiency (the ratio between the total mechanical work and C) was almost constant (0.273 +/- 0.015s.d.) for all bicycle designs, despite the increase in cruising speed. In the period from 1820 to 1890, improved design of bicycles increased the metabolically equivalent speed by threefold compared with walking at an average pace of ca. + 0.5 ms(-1) per decade [corrected]. The speed gain was the result of concurrent technological advancements in wheeled, human-powered vehicles and of 'smart' adaptation of the same actuator (the muscle) to different

  10. From bipedalism to bicyclism: evolution in energetics and biomechanics of historic bicycles.

    PubMed Central

    Minetti, A. E.; Pinkerton, J.; Zamparo, P.

    2001-01-01

    We measured the metabolic cost (C) and mechanical work of riding historic bicycles at different speeds: these bicycles included the Hobby Horse (1820s), the Boneshaker (1860s), the High Wheeler (1870s), the Rover (1880s), the Safety (1890s) and a modern bicycle (1980s) as a mean of comparison. The rolling resistance and air resistance of each vehicle were assessed. The mechanical internal work (W(INT)) was measured from three-dimensional motion analysis of the Hobby Horse and modern bicycle moving on a treadmill at different speeds. The equation obtained from the modern bicycle data was applied to the other vehicles. We found the following results. (i) Apart from the Rover, which was introduced for safety reasons, every newly invented bicycle improved metabolic economy. (ii) The rolling resistance decreased with subsequent designs while the frontal area and, hence, aerodynamic drag was fairly constant (except for the High Wheeler). (iii) The saddle-assisted body weight relief (which was inaugurated by the Hobby Horse) was responsible for most of the reduction in metabolic cost compared with walking or running. Further reductions in C were due to decreases in stride/pedalling frequency and, hence, W(INT) at the same speeds. (iv) The introduction of gear ratios allowed the use of pedalling frequencies that optimize the power/contraction velocity properties of the propulsive muscles. As a consequence, net mechanical efficiency (the ratio between the total mechanical work and C) was almost constant (0.273 +/- 0.015s.d.) for all bicycle designs, despite the increase in cruising speed. In the period from 1820 to 1890, improved design of bicycles increased the metabolically equivalent speed by threefold compared with walking at an average pace of ca. + 0.5 ms(-1) per decade [corrected]. The speed gain was the result of concurrent technological advancements in wheeled, human-powered vehicles and of 'smart' adaptation of the same actuator (the muscle) to different

  11. Walking economy during cued versus non-cued self-selected treadmill walking in persons with Parkinson's disease.

    PubMed

    Gallo, Paul M; McIsaac, Tara L; Garber, Carol Ewing

    2014-01-01

    Gait impairments related to Parkinson's disease (PD) include variable step length and decreased walking velocity, which may result in poorer walking economy. Auditory cueing is a common method used to improve gait mechanics in PD that has been shown to worsen walking economy at set treadmill walking speeds. It is unknown if auditory cueing has the same effects on walking economy at self-selected treadmill walking speeds. To determine if auditory cueing will affect walking economy at self-selected treadmill walking speeds and at speeds slightly faster and slower than self-selected. Twenty-two participants with moderate PD performed three, 6-minute bouts of treadmill walking at three speeds (self-selected and ± 0.22 m·sec-1). One session used cueing and the other without cueing. Energy expenditure was measured and walking economy was calculated (energy expenditure/power). Poorer walking economy and higher energy expenditure occurred during cued walking at a self-selected and a slightly faster walking speed, but there was no apparent difference at the slightly slower speed. These results suggest that potential gait benefits of auditory cueing may come at an energy cost and poorer walking economy for persons with PD at least at some treadmill walking speeds.

  12. How Fast Can a Human Run? − Bipedal vs. Quadrupedal Running

    PubMed Central

    Kinugasa, Ryuta; Usami, Yoshiyuki

    2016-01-01

    Usain Bolt holds the current world record in the 100-m run, with a running time of 9.58 s, and has been described as the best human sprinter in history. However, this raises questions concerning the maximum human running speed, such as “Can the world’s fastest men become faster still?” The correct answer is likely “Yes.” We plotted the historical world records for bipedal and quadrupedal 100-m sprint times according to competition year. These historical records were plotted using several curve-fitting procedures. We found that the projected speeds intersected in 2048, when for the first time, the winning quadrupedal 100-m sprint time could be lower, at 9.276 s, than the winning bipedal time of 9.383 s. Video analysis revealed that in quadrupedal running, humans employed a transverse gallop with a small angular excursion. These results suggest that in the future, the fastest human on the planet might be a quadrupedal runner at the 2048 Olympics. This may be achieved by shifting up to the rotary gallop and taking longer strides with wide sagittal trunk motion. PMID:27446911

  13. Bipedality and hair loss in human evolution revisited: The impact of altitude and activity scheduling.

    PubMed

    Dávid-Barrett, Tamás; Dunbar, Robin I M

    2016-05-01

    Bipedality evolved early in hominin evolution, and at some point was associated with hair loss over most of the body. One classic explanation (Wheeler 1984: J. Hum. Evol. 13, 91-98) was that these traits evolved to reduce heat overload when australopiths were foraging in more open tropical habitats where they were exposed to the direct effects of sunlight at midday. A recent critique of this model (Ruxton & Wilkinson 2011a: Proc. Natl. Acad. Sci. USA 108, 20965-20969) argued that it ignored the endogenous costs of heat generated by locomotion, and concluded that only hair loss provided a significant reduction in heat load. We add two crucial corrections to this model (the altitude at which australopiths actually lived and activity scheduling) and show that when these are included there are substantial reductions in heat load for bipedal locomotion even for furred animals. In addition, we add one further consideration to the model: we extend the analysis across the full 24 h day, and show that fur loss could not have evolved until much later because of the thermoregulatory costs this would have incurred at the altitudes where australopiths actually lived. Fur loss is most likely associated with the exploitation of open habitats at much lower altitudes at a much later date by the genus Homo. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  14. A bipedal DNA motor that travels back and forth between two DNA origami tiles.

    PubMed

    Liber, Miran; Tomov, Toma E; Tsukanov, Roman; Berger, Yaron; Nir, Eyal

    2015-02-04

    In this work, the successful operation of a dynamic DNA device constructed from two DNA origami building blocks is reported. The device includes a bipedal walker that strides back and forth between the two origami tiles. Two different DNA origami tiles are first prepared separately; they are then joined together in a controlled manner by a set of DNA strands to form a stable track in high yield as confirmed by single-molecule fluorescence (SMF). Second, a bipedal DNA motor, initially attached to one of the two origami units and operated by sequential interaction with "fuel" and "antifuel" DNA strands, moves from one origami tile to another and then back again. The operational yield, measured by SMF, was similar to that of a motor operating on a similar track embedded in a single origami tile, confirming that the transfer across the junction from one tile to the other does not result in dissociation that is any more than that of steps on a single tile. These results demonstrate that moving parts can reliably travel from one origami unit to another, and it demonstrates the feasibility of dynamic DNA molecular machines that are made of more than a single origami building block. This study is a step toward the development of motors that can stride over micrometer distances. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. DNA Bipedal Motor Achieves a Large Number of Steps Due to Operation Using Microfluidics-Based Interface.

    PubMed

    Tomov, Toma E; Tsukanov, Roman; Glick, Yair; Berger, Yaron; Liber, Miran; Avrahami, Dorit; Gerber, Doron; Nir, Eyal

    2017-04-25

    Realization of bioinspired molecular machines that can perform many and diverse operations in response to external chemical commands is a major goal in nanotechnology, but current molecular machines respond to only a few sequential commands. Lack of effective methods for introduction and removal of command compounds and low efficiencies of the reactions involved are major reasons for the limited performance. We introduce here a user interface based on a microfluidics device and single-molecule fluorescence spectroscopy that allows efficient introduction and removal of chemical commands and enables detailed study of the reaction mechanisms involved in the operation of synthetic molecular machines. The microfluidics provided 64 consecutive DNA strand commands to a DNA-based motor system immobilized inside the microfluidics, driving a bipedal walker to perform 32 steps on a DNA origami track. The microfluidics enabled removal of redundant strands, resulting in a 6-fold increase in processivity relative to an identical motor operated without strand removal and significantly more operations than previously reported for user-controlled DNA nanomachines. In the motor operated without strand removal, redundant strands interfere with motor operation and reduce its performance. The microfluidics also enabled computer control of motor direction and speed. Furthermore, analysis of the reaction kinetics and motor performance in the absence of redundant strands, made possible by the microfluidics, enabled accurate modeling of the walker processivity. This enabled identification of dynamic boundaries and provided an explanation, based on the "trap state" mechanism, for why the motor did not perform an even larger number of steps. This understanding is very important for the development of future motors with significantly improved performance. Our universal interface enables two-way communication between user and molecular machine and, relying on concepts similar to that of solid

  16. The stabilizing properties of foot yaw in human walking.

    PubMed

    Rebula, John R; Ojeda, Lauro V; Adamczyk, Peter G; Kuo, Arthur D

    2017-02-28

    Humans perform a variety of feedback adjustments to maintain balance during walking. These include lateral footfall placement, and center of pressure adjustment under the stance foot, to stabilize lateral balance. A less appreciated possibility would be to steer for balance like a bicycle, whose front wheel may be turned toward the direction of a lean to capture the center of mass. Humans could potentially combine steering with other strategies to distribute balance adjustments across multiple degrees of freedom. We tested whether human balance can theoretically benefit from steering, and experimentally tested for evidence of steering for balance. We first developed a simple dynamic walking model, which shows that bipedal walking may indeed be stabilized through steering-externally rotating the foot about vertical toward the direction of lateral lean for each footfall-governed by linear feedback control. Moreover, least effort (mean-square control torque) is required if steering is combined with lateral foot placement. If humans use such control, footfall variability should show a statistical coupling between external rotation with lateral placement. We therefore examined the spontaneous fluctuations of hundreds of strides of normal overground walking in healthy adults (N=26). We found significant coupling (P=9·10(-8)), of 0.54rad of external rotation per meter of lateral foot deviation. Successive footfalls showed a weaker, negative correlation with each other, similar to how a bicycle׳s steering adjustment made for balance must be followed by gradual corrections to resume the original travel direction. Steering may be one of multiple strategies to stabilize balance during walking. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Gait or Walking Problems

    MedlinePlus

    Gait or Walking Problems the basic facts multiple sclerosis Many people with MS will experience difficulty with walking, which is also called ambulation. The term “gait” refers more specifically to the manner ...

  18. Toe Walking in Children

    MedlinePlus

    ... concern. Toe walking is sometimes the result of cerebral palsy, muscular dystrophy or another generalized disease of nerve ... can prevent the heel from touching the ground. Cerebral palsy. Toe walking can be caused by cerebral palsy — ...

  19. Locomotion by Abdopus aculeatus (Cephalopoda: Octopodidae): walking the line between primary and secondary defenses.

    PubMed

    Huffard, Christine L

    2006-10-01

    Speeds and variation in body form during crawling, bipedal walking, swimming and jetting by the shallow-water octopus Abdopus aculeatus were compared to explore possible interactions between defense behaviors and biomechanics of these multi-limbed organisms. General body postures and patterns were more complex and varied during the slow mode of crawling than during fast escape maneuvers such as swimming and jetting. These results may reflect a trade-off between predator deception and speed, or simply a need to reduce drag during jet-propelled locomotion. Octopuses swam faster when dorsoventrally compressed, a form that may generate lift, than when swimming in the head-raised posture. Bipedal locomotion proceeded as fast as swimming and can be considered a form of fast escape (secondary defense) that also incorporates elements of crypsis and polyphenism (primary defenses). Body postures during walking suggested the use of both static and dynamic stability. Absolute speed was not correlated with body mass in any mode. Based on these findings the implications for defense behaviors such as escape from predation, aggression, and 'flatfish mimicry' performed by A. aculeatus and other octopuses are discussed.

  20. On alternating quantum walks

    NASA Astrophysics Data System (ADS)

    Rousseva, Jenia; Kovchegov, Yevgeniy

    2017-03-01

    We study an inhomogeneous quantum walk on a line that evolves according to alternating coins, each a rotation matrix. For the quantum walk with the coin alternating between clockwise and counterclockwise rotations by the same angle, we derive a closed form solution for the propagation of probabilities, and provide its asymptotic approximation via the method of stationary phase. Finally, we observe that for a x03c0;/4 angle, this alternating rotation walk will replicate the renown Hadamard walk.

  1. Knuckle-walking anteater: a convergence test of adaptation for purported knuckle-walking features of African Hominidae.

    PubMed

    Orr, Caley M

    2005-11-01

    distal radius in the hominin lineage might be indicative of a knuckle-walking ancestry for bipedal hominins if interpreted within the biomechanical and phylogenetic context of hominid locomotor evolution. Copyright 2005 Wiley-Liss, Inc

  2. Walk This Way

    ERIC Educational Resources Information Center

    Mason, Nick

    2007-01-01

    A generation ago, it was part of growing up for all kids when they biked or walked to school. But in the last 30 years, heavier traffic, wider roads and more dangerous intersections have made it riskier for students walking or pedaling. Today, fewer than 15 percent of kids bike or walk to school compared with more than 50 percent in 1969. In the…

  3. Walk This Way

    ERIC Educational Resources Information Center

    Mason, Nick

    2007-01-01

    A generation ago, it was part of growing up for all kids when they biked or walked to school. But in the last 30 years, heavier traffic, wider roads and more dangerous intersections have made it riskier for students walking or pedaling. Today, fewer than 15 percent of kids bike or walk to school compared with more than 50 percent in 1969. In the…

  4. Quantum walk computation

    SciTech Connect

    Kendon, Viv

    2014-12-04

    Quantum versions of random walks have diverse applications that are motivating experimental implementations as well as theoretical studies. Recent results showing quantum walks are “universal for quantum computation” relate to algorithms, to be run on quantum computers. We consider whether an experimental implementation of a quantum walk could provide useful computation before we have a universal quantum computer.

  5. Walking Wellness. Student Workbook.

    ERIC Educational Resources Information Center

    Sweetgall, Robert; Neeves, Robert

    This comprehensive student text and workbook, for grades four through eight, contains 16 workshop units focusing on walking field trips, aerobic pacing concepts, walking techniques, nutrition, weight control and healthy life-style planning. Co-ordinated homework assignments are included. The appendixes include 10 tips for walking, a calorie chart,…

  6. Walking Wellness. Student Workbook.

    ERIC Educational Resources Information Center

    Sweetgall, Robert; Neeves, Robert

    This comprehensive student text and workbook, for grades four through eight, contains 16 workshop units focusing on walking field trips, aerobic pacing concepts, walking techniques, nutrition, weight control and healthy life-style planning. Co-ordinated homework assignments are included. The appendixes include 10 tips for walking, a calorie chart,…

  7. Decentralized Feedback Controllers for Exponential Stabilization of Hybrid Periodic Orbits: Application to Robotic Walking*

    PubMed Central

    Hamed, Kaveh Akbari; Gregg, Robert D.

    2016-01-01

    This paper presents a systematic algorithm to design time-invariant decentralized feedback controllers to exponentially stabilize periodic orbits for a class of hybrid dynamical systems arising from bipedal walking. The algorithm assumes a class of parameterized and nonlinear decentralized feedback controllers which coordinate lower-dimensional hybrid subsystems based on a common phasing variable. The exponential stabilization problem is translated into an iterative sequence of optimization problems involving bilinear and linear matrix inequalities, which can be easily solved with available software packages. A set of sufficient conditions for the convergence of the iterative algorithm to a stabilizing decentralized feedback control solution is presented. The power of the algorithm is demonstrated by designing a set of local nonlinear controllers that cooperatively produce stable walking for a 3D autonomous biped with 9 degrees of freedom, 3 degrees of underactuation, and a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg. PMID:27990059

  8. Does elevated osteopontin level play an important role in the development of scoliosis in bipedal mice?

    PubMed

    Xie, Ning; Li, Mo; Wu, Tao; Liu, Jun; Wang, Binbin; Tang, Feng

    2015-07-01

    Previous studies implied indirectly that an elevated osteopontin (OPN) level might play a key role in the pathomechanism of adolescent idiopathic scoliosis. Nonetheless, up to now, no direct evidence was proposed to determine this issue. The aim was to determine the role of OPN in the pathomechanism of scoliosis. This was an experimental study to investigate the role of OPN in a bipedal mouse scoliosis model. All procedures were performed under the approval and supervision of the Institutional Animal Care and Use Committee of our university. A new bipedal mouse model with elevated OPN level was established in this study. Amputation of forelimbs and tail was performed on 80 male C3H/HeJ mice at the age of 3 weeks. Then, these mice were randomly divided into two groups: Group A consisted of 40 mice treated with OPN 40 mg/kg daily and Group B consisted of the remaining 40 mice treated with saline. Then, 40 quadruped mice with saline were included in Group C. Body length, X-rays, and computed tomographic scans were obtained at the twentieth week. Then, scoliosis incidence, curve magnitude, and circulating OPN level were compared among groups. Osteopontin level was significantly higher in Group A compared with that in Groups B and C. Spine deformity was identified in 37 mice in Group A, 21 mice in Group B, and 5 mice in Group C. The average Cobb angle was 29.8° in Group A, 20.9° in Group B, and 17.5° in Group C. Although no significant difference of body length was found, significant statistical difference was noted in terms of scoliosis incidence and curve magnitude, among the three groups. The results of the present study indicated that the elevated OPN level might play an important role in the etiopathogenesis of scoliosis, that is, it not only raises the risk for scoliosis in bipedal mice but also contributes to curve progression. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Self-reported walking ability predicts functional mobility performance in frail older adults.

    PubMed

    Alexander, N B; Guire, K E; Thelen, D G; Ashton-Miller, J A; Schultz, A B; Grunawalt, J C; Giordani, B

    2000-11-01

    To determine how self-reported physical function relates to performance in each of three mobility domains: walking, stance maintenance, and rising from chairs. Cross-sectional analysis of older adults. University-based laboratory and community-based congregate housing facilities. Two hundred twenty-one older adults (mean age, 79.9 years; range, 60-102 years) without clinical evidence of dementia (mean Folstein Mini-Mental State score, 28; range, 24-30). We compared the responses of these older adults on a questionnaire battery used by the Established Populations for the Epidemiologic Study of the Elderly (EPESE) project, to performance on mobility tasks of graded difficulty. Responses to the EPESE battery included: (1) whether assistance was required to perform seven Katz activities of daily living (ADL) items, specifically with walking and transferring; (2) three Rosow-Breslau items, including the ability to walk up stairs and walk a half mile; and (3) five Nagi items, including difficulty stooping, reaching, and lifting objects. The performance measures included the ability to perform, and time taken to perform, tasks in three summary score domains: (1) walking ("Walking," seven tasks, including walking with an assistive device, turning, stair climbing, tandem walking); (2) stance maintenance ("Stance," six tasks, including unipedal, bipedal, tandem, and maximum lean); and (3) chair rise ("Chair Rise," six tasks, including rising from a variety of seat heights with and without the use of hands for assistance). A total score combines scores in each Walking, Stance, and Chair Rise domain. We also analyzed how cognitive/ behavioral factors such as depression and self-efficacy related to the residuals from the self-report and performance-based ANOVA models. Rosow-Breslau items have the strongest relationship with the three performance domains, Walking, Stance, and Chair Rise (eta-squared ranging from 0.21 to 0.44). These three performance domains are as strongly

  10. Mechanical analysis of infant carrying in hominoids

    NASA Astrophysics Data System (ADS)

    Amaral, Lia Q.

    2008-04-01

    In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair-hair friction coefficient, and body angle exists. The hair-hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here.

  11. Mechanical analysis of infant carrying in hominoids

    PubMed Central

    2007-01-01

    In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair–hair friction coefficient, and body angle exists. The hair–hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here. PMID:18030438

  12. Mechanical analysis of infant carrying in hominoids.

    PubMed

    Amaral, Lia Q

    2008-04-01

    In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair-hair friction coefficient, and body angle exists. The hair-hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here.

  13. Emergence of bipedal locomotion through entrainment among the neuro-musculo-skeletal system and the environment

    NASA Astrophysics Data System (ADS)

    Taga, Gentaro

    1994-08-01

    A principle of locomotor control in an unpredictably changing environment is presented on the basis of neurophysiology and biomechanics from the perspective of nonlinear dynamics theory. Locomotor movements emerge as a limit cycle generated through global entrainment among the neuro-musculo-skeletal system and the environment. A computer simulation of a specific model of bipedal locomotion shows its ability to adapt to a changing environment in real-time. The stability of the limit cycle is maintained despite the presence of time delays in transporting and processing information between the neural rhythm generator and the musculo-skeletal system. With considerable time delays, however, the locomotor pattern becomes chaotic, which is compared with a gait of patients with neural deficits. A general framework for motor control is discussed toward the control of movements in an unpredictable environment.

  14. The evolutionary origins of obstructed labor: bipedalism, encephalization, and the human obstetric dilemma.

    PubMed

    Wittman, Anna Blackburn; Wall, L Lewis

    2007-11-01

    Obstructed labor is a common complication of human childbirth. In parts of the world where access to emergency obstetric services is limited, obstructed labor is a major cause of maternal mortality. Women who survive the ordeal of prolonged obstructed labor often end up suffering from an obstetric vesicovaginal fistula or another serious birth injury that leaves them crippled for life. Compared with the other higher primates (chimpanzees, bonobos, gorillas, and orangutans), these problems are uniquely human. This article reviews the evolutionary origins of the human obstetric dilemma with special reference to the changes imposed on pelvic architecture by the assumption of upright, bipedal posture and locomotion. The subsequent development of progressively increasing brain size (encephalization) in hominins led to the present human obstetrical conundrum: how to balance the evolutionary advantage of bigger babies with larger brains against the presence of a narrow pelvis that is difficult for a fetus to traverse during labor.

  15. Intra-task variability of trunk coordination during a rate-controlled bipedal dance jump.

    PubMed

    Smith, Jo Armour; Siemienski, Adam; Popovich, John M; Kulig, Kornelia

    2012-01-01

    In this study, we investigated trunk coordination during rate-controlled bipedal vertical dance jumps. The aims of the study were to investigate the pattern of coordination and the magnitude of coordination variability within jump phases and relative to phase-defining events during the jump. Lumbar and thoracic kinematics were collected from seven dancers during a series of jumps at 95 beats per minute. The vector coding technique was used to quantify the pattern and variability of trunk coordination. Coordination was predominantly anti-phase during propulsion and landing. Mean coordination variability peaked just before the landing phase and at the transition from landing to propulsion phases, and was lowest during the propulsion phase just before toe-off. The results indicate that peaks in variability could be explained by task and phase-specific biomechanical demands.

  16. Walk Score®

    PubMed Central

    Brown, Scott C.; Pantin, Hilda; Lombard, Joanna; Toro, Matthew; Huang, Shi; Plater-Zyberk, Elizabeth; Perrino, Tatiana; Perez-Gomez, Gianna; Barrera-Allen, Lloyd; Szapocznik, José

    2013-01-01

    Background Walk Score® is a nationally and publicly available metric of neighborhood walkability based on proximity to amenities (e.g., retail, food, schools). However, few studies have examined the relationship of Walk Score to walking behavior. Purpose To examine the relationship of Walk Score to walking behavior in a sample of recent Cuban immigrants, who overwhelmingly report little choice in their selection of neighborhood built environments when they arrive in the U.S. Methods Participants were 391 recent healthy Cuban immigrants (M age=37.1 years) recruited within 90 days of arrival in the U.S., and assessed within 4 months of arrival (M=41.0 days in the U.S.), who resided throughout Miami-Dade County FL. Data on participants’ addresses, walking and sociodemographics were collected prospectively from 2008 to 2010. Analyses conducted in 2011 examined the relationship of Walk Score for each participant’s residential address in the U.S. to purposive walking, controlling for age, gender, education, BMI, days in the U.S., and habitual physical activity level in Cuba. Results For each 10-point increase in Walk Score, adjusting for covariates, there was a significant 19% increase in the likelihood of purposive walking, a 26% increase in the likelihood of meeting physical activity recommendations by walking, and 27% more minutes walked in the previous week. Conclusions Results suggest that Walk Score is associated with walking in a sample of recent immigrants who initially had little choice in where they lived in the U.S. These results support existing guidelines indicating that mixed land use (such as parks and restaurants near homes) should be included when designing walkable communities. PMID:23867028

  17. Role of Enhanced Central Leptin Activity in a Scoliosis Model Created in Bipedal Amputated Mice.

    PubMed

    Wu, Tao; Sun, Xu; Zhu, Zezhang; Yan, Huang; Guo, Jing; Cheng, Jack C Y; Qiu, Yong

    2015-10-01

    An experimental study to investigate the role of enhanced central leptin activity in a bipedal mouse scoliosis model. To investigate the influence of enhanced central leptin activity on the development of scoliosis in mice, and to support Burwell's hypothesis that central leptin dysfunction is involved in the etiopathogenesis of idiopathic scoliosis. Significantly lower level of circulating leptin and higher level of soluble leptin receptor have been reported in adolescent idiopathic scoliosis compared with healthy adolescents, suggesting possible association between abnormal central leptin level and dysfunction. Amputation of forelimbs and tail was performed on 50 male C3H/HeJ mice at the age of 3 weeks. Then, the mice were randomly divided into 2 groups: Group A consisted of 25 mice treated with injection into the hypothalamus with lentivirus vectors that overexpressed leptin; and Group B involved the remaining 25 mice receiving intracerebral injection with the control vectors. Radiographs were obtained at 20th week to determine the presence of spinal deformity. The incidence of scoliosis and curve magnitude were compared between groups. The body weight was initially found to be slightly lower in mice of Group A when compared with Group B. Significantly higher peripheral serum leptin level was found in leptin-overexpressing mice than control mice. Scoliosis developed in 23 mice of Group A (92%), with an average Cobb angle of 30.2°, and in 13 of Group B (52%), with an average Cobb angle of 18.4°, respectively. A higher incidence (P = 0.002) and more severe curve (P <0.001) were observed in Group A. In this bipedal mouse scoliosis model, enhanced central leptin activity might not only increase the risk of developing a scoliosis, but also contribute to the progression of scoliosis. N/A.

  18. Water-walking devices

    NASA Astrophysics Data System (ADS)

    Hu, David L.; Prakash, Manu; Chan, Brian; Bush, John W. M.

    2007-11-01

    We report recent efforts in the design and construction of water-walking machines inspired by insects and spiders. The fundamental physical constraints on the size, proportion and dynamics of natural water-walkers are enumerated and used as design criteria for analogous mechanical devices. We report devices capable of rowing along the surface, leaping off the surface and climbing menisci by deforming the free surface. The most critical design constraint is that the devices be lightweight and non-wetting. Microscale manufacturing techniques and new man-made materials such as hydrophobic coatings and thermally actuated wires are implemented. Using high-speed cinematography and flow visualization, we compare the functionality and dynamics of our devices with those of their natural counterparts.

  19. Water-walking devices

    NASA Astrophysics Data System (ADS)

    Hu, David L.; Prakash, Manu; Chan, Brian; Bush, John W. M.

    We report recent efforts in the design and construction of water-walking machines inspired by insects and spiders. The fundamental physical constraints on the size, proportion and dynamics of natural water-walkers are enumerated and used as design criteria for analogous mechanical devices. We report devices capable of rowing along the surface, leaping off the surface and climbing menisci by deforming the free surface. The most critical design constraint is that the devices be lightweight and non-wetting. Microscale manufacturing techniques and new man-made materials such as hydrophobic coatings and thermally actuated wires are implemented. Using highspeed cinematography and flow visualization, we compare the functionality and dynamics of our devices with those of their natural counterparts.

  20. Rhythm Pattern of Sole through Electrification of the Human Body When Walking

    NASA Astrophysics Data System (ADS)

    Takiguchi, Kiyoaki; Wada, Takayuki; Tohyama, Shigeki

    The rhythm of automatic cyclic movements such as walking is known to be generated by a rhythm generator called CPG in the spinal cord. The measurement of rhythm characteristics in walking is considered to be important for analyzing human bipedal walking and adaptive walking on irregular terrain. In particular, the soles that contact the terrain surface perform flexible movements similar to the movement of the fins of a lungfish, which is considered to be the predecessor of land animals. The sole movements are believed to be a basic movement acquired during prehistoric times. The detailed rhythm pattern of sole motion is considered to be important. We developed a method for measuring electrification without installing device on a subject's body and footwear for stabilizing the electrification of the human body. We measured the rhythm pattern of 20 subjects including 4 infants when walking by using this system and the corresponding equipment. Therefore, we confirmed the commonality of the correlative rhythm patterns of 20 subjects. Further, with regard to an individual subject, the reproducibility of a rhythm pattern with strong correlation coefficient > 0.93 ± 0.5 (mean ± SD) concerning rhythms of trials that are differently conducted on adult subjects could be confirmed.

  1. Development of energy and time parameters in the walking of healthy human infants.

    PubMed

    Kimura, Tasuku; Yaguramaki, Naoko; Fujita, Masaki; Ogiue-Ikeda, Mari; Nishizawa, Satoshi; Ueda, Yutaka

    2005-11-01

    Sixteen infants were analyzed longitudinally from the onset of independent walking to 3 years of age using time parameters, speed and energy recovery. Considerable variation and irregularities were observed in many parameters of infant walking, especially until 13 months of age when infants had difficulty in walking steadily step by step. Infant walking until 3 years of age was characterized by a small braking duration, caused mainly by the forward inclination of the trunk, a large relative stance phase duration, which maintained static balance, short stride length, due to the small range of the lower limb joint angle, and a small recovery of external energy. These characteristics were also predominantly evident until 13 months of age. The small recovery characteristic of infants was caused by flexed lower limb joints, pronounced irregularities in energy output, and in younger infants, slow speed. The maximum recovery up until 2 years of age, though smaller than in adults, appeared at about 0.45 dimensionless speed, which is about the same speed that adults in particular naturally and at which their maximum recovery appeared. The forward inclination of the trunk and the lower limb joint angle, influenced the development of many characteristics of bipedal walking.

  2. Treadmill walking is not equivalent to overground walking for the study of walking smoothness and rhythmicity in older adults.

    PubMed

    Row Lazzarini, Brandi S; Kataras, Theodore J

    2016-05-01

    Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.

  3. Can treadmill walking be used to assess propulsion generation?

    PubMed Central

    Goldberg, Evan J.; Kautz, Steven A.; Neptune, Richard R.

    2008-01-01

    Instrumented treadmills offer significant advantages for analysis of human locomotion, including recording consecutive steady-state gait cycles, precisely controlling walking speed, and avoiding force plate targeting. However, some studies of hemiparetic walking on a treadmill have suggested that the moving treadmill belt may fundamentally alter propulsion mechanics. Any differences in propulsion mechanics during treadmill walking would be problematic since recent studies assessing propulsion have provided fundamental insight into hemiparetic walking. The purpose of this study was to test the hypothesis that there would be no difference in the generation of anterior/posterior (A/P) propulsion by performing a carefully controlled comparison of the A/P ground reaction forces (GRFs) and impulses in healthy adults during treadmill and overground walking. Gait data were collected from eight subjects walking overground and on a treadmill with speed and cadence controlled. Peak negative and positive horizontal GRFs in early and late stance, respectively, were reduced by less than 5% of body weight (p < 0.05) during treadmill walking compared to overground walking. The magnitude of the braking impulse was similarly lower (p < 0.05) during treadmill walking, but no significant difference was found between propulsion impulses. While there were some subtle differences in A/P GRFs between overground and treadmill walking, these results suggest there is no fundamental difference in propulsion mechanics. We conclude that treadmill walking can be used to investigate propulsion generation in healthy and by implication clinical populations. PMID:18436229

  4. Can treadmill walking be used to assess propulsion generation?

    PubMed

    Goldberg, Evan J; Kautz, Steven A; Neptune, Richard R

    2008-01-01

    Instrumented treadmills offer significant advantages for analysis of human locomotion, including recording consecutive steady-state gait cycles, precisely controlling walking speed, and avoiding force plate targeting. However, some studies of hemiparetic walking on a treadmill have suggested that the moving treadmill belt may fundamentally alter propulsion mechanics. Any differences in propulsion mechanics during treadmill walking would be problematic since recent studies assessing propulsion have provided fundamental insight into hemiparetic walking. The purpose of this study was to test the hypothesis that there would be no difference in the generation of anterior/posterior (A/P) propulsion by performing a carefully controlled comparison of the A/P ground reaction forces (GRFs) and impulses in healthy adults during treadmill and overground walking. Gait data were collected from eight subjects walking overground and on a treadmill with speed and cadence controlled. Peak negative and positive horizontal GRFs in early and late stance, respectively, were reduced by less than 5% of body weight (p<0.05) during treadmill walking compared to overground walking. The magnitude of the braking impulse was similarly lower (p<0.05) during treadmill walking, but no significant difference was found between propulsion impulses. While there were some subtle differences in A/P GRFs between overground and treadmill walking, these results suggest there is no fundamental difference in propulsion mechanics. We conclude that treadmill walking can be used to investigate propulsion generation in healthy and by implication clinical populations.

  5. Walking on music.

    PubMed

    Styns, Frederik; van Noorden, Leon; Moelants, Dirk; Leman, Marc

    2007-10-01

    The present study focuses on the intricate relationship between human body movement and music, in particular on how music may influence the way humans walk. In an experiment, participants were asked to synchronize their walking tempo with the tempo of musical and metronome stimuli. The walking tempo and walking speed were measured. The tempi of the stimuli varied between 50 and 190 beats per minute. The data revealed that people walk faster on music than on metronome stimuli and that walking on music can be modeled as a resonance phenomenon that is related to the perceptual resonance phenomenon as described by Van Noorden and Moelants (Van Noorden, L., & Moelants, D. (1999). Resonance in the perception of musical pulse. Journal of New Music Research, 28, 43-66).

  6. Stability of walking frames.

    PubMed

    Deathe, A B; Pardo, R D; Winter, D A; Hayes, K C; Russell-Smyth, J

    1996-02-01

    Biomechanical tools were used to assess stability for 11 patients who, following the surgical amputation of one lower limb, required the assistance of a walking frame to ambulate. The Walker Tipping Index (WTI), as derived from the forces applied to the walking frame, was developed specifically for this study to examine the relationship between stability and walking frame height during ambulation. However, the WTI may be useful as a criterion of stability to assist clinicians in their evaluation of walker use in a variety of patient populations. Walker stability was examined as subjects, wearing their prostheses, completed 30-sec walking trials in each of the normal, high, and low walking frame height conditions. Adjusting the height of the walker to one setting (3 cm) above or below normal appears to redistribute the load of walking between the upper and lower extremities without adversely affecting stability.

  7. Prediction of walking possibility in crawling children in poliomyelitis.

    PubMed

    Arora, S S; Tandon, H

    1999-01-01

    Crawling is one of the most common modes of ambulating in children with severe paralysis and deformities in poliomyelitis. Restoring upright posture and bipedal gait, although desirable, has its own limitations due to various factors. Fifty-three children below the age of 12 years (29 boys and 24 girls) crawling due to post-poliomyelitis residual paralysis were assessed for the genesis of crawling as a mode of ambulating. The patterns of crawling were classified according to Cross's classification. Paralyzed muscles and deformities in definite combinations were found responsible for each type of crawling. Trunk muscles, gluteus maximus, quadriceps, hamstrings, tibialis anterior, and triceps surae were identified as muscles crucial for walking in order of priority. At least antigravity power in these muscles was necessary for an upright posture and walking with support. Various combinations of treatment modalities were used to correct the deformities before fitting an orthosis and instituting gait training. Thirty-four children became outdoor walkers, 14 indoor walkers, and five remained nonwalkers. The most favorable patterns of crawling for restoration of upright posture were true quadruped progression (30 cases) and infant-like crawl (14 cases). Average follow-up was 17 months (range, 6 months to 5 years).

  8. Passive Dynamics Explain Quadrupedal Walking, Trotting, and Tölting

    PubMed Central

    Gan, Zhenyu; Wiestner, Thomas; Weishaupt, Michael A.; Waldern, Nina M.; David Remy, C.

    2016-01-01

    This paper presents a simplistic passive dynamic model that is able to create realistic quadrupedal walking, tölting, and trotting motions. The model is inspired by the bipedal spring loaded inverted pendulum (SLIP) model and consists of a distributed mass on four massless legs. Each of the legs is either in ground contact, retracted for swing, or is ready for touch down with a predefined angle of attack. Different gaits, that is, periodic motions differing in interlimb coordination patterns, are generated by choosing different initial model states. Contact patterns and ground reaction forces (GRFs) evolve solely from these initial conditions. By identifying appropriate system parameters in an optimization framework, the model is able to closely match experimentally recorded vertical GRFs of walking and trotting of Warmblood horses, and of tölting of Icelandic horses. In a detailed study, we investigated the sensitivity of the obtained solutions with respect to all states and parameters and quantified the improvement in fitting GRF by including an additional head and neck segment. Our work suggests that quadrupedal gaits are merely different dynamic modes of the same structural system and that we can interpret different gaits as different nonlinear elastic oscillations that propel an animal forward. PMID:27222653

  9. Effect of expertise in shooting and Taekwondo on bipedal and unipedal postural control isolated or concurrent with a reaction-time task.

    PubMed

    Negahban, Hossein; Aryan, Najmolhoda; Mazaheri, Masood; Norasteh, Ali Asghar; Sanjari, Mohammad Ali

    2013-06-01

    It was hypothesized that training in 'static balance' or 'dynamic balance' sports has differential effects on postural control and its attention demands during quiet standing. In order to test this hypothesis, two groups of female athletes practicing shooting, as a 'static balance' sport, and Taekwondo, as a 'dynamic balance' sport, and a control group of non-physically active females voluntarily participated in this study. Postural control was assessed during bipedal and unipedal stance with and without performing a Go/No-go reaction time task. Visual and/or support surface conditions were manipulated in bipedal and unipedal stances in order to modify postural difficulty. Mixed model analysis of variance was used to determine the effects of dual tasking on postural and cognitive performance. Similar pattern of results were found in bipedal and unipedal stances, with Taekwondo practitioners displaying larger sway, shooters displaying lower sway and non-athletes displaying sway characteristics intermediate to Taekwondo and shooting athletes. Larger effect was found in bipedal stance. Single to dual-task comparison of postural control showed no significant effect of mental task on sway velocity in shooters, indicating less cognitive effort invested in balance control during bipedal stance. We suggest that expertise in shooting has a more pronounced effect on decreased sway in static balance conditions. Furthermore, shooters invest less attention in postures that are more specific to their training, i.e. bipedal stance.

  10. Quantum walk public-key cryptographic system

    NASA Astrophysics Data System (ADS)

    Vlachou, C.; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.

    2015-12-01

    Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public-key is given by a quantum state generated by performing a quantum walk. We show that the protocol is secure and analyze the complexity of public key generation and encryption/decryption procedures.

  11. Numerical Simulations of Level-Ground Walking Based on Passive Walk for Planar Biped Robots with Torso by Hip Actuators

    NASA Astrophysics Data System (ADS)

    Narukawa, Terumasa; Takahashi, Masaki; Yoshida, Kazuo

    This study aims at a design technique of energy-efficient biped walking robots on level ground with simple mechanisms. To do this, we focus on the passive dynamic walkers which can walk stably down a shallow slope without actuators and controllers. On level ground, active walking should be studied because the mechanical energy is mainly lost through the swing-leg impacts with the ground. In this paper, numerical simulations show that planar biped robots with torso can walk efficiently on level ground over a wide range of speed by only using hip actuators. The hip actuators are used for a torso and swing-leg control based on passive-dynamic walking. The torso is used to generate active power replacing gravity used in the case of the passive walk. The swing-leg control is introduced to walk stably over a wide range of speed.

  12. Virtually Abelian quantum walks

    NASA Astrophysics Data System (ADS)

    Mauro D'Ariano, Giacomo; Erba, Marco; Perinotti, Paolo; Tosini, Alessandro

    2017-01-01

    We study discrete-time quantum walks on Cayley graphs of non-Abelian groups, focusing on the easiest case of virtually Abelian groups. We present a technique to reduce the quantum walk to an equivalent one on an Abelian group with coin system having larger dimension. This method allows one to extend the notion of wave-vector to the virtually Abelian case and study analytically the walk dynamics. We apply the technique in the case of two quantum walks on virtually Abelian groups with planar Cayley graphs, finding the exact solution in terms of dispersion relation.

  13. Stand and be counted: the neo-Darwinian synthesis and the ascension of bipedalism as an essential hominid synapomorphy.

    PubMed

    Gundling, Tom

    2012-01-01

    Since its inception in the early- to middle-nineteenth century, human origins studies have been informed by a variety of disciplines beyond physical anthropology and archaeology, most notably geology and biology. This study examines dramatic changes within human origins research that occurred in the mid-twentieth century largely as a consequence of the dissemination of the neo-Darwinian synthesis from biology (sensu lato) into the new" physical anthropology. This paradigm shift resulted in foregrounding evolution as a process affecting variable populations over exercises in typological classification. It led to the acknowledgement of bipedalism as the earliest hominidi adaptation, preceding other important changes in morphology (e.g., increased encephalization quotient) and behavior (e.g., stone tool manufacture and use). An important corollary of the recognition of a bipedal ape phase in our ancestry was the decoupling of the grade category "human" from the phylogenetic term "hominid".

  14. Energy expenditure during walking in amputees after disarticulation of the hip. A microprocessor-controlled swing-phase control knee versus a mechanical-controlled stance-phase control knee.

    PubMed

    Chin, T; Sawamura, S; Shiba, R; Oyabu, H; Nagakura, Y; Nakagawa, A

    2005-01-01

    We have compared the energy expenditure during walking in three patients, aged between 51 and 55 years, with unilateral disarticulation of the hip when using the mechanical-controlled stance-phase control knee (Otto Bock 3R15) and the microprocessor-controlled pneumatic swing-phase control knee (Intelligent Prosthesis, IP). All had an endoskeletal hip disarticulation prosthesis with an Otto Bock 7E7 hip and a single-axis foot. The energy expenditure was measured when walking at speeds of 30, 50, and 70 m/min. Two patients showed a decreased uptake of oxygen (energy expenditure per unit time, ml/kg/min) of between 10.3% and 39.6% when using the IP compared with the Otto Bock 3R15 at the same speeds. One did not show any significant difference in the uptake of oxygen at 30 m/min, but at 50 and 70 m/min, a decrease in uptake of between 10.5% and 11.6% was found when using the IP. The use of the IP decreased the energy expenditure of walking in these patients.

  15. A trajectory equation for walking droplets

    NASA Astrophysics Data System (ADS)

    Oza, Anand; Rosales, Rodolfo; Bush, John

    2012-11-01

    Yves Couder and coworkers have demonstrated phenomena reminiscent of quantum mechanics in a macroscopic hydrodynamic system. Specifically, they have discovered that millimetric droplets walking on a vibrating fluid bath exhibit wave-particle phenomena previously thought to be peculiar to the microscopic quantum realm, including single-particle diffraction and tunneling. Orbital quantization may be observed by placing a walking drop on a rotating fluid bath, which suggests a correspondence between the drop's quantized orbits and the Landau levels of an electron in a uniform magnetic field. We here develop an integro-differential trajectory equation for these walking droplets with a view to gaining insight into their subtle dynamics. We present an exact formula for the walking speed and compare it to experimental data. We also analyze the stability of the walking solution to infinitesimal perturbations. The trajectory equation is used to model the walking drop in a rotating fluid bath, which allows us to rationalize the observed orbital quantization. We predict the existence of self-orbiting or ``spin'' states and a mechanism reminiscent of the Zeeman effect in quantum mechanics.

  16. Walking boot assembly

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C.; Chambers, A. B.; Stjohn, R. H. (Inventor)

    1977-01-01

    A walking boot assembly particularly suited for use with a positively pressurized spacesuit is presented. A bootie adapted to be secured to the foot of a wearer, an hermetically sealed boot for receiving the bootie having a walking sole, an inner sole, and an upper portion adapted to be attached to an ankle joint of a spacesuit, are also described.

  17. Relationships between frontal-plane angular momentum and clinical balance measures during post-stroke hemiparetic walking

    PubMed Central

    Nott, C. R.; Neptune, R. R.; Kautz, S. A.

    2013-01-01

    Stroke has significant impact on dynamic balance during locomotion, with a 73% incidence rate for falls post-stroke. Current clinical assessments often rely on tasks and/or questionnaires that relate to the statistical probability of falls and provide little insight into the mechanisms that impair dynamic balance. Current quantitative measures that assess medial-lateral balance performance do not consider the angular motion of the body, which can be particularly impaired after stroke. Current control methods in bipedal robotics rely on the regulation of angular momentum (H) to maintain dynamic balance during locomotion. This study tests whether frontal-plane H is significantly correlated to clinical balance tests that could be used to provide a detailed assessment of medial-lateral balance impairments in hemiparetic gait. H was measured in post-stroke (n=48) and control (n=20) subjects. Post-stroke there were significant negative relationships between the change in frontal-plane H during paretic single-leg stance and two clinical tests: the Dynamic Gait Index (DGI) (r=-0.57, p<0.001) and the Berg Balance Scale (BBS) (r = -0.54, p<0.001). Control subjects showed timely regulation of frontal-plane H during the first half of single-leg stance, with the level of regulation depending on the initial magnitude. In contrast, the post-stroke subjects who made poorer adjustments to frontal-plane H during initial paretic leg single stance exhibited lower DGI and BBS scores (r = 0.45, p=0.003). We conclude that H is a promising balance indicator during steady-state hemiparetic walking and that paretic single-leg stance is a period with higher instability for stroke patients. PMID:23820449

  18. Lévy walks

    NASA Astrophysics Data System (ADS)

    Zaburdaev, V.; Denisov, S.; Klafter, J.

    2015-04-01

    Random walk is a fundamental concept with applications ranging from quantum physics to econometrics. Remarkably, one specific model of random walks appears to be ubiquitous across many fields as a tool to analyze transport phenomena in which the dispersal process is faster than dictated by Brownian diffusion. The Lévy-walk model combines two key features, the ability to generate anomalously fast diffusion and a finite velocity of a random walker. Recent results in optics, Hamiltonian chaos, cold atom dynamics, biophysics, and behavioral science demonstrate that this particular type of random walk provides significant insight into complex transport phenomena. This review gives a self-consistent introduction to Lévy walks, surveys their existing applications, including latest advances, and outlines further perspectives.

  19. Hip proprioceptive feedback influences the control of mediolateral stability during human walking.

    PubMed

    Roden-Reynolds, Devin C; Walker, Megan H; Wasserman, Camille R; Dean, Jesse C

    2015-10-01

    Active control of the mediolateral location of the feet is an important component of a stable bipedal walking pattern, although the roles of sensory feedback in this process are unclear. In the present experiments, we tested whether hip abductor proprioception influenced the control of mediolateral gait motion. Participants performed a series of quiet standing and treadmill walking trials. In some trials, 80-Hz vibration was applied intermittently over the right gluteus medius (GM) to evoke artificial proprioceptive feedback. During walking, the GM was vibrated during either right leg stance (to elicit a perception that the pelvis was closer mediolaterally to the stance foot) or swing (to elicit a perception that the swing leg was more adducted). Vibration during quiet standing evoked leftward sway in most participants (13 of 16), as expected from its predicted perceptual effects. Across the 13 participants sensitive to vibration, stance phase vibration caused the contralateral leg to be placed significantly closer to the midline (by ∼2 mm) at the end of the ongoing step. In contrast, swing phase vibration caused the vibrated leg to be placed significantly farther mediolaterally from the midline (by ∼2 mm), whereas the pelvis was held closer to the stance foot (by ∼1 mm). The estimated mediolateral margin of stability was thus decreased by stance phase vibration but increased by swing phase vibration. Although the observed effects of vibration were small, they were consistent with humans monitoring hip proprioceptive feedback while walking to maintain stable mediolateral gait motion.

  20. Hip proprioceptive feedback influences the control of mediolateral stability during human walking

    PubMed Central

    Roden-Reynolds, Devin C.; Walker, Megan H.; Wasserman, Camille R.

    2015-01-01

    Active control of the mediolateral location of the feet is an important component of a stable bipedal walking pattern, although the roles of sensory feedback in this process are unclear. In the present experiments, we tested whether hip abductor proprioception influenced the control of mediolateral gait motion. Participants performed a series of quiet standing and treadmill walking trials. In some trials, 80-Hz vibration was applied intermittently over the right gluteus medius (GM) to evoke artificial proprioceptive feedback. During walking, the GM was vibrated during either right leg stance (to elicit a perception that the pelvis was closer mediolaterally to the stance foot) or swing (to elicit a perception that the swing leg was more adducted). Vibration during quiet standing evoked leftward sway in most participants (13 of 16), as expected from its predicted perceptual effects. Across the 13 participants sensitive to vibration, stance phase vibration caused the contralateral leg to be placed significantly closer to the midline (by ∼2 mm) at the end of the ongoing step. In contrast, swing phase vibration caused the vibrated leg to be placed significantly farther mediolaterally from the midline (by ∼2 mm), whereas the pelvis was held closer to the stance foot (by ∼1 mm). The estimated mediolateral margin of stability was thus decreased by stance phase vibration but increased by swing phase vibration. Although the observed effects of vibration were small, they were consistent with humans monitoring hip proprioceptive feedback while walking to maintain stable mediolateral gait motion. PMID:26289467

  1. Random walks in the history of life

    PubMed Central

    Cornette, James L.; Lieberman, Bruce S.

    2004-01-01

    The simplest null hypothesis for evolutionary time series is that the observed data follow a random walk. We examined whether aspects of Sepkoski's compilation of marine generic diversity depart from a random walk by using statistical tests from econometrics. Throughout most of the Phanerozoic, the random-walk null hypothesis is not rejected for marine diversity, accumulated origination or accumulated extinction, suggesting that either these variables were correlated with environmental variables that follow a random walk or so many mechanisms were affecting these variables, in different ways, that the resultant trends appear random. The only deviation from this pattern involves rejection of the null hypothesis for roughly the last 75 million years for the diversity and accumulated origination time series. PMID:14684835

  2. Walking with coffee: why does it spill?

    PubMed

    Mayer, H C; Krechetnikov, R

    2012-04-01

    In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup. These observations are analyzed from the dynamical systems and fluid mechanics viewpoints as well as with the help of a model developed here. Particularities of the common cup sizes, the coffee properties, and the biomechanics of walking proved to be responsible for the spilling phenomenon. The studied problem represents an example of the interplay between the complex motion of a cup, due to the biomechanics of a walking individual, and the low-viscosity-liquid dynamics in it.

  3. Walking with coffee: Why does it spill?

    NASA Astrophysics Data System (ADS)

    Mayer, H. C.; Krechetnikov, R.

    2012-04-01

    In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup. These observations are analyzed from the dynamical systems and fluid mechanics viewpoints as well as with the help of a model developed here. Particularities of the common cup sizes, the coffee properties, and the biomechanics of walking proved to be responsible for the spilling phenomenon. The studied problem represents an example of the interplay between the complex motion of a cup, due to the biomechanics of a walking individual, and the low-viscosity-liquid dynamics in it.

  4. Strongly correlated quantum walks in optical lattices.

    PubMed

    Preiss, Philipp M; Ma, Ruichao; Tai, M Eric; Lukin, Alexander; Rispoli, Matthew; Zupancic, Philip; Lahini, Yoav; Islam, Rajibul; Greiner, Markus

    2015-03-13

    Full control over the dynamics of interacting, indistinguishable quantum particles is an important prerequisite for the experimental study of strongly correlated quantum matter and the implementation of high-fidelity quantum information processing. We demonstrate such control over the quantum walk-the quantum mechanical analog of the classical random walk-in the regime where dynamics are dominated by interparticle interactions. Using interacting bosonic atoms in an optical lattice, we directly observed fundamental effects such as the emergence of correlations in two-particle quantum walks, as well as strongly correlated Bloch oscillations in tilted optical lattices. Our approach can be scaled to larger systems, greatly extending the class of problems accessible via quantum walks. Copyright © 2015, American Association for the Advancement of Science.

  5. Epidemic spreading driven by biased random walks

    NASA Astrophysics Data System (ADS)

    Pu, Cunlai; Li, Siyuan; Yang, Jian

    2015-08-01

    Random walk is one of the basic mechanisms of many network-related applications. In this paper, we study the dynamics of epidemic spreading driven by biased random walks in complex networks. In our epidemic model, infected nodes send out infection packets by biased random walks to their neighbor nodes, and this causes the infection of susceptible nodes that receive the packets. Infected nodes recover from the infection at a constant rate λ, and will not be infected again after recovery. We obtain the largest instantaneous number of infected nodes and the largest number of ever-infected nodes respectively, by tuning the parameter α of the biased random walks. Simulation results on model and real-world networks show that spread of the epidemic becomes intense and widespread with increase of either delivery capacity of infected nodes, average node degree, or homogeneity of node degree distribution.

  6. Biomechanical modeling and sensitivity analysis of bipedal running ability. II. Extinct taxa.

    PubMed

    Hutchinson, John R

    2004-10-01

    Using an inverse dynamics biomechanical analysis that was previously validated for extant bipeds, I calculated the minimum amount of actively contracting hindlimb extensor muscle that would have been needed for rapid bipedal running in several extinct dinosaur taxa. I analyzed models of nine theropod dinosaurs (including birds) covering over five orders of magnitude in size. My results uphold previous findings that large theropods such as Tyrannosaurus could not run very quickly, whereas smaller theropods (including some extinct birds) were adept runners. Furthermore, my results strengthen the contention that many nonavian theropods, especially larger individuals, used fairly upright limb orientations, which would have reduced required muscular force, and hence muscle mass. Additional sensitivity analysis of muscle fascicle lengths, moment arms, and limb orientation supports these conclusions and points out directions for future research on the musculoskeletal limits on running ability. Although ankle extensor muscle support is shown to have been important for all taxa, the ability of hip extensor muscles to support the body appears to be a crucial limit for running capacity in larger taxa. I discuss what speeds were possible for different theropod dinosaurs, and how running ability evolved in an inverse relationship to body size in archosaurs.

  7. Relationships between Muscle Contributions to Walking Subtasks and Functional Walking Status in Persons with Post-Stroke Hemiparesis

    PubMed Central

    Hall, A.L.; Peterson, C.L.; Kautz, S.A.; Neptune, R.R.

    2011-01-01

    Background Persons with post-stroke hemiparesis usually walk slowly and asymmetrically. Stroke severity and functional walking status are commonly predicted by post-stroke walking speed. The mechanisms that limit walking speed, and by extension functional walking status, need to be understood to improve post-stroke rehabilitation methods. Methods Three-dimensional forward dynamics walking simulations of hemiparetic subjects (and speed-matched controls) with different levels of functional walking status were developed to investigate the relationships between muscle contributions to walking subtasks and functional walking status. Muscle contributions to forward propulsion, swing initiation and power generation were analyzed during the pre-swing phase of the gait cycle and compared between groups. Findings Contributions from the paretic leg muscles (i.e., soleus, gastrocnemius and gluteus medius) to forward propulsion increased with improved functional walking status, with the non-paretic leg muscles (i.e., rectus femoris and vastii) compensating for reduced paretic leg propulsion in the limited community walker. Contributions to swing initiation from both paretic (i.e., gastrocnemius, iliacus and psoas) and non-paretic leg muscles (i.e., hamstrings) also increased as functional walking status improved. Power generation was also an important indicator of functional walking status, with reduced paretic leg power generation limiting the paretic leg contribution to forward propulsion and leg swing initiation. Interpretation These results suggest that deficits in muscle contributions to the walking subtasks of forward propulsion, swing initiation and power generation are directly related to functional walking status and that improving output in these muscle groups may be an effective rehabilitation strategy for improving post-stroke hemiparetic walking. PMID:21251738

  8. Normal and hemiparetic walking

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Friedrich; König, Eberhard

    2013-01-01

    The idea of a model-based control of rehabilitation for hemiparetic patients requires efficient models of human walking, healthy walking as well as hemiparetic walking. Such models are presented in this paper. They include 42 degrees of freedom and allow especially the evaluation of kinetic magnitudes with the goal to evaluate measures for the hardness of hemiparesis. As far as feasible, the simulations have been compared successfully with measurements, thus improving the confidence level for an application in clinical practice. The paper is mainly based on the dissertation [19].

  9. Quantum Walk Schemes for Universal Quantum Computation

    NASA Astrophysics Data System (ADS)

    Underwood, Michael S.

    Random walks are a powerful tool for the efficient implementation of algorithms in classical computation. Their quantum-mechanical analogues, called quantum walks, hold similar promise. Quantum walks provide a model of quantum computation that has recently been shown to be equivalent in power to the standard circuit model. As in the classical case, quantum walks take place on graphs and can undergo discrete or continuous evolution, though quantum evolution is unitary and therefore deterministic until a measurement is made. This thesis considers the usefulness of continuous-time quantum walks to quantum computation from the perspectives of both their fundamental power under various formulations, and their applicability in practical experiments. In one extant scheme, logical gates are effected by scattering processes. The results of an exhaustive search for single-qubit operations in this model are presented. It is shown that the number of distinct operations increases exponentially with the number of vertices in the scattering graph. A catalogue of all graphs on up to nine vertices that implement single-qubit unitaries at a specific set of momenta is included in an appendix. I develop a novel scheme for universal quantum computation called the discontinuous quantum walk, in which a continuous-time quantum walker takes discrete steps of evolution via perfect quantum state transfer through small 'widget' graphs. The discontinuous quantum-walk scheme requires an exponentially sized graph, as do prior discrete and continuous schemes. To eliminate the inefficient vertex resource requirement, a computation scheme based on multiple discontinuous walkers is presented. In this model, n interacting walkers inhabiting a graph with 2n vertices can implement an arbitrary quantum computation on an input of length n, an exponential savings over previous universal quantum walk schemes. This is the first quantum walk scheme that allows for the application of quantum error correction

  10. Walking with coffee: when and why coffee spills

    NASA Astrophysics Data System (ADS)

    Mayer, Hans C.; Krechetnikov, Rouslan

    2011-11-01

    In our busy lives, almost all of us have to walk with a cup of coffee. Needless to say, under certain conditions we spill that precious liquid. This is a common example of the interplay between the mechanics of the complex motion of a walking individual and the fluid dynamics of a low viscosity liquid contained in a cup. We report on the results of an experimental investigation undertaken to explore the particular conditions under which coffee spills. Frame-by-frame analysis of recorded movies helps to elucidate the trajectory of the cup for various walking speeds and initial liquid levels. These kinematics, including both regular and irregular motions, are connected to instances during walking that result in spilled liquid. The coupling between mechanical aspects of walking and the fluid motion are analyzed based on which we determine a basic operational space with which one can confidently walk with cup in hand.

  11. Crossover from random walk to self-avoiding walk

    NASA Astrophysics Data System (ADS)

    Rieger, Jens

    1988-11-01

    A one-dimensional n-step random walk on openZ1 which must not visit a vertex more than k times is studied via Monte Carlo methods. The dependences of the mean-square end-to-end distance of the walk and of the fraction of trapped walks on λ=(k-1)/n will be given for the range from λ=0 (self-avoiding walk) to λ=1 (unrestricted random walk). From the results it is conjectured that in the limit n-->∞ the walk obeys simple random walk statistics with respect to its static properties for all λ>0.

  12. Integrated photonic quantum walks

    NASA Astrophysics Data System (ADS)

    Gräfe, Markus; Heilmann, René; Lebugle, Maxime; Guzman-Silva, Diego; Perez-Leija, Armando; Szameit, Alexander

    2016-10-01

    Over the last 20 years quantum walks (QWs) have gained increasing interest in the field of quantum information science and processing. In contrast to classical walkers, quantum objects exhibit intrinsic properties like non-locality and non-classical many-particle correlations, which renders QWs a versatile tool for quantum simulation and computation as well as for a deeper understanding of genuine quantum mechanics. Since they are highly controllable and hardly interact with their environment, photons seem to be ideally suited quantum walkers. In order to study and exploit photonic QWs, lattice structures that allow low loss coherent evolution of quantum states are demanded. Such requirements are perfectly met by integrated optical waveguide devices that additionally allow a substantial miniaturization of experimental settings. Moreover, by utilizing the femtosecond direct laser writing technique three-dimensional waveguide structures are capable of analyzing QWs also on higher dimensional geometries. In this context, advances and findings of photonic QWs are discussed in this review. Various concepts and experimental results are presented covering, such as different quantum transport regimes, the Boson sampling problem, and the discrete fractional quantum Fourier transform.

  13. Analysis of the multi-segmental postural movement strategies utilized in bipedal, tandem and one-leg stance as quantified by a principal component decomposition of marker coordinates.

    PubMed

    Federolf, Peter; Roos, Lilian; Nigg, Benno M

    2013-10-18

    Postural control research describes ankle-, hip-, or multi-joint strategies as mechanisms to control upright posture. The objectives of this study were, first, development of an analysis technique facilitating a direct comparison of the structure of such multi-segment postural movement patterns between subjects; second, comparison of the complexity of postural movements between three stances of different difficulty levels; and third, investigation of between-subject differences in the structure of postural movements and of factors that may contribute to these differences. Twenty-nine subjects completed 100-s trials in bipedal (BP), tandem (TA) and one-leg stance (OL). Their postural movements were recorded using 28 reflective markers distributed over all body segments. These marker coordinates were interpreted as 84-dimensional posture vectors, normalized, concatenated from all subjects, and submitted to a principal component analysis (PCA) to extract principal movement components (PMs). The PMs were characterized by determining their relative contribution to the subject's entire postural movements and the smoothness of their time series. Four, eight, and nine PM were needed to represent 90% of the total variance in BP, TA, and OL, respectively, suggesting that increased task difficulty is associated with increased complexity of the movement structure. Different subjects utilized different combinations of PMs to control their posture. In several PMs, the relative contribution of a PM to a subject's overall postural movements correlated with the smoothness of the PM's time series, suggesting that utilization of specific postural PMs may depend on the subject's ability to control the PM's temporal evolution.

  14. Walking On Air

    NASA Image and Video Library

    This video features a series of time lapse sequences photographed by the Expedition 30 crew aboard the International Space Station. Set to the song "€œWalking in the Air,"€ by Howard Blake, the v...

  15. A finite element study on the mechanical response of the head-neck interface of hip implants under realistic forces and moments of daily activities: Part 1, level walking.

    PubMed

    Farhoudi, Hamidreza; Fallahnezhad, Khosro; Oskouei, Reza H; Taylor, Mark

    2017-08-12

    This paper investigates the mechanical response of a modular head-neck interface of hip joint implants under realistic loads of level walking. The realistic loads of the walking activity consist of three dimensional gait forces and the associated frictional moments. These forces and moments were extracted for a 32mm metal-on-metal bearing couple. A previously reported geometry of a modular CoCr/CoCr head-neck interface with a proximal contact was used for this investigation. An explicit finite element analysis was performed to investigate the interface mechanical responses. To study the level of contribution and also the effect of superposition of the load components, three different scenarios of loading were studied: gait forces only, frictional moments only, and combined gait forces and frictional moments. Stress field, micro-motions, shear stresses and fretting work at the contacting nodes of the interface were analysed. Gait forces only were found to significantly influence the mechanical environment of the head-neck interface by temporarily extending the contacting area (8.43% of initially non-contacting surface nodes temporarily came into contact), and therefore changing the stress field and resultant micro-motions during the gait cycle. The frictional moments only did not cause considerable changes in the mechanical response of the interface (only 0.27% of the non-contacting surface nodes temporarily came into contact). However, when superposed with the gait forces, the mechanical response of the interface, particularly micro-motions and fretting work, changed compared to the forces only case. The normal contact stresses and micro-motions obtained from this realistic load-controlled study were typically in the range of 0-275MPa and 0-38µm, respectively. These ranges were found comparable to previous experimental displacement-controlled pin/cylinder-on-disk fretting corrosion studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Powered Exoskeletons for Walking Assistance in Persons with Central Nervous System Injuries: A Narrative Review.

    PubMed

    Esquenazi, Alberto; Talaty, Mukul; Jayaraman, Arun

    2017-01-01

    Individuals with central nervous system injuries are a large and apparently rapidly expanding population-as suggested by 2013 statistics from the American Heart Association. Increasing survival rates and lifespans emphasize the need to improve the quality of life for this population. In persons with central nervous system injuries, mobility limitations are among the most important factors contributing to reduced life satisfaction. Decreased mobility and subsequently reduced overall activity levels also contribute to lower levels of physical health. Braces to assist walking are options for greater-functioning individuals but still limit overall mobility as the result of increased energy expenditure and difficulty of use. For individuals with greater levels of mobility impairment, wheelchairs remain the preferred mobility aid yet still fall considerably short compared with upright bipedal walking. Furthermore, the promise of functional electrical stimulation as a means to achieve walking has yet to materialize. None of these options allow individuals to achieve walking at speeds or levels comparable with those seen in individuals with unimpaired gait. Medical exoskeletons hold much promise to fulfill this unmet need and have advanced as a viable option in both therapeutic and personal mobility state, particularly during the past decade. The present review highlights the major developments in this technology, with a focus on exoskeletons for lower limb that may encompass the spine and that aim to allow independent upright walking for those who otherwise do not have this option. Specifically reviewed are powered exoskeletons that are either commercially available or have the potential to restore upright walking function. This paper includes a basic description of how each exoskeleton device works, a summation of key features, their known limitations, and a discussion of current and future clinical applicability. Copyright © 2017 American Academy of Physical Medicine

  17. Quantum walk and potential application

    NASA Astrophysics Data System (ADS)

    Wang, J. B.; Douglas, B. L.

    2010-06-01

    Quantum walk represents a generalised version of the well-known classical random walk. Regardless of their apparent connection, the dynamics of quantum walk is often non-intuitive and far deviate from its classical counterpart. However, despite such potentially superior efficiency in quantum walks, it has yet to be applied to problems of practical importance. In this paper, we will give a brief introduction to quantum walks and discuss potential applications.

  18. Homeothermy and primate bipedalism: is water shortage or solar radiation the main threat to baboon (Papio hamadryas) homeothermy?

    PubMed

    Mitchell, Duncan; Fuller, Andrea; Maloney, Shane K

    2009-05-01

    Other than the hominin lineage, baboons are the diurnally active primates that have colonized the arid plains of Africa most successfully. While the hominin lineage adopted bipedalism before colonizing the open, dry plains, baboons retained a quadrupedal mode of locomotion. Because bipedalism has been considered to reduce the thermoregulatory stress of inhabiting open dry plains, we investigated how baboons cope with thermal loads and water restriction. Using implanted data loggers, we measured abdominal temperature every 5 min in six unrestrained baboons while they were exposed to simulated desert conditions (15 degrees C at night rising to 35 degrees C during the day, with and without extra radiant heating), or an ambient temperature of 22 degrees C. At 22 degrees C, core temperature averaged 37.9 degrees C and cycled nychthemerally by 1.7 degrees C. Mean, minimum, and maximum daily core temperatures in euhydrated baboons in the simulated desert environments did not differ from the temperatures displayed in the 22 degrees C environment, even when radiant heating was applied. At 22 degrees C, restricting water intake did not affect core temperature. During the desert simulations, maximum core temperature increased significantly on each day of water deprivation, with the highest temperatures (>40 degrees C) on the third day in the simulation that included radiant heat. When drinking water heated to 38 degrees C was returned, core temperature decreased rapidly to a level lower than normal for that time of day. We conclude that baboons with access to water can maintain homeothermy in the face of high air temperatures and radiant heat loads, but that a lack of access to drinking water poses a major threat to baboon homeothermy. We speculate that any competitive thermoregulatory advantage of bipedalism in early hominins was related to coping with water shortage in hot environments, and that their freed hands might have enabled them to transport enough water to avoid

  19. Exploring Factors Regarding Transit-related Walking and Walking Duration.

    PubMed

    Yu, Chia-Yuan; Lin, Hsien-Chang

    2016-11-01

    Transit-related walking provides a potential opportunity to promote general walking behavior, yet few studies have examined this issue. Since people's decisions tend to vary as they walk between home and transit and between transit and destination, this study separated trips made in each direction. This study identified the associations between sociodemographics and the 2-step process of transit-related walking: 1) whether transit users walked for home-transit trip or transitdestination trip, and 2) the walking duration for home-transit trip or transit-destination trip among those who walked. This cross-sectional study used the 2009 National Household Travel Survey and used the Heckman 2-step selection model by including 4042 respondents (10,105 trips) who walked all portions for home-transit trip and 3756 (8075 trips) for transitdestination trip. The mean walking duration for home-transit trips (7.60 minutes) was shorter than transit-destination trips (7.87 minutes). Hispanics were more likely to walk for both directions and had higher walking durations than did whites. Respondents living in low-income households were more likely to walk for home-transit trip, but not for transit-destination trips. This study illustrated several implications regarding to transit-related walking, such as creating short home-transit distances and targeting whites in promoting transit-related walking.

  20. Developing Point-of-Decision Prompts to Encourage Airport Walking: The Walk to Fly Study

    PubMed Central

    Frederick, Ginny M.; Paul, Prabasaj; Watson, Kathleen Bachtel; Dorn, Joan M.; Fulton, Janet

    2017-01-01

    Background Point-of-decision prompts may be appropriate to promote walking, instead of using a mechanized mode of transport, such as a train, in airports. To our knowledge, no current studies describe the development of messages for prompts in this setting. Methods In-person interviews were conducted with 150 randomly selected airport travelers who rode the train to their departure gate. Travelers reported various reasons for riding the train to their gate. They were asked about messages that would encourage them to walk. Exploratory factor analysis was conducted for reasons for riding the train. Confirmatory factor analysis was conducted for messages to encourage walking to the departure gate. Results Travelers reported not knowing walking was an option (23.8%), seeing others riding the train (14.4%), and being afraid of getting lost (9.2%) as reasons for riding the train. Many indicated that directional signs and prompts promoting walking as exercise would encourage them to walk instead of riding the train. Conclusions Some reasons for riding the train in an airport may be modifiable by installing point-of-decision prompts. Providing directional signs to travelers may prompt them to walk to their gate instead of riding the train. Similar prompts may also be considered in other community settings. PMID:26445371

  1. Developing Point-of-Decision Prompts to Encourage Airport Walking: The Walk to Fly Study.

    PubMed

    Frederick, Ginny M; Paul, Prabasaj; Bachtel Watson, Kathleen; Dorn, Joan M; Fulton, Janet

    2016-04-01

    Point-of-decision prompts may be appropriate to promote walking, instead of using a mechanized mode of transport, such as a train, in airports. To our knowledge, no current studies describe the development of messages for prompts in this setting. In-person interviews were conducted with 150 randomly selected airport travelers who rode the train to their departure gate. Travelers reported various reasons for riding the train to their gate. They were asked about messages that would encourage them to walk. Exploratory factor analysis was conducted for reasons for riding the train. Confirmatory factor analysis was conducted for messages to encourage walking to the departure gate. Travelers reported not knowing walking was an option (23.8%), seeing others riding the train (14.4%), and being afraid of getting lost (9.2%) as reasons for riding the train. Many indicated that directional signs and prompts promoting walking as exercise would encourage them to walk instead of riding the train. Some reasons for riding the train in an airport may be modifiable by installing point-of-decision prompts. Providing directional signs to travelers may prompt them to walk to their gate instead of riding the train. Similar prompts may also be considered in other community settings.

  2. Zero Range Process and Multi-Dimensional Random Walks

    NASA Astrophysics Data System (ADS)

    Bogoliubov, Nicolay M.; Malyshev, Cyril

    2017-07-01

    The special limit of the totally asymmetric zero range process of the low-dimensional non-equilibrium statistical mechanics described by the non-Hermitian Hamiltonian is considered. The calculation of the conditional probabilities of the model are based on the algebraic Bethe ansatz approach. We demonstrate that the conditional probabilities may be considered as the generating functions of the random multi-dimensional lattice walks bounded by a hyperplane. This type of walks we call the walks over the multi-dimensional simplicial lattices. The answers for the conditional probability and for the number of random walks in the multi-dimensional simplicial lattice are expressed through the symmetric functions.

  3. D.U.C.K. Walking.

    ERIC Educational Resources Information Center

    Steller, Jenifer J.

    This manual presents a schoolwide walking program that includes aerobic fitness information, curriculum integration, and walking tours. "Discover and Understand Carolina Kids by Walking" is D.U.C.K. Walking. An aerobic walking activity, D.U.C.K. Walking has two major goals: (1) to promote regular walking as a way to exercise at any age;…

  4. Generalized teleportation by quantum walks

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Shang, Yun; Xue, Peng

    2017-09-01

    We develop a generalized teleportation scheme based on quantum walks with two coins. For an unknown qubit state, we use two-step quantum walks on the line and quantum walks on the cycle with four vertices for teleportation. For any d-dimensional states, quantum walks on complete graphs and quantum walks on d-regular graphs can be used for implementing teleportation. Compared with existing d-dimensional states teleportation, prior entangled state is not required and the necessary maximal entanglement resource is generated by the first step of quantum walk. Moreover, two projective measurements with d elements are needed by quantum walks on the complete graph, rather than one joint measurement with d^2 basis states. Quantum walks have many applications in quantum computation and quantum simulations. This is the first scheme of realizing communicating protocol with quantum walks, thus opening wider applications.

  5. Insect walking and robotics.

    PubMed

    Delcomyn, Fred

    2004-01-01

    With the advent of significant collaborations between researchers who study insect walking and robotics engineers interested in constructing adaptive legged robots, insect walking is once again poised to make a more significant scientific contribution than the numbers of participants in the field might suggest. This review outlines current knowledge of the physiological basis of insect walking with an emphasis on recent new developments in biomechanics and genetic dissection of behavior, and the impact this knowledge is having on robotics. Engineers have begun to team with neurobiologists to build walking robots whose physical design and functional control are based on insect biology. Such an approach may have benefits for engineering, by leading to the construction of better-performing robots, and for biology, by allowing real-time and real-world tests of critical hypotheses about how locomotor control is effected. It is argued that in order for the new field of biorobotics to have significant influence it must adopt criteria for performance and an experimental approach to the development of walking robots.

  6. Walks on SPR neighborhoods.

    PubMed

    Caceres, Alan Joseph J; Castillo, Juan; Lee, Jinnie; St John, Katherine

    2013-01-01

    A nearest-neighbor-interchange (NNI)-walk is a sequence of unrooted phylogenetic trees, T1, T2, . . . , T(k) where each consecutive pair of trees differs by a single NNI move. We give tight bounds on the length of the shortest NNI-walks that visit all trees in a subtree-prune-and-regraft (SPR) neighborhood of a given tree. For any unrooted, binary tree, T, on n leaves, the shortest walk takes Θ(n²) additional steps more than the number of trees in the SPR neighborhood. This answers Bryant’s Second Combinatorial Challenge from the Phylogenetics Challenges List, the Isaac Newton Institute, 2011, and the Penny Ante Problem List, 2009.

  7. Bouncing and walking droplets

    NASA Astrophysics Data System (ADS)

    Molacek, Jan; Bush, John

    2012-11-01

    Motivated by the hydrodynamic quantum analogue system of Yves Couder, we examine the dynamics of silicone oil drops bouncing on a vertically vibrating liquid bath. We report regime diagrams indicating the dependence of the vertical drop motion on the system parameters. A logarithmic spring model for the interface is developed, and provides new rationale for the regime diagrams. We further examine the spatio-temporal evolution of the standing waves created on the bath surface by repeated drop impacts. Measurement of the tangential coefficient of restitution of drops bouncing on a quiescent bath enables us to accurately determine all the major forces acting on the drop during flight and impact. By combining the horizontal and vertical dynamics, we thus develop a model for the walking drops that enables us to rationalize both the extent of the walking regime and the walking speeds. The model predictions compare favorably with experimental data in the parameter range explored.

  8. Staggered quantum walks with Hamiltonians

    NASA Astrophysics Data System (ADS)

    Portugal, R.; de Oliveira, M. C.; Moqadam, J. K.

    2017-01-01

    Quantum walks are recognizably useful for the development of new quantum algorithms, as well as for the investigation of several physical phenomena in quantum systems. Actual implementations of quantum walks face technological difficulties similar to the ones for quantum computers, though. Therefore, there is a strong motivation to develop new quantum-walk models which might be easier to implement. In this work we present an extension of the staggered quantum walk model that is fitted for physical implementations in terms of time-independent Hamiltonians. We demonstrate that this class of quantum walk includes the entire class of staggered quantum walk model, Szegedy's model, and an important subset of the coined model.

  9. Postural bipedance in paraplegics under Neuromuscular Electrical Stimulation: Is it possible to improve it based on Sagittal Spinal Alignment?

    PubMed Central

    Medeiros, Rodrigo C.; Jaccard, Alexandre P. B.; Cliquet, Alberto

    2011-01-01

    Study design Experimental trial based on the analytical study of the radiographic standards of the sagittal spinal alignment in paraplegics in upright position under surface Neuromuscular Electrical Stimulation (NMES). Objectives To evaluate changes in radiographic standards of the sagittal spinal alignment of paraplegics under three different models of NMES used to optimize the global bipedal posture. Setting The University Hospital Ambulatory (UNICAMP), Campinas, SP, Brazil Methods Ten paraplegic patients were selected. Each patient underwent three different models of NMES. The influence that each NMES models exerted over the sagittal balance of the spine was evaluated by lateral panoramic x-rays. Wilcoxon’s Test was used to compare the modifications observed in each NMES model in the group studied. Results Using the femoral quadriceps muscles’ NMES as the starting point, the inclusion of the gluteus maximus’ NMES generated an increase of the lumbar lordosis and an decrease of the spinal tilt angle. These alterations resulted in partial improvement of the anterior sagittal imbalance. NMES of the paralyzed paravertebral lumbar muscles resulted in a more expressive increase on the lumbar lordosis with no important change on the spinal tilt. On the latter model, however, an improvement of 20% was observed in the global sagittal imbalance due to a posterior translation of the spine as pointed out by the decrease in the C7-HA horizontal distance. Conclusions The proposed NMES models were able to partially amend the anterior sagittal imbalance of the paraplegic patients in bipedal posture. PMID:22333891

  10. On extracting design principles from biology: II. Case study-the effect of knee direction on bipedal robot running efficiency.

    PubMed

    Haberland, M; Kim, S

    2015-02-02

    Comparing the leg of an ostrich to that of a human suggests an important question to legged robot designers: should a robot's leg joint bend in the direction of running ('forwards') or opposite ('backwards')? Biological studies cannot answer this question for engineers due to significant differences between the biological and engineering domains. Instead, we investigated the inherent effect of joint bending direction on bipedal robot running efficiency by comparing energetically optimal gaits of a wide variety of robot designs sampled at random from a design space. We found that the great majority of robot designs have several locally optimal gaits with the knee bending backwards that are more efficient than the most efficient gait with the knee bending forwards. The most efficient backwards gaits do not exhibit lower touchdown losses than the most efficient forward gaits; rather, the improved efficiency of backwards gaits stems from lower torque and reduced motion at the hip. The reduced hip use of backwards gaits is enabled by the ability of the backwards knee, acting alone, to (1) propel the robot upwards and forwards simultaneously and (2) lift and protract the foot simultaneously. In the absence of other information, designers interested in building efficient bipedal robots with two-segment legs driven by electric motors should design the knee to bend backwards rather than forwards. Compared to common practices for choosing robot knee direction, application of this principle would have a strong tendency to improve robot efficiency and save design resources.

  11. 10 CFR 431.302 - Definitions concerning walk-in coolers and walk-in freezers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Definitions concerning walk-in coolers and walk-in... FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Walk-in Coolers and Walk-in Freezers § 431.302 Definitions concerning walk-in coolers and walk-in freezers. Walk-in cooler and walk-in freezer mean...

  12. Attributes of environments supporting walking.

    PubMed

    Moudon, Anne Vernez; Lee, Chanam; Cheadle, Allen D; Garvin, Cheza; Rd, Donna B Johnson; Schmid, Thomas L; Weathers, Robert D

    2007-01-01

    This study established a framework to audit environments supporting walking in neighborhoods. Cross-sectional analysis using a telephone survey and 200 objective environmental variables. SETTING. Urbanized King County, WA. SUBJECTS. 608 randomly sampled adults. Measures. Walking measures constructed from survey questions; objective environmental measures taken from parcel-level databases in Geographic Information Systems. Multinomial models estimated the odds of people engaging in moderate walking (<149 min/wk) and in walking sufficiently to meet recommendations for health (150+ min/ wk), relative to not walking" and in walking sufficiently, relative to walking moderately. A base model consisted of survey variables, and final models incorporated both survey and environmental variables. RESULTS. Survey variables strongly associated with walking sufficiently to enhance health included household income, not having difficulty walking, using transit, perceiving social support for walking walking outside of the neighborhood, and having a dog (p < .01). The models isolated 14 environmental variables associated with walking sufficiently (pseudo R2 up to 0. 46). Measures of distance to neighborhood destinations dominated the results: shorter distances to grocery stores/markets, restaurants, and retail stores, but longer distances to offices or mixed-use buildings (p < .01 or .05). The density of the respondent's parcel was also strongly associated with walking sufficiently (p < .01). Conclusions. The study offered valid environmental measures of neighborhood walkability.

  13. Shared muscle synergies in human walking and cycling.

    PubMed

    Barroso, Filipe O; Torricelli, Diego; Moreno, Juan C; Taylor, Julian; Gomez-Soriano, Julio; Bravo-Esteban, Elisabeth; Piazza, Stefano; Santos, Cristina; Pons, José L

    2014-10-15

    The motor system may rely on a modular organization (muscle synergies activated in time) to execute different tasks. We investigated the common control features of walking and cycling in healthy humans from the perspective of muscle synergies. Three hypotheses were tested: 1) muscle synergies extracted from walking trials are similar to those extracted during cycling; 2) muscle synergies extracted from one of these motor tasks can be used to mathematically reconstruct the electromyographic (EMG) patterns of the other task; 3) muscle synergies of cycling can result from merging synergies of walking. A secondary objective was to identify the speed (and cadence) at which higher similarities emerged. EMG activity from eight muscles of the dominant leg was recorded in eight healthy subjects during walking and cycling at four matched cadences. A factorization technique [nonnegative matrix factorization (NNMF)] was applied to extract individual muscle synergy vectors and the respective activation coefficients behind the global muscular activity of each condition. Results corroborated hypotheses 2 and 3, showing that 1) four synergies from walking and cycling can successfully explain most of the EMG variability of cycling and walking, respectively, and 2) two of four synergies from walking appear to merge together to reconstruct one individual synergy of cycling, with best reconstruction values found for higher speeds. Direct comparison of the muscle synergy vectors of walking and the muscle synergy vectors of cycling (hypothesis 1) produced moderated values of similarity. This study provides supporting evidence for the hypothesis that cycling and walking share common neuromuscular mechanisms.

  14. Mall Walking Program Environments, Features, and Participants: A Scoping Review.

    PubMed

    Farren, Laura; Belza, Basia; Allen, Peg; Brolliar, Sarah; Brown, David R; Cormier, Marc L; Janicek, Sarah; Jones, Dina L; King, Diane K; Marquez, David X; Rosenberg, Dori E

    2015-08-13

    Walking is a preferred and recommended physical activity for middle-aged and older adults, but many barriers exist, including concerns about safety (ie, personal security), falling, and inclement weather. Mall walking programs may overcome these barriers. The purpose of this study was to summarize the evidence on the health-related value of mall walking and mall walking programs. We conducted a scoping review of the literature to determine the features, environments, and benefits of mall walking programs using the RE-AIM framework (reach, effectiveness, adoption, implementation, and maintenance). The inclusion criteria were articles that involved adults aged 45 years or older who walked in indoor or outdoor shopping malls. Exclusion criteria were articles that used malls as laboratory settings or focused on the mechanics of walking. We included published research studies, dissertations, theses, conference abstracts, syntheses, nonresearch articles, theoretical papers, editorials, reports, policy briefs, standards and guidelines, and nonresearch conference abstracts and proposals. Websites and articles written in a language other than English were excluded. We located 254 articles on mall walking; 32 articles met our inclusion criteria. We found that malls provided safe, accessible, and affordable exercise environments for middle-aged and older adults. Programmatic features such as program leaders, blood pressure checks, and warm-up exercises facilitated participation. Individual benefits of mall walking programs included improvements in physical, social, and emotional well-being. Limited transportation to the mall was a barrier to participation. We found the potential for mall walking programs to be implemented in various communities as a health promotion measure. However, the research on mall walking programs is limited and has weak study designs. More rigorous research is needed to define best practices for mall walking programs' reach, effectiveness, adoption

  15. Bicycling and Walking are Associated with Different Cortical Oscillatory Dynamics.

    PubMed

    Storzer, Lena; Butz, Markus; Hirschmann, Jan; Abbasi, Omid; Gratkowski, Maciej; Saupe, Dietmar; Schnitzler, Alfons; Dalal, Sarang S

    2016-01-01

    Although bicycling and walking involve similar complex coordinated movements, surprisingly Parkinson's patients with freezing of gait typically remain able to bicycle despite severe difficulties in walking. This observation suggests functional differences in the motor networks subserving bicycling and walking. However, a direct comparison of brain activity related to bicycling and walking has never been performed, neither in healthy participants nor in patients. Such a comparison could potentially help elucidating the cortical involvement in motor control and the mechanisms through which bicycling ability may be preserved in patients with freezing of gait. The aim of this study was to contrast the cortical oscillatory dynamics involved in bicycling and walking in healthy participants. To this end, EEG and EMG data of 14 healthy participants were analyzed, who cycled on a stationary bicycle at a slow cadence of 40 revolutions per minute (rpm) and walked at 40 strides per minute (spm), respectively. Relative to walking, bicycling was associated with a stronger power decrease in the high beta band (23-35 Hz) during movement initiation and execution, followed by a stronger beta power increase after movement termination. Walking, on the other hand, was characterized by a stronger and persisting alpha power (8-12 Hz) decrease. Both bicycling and walking exhibited movement cycle-dependent power modulation in the 24-40 Hz range that was correlated with EMG activity. This modulation was significantly stronger in walking. The present findings reveal differential cortical oscillatory dynamics in motor control for two types of complex coordinated motor behavior, i.e., bicycling and walking. Bicycling was associated with a stronger sustained cortical activation as indicated by the stronger high beta power decrease during movement execution and less cortical motor control within the movement cycle. We speculate this to be due to the more continuous nature of bicycling demanding

  16. Bicycling and Walking are Associated with Different Cortical Oscillatory Dynamics

    PubMed Central

    Storzer, Lena; Butz, Markus; Hirschmann, Jan; Abbasi, Omid; Gratkowski, Maciej; Saupe, Dietmar; Schnitzler, Alfons; Dalal, Sarang S.

    2016-01-01

    Although bicycling and walking involve similar complex coordinated movements, surprisingly Parkinson’s patients with freezing of gait typically remain able to bicycle despite severe difficulties in walking. This observation suggests functional differences in the motor networks subserving bicycling and walking. However, a direct comparison of brain activity related to bicycling and walking has never been performed, neither in healthy participants nor in patients. Such a comparison could potentially help elucidating the cortical involvement in motor control and the mechanisms through which bicycling ability may be preserved in patients with freezing of gait. The aim of this study was to contrast the cortical oscillatory dynamics involved in bicycling and walking in healthy participants. To this end, EEG and EMG data of 14 healthy participants were analyzed, who cycled on a stationary bicycle at a slow cadence of 40 revolutions per minute (rpm) and walked at 40 strides per minute (spm), respectively. Relative to walking, bicycling was associated with a stronger power decrease in the high beta band (23–35 Hz) during movement initiation and execution, followed by a stronger beta power increase after movement termination. Walking, on the other hand, was characterized by a stronger and persisting alpha power (8–12 Hz) decrease. Both bicycling and walking exhibited movement cycle-dependent power modulation in the 24–40 Hz range that was correlated with EMG activity. This modulation was significantly stronger in walking. The present findings reveal differential cortical oscillatory dynamics in motor control for two types of complex coordinated motor behavior, i.e., bicycling and walking. Bicycling was associated with a stronger sustained cortical activation as indicated by the stronger high beta power decrease during movement execution and less cortical motor control within the movement cycle. We speculate this to be due to the more continuous nature of bicycling

  17. Mall Walking Program Environments, Features, and Participants: A Scoping Review

    PubMed Central

    Belza, Basia; Allen, Peg; Brolliar, Sarah; Brown, David R.; Cormier, Marc L.; Janicek, Sarah; Jones, Dina L.; King, Diane K.; Marquez, David X.; Rosenberg, Dori E.

    2015-01-01

    Introduction Walking is a preferred and recommended physical activity for middle-aged and older adults, but many barriers exist, including concerns about safety (ie, personal security), falling, and inclement weather. Mall walking programs may overcome these barriers. The purpose of this study was to summarize the evidence on the health-related value of mall walking and mall walking programs. Methods We conducted a scoping review of the literature to determine the features, environments, and benefits of mall walking programs using the RE-AIM framework (reach, effectiveness, adoption, implementation, and maintenance). The inclusion criteria were articles that involved adults aged 45 years or older who walked in indoor or outdoor shopping malls. Exclusion criteria were articles that used malls as laboratory settings or focused on the mechanics of walking. We included published research studies, dissertations, theses, conference abstracts, syntheses, nonresearch articles, theoretical papers, editorials, reports, policy briefs, standards and guidelines, and nonresearch conference abstracts and proposals. Websites and articles written in a language other than English were excluded. Results We located 254 articles on mall walking; 32 articles met our inclusion criteria. We found that malls provided safe, accessible, and affordable exercise environments for middle-aged and older adults. Programmatic features such as program leaders, blood pressure checks, and warm-up exercises facilitated participation. Individual benefits of mall walking programs included improvements in physical, social, and emotional well-being. Limited transportation to the mall was a barrier to participation. Conclusion We found the potential for mall walking programs to be implemented in various communities as a health promotion measure. However, the research on mall walking programs is limited and has weak study designs. More rigorous research is needed to define best practices for mall walking

  18. Design and use of improved walking aids.

    PubMed

    Nava, L C; Laura, P A

    1985-10-01

    The design of crutches and walking sticks to assist the disabled has not varied much since their original conception, some 5000 years ago. From an engineering viewpoint one must consider crutches and walking sticks as dynamic mechanical systems which alleviate a disability; they may act as supports, help the user to recover from stumbling, or transmit from the arms, the energy required to lift the feet from the ground, an action not provided by artificial ankle joints. We describe some dynamic walking aids recently developed at the Instituto de Mecánica Aplicada, and discuss their design and our experience with their use. They are adjustable in height, shock absorbing and have non-slipping tips. Specially developed aids have been designed for children; they are versatile and their use has been made psychologically attractive.

  19. Predicting metabolic rate across walking speed: One fit for all body sizes?

    USDA-ARS?s Scientific Manuscript database

    We formulated a "one-size-fits-all" model that predicts the energy requirements of level human walking from height, weight, and walking speed. Our three-component model theorizes that the energy expended per kilogram per stride is independent of stature at mechanically equivalent walking speeds. We ...

  20. Walking in My Shoes

    ERIC Educational Resources Information Center

    Salia, Hannah

    2010-01-01

    The Walking in My Shoes curriculum at St. Thomas School in Medina, Washington, has been developed to deepen students' understanding of their own heritage and the cultural similarities and differences among their global peers. Exploring the rich diversity of the world's cultural heritage and the interactions of global migrations throughout history,…

  1. Deterministic Walks with Choice

    SciTech Connect

    Beeler, Katy E.; Berenhaut, Kenneth S.; Cooper, Joshua N.; Hunter, Meagan N.; Barr, Peter S.

    2014-01-10

    This paper studies deterministic movement over toroidal grids, integrating local information, bounded memory and choice at individual nodes. The research is motivated by recent work on deterministic random walks, and applications in multi-agent systems. Several results regarding passing tokens through toroidal grids are discussed, as well as some open questions.

  2. Walking in My Shoes

    ERIC Educational Resources Information Center

    Salia, Hannah

    2010-01-01

    The Walking in My Shoes curriculum at St. Thomas School in Medina, Washington, has been developed to deepen students' understanding of their own heritage and the cultural similarities and differences among their global peers. Exploring the rich diversity of the world's cultural heritage and the interactions of global migrations throughout history,…

  3. Take a Planet Walk

    ERIC Educational Resources Information Center

    Schuster, Dwight

    2008-01-01

    Physical models in the classroom "cannot be expected to represent the full-scale phenomenon with complete accuracy, not even in the limited set of characteristics being studied" (AAAS 1990). Therefore, by modifying a popular classroom activity called a "planet walk," teachers can explore upper elementary students' current understandings; create an…

  4. A Walk Back.

    ERIC Educational Resources Information Center

    Greenslade, Cleo B.

    1988-01-01

    Discusses a walking trip through Elfers, Florida, which gives intermediate level students a basis for a real understanding of the state's history, climate, economy, and natural resources. Describes how students prepare for the outing by examining maps and interviewing their parents and grandparents about life when they were in school. (GEA)

  5. Walking Out Graphs

    ERIC Educational Resources Information Center

    Shen, Ji

    2009-01-01

    In the Walking Out Graphs Lesson described here, students experience several types of representations used to describe motion, including words, sentences, equations, graphs, data tables, and actions. The most important theme of this lesson is that students have to understand the consistency among these representations and form the habit of…

  6. Walking Advisement: Program Description.

    ERIC Educational Resources Information Center

    Byram Hills School District, Armonk, NY.

    The Walking Advisement program at Crittenden Middle School in Armonk, New York was started during the 1984-1985 school year. It was based on the work of Alfred Arth, a middle school specialist at the University of Wyoming. Essentially, the program attempts to expand the guidance function of the school by bringing faculty and students together to…

  7. Take a Planet Walk

    ERIC Educational Resources Information Center

    Schuster, Dwight

    2008-01-01

    Physical models in the classroom "cannot be expected to represent the full-scale phenomenon with complete accuracy, not even in the limited set of characteristics being studied" (AAAS 1990). Therefore, by modifying a popular classroom activity called a "planet walk," teachers can explore upper elementary students' current understandings; create an…

  8. A Walk through Time.

    ERIC Educational Resources Information Center

    Renfroe, Mark; Letendre, Wanda

    1996-01-01

    Describes a seventh-grade class project where students constructed a "time tunnel" (a walk-through display with models and exhibits illustrating various themes and eras). Beginning modestly, the tunnel grew over seven years to include 11 different display scenes. Discusses the construction of the project and benefits to the school. (MJP)

  9. Walking with a Slower Friend

    ERIC Educational Resources Information Center

    Bailey, Herb; Kalman, Dan

    2011-01-01

    Fay and Sam go for a walk. Sam walks along the left side of the street while Fay, who walks faster, starts with Sam but walks to a point on the right side of the street and then returns to meet Sam to complete one segment of their journey. We determine Fay's optimal path minimizing segment length, and thus maximizing the number of times they meet…

  10. Walking with a Slower Friend

    ERIC Educational Resources Information Center

    Bailey, Herb; Kalman, Dan

    2011-01-01

    Fay and Sam go for a walk. Sam walks along the left side of the street while Fay, who walks faster, starts with Sam but walks to a point on the right side of the street and then returns to meet Sam to complete one segment of their journey. We determine Fay's optimal path minimizing segment length, and thus maximizing the number of times they meet…

  11. How to walk a conveyor

    SciTech Connect

    2007-06-15

    The article gives a check list of what one should know before walking a belt conveyor, and what to do during the walk. It then presents a list of what to look at on a walk along the conveyor system (excluding related equipment which could be inspected or maintained during the walk). It gives advice on when to stop the conveyor, on testing the emergency stop system, on recording problems and on acting on things noted. 1 tab.

  12. Comparative Anatomy of the Hind Limb Vessels of the Bearded Capuchins (Sapajus libidinosus) with Apes, Baboons, and Cebus capucinus: With Comments on the Vessels' Role in Bipedalism

    PubMed Central

    Aversi-Ferreira, Roqueline A. G. M. F.; de Abreu, Tainá; Pfrimer, Gabriel A.; Silva, Sylla F.; Ziermann, Janine M.; Carneiro-e-Silva, Frederico O.; Tomaz, Carlos; Tavares, Maria Clotilde H.; Maior, Rafael S.; Aversi-Ferreira, Tales A.

    2013-01-01

    Capuchin monkeys are known to exhibit sporadic bipedalism while performing specific tasks, such as cracking nuts. The bipedal posture and locomotion cause an increase in the metabolic cost and therefore increased blood supply to lower limbs is necessary. Here, we present a detailed anatomical description of the capuchin arteries and veins of the pelvic limb of Sapajus libidinosus in comparison with other primates. The arterial pattern of the bearded capuchin hind limb is more similar to other quadrupedal Cebus species. Similarities were also found to the pattern observed in the quadruped Papio, which is probably due to a comparable pelvis and the presence of the tail. Sapajus' traits show fewer similarities when compared to great apes and modern humans. Moreover, the bearded capuchin showed unique patterns for the femoral and the short saphenous veins. Although this species switches easily from quadrupedal to bipedal postures, our results indicate that the bearded capuchin has no specific or differential features that support extended bipedal posture and locomotion. Thus, the explanation for the behavioral differences found among capuchin genera probably includes other aspects of their physiology. PMID:24396829

  13. Autonomous exoskeleton reduces metabolic cost of walking.

    PubMed

    Mooney, Luke M; Rouse, Elliott J; Herr, Hugh M

    2014-01-01

    We developed an autonomous powered leg exoskeleton capable of providing large amounts of positive mechanical power to the wearer during powered plantarflexion phase of walking. The autonomous exoskeleton consisted of a winch actuator fasted to the shin which pulled on fiberglass struts attached to a boot. The fiberglass struts formed a rigid extension of the foot when the proximal end of the strut was pulled in forward by the winch actuator. This lightweight, geometric transmission allowed the electric winch actuator to efficiently produce biological levels of power at the ankle joint. The exoskeleton was powered and controlled by lithium polymer batteries and motor controller worn around the waist. Preliminary testing on two subjects walking at 1.4 m/s resulted in the exoskeleton reducing the metabolic cost of walking by 6-11% as compared to not wearing the device. The exoskeleton provided a peak mechanical power of over 180 W at each ankle (mean standard ± deviation) and an average positive mechanical power of 27 ± 1 W total to both ankles, while electrically using 75-89 W of electricity. The batteries (800 g) used in this experiment are estimated to be capable of providing this level of assistance for up to 7 km of walking.

  14. Comparing normal walking and compensated walking: their stability and perturbation resistance. A simulation study.

    PubMed

    Yu, W; Ikemoto, Y; Acharya, R; Unoue, J

    2010-01-01

    People usually develop different kinds of compensated gait in response to local function deficits, such as muscle weakness, spasticity in specific muscle groups, or joint stiffness, in order to overcome the falling risk factors. Compensated walking has been analysed empirically in the impaired gait analysis area. However, the compensation could be identified spatially and temporally. The stability and perturbation resistance of compensated walking have not been analysed quantitatively. In this research, a biomimetic human walking simulator was employed to model one individual paraplegic subject with plantarflexor spasticity. The pes equinus was expressed by biasing the outputs of plantarflexor neurons corresponding to the spastic muscles. Then, the compensatory mechanism was explored by adjusting the outputs of the other muscles. It was shown that this approach can be used for quantitative analysis of the spastic gait and compensated walking. Thus, this research can improve the understanding of the behaviour of compensated walking, bringing insights not only for building useful walking assist systems with high safety but also for designing effective rehabilitation interventions.

  15. FOOT PLACEMENT IN A BODY REFERENCE FRAME DURING WALKING AND ITS RELATIONSHIP TO HEMIPARETIC WALKING PERFORMANCE

    PubMed Central

    Balasubramanian, Chitralakshmi K.; Neptune, Richard R.; Kautz, Steven A.

    2010-01-01

    Background Foot placement during walking is closely linked to the body position, yet it is typically quantified relative to the other foot. The purpose of this study was to quantify foot placement patterns relative to body post-stroke and investigate its relationship to hemiparetic walking performance. Methods Thirty-nine participants with hemiparesis walked on a split-belt treadmill at their self-selected speeds and twenty healthy participants walked at matched slow speeds. Anterior-posterior and medial-lateral foot placements (foot center-of-mass) relative to body (pelvis center-of-mass) quantified stepping in body reference frame. Walking performance was quantified using step length asymmetry ratio, percent of paretic propulsion and paretic weight support. Findings Participants with hemiparesis placed their paretic foot further anterior than posterior during walking compared to controls walking at matched slow speeds (p < .05). Participants also placed their paretic foot further lateral relative to pelvis than non-paretic (p < .05). Anterior-posterior asymmetry correlated with step length asymmetry and percent paretic propulsion but some persons revealed differing asymmetry patterns in the translating reference frame. Lateral foot placement asymmetry correlated with paretic weight support (r = .596; p < .001), whereas step widths showed no relation to paretic weight support. Interpretation Post-stroke gait is asymmetric when quantifying foot placement in a body reference frame and this asymmetry related to the hemiparetic walking performance and explained motor control mechanisms beyond those explained by step lengths and step widths alone. We suggest that biomechanical analyses quantifying stepping performance in impaired populations should investigate foot placement in a body reference frame. PMID:20193972

  16. The phylogenetic position of the musky rat-kangaroo and the evolution of bipedal hopping in kangaroos (Macropodidae: Diprotodontia).

    PubMed

    Burk, A; Westerman, M; Springer, M

    1998-09-01

    Kangaroos and their relatives (family Macropodidae) are divided into the subfamilies Macropodinae (kangaroos, wallabies, pademelons) and Potoroinae (rat-kangaroos, potoroos, bettongs). The musky rat-kangaroo, Hypsiprymnodon moschatus, is traditionally allied with other potoroines, based primarily on the basis of osteological characters and aspects of the female reproductive system. Unlike other macropodids, however, which are capable of bipedal hopping, Hypsiprymnodon is a quadrupedal bounder and lacks several derived features of the pes and tarsus that are presumably adaptations for bipedal hopping. Other derived features, such as a complex stomach, loss of P2 with the eruption of P3, and reduction of litter size to one, are also lacking in Hypsiprymnodon but occur in all other macropodids. Thus, available evidence suggests that Hypsiprymnodon either is part of a monophyletic Potoroinae or is a sister taxon to other living macropodids. To test these hypotheses, we sequenced 1,170 bp base pairs of the mitochondrial genome for 16 macropodids. Maximum parsimony, minimum evolution, maximum likelihood, and quartet puzzling all support the hypothesis that macropodines and potoroines are united to the exclusion of Hypsiprymnodon. This hypothesis implies that characters such as bipedal hopping evolved only once in macropodid evolution. Aside from Hypsiprymnodon, the remaining macropodids separate into the traditional Macropodinae and Potoroinae. Macropodines further separate into two clades: one containing the New Guinean forest wallabies Dorcopsis and Dorcopsulus, and one consisting of the genera Macropus, Setonix, Thylogale, Onychogalea, Wallabia, Dendrolagus, Peradorcas, and Lagorchestes. Among potoroines, there is moderate support for the association of Bettongia and Aepyprymnus to the exclusion of Potorous. Divergence times were estimated by using 12S ribosomal RNA transversions. At the base of the macropodid radiation, Hypsiprymnodon diverged from other macropodids

  17. The effect of calmodulin antagonists on scoliosis: bipedal C57BL/6 mice model.

    PubMed

    Akel, Ibrahim; Demirkiran, Gokhan; Alanay, Ahmet; Karahan, Sevilay; Marcucio, Ralph; Acaroglu, Emre

    2009-04-01

    C57BL6 mice are melatonin deficient from birth and have been shown to develop scoliosis when rendered bipedal. Our previous work suggested that tamoxifen and trifluoperozine may change the natural course of scoliosis in a chicken model. The objective of this study was to analyze whether the incidence of scoliosis or the magnitude of curves may be decreased by the administration of pharmacological agents tamoxifen or trifluoperozine in a mice scoliosis model. Sixty female 3-week-old C57BL6 mice underwent amputations of forelimbs and tails. Available 57 mice were divided into three groups, Group-I received no medications whereas Groups II and III received 10 mg TMX and 10 mg TMX + 10 mg TFP per liter of daily water supply, respectively. PA scoliosis X-rays were obtained at 20th and 40th weeks. Deformities were compared for incidence and the severity of the curves as well as disease progression or regression. At 20th week, overall, upper thoracic (UT), lower thoracic (T), and lumbar (L) scoliosis rates were similar (P = 0.531; P = 0.209; P = 0.926; P = 0.215, respectively) but thoraco-lumbar (TL) scoliosis rate was higher inTMX group (P = 0.036). However, at 40th week, although TL and L rates were similar (P = 0.628, P = 0.080), overall rate as well as the rates of UT and T scoliosis of TMX group were significantly lower (P = 0.001, P = 0.011, P = 0.001, respectively). As for curve magnitudes, T mean Cobb angle at 20th week was significantly higher in the C group (14 +/- 2.55) compared to TMX + TFP group (9 +/- 2.708; P = 0.033); at 40th week, TL mean Cobb angle was lower in the TMX + TFP group (17.50 +/- 3.45) compared to C (29.40 +/- 5.98; P = 0.031); and TMX group had lower TL Cobb angles compared to C (8.67 +/- 11.72) although not significant (P = 0.109). Double curve incidence at 40th week was significantly lower in TMX group compared to other groups (P = 0.001), triple curve incidence was lower in TMX + TFP and TMX groups, albeit not significant (P = 0

  18. Spin-1 quantum walks

    NASA Astrophysics Data System (ADS)

    Morita, Daichi; Kubo, Toshihiro; Tokura, Yasuhiro; Yamashita, Makoto

    2016-06-01

    We study the quantum walks of two interacting spin-1 bosons. We derive an exact solution for the time-dependent wave function, which describes the two-particle dynamics governed by the one-dimensional spin-1 Bose-Hubbard model. We show that propagation dynamics in real space and mixing dynamics in spin space are correlated via the spin-dependent interaction in this system. The spin-mixing dynamics has two characteristic frequencies in the limit of large spin-dependent interactions. One of the characteristic frequencies is determined by the energy difference between two bound states, and the other frequency relates to the cotunneling process of a pair of spin-1 bosons. Furthermore, we numerically analyze the growth of the spin correlations in quantum walks. We find that long-range spin correlations emerge showing a clear dependence on the sign of the spin-dependent interaction and the initial state.

  19. Bobcat Walking and Swimming

    NASA Image and Video Library

    2014-03-06

    CAPE CANAVERAL, Fla. – A bobcat walks on the shore of a canal near the NASA News Center at Kennedy Space Center in Florida. The center shares a boundary with the Merritt Island National Wildlife Refuge. The refuge encompasses 140,000 acres that are a habitat for more than 330 species of birds, 31 mammals, 117 fishes, and 65 amphibians and reptiles. Photo credit: NASA/Daniel Casper

  20. Bobcat Walking and Swimming

    NASA Image and Video Library

    2014-03-06

    CAPE CANAVERAL, Fla. – A bobcat walks along a canal near the NASA News Center at Kennedy Space Center in Florida. The center shares a boundary with the Merritt Island National Wildlife Refuge. The refuge encompasses 140,000 acres that are a habitat for more than 330 species of birds, 31 mammals, 117 fishes, and 65 amphibians and reptiles. Photo credit: NASA/Daniel Casper

  1. Bobcat Walking and Swimming

    NASA Image and Video Library

    2014-03-06

    CAPE CANAVERAL, Fla. – A bobcat walks along a canal near the NASA News Center at Kennedy Space Center in Florida. The center shares a boundary with the Merritt Island National Wildlife Refuge. The refuge encompasses 140,000 acres that are a habitat for more than 330 species of birds, 31 mammals, 117 fishes, and 65 amphibians and reptiles. Photo credit: NASA/Daniel Casper. Note: Selected image is cropped

  2. Bobcat Walking and Swimming

    NASA Image and Video Library

    2014-03-06

    CAPE CANAVERAL, Fla. – A bobcat pauses to look back at the photographer while out for a walk at NASA's Kennedy Space Center in Florida. The center shares a boundary with the Merritt Island National Wildlife Refuge. The refuge encompasses 140,000 acres that are a habitat for more than 330 species of birds, 31 mammals, 117 fishes, and 65 amphibians and reptiles. Photo credit: NASA/Daniel Casper Note: selected image is cropped

  3. Walking with springs

    NASA Astrophysics Data System (ADS)

    Sugar, Thomas G.; Hollander, Kevin W.; Hitt, Joseph K.

    2011-04-01

    Developing bionic ankles poses great challenges due to the large moment, power, and energy that are required at the ankle. Researchers have added springs in series with a motor to reduce the peak power and energy requirements of a robotic ankle. We developed a "robotic tendon" that reduces the peak power by altering the required motor speed. By changing the required speed, the spring acts as a "load variable transmission." If a simple motor/gearbox solution is used, one walking step would require 38.8J and a peak motor power of 257 W. Using an optimized robotic tendon, the energy required is 21.2 J and the peak motor power is reduced to 96.6 W. We show that adding a passive spring in parallel with the robotic tendon reduces peak loads but the power and energy increase. Adding a passive spring in series with the robotic tendon reduces the energy requirements. We have built a prosthetic ankle SPARKy, Spring Ankle with Regenerative Kinetics, that allows a user to walk forwards, backwards, ascend and descend stairs, walk up and down slopes as well as jog.

  4. Treadmill walking of the pneumatic biped Lucy: Walking at different speeds and step-lengths

    NASA Astrophysics Data System (ADS)

    Vanderborght, B.; Verrelst, B.; Van Ham, R.; Van Damme, M.; Versluys, R.; Lefeber, D.

    2008-07-01

    Actuators with adaptable compliance are gaining interest in the field of legged robotics due to their capability to store motion energy and to exploit the natural dynamics of the system to reduce energy consumption while walking and running. To perform research on compliant actuators we have built the planar biped Lucy. The robot has six actuated joints, the ankle, knee and hip of both legs with each joint powered by two pleated pneumatic artificial muscles in an antagonistic setup. This makes it possible to control both the torque and the stiffness of the joint. Such compliant actuators are used in passive walkers to overcome friction when walking over level ground and to improve stability. Typically, this kind of robots is only designed to walk with a constant walking speed and step-length, determined by the mechanical design of the mechanism and the properties of the ground. In this paper, we show that by an appropriate control, the robot Lucy is able to walk at different speeds and step-lengths and that adding and releasing weights does not affect the stability of the robot. To perform these experiments, an automated treadmill was built

  5. Running for Exercise Mitigates Age-Related Deterioration of Walking Economy

    PubMed Central

    Ortega, Justus D.; Beck, Owen N.; Roby, Jaclyn M.; Turney, Aria L.; Kram, Rodger

    2014-01-01

    Introduction Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy. Purpose To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults. Methods 15 older adults (69±3 years) who walk ≥30 min, 3x/week for exercise, “walkers” and 15 older adults (69±5 years) who run ≥30 min, 3x/week, “runners” walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study. Results Older runners had a 7–10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p = .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p = .461) and ∼26% worse walking economy than young adults (p<.0001). Conclusion Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy. PMID:25411850

  6. Running for exercise mitigates age-related deterioration of walking economy.

    PubMed

    Ortega, Justus D; Beck, Owen N; Roby, Jaclyn M; Turney, Aria L; Kram, Rodger

    2014-01-01

    Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy. To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults. 15 older adults (69 ± 3 years) who walk ≥ 30 min, 3x/week for exercise, "walkers" and 15 older adults (69 ± 5 years) who run ≥ 30 min, 3x/week, "runners" walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study. Older runners had a 7-10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p =  .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p =  .461) and ∼ 26% worse walking economy than young adults (p<.0001). Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy.

  7. Quantum random walk polynomial and quantum random walk measure

    NASA Astrophysics Data System (ADS)

    Kang, Yuanbao; Wang, Caishi

    2014-05-01

    In the paper, we introduce a quantum random walk polynomial (QRWP) that can be defined as a polynomial , which is orthogonal with respect to a quantum random walk measure (QRWM) on , such that the parameters are in the recurrence relations and satisfy . We firstly obtain some results of QRWP and QRWM, in which case the correspondence between measures and orthogonal polynomial sequences is one-to-one. It shows that any measure with respect to which a quantum random walk polynomial sequence is orthogonal is a quantum random walk measure. We next collect some properties of QRWM; moreover, we extend Karlin and McGregor's representation formula for the transition probabilities of a quantum random walk (QRW) in the interacting Fock space, which is a parallel result with the CGMV method. Using these findings, we finally obtain some applications for QRWM, which are of interest in the study of quantum random walk, highlighting the role played by QRWP and QRWM.

  8. Fractional random walk lattice dynamics

    NASA Astrophysics Data System (ADS)

    Michelitsch, T. M.; Collet, B. A.; Riascos, A. P.; Nowakowski, A. F.; Nicolleau, F. C. G. A.

    2017-02-01

    We analyze time-discrete and time-continuous ‘fractional’ random walks on undirected regular networks with special focus on cubic periodic lattices in n  =  1, 2, 3,.. dimensions. The fractional random walk dynamics is governed by a master equation involving fractional powers of Laplacian matrices {{L}\\fracα{2}}} where α =2 recovers the normal walk. First we demonstrate that the interval 0<α ≤slant 2 is admissible for the fractional random walk. We derive analytical expressions for the transition matrix of the fractional random walk and closely related the average return probabilities. We further obtain the fundamental matrix {{Z}(α )} , and the mean relaxation time (Kemeny constant) for the fractional random walk. The representation for the fundamental matrix {{Z}(α )} relates fractional random walks with normal random walks. We show that the matrix elements of the transition matrix of the fractional random walk exihibit for large cubic n-dimensional lattices a power law decay of an n-dimensional infinite space Riesz fractional derivative type indicating emergence of Lévy flights. As a further footprint of Lévy flights in the n-dimensional space, the transition matrix and return probabilities of the fractional random walk are dominated for large times t by slowly relaxing long-wave modes leading to a characteristic {{t}-\\frac{n{α}} -decay. It can be concluded that, due to long range moves of fractional random walk, a small world property is emerging increasing the efficiency to explore the lattice when instead of a normal random walk a fractional random walk is chosen.

  9. Predicting sagittal plane biomechanics that minimize the axial knee joint contact force during walking.

    PubMed

    Miller, Ross H; Brandon, Scott C E; Deluzio, Kevin J

    2013-01-01

    Both development and progression of knee osteoarthritis have been associated with the loading of the knee joint during walking. We are, therefore, interested in developing strategies for changing walking biomechanics to offload the knee joint without resorting to surgery. In this study, simulations of human walking were performed using a 2D bipedal forward dynamics model. A simulation generated by minimizing the metabolic cost of transport (CoT) resembled data measured from normal human walking. Three simulations targeted at minimizing the peak axial knee joint contact force instead of the CoT reduced the peak force by 12-25% and increased the CoT by 11-14%. The strategies used by the simulations were (1) reduction in gastrocnemius muscle force, (2) avoidance of knee flexion during stance, and (3) reduced stride length. Reduced gastrocnemius force resulted from a combination of changes in activation and changes in the gastrocnemius contractile component kinematics. The simulations that reduced the peak contact force avoided flexing the knee during stance when knee motion was unrestricted and adopted a shorter stride length when the simulated knee motion was penalized if it deviated from the measured human knee motion. A higher metabolic cost in an offloading gait would be detrimental for covering a long distance without fatigue but beneficial for exercise and weight loss. The predicted changes in the peak axial knee joint contact force from the simulations were consistent with estimates of the joint contact force in a human subject who emulated the predicted kinematics. The results demonstrate the potential of using muscle-actuated forward dynamics simulations to predict novel joint offloading interventions.

  10. Tripedal knuckle-walking: a proposal for the evolution of human locomotion and handedness.

    PubMed

    Kelly, R E

    2001-12-07

    A comparative morphological analysis of human and non-human hominoids was conducted in an attempt to determine the mode of locomotion of the protohominid. Although the generalized hominoid anatomy permits variation of locomotion: brachiation, knuckle-walking, etc., minor variations in structure determine which behavior is favored. Arboreal arm swinging requires a flexible forelimb while terrestrial fist or knuckle-walking demands more rigidity of the hand and wrist. It is demonstrated that the large human thumb accompanied by the strong adduction of the thenar, hypothenar, and palmar interosseous muscles offer powerful rigidity to the hand, while fusion of the os centrale with the scaphoid during gestation permits the formation of an arch of carpals which imbue the wrist with the stability necessary for weight bearing. Fascialization of the contrahentes and dorsiepitrochlearis muscles in the human as well as depilation of the middle phalanges; the webbing (syndactyly) of the palm; the direction of the fibers of the interosseous membrane of the forearm; the shape of the puerile annular ligament, and the direction of the human glenoid fossa strongly suggest that the ancestor of man used a knuckle-walking form of locomotion prior to becoming bipedal. A model is presented that suggests that bipedalism was attained through an intermediate stage of tripedalism. The model is based on the fact that man's anatomy is much more asymmetric than that of the great apes. A presumption is made that due to the absence of trees for climbing in the transition from forest to open plain, the protohominid needed to carry tools (stones) at all times for protection. Stones could be carried for long distances on the posterior iliac crest since the weight would be shifted posteriorly over the legs. Pick up, medial rotation and adduction of the stone would employ a two-muscle chain of biceps brachii and latissimus dorsi. On the iliac crest, the stone is posterior to the coronal plane of the

  11. 10 CFR 431.302 - Definitions concerning walk-in coolers and walk-in freezers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... cooler or walk-in freezer that are not part of its refrigeration system. K-factor means the thermal... not limited to, refrigeration, doors, lights, windows, or walls; or (2) Manufactures or assembles the... Fahrenheit using a refrigeration system. Refrigeration system means the mechanism (including all controls...

  12. 10 CFR 431.302 - Definitions concerning walk-in coolers and walk-in freezers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... cooler or walk-in freezer that are not part of its refrigeration system. K-factor means the thermal... not limited to, refrigeration, doors, lights, windows, or walls; or (2) Manufactures or assembles the... Fahrenheit using a refrigeration system. Refrigeration system means the mechanism (including all controls...

  13. 10 CFR 431.302 - Definitions concerning walk-in coolers and walk-in freezers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... cooler or walk-in freezer that are not part of its refrigeration system. K-factor means the thermal... not limited to, refrigeration, doors, lights, windows, or walls; or (2) Manufactures or assembles the... Fahrenheit using a refrigeration system. Refrigeration system means the mechanism (including all controls...

  14. New wearable walking-type continuous passive motion device for postsurgery walking rehabilitation.

    PubMed

    Zhu, Yong; Nakamura, Masahiro; Horiuchi, Tadahiro; Kohno, Hideki; Takahashi, Rei; Terada, Hidetsugu; Haro, Hirotaka

    2013-07-01

    While total knee arthroplasty is useful for treating osteoarthritis of the knee, the success of this treatment depends on effective rehabilitation. The goal of this study was to develop an assistive device for post-total knee arthroplasty patients for walking rehabilitation and for shortening the hospitalization period. We developed a brace electronic assist system termed the knee assistive instrument for walking rehabilitation (KAI-R) to illustrate the need for training during postoperative rehabilitation. Sixteen osteoarthritis patients (1 male and 15 females; average age 68.9 years) who underwent total knee arthroplasty were analyzed before operation and 2-4 weeks after operation, and 25 healthy individuals (14 males and 11 females; average age 26.2 years) formed the control group. Based on the pre- and postoperative data on peak knee flexion angle, foot height, and walking velocity, we developed the KAI-R, which consists of an assistive mechanism for the knee joint, a hip joint support system, and a foot pressure sensor system and is driven by a CPU board that generates the walking pattern. We then tested the walking gait in seven healthy volunteers with and without KAI-R assistance. KAI-R increased the peak flexion angle of the knee and foot height in all seven volunteers; their range of motion of the knee joint was increased. However, KAI-R also decreased the walking velocity of subjects, which was explained by reaction delay and slightly compromised physical balance, which was caused by wearing the KAI-R. KAI-R is useful for gait improvement. In future studies, KAI-R will be investigated in a clinical trial for its ability for walking rehabilitation in post-total knee arthroplasty patients.

  15. Pedometer accuracy in slow walking older adults

    PubMed Central

    Martin, Jessica B.; Krč, Katarina M.; Mitchell, Emily A.; Eng, Janice J.; Noble, Jeremy W.

    2013-01-01

    The purpose of this study was to determine pedometer accuracy during slow overground walking in older adults (Mean age = 63.6 years). A total of 18 participants (6 males, 12 females) wore 5 different brands of pedometers over 3 pre-set cadences that elicited walking speeds between 0.3 and 0.9 m/s and one self-selected cadence over 80 meters of indoor track. Pedometer accuracy decreased with slower walking speeds with mean percent errors across all devices combined of 56%, 40%, 19% and 9% at cadences of 50, 66, and 80 steps/min, and self selected cadence, respectively. Percent error ranged from 45.3% for Omron HJ105 to 66.9% for Yamax Digiwalker 200. Due to the high level of error across the slowest cadences of all 5 devices, the use of pedometers to monitor step counts in healthy older adults with slower gait speeds is problematic. Further research is required to develop pedometer mechanisms that accurately measure steps at slower walking speeds. PMID:24795762

  16. Hip Joint Contact Force in the Emu (Dromaius novaehollandiae) during Normal Level Walking

    PubMed Central

    Goetz, Jessica E.; Derrick, Timothy R.; Pedersen, Douglas R.; Robinson, Duane A.; Conzemius, Michael G.; Baer, Thomas E.; Brown, Thomas D.

    2008-01-01

    The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratory-habituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lower-limb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders. PMID:18206892

  17. Perception, planning, and control for walking on rugged terrain

    NASA Technical Reports Server (NTRS)

    Simmons, Reid; Krotkov, Eric

    1991-01-01

    The CMU Planetary Rover project is developing a six-legged walking robot capable of autonomously navigating, exploring, and acquiring samples in rugged, unknown environments. To gain experience with the problems involved in walking on rugged terrain, a full-scale prototype leg was built and mounted on a carriage that rolls along overhead rails. Issues addressed in developing the software system to autonomously walk the leg through rugged terrain are described. In particular, the insights gained into perceiving and modeling rugged terrain, controlling the legged mechanism, interacting with the ground, choosing safe yet effective footfalls, and planning efficient leg moves through space are described.

  18. Agile Walking Robot

    NASA Technical Reports Server (NTRS)

    Larimer, Stanley J.; Lisec, Thomas R.; Spiessbach, Andrew J.; Waldron, Kenneth J.

    1990-01-01

    Proposed agile walking robot operates over rocky, sandy, and sloping terrain. Offers stability and climbing ability superior to other conceptual mobile robots. Equipped with six articulated legs like those of insect, continually feels ground under leg before applying weight to it. If leg sensed unexpected object or failed to make contact with ground at expected point, seeks alternative position within radius of 20 cm. Failing that, robot halts, examines area around foot in detail with laser ranging imager, and replans entire cycle of steps for all legs before proceeding.

  19. Rugged Walking Robot

    NASA Technical Reports Server (NTRS)

    Larimer, Stanley J.; Lisec, Thomas R.; Spiessbach, Andrew J.

    1990-01-01

    Proposed walking-beam robot simpler and more rugged than articulated-leg walkers. Requires less data processing, and uses power more efficiently. Includes pair of tripods, one nested in other. Inner tripod holds power supplies, communication equipment, computers, instrumentation, sampling arms, and articulated sensor turrets. Outer tripod holds mast on which antennas for communication with remote control site and video cameras for viewing local and distant terrain mounted. Propels itself by raising, translating, and lowering tripods in alternation. Steers itself by rotating raised tripod on turntable.

  20. Walking Machine Control Programming

    DTIC Science & Technology

    1983-08-31

    difficulty. 21 \\W;dkitiI M.’h 1 .(otri rot I’rogr ii ini g S A #2054 iI.Ld T’dl itdt Itort OWL WALKING ALGORITHMS The structure of the nervous system of...the nervous system . For this reason the cell it is usually attached to the ad- perpendicular axes and about acoustic the hair cell is sometimes...to drive air from the hydraulic system is to drive the compensator in while the ma- chine is tucked. The knee centering routine simply positions the

  1. Age-Associated Declines in Complex Walking Task Performance: The Walking InCHIANTI Toolkit

    PubMed Central

    Shumway-Cook, Anne; Guralnik, Jack M.; Phillips, Caroline L.; Coppin, Antonia K.; Ciol, Marcia A.; Bandinelli, Stefania; Ferrucci, Luigi

    2009-01-01

    OBJECTIVES To describe a set of complex walking tasks (CWTs) that can be used to evaluate mobility and to characterize age- and sex-specific performance on these tests. DESIGN A population-based study of persons living in the Chianti geographic area (Tuscany, Italy). SETTING Community. PARTICIPANTS One thousand two hundred twenty-seven persons (aged 20–95) selected from the city registries of Greve and Bagno a Ripoli (Tuscany, Italy). MEASUREMENTS Gait velocity (m/s) was measured during 13 walking tests (Walking InCHIANTI Toolkit (WIT)) used to examine walking ability under a range of conditions and distances. Other measures included performance on the Short Physical Performance Battery and self-reported health and functional status, including disability in activities of daily living. RESULTS Age-associated differences on the WIT were reflected in the number of older adults unable to complete CWTs and a decrease in gait velocity. For all tasks, decrements in walking speed with increasing age were significantly larger at aged 65 and older. Performance on CWTs was highly variable and could not be explained by usual gait speed measured under low-challenge conditions alone. CONCLUSION CWTs may provide important insight into mobility function, particularly in persons with normal or near-normal usual gait speed. Further research is needed to elucidate the specific physiological mechanisms that contribute to declining performance on CWT with increasing age. PMID:17233686

  2. Counterturns initiated by decrease in rate of increase of concentration : Possible mechanism of chemotaxis by walking femaleIps paraconfusus bark beetles.

    PubMed

    Patrick Akers, R

    1989-01-01

    The position of beetles were marked at 1-sec intervals after they were released in still air 16-18 cm from point sources of pheromone. Characteristics of the tracks were quantified and compared to those that might be produced by counterturning schemakinesis, tropotaxis, klinotaxis, zigzagging, look-and-leap, or steepest-ascent schemakinesis mechanisms. The beetles' movements were highly irregular, but they turned almost continually and never fixed on a heading near 0° (=straight towards the source). Turn angle sizes increased slightly with absolute size of heading but had the opposite sign, thus compensating slightly for heading. Their distribution was centered about 0° and was unimodal. Heading decreased gradually as the source was neared, but the decrease became steeper within 1-5 cm of the source. Histograms showed that the maximum headings between occurrences when the beetle was headed directly towards the source (0°) were centered around 0° and most of them were less than 90°. However, maximum headings between 90° and 180° were not uncommon. Turn radius decreased as the source was neared. The counterturning mechanism was the most consistent with these observations. An analysis of rate of change of concentration with respect to heading and distance to the source further demonstrated that the counterturning mechanism could explain the form of the decrease in heading as the source was neared, if the major cue used to initiate counterturns was a decrease in the rate of increase of concentration. The tropotaxis could not recreate the form of the decrease, under any form of stimulus processing.

  3. A relativistically covariant random walk

    NASA Astrophysics Data System (ADS)

    Almaguer, J.; Larralde, H.

    2007-08-01

    In this work we present and analyze an extremely simple relativistically covariant random walk model. In our approach, the probability density and the flow of probability arise naturally as the components of a four-vector and they are related to one another via a tensorial constitutive equation. We show that the system can be described in terms of an underlying invariant space time random walk parameterized by the number of sojourns. Finally, we obtain explicit expressions for the moments of the covariant random walk as well as for the underlying invariant random walk.

  4. Persistence of random walk records

    NASA Astrophysics Data System (ADS)

    Ben-Naim, E.; Krapivsky, P. L.

    2014-06-01

    We study records generated by Brownian particles in one dimension. Specifically, we investigate an ordinary random walk and define the record as the maximal position of the walk. We compare the record of an individual random walk with the mean record, obtained as an average over infinitely many realizations. We term the walk ‘superior’ if the record is always above average, and conversely, the walk is said to be ‘inferior’ if the record is always below average. We find that the fraction of superior walks, S, decays algebraically with time, S ˜ t-β, in the limit t → ∞, and that the persistence exponent is nontrivial, β = 0.382 258…. The fraction of inferior walks, I, also decays as a power law, I ˜ t-α, but the persistence exponent is smaller, α = 0.241 608…. Both exponents are roots of transcendental equations involving the parabolic cylinder function. To obtain these theoretical results, we analyze the joint density of superior walks with a given record and position, while for inferior walks it suffices to study the density as a function of position.

  5. Decoding Intra-Limb and Inter-Limb Kinematics During Treadmill Walking From Scalp Electroencephalographic (EEG) Signals

    PubMed Central

    Presacco, Alessandro; Forrester, Larry W.; Contreras-Vidal, Jose L.

    2012-01-01

    Brain–machine interface (BMI) research has largely been focused on the upper limb. Although restoration of gait function has been a long-standing focus of rehabilitation research, surprisingly very little has been done to decode the cortical neural networks involved in the guidance and control of bipedal locomotion. A notable exception is the work by Nicolelis’ group at Duke University that decoded gait kinematics from chronic recordings from ensembles of neurons in primary sensorimotor areas in rhesus monkeys. Recently, we showed that gait kinematics from the ankle, knee, and hip joints during human treadmill walking can be inferred from the electroencephalogram (EEG) with decoding accuracies comparable to those using intracortical recordings. Here we show that both intra- and inter-limb kinematics from human treadmill walking can be achieved with high accuracy from as few as 12 electrodes using scalp EEG. Interestingly, forward and backward predictors from EEG signals lagging or leading the kinematics, respectively, showed different spatial distributions suggesting distinct neural networks for feedforward and feedback control of gait. Of interest is that average decoding accuracy across subjects and decoding modes was ~0.68±0.08, supporting the feasibility of EEG-based BMI systems for restoration of walking in patients with paralysis. PMID:22438336

  6. Influence of Neuromuscular Noise and Walking Speed on Fall Risk and Dynamic Stability in a 3D Dynamic Walking Model

    PubMed Central

    Roos, Paulien E.; Dingwell, Jonathan B.

    2013-01-01

    Older adults and those with increased fall risk tend to walk slower. They may do this voluntarily to reduce their fall risk. However, both slower and faster walking speeds can predict increased risk of different types of falls. The mechanisms that contribute to fall risk across speeds are not well known. Faster walking requires greater forward propulsion, generated by larger muscle forces. However, greater muscle activation induces increased signal-dependent neuromuscular noise. These speed-related increases in neuromuscular noise may contribute to the increased fall risk observed at faster walking speeds. Using a 3D dynamic walking model, we systematically varied walking speed without and with physiologically-appropriate neuromuscular noise. We quantified how actual fall risk changed with gait speed, how neuromuscular noise affected speed-related changes in fall risk, and how well orbital and local dynamic stability measures predicted changes in fall risk across speeds. When we included physiologically-appropriate noise to the ‘push-off’ force in our model, fall risk increased with increasing walking speed. Changes in kinematic variability, orbital, and local dynamic stability did not predict these speed-related changes in fall risk. Thus, the increased neuromuscular variability that results from increased signal-dependent noise that is necessitated by the greater muscular force requirements of faster walking may contribute to the increased fall risk observed at faster walking speeds. The lower fall risk observed at slower speeds supports experimental evidence that slowing down can be an effective strategy to reduce fall risk. This may help explain the slower walking speeds observed in older adults and others. PMID:23659911

  7. Influence of neuromuscular noise and walking speed on fall risk and dynamic stability in a 3D dynamic walking model.

    PubMed

    Roos, Paulien E; Dingwell, Jonathan B

    2013-06-21

    Older adults and those with increased fall risk tend to walk slower. They may do this voluntarily to reduce their fall risk. However, both slower and faster walking speeds can predict increased risk of different types of falls. The mechanisms that contribute to fall risk across speeds are not well known. Faster walking requires greater forward propulsion, generated by larger muscle forces. However, greater muscle activation induces increased signal-dependent neuromuscular noise. These speed-related increases in neuromuscular noise may contribute to the increased fall risk observed at faster walking speeds. Using a 3D dynamic walking model, we systematically varied walking speed without and with physiologically-appropriate neuromuscular noise. We quantified how actual fall risk changed with gait speed, how neuromuscular noise affected speed-related changes in fall risk, and how well orbital and local dynamic stability measures predicted changes in fall risk across speeds. When we included physiologically-appropriate noise to the 'push-off' force in our model, fall risk increased with increasing walking speed. Changes in kinematic variability, orbital, and local dynamic stability did not predict these speed-related changes in fall risk. Thus, the increased neuromuscular variability that results from increased signal-dependent noise that is necessitated by the greater muscular force requirements of faster walking may contribute to the increased fall risk observed at faster walking speeds. The lower fall risk observed at slower speeds supports experimental evidence that slowing down can be an effective strategy to reduce fall risk. This may help explain the slower walking speeds observed in older adults and others. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Random-walk enzymes

    PubMed Central

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-01-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C → U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics. PMID:26465508

  9. Random-walk enzymes.

    PubMed

    Mak, Chi H; Pham, Phuong; Afif, Samir A; Goodman, Myron F

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C→U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  10. Random-walk enzymes

    NASA Astrophysics Data System (ADS)

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C →U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  11. New theory of diffusive and coherent nature of optical wave via a quantum walk

    NASA Astrophysics Data System (ADS)

    Ide, Yusuke; Konno, Norio; Matsutani, Shigeki; Mitsuhashi, Hideo

    2017-08-01

    We propose a new theory on a relation between diffusive and coherent nature in one dimensional wave mechanics based on a quantum walk. It is known that the quantum walk in homogeneous matrices provides the coherent property of wave mechanics. Using the recent result of a localization phenomenon in a one-dimensional quantum walk (Konno, 2010), we numerically show that the randomized localized matrices suppress the coherence and give diffusive nature.

  12. Intrinsic Lévy behaviour in organisms - searching for a mechanism. Comment on "Liberating Lévy walk research from the shackles of optimal foraging" by A.M. Reynolds

    NASA Astrophysics Data System (ADS)

    Sims, David W.

    2015-09-01

    The seminal papers by Viswanathan and colleagues in the late 1990s [1,2] proposed not only that scale-free, superdiffusive Lévy walks can describe the free-ranging movement patterns observed in animals such as the albatross [1], but that the Lévy walk was optimal for searching for sparsely and randomly distributed resource targets [2]. This distinct advantage, now shown to be present over a much broader set of conditions than originally theorised [3], implied that the Lévy walk is a search strategy that should be found very widely in organisms [4]. In the years since there have been several influential empirical studies showing that Lévy walks can indeed be detected in the movement patterns of a very broad range of taxa, from jellyfish, insects, fish, reptiles, seabirds, humans [5-10], and even in the fossilised trails of extinct invertebrates [11]. The broad optimality and apparent deep evolutionary origin of movement (search) patterns that are well approximated by Lévy walks led to the development of the Lévy flight foraging (LFF) hypothesis [12], which states that "since Lévy flights and walks can optimize search efficiencies, therefore natural selection should have led to adaptations for Lévy flight foraging".

  13. Unique characteristics of motor adaptation during walking in young children

    PubMed Central

    Musselman, Kristin E.; Patrick, Susan K.; Vasudevan, Erin V. L.; Bastian, Amy J.

    2011-01-01

    Children show precocious ability in the learning of languages; is this the case with motor learning? We used split-belt walking to probe motor adaptation (a form of motor learning) in children. Data from 27 children (ages 8–36 mo) were compared with those from 10 adults. Children walked with the treadmill belts at the same speed (tied belt), followed by walking with the belts moving at different speeds (split belt) for 8–10 min, followed again by tied-belt walking (postsplit). Initial asymmetries in temporal coordination (i.e., double support time) induced by split-belt walking were slowly reduced, with most children showing an aftereffect (i.e., asymmetry in the opposite direction to the initial) in the early postsplit period, indicative of learning. In contrast, asymmetries in spatial coordination (i.e., center of oscillation) persisted during split-belt walking and no aftereffect was seen. Step length, a measure of both spatial and temporal coordination, showed intermediate effects. The time course of learning in double support and step length was slower in children than in adults. Moreover, there was a significant negative correlation between the size of the initial asymmetry during early split-belt walking (called error) and the aftereffect for step length. Hence, children may have more difficulty learning when the errors are large. The findings further suggest that the mechanisms controlling temporal and spatial adaptation are different and mature at different times. PMID:21368001

  14. Intersegmental coordination of walking movements in stick insects.

    PubMed

    Ludwar, Björn Ch; Göritz, Marie L; Schmidt, Joachim

    2005-03-01

    Locomotion requires the coordination of movements across body segments, which in walking animals is expressed as gaits. We studied the underlying neural mechanisms of this coordination in a semi-intact walking preparation of the stick insect Carausius morosus. During walking of a single front leg on a treadmill, leg motoneuron (MN) activity tonically increased and became rhythmically modulated in the ipsilateral deafferented and deefferented mesothoracic (middle leg) ganglion. The pattern of modulation was correlated with the front leg cycle and specific for a given MN pool, although it was not consistent with functional leg movements for all MN pools. In an isolated preparation of a pair of ganglia, where one ganglion was made rhythmically active by application of pilocarpine, we found no evidence for coupling between segmental central pattern generators (CPGs) that could account for the modulation of MN activity observed in the semi-intact walking preparation. However, a third preparation provided evidence that signals from the front leg's femoral chordotonal organ (fCO) influenced activity of ipsilateral MNs in the adjacent mesothoracic ganglion. These intersegmental signals could be partially responsible for the observed MN activity modulation during front leg walking. While afferent signals from a single walking front leg modulate the activity of MNs in the adjacent segment, additional afferent signals, local or from contralateral or posterior legs, might be necessary to produce the functional motor pattern observed in freely walking animals.

  15. Design of a walking robot

    NASA Technical Reports Server (NTRS)

    Whittaker, William; Dowling, Kevin

    1994-01-01

    Carnegie Mellon University's Autonomous Planetary Exploration Program (APEX) is currently building the Daedalus robot; a system capable of performing extended autonomous planetary exploration missions. Extended autonomy is an important capability because the continued exploration of the Moon, Mars and other solid bodies within the solar system will probably be carried out by autonomous robotic systems. There are a number of reasons for this - the most important of which are the high cost of placing a man in space, the high risk associated with human exploration and communication delays that make teleoperation infeasible. The Daedalus robot represents an evolutionary approach to robot mechanism design and software system architecture. Daedalus incorporates key features from a number of predecessor systems. Using previously proven technologies, the Apex project endeavors to encompass all of the capabilities necessary for robust planetary exploration. The Ambler, a six-legged walking machine was developed by CMU for demonstration of technologies required for planetary exploration. In its five years of life, the Ambler project brought major breakthroughs in various areas of robotic technology. Significant progress was made in: mechanism and control, by introducing a novel gait pattern (circulating gait) and use of orthogonal legs; perception, by developing sophisticated algorithms for map building; and planning, by developing and implementing the Task Control Architecture to coordinate tasks and control complex system functions. The APEX project is the successor of the Ambler project.

  16. Design of a walking robot

    NASA Astrophysics Data System (ADS)

    Whittaker, William; Dowling, Kevin

    1994-03-01

    Carnegie Mellon University's Autonomous Planetary Exploration Program (APEX) is currently building the Daedalus robot; a system capable of performing extended autonomous planetary exploration missions. Extended autonomy is an important capability because the continued exploration of the Moon, Mars and other solid bodies within the solar system will probably be carried out by autonomous robotic systems. There are a number of reasons for this - the most important of which are the high cost of placing a man in space, the high risk associated with human exploration and communication delays that make teleoperation infeasible. The Daedalus robot represents an evolutionary approach to robot mechanism design and software system architecture. Daedalus incorporates key features from a number of predecessor systems. Using previously proven technologies, the Apex project endeavors to encompass all of the capabilities necessary for robust planetary exploration. The Ambler, a six-legged walking machine was developed by CMU for demonstration of technologies required for planetary exploration. In its five years of life, the Ambler project brought major breakthroughs in various areas of robotic technology. Significant progress was made in: mechanism and control, by introducing a novel gait pattern (circulating gait) and use of orthogonal legs; perception, by developing sophisticated algorithms for map building; and planning, by developing and implementing the Task Control Architecture to coordinate tasks and control complex system functions. The APEX project is the successor of the Ambler project.

  17. Quantum walks on quotient graphs

    SciTech Connect

    Krovi, Hari; Brun, Todd A.

    2007-06-15

    A discrete-time quantum walk on a graph {gamma} is the repeated application of a unitary evolution operator to a Hilbert space corresponding to the graph. If this unitary evolution operator has an associated group of symmetries, then for certain initial states the walk will be confined to a subspace of the original Hilbert space. Symmetries of the original graph, given by its automorphism group, can be inherited by the evolution operator. We show that a quantum walk confined to the subspace corresponding to this symmetry group can be seen as a different quantum walk on a smaller quotient graph. We give an explicit construction of the quotient graph for any subgroup H of the automorphism group and illustrate it with examples. The automorphisms of the quotient graph which are inherited from the original graph are the original automorphism group modulo the subgroup H used to construct it. The quotient graph is constructed by removing the symmetries of the subgroup H from the original graph. We then analyze the behavior of hitting times on quotient graphs. Hitting time is the average time it takes a walk to reach a given final vertex from a given initial vertex. It has been shown in earlier work [Phys. Rev. A 74, 042334 (2006)] that the hitting time for certain initial states of a quantum walks can be infinite, in contrast to classical random walks. We give a condition which determines whether the quotient graph has infinite hitting times given that they exist in the original graph. We apply this condition for the examples discussed and determine which quotient graphs have infinite hitting times. All known examples of quantum walks with hitting times which are short compared to classical random walks correspond to systems with quotient graphs much smaller than the original graph; we conjecture that the existence of a small quotient graph with finite hitting times is necessary for a walk to exhibit a quantum speedup.

  18. Diffraction of walking droplets

    NASA Astrophysics Data System (ADS)

    Harris, Daniel M.; Pucci, Giuseppe; Bush, John W. M.

    2014-11-01

    We present results from our revisitation of the experiment of a walking droplet passing through a single slit, originally investigated by Couder & Fort (PRL, 2006). On each passage, the walker's trajectory is deviated as a result of the spatial confinement of its guiding wave. We explore the role of the droplet size and the bath's vibration amplitude on both the dynamics and statistics. We find the behavior to be remarkably sensitive to these control parameters. A complex physical picture emerges. The authors gratefully acknowledge the financial support of the NSF through Grant CMMI-1333242, DMH through the NSF Graduate Research Fellowship Program, and GP through the Programma Operativo Regionale (POR) Calabria - FSE 2007/2013.

  19. Slow-walking inflation

    SciTech Connect

    Erdmenger, Johanna; Halter, Sebastian; Núñez, Carlos; Tasinato, Gianmassimo E-mail: s.halter@physik.uni-muenchen.de E-mail: gianmassimo.tasinato@port.ac.uk

    2013-01-01

    We propose a new model of slow-roll inflation in string cosmology, based on warped throat supergravity solutions displaying 'walking' dynamics, i.e. the coupling constant of the dual gauge theory slowly varies over a range of energy scales. The features of the throat geometry are sourced by a rich field content, given by the dilaton and RR and NS fluxes. By considering the motion of a D3-brane probe in this geometry, we are able to analytically calculate the brane potential in a physically interesting regime. This potential has an inflection point: in its proximity we realize a model of inflation lasting sixty e-foldings, and whose robust predictions are in agreement with current observations. We are also able to interpret some of the most interesting aspects of this scenario in terms of the properties of the QFT dual theory.

  20. Walking drawings and walking ability in children with cerebral palsy.

    PubMed

    Chong, Jimmy; Mackey, Anna H; Stott, N Susan; Broadbent, Elizabeth

    2013-06-01

    To investigate whether drawings of the self walking by children with cerebral palsy (CP) were associated with walking ability and illness perceptions. This was an exploratory study in 52 children with CP (M:F = 28:24), mean age 11.1 years (range 5-18), who were attending tertiary level outpatient clinics. Children were asked to draw a picture of themselves walking. Drawing size and content was used to investigate associations with clinical walk tests and children's own perceptions of their CP assessed using a CP version of the Brief Illness Perception Questionnaire. Larger drawings of the self were associated with less distance traveled, higher emotional responses to CP, and lower perceptions of pain or discomfort, independent of age. A larger self-to-overall drawing height ratio was related to walking less distance. Drawings of the self confined within buildings and the absence of other figures were also associated with reduced walking ability. Drawing size and content can reflect walking ability, as well as symptom perceptions and distress. Drawings may be useful for clinicians to use with children with cerebral palsy to aid discussion about their condition. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  1. Walking indoors, walking outdoors: an fMRI study

    PubMed Central

    Dalla Volta, Riccardo; Fasano, Fabrizio; Cerasa, Antonio; Mangone, Graziella; Quattrone, Aldo; Buccino, Giovanni

    2015-01-01

    An observation/execution matching system for walking has not been assessed yet. The present fMRI study was aimed at assessing whether, as for object-directed actions, an observation/execution matching system is active for walking and whether the spatial context of walking (open or narrow space) recruits different neural correlates. Two experimental conditions were employed. In the execution condition, while being scanned, participants performed walking on a rolling cylinder located just outside the scanner. The same action was performed also while observing a video presenting either an open space (a country field) or a narrow space (a corridor). In the observation condition, participants observed a video presenting an individual walking on the same cylinder on which the actual action was executed, the open space video and the narrow space video, respectively. Results showed common bilateral activations in the dorsal premotor/supplementary motor areas and in the posterior parietal lobe for both execution and observation of walking, thus supporting a matching system for this action. Moreover, specific sectors of the occipital–temporal cortex and the middle temporal gyrus were consistently active when processing a narrow space versus an open one, thus suggesting their involvement in the visuo-motor transformation required when walking in a narrow space. We forward that the present findings may have implications for rehabilitation of gait and sport training. PMID:26483745

  2. Dog-walking: motivation for adherence to a walking program.

    PubMed

    Johnson, Rebecca A; Meadows, Richard L

    2010-11-01

    Healthy People 2010 cited walking as a major health indicator; however, adherence is challenging, especially among those with multiple chronic illnesses. Studies suggest that walking one's own dog may motivate adherence. However, no research has studied whether walking a "loaner" dog may facilitate adherence. Using a pretest-posttest design, the authors studied adherence to and outcomes of a graduated walking program when 26 public housing residents walked certified therapy dogs with a handler. Participants walked 20 minutes, 5 days/week, for 26 or 50 weeks. In all, 13 participants in the 50-week group had a mean adherence rate of 72% and weight loss of 14.4 pounds (p = .013). Thirteen participants in the 26-week group had a mean adherence rate of 52% and weight loss of 5 pounds (nonsignificant). Participants' most commonly stated reason for adherence was that the dogs "need us to walk them." Commitment to a dog that is not one's own may effectively facilitate physical activity.

  3. Reduced Gravity Walking Simulator

    NASA Technical Reports Server (NTRS)

    1963-01-01

    A test subject being suited up for studies on the Reduced Gravity Walking Simulator located in the hanger at Langley Research Center. The initial version of this simulator was located inside the hanger. Later a larger version would be located at the Lunar Landing Facility. The purpose of this simulator was to study the subject while walking, jumping or running. Researchers conducted studies of various factors such as fatigue limit, energy expenditure, and speed of locomotion. Francis B. Smith wrote in his paper 'Simulators For Manned Space Research,' 'I would like to conclude this talk with a discussion of a device for simulating lunar gravity which is very effective and yet which is so simple that its cost is in the order of a few thousand dollars at most, rather than hundreds of thousands. With a little ingenuity, one could almost build this type simulator in his backyard for children to play on. The principle is ...if a test subject is suspended in a sling so that his body axis makes an angle of 9 1/2 degrees with the horizontal and if he then 'stands' on a platform perpendicular to his body axis, the component of the earth's gravity forcing him toward the platform is one times the sine of 9 1/2 degrees or approximately 1/6 of the earth's normal gravity field. That is, a 180 pound astronaut 'standing' on the platform would exert a force of only 30 pounds - the same as if he were standing upright on the lunar surface.' Published in James R. Hansen, Spaceflight Revolution: NASA Langley Research Center From Sputnik to Apollo, NASA SP-4308; Francis B. Smith, 'Simulators For Manned Space Research,' Paper for 1966 IEEE International Convention, New York, NY, March 21-25, 1966.

  4. Excitability changes in intracortical neural circuits induced by differentially controlled walking patterns.

    PubMed

    Ito, Tomotaka; Tsubahara, Akio; Shinkoda, Koichi; Yoshimura, Yosuke; Kobara, Kenichi; Osaka, Hiroshi

    2015-01-01

    Our previous single-pulse transcranial magnetic stimulation (TMS) study revealed that excitability in the motor cortex can be altered by conscious control of walking relative to less conscious normal walking. However, substantial elements and underlying mechanisms for inducing walking-related cortical plasticity are still unknown. Hence, in this study we aimed to examine the characteristics of electromyographic (EMG) recordings obtained during different walking conditions, namely, symmetrical walking (SW), asymmetrical walking 1 (AW1), and asymmetrical walking 2 (AW2), with left to right stance duration ratios of 1:1, 1:2, and 2:1, respectively. Furthermore, we investigated the influence of three types of walking control on subsequent changes in the intracortical neural circuits. Prior to each type of 7-min walking task, EMG analyses of the left tibialis anterior (TA) and soleus (SOL) muscles during walking were performed following approximately 3 min of preparative walking. Paired-pulse TMS was used to measure short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the left TA and SOL at baseline, immediately after the 7-min walking task, and 30 min post-task. EMG activity in the TA was significantly increased during AW1 and AW2 compared to during SW, whereas a significant difference in EMG activity of the SOL was observed only between AW1 and AW2. As for intracortical excitability, there was a significant alteration in SICI in the TA between SW and AW1, but not between SW and AW2. For the same amount of walking exercise, we found that the different methods used to control walking patterns induced different excitability changes in SICI. Our research shows that activation patterns associated with controlled leg muscles can alter post-exercise excitability in intracortical circuits. Therefore, how leg muscles are activated in a clinical setting could influence the outcome of walking in patients with stroke.

  5. Excitability Changes in Intracortical Neural Circuits Induced by Differentially Controlled Walking Patterns

    PubMed Central

    Ito, Tomotaka; Tsubahara, Akio; Shinkoda, Koichi; Yoshimura, Yosuke; Kobara, Kenichi; Osaka, Hiroshi

    2015-01-01

    Our previous single-pulse transcranial magnetic stimulation (TMS) study revealed that excitability in the motor cortex can be altered by conscious control of walking relative to less conscious normal walking. However, substantial elements and underlying mechanisms for inducing walking-related cortical plasticity are still unknown. Hence, in this study we aimed to examine the characteristics of electromyographic (EMG) recordings obtained during different walking conditions, namely, symmetrical walking (SW), asymmetrical walking 1 (AW1), and asymmetrical walking 2 (AW2), with left to right stance duration ratios of 1:1, 1:2, and 2:1, respectively. Furthermore, we investigated the influence of three types of walking control on subsequent changes in the intracortical neural circuits. Prior to each type of 7-min walking task, EMG analyses of the left tibialis anterior (TA) and soleus (SOL) muscles during walking were performed following approximately 3 min of preparative walking. Paired-pulse TMS was used to measure short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the left TA and SOL at baseline, immediately after the 7-min walking task, and 30 min post-task. EMG activity in the TA was significantly increased during AW1 and AW2 compared to during SW, whereas a significant difference in EMG activity of the SOL was observed only between AW1 and AW2. As for intracortical excitability, there was a significant alteration in SICI in the TA between SW and AW1, but not between SW and AW2. For the same amount of walking exercise, we found that the different methods used to control walking patterns induced different excitability changes in SICI. Our research shows that activation patterns associated with controlled leg muscles can alter post-exercise excitability in intracortical circuits. Therefore, how leg muscles are activated in a clinical setting could influence the outcome of walking in patients with stroke. PMID:25688972

  6. The mass-specific energy cost of human walking is set by stature

    USDA-ARS?s Scientific Manuscript database

    The metabolic and mechanical requirements of walking are considered to be of fundamental importance to the health, physiological function and even the evolution of modern humans. Although walking energy expenditure and gait mechanics are clearly linked, a direct quantitative relationship has not eme...

  7. Hairless mutation: a driving force of humanization from a human–ape common ancestor by enforcing upright walking while holding a baby with both hands

    PubMed Central

    Sutou, Shizuyo

    2012-01-01

    Three major characteristics distinguish humans from other primates: bipedality, practical nakedness, and the family as a social unit. A hairless mutation introduced into the chimpanzee/human last common ancestor (CLCA) 6 million years ago (Mya) diverged hairless human and hairy chimpanzee lineages. All primates except humans can carry their babies without using their hands. A hairless mother would be forced to stand and walk upright. Her activities would be markedly limited. The male partner would have to collect food and carry it to her by hand to keep her and their baby from starving; irresponsible and selfish males could not have left their offspring. The mother would have sexually accepted her partner at any time as a reward for food. Sexual relations irrespective of estrus cycles might have strengthened the pair bond. Molecular and paleontological dating indicates that CLCA existed 6 Mya, and early hominin fossils show that they were bipeds, indicating that humanization from CLCA occurred rapidly. A single mutation in animals with scalp hair is known to induce hairless phenotype (ectodermal dysplasia). Bipedalism and hairlessness are disadvantageous traits; only those who could survive trials and tribulations in cooperation with family members must have been able to evolve as humans. PMID:22404045

  8. Visual control of walking velocity.

    PubMed

    François, Matthieu; Morice, Antoine H P; Bootsma, Reinoud J; Montagne, Gilles

    2011-06-01

    Even if optical correlates of self-motion velocity have already been identified, their contribution to the control of displacement velocity remains to be established. In this study, we used a virtual reality set-up coupled to a treadmill to test the role of both Global Optic Flow Rate (GOFR) and Edge Rate (ER) in the regulation of walking velocity. Participants were required to walk at a constant velocity, corresponding to their preferred walking velocity, while eye height and texture density were manipulated. This manipulation perturbed the natural relationship between the actual walking velocity and its optical specification by GOFR and ER, respectively. Results revealed that both these sources of information are indeed used by participants to control walking speed, as demonstrated by a slowing down of actual walking velocity when the optical specification of velocity by either GOFR or ER gives rise to an overestimation of actual velocity, and vice versa. Gait analyses showed that these walking velocity adjustments result from simultaneous adaptations in both step length and step duration. The role of visual information in the control of self-motion velocity is discussed in relation with other factors.

  9. Optic flow is calibrated to walking effort.

    PubMed

    Zadra, Jonathan R; Proffitt, Dennis R

    2016-10-01

    Through experience, people learn that a given magnitude of walking produces an associated magnitude of optic flow. Artificially altering this relationship has both behavioral and perceptual consequences: walking on a treadmill results in zero translational optic flow and causes people to subsequently drift forward when attempting to walk in place while blindfolded (they have learned that forward walking is required to remain stationary). Similarly, after walking on a treadmill people perceive the walking distance to targets to be greater (they have recalibrated the magnitude of walking required to reach the target). While the measurement unit for walking magnitude in this relationship has been treated as walking speed (stride length * [steps / time]), recent experiments suggest that walkable distances may instead be measured in bioenergetic units (i.e., the magnitude of energy required to produce a given magnitude of optic flow). In the first experiment, zero translational optic flow was paired with a constant walking speed, and walking energy was manipulated by varying the incline of the treadmill. Participants who walked on an inclined treadmill drifted farther while attempting to walk in place than participants who walked on a flat treadmill. A follow-up experiment presented optic flow via an immersive virtual environment, and no difference between flat and inclined treadmill walking was found, thereby showing that the effect found in the first experiment was not an artifact of biomechanical differences associated with flat versus inclined treadmill walking. The results support the hypothesis that walking magnitude is scaled by bioenergetic units.

  10. Constraining walking and custodial technicolor

    SciTech Connect

    Foadi, Roshan; Frandsen, Mads T.; Sannino, Francesco

    2008-05-01

    We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level - custodial technicolor - and argue that these models cannot emerge from walking-type dynamics. We suggest that it is possible to have a very light spin-one axial (vector) boson. However, in the walking dynamics the associated vector boson is heavy while it is degenerate with the axial in custodial technicolor.

  11. Big power from walking

    NASA Astrophysics Data System (ADS)

    Illenberger, Patrin K.; Madawala, Udaya K.; Anderson, Iain A.

    2016-04-01

    Dielectric Elastomer Generators (DEG) offer an opportunity to capture the energy otherwise wasted from human motion. By integrating a DEG into the heel of standard footwear, it is possible to harness this energy to power portable devices. DEGs require substantial auxiliary systems which are commonly large, heavy and inefficient. A unique challenge for these low power generators is the combination of high voltage and low current. A void exists in the semiconductor market for devices that can meet these requirements. Until these become available, existing devices must be used in an innovative way to produce an effective DEG system. Existing systems such as the Bi-Directional Flyback (BDFB) and Self Priming Circuit (SPC) are an excellent example of this. The BDFB allows full charging and discharging of the DEG, improving power gained. The SPC allows fully passive voltage boosting, removing the priming source and simplifying the electronics. This paper outlines the drawbacks and benefits of active and passive electronic solutions for maximizing power from walking.

  12. Walking Shoes: Features and Fit

    MedlinePlus

    ... also be fairly lightweight and provide good shock absorption. But not all walking shoes are created equal. ... to compensate for your lack of natural shock absorption. A curved last also may help in some ...

  13. Adaptive walk on complex networks.

    PubMed

    Campos, Paulo R A; Moreira, F G Brady

    2005-06-01

    We investigate the properties of adaptive walks on an uncorrelated fitness landscape which is established in sequence spaces of complex structure. In particular, we perform numerical simulations of adaptive walks on random graphs and scale-free networks. For the former, we also derive some analytical approximations for the density of local optima of the fitness landscape and the mean length walk. We compare our results with those obtained for regular lattices. We obtain that the density of local optima decreases as 1/z, where z is the mean connectivity, for all networks we have investigated. In random graphs, the mean length walk L reaches the asymptotic value e - 1 for large z, which corresponds to the result for regular networks. Although we could not find an exact estimate, we derive an underestimated value for L. Unlike random graphs, scale-free networks show an upper asymptotic value of L.

  14. Base Station Walk-Back

    NASA Image and Video Library

    Train to improve your lung, heart, and other muscle endurance while walking a progressive, measured distance. The Train Like an Astronaut project uses the excitement of exploration to challenge stu...

  15. Quantum snake walk on graphs

    SciTech Connect

    Rosmanis, Ansis

    2011-02-15

    I introduce a continuous-time quantum walk on graphs called the quantum snake walk, the basis states of which are fixed-length paths (snakes) in the underlying graph. First, I analyze the quantum snake walk on the line, and I show that, even though most states stay localized throughout the evolution, there are specific states that most likely move on the line as wave packets with momentum inversely proportional to the length of the snake. Next, I discuss how an algorithm based on the quantum snake walk might potentially be able to solve an extended version of the glued trees problem, which asks to find a path connecting both roots of the glued trees graph. To the best of my knowledge, no efficient quantum algorithm solving this problem is known yet.

  16. The Effects of Walking Behavior on Mood.

    ERIC Educational Resources Information Center

    Snodgrass, Sara E.; And Others

    Past research has shown that the way one walks reflects one's personality traits and mood states. A study was conducted to examine whether the way one walks can reciprocally affect one's mood. The study tested the hypothesis that walking vigorously would cause a person to feel happier, and that a shuffling walk would cause a person to feel more…

  17. 10 CFR 429.53 - Walk-in coolers and walk-in freezers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Walk-in coolers and walk-in freezers. 429.53 Section 429... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.53 Walk-in coolers and walk... are applicable to walk-in coolers and freezers; and (2) (b) Certification reports. (1) Except...

  18. Lévy random walks on multiplex networks

    PubMed Central

    Guo, Quantong; Cozzo, Emanuele; Zheng, Zhiming; Moreno, Yamir

    2016-01-01

    Random walks constitute a fundamental mechanism for many dynamics taking place on complex networks. Besides, as a more realistic description of our society, multiplex networks have been receiving a growing interest, as well as the dynamical processes that occur on top of them. Here, inspired by one specific model of random walks that seems to be ubiquitous across many scientific fields, the Lévy flight, we study a new navigation strategy on top of multiplex networks. Capitalizing on spectral graph and stochastic matrix theories, we derive analytical expressions for the mean first passage time and the average time to reach a node on these networks. Moreover, we also explore the efficiency of Lévy random walks, which we found to be very different as compared to the single layer scenario, accounting for the structure and dynamics inherent to the multiplex network. Finally, by comparing with some other important random walk processes defined on multiplex networks, we find that in some region of the parameters, a Lévy random walk is the most efficient strategy. Our results give us a deeper understanding of Lévy random walks and show the importance of considering the topological structure of multiplex networks when trying to find efficient navigation strategies. PMID:27892508

  19. Lévy random walks on multiplex networks

    NASA Astrophysics Data System (ADS)

    Guo, Quantong; Cozzo, Emanuele; Zheng, Zhiming; Moreno, Yamir

    2016-11-01

    Random walks constitute a fundamental mechanism for many dynamics taking place on complex networks. Besides, as a more realistic description of our society, multiplex networks have been receiving a growing interest, as well as the dynamical processes that occur on top of them. Here, inspired by one specific model of random walks that seems to be ubiquitous across many scientific fields, the Lévy flight, we study a new navigation strategy on top of multiplex networks. Capitalizing on spectral graph and stochastic matrix theories, we derive analytical expressions for the mean first passage time and the average time to reach a node on these networks. Moreover, we also explore the efficiency of Lévy random walks, which we found to be very different as compared to the single layer scenario, accounting for the structure and dynamics inherent to the multiplex network. Finally, by comparing with some other important random walk processes defined on multiplex networks, we find that in some region of the parameters, a Lévy random walk is the most efficient strategy. Our results give us a deeper understanding of Lévy random walks and show the importance of considering the topological structure of multiplex networks when trying to find efficient navigation strategies.

  20. Modular control during incline and level walking in humans.

    PubMed

    Janshen, Lars; Santuz, Alessandro; Ekizos, Antonis; Arampatzis, Adamantios

    2017-03-01

    The neuromuscular control of human movement can be described by a set of muscle synergies factorized from myoelectric signals. There is some evidence that the selection, activation and flexible combination of these basic activation patterns are of a neural origin. We investigated the muscle synergies during incline and level walking to evaluate changes in the modular organization of neuromuscular control related to changes in the mechanical demands. Our results revealed five fundamental (not further factorizable) synergies for both walking conditions but with different frequencies of appearance of the respective synergies during incline compared with level walking. Low similarities across conditions were observed in the timing of the activation patterns (motor primitives) and the weightings of the muscles within the respective elements (motor modules) for the synergies associated with the touchdown, mid-stance and early push-off phase. The changes in neuromuscular control could be attributed to changes in the mechanical demands in support, propulsion and medio-lateral stabilization of the body during incline compared with level walking. Our findings provide further evidence that the central nervous system flexibly uses a consistent set of neural control elements with a flexible temporal recruitment and modifications of the relative muscle weightings within each element to provide stable locomotion under varying mechanical demands during walking.

  1. Autonomous exoskeleton reduces metabolic cost of human walking.

    PubMed

    Mooney, Luke M; Rouse, Elliott J; Herr, Hugh M

    2014-11-03

    Passive exoskeletons that assist with human locomotion are often lightweight and compact, but are unable to provide net mechanical power to the exoskeletal wearer. In contrast, powered exoskeletons often provide biologically appropriate levels of mechanical power, but the size and mass of their actuator/power source designs often lead to heavy and unwieldy devices. In this study, we extend the design and evaluation of a lightweight and powerful autonomous exoskeleton evaluated for loaded walking in (J Neuroeng Rehab 11:80, 2014) to the case of unloaded walking conditions. The metabolic energy consumption of seven study participants (85 ± 12 kg body mass) was measured while walking on a level treadmill at 1.4 m/s. Testing conditions included not wearing the exoskeleton and wearing the exoskeleton, in both powered and unpowered modes. When averaged across the gait cycle, the autonomous exoskeleton applied a mean positive mechanical power of 26 ± 1 W (13 W per ankle) with 2.12 kg of added exoskeletal foot-shank mass (1.06 kg per leg). Use of the leg exoskeleton significantly reduced the metabolic cost of walking by 35 ± 13 W, which was an improvement of 10 ± 3% (p = 0.023) relative to the control condition of not wearing the exoskeleton. The results of this study highlight the advantages of developing lightweight and powerful exoskeletons that can comfortably assist the body during walking.

  2. Walking on a moving surface: energy-optimal walking motions on a shaky bridge and a shaking treadmill can reduce energy costs below normal

    PubMed Central

    Joshi, Varun; Srinivasan, Manoj

    2015-01-01

    Understanding how humans walk on a surface that can move might provide insights into, for instance, whether walking humans prioritize energy use or stability. Here, motivated by the famous human-driven oscillations observed in the London Millennium Bridge, we introduce a minimal mathematical model of a biped, walking on a platform (bridge or treadmill) capable of lateral movement. This biped model consists of a point-mass upper body with legs that can exert force and perform mechanical work on the upper body. Using numerical optimization, we obtain energy-optimal walking motions for this biped, deriving the periodic body and platform motions that minimize a simple metabolic energy cost. When the platform has an externally imposed sinusoidal displacement of appropriate frequency and amplitude, we predict that body motion entrained to platform motion consumes less energy than walking on a fixed surface. When the platform has finite inertia, a mass- spring-damper with similar parameters to the Millennium Bridge, we show that the optimal biped walking motion sustains a large lateral platform oscillation when sufficiently many people walk on the bridge. Here, the biped model reduces walking metabolic cost by storing and recovering energy from the platform, demonstrating energy benefits for two features observed for walking on the Millennium Bridge: crowd synchrony and large lateral oscillations. PMID:25663810

  3. Walking on a moving surface: energy-optimal walking motions on a shaky bridge and a shaking treadmill can reduce energy costs below normal.

    PubMed

    Joshi, Varun; Srinivasan, Manoj

    2015-02-08

    Understanding how humans walk on a surface that can move might provide insights into, for instance, whether walking humans prioritize energy use or stability. Here, motivated by the famous human-driven oscillations observed in the London Millennium Bridge, we introduce a minimal mathematical model of a biped, walking on a platform (bridge or treadmill) capable of lateral movement. This biped model consists of a point-mass upper body with legs that can exert force and perform mechanical work on the upper body. Using numerical optimization, we obtain energy-optimal walking motions for this biped, deriving the periodic body and platform motions that minimize a simple metabolic energy cost. When the platform has an externally imposed sinusoidal displacement of appropriate frequency and amplitude, we predict that body motion entrained to platform motion consumes less energy than walking on a fixed surface. When the platform has finite inertia, a mass- spring-damper with similar parameters to the Millennium Bridge, we show that the optimal biped walking motion sustains a large lateral platform oscillation when sufficiently many people walk on the bridge. Here, the biped model reduces walking metabolic cost by storing and recovering energy from the platform, demonstrating energy benefits for two features observed for walking on the Millennium Bridge: crowd synchrony and large lateral oscillations.

  4. Walking strategies of visually impaired people on trapezoidal- and sinusoidal-section tactile groundsurface indicators.

    PubMed

    Ranavolo, A; Conte, C; Iavicoli, S; Serrao, M; Silvetti, A; Sandrini, G; Pierelli, F; Draicchio, F

    2011-03-01

    The visual system in walking serves to perceive feedback or feed-forward signals. Therefore, visually impaired persons (VIP) have biased motor control mechanisms. The use of leading indicators (LIs) and long canes helps to improve their walking efficiency. The aims of this study were to compare the walking efficiency of VIP on trapezoidal- and sinusoidal-section LIs using an optoelectronic motion analysis system. VIP displayed a significantly longer stance phase, a shorter swing phase and shorter step and stride lengths when they walked on the sinusoidal LI than when they walked on the trapezoidal LI. Compared with the trapezoidal LI, VIP walking on the sinusoidal LI displayed significantly lower joint ranges of motion. The centre of mass lateral displacement was wider for VIP walking on the sinusoidal LI than on the trapezoidal LI. Some significant differences were also found in sighted persons walking on both LIs. In conclusion, the trapezoidal shape enabled visually impaired subjects to walk more efficiently, whereas the sinusoidal shape caused dynamic balance problems. STATEMENT OF RELEVANCE: These findings suggest that VIP can walk more efficiently, with a lower risk of falls, on trapezoidal-section than on sinusoidal-section LIs. These results should be considered when choosing the most appropriate ground tactile surface indicators for widespread use.

  5. Robotic gait analysis of bipedal treadmill stepping by spinal contused rats: characterization of intrinsic recovery and comparison with BBB.

    PubMed

    Nessler, Jeff A; De Leon, Ray D; Sharp, Kelli; Kwak, Eugene; Minakata, Koyiro; Reinkensmeyer, David J

    2006-06-01

    There is a critical need to develop objective, quantitative techniques to assess motor function after spinal cord injury. Here, we assess the ability of a recently developed robotic device (the "rat stepper") to characterize locomotor impairment following contusion injury in rats. In particular, we analyzed how the kinematic features of hindlimb movement during bipedal, weight-supported treadmill stepping change following contusion, and whether these changes correlate with the recovery of open field locomotion. Female, Sprague-Dawley rats (n=29, 8 weeks of age) received mid thoracic contusion injuries of differing severities (11 mild, nine moderate, nine severe, and four sham). In a first experiment, 16 of the animals were evaluated weekly for 12 weeks using the robotic stepping device. In a second experiment, 17 of the animals were evaluated every other day for 4 weeks. The contused animals recovered open field locomotion based on the Basso, Beattie, and Bresnahan Scale (BBB) analysis, with most of the recovery occurring by 4 weeks post-injury. Analysis of 14 robotic measures of stepping revealed that several measures improved significantly during the same 4 weeks: swing velocity, step height, step length, hindlimb coordination, and the ability to support body weight. These measures were also significantly correlated with the BBB score. The number of steps taken during testing was not directly related to intrinsic recovery or correlated to the BBB score. These results suggest that it is the quality of weight-supported steps, rather than the quantity, that best reflects locomotor recovery after contusion injury, and that the quality of these steps is determined by the integrity of extensor, flexor, and bilateral coordination pathways. Thus, by measuring only a few weight-supported steps with motion capture, a sensitive, valid measure of locomotor recovery following contusion injury can be obtained across a broad range of impairment levels.

  6. Comparison of forward walking and backward walking in stroke hemiplegia patients focusing on the paretic side

    PubMed Central

    Makino, Misato; Takami, Akiyoshi; Oda, Atsushi

    2017-01-01

    [Purpose] To investigate the features of backward walking in stroke patients with hemiplegia by focusing on the joint movements and moments of the paretic side, walking speed, stride length, and cadence. [Subjects and Methods] Nine stroke patients performed forward walking and backward walking along a 5-m walkway. Walking speed and stride length were self-selected. Movements were measured using a three-dimensional motion analysis system and a force plate. One walking cycle of the paretic side was analyzed. [Results] Walking speed, stride length, and cadence were significantly lower in backward walking than in forward walking. Peak hip extension was significantly lower in backward walking and peak hip flexion moment, knee extension moment, and ankle dorsiflexion and plantar flexion moments were lower in backward walking. [Conclusion] Unlike forward walking, backward walking requires conscious hip joint extension. Conscious extension of the hip joint is hard for stroke patients with hemiplegia. Therefore, the range of hip joint movement declined in backward walking, and walking speed and stride length also declined. The peak ankle plantar flexion moment was significantly lower in backward walking than in forward walking, and it was hard to generate propulsion power in backward walking. These difficulties also affected the walking speed. PMID:28265136

  7. Biomechanics and energetics of walking on uneven terrain

    PubMed Central

    Voloshina, Alexandra S.; Kuo, Arthur D.; Daley, Monica A.; Ferris, Daniel P.

    2013-01-01

    SUMMARY Walking on uneven terrain is more energetically costly than walking on smooth ground, but the biomechanical factors that contribute to this increase are unknown. To identify possible factors, we constructed an uneven terrain treadmill that allowed us to record biomechanical, electromyographic and metabolic energetics data from human subjects. We hypothesized that walking on uneven terrain would increase step width and length variability, joint mechanical work and muscle co-activation compared with walking on smooth terrain. We tested healthy subjects (N=11) walking at 1.0 m s−1, and found that, when walking on uneven terrain with up to 2.5 cm variation, subjects decreased their step length by 4% and did not significantly change their step width, while both step length and width variability increased significantly (22 and 36%, respectively; P<0.05). Uneven terrain walking caused a 28 and 62% increase in positive knee and hip work, respectively, and a 26% greater magnitude of negative knee work (0.0106, 0.1078 and 0.0425 J kg−1, respectively; P<0.05). Mean muscle activity increased in seven muscles in the lower leg and thigh (P<0.05). These changes caused overall net metabolic energy expenditure to increase by 0.73 W kg−1 (28%; P<0.0001). Much of that increase could be explained by the increased mechanical work observed at the knee and hip. Greater muscle co-activation could also contribute to increased energetic cost but to unknown degree. The findings provide insight into how lower limb muscles are used differently for natural terrain compared with laboratory conditions. PMID:23913951

  8. Biomechanics and energetics of walking on uneven terrain.

    PubMed

    Voloshina, Alexandra S; Kuo, Arthur D; Daley, Monica A; Ferris, Daniel P

    2013-11-01

    Walking on uneven terrain is more energetically costly than walking on smooth ground, but the biomechanical factors that contribute to this increase are unknown. To identify possible factors, we constructed an uneven terrain treadmill that allowed us to record biomechanical, electromyographic and metabolic energetics data from human subjects. We hypothesized that walking on uneven terrain would increase step width and length variability, joint mechanical work and muscle co-activation compared with walking on smooth terrain. We tested healthy subjects (N=11) walking at 1.0 m s(-1), and found that, when walking on uneven terrain with up to 2.5 cm variation, subjects decreased their step length by 4% and did not significantly change their step width, while both step length and width variability increased significantly (22 and 36%, respectively; P<0.05). Uneven terrain walking caused a 28 and 62% increase in positive knee and hip work, respectively, and a 26% greater magnitude of negative knee work (0.0106, 0.1078 and 0.0425 J kg(-1), respectively; P<0.05). Mean muscle activity increased in seven muscles in the lower leg and thigh (P<0.05). These changes caused overall net metabolic energy expenditure to increase by 0.73 W kg(-1) (28%; P<0.0001). Much of that increase could be explained by the increased mechanical work observed at the knee and hip. Greater muscle co-activation could also contribute to increased energetic cost but to unknown degree. The findings provide insight into how lower limb muscles are used differently for natural terrain compared with laboratory conditions.

  9. Walking robot: A design project for undergraduate students

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The objective of the University of Maryland walking robot project was to design, analyze, assemble, and test an intelligent, mobile, and terrain-adaptive system. The robot incorporates existing technologies in novel ways. The legs emulate the walking path of a human by an innovative modification of a crank-and-rocker mechanism. The body consists of two tripod frames connected by a turning mechanism. The two sets of three legs are mounted so as to allow the robot to walk with stability in its own footsteps. The computer uses a modular hardware design and distributed processing. Dual-port RAM is used to allow communication between a supervisory personal computer and seven microcontrollers. The microcontrollers provide low-level control for the motors and relieve the processing burden on the PC.

  10. Walking robot: A design project for undergraduate students

    NASA Astrophysics Data System (ADS)

    The objective of the University of Maryland walking robot project was to design, analyze, assemble, and test an intelligent, mobile, and terrain-adaptive system. The robot incorporates existing technologies in novel ways. The legs emulate the walking path of a human by an innovative modification of a crank-and-rocker mechanism. The body consists of two tripod frames connected by a turning mechanism. The two sets of three legs are mounted so as to allow the robot to walk with stability in its own footsteps. The computer uses a modular hardware design and distributed processing. Dual-port RAM is used to allow communication between a supervisory personal computer and seven microcontrollers. The microcontrollers provide low-level control for the motors and relieve the processing burden on the PC.

  11. [The use of bi-pedical rotatory door muscle-skin flap reconstruction in extended partial laryngectomy for late (T3 and T4) glottic cancer].

    PubMed

    Zhao, S; Sun, X; Lu, S

    1998-12-01

    The purpose is to radical treatment for late glottic cancer by surgery, to restore the essential function of the larynx, 62 patients of late (T3 and T4) glottic cancer were treated by extended vertical partial and subtotal laryngectomy. At the same time, an appropriate method of reconstruction of laryngeal function by bi-pedical rotatory door muscle-skin flap was presented. The decannulation rate was 87.1% and 85.0% cases enjoyed satisfactory voice. All cases resumed normal mouth-food-taking. The conclusion is that selective treated with extended partial laryngectomy is effective for T3 and T4 glottic cancer.

  12. Bionic ankle-foot prosthesis normalizes walking gait for persons with leg amputation.

    PubMed

    Herr, Hugh M; Grabowski, Alena M

    2012-02-07

    Over time, leg prostheses have improved in design, but have been incapable of actively adapting to different walking velocities in a manner comparable to a biological limb. People with a leg amputation using such commercially available passive-elastic prostheses require significantly more metabolic energy to walk at the same velocities, prefer to walk slower and have abnormal biomechanics compared with non-amputees. A bionic prosthesis has been developed that emulates the function of a biological ankle during level-ground walking, specifically providing the net positive work required for a range of walking velocities. We compared metabolic energy costs, preferred velocities and biomechanical patterns of seven people with a unilateral transtibial amputation using the bionic prosthesis and using their own passive-elastic prosthesis to those of seven non-amputees during level-ground walking. Compared with using a passive-elastic prosthesis, using the bionic prosthesis decreased metabolic cost by 8 per cent, increased trailing prosthetic leg mechanical work by 57 per cent and decreased the leading biological leg mechanical work by 10 per cent, on average, across walking velocities of 0.75-1.75 m s(-1) and increased preferred walking velocity by 23 per cent. Using the bionic prosthesis resulted in metabolic energy costs, preferred walking velocities and biomechanical patterns that were not significantly different from people without an amputation.

  13. Effect of walking speed in heart failure patients and heart transplant patients.

    PubMed

    Bona, Renata L; Bonezi, Artur; da Silva, Paula Figueiredo; Biancardi, Carlo M; de Souza Castro, Flávio Antônio; Clausel, Nadine Oliveira

    2017-02-01

    Chronic heart failure patients present higher cost of transport and some changes in pattern of walking, but the same aspects have not yet been investigated in heart transplant patients. The aim of this study was to investigate both metabolic and mechanicals parameters, at five different walking speeds on treadmill, in chronic heart failure and heart transplant patients. Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Tridimensional kinematics data and oxygen uptake were collected simultaneously. In both experimental groups the self-selected walking speed was lower than in controls, and lower than the expected optimal walking speed. At that speed all groups showed the best ventilatory efficiency. On contrary, chronic heart failure and heart transplant patients reached the minimum cost of transport and the maximum recovery at greater speeds than the self-selected walking speed. Their mechanical efficiency was lower than in controls, while their metabolic cost and mechanical work were on average larger. We conclude that actions, like a physical training, that could increase the self-selected walking speed in these patients, could also increase their economy and optimize the mechanical parameters of walking. We propose a rehabilitation index, based on the theoretical optimal walking speed, to measure the improvements during a physical rehabilitation therapy. These results have an important clinical relevance and can help to improve the quality of life of heart failure and transplant patients. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Research on Walking Wheel Slippage Control of Live Inspection Robot

    NASA Astrophysics Data System (ADS)

    Yan, Yu; Liu, Xiaqing; Guo, Hao; Li, Jinliang; Liu, Lanlan

    2017-07-01

    To solve the problem of walking wheel slippage of a live inspection robot during walking or climbing, this paper analyzes the climbing capacity of the robot with a statics method, designs a pressing wheel mechanism, and presents a method of indirectly identifying walking wheel slippage by reading speed of the pressing wheel due to the fact that the linear speed of the pressing wheel and the walking wheel at the contract point is the same; and finds that the slippage state can not be controlled through accurate mathematical models after identifying the slippage state, whereas slippage can be controlled with fuzzy control. The experiment results indicate that due to design of the pressing wheel mechanism, friction force of the walking wheel is increased, and the climbing capability of the robot is improved. Within the range of climbing capability of the robot, gradient is the key factor that has influence on slippage of robot, and slippage can be effectively eliminated through the fuzzy control method proposed in this paper.

  15. Stability and Control of Constrained Three-Dimensional Robotic Systems with Application to Bipedal Postural Movements

    NASA Astrophysics Data System (ADS)

    Kallel, Hichem

    Three classes of postural adjustments are investigated with the view of a better understanding of the control mechanisms involved in human movement. The control mechanisms and responses of human or computer models to deliberately induced disturbances in postural adjustments are the focus of this dissertation. The classes of postural adjustments are automatic adjustments, (i.e. adjustments not involving voluntary deliberate movement), adjustments involving imposition of constraints for the purpose of maintaining support forces, and adjustments involving violation and imposition of constraints for the purpose of maintaining balance, (i.e. taking one or more steps). For each class, based on the physiological attributes of the control mechanisms in human movements, control strategies are developed to synthesize the desired postural response. The control strategies involve position and velocity feedback control, on line relegation control, and pre-stored trajectory control. Stability analysis for constrained and unconstrained maneuvers is carried out based on Lyapunov stability theorems. The analysis is based on multi-segment biped robots. Depending on the class of postural adjustments, different biped models are developed. An eight-segment three dimensional biped model is formulated for the study of automatic adjustments and adjustments for balance. For the study of adjustments for support, a four segment lateral biped model is considered. Muscle synergies in automatic adjustments are analyzed based on a three link six muscle system. The muscle synergies considered involve minimal muscle number and muscle co-activation. The role of active and passive feedback in these automatic adjustments is investigated based on the specified stiffness and damping of the segments. The effectiveness of the control strategies and the role of muscle synergies in automatic adjustments are demonstrated by a number of digital computer simulations.

  16. Walking on ballast impacts balance.

    PubMed

    Wade, Chip; Garner, John C; Redfern, Mark S; Andres, Robert O

    2014-01-01

    Railroad workers often perform daily work activities on irregular surfaces, specifically on ballast rock. Previous research and injury epidemiology have suggested a relationship between working on irregular surfaces and postural instability. The purpose of this study was to examine the impact of walking on ballast for an extended duration on standing balance. A total of 16 healthy adult males walked on a 7.62 m × 4.57 m (25 ft × 15 ft) walking surface of no ballast (NB) or covered with ballast (B) of an average rock size of about 1 inch for 4 h. Balance was evaluated using dynamic posturography with the NeuroCom(®) Equitest System(™) prior to experiencing the NB or B surface and again every 30 min during the 4 h of ballast exposure. Dependent variables were the sway velocity and root-mean-square (RMS) sway components in the medial-lateral and anterior-posterior directions. Repeated measures ANOVA revealed statistically significant differences in RMS and sway velocity between ballast surface conditions and across exposure times. Overall, the ballast surface condition induced greater sway in all of the dynamic posturography conditions. Walking on irregular surfaces for extended durations has a deleterious effect on balance compared to walking on a surface without ballast. These findings of changes in balance during ballast exposure suggest that working on an irregular surface may impact postural control.

  17. Noisy continuous time random walks

    NASA Astrophysics Data System (ADS)

    Jeon, Jae-Hyung; Barkai, Eli; Metzler, Ralf

    2013-09-01

    Experimental studies of the diffusion of biomolecules within biological cells are routinely confronted with multiple sources of stochasticity, whose identification renders the detailed data analysis of single molecule trajectories quite intricate. Here, we consider subdiffusive continuous time random walks that represent a seminal model for the anomalous diffusion of tracer particles in complex environments. This motion is characterized by multiple trapping events with infinite mean sojourn time. In real physical situations, however, instead of the full immobilization predicted by the continuous time random walk model, the motion of the tracer particle shows additional jiggling, for instance, due to thermal agitation of the environment. We here present and analyze in detail an extension of the continuous time random walk model. Superimposing the multiple trapping behavior with additive Gaussian noise of variable strength, we demonstrate that the resulting process exhibits a rich variety of apparent dynamic regimes. In particular, such noisy continuous time random walks may appear ergodic, while the bare continuous time random walk exhibits weak ergodicity breaking. Detailed knowledge of this behavior will be useful for the truthful physical analysis of experimentally observed subdiffusion.

  18. Ambulatory assessment of walking balance after stroke using instrumented shoes.

    PubMed

    van Meulen, Fokke B; Weenk, Dirk; Buurke, Jaap H; van Beijnum, Bert-Jan F; Veltink, Peter H

    2016-05-19

    For optim