Science.gov

Sample records for prolonged knee-extensor exercise

  1. Effects of 4 weeks preoperative exercise on knee extensor strength after anterior cruciate ligament reconstruction

    PubMed Central

    Kim, Do Kyung; Hwang, Ji Hye; Park, Won Hah

    2015-01-01

    [Purpose] After an anterior cruciate ligament injury and subsequent reconstruction, quadriceps muscle weakness and disruption of proprioceptive function are common. The purpose of this study was to examine the effects of a 4 weeks preoperative exercise intervention on knee strength power and function post-surgery. [Subjects and Methods] Eighty male patients (27.8±5.7 age), scheduled for reconstruction surgery, were randomly assigned to two groups, the preoperative exercise group (n=40) and a no preoperative exercise group (n=40). The preoperative exercise group participated in a 4-week preoperative and 12-week post-operative programs, while the no preoperative exercise group participated only in the 12-week postoperative exercise program. Isokinetic measured of quadriceps strength were obtained at 4 weeks before and 3 months after surgery. [Results] The knee extensor strength deficits measured at 60°/s and 180°/s was significantly lower in the preoperative exercise group compared with the no preoperative exercise group. At 3 months after surgery, the extensor strength deficit was 28.5±9.0% at 60°/sec and 23.3±9.0% at 180°/sec in the preoperative exercise group, whereas the no preoperative exercise group showed extensor strength deficits of 36.5±10.7% and 27.9±12.6% at 60°/sec and 180°/sec, respectively. The preoperative exercise group demonstrated significant improvement the single-leg hop distance. [Conclusion] Four week preoperative exercise may produce many positive effects post reconstruction surgery, including faster recovery of knee extensor strength and function, as measured by single-leg hop ability. PMID:26504270

  2. Protective effect by maximal isometric contractions against maximal eccentric exercise-induced muscle damage of the knee extensors.

    PubMed

    Tseng, Kuo-Wei; Tseng, Wei-Chin; Lin, Ming-Ju; Chen, Hsin-Lian; Nosaka, Kazunori; Chen, Trevor C

    2016-01-01

    This study investigated whether maximal voluntary isometric contractions (MVIC) performed before maximal eccentric contractions (MaxEC) would attenuate muscle damage of the knee extensors. Untrained men were placed to an experimental group that performed 6 sets of 10 MVIC at 90° knee flexion 2 weeks before 6 sets of 10 MaxEC or a control group that performed MaxEC only (n = 13/group). Changes in muscle damage markers were assessed before to 5 days after each exercise. Small but significant changes in maximal voluntary concentric contraction torque, range of motion (ROM) and plasma creatine kinase (CK) activity were evident at immediately to 2 days post-MVIC (p < 0.05), but other variables (e.g. thigh girth, myoglobin concentration, B-mode echo intensity) did not change significantly. Changes in all variables after MaxEC were smaller (p < 0.05) by 45% (soreness)-67% (CK) for the experimental than the control group. These results suggest that MVIC conferred potent protective effect against MaxEC-induced muscle damage. PMID:27366814

  3. The effect of exercise-induced muscle damage on isometric and dynamic knee extensor strength and vertical jump performance.

    PubMed

    Byrne, Christopher; Eston, Roger

    2002-05-01

    In this study, we assessed the effect of exercise-induced muscle damage on knee extensor muscle strength during isometric, concentric and eccentric actions at 1.57 rad x s(-1) and vertical jump performance under conditions of squat jump, countermovement jump and drop jump. The eight participants (5 males, 3 females) were aged 29.5+/-7.1 years (mean +/- s). These variables, together with plasma creatine kinase (CK), were measured before, 1 h after and 1, 2, 3, 4 and 7 days after a bout of muscle damaging exercise: 100 barbell squats (10 sets x 10 repetitions at 70% body mass load). Strength was reduced for 4 days (P< 0.05) but no significant differences (P> 0.05) were apparent in the magnitude or rate of recovery of strength between isometric, concentric and eccentric muscle actions. The overall decline in vertical jump performance was dependent on jump method: squat jump performance was affected to a greater extent than countermovement (91.6+/-1.1% vs 95.2+/-1.3% of pre-exercise values, P< 0.05) and drop jump (95.2+/-1.4%, P< 0.05) performance. Creatine kinase was elevated (P < 0.05) above baseline 1 h after exercise, peaked on day 1 and remained significantly elevated on days 2 and 3. Strength loss after exercise-induced muscle damage was independent of the muscle action being performed. However, the impairment of muscle function was attenuated when the stretch-shortening cycle was used in vertical jumping performance. PMID:12043831

  4. Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans.

    PubMed

    Bailey, Stephen J; Fulford, Jonathan; Vanhatalo, Anni; Winyard, Paul G; Blackwell, Jamie R; DiMenna, Fred J; Wilkerson, Daryl P; Benjamin, Nigel; Jones, Andrew M

    2010-07-01

    The purpose of this study was to elucidate the mechanistic bases for the reported reduction in the O(2) cost of exercise following short-term dietary nitrate (NO(3)(-)) supplementation. In a randomized, double-blind, crossover study, seven men (aged 19-38 yr) consumed 500 ml/day of either nitrate-rich beet root juice (BR, 5.1 mmol of NO(3)(-)/day) or placebo (PL, with negligible nitrate content) for 6 consecutive days, and completed a series of low-intensity and high-intensity "step" exercise tests on the last 3 days for the determination of the muscle metabolic (using (31)P-MRS) and pulmonary oxygen uptake (Vo(2)) responses to exercise. On days 4-6, BR resulted in a significant increase in plasma [nitrite] (mean +/- SE, PL 231 +/- 76 vs. BR 547 +/- 55 nM; P < 0.05). During low-intensity exercise, BR attenuated the reduction in muscle phosphocreatine concentration ([PCr]; PL 8.1 +/- 1.2 vs. BR 5.2 +/- 0.8 mM; P < 0.05) and the increase in Vo(2) (PL 484 +/- 41 vs. BR 362 +/- 30 ml/min; P < 0.05). During high-intensity exercise, BR reduced the amplitudes of the [PCr] (PL 3.9 +/- 1.1 vs. BR 1.6 +/- 0.7 mM; P < 0.05) and Vo(2) (PL 209 +/- 30 vs. BR 100 +/- 26 ml/min; P < 0.05) slow components and improved time to exhaustion (PL 586 +/- 80 vs. BR 734 +/- 109 s; P < 0.01). The total ATP turnover rate was estimated to be less for both low-intensity (PL 296 +/- 58 vs. BR 192 +/- 38 microM/s; P < 0.05) and high-intensity (PL 607 +/- 65 vs. BR 436 +/- 43 microM/s; P < 0.05) exercise. Thus the reduced O(2) cost of exercise following dietary NO(3)(-) supplementation appears to be due to a reduced ATP cost of muscle force production. The reduced muscle metabolic perturbation with NO(3)(-) supplementation allowed high-intensity exercise to be tolerated for a greater period of time. PMID:20466802

  5. Sex differences in leg vasodilation during graded knee extensor exercise in young adults.

    PubMed

    Parker, Beth A; Smithmyer, Sandra L; Pelberg, Justin A; Mishkin, Aaron D; Herr, Michael D; Proctor, David N

    2007-11-01

    Limb vascular conductance responses to pharmacological and nonexercise vasodilator stimuli are generally augmented in women compared with men. In the present investigation, we tested the hypothesis that exercise-induced vasodilator responses are also greater in women than men. Sixteen women and 15 men (20-30 yr) with similar fitness and activity levels performed graded quadriceps exercise (supine, single-leg knee extensions, 40 contractions/min) to maximal exertion. Active limb hemodynamics (left common femoral artery diameter and volumetric blood flow), heart rate (ECG), and beat-to-beat mean arterial blood pressure (MAP; radial artery tonometry) were measured during each 3-min workload (4.8 and 8 W/stage for women and men, respectively). The hyperemic response to exercise (slope of femoral blood flow vs. workload) was greater (P < 0.01) in women as was femoral blood flow at workloads >15 W. The leg vasodilatory response to exercise (slope of calculated femoral vascular conductance vs. absolute workload) was also greater in women than in men (P < 0.01) because of the sex difference in hyperemia and the women's lower MAP ( approximately 10-15 mmHg) at all workloads (P < 0.05). The femoral artery dilated to a significantly greater extent in the women ( approximately 0.5 mm) than in the men ( approximately 0.1 mm) across all submaximal workloads. At maximal exertion, femoral vascular conductance was lower in the men (men, 18.0 +/- 0.6 ml.min(-1)xmmHg(-1); women, 22.6 +/- 1.4 mlxmin(-1)xmmHg(-1); P < 0.01). Collectively, these findings suggest that the vasodilatory response to dynamic leg exercise is greater in young women vs. men. PMID:17717115

  6. Acute Postexercise Time Course Responses of Hypertrophic vs. Power-Endurance Squat Exercise Protocols on Maximal and Rapid Torque of the Knee Extensors.

    PubMed

    Conchola, Eric C; Thiele, Ryan M; Palmer, Ty B; Smith, Doug B; Thompson, Brennan J

    2015-05-01

    The aim of this study was to examine the effects of a medium-intensity high-volume vs. explosive squat protocol on the postexercise time course responses of maximal and rapid strength of the knee extensors. Seventeen resistance-trained men (mean ± SD: age = 22.0 ± 2.6 years) performed maximal voluntary contractions (MVCs) of the knee extensors before and after performing a squat workout using either a low-intensity fast velocity (LIFV) (5 × 16 at 40% 1 repetition maximum) or a traditional high-intensity slow velocity (TISV) (5 × 8 at 80% 1RM) exercise protocol. For each MVC, peak torque (PT), peak rate of torque development (RTDpeak), absolute (RTDabs), and relative RTD (RTDnorm) at early (0-50 milliseconds) and late (100-200 milliseconds) phases of muscle contraction were examined at pre- (Pre) and post-exercise at 0, 7, 15, and 30 (Post0...30) minutes. There were no intensity × time interactions for any variables (p = 0.098-0.832). Peak torque was greater at Pre than Post0 and Post7 (p = 0.001-0.016) but was not greater than Post15 and Post30 (p = 0.010-0.189). RTDpeak and early absolute RTD (RTD50abs) were greater at Pre than all postexercise time phases (p = 0.001-0.050); however, later absolute RTD (RTD100-200abs) was only greater at Pre than Post0 and Post30 (p = 0.013-0.048). Early relative RTD (RTD50norm) was only higher at Pre compared with Post0 (p = 0.023), whereas no differences were observed for later relative RTD (RTD100-200norm) (p = 0.920-0.990). Low-intensity fast velocity and TISV squat protocols both yielded acute decreases in maximal and rapid strength capacities following free-weight squats, with rapid strength showing slower recovery characteristics than maximal strength. PMID:25774625

  7. Muscle metabolism and activation heterogeneity by combined 31P chemical shift and T2 imaging, and pulmonary O2 uptake during incremental knee-extensor exercise

    PubMed Central

    Cannon, Daniel T.; Howe, Franklyn A.; Whipp, Brian J.; Ward, Susan A.; McIntyre, Dominick J.; Ladroue, Christophe; Griffiths, John R.; Kemp, Graham J.

    2013-01-01

    The integration of skeletal muscle substrate depletion, metabolite accumulation, and fatigue during large muscle-mass exercise is not well understood. Measurement of intramuscular energy store degradation and metabolite accumulation is confounded by muscle heterogeneity. Therefore, to characterize regional metabolic distribution in the locomotor muscles, we combined 31P magnetic resonance spectroscopy, chemical shift imaging, and T2-weighted imaging with pulmonary oxygen uptake during bilateral knee-extension exercise to intolerance. Six men completed incremental tests for the following: 1) unlocalized 31P magnetic resonance spectroscopy; and 2) spatial determination of 31P metabolism and activation. The relationship of pulmonary oxygen uptake to whole quadriceps phosphocreatine concentration ([PCr]) was inversely linear, and three of four knee-extensor muscles showed activation as assessed by change in T2. The largest changes in [PCr], [inorganic phosphate] ([Pi]) and pH occurred in rectus femoris, but no voxel (72 cm3) showed complete PCr depletion at exercise cessation. The most metabolically active voxel reached 11 ± 9 mM [PCr] (resting, 29 ± 1 mM), 23 ± 11 mM [Pi] (resting, 7 ± 1 mM), and a pH of 6.64 ± 0.29 (resting, 7.08 ± 0.03). However, the distribution of 31P metabolites and pH varied widely between voxels, and the intervoxel coefficient of variation increased between rest (∼10%) and exercise intolerance (∼30–60%). Therefore, the limit of tolerance was attained with wide heterogeneity in substrate depletion and fatigue-related metabolite accumulation, with extreme metabolic perturbation isolated to only a small volume of active muscle (<5%). Regional intramuscular disturbances are thus likely an important requisite for exercise intolerance. How these signals integrate to limit muscle power production, while regional “recruitable muscle” energy stores are presumably still available, remains uncertain. PMID:23813534

  8. Intensity-dependent alterations in the excitability of cortical and spinal projections to the knee extensors during isometric and locomotor exercise

    PubMed Central

    Weavil, J. C.; Sidhu, S. K.; Mangum, T. S.; Richardson, R. S.

    2015-01-01

    We investigated the role of exercise intensity and associated central motor drive in determining corticomotoneuronal excitability. Ten participants performed a series of nonfatiguing (3 s) isometric single-leg knee extensions (ISO; 10–100% of maximal voluntary contractions, MVC) and cycling bouts (30–160% peak aerobic capacity, Wpeak). At various exercise intensities, electrical potentials were evoked in the vastus lateralis (VL) and rectus femoris (RF) via transcranial magnetic stimulation (motor-evoked potentials, MEP), and electrical stimulation of both the cervicomedullary junction (cervicomedullary evoked potentials, CMEP) and the femoral nerve (maximal M-waves, Mmax). Whereas Mmax remained unchanged in both muscles (P > 0.40), voluntary electromyographic activity (EMG) increased in an exercise intensity-dependent manner for ISO and cycling exercise in VL and RF (both P < 0.001). During ISO exercise, MEPs and CMEPs progressively increased in VL and RF until a plateau was reached at ∼75% MVC; further increases in contraction intensity did not cause additional changes (P > 0.35). During cycling exercise, VL-MEPs and CMEPs progressively increased by ∼65% until a plateau was reached at Wpeak. In contrast, RF MEPs and CMEPs progressively increased by ∼110% throughout the tested cycling intensities without the occurrence of a plateau. Furthermore, alterations in EMG below the plateau influenced corticomotoneuronal excitability similarly between exercise modalities. In both exercise modalities, the MEP-to-CMEP ratio did not change with exercise intensity (P > 0.22). In conclusion, increases in exercise intensity and EMG facilitates the corticomotoneuronal pathway similarly in isometric knee extension and locomotor exercise until a plateau occurs at a submaximal exercise intensity. This facilitation appears to be primarily mediated by increases in excitability of the motoneuron pool. PMID:25876651

  9. Differential serial sarcomere number adaptations in knee extensor muscles of rats is contraction type dependent.

    PubMed

    Butterfield, Timothy A; Leonard, Timothy R; Herzog, Walter

    2005-10-01

    Sarcomerogenesis, or the addition of sarcomeres in series within a fiber, has a profound impact on the performance of a muscle by increasing its contractile velocity and power. Sarcomerogenesis may provide a beneficial adaptation to prevent injury when a muscle consistently works at long lengths, accounting for the repeated-bout effect. The association between eccentric exercise, sarcomerogenesis and the repeated-bout effect has been proposed to depend on damage, where regeneration allows sarcomeres to work at shorter lengths for a given muscle-tendon unit length. To gain additional insight into this phenomenon, we measured fiber dynamics directly in the vastus lateralis (VL) muscle of rats during uphill and downhill walking, and we measured serial sarcomere number in the VL and vastus intermedius (VI) after chronic training on either a decline or incline grade. We found that the knee extensor muscles of uphill walking rats undergo repeated active concentric contractions, and therefore they suffer no contraction-induced injury. Conversely, the knee extensor muscles during downhill walking undergo repeated active eccentric contractions. Serial sarcomere numbers change differently for the uphill and downhill exercise groups, and for the VL and VI muscles. Short muscle lengths for uphill concentric-biased contractions result in a loss of serial sarcomeres, and long muscle lengths for downhill eccentric-biased contractions result in a gain of serial sarcomeres. PMID:15947030

  10. Bilateral Knee Extensor Fatigue Modulates Force and Responsiveness of the Corticospinal Pathway in the Non-fatigued, Dominant Elbow Flexors

    PubMed Central

    Šambaher, Nemanja; Aboodarda, Saied Jalal; Behm, David George

    2016-01-01

    Exercise-induced fatigue affects muscle performance and modulates corticospinal excitability in non-exercised muscles. The purpose of this study was to investigate the effect of bilateral knee extensor fatigue on dominant elbow flexor (EF) maximal voluntary force production and corticospinal excitability. Transcranial magnetic, transmastoid electrical and brachial plexus electrical stimulation (BPES) were used to investigate corticospinal, spinal, and muscle excitability of the dominant EF before and after a bilateral knee extensor fatiguing protocol or time matched rest period (control). For both sessions three stimuli were delivered every 1.5 s during the three pre-test time points and during the 1st, 3rd, 6th, 9th and 12th post-test 5 s EF isometric maximal voluntary contractions (MVC). In both conditions, overall, EF MVC force (p < 0.001) decreased progressively from repetition #1 to #12 during the post-test MVC protocol. EF MVC force (p < 0.001, ES = 0.9, Δ10.3%) decrements were more pronounced in the knee extensor fatigue intervention condition. In addition, there were no significant differences between conditions for biceps brachii electromyographic (EMG) activity (p = 0.43), motor evoked potentials (MEPs) amplitude (p = 0.908) or MEP silent period (SP; p = 0.776). However, the fatigue condition exhibited a lower MEP/cervicomedullary MEP (CMEP) ratio (p = 0.042, ES = 2.5, Δ25%) and a trend toward higher CMEP values (p = 0.08, ES = 0.5, Δ20.4%). These findings suggest that bilateral knee extensor fatigue can impair performance and modulate corticospinal excitability of the EF. PMID:26869902

  11. Bilateral Knee Extensor Fatigue Modulates Force and Responsiveness of the Corticospinal Pathway in the Non-fatigued, Dominant Elbow Flexors.

    PubMed

    Šambaher, Nemanja; Aboodarda, Saied Jalal; Behm, David George

    2016-01-01

    Exercise-induced fatigue affects muscle performance and modulates corticospinal excitability in non-exercised muscles. The purpose of this study was to investigate the effect of bilateral knee extensor fatigue on dominant elbow flexor (EF) maximal voluntary force production and corticospinal excitability. Transcranial magnetic, transmastoid electrical and brachial plexus electrical stimulation (BPES) were used to investigate corticospinal, spinal, and muscle excitability of the dominant EF before and after a bilateral knee extensor fatiguing protocol or time matched rest period (control). For both sessions three stimuli were delivered every 1.5 s during the three pre-test time points and during the 1st, 3rd, 6th, 9th and 12th post-test 5 s EF isometric maximal voluntary contractions (MVC). In both conditions, overall, EF MVC force (p < 0.001) decreased progressively from repetition #1 to #12 during the post-test MVC protocol. EF MVC force (p < 0.001, ES = 0.9, Δ10.3%) decrements were more pronounced in the knee extensor fatigue intervention condition. In addition, there were no significant differences between conditions for biceps brachii electromyographic (EMG) activity (p = 0.43), motor evoked potentials (MEPs) amplitude (p = 0.908) or MEP silent period (SP; p = 0.776). However, the fatigue condition exhibited a lower MEP/cervicomedullary MEP (CMEP) ratio (p = 0.042, ES = 2.5, Δ25%) and a trend toward higher CMEP values (p = 0.08, ES = 0.5, Δ20.4%). These findings suggest that bilateral knee extensor fatigue can impair performance and modulate corticospinal excitability of the EF. PMID:26869902

  12. Comparison of Recovery Strategies on Maximal Force-Generating Capacity and Electromyographic Activity Level of the Knee Extensor Muscles

    PubMed Central

    Zarrouk, Nidhal; Rebai, Haithem; Yahia, Abdelmoneem; Souissi, Nizar; Hug, François; Dogui, Mohamed

    2011-01-01

    Context: With regard to intermittent training exercise, the effects of the mode of recovery on subsequent performance are equivocal. Objective: To compare the effects of 3 types of recovery intervention on peak torque (PT) and electromyographic (EMG) activity of the knee extensor muscles after fatiguing isokinetic intermittent concentric exercise. Design: Crossover study. Setting: Research laboratory. Patients or Other Participants: Eight elite judo players (age = 18.4 ± 1.4 years, height = 180 ± 3 cm, mass = 77.0 ± 4.2 kg). Interventions : Participants completed 3 randomized sessions within 7 days. Each session consisted of 5 sets of 10 concentric knee extensions at 80% PT at 120°/s, with 3 minutes of recovery between sets. Recovery interventions were passive, active, and electromyostimulation. The PT and maximal EMG activity were recorded simultaneously while participants performed isokinetic dynamometer trials before and 3 minutes after the resistance exercise. Main Outcome Measure(s): The PT and maximal EMG activity from the knee extensors were quantified at isokinetic velocities of 60°/s, 120°/s, and 180°/s, with 5 repetitions at each velocity. Results: The reduction in PT observed after electromyo-stimulation was less than that seen after passive (P < .001) or active recovery (P < .001). The reduction in PT was less after passive recovery than after active recovery (P < .001). The maximal EMG activity level observed after electromyostimulation was higher than that seen after active recovery (P < .05). Conclusions: Electromyostimulation was an effective recovery tool in decreasing neuromuscular fatigue after high-intensity, intermittent isokinetic concentric exercise for the knee extensor muscles. Also, active recovery induced the greatest amount of neuromuscular fatigue. PMID:21944070

  13. The Artificial Gravity Bed Rest Pilot Project: Effects on Knee Extensor and Plantar Flexor Muscle Groups

    NASA Technical Reports Server (NTRS)

    Caiozzo, V. J.; Haddad, F.; Lee, S.; Baker, M.; Baldwin, K. M.

    2007-01-01

    The goal of this project was to examine the effects of artificial gravity (2.5 g) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) control (C) group (N=7); and 2) an AG group (N=8), which was exposed to 21 days of bed-rest plus daily 1 hr exposures to AG (2.5 g). This particular experiment was part of an integrated AG Pilot Project sponsored by NASA/Johnson Space Center. The in vivo torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre and post treatment. Also, pre- and post treatment biopsy samples were obtained from both the vastus lateralis and soleus muscles and were used, in part, for a series of analyses on gene expression (mRNA abundance) of key factors implicated in the anabolic versus catabolic state of the muscle. Post/Pre toque-velocity determinations revealed greater decrements in knee extensor performance in the C versus AG group (P less than 0.04). The plantar flexor muscle group of the AG subjects actually demonstrated a net gain in torque-velocity relationship; whereas, in the C group the overall post/pre responses declined (AG vs C; P less than 0.001). Measurements of muscle fiber cross-sectional area (for both muscles) demonstrated a loss of approx. 20% in the C group while no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity (IGF-1, IGF-1 BP4, mechano growth factor, total RNA, and pro-collagen 3a) were higher in the AG group, whereas catabolic markers (myostatin and atrogen) were elevated in the C group. Importantly, these patterns were seen in both muscles. Based on these observations we conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading states. These findings also

  14. Tennis in hot and cool conditions decreases the rapid muscle torque production capacity of the knee extensors but not of the plantar flexors

    PubMed Central

    Girard, Olivier; Racinais, Sébastien; Périard, Julien D

    2014-01-01

    Objectives To assess the time course of changes in rapid muscle force/torque production capacity and neuromuscular activity of lower limb muscles in response to prolonged (∼2 h) match-play tennis under heat stress. Methods The rates of torque development (RTD) and electromyographic activity (EMG; ie, root mean square) rise were recorded from 0 to 30, –50, –100 and –200 ms during brief (3–5 s) explosive maximal isometric voluntary contractions (MVC) of the knee extensors (KE) and plantar flexors (PF), along with the peak RTD within the entirety of the torque-time curve. These values were recorded in 12 male tennis players before (prematch) and after (postmatch, 24 and 48 h) match-play in HOT (∼37°C) and COOL (∼22°C) conditions. Results The postmatch core temperature was greater in the HOT (∼39.4°C) vs COOL (∼38.7°C) condition (p<0.05). Reductions in KE RTD occurred within the 0–200 ms epoch after contraction onset postmatch and at 24 h, compared with prematch, independent of environmental conditions (p<0.05). A similar reduction in the KE peak RTD was also observed postmatch relative to prematch (p<0.05). No differences in KE RTD values were observed after normalisation to MVC torque. Furthermore, the rate of KE EMG activity rise remained unchanged. Conversely, the PF contractile RTD and rate of EMG activity rise were unaffected by the exercise or environmental conditions. Conclusions In the KE, a reduction in maximal torque production capacity following prolonged match-play tennis appears to account for the decrease in the rate of torque development, independent of environmental conditions, while remaining unchanged in the PF. PMID:24668381

  15. Improved Knee Extensor Strength with Resistance Training Associates with Muscle Specific miRNAs in Older Adults

    PubMed Central

    Zhang, Tan; Birbrair, Alexander; Wang, Zhong-Min; Messi, María L.; Marsh, Anthony P.; Leng, Iris; Nicklas, Barbara J.; Delbono, Osvaldo

    2015-01-01

    Regular exercise, particularly resistance training (RT), is the only therapy known to consistently improve muscle strength and quality (force per unit of mass) in older persons, but there is considerable variability in responsiveness to training. Identifying sensitive diagnostic biomarkers of responsiveness to RT may inform the design of a more efficient exercise regimen to improve muscle strength in older adults. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression. We quantified six muscle specific miRNAs (miR-1, -133a, -133b, -206, -208b and -499) in both muscle tissue and blood plasma, and their relationship with knee extensor strength in seven older (age = 70.5 ± 2.5 years) adults before and after 5 months of RT. MiRNAs differentially responded to RT; muscle miR-133b decreased, while all plasma miRNAs tended to increase. Percent changes in knee extensor strength with RT showed strong positive correlations with percent changes in muscle miR-133a, -133b, -206 and with percent changes in plasma and plasma/muscle miR-499 ratio. Baseline level of plasma or plasma/muscle miR-499 ratio further predicts muscle response to RT, while changes in muscle miR-133a, -133b, -206 may correlate with muscle TNNT1gene alternative splicing in response to RT. Our results indicate that RT alters muscle specific miRNAs in muscle and plasma, and that these changes account for some of the variation in strength responses to RT in older adults. PMID:25560803

  16. Rhythmic Isometric Fatigue Patterns of the Elbow Flexors and Knee Extensors

    ERIC Educational Resources Information Center

    Ordway, George A.; And Others

    1977-01-01

    During a rhythmic, all-out task, the rates of fatigue experienced by elbow flexor and knee extendor muscle groups tend to differ, with the elbow flexors fatiguing more rapidly initially, but reaching a plateau at a relatively higher level than the knee extensors. (Author)

  17. The Effect of an Exercise Program in Conjunction With Short-Period Patellar Taping on Pain, Electromyogram Activity, and Muscle Strength in Patellofemoral Pain Syndrome

    PubMed Central

    Kaya, Defne; Callaghan, Michael James; Ozkan, Huseyin; Ozdag, Fatih; Atay, Ozgur Ahmet; Yuksel, Inci; Doral, Mahmut Nedim

    2010-01-01

    Background: McConnell recommended that patellar tape be kept on all day, until patients learn how to activate their vastus medialis obliquus (VMO) during an exercise program. This application may pose problems because prolonged taping may be inadvisable for some patients or even contraindicated owing to skin discomfort, irritation, or allergic reaction. Hypothesis: Wearing patellofemoral tape for a shorter duration during an exercise program would be just as beneficial as a prolonged taping application. Study Design: Prospective cohort. Methods: Twelve patients and 16 healthy people participated. Patients underwent short-period patellar taping plus an exercise program for 3 months. Numeric pain rating, muscle strength of the knee extensors, and electromyogram activity of the vastus lateralis and VMO were evaluated. Results: There were significant differences in electromyogram activity (P = .04) and knee extensor muscle strength (P = .03) between involved and uninvolved sides before treatment. After treatment, pain scores decreased, and there were no significant differences between involved and uninvolved sides in electromyogram activity (P = .68) and knee extensor strength (P = .62). Before treatment, mean VMO activation started significantly later than that of vastus lateralis, as compared with the matched healthy control group (P = .01). After treatment, these differences were nonsignificant (P = .08). Conclusion: Short-period patellar taping plus an exercise program improves VMO and vastus lateralis activation. Clinical Relevance: A shorter period of taping for the exercise program may be as beneficial as a prolonged taping application. PMID:23015969

  18. Radiographic analysis of factors predisposing toward tendon tears in the knee extensor mechanism☆☆☆

    PubMed Central

    Pires e Albuquerque, Rodrigo; Campos, André Luiz Siqueira; dos Santos Neto, José Félix; Karam, Evaldo; Neves, José Guilherme; Di Tullio, Paulo; Giordano, Vincenzo; do Amaral, Ney Pecegueiro

    2014-01-01

    Objectives to review radiographs of patients who suffered tendon tears of the knee extensor apparatus and observe alterations that might be factors predisposing toward this type of injury. Methods we retrospectively analyzed 60 cases of injury to the knee extensor mechanism that were treated surgically at the Miguel Couto Municipal Hospital between March 2004 and March 2011. Four patients were excluded due to poor quality of the examination. Results of the 56 patients evaluated, 23 were considered to be normal and 33 presented radiographic alterations. Among these, eight (24.3%) presented suprapatellar osteophytes alone; seven (21.2%), infrapatellar calcification; seven (21.2%), suprapatellar calcification; six (18.2%), supra- and infrapatellar osteophytes; and five (15.1%), infrapatellar osteophytes alone. Conclusion radiographic alterations were frequently observed in patients with extensor mechanism tears. PMID:26229830

  19. Effects of 17-day spaceflight on knee extensor muscle function and size

    NASA Technical Reports Server (NTRS)

    Tesch, Per A.; Berg, Hans E.; Bring, Daniel; Evans, Harlan J.; LeBlanc, Adrian D.

    2005-01-01

    It is generally held that space travelers experience muscle dysfunction and atrophy during exposure to microgravity. However, observations are scarce and reports somewhat inconsistent with regard to the time course, specificity and magnitude of such changes. Hence, we examined four male astronauts (group mean approximately 43 years, 86 kg and 183 cm) before and after a 17-day spaceflight (Space Transport System-78). Knee extensor muscle function was measured during maximal bilateral voluntary isometric and iso-inertial concentric, and eccentric actions. Cross-sectional area (CSA) of the knee extensor and flexor, and gluteal muscle groups was assessed by means of magnetic resonance imaging. The decrease in strength (P<0.05) across different muscle actions after spaceflight amounted to 10%. Eight ambulatory men, examined on two occasions 20 days apart, showed unchanged (P>0.05) muscle strength. CSA of the knee extensor and gluteal muscles, each decreased (P<0.05) by 8%. Knee flexor muscle CSA showed no significant (P>0.05) change. The magnitude of these changes concord with earlier results from ground-based studies of similar duration. The results of this study, however, do contrast with the findings of no decrease in maximal voluntary ankle plantar flexor force previously reported in the same crew.

  20. Mental fatigue induced by prolonged self-regulation does not exacerbate central fatigue during subsequent whole-body endurance exercise.

    PubMed

    Pageaux, Benjamin; Marcora, Samuele M; Rozand, Vianney; Lepers, Romuald

    2015-01-01

    It has been shown that the mental fatigue induced by prolonged self-regulation increases perception of effort and reduces performance during subsequent endurance exercise. However, the physiological mechanisms underlying these negative effects of mental fatigue are unclear. The primary aim of this study was to test the hypothesis that mental fatigue exacerbates central fatigue induced by whole-body endurance exercise. Twelve subjects performed 30 min of either an incongruent Stroop task to induce a condition of mental fatigue or a congruent Stroop task (control condition) in a random and counterbalanced order. Both cognitive tasks (CTs) were followed by a whole-body endurance task (ET) consisting of 6 min of cycling exercise at 80% of peak power output measured during a preliminary incremental test. Neuromuscular function of the knee extensors was assessed before and after CT, and after ET. Rating of perceived exertion (RPE) was measured during ET. Both CTs did not induce any decrease in maximal voluntary contraction (MVC) torque (p = 0.194). During ET, mentally fatigued subjects reported higher RPE (mental fatigue 13.9 ± 3.0, control 13.3 ± 3.2, p = 0.044). ET induced a similar decrease in MVC torque (mental fatigue -17 ± 15%, control -15 ± 11%, p = 0.001), maximal voluntary activation level (mental fatigue -6 ± 9%, control -6 ± 7%, p = 0.013) and resting twitch (mental fatigue -30 ± 14%, control -32 ± 10%, p < 0.001) in both conditions. These findings reject our hypothesis and confirm previous findings that mental fatigue does not reduce the capacity of the central nervous system to recruit the working muscles. The negative effect of mental fatigue on perception of effort does not reflect a greater development of either central or peripheral fatigue. Consequently, mentally fatigued subjects are still able to perform maximal exercise, but they are experiencing an altered performance during submaximal exercise due to higher-than-normal perception of effort

  1. Acute Effects of Kinesio Taping on Knee Extensor Peak Torque and Stretch Reflex in Healthy Adults.

    PubMed

    Yeung, Simon S; Yeung, Ella W

    2016-01-01

    Kinesio Tex tape (KT) is used to prevent and treat sports-related injuries and to enhance muscle performance. It has been proposed that the direction of taping may either facilitate or inhibit the muscle by having different effects on cutaneous receptors that modulate excitability of the motor neurons. This study had 2 goals. First, we wished to determine if KT application affects muscle performance and if the method of application facilitates or inhibits muscle performance. This was assessed by measuring isokinetic knee extension peak torque in the knee extensor. Second, we assessed neurological effects of taping on the excitability of the motor neurons by measuring the reflex latency and action potential by electromyography (EMG) in the patellar reflex. The study was a single-blind, placebo-controlled crossover trial with 28 healthy volunteers with no history of knee injuries. Participants received facilitative KT treatment, inhibitory KT treatment, or Hypafix taping of the knee extensor. There were significant differences in the peak torque between 3 treatments (F(2,54) = 4.873, P < 0.01). Post hoc analysis revealed that facilitative KT treatment resulted in higher knee extensor peak torque performance than inhibitory KT treatment (P = 0.036, effect size 0.26). There were, however, no significant differences in the reflex latency (F(2,54) = 2.84, P = 0.067) nor in the EMG values (F(2,54) = 0.18, P = 0.837) in the patellar reflex between the 3 taping applications. The findings suggest that the direction of KT application over the muscle has specific effects on muscle performance. Given the magnitude of effect is small, interpretation of clinical significance should be considered with caution. The underlying mechanism warrants further investigation. PMID:26825916

  2. Effect of Preactivation on Torque Enhancement by the Stretch-Shortening Cycle in Knee Extensors

    PubMed Central

    Fukutani, Atsuki; Misaki, Jun; Isaka, Tadao

    2016-01-01

    The stretch-shortening cycle is one of the most interesting topics in the field of sport sciences, because the performance of human movement is enhanced by the stretch-shortening cycle (eccentric contraction). The purpose of the present study was to examine whether the influence of preactivation on the torque enhancement by stretch-shortening cycle in knee extensors. Twelve men participated in this study. The following three conditions were conducted for knee extensors: (1) concentric contraction without preactivation (CON), (2) concentric contraction with eccentric preactivation (ECC), and (3) concentric contraction with isometric preactivation (ISO). Muscle contractions were evoked by electrical stimulation to discard the influence of neural activity. The range of motion of the knee joint was set from 80 to 140 degrees (full extension = 180 degrees). Angular velocities of the concentric and eccentric contractions were set at 180 and 90 degrees/s, respectively. In the concentric contraction phase, joint torques were recorded at 85, 95, and 105 degrees, and they were compared among the three conditions. In the early phase (85 degrees) of concentric contraction, the joint torque was larger in the ECC and ISO conditions than in the CON condition. However, these clear differences disappeared in the later phase (105 degrees) of concentric contraction. The results showed that joint torque was clearly different among the three conditions in the early phase whereas this difference disappeared in the later phase. Thus, preactivation, which is prominent in the early phase of contractions, plays an important role in torque enhancement by the stretch-shortening cycle in knee extensors. PMID:27414804

  3. High Altitude Increases Alteration in Maximal Torque but Not in Rapid Torque Development in Knee Extensors after Repeated Treadmill Sprinting.

    PubMed

    Girard, Olivier; Brocherie, Franck; Millet, Grégoire P

    2016-01-01

    We assessed knee extensor neuromuscular adjustments following repeated treadmill sprints in different normobaric hypoxia conditions, with special reference to rapid muscle torque production capacity. Thirteen team- and racquet-sport athletes undertook 8 × 5-s "all-out" sprints (passive recovery = 25 s) on a non-motorized treadmill in normoxia (NM; FiO2 = 20.9%), at low (LA; FiO2 = 16.8%) and high (HA; FiO2 = 13.3%) normobaric hypoxia (simulated altitudes of ~1800 m and ~3600 m, respectively). Explosive (~1 s; "fast" instruction) and maximal (~5 s; "hard" instruction) voluntary isometric contractions (MVC) of the knee extensors (KE), with concurrent electromyographic (EMG) activity recordings of the vastus lateralis (VL) and rectus femoris (RF) muscles, were performed before and 1-min post-exercise. Rate of torque development (RTD) and EMG (i.e., Root Mean Square or RMS) rise from 0 to 30, -50, -100, and -200 ms were recorded, and were also normalized to maximal torque and EMG values, respectively. Distance covered during the first 5-s sprint was similar (P > 0.05) in all conditions. A larger (P < 0.05) sprint decrement score and a shorter (P < 0.05) cumulated distance covered over the eight sprints occurred in HA (-8 ± 4% and 178 ± 11 m) but not in LA (-7 ± 3% and 181 ± 10 m) compared to NM (-5 ± 2% and 183 ± 9 m). Compared to NM (-9 ± 7%), a larger (P < 0.05) reduction in MVC torque occurred post-exercise in HA (-14 ± 9%) but not in LA (-12 ± 7%), with no difference between NM and LA (P > 0.05). Irrespectively of condition (P > 0.05), peak RTD (-6 ± 11%; P < 0.05), and normalized peak RMS activity for VL (-8 ± 11%; P = 0.07) and RF (-14 ± 11%; P < 0.01) muscles were reduced post-exercise, whereas reductions (P < 0.05) in absolute RTD occurred within the 0-100 (-8 ± 9%) and 0-200 ms (-10 ± 8%) epochs after contraction onset. After normalization to MVC torque, there was no difference in RTD values. Additionally, the EMG rise for VL muscle was similar

  4. High Altitude Increases Alteration in Maximal Torque but Not in Rapid Torque Development in Knee Extensors after Repeated Treadmill Sprinting

    PubMed Central

    Girard, Olivier; Brocherie, Franck; Millet, Grégoire P.

    2016-01-01

    We assessed knee extensor neuromuscular adjustments following repeated treadmill sprints in different normobaric hypoxia conditions, with special reference to rapid muscle torque production capacity. Thirteen team- and racquet-sport athletes undertook 8 × 5-s “all-out” sprints (passive recovery = 25 s) on a non-motorized treadmill in normoxia (NM; FiO2 = 20.9%), at low (LA; FiO2 = 16.8%) and high (HA; FiO2 = 13.3%) normobaric hypoxia (simulated altitudes of ~1800 m and ~3600 m, respectively). Explosive (~1 s; “fast” instruction) and maximal (~5 s; “hard” instruction) voluntary isometric contractions (MVC) of the knee extensors (KE), with concurrent electromyographic (EMG) activity recordings of the vastus lateralis (VL) and rectus femoris (RF) muscles, were performed before and 1-min post-exercise. Rate of torque development (RTD) and EMG (i.e., Root Mean Square or RMS) rise from 0 to 30, −50, −100, and −200 ms were recorded, and were also normalized to maximal torque and EMG values, respectively. Distance covered during the first 5-s sprint was similar (P > 0.05) in all conditions. A larger (P < 0.05) sprint decrement score and a shorter (P < 0.05) cumulated distance covered over the eight sprints occurred in HA (−8 ± 4% and 178 ± 11 m) but not in LA (−7 ± 3% and 181 ± 10 m) compared to NM (−5 ± 2% and 183 ± 9 m). Compared to NM (−9 ± 7%), a larger (P < 0.05) reduction in MVC torque occurred post-exercise in HA (−14 ± 9%) but not in LA (-12 ± 7%), with no difference between NM and LA (P > 0.05). Irrespectively of condition (P > 0.05), peak RTD (−6 ± 11%; P < 0.05), and normalized peak RMS activity for VL (−8 ± 11%; P = 0.07) and RF (−14 ± 11%; P < 0.01) muscles were reduced post-exercise, whereas reductions (P < 0.05) in absolute RTD occurred within the 0–100 (−8 ± 9%) and 0–200 ms (−10 ± 8%) epochs after contraction onset. After normalization to MVC torque, there was no difference in RTD values

  5. Knee Extensor Mechanism Repairs: Standard Suture Repair and Novel Augmentation Technique.

    PubMed

    Meyer, Zachary; Ricci, William M

    2016-08-01

    Patellar and quadriceps tendon ruptures are relatively common injuries. Rupture of the knee extensor mechanism may occur because of a forceful eccentric contraction of the quadriceps against a resisted flexed knee, though atraumatic cases have also been described. Patients at higher than normal risk for knee extensor mechanism rupture include those with systemic co-morbidities, fluoroquinolone use, and chronic tendinopathy. Early operative treatment and mobilization of acute extensor mechanism ruptures has proven effective, and numerous techniques have been described. A 46-year-old male on anastrozole therapy simultaneously ruptured his left patellar and right quadriceps tendons during a deadlift attempt. Diagnosis was by history and physical examination. Repair of both injuries was performed 5 days after injury. Described within and shown in the accompanying video is a standard technique for primary repair using Krackow stitches through the ruptured tendon that are passed through patellar bone tunnels and tied over a bone bridge. The finer points of this technique are emphasized. Also included is a technique to augment the standard repair with a figure-of-8 stitch passed through additional oblique patellar bone tunnels. The mechanical advantage of the adjuvant figure-of-8 stitch provides additional compression, which nicely reapproximates the tendon edges. PMID:27441933

  6. Carotid Baroreflex Function During Prolonged Exercise

    NASA Technical Reports Server (NTRS)

    Raven, P. B.

    1999-01-01

    Astronauts are often required to work (exercise) at moderate to high intensities for extended periods while performing extra-vehicular activities (EVA). Although the physiologic responses associated with prolonged exercise have been documented, the mechanisms involved in blood pressure regulation under these conditions have not yet been fully elucidated. An understanding of this issue is pertinent to the ability of humans to perform work in microgravity and complies with the emphasis of NASA's Space Physiology and Countermeasures Program. Prolonged exercise at a constant workload is know to result in a progressive decrease in mean arterial pressure (MAP) concomitant with a decrease in stroke volume and a compensatory increase in heart rate. The continuous decrease in MAP during the exercise, which is related to the thermoregulatory redistribution of circulating blood volume to the cutaneous circulation, raises the question as to whether there is a loss of baroreflex regulation of arterial blood pressure. We propose that with prolongation of the exercise to 60 minutes, progressive increases on central command reflect a progressive upward resetting of the carotid baroreflex (CBR) such that the operating point of the CBR is shifted to a pressure below the threshold of the reflex rendering it ineffectual in correcting the downward drift in MAP. In order to test this hypothesis, experiments have been designed to uncouple the global hemodynamic response to prolonged exercise from the central command mediated response via: (1) continuous maintenance of cardiac filling volume by intravenous infusion of a dextran solution; and (2) whole body surface cooling to counteract thermoregulatory cutaneous vasodialation. As the type of work (exercise) performed by astronauts is inherently arm and upper body dependent, we will also examine the physiologic responses to prolonged leg cycling and arm ergometry exercise in the supine positions with and without level lower body negative

  7. Sit-to-Stand Movement in Children with Hemiplegic Cerebral Palsy: Relationship with Knee Extensor Torque and Social Participation

    ERIC Educational Resources Information Center

    dos Santos, Adriana Neves; Pavao, Silvia Leticia; Santiago, Paulo Roberto Pereira; Salvini, Tania de Fatima; Rocha, Nelci Adriana Cicuto Ferreira

    2013-01-01

    This study aimed to investigate the relationship between sit-to-stand (STS) movement, knee extensor torque and social participation in children with cerebral palsy (CP). Seven spastic hemiplegic CP patients (8.0 plus or minus 2.2 years), classified by the Gross Motor Function Classification System as I and II, and 18 typical children (8.4 plus or…

  8. Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque.

    PubMed

    Pethick, Jamie; Winter, Samantha L; Burnley, Mark

    2016-06-01

    The complexity of knee extensor torque time series decreases during fatiguing isometric muscle contractions. We hypothesized that because of peripheral fatigue, this loss of torque complexity would occur exclusively during contractions above the critical torque (CT). Nine healthy participants performed isometric knee extension exercise (6 s of contraction, 4 s of rest) on six occasions for 30 min or to task failure, whichever occurred sooner. Four trials were performed above CT (trials S1-S4, S1 being the lowest intensity), and two were performed below CT (at 50% and 90% of CT). Global, central, and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. The complexity of torque output was determined using approximate entropy (ApEn) and the detrended fluctuation analysis-α scaling exponent (DFA-α). The MVC torque was reduced in trials below CT [by 19 ± 4% (means ± SE) in 90%CT], but complexity did not decrease [ApEn for 90%CT: from 0.82 ± 0.03 to 0.75 ± 0.06, 95% paired-samples confidence intervals (CIs), 95% CI = -0.23, 0.10; DFA-α from 1.36 ± 0.01 to 1.32 ± 0.03, 95% CI -0.12, 0.04]. Above CT, substantial reductions in MVC torque occurred (of 49 ± 8% in S1), and torque complexity was reduced (ApEn for S1: from 0.67 ± 0.06 to 0.14 ± 0.01, 95% CI = -0.72, -0.33; DFA-α from 1.38 ± 0.03 to 1.58 ± 0.01, 95% CI 0.12, 0.29). Thus, in these experiments, the fatigue-induced loss of torque complexity occurred exclusively during contractions performed above the CT. PMID:27101290

  9. KNEE EXTENSOR STRENGTH EXHIBITS POTENTIAL TO PREDICT FUNCTION IN SPORADIC INCLUSION-BODY MYOSITIS

    PubMed Central

    LOWES, LINDA PAX; ALFANO, LINDSAY; VIOLLET, LAURENCE; ROSALES, XIOMARA QUINTERO; SAHENK, ZARIFE; KASPAR, BRIAN K.; CLARK, K. REED; FLANIGAN, KEVIN M.; MENDELL, JERRY R.

    2013-01-01

    Introduction In this study we address the challenging issue of potential use of muscle strength to predict function in clinical trials. This has immediate relevance to translational studies that attempt to improve quadriceps strength in sporadic inclusion-body myositis (sIBM). Methods Maximum voluntary isometric contraction testing as a measure of muscle strength and a battery of functional outcomes were tested in 85 ambulatory subjects with sIBM. Results Marked quadriceps weakness was noted in all patients. Strength was correlated with distance walked at 2 and 6 minutes. Additional correlations were found with time to get up from a chair, climb stairs, and step up on curbs. Conclusions Quadriceps (knee extensor) strength correlated with performance in this large cohort of sIBM subjects, which demonstrated its potential to predict function in this disease. These data provide initial support for use of muscle strength as a surrogate for function, although validation in a clinical trial is required. PMID:22246869

  10. Differential effects of whole body vibration durations on knee extensor strength.

    PubMed

    Stewart, James A; Cochrane, Darryl J; Morton, R Hugh

    2009-01-01

    The effectiveness and optimality of whole body vibration (WBV) duration on muscular strength is yet to be determined. Hence the aim of this study was to investigate the effects of three different durations of continuous WBV exposure on isometric right knee extensor strength measured pre and post exposure. The study involved 12 trained male subjects (age 23.7+/-4.2 years, height 1.82+/-0.06m, weight 81.8+/-15.5kg). Pre and post knee extensor strength was measured using the Biodex System 3. Peak and mean torques were recorded over three maximal 2s contractions with 10s intervals. All subjects completed three interventions of WBV lasting 2, 4, or 6min, in a balanced randomized order. Whole body vibration was performed on the Galileo machine set at 26Hz with peak-to-peak amplitude of 4mm. We found significant interaction (durationxpre-post) effects for both peak and mean torque. Two minutes of WBV provided a significantly different (p<0.05) effect (peak torque +3.8%, mean torque +3.6%) compared to 4min (-2.7% and -0.8%, respectively), and compared to 6min (-6.0% and -5.2%, respectively), while 4min produced significantly different results compared to 6min for peak torque measurements only. Two minutes of WBV produced an improvement in isometric right knee extension strength compared to 4 and 6min, both of which produced strength decreases. Nevertheless, the mechanisms and optimal dose-response character of vibration exposure remain unclear. PMID:18078783

  11. Hemiparetic Knee Extensor Strength and Balance Function Are Predictors of Ambulatory Function in Subacute Stroke Patients

    PubMed Central

    Hyun, Chul Woong; Im, Sang Hee; Choi, Jay Chol; Kim, Bo Ryun; Yoon, Ho Min; Lee, Yong Ki

    2015-01-01

    Objective To identify the potential predictors of ambulatory function in subacute stroke patients, and to determine the contributing factors according to gait severity. Methods Fifty-three subacute stroke patents were enrolled. Ambulatory function was assessed by gait speed and endurance. Balance function was evaluated by the Berg Balance Scale score (BBS) and the Timed Up and Go test (TUG). The isometric muscular strengths of bilateral knee extensors and flexors were measured using an isokinetic dynamometer. Cardiovascular fitness was evaluated using an expired gas analyzer. Participants were assigned into the household ambulator group (<0.4 m/s) or the community ambulator group (≥0.4 m/s) based on gait severity. Results In the linear regression analyses of all patients, paretic knee isometric extensor strength (p=0.007) and BBS (p<0.001) were independent predictors of gait endurance (R2=0.668). TUG (p<0.001) and BBS (p=0.037) were independent predictors of gait speed (R2=0.671). Paretic isometric extensor strength was a predictor of gait endurance (R2=0.340, p=0.008). TUG was a predictor of gait speed (R2=0.404, p<0.001) in the household ambulator group, whereas BBS was a predictive factor of gait endurance (R2=0.598, p=0.008) and speed (R2=0.713, p=0.006). TUG was a predictor of gait speed (R2=0.713, p=0.004) in the community ambulator group. Conclusion Our results reveal that balance function and knee extensor isometric strength were strong predictors of ambulatory function in subacute stroke patients. However, they work differently according to gait severity. Therefore, a comprehensive functional assessment and a different therapeutic approach should be provided depending on gait severity in subacute stroke patients. PMID:26361594

  12. β-alanine supplementation improves isometric endurance of the knee extensor muscles

    PubMed Central

    2012-01-01

    Background We examined the effect of four weeks of β-alanine supplementation on isometric endurance of the knee extensors at 45% maximal voluntary isometric contraction (MVIC). Methods Thirteen males (age 23 ± 6 y; height 1.80 ± 0.05 m; body mass 81.0 ± 10.5 kg), matched for pre-supplementation isometric endurance, were allocated to either a placebo (n = 6) or β-alanine (n = 7; 6.4 g·d-1 over 4 weeks) supplementation group. Participants completed an isometric knee extension test (IKET) to fatigue, at an intensity of 45% MVIC, before and after supplementation. In addition, two habituation tests were completed in the week prior to the pre-supplementation test and a further practice test was completed in the week prior to the post-supplementation test. MVIC force, IKET hold-time, and impulse generated were recorded. Results IKET hold-time increased by 9.7 ± 9.4 s (13.2%) and impulse by 3.7 ± 1.3 kN·s-1 (13.9%) following β-alanine supplementation. These changes were significantly greater than those in the placebo group (IKET: t(11) = 2.9, p ≤0.05; impulse: t(11) = 3.1, p ≤ 0.05). There were no significant changes in MVIC force in either group. Conclusion Four weeks of β-alanine supplementation at 6.4 g·d-1 improved endurance capacity of the knee extensors at 45% MVIC, which most likely results from improved pH regulation within the muscle cell as a result of elevated muscle carnosine levels. PMID:22697405

  13. Human muscle function following prolonged eccentric exercise.

    PubMed

    Sargeant, A J; Dolan, P

    1987-01-01

    4 subjects performed repeated eccentric contractions with leg extensors during prolonged downhill walking (-25% gradient) at 6.44 km.h-1 until collapse due to muscle weakness (range of exercise duration 29 to 40 min). During the exercise oxygen uptake rose progressively from approximately 45% of the previously determined VO2max at 10 min to approximately 65% at the end of the exercise. Following the exercise there was an immediate, significant, and sustained reduction in maximal voluntary isometric contraction, and short term (anaerobic) power output measured concentrically on an isokinetic ergometer. These reductions in muscle function persisted for 96 hours post exercise, and were reflected by significant reductions in the tension generated at low frequency (20 Hz) relative to higher frequency (50 Hz) percutaneous stimulation of the quadriceps. All four subjects showed an increase in plasma levels of creatine kinase post eccentric exercise. Performing concentric contractions by walking uphill for one hour at a significantly greater metabolic cost failed to induce comparable reductions in muscle function. These results provide evidence for the consequences of prolonged eccentric work upon dynamic function which complements earlier reports of structural, enzymatic, and static function changes. PMID:3678226

  14. Brain glycogen decreases during prolonged exercise

    PubMed Central

    Matsui, Takashi; Soya, Shingo; Okamoto, Masahiro; Ichitani, Yukio; Kawanaka, Kentaro; Soya, Hideaki

    2011-01-01

    Abstract Brain glycogen could be a critical energy source for brain activity when the glucose supply from the blood is inadequate (hypoglycaemia). Although untested, it is hypothesized that during prolonged exhaustive exercise that induces hypoglycaemia and muscular glycogen depletion, the resultant hypoglycaemia may cause a decrease in brain glycogen. Here, we tested this hypothesis and also investigated the possible involvement of brain monoamines with the reduced levels of brain glycogen. For this purpose, we exercised male Wistar rats on a treadmill for different durations (30–120 min) at moderate intensity (20 m min−1) and measured their brain glycogen levels using high-power microwave irradiation (10 kW). At the end of 30 and 60 min of running, the brain glycogen levels remained unchanged from resting levels, but liver and muscle glycogen decreased. After 120 min of running, the glycogen levels decreased significantly by ∼37–60% in five discrete brain loci (the cerebellum 60%, cortex 48%, hippocampus 43%, brainstem 37% and hypothalamus 34%) compared to those of the sedentary control. The brain glycogen levels in all five regions after running were positively correlated with the respective blood and brain glucose levels. Further, in the cortex, the levels of methoxyhydroxyphenylglycol (MHPG) and 5-hydroxyindoleacetic acid (5-HIAA), potential involved in degradation of the brain glycogen, increased during prolonged exercise and negatively correlated with the glycogen levels. These results support the hypothesis that brain glycogen could decrease with prolonged exhaustive exercise. Increased monoamines together with hypoglycaemia should be associated with the development of decreased brain glycogen, suggesting a new clue towards the understanding of central fatigue during prolonged exercise. PMID:21521757

  15. Mental fatigue induced by prolonged self-regulation does not exacerbate central fatigue during subsequent whole-body endurance exercise

    PubMed Central

    Pageaux, Benjamin; Marcora, Samuele M.; Rozand, Vianney; Lepers, Romuald

    2015-01-01

    It has been shown that the mental fatigue induced by prolonged self-regulation increases perception of effort and reduces performance during subsequent endurance exercise. However, the physiological mechanisms underlying these negative effects of mental fatigue are unclear. The primary aim of this study was to test the hypothesis that mental fatigue exacerbates central fatigue induced by whole-body endurance exercise. Twelve subjects performed 30 min of either an incongruent Stroop task to induce a condition of mental fatigue or a congruent Stroop task (control condition) in a random and counterbalanced order. Both cognitive tasks (CTs) were followed by a whole-body endurance task (ET) consisting of 6 min of cycling exercise at 80% of peak power output measured during a preliminary incremental test. Neuromuscular function of the knee extensors was assessed before and after CT, and after ET. Rating of perceived exertion (RPE) was measured during ET. Both CTs did not induce any decrease in maximal voluntary contraction (MVC) torque (p = 0.194). During ET, mentally fatigued subjects reported higher RPE (mental fatigue 13.9 ± 3.0, control 13.3 ± 3.2, p = 0.044). ET induced a similar decrease in MVC torque (mental fatigue –17 ± 15%, control –15 ± 11%, p = 0.001), maximal voluntary activation level (mental fatigue –6 ± 9%, control –6 ± 7%, p = 0.013) and resting twitch (mental fatigue –30 ± 14%, control –32 ± 10%, p < 0.001) in both conditions. These findings reject our hypothesis and confirm previous findings that mental fatigue does not reduce the capacity of the central nervous system to recruit the working muscles. The negative effect of mental fatigue on perception of effort does not reflect a greater development of either central or peripheral fatigue. Consequently, mentally fatigued subjects are still able to perform maximal exercise, but they are experiencing an altered performance during submaximal exercise due to higher

  16. Fatigue reduces the complexity of knee extensor torque fluctuations during maximal and submaximal intermittent isometric contractions in man

    PubMed Central

    Pethick, Jamie; Winter, Samantha L; Burnley, Mark

    2015-01-01

    Neuromuscular fatigue increases the amplitude of fluctuations in torque output during isometric contractions, but the effect of fatigue on the temporal structure, or complexity, of these fluctuations is not known. We hypothesised that fatigue would result in a loss of temporal complexity and a change in fractal scaling of the torque signal during isometric knee extensor exercise. Eleven healthy participants performed a maximal test (5 min of intermittent maximal voluntary contractions, MVCs), and a submaximal test (contractions at a target of 40% MVC performed until task failure), each with a 60% duty factor (6 s contraction, 4 s rest). Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling of torque were quantified by calculating approximate entropy (ApEn), sample entropy (SampEn) and the detrended fluctuation analysis (DFA) scaling exponent α. Fresh submaximal contractions were more complex than maximal contractions (mean ± SEM, submaximal vs. maximal: ApEn 0.65 ± 0.09 vs. 0.15 ± 0.02; SampEn 0.62 ± 0.09 vs. 0.14 ± 0.02; DFA α 1.35 ± 0.04 vs. 1.55 ± 0.03; all P < 0.005). Fatigue reduced the complexity of submaximal contractions (ApEn to 0.24 ± 0.05; SampEn to 0.22 ± 0.04; DFA α to 1.55 ± 0.03; all P < 0.005) and maximal contractions (ApEn to 0.10 ± 0.02; SampEn to 0.10 ± 0.02; DFA α to 1.63 ± 0.02; all P < 0.01). This loss of complexity and shift towards Brownian-like noise suggests that as well as reducing the capacity to produce torque, fatigue reduces the neuromuscular system's adaptability to external perturbations. PMID:25664928

  17. Severe COPD Alters Muscle Fiber Conduction Velocity During Knee Extensors Fatiguing Contraction.

    PubMed

    Boccia, Gennaro; Coratella, Giuseppe; Dardanello, Davide; Rinaldo, Nicoletta; Lanza, Massimo; Schena, Federico; Rainoldi, Alberto

    2016-10-01

    The aim of this study was to assess the changes in muscle fiber conduction velocity (CV), as a sign of fatigue during knee extensor contraction in patients with chronic obstructive pulmonary disease (COPD) as compared with healthy controls. Eleven male patients (5 with severe and 6 with moderate COPD; age 67 ± 5 years) and 11 age-matched healthy male controls (age 65 ± 4 years) volunteered for the study. CV was obtained by multichannel surface electromyography (EMG) from the vastus lateralis (VL) and medialis (VM) of the quadriceps muscle during isometric, 30-second duration knee extension at 70% of maximal voluntary contraction. The decline in CV in both the VL and VM was steeper in the severe COPD patients than in healthy controls (for VL: severe COPD vs. controls -0.45 ± 0.07%/s; p < 0.001, and for VM: severe COPD vs. controls -0.54 ± 0.09%/s, p < 0.001). No difference in CV decline was found between the moderate COPD patients and the healthy controls. These findings suggest that severe COPD may impair muscle functions, leading to greater muscular fatigue, as expressed by CV changes. The results may be due to a greater involvement of anaerobic metabolism and a shift towards fatigable type II fibers in the muscle composition of the severe COPD patients. PMID:27007486

  18. Effect of mental fatigue on induced tremor in human knee extensors.

    PubMed

    Budini, Francesco; Lowery, Madeleine; Durbaba, Rade; De Vito, Giuseppe

    2014-06-01

    In this study, the effects of mental fatigue on mechanically induced tremor at both a low (3-6Hz) and high (8-12Hz) frequency were investigated. The two distinct tremor frequencies were evoked using two springs of different stiffness, during 20s sustained contractions of the knee extensor muscles at 30% maximum voluntary contraction (MVC) before and after 100min of a mental fatigue task, in 12 healthy (29±3.7years) participants. Mental fatigue resulted in a 6.9% decrease in MVC and in a 9.4% decrease in the amplitude of the agonist muscle EMG during sustained 30% MVC contractions in the induced high frequency only. Following the mental fatigue task, the coefficient of variation and standard deviation of the force signal decreased at 8-12Hz induced tremor by 31.7% and 35.2% respectively, but not at 3-6Hz induced tremor. Similarly, the maximum value and area underneath the peak in the power spectrum of the force signal decreased by 55.5% and 53.1% respectively in the 8-12Hz range only. In conclusion, mental fatigue decreased mechanically induced 8-12Hz tremor and had no effect on induced 3-6Hz tremor. We suggest that the reduction could be attributed to the decreased activation of the agonist muscles. PMID:24613661

  19. Modulation of recurrent inhibition from knee extensors to ankle motoneurones during human walking

    PubMed Central

    Lamy, Jean-Charles; Iglesias, Caroline; Lackmy, Alexandra; Nielsen, Jens Bo; Katz, Rose; Marchand-Pauvert, Véronique

    2008-01-01

    The neural control for muscle coordination during human locomotion involves spinal and supraspinal networks, but little is known about the exact mechanisms implicated. The present study focused on modulation of heteronymous recurrent inhibition from knee extensors to ankle motoneurones at different times in the gait cycle, when quadriceps (Quad) muscle activity overlaps that in tibialis anterior (TA) and soleus (Sol). The effects of femoral nerve stimulation on ankle motoneurones were investigated during treadmill walking and during tonic co-contraction of Quad and TA/Sol while standing. Recurrent inhibition of TA motoneurones depended on the level of background EMG, and was similar during walking and standing for matched background EMG levels. On the other hand, recurrent inhibition in Sol was reduced in early stance, with respect to standing, and enhanced in late stance. Reduced inhibition in Sol was also observed when Quad was coactivated with TA around the time of heel contact, compared to standing at matched background EMG levels in the two muscles. The modulation of recurrent inhibition of Sol during walking might reflect central and/or peripheral control of the Renshaw cells. These modulations could be implicated in the transition phases, from swing to stance to assist Sol activation during the stance phase, and from stance to swing, for its deactivation. PMID:18936080

  20. Isokinetic dynamometry of the knee extensors and flexors in Iranian healthy males and females

    PubMed Central

    Rezaei, Mandana; Ebrahimi, Ismael; Vassaghi- Gharamaleki, Behnoush; Pirali, Milad; Mortaza, Niyousha; Malmir, Kazem; Ghasemi, Kobra; A. Jamshidi, Ali

    2014-01-01

    Background: This paper explores the gender-related bilateral differences of extensor and flexor torques of the knee joint at low and high angular velocities in Iranian healthy males and females. Methods: 70 healthy subjects (29 males (26.61±4.34 yrs and 41 females with average age of 23.07±3.70 yrs)) were participated in this study. Isokinetic peak torque values for knee extensors and flexors in concentric and eccentric contraction modes were measured and flexors and extensors strength ratios (HQR) computed among both dominant and non-dominant legs in lying position at 60 and 180°.s-1angular velocities. Results: There was significant gender-velocity interactions detected for knee flexor to extensor strength ratios presenting that increasing velocity escaled this, ratios in females more than males (p<0.05). There was no gender- velocity-leg side interaction (p>0.05). Bilateral differences were found for eccentric flexor peak torques (p<0.05). By increasing velocity, peak torque values decreased and HQR was increased (p<0.05). Conclusion: Measurement procedures including test position is an important factor when interpreting genderrelated and bilateral differences of isokinetic knee strength ratios in healthy individuals. PMID:25664309

  1. The effects of isometric resistance training on stretch reflex induced tremor in the knee extensor muscles.

    PubMed

    Durbaba, Rade; Cassidy, Angela; Budini, Francesco; Macaluso, Andrea

    2013-06-15

    This study examines the effect of 4 wk of high-intensity isometric resistance training on induced tremor in knee extensor muscles. Fourteen healthy volunteers were assigned to either the training group (n = 7) or the nontraining control group (n = 7). Induced tremor was assessed by measuring force fluctuations during anisometric contractions against spring loading, whose compliance was varied to allow for preferential activation of the short or long latency stretch reflex components. Effects of high-intensity isometric resistance training on induced tremor was assessed under two contraction conditions: relative force matching, where the relative level of activity was equal for both pre- and post-training sessions, set at 30% maximum voluntary contraction (MVC), and absolute force matching, where the level of activity was set to 30% pretrained MVC. The training group experienced a 26.5% increase in MVC in contrast to the 0.8% for the control group. For relative force-matching contractions, induced tremor amplitude and frequency did not change in either the training or control group. During absolute force-matching contractions, induced tremor amplitude was decreased by 37.5% and 31.6% for the short and long components, respectively, with no accompanying change in frequency, for the training group. No change in either measure was observed in the control group for absolute force-matching contractions. The results are consistent with high-intensity isometric resistance training induced neural changes leading to increased strength, coupled with realignment of stretch reflex automatic gain compensation to the new maximal force output. Also, previous reported reductions in anisometric tremor following strength training may partly be due to changed stretch reflex behavior. PMID:23580599

  2. Relationship of body composition, knee extensor strength, and standing balance to lumbar bone mineral density in postmenopausal females

    PubMed Central

    Shin, Seungsub; Lee, Kyeongjin; Song, Changho

    2016-01-01

    [Purpose] This study aimed to investigate correlations between lumbar bone mineral density (BMD) and general characteristics of postmenopausal females, including body composition, knee extensor strength, standing balance, and femur BMD. [Subjects and Methods] A total of 40 postmenopausal females (55.6 ± 4.6 years) who were caregivers or guardians of patients in the K hospital were included in the study. The weight, height, body composition, left and right knee extensor strength, standing balance, femur BMD, and lumbar BMD measurements of the subjects were obtained. [Results] The effect of measurement variables on lumbar BMD was examined. Increases in age and menopausal duration were observed to significantly increase lumbar BMD, whereas an increase in height was found to significantly decrease lumbar BMD. An increase in soft lean mass, skeletal muscle mass, fat-free mass, and femur BMD was also associated with significantly decreased lumbar BMD. [Conclusion] Age, menopausal duration, soft lean mass, skeletal muscle mass, and fat-free mass were factors that decreased lumbar BMD in menopausal females. This study is expected to provide basic knowledge for osteoporosis prevention and treatment programs for postmenopausal females. PMID:27512276

  3. Relationship of body composition, knee extensor strength, and standing balance to lumbar bone mineral density in postmenopausal females.

    PubMed

    Shin, Seungsub; Lee, Kyeongjin; Song, Changho

    2016-07-01

    [Purpose] This study aimed to investigate correlations between lumbar bone mineral density (BMD) and general characteristics of postmenopausal females, including body composition, knee extensor strength, standing balance, and femur BMD. [Subjects and Methods] A total of 40 postmenopausal females (55.6 ± 4.6 years) who were caregivers or guardians of patients in the K hospital were included in the study. The weight, height, body composition, left and right knee extensor strength, standing balance, femur BMD, and lumbar BMD measurements of the subjects were obtained. [Results] The effect of measurement variables on lumbar BMD was examined. Increases in age and menopausal duration were observed to significantly increase lumbar BMD, whereas an increase in height was found to significantly decrease lumbar BMD. An increase in soft lean mass, skeletal muscle mass, fat-free mass, and femur BMD was also associated with significantly decreased lumbar BMD. [Conclusion] Age, menopausal duration, soft lean mass, skeletal muscle mass, and fat-free mass were factors that decreased lumbar BMD in menopausal females. This study is expected to provide basic knowledge for osteoporosis prevention and treatment programs for postmenopausal females. PMID:27512276

  4. Effect of acute dietary nitrate intake on maximal knee extensor speed and power in healthy men and women.

    PubMed

    Coggan, Andrew R; Leibowitz, Joshua L; Kadkhodayan, Ana; Thomas, Deepak P; Ramamurthy, Sujata; Spearie, Catherine Anderson; Waller, Suzanne; Farmer, Marsha; Peterson, Linda R

    2015-08-01

    Nitric oxide (NO) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle. Dietary nitrate (NO3(-)) intake has been demonstrated to increase NO bioavailability in humans. We therefore hypothesized that acute dietary NO3(-) intake (in the form of a concentrated beetroot juice (BRJ) supplement) would improve muscle speed and power in humans. To test this hypothesis, healthy men and women (n = 12; age = 22-50 y) were studied using a randomized, double-blind, placebo-controlled crossover design. After an overnight fast, subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO3(-). After 2 h, knee extensor contractile function was assessed using a Biodex 4 isokinetic dynamometer. Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole-body NO production. No significant changes in breath NO were observed in the placebo trial, whereas breath NO rose by 61% (P < 0.001; effect size = 1.19) after dietary NO3(-) intake. This was accompanied by a 4% (P < 0.01; effect size = 0.74) increase in peak knee extensor power at the highest angular velocity tested (i.e., 6.28 rad/s). Calculated maximal knee extensor power was therefore greater (i.e., 7.90 ± 0.59 vs. 7.44 ± 0.53 W/kg; P < 0.05; effect size = 0.63) after dietary NO3(-) intake, as was the calculated maximal velocity (i.e., 14.5 ± 0.9 vs. 13.1 ± 0.8 rad/s; P < 0.05; effect size = 0.67). No differences in muscle function were observed during 50 consecutive knee extensions performed at 3.14 rad/s. We conclude that acute dietary NO3(-) intake increases whole-body NO production and muscle speed and power in healthy men and women. PMID:25199856

  5. Effect of acute dietary nitrate intake on maximal knee extensor speed and power in healthy men and women

    PubMed Central

    Coggan, Andrew R.; Leibowitz, Joshua L.; Kadkhodayan, Ana; Thomas, Deepak T.; Ramamurthy, Sujata; Spearie, Catherine Anderson; Waller, Suzannea; Farmer, Marsha; Peterson, Linda R.

    2014-01-01

    Nitric oxide (NO) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle. Dietary nitrate (NO3-) intake has been demonstrated to increase NO bioavailability in humans. We therefore hypothesized that acute dietary NO3- intake (in the form of a concentrated beetroot juice (BRJ) supplement) would improve muscle speed and power in humans. To test this hypothesis, healthy men and women (n=12; age=22-50 y) were studied using a randomized, double-blind, placebo-controlled crossover design. After an overnight fast, subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO3-. After 2 h, knee extensor contractile function was assessed using a Biodex 4 isokinetic dynamometer. Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole-body NO production. No significant changes in breath NO were observed in the placebo trial, whereas breath NO rose by 61% (P<0.001; effect size=1.19) after dietary NO3- intake. This was accompanied by a 4% (P<0.01; effect size=0.74) increase in peak knee extensor power at the highest angular velocity tested (i.e., 6.28 rad/s). Calculated maximal knee extensor power was therefore greater (i.e., 7.90±0.59 vs. 7.44±0.53 W/kg; P<0.05; effect size=0.63) after dietary NO3- intake, as was the calculated maximal velocity (i.e., 14.5±0.9 vs. 13.1±0.8 rad/s; P<0.05; effect size=0.67). No differences in muscle function were observed during 50 consecutive knee extensions performed at 3.14 rad/s. We conclude that acute dietary NO3- intake increases whole-body NO production and muscle speed and power in healthy men and women. PMID:25199856

  6. Effects Of Exercise During Prolonged Bed Rest

    NASA Technical Reports Server (NTRS)

    Arnaud, S.; Berry, P; Cohen, M.; Danelis, J.; Deroshia, C.; Greenleaf, J.; Harris, B.; Keil, L.; Bernauer, E.; Bond, M.; Ellis, S.; Lee, P.; Selzer, R.; Wade, C.

    1992-01-01

    Report describes experiment to investigate effects of isotonic and isokinetic leg exercises in counteracting effects of bed rest upon physical and mental conditions of subjects. Data taken on capacity for work, endurance and strength, tolerance to sitting up, equilibrium, posture, gait, atrophy, mineralization and density of bones, endocrine analyses concerning vasoactivity and fluid and electrolyte balances, intermediary metabolism of muscles, mood, and performance.

  7. Maximal aerobic exercise following prolonged sleep deprivation.

    PubMed

    Goodman, J; Radomski, M; Hart, L; Plyley, M; Shephard, R J

    1989-12-01

    The effect of 60 h without sleep upon maximal oxygen intake was examined in 12 young women, using a cycle ergometer protocol. The arousal of the subjects was maintained by requiring the performance of a sequence of cognitive tasks throughout the experimental period. Well-defined oxygen intake plateaus were obtained both before and after sleep deprivation, and no change of maximal oxygen intake was observed immediately following sleep deprivation. The endurance time for exhausting exercise also remained unchanged, as did such markers of aerobic performance as peak exercise ventilation, peak heart rate, peak respiratory gas exchange ratio, and peak blood lactate. However, as in an earlier study of sleep deprivation with male subjects (in which a decrease of treadmill maximal oxygen intake was observed), the formula of Dill and Costill (4) indicated the development of a substantial (11.6%) increase of estimated plasma volume percentage with corresponding decreases in hematocrit and red cell count. Possible factors sustaining maximal oxygen intake under the conditions of the present experiment include (1) maintained arousal of the subjects with no decrease in peak exercise ventilation or the related respiratory work and (2) use of a cycle ergometer rather than a treadmill test with possible concurrent differences in the impact of hematocrit levels and plasma volume expansion upon peak cardiac output and thus oxygen delivery to the working muscles. PMID:2628360

  8. Effects of strength training program on hip extensors and knee extensors strength of lower limb in children with spastic diplegic cerebral palsy

    PubMed Central

    Aye, Thanda; Thein, Soe; Hlaing, Thaingi

    2016-01-01

    [Purpose] The purpose of this study was to determine whether strength training programs for hip extensors and knee extensors improve gross motor function of children with cerebral palsy in Myanmar. [Subjects and Methods] Forty children (25 boys and 15 girls, mean age: 6.07 ± 2.74 years) from National Rehabilitation Hospital, Yangon, Myanmar, who had been diagnosed with spastic diplegic cerebral palsy, Gross Motor Classification System I and II participated in a 6-week strength training program (45 minutes per day, 3 days per week) on hip and knee extensors. Assessment was made, before and after intervention, of the amount of training weight in pounds, as well as Gross Motor Function Measure (GMFM) dimensions D (standing) and E (walking, running, jumping). [Results] All scores had increased significantly after the strength-training program. [Conclusion] A simple method of strength-training program for hip and knee extensors might lead to improved muscle strength and gross motor function in children with spastic diplegic cerebral palsy. PMID:27065561

  9. Breathing during prolonged exercise in humans.

    PubMed Central

    Kearon, M C; Summers, E; Jones, N L; Campbell, E J; Killian, K J

    1991-01-01

    1. Six normal subjects cycled to endurance or for 60 min at four work rates (WR 1-4): mean of 34% working capacity (93 watts for 60 min); 43% (120 watts for 56 min); 63% (177 watts for 37 min); and 84% (233 watts for 12 min), to determine how breathing pattern and dyspnoea change during prolonged activity. Four to six minutes were allowed to establish steady state and subsequent changes were considered to be endurance related. 2. Dyspnoea (Borg scale, 0-10) increased with the duration of activity at all work rates. 3. Ventilation (VE) did not change at WR1; increased from 44 to 47 l min-1 at WR2; from 60 to 88 l min-1 at WR3; and from 111 to 132 l min-1 at WR4. Dyspnoea was significantly and independently related to ventilation and duration of activity: dyspnoea = 0.004 VE1.36 time 0.25 (r = 0.81; partial F 202 and 26 respectively). 4. Inspiratory resistance did not increase at any work rate. Dynamic elastance remained constant during WR1, WR2 and WR3 but increased from 7.4 to 9.1 cmH2O l-1 during WR4. 5. Peak inspiratory pressure did not increase, and the increase in VE was accomplished by an increased breathing frequency without change in duty cycle. 6. Duration of activity is an important contributor to dyspnoea independent of changes in respiratory muscle contractile activity. PMID:1798038

  10. Low-level intermittent quadriceps activity during transcranial direct current stimulation facilitates knee extensor force-generating capacity.

    PubMed

    Washabaugh, Edward P; Santos, Luciana; Claflin, Edward S; Krishnan, Chandramouli

    2016-08-01

    Anodal transcranial direct current stimulation (tDCS) is known to increase the force-generating capacity of the skeletal muscles. However, when tDCS is concurrently combined with a motor task, interference may occur that hinders tDCS effects. Here, we tested the interaction and time course of tDCS effects on force production when paired with a low-level force-matching task. Twenty-two subjects were randomized into two groups: tDCS-Matching and tDCS-Resting. Each group received tDCS and a sham stimulation, separated by one week. Maximal knee extensor and flexor torques were measured before and up to twenty-five minutes following the stimulation. The tDCS-Matching group produced greater knee extension torques relative to sham when compared with the tDCS-Resting group. There was no significant effect for knee flexion. This suggests that interference does not occur for force production tasks when tDCS is combined with a motor task. Rather, the task appears to aid and isolate the effects to the muscle groups involved in the task. PMID:27138643

  11. Effects of isokinetic training of the knee extensors on isometric strength and peak power output during cycling.

    PubMed

    Mannion, A F; Jakeman, P M; Willan, P L

    1992-01-01

    Isokinetic training of right and left quadriceps femoris was undertaken three times per week for 16 weeks. One group of subjects (n = 13) trained at an angular velocity of 4.19 rad.s-1 and a second group (n = 10) at 1.05 rad.s-1. A control group (n = 10) performed no training. Maximal voluntary contraction (MVC) of the quadriceps, and peak pedal velocity nu p,peak) and peak power output (Wpeak) during all-out cycling (against loads equivalent to 9, 10, 11, 12, 13 and 14% MVC) were assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of the performance variables (P > 0.05). No significant difference in MVC was observed for any group after the 16-week period (P = 0.167). The post-training increases in average Wpeak (7%) and nu p,peak (6%) during the cycle tests were each significantly different from the control group response (P = 0.018 and P = 0.008, respectively). It is concluded that 16 weeks of isokinetic strength training of the knee extensors is able to significantly improve nu p, peak and Wpeak during spring cycling, an activity which demands considerable involvement of the trained muscle group but with its own distinct pattern of coordination. PMID:1425638

  12. Cerebral ammonia uptake and accumulation during prolonged exercise in humans

    PubMed Central

    Nybo, Lars; Dalsgaard, Mads K; Steensberg, Adam; Møller, Kirsten; Secher, Niels H

    2005-01-01

    We evaluated whether peripheral ammonia production during prolonged exercise enhances the uptake and subsequent accumulation of ammonia within the brain. Two studies determined the cerebral uptake of ammonia (arterial and jugular venous blood sampling combined with Kety–Schmidt-determined cerebral blood flow; n = 5) and the ammonia concentration in the cerebrospinal fluid (CSF; n = 8) at rest and immediately following prolonged exercise either with or without glucose supplementation. There was a net balance of ammonia across the brain at rest and at 30 min of exercise, whereas 3 h of exercise elicited an uptake of 3.7 ± 1.3 μmol min−1 (mean ±s.e.m.) in the placebo trial and 2.5 ± 1.0 μmol min−1 in the glucose trial (P < 0.05 compared to rest, not different across trials). At rest, CSF ammonia was below the detection limit of 2 μm in all subjects, but it increased to 5.3 ± 1.1 μm following exercise with glucose, and further to 16.1 ± 3.3 μm after the placebo trial (P < 0.05). Correlations were established between both the cerebral uptake (r2 = 0.87; P < 0.05) and the CSF concentration (r2 = 0.72; P < 0.05) and the arterial ammonia level and, in addition, a weaker correlation (r2 = 0.37; P < 0.05) was established between perceived exertion and CSF ammonia at the end of exercise. The results let us suggest that during prolonged exercise the cerebral uptake and accumulation of ammonia may provoke fatigue, e.g. by affecting neurotransmitter metabolism. PMID:15611036

  13. Exercise as a countermeasure for physiological adaptation to prolonged spaceflight.

    PubMed

    Convertino, V A

    1996-08-01

    Exercise represents the primary countermeasure used during spaceflight to maintain or restore maximal aerobic capacity (VO2max), musculoskeletal structure, and orthostatic function. However, no single exercise or combination of prescriptions has proven entirely effective in restoring cardiovascular and musculoskeletal functions to preflight levels following prolonged spaceflight. As human spaceflight exposures increase in duration, assessment and development of various effective exercise-based protective procedures become paramount. This must involve improvement in specific countermeasure prescription as well as development of additional approaches that will allow space travelers greater flexibility and medical safety during long flights. Effective exercise prescription will be based on identification of basic physiological stimuli that maintain normal function in terrestrial gravity and understanding of how specific combinations of exercise characteristics e.g., duration, frequency, intensity, mode) can mimic these stimuli and affect the overall process of adaptation to microgravity. This can be accomplished only with greater emphasis of research on ground-based experiments. Future attention must be directed to improving exercise compliance while minimizing both crew time and the impact of the exercise on life-support resources. PMID:8871910

  14. Exercise as a countermeasure for physiological adaptation to prolonged spaceflight

    NASA Technical Reports Server (NTRS)

    Convertino, V. A.

    1996-01-01

    Exercise represents the primary countermeasure used during spaceflight to maintain or restore maximal aerobic capacity (VO2max), musculoskeletal structure, and orthostatic function. However, no single exercise or combination of prescriptions has proven entirely effective in restoring cardiovascular and musculoskeletal functions to preflight levels following prolonged spaceflight. As human spaceflight exposures increase in duration, assessment and development of various effective exercise-based protective procedures become paramount. This must involve improvement in specific countermeasure prescription as well as development of additional approaches that will allow space travelers greater flexibility and medical safety during long flights. Effective exercise prescription will be based on identification of basic physiological stimuli that maintain normal function in terrestrial gravity and understanding of how specific combinations of exercise characteristics e.g., duration, frequency, intensity, mode) can mimic these stimuli and affect the overall process of adaptation to microgravity. This can be accomplished only with greater emphasis of research on ground-based experiments. Future attention must be directed to improving exercise compliance while minimizing both crew time and the impact of the exercise on life-support resources.

  15. Influence of length-restricted strength training on athlete's power-load curves of knee extensors and flexors.

    PubMed

    Ullrich, Boris; Kleinöder, Heinz; Brüggemann, Gert-Peter

    2010-03-01

    This study investigated whether different length-restricted strength training regimens affect voluntary explosive concentric power-load curves of the quadriceps femoris (QF) and hamstring (HAM) muscles. Thirty-two athletes were divided into 3 different training groups (G1-G3): G1 performed isometric training at knee joint angles corresponding to long muscle-tendon unit (MTU) length for QF and HAM; G2 conducted concentric-eccentric contraction cycles that were restricted to a knee joint range of motion corresponding to predominantly long MTU length for QF and HAM; and G3 combined the protocols of G1 and G2. Knee joint angle-dependent power-load curves during maximal voluntary explosive concentric knee extensions and flexions were measured for loads corresponding to 40, 60, and 80% of individual 1 repetition maximum at 5 different occasions: 2 times before, after 5 and 8 weeks of training, and 4 weeks post training. Power values of each subject were normalized to the largest value produced at any knee joint position (percent maximum). Obtained by curve fitting, the optimal knee joint angle for power production of QF and HAM remained unaltered throughout the course of the study for all testing loads and training groups. Therefore, different strength training regimens with a common restriction to long MTU lengths failed to induce length-dependent alterations in athlete's voluntary concentric power-load curves of knee extensors and flexors. The approach to develop strength training programs that induce systematic shifts in length-dependent power production of QF and HAM is of direct practical relevance for athletic activities such as cycling, ice skating, and skiing. However, restricting the muscle excursion range during loading seems to be an inappropriate trigger to cause length-dependent alterations in athlete's voluntary concentric power-load curves. PMID:20145573

  16. Effects of Between-Set Interventions on Neuromuscular Function During Isokinetic Maximal Concentric Contractions of the Knee Extensors

    PubMed Central

    Cometti, Carole; Deley, Gaelle; Babault, Nicolas

    2011-01-01

    The presents study investigated the effects of between-set interventions on neuromuscular function of the knee extensors during six sets of 10 isokinetic (120°·s-1) maximal concentric contractions separated by three minutes. Twelve healthy men (age: 23.9 ± 2.4 yrs) were tested for four different between-set recovery conditions applied during two minutes: passive recovery, active recovery (cycling), electromyostimulation and stretching, in a randomized, crossover design. Before, during and at the end of the isokinetic session, torque and thigh muscles electromyographic activity were measured during maximal voluntary contractions and electrically-evoked doublets. Activation level was calculated using the twitch interpolation technique. While quadriceps electromyographic activity and activation level were significantly decreased at the end of the isokinetic session (-5.5 ± 14.2 % and -2.7 ± 4.8 %; p < 0.05), significant decreases in maximal voluntary contractions and doublets were observed after the third set (respectively -0.8 ± 12.1% and -5.9 ± 9.9%; p < 0.05). Whatever the recovery modality applied, torque was back to initial values after each recovery period. The present results showed that fatigue appeared progressively during the isokinetic session with peripheral alterations occurring first followed by central ones. Recovery interventions between sets did not modify fatigue time course as compared with passive recovery. It appears that the interval between sets (3 min) was long enough to provide recovery regardless of the interventions. Key points Allowing three minutes of recovery between sets of 10 maximal concentric contractions would help the subjects to recover from the peripheral fatigue induced by each set and therefore to start each new set with a high intensity. During this type of session, with three minutes between sets, passive recovery is sufficient; there is no need to apply complicated recovery interventions. PMID:24149550

  17. Neuromuscular adjustments of the knee extensors and plantar flexors following match-play tennis in the heat

    PubMed Central

    Périard, Julien D; Girard, Olivier; Racinais, Sébastien

    2014-01-01

    Objectives This study tested the hypothesis that impairments in lower limb maximal strength and voluntary activation (VA) are exacerbated following match-play tennis in hot compared with cool conditions. Methods Torque and VA were evaluated during brief (5 s) and sustained (20 s) maximal voluntary isometric contractions of the knee extensors (KE) and plantar flexors (PF) in 12 male tennis players before (pre) and after (post, 24 h and 48 h) ∼115 min of play in hot (∼37°C) and cool (∼22°C) conditions. Results Rectal temperature was higher following play in hot than in cool (∼39.2 vs ∼38.5°C; p<0.05). Torque production decreased from prematch to postmatch during the brief and sustained contractions in hot (KE: ∼22%; PF: ∼13%) and cool (KE: ∼9%, PF: ∼7%) (p<0.05). KE strength losses in hot were greater than in cool (p<0.05) and persisted for 24 h (p<0.05). Postmatch brief and sustained KE VA was lower in hot than in cool (p<0.05), in which VA was maintained. PF VA was maintained throughout the protocol. Peak twitch torque and maximum rates of torque development and relaxation in the KE and PF were equally reduced postmatch relative to prematch in hot and cool conditions (p<0.05), and were restored near baseline within 24 h. Conclusions Neuromuscular system integrity of the lower limbs is compromised immediately following match-play tennis in hot and cool conditions due to the development of peripheral fatigue. The larger and persistent KE strength losses observed under heat stress are associated with greater levels of central fatigue especially during sustained contractions. PMID:24668379

  18. Isometric knee extensor fatigue following a Wingate test: peripheral and central mechanisms.

    PubMed

    Fernandez-del-Olmo, M; Rodriguez, F A; Marquez, G; Iglesias, X; Marina, M; Benitez, A; Vallejo, L; Acero, R M

    2013-02-01

    Central and peripheral fatigue have been explored during and after running or cycling exercises. However, the fatigue mechanisms associated with a short maximal cycling exercise (30 s Wingate test) have not been investigated. In this study, 10 volunteer subjects performed several isometric voluntary contractions using the leg muscle extensors before and after two bouts of cycling at 25% of maximal power output and two bouts of Wingate tests. Transcranial magnetic stimulation (TMS) and electrical motor nerve stimulation (NM) were applied at rest and during the voluntary contractions. Maximal voluntary contraction (MVC), voluntary activation (VA), twitch amplitude evoked by electrical nerve stimulation, M wave and motor potential evoked by TMS (MEP) were recorded. MVC, VA and twitch amplitude evoked at rest by NM decreased significantly after the first and second Wingate tests, indicating central and peripheral fatigue. MVC and VA, but not the twitch amplitude evoked by NM, recovered before the second Wingate test. These results suggest that the Wingate test results in a decrease in MVC associated with peripheral and central fatigue. While the peripheral fatigue is associated with an intramuscular impairment, the central fatigue seems to be the main reason for the Wingate test-induced impairment of MVC. PMID:21812824

  19. Reproducibility of cardiac biomarkers response to prolonged treadmill exercise.

    PubMed

    Tian, Ye; Nie, Jinlei; George, Keith P; Huang, Chuanye

    2014-03-01

    We examined the reproducibility of alterations in cardiac biomarkers after two identical bouts of prolonged exercise in young athletes. Serum high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were assessed before and after exercise. Significant rises in median hs-cTnT and NT-proBNP occurred in both trials. While the absolute changes in hs-cTnT were smaller after trial 2, the pattern of change was similar and the delta scores were significantly related. However, the change in NT-proBNP was not correlated between trials. The hs-cTnT release demonstrates some consistency after exercise although the blunted hc-cTnT response requires further study. PMID:24451016

  20. Electromechanical delay of the knee extensor muscles is not altered after harvesting the patellar tendon as a graft for ACL reconstruction: implications for sports performance.

    PubMed

    Georgoulis, A D; Ristanis, S; Papadonikolakis, A; Tsepis, E; Moebius, U; Moraiti, C; Stergiou, N

    2005-09-01

    Although the scar tissue, which heals the donor site defect, has different elasticity from the neighbouring patellar tissue, it remains unclear if this scar tissue can lead to the changes of the electromechanical delay (EMD) of the knee extensor muscles. If such changes do exist, they can possibly affect both the utilization of the stored energy in the series elastic component, as well as the optimal performance of the knee joint movement. The purpose of this study was to investigate the influence of harvesting the patellar tendon during anterior cruciate ligament (ACL) reconstruction and the associated patellar tendon scar tissue development on the EMD of the rectus femoris (RF) and vastus medialis (VM) muscles. Seventeen patients who underwent an ACL reconstruction using the medial third of the patellar tendon were divided in two groups based upon their post-operative time interval. Maximal voluntary contraction from the knee extensors, surface EMG activity, and ultrasonographic measurements of the patellar tendon cross-section area were obtained from both knees. Our results revealed that no significant changes for the maximal voluntary contraction of the knee extensors and for the EMD of the RF and the VM muscles due to patellar scar tissue development after harvesting the tendon for ACL reconstruction. The EMD, as a component of the stretch reflex, is important for the utilization of the stored energy in the series elastic component and thus, optimal sports performance. However, from our results, it can be implied that the ACL reconstruction using a patellar tendon graft would not impair sports performance as far as EMD is concerned. PMID:15968530

  1. Alteration of Muscle Function After Electrical Stimulation Bout of Knee Extensors and Flexors

    PubMed Central

    Vanderthommen, Marc; Triffaux, Mylène; Demoulin, Christophe; Crielaard, Jean-Michel; Croisier, Jean-Louis

    2012-01-01

    The purpose was to study the effects on muscle function of an electrical stimulation bout applied unilaterally on thigh muscles in healthy male volunteers. One group (ES group, n = 10) received consecutively 100 isometric contractions of quadriceps and 100 isometric contractions of hamstrings (on-off ratio 6-6 s) induced by neuromuscular electrical stimulations (NMES). Changes in muscle torque, muscle soreness (0-10 VAS), muscle stiffness and serum creatine kinase (CK) activity were assessed before the NMES exercise (pre-ex) as well as 24h (d+1), 48h (d+2) and 120h (d+5) after the bout. A second group (control group, n = 10) were submitted to the same test battery than the ES group and with the same time-frame. The between-group comparison indicated a significant increase in VAS scores and in serum levels of CK only in the ES group. In the ES group, changes were more pronounced in hamstrings than in quadriceps and peaked at d+2 (quadriceps VAS scores = 2.20 ± 1.55 a.u. (0 at pre-ex); hamstrings VAS scores = 3.15 ± 2.14 a.u. (0 at pre-ex); hip flexion angle = 62 ± 5° (75 ± 6° at pre-ex); CK activity = 3021 ± 2693 IU·l-1 (136 ± 50 IU·l-1 at pre-ex)). The results of the present study suggested the occurrence of muscle damage that could have been induced by the peculiar muscle recruitment in NMES and the resulting overrated mechanical stress. The sensitivity to the damaging effects of NMES appeared higher in the hamstrings than in quadriceps muscles. Key points A stimulation bout of quadriceps and hamstrings that reflects usual application of NMES, increases indirect markers of muscle damage (muscle soreness, muscle weakness and stiffness and serum CK activity). The occurrence of muscle damage could have been induced by the peculiar muscle recruitment in NMES and the resulting overrated mechanical stress. The sensitivity to the damaging effects of NMES appears higher in the hamstrings than in quadriceps muscles. PMID:24150067

  2. Performance predicting factors in prolonged exhausting exercise of varying intensity.

    PubMed

    Björklund, Glenn; Pettersson, Sofia; Schagatay, Erika

    2007-03-01

    Several endurance sports, e.g. road cycling, have a varying intensity profile during competition. At present, few laboratory tests take this intensity profile into consideration. Thus, the purpose of this study was to examine the prognostic value of heart rate (HR), lactate (La(-1)), potassium (K(+)), and respiratory exchange ratio (RER) performance at an exhausting cycling exercise with varying intensity. Eight national level cyclists performed two cycle tests each on a cycle ergometer: (1) a incremental test to establish VO(2max), maximum power (W (max)), and lactate threshold (VO(2LT)), and (2) a variable intensity protocol (VIP). Exercise intensity for the VIP was based upon the VO(2max) obtained during the incremental test. The VIP consisted of six high intense (HI) workloads at 90% of VO(2max) for 3 min each, interspersed by five middle intense (MI) workloads at 70% of VO(2max )for 6 min each. VO(2 )and HR were continuously measured throughout the tests. Venous blood samples were taken before, during, and after the test. Increases in HR, La(-), K(+), and RER were observed when workload changed from MI to HI workload (P < 0.05). Potassium and RER decreased after transition from HI to MI workloads (P < 0.05). There was a negative correlation between time to exhaustion and decrease in La(-) concentration during the first MI (r = -0.714; P = 0.047). Furthermore, time to exhaustion correlated with VO(2LT )calculated from the ramp test (r = 0.738; P = 0.037). Our results suggest that the magnitude of decrease of La(-1) between the first HI workload and the consecutive MI workload could predict performance during prolonged exercise with variable intensity. PMID:17186302

  3. Artificial gravity as a countermeasure to microgravity: a pilot study examining the effects on knee extensor and plantar flexor muscle groups.

    PubMed

    Caiozzo, V J; Haddad, F; Lee, S; Baker, M; Paloski, William; Baldwin, K M

    2009-07-01

    The goal of this project was to examine the effects of artificial gravity (AG) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) group (n = 7) and 2) an AG group (n = 8), which was subjected to 21 days of 6 degrees head-down tilt bed rest plus daily 1-h exposures to AG (2.5 G at the feet). Centrifugation was produced using a short-arm centrifuge with the foot plate approximately 220 cm from the center of rotation. The torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre- and posttreatment. Muscle biopsy samples obtained from the vastus lateralis and soleus muscles were used for a series of gene expression analyses (mRNA abundance) of key factors implicated in the anabolic vs. catabolic state of the muscle. Post/pre torque-velocity determinations revealed greater decrements in knee extensor performance in the BR vs. AG group (P < 0.04). The plantar flexors of the AG subjects actually demonstrated a net gain in the torque-velocity relationship, whereas in the BR group, the responses declined (AG vs. BR, P < 0.001). Muscle fiber cross-sectional area decreased by approximately 20% in the BR group, whereas no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity were higher in the AG group, whereas catabolic markers were elevated in the BR group. Importantly, these patterns were seen in both muscles. We conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading. PMID:19286573

  4. Influence of obstructive sleep apnea syndrome in the fluctuation of the submaximal isometric torque of knee extensors in patients with early-grade osteoarthritis

    PubMed Central

    Silva, Andressa; Mello, Marco T.; Serrão, Paula R.; Luz, Roberta P.; Bittencourt, Lia R.; Mattiello, Stela M.

    2015-01-01

    OBJECTIVE: The aim of this study was to investigate whether obstructive sleep apnea (OSA) alters the fluctuation of submaximal isometric torque of the knee extensors in patients with early-grade osteoarthritis (OA). METHOD: The study included 60 male volunteers, aged 40 to 70 years, divided into four groups: Group 1 (G1) - Control (n=15): without OA and without OSA; Group 2 (G2) (n=15): with OA and without OSA; Group 3 (G3) (n=15): without OA and with OSA; and Group 4 (G4) (n=15) with OA and with OSA. Five patients underwent maximal isometric contractions of 10 seconds duration each, with the knee at 60° of flexion to determine peak torque at 60°. To evaluate the fluctuation of torque, 5 submaximal isometric contractions (50% of maximum peak torque) of 10 seconds each, which were calculated from the standard deviation of torque and coefficient of variation, were performed. RESULTS: Significant differences were observed between groups for maximum peak torque, while G4 showed a lower value compared with G1 (p=0.005). Additionally, for the average torque exerted, G4 showed a lower value compared to the G1 (p=0.036). However, no differences were found between the groups for the standard deviation (p=0.844) and the coefficient of variation (p=0.143). CONCLUSION: The authors concluded that OSA did not change the parameters of the fluctuation of isometric submaximal torque of knee extensors in patients with early-grade OA. PMID:26443974

  5. Artificial gravity as a countermeasure to microgravity: a pilot study examining the effects on knee extensor and plantar flexor muscle groups

    PubMed Central

    Caiozzo, V. J.; Haddad, F.; Lee, S.; Baker, M.; Paloski, William; Baldwin, K. M.

    2009-01-01

    The goal of this project was to examine the effects of artificial gravity (AG) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) group (n = 7) and 2) an AG group (n = 8), which was subjected to 21 days of 6° head-down tilt bed rest plus daily 1-h exposures to AG (2.5 G at the feet). Centrifugation was produced using a short-arm centrifuge with the foot plate ∼220 cm from the center of rotation. The torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre- and posttreatment. Muscle biopsy samples obtained from the vastus lateralis and soleus muscles were used for a series of gene expression analyses (mRNA abundance) of key factors implicated in the anabolic vs. catabolic state of the muscle. Post/pre torque-velocity determinations revealed greater decrements in knee extensor performance in the BR vs. AG group (P < 0.04). The plantar flexors of the AG subjects actually demonstrated a net gain in the torque-velocity relationship, whereas in the BR group, the responses declined (AG vs. BR, P < 0.001). Muscle fiber cross-sectional area decreased by ∼20% in the BR group, whereas no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity were higher in the AG group, whereas catabolic markers were elevated in the BR group. Importantly, these patterns were seen in both muscles. We conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading. PMID:19286573

  6. Salivary and serum cortisol levels during recovery from intense exercise and prolonged, moderate exercise.

    PubMed

    Powell, J; DiLeo, T; Roberge, R; Coca, A; Kim, J-H

    2015-06-01

    The aim of this study was to compare serum (SERc) and salivary cortisol (SALc) responses during recovery from two different exhaustive exercises to determine peak cortisol sampling time and the agreement between SERc and SALc levels. Twelve healthy men underwent a maximal treadmill graded exercise to exhaustion (MEx) and a prolonged, submaximal cycle exercise in the heat for 90 min (PEx) while SERc and SALc samples were taken in parallel at baseline, end of exercise, and 15 min intervals over one hour of recovery. MEx and PEx significantly increased SERc and SALc levels (p < 0.01) while absolute SERc levels were approximately 7-10 folds higher than SALc. SERc and SALc showed highly positive correlation (R = 0.667-0.910, p < 0.05) at most sampling times and only a few individual values were out of 95% limit of agreement when analyzed by Bland-Altman plots. However, peak SERc levels (MEx: 784.0±147, PEx: 705.5±212.0 nmol · L(-1)) occurred at 15 min of recovery, whereas peak SALc levels (MEx: 102.7±46.4, PEx: 95.7±40.9 nmol · L(-1)) were achieved at the end of exercise in MEx and PEx. The recovery trend of SERc and SALc also differed following MEx and PEx. Activity of 11β-hydroxysteroid dehydrogenase type 2 enzymes may be suppressed following MEx compared to PEx. In conclusion, sampling for peak SERc and SALc levels should take into account their evolution and clearance characteristics as well as type of exercise performed, whereas SALc appeared to be a more sensitive marker than SERc for the measurement of cortisol responses during exercise recovery. PMID:26028807

  7. Salivary and serum cortisol levels during recovery from intense exercise and prolonged, moderate exercise

    PubMed Central

    Powell, J; DiLeo, T; Roberge, R; Coca, A

    2015-01-01

    The aim of this study was to compare serum (SERc) and salivary cortisol (SALc) responses during recovery from two different exhaustive exercises to determine peak cortisol sampling time and the agreement between SERc and SALc levels. Twelve healthy men underwent a maximal treadmill graded exercise to exhaustion (MEx) and a prolonged, submaximal cycle exercise in the heat for 90 min (PEx) while SERc and SALc samples were taken in parallel at baseline, end of exercise, and 15 min intervals over one hour of recovery. MEx and PEx significantly increased SERc and SALc levels (p < 0.01) while absolute SERc levels were approximately 7-10 folds higher than SALc. SERc and SALc showed highly positive correlation (R = 0.667-0.910, p < 0.05) at most sampling times and only a few individual values were out of 95% limit of agreement when analyzed by Bland-Altman plots. However, peak SERc levels (MEx: 784.0±147, PEx: 705.5±212.0 nmol · L−1) occurred at 15 min of recovery, whereas peak SALc levels (MEx: 102.7±46.4, PEx: 95.7±40.9 nmol · L−1) were achieved at the end of exercise in MEx and PEx. The recovery trend of SERc and SALc also differed following MEx and PEx. Activity of 11β-hydroxysteroid dehydrogenase type 2 enzymes may be suppressed following MEx compared to PEx. In conclusion, sampling for peak SERc and SALc levels should take into account their evolution and clearance characteristics as well as type of exercise performed, whereas SALc appeared to be a more sensitive marker than SERc for the measurement of cortisol responses during exercise recovery. PMID:26028807

  8. Influence of exercise duration and hydration status on cognitive function during prolonged cycling exercise.

    PubMed

    Grego, F; Vallier, J-M; Collardeau, M; Rousseu, C; Cremieux, J; Brisswalter, J

    2005-01-01

    The purpose of the present study was to examine the influence of submaximal aerobic exercise duration on simple and complex cognitive performance. Eight well-trained male subjects agreed to participate in this study (trial group). A control group of eight regularly trained male subjects was included for comparative purposes. For the trial group, the experiment involved a critical flicker fusion test (CFF) and a map recognition task performed before, every 20 min during, and immediately after, a 3-h cycling task at an intensity corresponding to approximately 60 % of VO2max. Data were obtained over two experimental sessions with fluid ingestion (F) or no fluid (NF) ingestion. For the control group the experiment was the same but without exercise and fluid ingestion. In the trial group, a significant effect of hydration status was observed on physiological parameters (p <0.05). No effect was found on cognitive performance. A significant decrease in CFF performance was observed after 120 min of exercise when compared with the first 20 min (respectively for CFFmdi: 2.6 vs. 3.8 Hz), irrespective of experimental condition. A significant improvement in speed of response (respectively: 3291 vs. 3062 msec for 20 and 120 min, respectively) and a decrease in error number (21.5 % vs. 6.0 % for 20 and 120 min, respectively) during the map recognition task were recorded between 80 min and 120 min when compared with the first 20 min of exercise. After 120 min the number of recorded errors was significantly greater indicating a shift in the accuracy-speed trade-off (6.0 % vs. 14.1 % for 120 and 180 min, respectively). These results provide some evidence for exercise-induced facilitation of cognitive function. However this positive effect disappears during prolonged exercise--as evidenced within our study by an increase in errors during the complex task and an alteration in perceptual response (i.e. the appearance of symptoms of central fatigue). PMID:15643531

  9. Influence of preliminary exercise training on muscle damage indices in rats after one bout of prolonged treadmill exercise.

    PubMed

    Hyun, Ju; Kim, Young Mi; Hwangbo, Kak; Kim, Young Mi

    2016-06-01

    [Purpose] The purpose of this study was to investigate the effects of exercise on muscle damage indices in male Sprague-Dawley rats. Two groups of rats were trained in either moderate- or high-intensity treadmill running for 4 weeks. Subsequently, the concentrations of creatine kinase, lactate dehydrogenase, and high-sensitivity C-reactive protein were examined following a single bout of prolonged (3-h) intensive exercise. [Subjects and Methods] The study included forty 6-week-old male Sprague-Dawley rats weighing 150-180 g each. The aerobic exercise group was divided into high-intensity (28 m/min) and moderate-intensity (15 m/min) subgroups. Both subgroups were trained for 35 min daily for 6 days per week (excluding Sunday) over a 4-week period. Following training, the high- and moderate-intensity exercise groups and a non-exercise group performed one bout of prolonged (3-h) treadmill exercise for 3 hours at a speed of 15 m/min. [Results] Creatine kinase and lactate dehydrogenase levels differed significantly among the groups. [Conclusion] The preliminary exercise groups showed lower muscle damage and inflammatory response levels than the non-exercise group after the bout of prolonged intensive exercise. PMID:27390433

  10. Influence of preliminary exercise training on muscle damage indices in rats after one bout of prolonged treadmill exercise

    PubMed Central

    Hyun, Ju; Kim, Young Mi; Hwangbo, Kak; Kim, Young Mi

    2016-01-01

    [Purpose] The purpose of this study was to investigate the effects of exercise on muscle damage indices in male Sprague-Dawley rats. Two groups of rats were trained in either moderate- or high-intensity treadmill running for 4 weeks. Subsequently, the concentrations of creatine kinase, lactate dehydrogenase, and high-sensitivity C-reactive protein were examined following a single bout of prolonged (3-h) intensive exercise. [Subjects and Methods] The study included forty 6-week-old male Sprague-Dawley rats weighing 150–180 g each. The aerobic exercise group was divided into high-intensity (28 m/min) and moderate-intensity (15 m/min) subgroups. Both subgroups were trained for 35 min daily for 6 days per week (excluding Sunday) over a 4-week period. Following training, the high- and moderate-intensity exercise groups and a non-exercise group performed one bout of prolonged (3-h) treadmill exercise for 3 hours at a speed of 15 m/min. [Results] Creatine kinase and lactate dehydrogenase levels differed significantly among the groups. [Conclusion] The preliminary exercise groups showed lower muscle damage and inflammatory response levels than the non-exercise group after the bout of prolonged intensive exercise. PMID:27390433

  11. Acute moderate exercise does not attenuate cardiometabolic function associated with a bout of prolonged sitting.

    PubMed

    Younger, Amanda M; Pettitt, Robert W; Sexton, Patrick J; Maass, William J; Pettitt, Cherie D

    2016-01-01

    Epidemiological studies suggest that prolonged sitting increases all-cause mortality; yet, physiological causes underpinning prolonged sitting remain elusive. We evaluated cardiometabolic function during prolonged sitting (5 h) in 10 adults with and without 30 min of moderate exercise leading up to the sitting. Mean arterial blood pressure (MAP), heart rate (HR) and posterior tibial artery blood velocity were measured at baseline and every hour subsequently. Blood glucose was measured at baseline, 3 and 5 h, with consumption of a caloric beverage at 1 h. Seated MAP and HR values were ~17 mmHg (P < 0.001) and ~4 bpm (P < 0.05) higher for the moderate exercise versus sitting conditions. A ~ 4 cm·s(-1) (16%) (P < 0.05) decline in posterior tibial artery blood velocity from prolonged sitting was observed, with no benefit conferred from moderate exercise. Postprandial glucose metabolism was not different between conditions (P > 0.05). We conclude prolonged sitting may be related to decreased posterior tibial artery blood velocity. Moreover, an acute bout of moderate exercise does not seem to attenuate cardiometabolic function during prolonged sitting in healthy, young adults. PMID:26186044

  12. Knee extensor loss and proximal tibial soft tissue defect managed successfully with simultaneous medial gastrocnemius flap, saphenous fasciocutaneous flap and medial hemisoleus flap: a case report

    PubMed Central

    2013-01-01

    Introduction Open fractures of the proximal tibia often pose serious challenges to the treating orthopedic surgeon. Management of these complex injuries becomes difficult if they are associated with damage to the extensor mechanism and an exposed knee joint. The scenario becomes more difficult to manage when the soft tissue defect extends to the middle third of the leg. We report a case where we used an extended medial gastrocnemius flap in combination with a saphenous artery fasciocutaneous flap and a medial hemisoleus flap for treatment of an infected proximal tibia fracture with loss of the extensor mechanism and soft tissue defect. To the best of our knowledge, combined use of these three flaps for the management of such injuries has not been reported elsewhere to date. Case presentation A 28-year-old Indian man presented to our Out-patient Department with complaints of pain and pus discharge from his left proximal leg for four weeks. He had sustained an open fracture of his left proximal tibia in a road traffic accident five weeks ago and had been operated on elsewhere. He had a stiff, painful knee with an infected wound of 4×4cm over the proximal third of his leg exposing infected, necrotic patellar tendon. He was successfully managed with debridement and simultaneously elevated flaps as described. Conclusions This procedure avoids the donor site morbidity associated with free flaps harvested from sites distant from the site of injury, and also does not need the expertise of microvascular reconstruction. To the best of our knowledge, this is also the first report of the combined use of three local flaps for knee extensor reconstruction and soft tissue coverage around the knee. PMID:23506268

  13. Carbohydrate vs protein supplementation for recovery of neuromuscular function following prolonged load carriage

    PubMed Central

    2010-01-01

    Background This study examined the effect of carbohydrate and whey protein supplements on recovery of neuromuscular function after prolonged load carriage. Methods Ten male participants (body mass: 81.5 ± 10.5 kg, age: 28 ± 9 years, O2max: 55.0 ± 5.5 ml·kg-1·min-1) completed three treadmill walking tests (2 hr, 6.5 km·h-1), carrying a 25 kg backpack consuming 500 ml of either: (1) Placebo (flavoured water) [PLA], (2) 6.4% Carbohydrate Solution [CHO] or (3) 7.0% Whey Protein Solution [PRO]. For three days after load carriage, participants consumed two 500 ml supplement boluses. Muscle performance was measured before and at 0, 24, 48 and 72 h after load carriage, during voluntary and electrically stimulated contractions. Results Isometric knee extension force decreased immediately after load carriage with no difference between conditions. During recovery, isometric force returned to pre-exercise values at 48 h for CHO and PRO but at 72 h for PLA. Voluntary activation decreased immediately after load carriage and returned to pre-exercise values at 24 h in all conditions (P = 0.086). During recovery, there were no differences between conditions for the change in isokinetic peak torque. Following reductions immediately after load carriage, knee extensor and flexor peak torque (60°·s-1) recovered to pre-exercise values at 72 h. Trunk extensor and flexor peak torque (15°·s-1) recovered to pre-exercise values at 24 h (P = 0.091) and 48 h (P = 0.177), respectively. Conclusion Recovery of neuromuscular function after prolonged load carriage is improved with either carbohydrate or whey protein supplementation for isometric contractions but not for isokinetic contractions. PMID:20157419

  14. Forearm training attenuates sympathetic responses to prolonged rhythmic forearm exercise

    NASA Technical Reports Server (NTRS)

    Sinoway, L.; Shenberger, J.; Leaman, G.; Zelis, R.; Gray, K.; Baily, R.; Leuenberger, U.

    1996-01-01

    We previously demonstrated that nonfatiguing rhythmic forearm exercise at 25% maximal voluntary contraction (12 2-s contractions/min) evokes sympathoexcitation without significant engagement of metabolite-sensitive muscle afferents (B.A. Batman, J.C. Hardy, U.A. Leuenberger, M.B. Smith, Q.X. Yang and L.I. Sinoway. J. Appl. Physiol. 76: 1077-1081, 1994). This is in contrast to the sympathetic nervous system responses observed during fatiguing static forearm exercise where metabolite-sensitive afferents are the key determinants of sympathetic activation. In this report we examined whether forearm exercise training would attenuate sympathetic nervous system responses to rhythmic forearm exercise. We measured heart rate, mean arterial blood pressure (MAP), muscle sympathetic nerve activity (microneurography), plasma norepinephrine (NE), and NE spillover and clearance (tritiated NE kinetics) during nonfatiguing rhythmic forearm exercise before and after a 4-wk unilateral forearm training paradigm. Training had no effect on forearm mass, maximal voluntary contraction, or heart rate but did attenuate the increase in MAP (increase in MAP: from 15.2 +/- 1.8 before training to 11.4 +/- 1.4 mmHg after training; P < 0.017), muscle sympathetic nerve activity (increase in bursts: from 10.8 +/- 1.4 before training to 6.2 +/- 1.1 bursts/min after training; P < 0.030), and the NE spillover (increases in arterial spillover: from 1.3 +/- 0.2 before training to 0.6 +/- 0.2 nmol.min-1.m-2 after training, P < 0.014; increase in venous spillover: from 2.0 +/- 0.6 before training to 1.0 +/- 0.5 nmol.min-1.m-2 after training, P < 0.037) seen in response to exercise performed by the trained forearm. Thus forearm training reduces sympathetic responses during a nonfatiguing rhythmic handgrip paradigm that does not engage muscle metaboreceptors. We speculate that this effect is due to a conditioning-induced reduction in mechanically sensitive muscle afferent discharge.

  15. Space physiology VI: exercise, artificial gravity, and countermeasure development for prolonged space flight.

    PubMed

    Hargens, Alan R; Bhattacharya, Roshmi; Schneider, Suzanne M

    2013-09-01

    When applied individually, exercise countermeasures employed to date do not fully protect the cardiovascular and musculoskeletal systems during prolonged spaceflight. Recent ground-based research suggests that it is necessary to perform exercise countermeasures within some form of artificial gravity to prevent microgravity deconditioning. In this regard, it is important to provide normal foot-ward loading and intravascular hydrostatic-pressure gradients to maintain musculoskeletal and cardiovascular function. Aerobic exercise within a centrifuge restores cardiovascular function, while aerobic exercise within lower body negative pressure restores cardiovascular function and helps protect the musculoskeletal system. Resistive exercise with vibration stimulation may increase the effectiveness of resistive exercise by preserving muscle function, allowing lower intensity exercises, and possibly reducing risk of loss of vision during prolonged spaceflight. Inexpensive methods to induce artificial gravity alone (to counteract head-ward fluid shifts) and exercise during artificial gravity (for example, by short-arm centrifuge or exercise within lower body negative pressure) should be developed further and evaluated as multi-system countermeasures. PMID:23079865

  16. High altitude, prolonged exercise, and the athlete biological passport.

    PubMed

    Schumacher, Yorck O; Garvican, Laura A; Christian, Ryan; Lobigs, Louisa M; Qi, Jiliang; Fan, Rongyun; He, Yingying; Wang, Hailing; Gore, Christopher J; Ma, Fuhai

    2015-01-01

    The Athlete Biological Passport (ABP) detects blood doping in athletes through longitudinal monitoring of erythropoietic markers. Mathematical algorithms are used to define individual reference ranges for these markers for each athlete. It is unclear if altitude and exercise can affect the variables included in these calculations in a way that the changes might be mistaken for blood manipulation. The aim of this study was to investigate the influence of the simultaneous strenuous exercise and low to high altitude exposure on the calculation algorithms of the ABP. 14 sea level (SL) and 11 altitude native (ALT) highly trained athletes participated in a 14-day cycling stage race taking place at an average altitude of 2496 m above sea level (min. 1014 m, max. 4120 m), race distances ranged between 96 and 227 km per day. ABP blood measures were taken on days -1,3,6,10,14 (SL) and -1,9,15 (ALT) of the race. Four results from three samples of two different SL athletes exceeded the individual limits at the 99% specificity threshold and one value at 99.9%. In ALT, three results from three samples of three different athletes were beyond the individual limits at 99%, one at 99.9%. The variations could be explained by the expected physiological reaction to exercise and altitude. In summary, the abnormalities observed in the haematological ABP´s of well-trained athletes during extensive exercise at altitude are limited and in line with expected physiological changes. PMID:25252093

  17. Plasma cell-free mitochondrial DNA declines in response to prolonged moderate aerobic exercise.

    PubMed

    Shockett, Penny E; Khanal, Januka; Sitaula, Alina; Oglesby, Christopher; Meachum, William A; Castracane, V Daniel; Kraemer, Robert R

    2016-01-01

    Increased plasma cell-free mitochondrial DNA (cf-mDNA), a damage-associated molecular pattern (DAMP) produced by cellular injury, contributes to neutrophil activation/inflammation in trauma patients and arises in cancer and autoimmunity. To further understand relationships between cf-mDNA released by tissue injury, inflammation, and health benefits of exercise, we examined cf-mDNA response to prolonged moderate aerobic exercise. Seven healthy moderately trained young men (age = 22.4 ± 1.2) completed a treadmill exercise trial for 90 min at 60% VO2 max and a resting control trial. Blood was sampled immediately prior to exercise (0 min = baseline), during (+18, +54 min), immediately after (+90 min), and after recovery (R40). Plasma was analyzed for cf-mDNA, IL-6, and lactate. A significant difference in cf-mDNA response was observed between exercise and control trials, with cf-mDNA levels reduced during exercise at +54 and +90 (with or without plasma volume shift correction). Declines in cf-mDNA were accompanied by increased lactate and followed by an increase in IL-6, suggesting a temporal association with muscle stress and inflammatory processes. Our novel finding of cf-mDNA decline with prolonged moderate treadmill exercise provides evidence for increased clearance from or reduced release of cf-mDNA into the blood with prolonged exercise. These studies contrast with previous investigations involving exhaustive short-term treadmill exercise, in which no change in cf-mDNA levels were reported, and contribute to our understanding of differences between exercise- and trauma-induced inflammation. We propose that transient declines in cf-mDNA may induce health benefits, by reducing systemic inflammation. PMID:26755735

  18. Effect of Prolonged Moderate Exercise on the Changes of Nonneuronal Cells in Early Myocardial Infarction.

    PubMed

    Rinaldi, Barbara; Guida, Francesca; Furiano, Anna; Donniacuo, Maria; Luongo, Livio; Gritti, Giulia; Urbanek, Konrad; Messina, Giovanni; Maione, Sabatino; Rossi, Francesco; de Novellis, Vito

    2015-01-01

    Myocardial infarction (MI) is one of the leading causes of death in developed countries and it is characterized by several associated symptomatologies and poor quality of life. Recent data showed a possible interaction between infarction and brain inflammation and activity. Previous studies have demonstrated the beneficial effect of exercise training on deterioration in cardiac function after MI. In this study we analyzed in sedentary and trained rats the microglia and astrocytes 48 hours after MI in PVN, thalamus, prefrontal cortex, and hippocampus through immunofluorescence approach. We found significant changes in specific microglia phenotypes in the brain areas analyzed together with astrocytes activation. Prolonged exercise normalized these morphological changes of microglia and astrocytes in the prefrontal cortex, hippocampus, and thalamus but not in the PVN. Our data suggest that there is an early brain reaction to myocardial infarction induction, involving nonneuronal cells, that is attenuated by the prolonged exercise. PMID:26266053

  19. Effect of Prolonged Moderate Exercise on the Changes of Nonneuronal Cells in Early Myocardial Infarction

    PubMed Central

    Rinaldi, Barbara; Guida, Francesca; Furiano, Anna; Donniacuo, Maria; Luongo, Livio; Gritti, Giulia; Urbanek, Konrad; Messina, Giovanni; Maione, Sabatino; Rossi, Francesco; de Novellis, Vito

    2015-01-01

    Myocardial infarction (MI) is one of the leading causes of death in developed countries and it is characterized by several associated symptomatologies and poor quality of life. Recent data showed a possible interaction between infarction and brain inflammation and activity. Previous studies have demonstrated the beneficial effect of exercise training on deterioration in cardiac function after MI. In this study we analyzed in sedentary and trained rats the microglia and astrocytes 48 hours after MI in PVN, thalamus, prefrontal cortex, and hippocampus through immunofluorescence approach. We found significant changes in specific microglia phenotypes in the brain areas analyzed together with astrocytes activation. Prolonged exercise normalized these morphological changes of microglia and astrocytes in the prefrontal cortex, hippocampus, and thalamus but not in the PVN. Our data suggest that there is an early brain reaction to myocardial infarction induction, involving nonneuronal cells, that is attenuated by the prolonged exercise. PMID:26266053

  20. Lack of Skeletal Muscle IL-6 Affects Pyruvate Dehydrogenase Activity at Rest and during Prolonged Exercise

    PubMed Central

    Gudiksen, Anders; Schwartz, Camilla Lindgren; Bertholdt, Lærke; Joensen, Ella; Knudsen, Jakob G.; Pilegaard, Henriette

    2016-01-01

    Pyruvate dehydrogenase (PDH) plays a key role in the regulation of skeletal muscle substrate utilization. IL-6 is produced in skeletal muscle during exercise in a duration dependent manner and has been reported to increase whole body fatty acid oxidation, muscle glucose uptake and decrease PDHa activity in skeletal muscle of fed mice. The aim of the present study was to examine whether muscle IL-6 contributes to exercise-induced PDH regulation in skeletal muscle. Skeletal muscle-specific IL-6 knockout (IL-6 MKO) mice and floxed littermate controls (control) completed a single bout of treadmill exercise for 10, 60 or 120 min, with rested mice of each genotype serving as basal controls. The respiratory exchange ratio (RER) was overall higher (P<0.05) in IL-6 MKO than control mice during the 120 min of treadmill exercise, while RER decreased during exercise independent of genotype. AMPK and ACC phosphorylation also increased with exercise independent of genotype. PDHa activity was in control mice higher (P<0.05) at 10 and 60 min of exercise than at rest but remained unchanged in IL-6 MKO mice. In addition, PDHa activity was higher (P<0.05) in IL-6 MKO than control mice at rest and 60 min of exercise. Neither PDH phosphorylation nor acetylation could explain the genotype differences in PDHa activity. Together, this provides evidence that skeletal muscle IL-6 contributes to the regulation of PDH at rest and during prolonged exercise and suggests that muscle IL-6 normally dampens carbohydrate utilization during prolonged exercise via effects on PDH. PMID:27327080

  1. Liver glycogen metabolism during and after prolonged endurance-type exercise.

    PubMed

    Gonzalez, Javier T; Fuchs, Cas J; Betts, James A; van Loon, Luc J C

    2016-09-01

    Carbohydrate and fat are the main substrates utilized during prolonged endurance-type exercise. The relative contribution of each is determined primarily by the intensity and duration of exercise, along with individual training and nutritional status. During moderate- to high-intensity exercise, carbohydrate represents the main substrate source. Because endogenous carbohydrate stores (primarily in liver and muscle) are relatively small, endurance-type exercise performance/capacity is often limited by endogenous carbohydrate availability. Much exercise metabolism research to date has focused on muscle glycogen utilization, with little attention paid to the contribution of liver glycogen. (13)C magnetic resonance spectroscopy permits direct, noninvasive measurements of liver glycogen content and has increased understanding of the relevance of liver glycogen during exercise. In contrast to muscle, endurance-trained athletes do not exhibit elevated basal liver glycogen concentrations. However, there is evidence that liver glycogenolysis may be lower in endurance-trained athletes compared with untrained controls during moderate- to high-intensity exercise. Therefore, liver glycogen sparing in an endurance-trained state may account partly for training-induced performance/capacity adaptations during prolonged (>90 min) exercise. Ingestion of carbohydrate at a relatively high rate (>1.5 g/min) can prevent liver glycogen depletion during moderate-intensity exercise independent of the type of carbohydrate (e.g., glucose vs. sucrose) ingested. To minimize gastrointestinal discomfort, it is recommended to ingest specific combinations or types of carbohydrates (glucose plus fructose and/or sucrose). By coingesting glucose with either galactose or fructose, postexercise liver glycogen repletion rates can be doubled. There are currently no guidelines for carbohydrate ingestion to maximize liver glycogen repletion. PMID:27436612

  2. Role of nitric oxide in exercise hyperaemia during prolonged rhythmic handgripping in humans.

    PubMed Central

    Dyke, C K; Proctor, D N; Dietz, N M; Joyner, M J

    1995-01-01

    1. We sought to determine whether the vasodilating molecule nitric oxide (NO) contributes to the forearm hyperaemia observed during prolonged rhythmic handgripping in humans. 2. Two bouts of exercise were performed during experimental protocols conducted on separate days. During each protocol the subject performed a 10 min and a 20 min bout of rhythmic (30 min-1) handgripping at 15% of maximum. Two exercise bouts were required to facilitate pharmacological interventions during the second protocol. Blood flow in the exercising forearm was measured every minute with plethysmography during brief pauses in the contractions. During both exercise bouts in the first protocol, forearm blood flow increased 2- to 3-fold above rest after 1 min of handgripping and remained constant at that level throughout the exercise. 3. During the 10 min bout of exercise in the second protocol, acetylcholine was given via a brachial artery catheter at 16 micrograms min-1 for 3 min to evoke NO release from the vascular endothelium. This caused forearm blood flow to increase above the values observed during exercise alone. 4. During the 20 min trial of handgripping in the second protocol, the NO synthase blocker NG-monomethyl-L-arginine (L-NMMA) was infused in the exercising forearm via the brachial catheter after 5 min of handgripping. The L-NMMA was infused at 4 mg min-1 for 10 min. 5. L-NMMA during exercise caused forearm blood flow to fall to values approximately 20-30% lower than those observed during exercise alone. When ACh was given during exercise after L-NMMA administration the rise in blood flow was also blunted, indicating blockade of NO synthase. These data suggest NO plays a role in exercise hyperaemia in humans. Images Figure 1 PMID:8568663

  3. Hypertrophy of chronically unloaded muscle subjected to resistance exercise.

    PubMed

    Tesch, P A; Trieschmann, J T; Ekberg, A

    2004-04-01

    In an effort to simulate the compromised function and atrophy of lower limb muscles experienced by astronauts after spaceflight, 21 men and women age 30-56 yr were subjected to unilateral lower limb unloading for 5 wk. Whereas 10 of these subjects performed unilateral knee extensor resistance exercise (ULRE) two or three times weekly, 11 subjects (UL) refrained from training. The exercise regimen consisted of four sets of seven maximal actions, using an apparatus that offers concentric and eccentric resistance by utilizing the inertia of rotating flywheel(s). Knee extensor muscle strength was measured before and after UL and ULRE, and knee extensor and ankle plantar flexor muscle volumes were determined by means of magnetic resonance imaging. Surface electromyographic activity measured after UL inferred increased muscle use to perform a given motor task. UL induced an 8.8% decrease (P < 0.05) in knee extensor muscle volume. After ULRE and as a result of only approximately 16 min of maximal contractile activity over the 5-wk course, muscle volume increased 7.7% (P < 0.05). Muscle strength decreased 24-32% (P < 0.05) in response to UL. Group ULRE showed maintained (P > 0.05) strength. Ankle plantar flexor muscle volume of the unloaded limb decreased (P < 0.05) in both groups (UL 10.5%; ULRE 11.1%). In neither group did the right weight-bearing limb show any change (P > 0.05) in muscle volume or strength. The results of this study provide evidence that resistance exercise not only may offset muscle atrophy but is in fact capable of promoting marked hypertrophy of chronically unloaded muscle. PMID:14660503

  4. Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids.

    PubMed

    Mourtzakis, Marina; Saltin, Bengt; Graham, Terry; Pilegaard, Henriette

    2006-06-01

    During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44+/-1% peak oxygen consumption (mean+/-SE) until exhaustion (exhaustion at 3 h 23 min+/-11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout (P<0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (approximately 30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake (P<0.05) was also associated with decreasing PDH activity (P<0.05) and increased PDH kinase 4 mRNA (P<0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised approximately 68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise. PMID:16424076

  5. Muscle ultrastructural changes from exhaustive exercise performed after prolonged restricted activity and retraining in dogs

    NASA Technical Reports Server (NTRS)

    Nazar, K.; Greenleaf, J. E.; Philpott, D.; Pohoska, E.; Olszewska, K.; Kaciuba-Uscilko, H.

    1991-01-01

    The effect of exhaustive treadmill exercise on ultrastructural changes in the quadriceps femoris muscle was studied in 7 normal, healthy dogs, before and after restricted activity (RA), and following a subsequent 2 month treadmill exercise retraining period for the 5 mo group. Mean time to exhaustion in the 2 mo group decreased from 177 + or - 22 min before to 90 + or - 32 min after RA. Retraining increased tolerance to 219 + or - 73 min; 24 pct. above the before RA and 143 pct. above the after RA time. After RA exhaustion time in the 5 mo group was 25 and 45 min. Before RA, pre-exercise muscle structure was normal and post exercise there was only slight swelling of mitochondria. After RA, pre-exercise, numerous glycogen granules and lipid droplets appeared in the muscle fibers, mitochondria were smaller, and sarcoplasmic reticulum channels widened; post exercise these changes were accentuated and some areas were devoid of glycogen, and there was fiber degradation. After 5 mo RA pre-exercise there were more pronounced changes; mitochondria were very small and dense, there were many lipid droplets, myofibrils were often separated, and the fibers appeared edematous and degenerating; post exercise the sarcoplasmic reticulum was swollen, no glycogen was present, and there was marked swelling and deformation of mitochondria. After retraining, both pre-exercise and post exercise there was still evidence of fiber degeneration. Thus, susceptibility of active skeletal muscle structures and subcellular elements, e.g., mitochondria, to the action of damaging factors occurring during exhaustive exercise is enhanced considerably by prolonged disuse.

  6. Changes in Voluntary Activation Assessed by Transcranial Magnetic Stimulation during Prolonged Cycling Exercise

    PubMed Central

    Perrey, Stephane; Temesi, John; Wuyam, Bernard; Levy, Patrick; Verges, Samuel; Millet, Guillaume Y.

    2014-01-01

    Maximal central motor drive is known to decrease during prolonged exercise although it remains to be determined whether a supraspinal deficit exists, and if so, when it appears. The purpose of this study was to evaluate corticospinal excitability and muscle voluntary activation before, during and after a 4-h cycling exercise. Ten healthy subjects performed three 80-min bouts on an ergocycle at 45% of their maximal aerobic power. Before exercise and immediately after each bout, neuromuscular function was evaluated in the quadriceps femoris muscles under isometric conditions. Transcranial magnetic stimulation was used to assess voluntary activation at the cortical level (VATMS), corticospinal excitability via motor-evoked potential (MEP) and intracortical inhibition by cortical silent period (CSP). Electrical stimulation of the femoral nerve was used to measure voluntary activation at the peripheral level (VAFNES) and muscle contractile properties. Maximal voluntary force was significantly reduced after the first bout (13±9%, P<0.01) and was further decreased (25±11%, P<0.001) at the end of exercise. CSP remained unchanged throughout the protocol. Rectus femoris and vastus lateralis but not vastus medialis MEP normalized to maximal M-wave amplitude significantly increased during cycling. Finally, significant decreases in both VATMS and VAFNES (∼8%, P<0.05 and ∼14%, P<0.001 post-exercise, respectively) were observed. In conclusion, reductions in VAFNES after a prolonged cycling exercise are partly explained by a deficit at the cortical level accompanied by increased corticospinal excitability and unchanged intracortical inhibition. When comparing the present results with the literature, this study highlights that changes at the cortical and/or motoneuronal levels depend not only on the type of exercise (single-joint vs. whole-body) but also on exercise intensity and/or duration. PMID:24586559

  7. Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use

    PubMed Central

    Boon, Hanneke; Gijsen, Annemie P.; Stegen, Jos H. C. H.; Kuipers, Harm; van Loon, Luc J. C.

    2007-01-01

    Using contemporary stable-isotope methodology and fluorescence microscopy, we assessed the impact of carbohydrate supplementation on whole-body and fiber-type-specific intramyocellular triacylglycerol (IMTG) and glycogen use during prolonged endurance exercise. Ten endurance-trained male subjects were studied twice during 3 h of cycling at 63 ± 4% of maximal O2 uptake with either glucose ingestion (CHO trial; 0.7 g CHO kg−1 h−1) or without (CON placebo trial; water only). Continuous infusions with [U-13C] palmitate and [6,6-2H2] glucose were applied to quantify plasma free fatty acids (FFA) and glucose oxidation rates and to estimate intramyocellular lipid and glycogen use. Before and after exercise, muscle biopsy samples were taken to quantify fiber-type-specific IMTG and glycogen content. Plasma glucose rate of appearance (Ra) and carbohydrate oxidation rates were substantially greater in the CHO vs CON trial. Carbohydrate supplementation resulted in a lower muscle glycogen use during the first hour of exercise in the CHO vs CON trial, resulting in a 38 ± 19 and 57 ± 22% decreased utilization in type I and II muscle-fiber glycogen content, respectively. In the CHO trial, both plasma FFA Ra and subsequent plasma FFA concentrations were lower, resulting in a 34 ± 12% reduction in plasma FFA oxidation rates during exercise (P < 0.05). Carbohydrate intake did not augment IMTG utilization, as fluorescence microscopy revealed a 76 ± 21 and 78 ± 22% reduction in type I muscle-fiber lipid content in the CHO and CON trial, respectively. We conclude that carbohydrate supplementation during prolonged cycling exercise does not modulate IMTG use but spares muscle glycogen use during the initial stages of exercise in endurance-trained men. PMID:17333244

  8. Interaction of hyperthermia and heart rate on stroke volume during prolonged exercise.

    PubMed

    Trinity, Joel D; Pahnke, Matthew D; Lee, Joshua F; Coyle, Edward F

    2010-09-01

    People who become hyperthermic during exercise display large increases in heart rate (HR) and reductions in stroke volume (SV). It is not clear if the reduction in SV is due primarily to hyperthermia or if it is a secondary effect of an elevation in HR reducing ventricular filling. In the present study, the upward drift of HR during prolonged exercise was prevented by a very small dose of the β1-adrenoreceptor blocker (atenolol; βB), thus allowing SV to be compared at a given HR during normothermia and hyperthermia. Eleven men cycled for 60 min at 57% of peak O2 uptake after receiving placebo control (PL) or a low dose (0.2 mg/kg) of βB. Hyperthermia was induced by reducing heat dissipation during exercise. Four experimental conditions were studied: normothermia-PL, normothermia-βB, hyperthermia-PL, and hyperthermia-βB. Hyperthermia increased skin and core temperature by 4.3 degrees C and 0.8 degrees C (P<0.01), respectively. βB prevented HR elevation with hyperthermia: HR values were similar at minute 60 during normothermia-PL and hyperthermia-βB (155±11 and 154±13 beats/min, respectively, P=0.82). However, SV was increased by 7% during the final 20 min of exercise during hyperthermia-βB compared with normothermia-PL (treatment×time interaction, P=0.03). In conclusion, when matched for HR, mild hyperthermia increased SV during exercise. Furthermore, the reduction in SV throughout prolonged exercise under normothermic and mildly hyperthermic conditions appears to be due to the increase in HR. PMID:20595543

  9. Reduced mechanical efficiency in chronic obstructive pulmonary disease but normal peak VO2 with small muscle mass exercise.

    PubMed

    Richardson, Russell S; Leek, Bryan T; Gavin, Timothy P; Haseler, Luke J; Mudaliar, Sundar R D; Henry, Robert; Mathieu-Costello, Odile; Wagner, Peter D

    2004-01-01

    We studied six patients with chronic obstructive pulmonary disease (COPD) (FEV1 = 1.1 +/- 0.2 L, 32% of predicted) and six age- and activity level-matched control subjects while performing both maximal bicycle exercise and single leg knee-extensor exercise. Arterial and femoral venous blood sampling, thermodilution blood flow measurements, and needle biopsies allowed the assessment of muscle oxygen supply, utilization, and structure. Maximal work rates and single leg VO2max (control subjects = 0.63 +/- 0.1; patients with COPD = 0.37 +/- 0.1 L/minute) were significantly greater in the control group during bicycle exercise. During knee-extensor exercise this difference in VO2max disappeared, whereas maximal work capacity was reduced (flywheel resistance: control subjects = 923 +/- 198; patients with COPD = 612 +/- 81 g) revealing a significantly reduced mechanical efficiency (work per unit oxygen consumed) with COPD. The patients had an elevated number of less efficient type II muscle fibers, whereas muscle fiber cross-sectional areas, capillarity, and mitochondrial volume density were not different between the groups. Therefore, although metabolic capacity per se is unchanged, fiber type differences associated with COPD may account for the reduced muscular mechanical efficiency that becomes clearly apparent during knee-extensor exercise, when muscle function is no longer overshadowed by the decrement in lung function. PMID:14500263

  10. Effect of exercise-induced fatigue on postural control of the knee.

    PubMed

    Hassanlouei, H; Arendt-Nielsen, L; Kersting, U G; Falla, D

    2012-06-01

    Muscle fatigue is associated with reduced power output and work capacity of the skeletal muscle. Fatigue-induced impairments in muscle function are believed to be a potential cause of increased injury rates during the latter stages of athletic competition and often occur during unexpected perturbations. However the effect of fatigue on functionally relevant, full body destabilizing perturbations has not been investigated. This study examines the effect of muscle fatigue on the activation of the quadriceps and hamstrings to fast, full body perturbations evoked by a moveable platform. Surface electromyographic (EMG) signals were recorded from the knee extensor (vastus medialis, rectus femoris, and vastus lateralis) and flexor muscles (biceps femoris and semitendinosus) of the right leg in nine healthy men during full body perturbations performed at baseline and immediately following high intensity exercise performed on a bicycle ergometer. In each condition, participants stood on a moveable platform during which 16 randomized postural perturbations (eight repetitions of two perturbation types: 8 cm forward slides, 8 cm backward slides) with varying inter-perturbation time intervals were performed over a period of 2-3 min. Maximal voluntary knee extension force was measured before and after the high intensity exercise protocol to confirm the presence of fatigue. Immediately after exercise, the maximal force decreased by 63% and 66% for knee extensors and flexors, respectively (P<0.0001). During the post-exercise postural perturbations, the EMG average rectified value (ARV) was significantly lower than the baseline condition for both the knee extensors (average across all muscles; baseline: 19.7±25.4μV, post exercise: 16.2±19.4 μV) and flexors (baseline: 24.3±20.9 μV, post exercise: 13.8±11.0 μV) (both P<0.05). Moreover the EMG onset was significantly delayed for both the knee extensors (baseline: 132.7±32.9 ms, post exercise: 170.8±22.9 ms) and flexors

  11. Timing Carbohydrate Beverage Intake During Prolonged Moderate Intensity Exercise Does Not Affect Cycling Performance

    PubMed Central

    SCHWEITZER, GEORGE G.; SMITH, JOHN D.; LECHEMINANT, JAMES D.

    2009-01-01

    Carbohydrate beverages consumed during long-term exercise have been shown to attenuate fatigue and improve performance; however, the optimal timing of ingestion is unclear. Therefore, the purpose of this study was to determine if timing the carbohydrate ingestion (continual loading (CL), front-loading (FL), and end-loading (EL)) during prolonged exercise influenced exercise performance in competitive cyclists. Ten well-trained cyclists completed three separate exercise bouts on a bicycle ergometer, each lasting 2 hours at an intensity of ~67% VO2 max, followed by a 15-minute “all out” time trial. In the CL trial, a carbohydrate beverage was ingested throughout the trial. In the FL trial, participants ingested a carbohydrate beverage during the first hour and a placebo beverage during the second hour. In the EL trial, a carbohydrate beverage was ingested during the second hour and a placebo during the first hour. The amount of carbohydrate consumed (75 g) was the same among conditions. The order of conditions was single-blinded, counterbalanced, and determined randomly. Performance was measured by the work output during the 15-minute performance ride. There were no differences in work output among the three conditions during the final time trial. In the first hour of exercise, peak venous blood glucose was highest in the FL condition. In the second hour, peak venous blood glucose was highest in the EL condition. Following the time trial, venous blood glucose levels were similar among CL, FL, and EL. Overall, the timing of carbohydrate beverage consumption during prolonged moderate intensity cycling did not alter cycling performance.

  12. Life-long spontaneous exercise does not prolong lifespan but improves health span in mice

    PubMed Central

    2013-01-01

    Background Life expectancy at birth in the first world has increased from 35 years at the beginning of the 20th century to more than 80 years now. The increase in life expectancy has resulted in an increase in age-related diseases and larger numbers of frail and dependent people. The aim of our study was to determine whether life-long spontaneous aerobic exercise affects lifespan and healthspan in mice. Results Male C57Bl/6J mice, individually caged, were randomly assigned to one of two groups: sedentary (n = 72) or spontaneous wheel-runners (n = 72). We evaluated longevity and several health parameters including grip strength, motor coordination, exercise capacity (VO2max) and skeletal muscle mitochondrial biogenesis. We also measured the cortical levels of the brain-derived neurotrophic factor (BDNF), a neurotrophin associated with brain plasticity. In addition, we measured systemic oxidative stress (malondialdehyde and protein carbonyl plasma levels) and the expression and activity of two genes involved in antioxidant defense in the liver (that is, glutathione peroxidase (GPx) and manganese superoxide dismutase (Mn-SOD)). Genes that encode antioxidant enzymes are considered longevity genes because their over-expression may modulate lifespan. Aging was associated with an increase in oxidative stress biomarkers and in the activity of the antioxidant enzymes, GPx and Mn-SOD, in the liver in mice. Life-long spontaneous exercise did not prolong longevity but prevented several signs of frailty (that is, decrease in strength, endurance and motor coordination). This improvement was accompanied by a significant increase in the mitochondrial biogenesis in skeletal muscle and in the cortical BDNF levels. Conclusion Life-long spontaneous exercise does not prolong lifespan but improves healthspan in mice. Exercise is an intervention that delays age-associated frailty, enhances function and can be translated into the clinic. PMID:24472376

  13. The Effects of Montmorency Tart Cherry Concentrate Supplementation on Recovery Following Prolonged, Intermittent Exercise.

    PubMed

    Bell, Phillip G; Stevenson, Emma; Davison, Gareth W; Howatson, Glyn

    2016-01-01

    This study investigated Montmorency tart cherry concentrate (MC) supplementation on markers of recovery following prolonged, intermittent sprint activity. Sixteen semi-professional, male soccer players, who had dietary restrictions imposed for the duration of the study, were divided into two equal groups and consumed either MC or placebo (PLA) supplementation for eight consecutive days (30 mL twice per day). On day 5, participants completed an adapted version of the Loughborough Intermittent Shuttle Test (LISTADAPT). Maximal voluntary isometric contraction (MVIC), 20 m Sprint, counter movement jump (CMJ), agility and muscle soreness (DOMS) were assessed at baseline, and 24, 48 and 72 h post-exercise. Measures of inflammation (IL-1-β, IL-6, IL-8, TNF-α, hsCRP), muscle damage (CK) and oxidative stress (LOOH) were analysed at baseline and 1, 3, 5, 24, 48 and 72 h post-exercise. Performance indices (MVIC, CMJ and agility) recovered faster and muscle soreness (DOMS) ratings were lower in the MC group (p < 0.05). Additionally, the acute inflammatory response (IL-6) was attenuated in the MC group. There were no effects for LOOH and CK. These findings suggest MC is efficacious in accelerating recovery following prolonged, repeat sprint activity, such as soccer and rugby, and lends further evidence that polyphenol-rich foods like MC are effective in accelerating recovery following various types of strenuous exercise. PMID:27455316

  14. The Effects of Montmorency Tart Cherry Concentrate Supplementation on Recovery Following Prolonged, Intermittent Exercise

    PubMed Central

    Bell, Phillip G.; Stevenson, Emma; Davison, Gareth W.; Howatson, Glyn

    2016-01-01

    This study investigated Montmorency tart cherry concentrate (MC) supplementation on markers of recovery following prolonged, intermittent sprint activity. Sixteen semi-professional, male soccer players, who had dietary restrictions imposed for the duration of the study, were divided into two equal groups and consumed either MC or placebo (PLA) supplementation for eight consecutive days (30 mL twice per day). On day 5, participants completed an adapted version of the Loughborough Intermittent Shuttle Test (LISTADAPT). Maximal voluntary isometric contraction (MVIC), 20 m Sprint, counter movement jump (CMJ), agility and muscle soreness (DOMS) were assessed at baseline, and 24, 48 and 72 h post-exercise. Measures of inflammation (IL-1-β, IL-6, IL-8, TNF-α, hsCRP), muscle damage (CK) and oxidative stress (LOOH) were analysed at baseline and 1, 3, 5, 24, 48 and 72 h post-exercise. Performance indices (MVIC, CMJ and agility) recovered faster and muscle soreness (DOMS) ratings were lower in the MC group (p < 0.05). Additionally, the acute inflammatory response (IL-6) was attenuated in the MC group. There were no effects for LOOH and CK. These findings suggest MC is efficacious in accelerating recovery following prolonged, repeat sprint activity, such as soccer and rugby, and lends further evidence that polyphenol-rich foods like MC are effective in accelerating recovery following various types of strenuous exercise. PMID:27455316

  15. Tyrosine supplementation does not influence the capacity to perform prolonged exercise in a warm environment.

    PubMed

    Watson, Phillip; Enever, Sophie; Page, Andrew; Stockwell, Jenna; Maughan, Ronald J

    2012-10-01

    Eight young men were recruited to a study designed to examine the effect of tyrosine (TYR) supplementation on the capacity to perform prolonged exercise in a warm environment. Subjects entered the laboratory in the morning and remained seated for 1 hr before cycling to exhaustion at 70% VO2peak. Two 250-ml aliquots of a placebo (PLA ) or a TYR solution were ingested at 30-min intervals before exercise, with an additional 150 ml consumed every 15 min throughout exercise (total TYR dose: 150 mg/kg BM). Cognitive function was assessed before drink ingestion, at the end of the rest period, and at exhaustion. TYR ingestion had no effect on exercise capacity (PLA 61.4 ± 13.7 min, TYR 60.2 ± 15.4 min; p = .505). No differences in heart rate (p = .380), core temperature (p = .554), or weighted mean skin temperature (p = .167) were apparent between trials. Ingestion of TYR produced a marked increase in serum TYR concentrations (+236 ± 46 μmol/L; p < .001), with this difference maintained throughout exercise. No change was apparent during the PLA trial (p = .924). Exercise caused an increase in error rate during the complex component of the Stroop test (p = .034), but this response was not influenced by the drink ingested. No other component of cognitive function was altered by the protocol (all p > .05). Ingestion of a TYR solution did not influence time to exhaustion or several aspects of cognitive function when exercise was undertaken in a warm environment. PMID:23011654

  16. Cardiovascular strain impairs prolonged self-paced exercise in the heat.

    PubMed

    Périard, Julien D; Cramer, Matthew N; Chapman, Phillip G; Caillaud, Corinne; Thompson, Martin W

    2011-02-01

    It has been proposed that self-paced exercise in the heat is regulated by an anticipatory reduction in work rate based on the rate of heat storage. However, performance may be impaired by the development of hyperthermia and concomitant rise in cardiovascular strain increasing relative exercise intensity. This study evaluated the influence of thermal strain on cardiovascular function and power output during self-paced exercise in the heat. Eight endurance-trained cyclists performed a 40 km simulated time trial in hot (35°C) and thermoneutral conditions (20°C), while power output, mean arterial pressure, heart rate, oxygen uptake and cardiac output were measured. Time trial duration was 64.3 ± 2.8 min (242.1 W) in the hot condition and 59.8 ± 2.6 min (279.4 W) in the thermoneutral condition (P < 0.01). Power output in the heat was depressed from 20 min onwards compared with exercise in the thermoneutral condition (P < 0.05). Rectal temperature reached 39.8 ± 0.3 (hot) and 38.9 ± 0.2°C (thermoneutral; P < 0.01). From 10 min onwards, mean skin temperature was ~7.5°C higher in the heat, and skin blood flow was significantly elevated (P < 0.01). Heart rate was ~8 beats min(-1) higher throughout hot exercise, while stroke volume, cardiac output and mean arterial pressure were significantly depressed compared with the thermoneutral condition (P < 0.05). Peak oxygen uptake measured during the final kilometre of exercise at maximal effort reached 77 (hot) and 95% (thermoneutral) of pre-experimental control values (P < 0.01). We conclude that a thermoregulatory-mediated rise in cardiovascular strain is associated with reductions in sustainable power output, peak oxygen uptake and maximal power output during prolonged, intense self-paced exercise in the heat. PMID:20851861

  17. Water and carbohydrate ingestion during prolonged exercise increase maximal neuromuscular power.

    PubMed

    Fritzsche, R G; Switzer, T W; Hodgkinson, B J; Lee, S H; Martin, J C; Coyle, E F

    2000-02-01

    This study investigated the individual and combined effects of water and carbohydrate ingestion during prolonged cycling on maximal neuromuscular power (P(max)), thermoregulation, cardiovascular function, and metabolism. Eight endurance-trained cyclists exercised for 122 min at 62% maximal oxygen uptake in a 35 degrees C environment (50% relative humidity, 2 m/s fan speed). P(max) was measured in triplicate during 6-min periods beginning at 26, 56, 86, and 116 min. On four different occasions, immediately before and during exercise, subjects ingested 1) 3.28 +/- 0.21 liters of water with no carbohydrate (W); 2) 3.39 +/- 0.23 liters of a solution containing 204 +/- 14 g of carbohydrate (W+C); 3) 204 +/- 14 g of carbohydrate in only 0.49 +/- 0.03 liter of solution (C); and 4) 0. 37 +/- 0.02 liter of water with no carbohydrate (placebo; Pl). These treatments were randomized, disguised, and presented double blind. At 26 min of exercise, P(max) was similar in all trials. From 26 to 116 min, P(max) declined 15.2 +/- 3.3 and 14.5 +/- 2.1% during C and Pl, respectively; 10.4 +/- 1.9% during W (W > C, W > Pl; P < 0.05); and 7.4 +/- 2.2% during W+C (W+C > W, W+C > C, and W+C > Pl; P < 0. 05). As an interesting secondary findings, we also observed that carbohydrate ingestion increased heat production, final core temperature, and whole body sweating rate. We conclude that, during prolonged moderate-intensity exercise in a warm environment, ingestion of W attenuates the decline in P(max). Furthermore, ingestion of W+C attenuates the decline in maximal power more than does W alone, and ingestion of C alone does not attenuate the decline in P(max) compared with Pl. PMID:10658044

  18. The effects of ingesting polylactate or glucose polymer drinks during prolonged exercise.

    PubMed

    Fahey, T D; Larsen, J D; Brooks, G A; Colvin, W; Henderson, S; Lary, D

    1991-09-01

    Five trained, fasted male cyclists rode a cycle ergometer three times at 50% of VO2max for 180 min. Using a balanced order, double-blind procedure, subjects were given either a solution containing polylactate (PL: 80% polylactate, 20% sodium lactate, in 7% solution with water), glucose polymer (GP: multidextrin in 7% solution with water), or control (C: water sweetened with aspartame) 5 min before exercise and at 20-min intervals during exercise. Venous blood samples were taken at rest and at 20-min intervals during exercise. In general, PL and GP rendered similar results except that pH and bicarbonate (HCO3-) were higher in PL. There were no differences between treatments in perceived exertion, sodium, potassium, chloride, lactate, heart rate, oxygen consumption, rectal temperature, or selected skin temperatures. These data show that polylactate may help maintain blood glucose and enhance blood buffering capacity during prolonged exercise and could be a useful component in an athletic fluid replacement beverage. PMID:1844999

  19. Effects of selective cooling of the facial area on physiological and metabolic output during graded maximal or prolonged submaximal exercise

    NASA Astrophysics Data System (ADS)

    Quirion, A.; Boisvert, P.; Brisson, G. R.; Decarufel, D.; Laurencelle, L.; Dulac, S.; Vogelaere, P.; Therminarias, A.

    1989-06-01

    Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65%dot VO_2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10°C, 4.6 m s-1). Facial cooling at the end of graded maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (dot VO_2 max), maximal heart rate (HR max), rectal temperature ( T re), work-load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work-load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.

  20. Glucose kinetics during prolonged exercise in highly trained human subjects: effect of glucose ingestion

    PubMed Central

    Jeukendrup, Asker E; Raben, Anne; Gijsen, Annemie; Stegen, Jos H C H; Brouns, Fred; Saris, Wim H M; Wagenmakers, Anton J M

    1999-01-01

    The objectives of this study were (1) to investigate whether glucose ingestion during prolonged exercise reduces whole body muscle glycogen oxidation, (2) to determine the extent to which glucose disappearing from the plasma is oxidized during exercise with and without carbohydrate ingestion and (3) to obtain an estimate of gluconeogenesis. After an overnight fast, six well-trained cyclists exercised on three occasions for 120 min on a bicycle ergometer at 50% maximum velocity of O2 uptake and ingested either water (Fast), or a 4% glucose solution (Lo-Glu) or a 22% glucose solution (Hi-Glu) during exercise. Dual tracer infusion of [U-13C]-glucose and [6,6-2H2]-glucose was given to measure the rate of appearance (Ra) of glucose, muscle glycogen oxidation, glucose carbon recycling, metabolic clearance rate (MCR) and non-oxidative disposal of glucose. Glucose ingestion markedly increased total Ra especially with Hi-Glu. After 120 min Ra and rate of disappearance (Rd) of glucose were 51-52 μmol kg−1 min−1 during Fast, 73-74 μmol kg−1 min−1 during Lo-Glu and 117–119 μmol kg−1 min−1 during Hi-Glu. The percentage of Rd oxidized was between 96 and 100% in all trials. Glycogen oxidation during exercise was not reduced by glucose ingestion. The vast majority of glucose disappearing from the plasma is oxidized and MCR increased markedly with glucose ingestion. Glucose carbon recycling was minimal suggesting that gluconeogenesis in these conditions is negligible. PMID:10050023

  1. Treadmill Exercise Within LBNP as an Integrated Coutermeasure to Microgravity

    NASA Technical Reports Server (NTRS)

    Lee, Stuart; Hargens, A. R.; Schneider, S. M.; Watenpaugh, D. E.

    2010-01-01

    An integrated exercise countermeasure for microgravity is needed to protect multiple physiologic systems and save crew time. Such a countermeasure should protect orthostatic tolerance, upright ambulatory capability (including sprinting), aerobic capacity, muscle strength/endurance, and other physiologic parameters relevant to human performance. We developed a novel physiologic countermeasure, treadmill exercise within LBNP, for preventing cardiovascular and musculoskeletal deconditioning associated with prolonged bed rest and spaceflight. We evaluated 40 min of daily LBNP treadmill exercise by a battery of physiologic parameters relevant to maintaining exercise performance and health of both women and men during bed-rest (simulated microgravity) studies lasting from 5 to 60 days. For 30 day studies, we employed identical twins with one twin as the control and the other twin as the exerciser to improve comparative power. During the WISE 60-day HDT study, the treadmill exercise within LBNP was performed 3-4 days each week and resistive exercise was performed 2-3 days each week. Our treadmill within LBNP protocol maintained plasma volume and sprint speed (30 day HDT bed-rest studies of identical twins), orthostatic tolerance to a degree, upright exercise capacity, muscle strength and endurance, and some bone parameters during 30 day (twin studies) and 60 day (WISE-2005) bed-rest simulations of microgravity. When combining treadmill exercise within LBNP and resistive exercise (WISE), cardiac mass increased significantly in the exercise (EX) group during bed rest relative to controls (CON). Upright peak VO2, and knee extensor strength and endurance decreased significantly in CON subjects; but these parameters were preserved in the EX group. In the 60 day WISE study, each LBNP exercise session was followed immediately by 10 minutes of static LBNP, and the last such session occurred three days before the end of bed rest. Still, orthostatic tolerance was better maintained

  2. Menstrual cycle phase effects free testosterone responses to prolonged aerobic exercise.

    PubMed

    Lane, A R; O'Leary, C B; Hackney, A C

    2015-09-01

    Research has shown that total testosterone (tT) levels in women increase acutely during a prolonged bout of aerobic exercise. Few studies, however, have considered the impact of the menstrual cycle phase on this response or have looked at the biologically active free testosterone (fT) form responses. Therefore, this study examined the fT concentration response independently and as a percentage (fT%) of tT to prolonged aerobic exercise during phases of the menstrual cycle with low estrogen-progesterone (L-EP; i.e., follicular phase) and high estrogen-progesterone (H-EP; i.e., luteal phase). Ten healthy, recreationally trained, eumennorrheic women (X ± SD: age = 20 ± 2 y, mass = 58.7 ± 8.3 kg, body fat = 22.3 ± 4.9 %, VO(2max) = 50.7 ± 9.0 ml/kg/min) participated in a laboratory based study and completed a 60-minute treadmill run during the L-EP and H-EP menstrual phases at ~70% of VO(2max). Blood was drawn prior to (PRE), immediately after (POST) and following 30 minutes of recovery (30POST) with each 60-minute run. During H-EP, there was a significant increase in fT concentrations from PRE to POST (p < 0.01) while in L-EP fT levels were unchanged; which resulted in fT being significantly higher at H-EP POST versus L-EP POST (p < 0.03). Area-under-the-curve (AUC) responses were calculated, for fT the total AUC was greater in H-EP than L-EP (p < 0.04). There was no significant interaction of fT% between phases and exercise sampling time. There was, however, a main effect for exercise where fT% POST was a greater proportion of tT than at PRE (p < 0.01). In summary, hormonal changes associated with the menstrual cycle impact fT response to a prolonged aerobic exercise bout; specifically, there being higher levels under H-EP conditions. This suggests more biologically active T is available during exercise in this phase. This response may be a function of the higher core temperatures found with H-EP causing greater sex hormone binding protein release of T, or could

  3. Effect of initial core temperature on hyperthermic hyperventilation during prolonged submaximal exercise in the heat.

    PubMed

    Tsuji, Bun; Honda, Yasushi; Fujii, Naoto; Kondo, Narihiko; Nishiyasu, Takeshi

    2012-01-01

    We investigated whether a core temperature threshold for hyperthermic hyperventilation is seen during prolonged submaximal exercise in the heat when core temperature before the exercise is reduced and whether the evoked hyperventilatory response is affected by altering the initial core temperature. Ten male subjects performed three exercise trials at 50% of peak oxygen uptake in the heat (37°C and 50% relative humidity) after altering their initial esophageal temperature (T(es)). Initial T(es) was manipulated by immersion for 25 min in water at 18°C (Precooling), 35°C (Control), or 40°C (Preheating). T(es) after the water immersion was significantly higher in the Preheating trial (37.5 ± 0.3°C) and lower in the Precooling trial (36.1 ± 0.3°C) than in the Control trial (36.9 ± 0.3°C). In the Precooling trial, minute ventilation (Ve) showed little change until T(es) reached 37.1 ± 0.4°C. Above this core temperature threshold, Ve increased linearly in proportion to increasing T(es). In the Control trial, Ve increased as T(es) increased from 37.0°C to 38.6°C after the onset of exercise. In the Preheating trial, Ve increased from the initially elevated levels of T(es) (from 37.6 to 38.6°C) and Ve. The sensitivity of Ve to increasing T(es) above the threshold for hyperventilation (the slope of the T(es)-Ve relation) did not significantly vary across trials (Precooling trial = 10.6 ± 5.9, Control trial = 8.7 ± 5.1, and Preheating trial = 9.2 ± 6.9 L·min(-1)·°C(-1)). These results suggest that during prolonged submaximal exercise at a constant workload in humans, there is a clear core temperature threshold for hyperthermic hyperventilation and that the evoked hyperventilatory response is unaffected by altering initial core temperature. PMID:21957164

  4. Branched-chain amino acid supplementation during repeated prolonged skiing exercises at altitude.

    PubMed

    Bigard, A X; Lavier, P; Ullmann, L; Legrand, H; Douce, P; Guezennec, C Y

    1996-09-01

    This study was conducted to test the hypothesis that a branched-chain amino acid (BCAA) supplementation would minimize changes in body composition and alterations in plasma amino acid profile induced by prolonged exercises at altitude. Twenty-four highly trained subjects participated in six successive sessions of ski mountaineering (6-8 hr duration, altitude 2,500-4,100 m). Twelve subjects took a dietary supplement of BCAA (BCAA group) and 12 took a dietary supplement that was 98% carbohydrate (C group). Body weight decreased in C subjects (-2.1%, p < .01), while the body weight loss recorded in the BCAA group was not statistically significant (-1.2%, NS). Changes in body composition that resulted from repeated skiing exercise at altitude were not significantly minimized by BCAA administration. Peak power output recorded during an incremental bicycle exercise decreased in C subjects but did not change significantly in BCAA subjects. Results of this study demonstrate that neither changes in body composition related to the ski mountaineering program nor muscular performance during isometric contraction was significantly affected by BCAA administration. PMID:8876349

  5. Dietary selenium and prolonged exercise alter gene expression and activity of antioxidant enzymes in equine skeletal muscle.

    PubMed

    White, S H; Johnson, S E; Bobel, J M; Warren, L K

    2016-07-01

    Untrained Thoroughbred horses (6 mares and 6 geldings; 11 yr [SE 1] and 565 kg [SE 11]) were used to evaluate antioxidant gene expression and enzyme activity in blood and skeletal muscle in response to prolonged exercise after receiving 2 levels of dietary selenium for 36 d: 0.1 (CON; = 6) or 0.3 mg/kg DM (SEL; = 6). Horses were individually fed 1.6% BW coastal bermudagrass hay, 0.4% BW whole oats, and a mineral/vitamin premix containing no Se. Sodium selenite was added to achieve either 0.1 or 0.3 mg Se/kg DM in the total diet. On d 35, horses underwent 2 h of submaximal exercise in a free-stall exerciser. Blood samples were obtained before (d 0) and after 34 d of Se supplementation and on d 35 to 36 immediately after exercise and at 6 and 24 h after exercise. Biopsies of the middle gluteal muscle were obtained on d 0, before exercise on d 34, and at 6 and 24 h after exercise. Supplementation with Se above the NRC requirement (SEL) increased serum Se ( = 0.011) and muscle thioredoxin reductase (TrxR) activity ( = 0.051) but had no effect on glutathione peroxidase (GPx) activity in plasma, red blood cell (RBC) lysate, or muscle in horses at rest. Serum creatine kinase activity increased ( < 0.0001) in response to prolonged exercise but was not affected by dietary treatment. Serum lipid hydroperoxides were affected by treatment ( = 0.052) and were higher ( = 0.012) in horses receiving CON than SEL immediately following exercise. Muscle expression of was unchanged at 6 h but increased ( = 0.005) 2.8-fold 24 h after exercise, whereas muscle TrxR activity remained unchanged. Glutathione peroxidase activity increased in plasma (P < 0.0001) and decreased in RBC lysate ( = 0.010) after prolonged exercise. A Se treatment × time interaction was observed for RBC GPx activity (P = 0.048). Muscle and expression and GPx activity did not change during the 24-h period after exercise. Level of dietary Se had no overall effect on expression of , , , , , , or in muscle following

  6. Hyperinsulinemia prevents prolonged hyperglycemia after intense exercise in insulin-dependent diabetic subjects.

    PubMed

    Sigal, R J; Purdon, C; Fisher, S J; Halter, J B; Vranic, M; Marliss, E B

    1994-10-01

    Hyperglycemia with accompanying hyperinsulinemia occurs after brief, greater than 85% maximum oxygen consumption exercise to exhaustion in normal subjects and persists up to 60 min of recovery. To determine the importance of endogenous insulin secretion during and after intense exercise, responses to exercise of lean fit male post-absorptive insulin-dependent diabetes mellitus (IDDM) subjects, aged 18-34 yr, were compared with those of control subjects (C; n = 6). Three iv insulin protocols were employed: hyperglycemic (HG; n = 7) and euglycemic (EG1; n = 6) with constant insulin infusion, and euglycemic with doubled insulin infusion during recovery (EG2; n = 6). Overnight iv insulin was adjusted to achieve prolonged euglycemia (5.4 +/- 0.3 mmol/L) or hyperglycemia (8.6 +/- 0.3 mmol/L) before exercise. This allowed for comparisons between HG and EG1 (constant infusion) and between C and EG2 (to approximate physiological hyperinsulinemia by doubling the infusion rates at exhaustion for 56 +/- 7 min during recovery). Subjects exercised to 89-98% of their individual maximum oxygen consumption for 12.8 +/- 0.3 min. Glycemia increased to maximum values at 6 min of recovery (9.8 +/- 0.5 in HG, 6.9 +/- 0.4 in EG1, 7.3 +/- 0.3 in EG2, and 6.9 +/- 0.4 mmol/L in C). Whereas in EG2 and C, glucose returned to resting values in 50-80 min, it remained elevated at 120 min recovery in HG and EG1. During exercise, [3-3H]-glucose-determined glucose production increased markedly and exceeded disappearance in all groups, but less so in the HG subjects than in the other groups. An early recovery decline in glucose production did not differ among groups, but MCR (rate of glucose disappearance/glycemia) were markedly lower in HG and EG1, in whom plasma free insulin remained unchanged from 15 min of recovery onward (MCR, 1.6-1.9 vs. 2.3-2.8 mL/kg.min in C). Doubling the insulin infusion rate in EG2 restored the MCR response to that of C subjects. In summary, constant insulin infusion is

  7. Dehydration accelerates reductions in cerebral blood flow during prolonged exercise in the heat without compromising brain metabolism.

    PubMed

    Trangmar, Steven J; Chiesa, Scott T; Llodio, Iñaki; Garcia, Benjamin; Kalsi, Kameljit K; Secher, Niels H; González-Alonso, José

    2015-11-01

    Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, whereas the cerebral metabolic rate for O2 (CMRO2 ) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled to fatigue. Two studies were undertaken. In study 1, 10 male cyclists cycled in the heat for ∼2 h with (control) and without fluid replacement (dehydration) while internal and external carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples were assessed with dehydration to evaluate CMRO2 . In study 2, in 8 male subjects, middle cerebral artery blood velocity was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, internal carotid artery flow declined to baseline with progressive dehydration (P < 0.05). However, cerebral metabolism remained stable through enhanced O2 and glucose extraction (P < 0.05). External carotid artery flow increased for 1 h but declined before exhaustion. Fluid ingestion maintained cerebral and extracranial perfusion throughout nonfatiguing exercise. During exhaustive exercise, however, euhydration delayed but did not prevent the decline in cerebral perfusion. In conclusion, during prolonged exercise in the heat, dehydration accelerates the decline in CBF without affecting CMRO2 and also restricts extracranial perfusion. Thus, fatigue is related to a reduction in CBF and extracranial perfusion rather than CMRO2 . PMID:26371170

  8. Influence of body temperature on the development of fatigue during prolonged exercise in the heat.

    PubMed

    González-Alonso, J; Teller, C; Andersen, S L; Jensen, F B; Hyldig, T; Nielsen, B

    1999-03-01

    We investigated whether fatigue during prolonged exercise in uncompensable hot environments occurred at the same critical level of hyperthermia when the initial value and the rate of increase in body temperature are altered. To examine the effect of initial body temperature [esophageal temperature (Tes) = 35.9 +/- 0.2, 37.4 +/- 0. 1, or 38.2 +/- 0.1 (SE) degrees C induced by 30 min of water immersion], seven cyclists (maximal O2 uptake = 5.1 +/- 0.1 l/min) performed three randomly assigned bouts of cycle ergometer exercise (60% maximal O2 uptake) in the heat (40 degrees C) until volitional exhaustion. To determine the influence of rate of heat storage (0.10 vs. 0.05 degrees C/min induced by a water-perfused jacket), four cyclists performed two additional exercise bouts, starting with Tes of 37.0 degrees C. Despite different initial temperatures, all subjects fatigued at an identical level of hyperthermia (Tes = 40. 1-40.2 degrees C, muscle temperature = 40.7-40.9 degrees C, skin temperature = 37.0-37.2 degrees C) and cardiovascular strain (heart rate = 196-198 beats/min, cardiac output = 19.9-20.8 l/min). Time to exhaustion was inversely related to the initial body temperature: 63 +/- 3, 46 +/- 3, and 28 +/- 2 min with initial Tes of approximately 36, 37, and 38 degrees C, respectively (all P < 0.05). Similarly, with different rates of heat storage, all subjects reached exhaustion at similar Tes and muscle temperature (40.1-40.3 and 40. 7-40.9 degrees C, respectively), but with significantly different skin temperature (38.4 +/- 0.4 vs. 35.6 +/- 0.2 degrees C during high vs. low rate of heat storage, respectively, P < 0.05). Time to exhaustion was significantly shorter at the high than at the lower rate of heat storage (31 +/- 4 vs. 56 +/- 11 min, respectively, P < 0.05). Increases in heart rate and reductions in stroke volume paralleled the rise in core temperature (36-40 degrees C), with skin blood flow plateauing at Tes of approximately 38 degrees C. These

  9. Changes in Fatigue, Multiplanar Knee Laxity, and Landing Biomechanics During Intermittent Exercise

    PubMed Central

    Shultz, Sandra J.; Schmitz, Randy J.; Cone, John R.; Henson, Robert A.; Montgomery, Melissa M.; Pye, Michele L.; Tritsch, Amanda J.

    2015-01-01

    Context: Knee laxity increases during exercise. However, no one, to our knowledge, has examined whether these increases contribute to higher-risk landing biomechanics during prolonged, fatiguing exercise. Objectives: To examine associations between changes in fatigue (measured as sprint time [SPTIME]), multiplanar knee laxity (anterior-posterior [APLAX], varus-valgus [VVLAX] knee laxity, and internal-external rotation [IERLAX]) knee laxity and landing biomechanics during prolonged, intermittent exercise. Design: Descriptive laboratory study. Setting: Laboratory and gymnasium. Patients or Other Participants: A total of 30 male (age = 20.3 ± 2.0 years, height = 1.79 ± 0.05 m, mass = 75.2 ± 7.2 kg) and 29 female (age = 20.5 ± 2.3 years, height = 1.67 ± 0.08 m, mass = 61.8 ± 9.0 kg) competitive athletes. Intervention(s): A 90-minute intermittent exercise protocol (IEP) designed to simulate the physiologic and biomechanical demands of a soccer match. Main Outcome Measure(s): We measured SPTIME, APLAX, and landing biomechanics before and after warm-up, every 15 minutes during the IEP, and every 15 minutes for 1 hour after the IEP. We measured VVLAX and IERLAX before and after the warm-up, at 45 and 90 minutes during the IEP, and at 30 minutes after the IEP. We used hierarchical linear modeling to examine associations between exercise-related changes in SPTIME and knee laxity with exercise-related changes in landing biomechanics while controlling for initial (before warm-up) knee laxity. Results: We found that SPTIME had a more global effect on landing biomechanics in women than in men, resulting in a more upright landing and a reduction in landing forces and out-of-plane motions about the knee. As APLAX increased with exercise, women increased their knee internal-rotation motion (P = .02), and men increased their hip-flexion motion and energy-absorption (P = .006) and knee-extensor loads (P = .04). As VVLAX and IERLAX increased, women went through greater knee

  10. Is Sodium Supplementation Necessary to Avoid Dehydration During Prolonged Exercise in the Heat?

    PubMed

    Hoffman, Martin D; Stuempfle, Kristin J

    2016-03-01

    The primary purpose of this work was to gain further insight into the need for sodium supplementation for maintenance of appropriate hydration during prolonged exercise under hot conditions. Participants of a 161-km ultramarathon (ambient temperature reaching 39° C) underwent body weight measurements immediately before, during, and after the race, and completed a postrace questionnaire about supplemental sodium intake and drinking strategies during 4 race segments. The postrace questionnaire was completed by 233 (78.7%) race finishers. Significant direct relationships were found for percentage weight change during the race with intake rate (r = 0.18, p = 0.0058) and total amount (r = 0.24, p = 0.0002) of sodium in supplements. Comparing those using no sodium supplements throughout the race (n = 15) with those using sodium supplements each race segment (n = 138), body weight change across the course showed significant group (p = 0.022), course location (p < 0.0001), and interaction (p = 0.0098) effects. Posttests revealed greater weight loss at 90 km (p = 0.016, -3.2 ± 1.6% vs. -2.2 ± 1.5%, mean ± SD) and the finish (p = 0.014, -3.2 ± 1.5% vs. -1.9 ± 1.9%) for those using no sodium supplements compared with those using sodium supplements each segment. Six runners who used no sodium supplements, drank to thirst, and only drank water or a mixture of mostly water with some electrolyte-containing drink finished with mean weight change of -3.4%. Although the use of supplemental sodium enhanced body weight maintenance, those not using sodium supplements maintained a more appropriate weight than those consistently using sodium supplements. Therefore, we conclude that the supplemental sodium is unnecessary to maintain appropriate hydration during prolonged exercise in the heat. PMID:26907835

  11. Changes of central haemodynamic parameters during mental stress and acute bouts of static and dynamic exercise.

    PubMed

    Lydakis, C; Momen, A; Blaha, C; Gugoff, S; Gray, K; Herr, M; Leuenberger, U A; Sinoway, L I

    2008-05-01

    Chronic dynamic (aerobic) exercise decreases central arterial stiffness, whereas chronic resistance exercise evokes the opposite effect. Nevertheless, there is little information available on the effects of acute bouts of exercise. Also, there is limited data showing an increase of central arterial stiffness during acute mental stress. This study aimed to determine the effect of acute mental and physical (static and dynamic exercise) stress on indices of central arterial stiffness. Fifteen young healthy volunteers were studied. The following paradigms were performed: (1) 2 min of mental arithmetic, (2) short bouts (20 s) of static handgrip at 20 and 70% of maximal voluntary contraction (MVC), (3) fatiguing handgrip at 40% MVC and (4) incremental dynamic knee extensor exercise. Central aortic waveforms were assessed using SphygmoCor software. As compared to baseline, pulse wave transit time decreased significantly for all four interventions indicating that central arterial stiffness increased. During fatiguing handgrip there was a fall in the ratio of peripheral to central pulse pressure from 1.69+/-0.02 at baseline to 1.56+/-0.05 (P<0.05). In the knee extensor protocol a non-significant trend for the opposite effect was noted. The augmentation index increased significantly during the arithmetic, short static and fatiguing handgrip protocols, whereas there was no change in the knee extensor protocol. We conclude that (1) during all types of acute stress tested in this study (including dynamic exercise) estimated central stiffness increased, (2) during static exercise the workload posed on the left ventricle (expressed as change in central pulse pressure) is relatively higher than that posed during dynamic exercise (given the same pulse pressure change in the periphery). PMID:18273040

  12. Cerebral volumetric changes induced by prolonged hypoxic exposure and whole-body exercise.

    PubMed

    Rupp, Thomas; Jubeau, Marc; Lamalle, Laurent; Warnking, Jan M; Millet, Guillaume Y; Wuyam, Bernard; Esteve, François; Levy, Patrick; Krainik, Alexandre; Verges, Samuel

    2014-11-01

    The present study assessed the isolated and synergetic effects of hypoxic exposure and prolonged exercise on cerebral volume and subedema and symptoms of acute mountain sickness (AMS). Twelve healthy males performed three semirandomized blinded 11-hour sessions with (1) an inspiratory oxygen fraction (FiO2) of 12% and 4-hour cycling, (2) FiO2=21% and 4-hour cycling, and (3) FiO2=8.5% to 12% at rest (matching arterial oxygen saturation measured during the first hypoxic session). Volumetric, apparent diffusion coefficient (ADC), and arterial spin labelling 3T magnetic resonance imaging sequences were performed after 30 minutes and 10 hours in each session. Thirty minutes of hypoxia at rest induced a significant increase in white-matter volume (+0.8±1.0% compared with normoxia) that was exacerbated after 10 hours of hypoxia at rest (+1.5±1.1%) or with cycling (+1.6±1.1%). Total brain parenchyma volume increased significantly after 10 hours of hypoxia with cycling only (+1.3±1.1%). Apparent diffusion coefficient was significantly reduced after 10 hours of hypoxia at rest or with cycling. No significant change in cerebral blood flow was observed. These results demonstrate changes in white-matter volume as early as after 30 minutes of hypoxia that worsen after 10 hours, probably due to cytotoxic edema. Exercise accentuates the effect of hypoxia by increasing total brain volume. These changes do not however correlate with AMS symptoms. PMID:25160673

  13. Influence of statins on distinct circulating microRNAs during prolonged aerobic exercise.

    PubMed

    Min, Pil-Ki; Park, Joseph; Isaacs, Stephanie; Taylor, Beth A; Thompson, Paul D; Troyanos, Chris; D'Hemecourt, Pierre; Dyer, Sophia; Chan, Stephen Y; Baggish, Aaron L

    2016-03-15

    Statins exacerbate exercise-induced skeletal muscle injury. Muscle-specific microRNAs (myomiRs) increase in plasma after prolonged exercise, but the patterns of myomiRs release after statin-associated muscle injury have not been examined. We examined the relationships between statin exposure, in vitro and in vivo muscle contraction, and expression of candidate circulating myomiRs. We measured plasma levels of myomiRs, circulating microRNA-1 (c-miR-1), c-miR-133a, c-miR-206, and c-miR-499-5p from 28 statin-using and 28 nonstatin-using runners before (PRE), immediately after (FINISH), and 24 h after they ran a 42-km footrace (the 2011 Boston marathon) (POST-24). To examine these cellular-regulation myomiRs, we used contracting mouse C2C12 myotubes in culture with and without statin exposure to compare intracellular and extracellular expression of these molecules. In marathoners, c-miR-1, c-miR-133a, and c-miR-206 increased at FINISH, returned to baseline at POST-24, and were unaffected by statin use. In contrast, c-miR-499-5p was unchanged at FINISH but increased at POST-24 among statin users compared with PRE and runners who did not take statins. In cultured C2C12 myotubes, extracellular c-miR-1, c-miR-133a, and c-miR-206 were significantly increased by muscle contraction regardless of statin use. In contrast, extracellular miR-499-5p was unaffected by either isolated statin exposure or isolated carbachol exposure but it was increased when muscle contraction was combined with statin exposure. In summary, we found that statin-potentiated muscle injury during exercise is accompanied by augmented extracellular release of miR-499-5p. Thus c-miR-499-5p may serve as a biomarker of statin-potentiated muscle damage. PMID:26472872

  14. Plasma catecholamines and hyperglycaemia influence thermoregulation in man during prolonged exercise in the heat.

    PubMed

    Mora-Rodríguez, R; González-Alonso, J; Below, P R; Coyle, E F

    1996-03-01

    1. We manipulated plasma catecholamines (combined adrenaline and noradrenaline concentrations) to three levels during prolonged exercise to determine their effect on cutaneous and forearm vascular conductance (CVC and FVC), oesophageal temperature (T(oes)) and cardiovascular responses. 2. On three occasions, seven endurance-trained men cycled at 65% VO2, max in the heat (33.1 +/- 0.7 degrees C) for 120-150 min. During the control trial (150 min duration), 0.45% saline was intravenously infused (SI) starting at 30 min, at a rate that replaced a third of the fluid losses. The infusion start time and rate were identical in all three trials. During SI, plasma catecholamine levels increased progressively and were 18.2 +/- 2.7 pmol ml-1 at 150 min. In another trial (120 min duration), adrenaline was infused (AI) at 0.1 microgram kg-1 min-1 and plasma catecholamine levels were elevated 6 pmol ml-1 above SI during the 60-120 min period. In a third trial (150 min duration), an 18% glucose solution was infused (GI) at a rate that maintained plasma glucose levels above 11 mM and plasma catecholamine levels were 5.0-5.5 pmol ml-1 lower (P < 0.05) than SI from 120-150 min. 3. Heat production and sweat rate were not different during the three trials and neither was the decline in stroke volume, cardiac output and mean arterial pressure. 4. Soon after beginning AI, CVC decreased 15%, T(oes) increased by 0.4 +/- 0.1 degree C and heart rate increased by 6 +/- 1 beats min-1; these significant (P < 0.05) differences from SI were maintained throughout the bout. As a result of GI, FVC was 15% higher than SI and T(oes) and heart rate were attenuated by 0.3 +/- 0.1 degree C and 7 +/- 1 beats min-1 at 150 min compared with SI (P < 0.05). 5. In conclusion, large increases in plasma catecholamine levels cause hyperthermia during exercise by vasoconstricting the skin. The mechanisms by which hyperglycaemia (i.e. 11 mM) attenuates hyperthermia are less clear and may be due to others factors

  15. Evaluation of fatigue of respiratory and lower limb muscles during prolonged aerobic exercise.

    PubMed

    Nadiv, Yaara; Vachbroit, Ricki; Gefen, Amit; Elad, David; Zaretsky, Uri; Moran, Dani; Halpern, Pinchas; Ratnovsky, Anat

    2012-05-01

    The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching. PMID:22723112

  16. Phagocytic responses of peritoneal macrophages and neutrophils are different in rats following prolonged exercise

    PubMed Central

    Ferreira, Clílton K O; Prestes, Jonato; Donatto, Felipe F; Verlengia, Rozangela; Navalta, James W; Cavaglieri, Cláudia R

    2010-01-01

    OBJECTIVE: To analyze the effects of exhausting long‐duration physical exercise (swimming) sessions of different durations and intensities on the number and phagocytic capacity of macrophages and neutrophils in sedentary rats. INTRODUCTION: Exercise intensity, duration and frequency are important factors in determining immune response to physical effort. Thus, the effects of exhausting long‐duration exercise are unclear. METHODS: Wistar rats were divided into two groups: an untreated group (macrophage study) and oyster glycogen‐treated rats (neutrophil study). In each group, the animals were subdivided into five groups (10 rats per group): unexercised controls, an unadapted low‐intensity exercise group, an unadapted moderate‐intensity exercise group, a preadapted low‐intensity exercise group and a preadapted moderate‐intensity exercise group. All exercises were performed to exhaustion, and preadaptation consisted of 5, 15, 30 and 45 min sessions. RESULTS: Macrophage study: the number of peritoneal macrophages significantly decreased (9.22 ± 1.78 × 106) after unadapted exercise but increased (21.50 ± 0.63 × 106) after preadapted low‐intensity exercise, with no changes in the moderate‐intensity exercise group. Phagocytic capacity, however, increased by more than 80% in all exercise groups (low/moderate, unadapted/preadapted). Neutrophil study: the number of peritoneal neutrophils significantly decreased after unadapted (29.20 ± 3.34 × 106) and preadapted (50.00 ± 3.53 × 106) low‐intensity exercise but increased after unadapted (127.60 ± 5.14 × 106) and preadapted (221.80 ± 14.85 × 106) moderate exercise. Neutrophil phagocytic capacity decreased by 63% after unadapted moderate exercise but increased by 90% after corresponding preadapted sessions, with no changes in the low‐intensity exercise groups. CONCLUSION: Neutrophils and macrophages of sedentary rats respond differently to exercise‐induced stress. Adaptation sessions reduce

  17. Exercise performance, core temperature, and metabolism after prolonged restricted activity and retraining in dogs

    NASA Technical Reports Server (NTRS)

    Nazar, K.; Greenleaf, J. E.; Pohoska, E.; Turlejska, E.; Kaciuba-Uscilko, H.; Kozlowski, S.

    1992-01-01

    Physiological effects of restricted activity (RA) and subsequent retraining have been studied. Ten male mongrel dogs performed a submaximal exercise endurance test on a treadmill during kennel control, after 8 weeks of cage confinement and after eight weeks of retraining using the same treadmill protocol 1 h/d for 6 d/week. Data obtained show that RA reduces exercise endurance, the effectiveness of exercise thermoregulation, muscle glycogen stores, and the lipolytic response to exercise and to noradrenaline stimulation.

  18. Absence of humoral mediated 5'AMP-activated protein kinase activation in human skeletal muscle and adipose tissue during exercise.

    PubMed

    Kristensen, Jonas Møller; Johnsen, Anders Bo; Birk, Jesper B; Nielsen, Jakob Nis; Jensen, Bente Rona; Hellsten, Ylva; Richter, Erik A; Wojtaszewski, Jørgen F P

    2007-12-15

    5'AMP-activated protein kinase (AMPK) exists as a heterotrimer comprising a catalytic alpha subunit and regulatory beta and gamma subunits. The AMPK system is activated under conditions of cellular stress, indicated by an increase in the AMP/ATP ratio, as observed, e.g. in muscles during contractile activity. AMPK was originally thought to be activated only by local intracellular mechanisms. However, recently it has become apparent that AMPK in mammals is also regulated by humoral substances, e.g. catecholamines. We studied whether humoral factors released during exercise regulate AMPK activity in contracting and resting muscles as well as in abdominal subcutaneous adipose tissue in humans. In resting leg muscle and adipose tissue the AMPK activity was not up-regulated by humoral factors during one-legged knee extensor exercise even when arm cranking exercise, inducing a approximately 20-fold increase in plasma catecholamine level, was added simultaneously. In exercising leg muscle the AMPK activity was increased by one-legged knee extensor exercise eliciting a whole body respiratory load of only 30% .VO(2,peak) but was not further increased by adding arm cranking exercise. In conclusion, during exercise with combined leg kicking and arm cranking, the AMPK activity in human skeletal muscle is restricted to contracting muscle without influence of marked increased catecholamine levels. Also, with this type of exercise the catecholamines or other humoral factors do not seem to be physiological regulators of AMPK in the subcutaneous adipose tissue. PMID:17962330

  19. Prevention of glycogen supercompensation prolongs the increase in muscle GLUT4 after exercise.

    PubMed

    Garcia-Roves, Pablo M; Han, Dong-Ho; Song, Zheng; Jones, Terry E; Hucker, Kathleen A; Holloszy, John O

    2003-10-01

    Exercise induces an increase in GLUT4 in skeletal muscle with a proportional increase in glucose transport capacity. This adaptation results in enhanced glycogen accumulation, i.e., "supercompensation," in response to carbohydrate feeding after glycogen-depleting exercise. The increase in GLUT4 reverses within 40 h after exercise in carbohydrate-fed rats. The purpose of this study was to determine whether prevention of skeletal muscle glycogen supercompensation after exercise results in maintenance of the increases in GLUT4 and the capacity for glycogen supercompensation. Rats were exercised by means of three daily bouts of swimming. GLUT4 mRNA was increased approximately 3-fold and GLUT4 protein was increased approximately 2-fold 18 h in epitrochlearis muscle after exercise. These increases in GLUT4 mRNA and protein reversed completely within 42 h after exercise in rats fed a high-carbohydrate diet. In contrast, the increases in GLUT4 protein, insulin-stimulated glucose transport, and increased capacity for glycogen supercompensation persisted unchanged for 66 h in rats fed a carbohydrate-free diet that prevented glycogen supercompensation after exercise. GLUT4 mRNA was still elevated at 42 h but had returned to baseline by 66 h after exercise in rats fed the carbohydrate-free diet. Glycogen-depleted rats fed carbohydrate 66 h after exercise underwent muscle glycogen supercompensation with concomitant reversal of the increase in GLUT4. These findings provide evidence that prevention of glycogen supercompensation after exercise results in persistence of exercise-induced increases in GLUT4 protein and enhanced capacity for glycogen supercompensation. PMID:12799316

  20. Carbohydrate supplementation and prolonged intermittent high-intensity exercise in adolescents: research findings, ethical issues and suggestions for the future.

    PubMed

    Phillips, Shaun M

    2012-10-01

    knowledge while safeguarding the health and well-being of young participants. It could be deemed unethical to continue study into carbohydrate supplementation while ignoring the potential health concerns and the possibility of generating similar performance enhancements using natural dietary interventions. Therefore, future work should investigate the influence of pre-exercise dietary intake on the prolonged intermittent, high-intensity exercise performance of adolescents. This would enable quantification of whether pre-exercise nutrition can modulate exercise performance and, if so, the optimum dietary composition to achieve this. Research could then combine this knowledge with ingestion of carbohydrate-containing products during exercise to facilitate ethical and healthy nutritional guidelines for enhancing the exercise performance of adolescents. This article addresses the available evidence regarding carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescent team games players. It discusses the potential health concerns associated with the frequent use of carbohydrate-containing products by adolescents and how this affects the research ethics of the field, and considers directions for future work. PMID:22901040

  1. High Intensity Exercise Countermeasures does not Prevent Orthostatic Intolerance Following Prolonged Bed Rest

    NASA Technical Reports Server (NTRS)

    Platts, Steven H.; Stenger, Michael B.; Ploutz-Snyder, Lori L.; Lee, Stuart M. C.

    2014-01-01

    Approximately 20% of Space Shuttle astronauts became presyncopal during operational stand and 80deg head-up tilt tests, and the prevalence of orthostatic intolerance increases after longer missions. Greater than 60% of the US astronauts participating in Mir and early International Space Station missions experienced presyncope during post-flight tilt tests, perhaps related to limitations of the exercise hardware that prevented high intensity exercise training until later ISS missions. The objective of this study was to determine whether an intense resistive and aerobic exercise countermeasure program designed to prevent cardiovascular and musculoskeletal deconditioning during 70 d of bed rest (BR), a space flight analog, would protect against post-BR orthostatic intolerance. METHODS Twenty-six subjects were randomly assigned to one of three groups: non-exercise controls (n=11) or one of two exercise groups (ExA, n=8; ExB, n=7). Both ExA and ExB groups performed the same resistive and aerobic exercise countermeasures during BR, but one exercise group received testosterone supplementation while the other received a placebo during BR in a double-blinded fashion. On 3 d/wk, subjects performed lower body resistive exercise and 30 min of continuous aerobic exercise (=75% max heart rate). On the other 3 d/wk, subjects performed only highintensity, interval-style aerobic exercise. Orthostatic intolerance was assessed using a 15-min 80? head-up tilt test performed 2 d (BR-2) before and on the last day of BR (BR70). Plasma volume was measured using carbon monoxide rebreathing on BR-3 and before rising on the first recovery day (BR+0). The code for the exercise groups has not been broken, and results are reported here without group identification. RESULTS Only one subject became presyncopal during tilt testing on BR-2, but 7 of 11 (63%) controls, 3 of 8 (38%) ExA, and 4 of 7 (57%) ExB subjects were presyncopal on BR70. Survival analysis of post-BR tilt tests revealed no

  2. Benefits of exercise training in Spanish prison inmates.

    PubMed

    Pérez-Moreno, F; Cámara-Sánchez, M; Tremblay, J F; Riera-Rubio, V J; Gil-Paisán, L; Lucia, A

    2007-12-01

    Prison populations are growing in Western countries. Imprisoned people usually have a poor health status and an increased risk to suffer chronic debilitating conditions as coinfection with the HIV and hepatitis C virus (HCV) and/or opioid dependency. We studied the effects of a 4-month concurrent cardiorespiratory and resistance training program on the cardiorespiratory fitness, lower and upper body dynamic strength endurance (6-RM test for bench press and knee-extensor exercise, respectively), muscle mass and quality of life (QOL) of adult prison inmates who are HIV/HVC co-infected and enrolled in a methadone maintenance program (n = 9; mean [SD] age: 37 [3] yrs). We also evaluated a control group (n = 10; 37 [2] yrs). A significant combined effect of group and time was found for peak completed workload (W) (p < 0.01), peak heart rate (HR (peak)) (p < 0.05) and rate of HR decrease at 1-min postexercise compared to HR (peak) (p < 0.05), respectively, in a gradual cycle ergometer test. A significant combined effect of group and time was also found for both bench press and knee-extensor 6-RM tests, respectively (p < 0.05). Supervised exercise training can improve the overall physical fitness of incarcerated people. Our results suggest that this type of intervention could be applied in prisons of Western societies. PMID:17549659

  3. Muscle mitochondrial density after exhaustive exercise in dogs - Prolonged restricted activity and retraining

    NASA Technical Reports Server (NTRS)

    Nazar, K.; Greenleaf, J. E.; Philpott, D.; Pohoska, E.; Olszewska, K.; Kaciuba-Uscilko, H.

    1993-01-01

    The effect of exhaustive treadmill exercise on mitochondrial density (MD) and ultrastructural changes in quadriceps femoris muscle was studied in 7 normal, healthy, male mongrel dogs before and after restricted activity (RA) and following a subsequent 2-month exercise retraining period. Mean time to exhaustion in the 2-month group decreased from 177 +/- 11 min before to 90 +/- 16 min after RA; retraining increased tolerance to 219 +/- 36 min above the pre-RA and 143 percent above the post-RA time. Post-RA exhaustion time in the 5-months group was 25 and 45 min. Muscle samples taken after RA showed abnormalities indicative of degeneration, which were reversed by retraining. Resting MD decreased from a control level of 27.8 percent to 14.7 percent and 16.3 percent, and was restored to 27.1 percent after retraining. Exhaustive exercise caused an increase in MD under control conditions and after RA, but not following retraining. Disruption of mitochondria after exercise was evident after 5-month confinement. Factors causing mitochondrial changes and eventually their disruption during exercise after restricted activity are not related as much to the state of fatigue as to the pre-exercise quality of the muscle modified by disease or training.

  4. What are the Physiological Mechanisms for Post-Exercise Cold Water Immersion in the Recovery from Prolonged Endurance and Intermittent Exercise?

    PubMed

    Ihsan, Mohammed; Watson, Greig; Abbiss, Chris R

    2016-08-01

    training performances. The efficacy of CWI for attenuating the secondary effects of EIMD seems dependent on the mode of exercise utilised. For instance, CWI application seems to demonstrate limited recovery benefits when EIMD was induced by single-joint eccentrically biased contractions. In contrast, CWI seems more effective in ameliorating effects of EIMD induced by whole body prolonged endurance/intermittent based exercise modalities. PMID:26888646

  5. The influence of wearing compression stockings on performance indicators and physiological responses following a prolonged trail running exercise.

    PubMed

    Vercruyssen, Fabrice; Easthope, Christopher; Bernard, Thierry; Hausswirth, Christophe; Bieuzen, Francois; Gruet, Mathieu; Brisswalter, Jeanick

    2014-01-01

    The objective of this study was to investigate the effects of wearing compression socks (CS) on performance indicators and physiological responses during prolonged trail running. Eleven trained runners completed a 15.6 km trail run at a competition intensity whilst wearing or not wearing CS. Counter movement jump, maximal voluntary contraction and the oxygenation profile of vastus lateralis muscle using near-infrared spectroscopy (NIRS) method were measured before and following exercise. Run time, heart rate (HR), blood lactate concentration and ratings of perceived exertion were evaluated during the CS and non-CS sessions. No significant difference in any dependent variables was observed during the run sessions. Run times were 5681.1 ± 503.5 and 5696.7 ± 530.7 s for the non-CS and CS conditions, respectively. The relative intensity during CS and non-CS runs corresponded to a range of 90.5-91.5% HRmax. Although NIRS measurements such as muscle oxygen uptake and muscle blood flow significantly increased following exercise (+57.7% and + 42.6%,+59.2% and + 32.4%, respectively for the CS and non-CS sessions, P<0.05), there was no difference between the run conditions. The findings suggest that competitive runners do not gain any practical or physiological benefits from wearing CS during prolonged off-road running. PMID:24533521

  6. Sex differences in the response to resistance exercise training in older people.

    PubMed

    Da Boit, Mariasole; Sibson, Rachael; Meakin, Judith R; Aspden, Richard M; Thies, Frank; Mangoni, Arduino A; Gray, Stuart Robert

    2016-06-01

    Resistance exercise training is known to be effective in increasing muscle mass in older people. Acute measurement of protein metabolism data has indicated that the magnitude of response may differ between sexes. We compared adaptive responses in muscle mass and function to 18 weeks resistance exercise training in a cohort of older (>65 years) men and women. Resistance exercise training improved knee extensor maximal torque, 4 m walk time, time to complete five chair rises, muscle anatomical cross-sectional area (ACSA) and muscle quality with no effect on muscle fat/water ratio or plasma glucose, insulin, triacylglycerol, IL-6, and TNF-α Differences between sexes were observed for knee extensor maximal torque and muscle quality with greater increases observed in men versus women (P < 0.05). Maximal torque increased by 15.8 ± 10.6% in women and 41.7 ± 25.5% in men, whereas muscle quality increased by 8.8 ± 17.5% in women and by 33.7 ± 25.6% in men. In conclusion, this study has demonstrated a difference in the magnitude of adaptation, of some of the outcome measures employed, in response to 18 weeks of resistance exercise training between men and women. The mechanisms underlying this observation remain to be established. PMID:27354538

  7. Reduction in Cerebral Oxygenation After Prolonged Exercise in Hypoxia is Related to Changes in Blood Pressure.

    PubMed

    Horiuchi, Masahiro; Dobashi, Shohei; Kiuchi, Masataka; Endo, Junko; Koyama, Katsuhiro; Subudhi, Andrew W

    2016-01-01

    We investigated the relation between blood pressure and cerebral oxygenation (COX) immediately after exercise in ten healthy males. Subjects completed an exercise and recovery protocol while breathing either 21% (normoxia) or 14.1% (hypoxia) O2 in a randomized order. Each exercise session included four sets of cycling (30 min/set, 15 min rest) at 50% of altitude-adjusted peak oxygen uptake, followed by 60 min of recovery. After exercise, mean arterial pressure (MAP; 87±1 vs. 84±1 mmHg, average values across the recovery period) and COX (68±1% vs. 58±1%) were lower in hypoxia compared to normoxia (P<0.001). Changes in MAP and COX were correlated during the recovery period in hypoxia (r=0.568, P<0.001) but not during normoxia (r=0.028, not significant). These results demonstrate that reductions in blood pressure following exercise in hypoxia are (1) more pronounced than in normoxia, and (2) associated with reductions in COX. Together, these results suggest an impairment in cerebral autoregulation as COX followed changes in MAP more passively in hypoxia than in normoxia. These findings could help explain the increased risk for postexercise syncope at high altitude. PMID:26782200

  8. Statins Attenuate the Increase in P-Selectin Produced by Prolonged Exercise

    PubMed Central

    Zaleski, Amanda; Capizzi, Jeffrey; Ballard, Kevin D.; Troyanos, Christopher; Baggish, Aaron; D'Hemecourt, Pierre; Thompson, Paul D.; Parker, Beth

    2013-01-01

    Strenuous endurance exercise increases inflammatory markers and acutely increases cardiovascular risk; however, statins may mitigate this response. We measured serum levels of p-selectin in 37 runners treated with statins and in 43 nonstatin treated controls running the 2011 Boston Marathon. Venous blood samples were obtained the day before (PRE) as well as within 1 hour after (FINISH) and 24 hours after (POST) the race. The increase in p-selectin immediately after exercise was lower in statin users (PRE to FINISH: 20.5 ± 19.4 ng/mL) than controls (PRE to FINISH: 30.9 ± 27.1 ng/mL; P < 0.001). The increase in p-selectin 24 hours after exercise was also lower in statin users (PRE to POST: 21.5 ± 26.6 ng/mL) than controls (PRE to POST: 29.3 ± 31.9 ng/mL; P < 0.001). Furthermore, LDL-C was positively correlated with p-selectin at FINISH and POST (P < 0.01 and P < 0.05, resp.), irrespective of drug treatment, suggesting that lower levels of LDL-C are associated with a reduced inflammatory response to exercise. We conclude that statins blunt the exercise-induced increase in p-selectin following a marathon and that the inflammatory response to a marathon varies directly with LDL-C levels. PMID:26464882

  9. Erythropoietin enhances whole body lipid oxidation during prolonged exercise in humans.

    PubMed

    Caillaud, Corinne; Connes, Philippe; Ben Saad, Helmi; Mercier, Jacques

    2015-03-01

    Animal studies have suggested that erythropoietin, besides its well-known hematopoietic effects, can modulate metabolism and prevent fat accumulation. We investigated the effects of repeated injections of recombinant human erythropoietin (EPO) on the balance of substrate oxidation during aerobic exercise in humans. Twelve healthy aerobically trained males received subcutaneously either moderate dose of EPO (50 U/kg, EPO) or saline injections (NaCl 0.9 %, control) three times a week for 4 weeks. Body weight, % fat, maximal aerobic capacity, and substrate utilization during exercise were assessed before and after treatment, while hemoglobin and hematocrit were monitored regularly during the treatment. Carbohydrate and fat oxidation were evaluated via indirect calorimetry, during a submaximal exercise performed at 75 % of the participants' maximal aerobic capacity (V̇(O2max)) for 60 min. Results showed that 4 weeks of EPO treatment significantly enhanced fat oxidation (+56 % in EPO versus -9 % in control) during exercise, independent of its effects on hematological parameters or V̇(O2max). This study shows that EPO can modulate substrate utilization during exercise, leading to enhanced fat utilization and lower use of carbohydrates. This opens new research directions exploring whether systemic EPO levels, in physiological conditions, participate to the modulation of fat oxidation. PMID:25567744

  10. Statins Attenuate the Increase in P-Selectin Produced by Prolonged Exercise.

    PubMed

    Zaleski, Amanda; Capizzi, Jeffrey; Ballard, Kevin D; Troyanos, Christopher; Baggish, Aaron; D'Hemecourt, Pierre; Thompson, Paul D; Parker, Beth

    2013-01-01

    Strenuous endurance exercise increases inflammatory markers and acutely increases cardiovascular risk; however, statins may mitigate this response. We measured serum levels of p-selectin in 37 runners treated with statins and in 43 nonstatin treated controls running the 2011 Boston Marathon. Venous blood samples were obtained the day before (PRE) as well as within 1 hour after (FINISH) and 24 hours after (POST) the race. The increase in p-selectin immediately after exercise was lower in statin users (PRE to FINISH: 20.5 ± 19.4 ng/mL) than controls (PRE to FINISH: 30.9 ± 27.1 ng/mL; P < 0.001). The increase in p-selectin 24 hours after exercise was also lower in statin users (PRE to POST: 21.5 ± 26.6 ng/mL) than controls (PRE to POST: 29.3 ± 31.9 ng/mL; P < 0.001). Furthermore, LDL-C was positively correlated with p-selectin at FINISH and POST (P < 0.01 and P < 0.05, resp.), irrespective of drug treatment, suggesting that lower levels of LDL-C are associated with a reduced inflammatory response to exercise. We conclude that statins blunt the exercise-induced increase in p-selectin following a marathon and that the inflammatory response to a marathon varies directly with LDL-C levels. PMID:26464882

  11. The effects of compression garments on performance of prolonged manual-labour exercise and recovery.

    PubMed

    Chan, Val; Duffield, Rob; Watsford, Mark

    2016-02-01

    This study investigated the effects of wearing compression garments during and 24 h following a 4-h exercise protocol simulating manual-labour tasks. Ten physically trained male participants, familiar with labouring activities, undertook 4 h of work tasks characteristic of industrial workplaces. Participants completed 2 testing sessions, separated by at least 1 week. In the experimental condition, participants wore a full-length compression top and compression shorts during the exercise protocol and overnight recovery, with normal work clothes worn in the control condition. Testing for serum creatine kinase and C-reactive protein, handgrip strength, knee flexion and extension torque, muscle stiffness, perceived muscle soreness and fatigue as well as heart rate and rating of perceived exertion (RPE) responses to 4-min cycling were performed before, following, and 24 h after exercise. Creatine kinase, muscle soreness, and rating of perceived fatigue increased following the exercise protocol (p < 0.05) as did RPE to a standardised cycling warm-up bout. Conversely, no postexercise changes were observed in C-reactive protein, handgrip strength, peak knee flexion torque, or stiffness measures (p > 0.05). Knee extension torque was significantly higher in the control condition at 24 h postexercise (3.1% ± 5.4% change; compression: 2.2% ± 11.1% change), although no other variables were different between conditions at any time. However, compression demonstrated a moderate-large effect (d > 0.60) to reduce perceived muscle soreness, fatigue, and RPE from standardised warm-up at 24 h postexercise. The current findings suggest that compression may assist in perceptual recovery from manual-labour exercise with implications for the ability to perform subsequent work bouts. PMID:26778138

  12. Prolonged Exercise in Type 1 Diabetes: Performance of a Customizable Algorithm to Estimate the Carbohydrate Supplements to Minimize Glycemic Imbalances

    PubMed Central

    Francescato, Maria Pia; Stel, Giuliana; Stenner, Elisabetta; Geat, Mario

    2015-01-01

    Physical activity in patients with type 1 diabetes (T1DM) is hindered because of the high risk of glycemic imbalances. A recently proposed algorithm (named Ecres) estimates well enough the supplemental carbohydrates for exercises lasting one hour, but its performance for prolonged exercise requires validation. Nine T1DM patients (5M/4F; 35–65 years; HbA1c 54±13 mmol·mol-1) performed, under free-life conditions, a 3-h walk at 30% heart rate reserve while insulin concentrations, whole-body carbohydrate oxidation rates (determined by indirect calorimetry) and supplemental carbohydrates (93% sucrose), together with glycemia, were measured every 30 min. Data were subsequently compared with the corresponding values estimated by the algorithm. No significant difference was found between the estimated insulin concentrations and the laboratory-measured values (p = NS). Carbohydrates oxidation rate decreased significantly with time (from 0.84±0.31 to 0.53±0.24 g·min-1, respectively; p<0.001), being estimated well enough by the algorithm (p = NS). Estimated carbohydrates requirements were practically equal to the corresponding measured values (p = NS), the difference between the two quantities amounting to –1.0±6.1 g, independent of the elapsed exercise time (time effect, p = NS). Results confirm that Ecres provides a satisfactory estimate of the carbohydrates required to avoid glycemic imbalances during moderate intensity aerobic physical activity, opening the prospect of an intriguing method that could liberate patients from the fear of exercise-induced hypoglycemia. PMID:25918842

  13. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis

    PubMed Central

    Areta, José L; Burke, Louise M; Ross, Megan L; Camera, Donny M; West, Daniel W D; Broad, Elizabeth M; Jeacocke, Nikki A; Moore, Daniel R; Stellingwerff, Trent; Phillips, Stuart M; Hawley, John A; Coffey, Vernon G

    2013-01-01

    Quantity and timing of protein ingestion are major factors regulating myofibrillar protein synthesis (MPS). However, the effect of specific ingestion patterns on MPS throughout a 12 h period is unknown. We determined how different distributions of protein feeding during 12 h recovery after resistance exercise affects anabolic responses in skeletal muscle. Twenty-four healthy trained males were assigned to three groups (n= 8/group) and undertook a bout of resistance exercise followed by ingestion of 80 g of whey protein throughout 12 h recovery in one of the following protocols: 8 × 10 g every 1.5 h (PULSE); 4 × 20 g every 3 h (intermediate: INT); or 2 × 40 g every 6 h (BOLUS). Muscle biopsies were obtained at rest and after 1, 4, 6, 7 and 12 h post exercise. Resting and post-exercise MPS (l-[ring-13C6] phenylalanine), and muscle mRNA abundance and cell signalling were assessed. All ingestion protocols increased MPS above rest throughout 1–12 h recovery (88–148%, P < 0.02), but INT elicited greater MPS than PULSE and BOLUS (31–48%, P < 0.02). In general signalling showed a BOLUS>INT>PULSE hierarchy in magnitude of phosphorylation. MuRF-1 and SLC38A2 mRNA were differentially expressed with BOLUS. In conclusion, 20 g of whey protein consumed every 3 h was superior to either PULSE or BOLUS feeding patterns for stimulating MPS throughout the day. This study provides novel information on the effect of modulating the distribution of protein intake on anabolic responses in skeletal muscle and has the potential to maximize outcomes of resistance training for attaining peak muscle mass. PMID:23459753

  14. The effect of hip abductor exercise on muscle strength and trunk stability after an injury of the lower extremities

    PubMed Central

    Kak, Hwang-Bo; Park, Sun-Ja; Park, Byun-Joon

    2016-01-01

    [Purpose] The gluteus medius, a hip abductor, controls femoral movement and stabilizes the pelvis during lower extremity mobilization. [Subjects] This study enrolled 24 subjects into control and experimental groups. [Methods] This randomized controlled study included patients who underwent arthroscopy after meniscus injury and started a rehabilitative exercise program 8 weeks after surgery. Subjects were divided into the experimental gluteus medius resistance exercise group (n=12) and the control group (n=12). The study investigated muscle strength and balance of the flexors, extensors, and abductors of the knee for 8 weeks. [Results] Strengths of knee extensors in patients who underwent rehabilitative exercise for 8 weeks were measured. Strength of the knee extensors of the experimental and control groups increased by 40% and 31%, respectively; strength of the hip flexors of the experimental and control groups increased by 31% and 18%, respectively. Strength of the hip joint muscles showed a 40% increase in the experimental group and a 14% increase in the control group. However, there was a significant difference (18%) in muscle strength of the hip abductors between the groups. Measurements of trunk lateral flexion showed a difference within a group, but no intergroup difference was found. [Conclusion] This study investigated the effect of hip abductor exercise on muscular strength and trunk stability in patients with a meniscus injury. PMID:27134387

  15. Changes in Drop-Jump Landing Biomechanics During Prolonged Intermittent Exercise

    PubMed Central

    Schmitz, Randy J.; Cone, John C.; Tritsch, Amanda J.; Pye, Michele L.; Montgomery, Melissa M.; Henson, Robert A.; Shultz, Sandra J.

    2014-01-01

    Background: As injury rates rise in the later stages of sporting activities, a better understanding of lower extremity biomechanics in the later phases of gamelike situations may improve training and injury prevention programs. Hypothesis: Lower extremity biomechanics of a drop-jump task (extracted from a principal components analysis) would reveal factors associated with risk of anterior cruciate ligament injury during a 90-minute individualized intermittent exercise protocol (IEP) and for 1 hour following the IEP. Study Design: Controlled laboratory study. Level of Evidence: Level 4. Methods: Fifty-nine athletes (29 women, 30 men) completed 3 sessions. The first session assessed fitness for an IEP designed to simulate the demands of a soccer match. An experimental session assessed drop-jump biomechanics, after a dynamic warm-up, every 15 minutes during the 90-minute IEP, and for 1 hour following the IEP. A control session with no exercise assessed drop-jump performance at the same intervals. Results: Two biomechanical factors early in the first half (hip flexion at initial contact and hip loading; ankle loading and knee shear force) decreased at the end of the IEP and into the 60-minute recovery period, while a third factor (knee loading) decreased only during the recovery period (P ≤ 0.05). Conclusion: The individualized sport-specific IEP may have more subtle effects on landing biomechanics when compared with short-term, exhaustive fatigue protocols. Clinical Relevance: Potentially injurious landing biomechanics may not occur until the later stages of soccer activity. PMID:24587862

  16. The Prolonged Intake of L-Arginine-L-Aspartate Reduces Blood Lactate Accumulation and Oxygen Consumption During Submaximal Exercise

    PubMed Central

    Burtscher, Martin; Brunner, Fritz; Faulhaber, Martin; Hotter, Barbara; Likar, Rudolf

    2005-01-01

    L-arginine-L-aspartate is widely used by athletes for its potentially ergogenic properties. However, only little information on its real efficacy is available from controlled studies. Therefore, we evaluated the effects of prolonged supplementation with L-arginine-L-aspartate on metabolic and cardiorespiratory responses to submaximal exercise in healthy athletes by a double blind placebo-controlled trial. Sixteen healthy male volunteers (22 ± 3 years) performed incremental cycle spiroergometry up to 150 watts before and after intake of L-arginine-L-aspartate (3 grams per day) or placebo for a period of 3 weeks. After intake of L-arginine-L-aspartate, blood lactate at 150 watts dropped from 2.8 ± 0.8 to 2.0 ± 0.9 mmol·l-1 (p < 0.001) and total oxygen consumption during the 3-min period at 150 watts from 6.32 ± 0.51 to 5.95 ± 0.40 l (p = 0.04) compared to placebo (2.7 ± 1.1 to 2.7 ± 1.4 mmol·l-1; p = 0.9 and 6.07 ± 0.51 to 5.91 ± 0.50 l; p = 0.3). Additionally, L-arginine-L-aspartate supplementation effected an increased fat utilisation at 50 watts. L-arginine and L-aspartate seem to have induced synergistic metabolic effects. L-arginine might have reduced lactic acid production by the inhibition of glycolysis and L-aspartate may have favoured fatty acid oxidation. Besides, the results indicate improved work efficiency after L-arginine-L-aspartate intake. The resulting increases of submaximal work capacity and exercise tolerance may have important implications for athletes as well as patients. Key Points Amino acids are among the most common nutritional supplements taken by athletes. They are involved in numerous metabolic pathways that affect exercise metabolism. Three weeks of L-arginine-L-aspartate supplementation resulted in lower blood lactate concentrations and oxygen consumption, diminished glucose and enhanced fat oxidation, and reduced heart rate and ventilation during submaximal cycle exercise. This implies increased submaximal work capacity and

  17. Effect of inspiratory resistance to prolonged exercise in a hot environment wearing protective clothing

    NASA Astrophysics Data System (ADS)

    Jetté, Maurice; Quenneville, Josée; Thoden, James; Livingstone, Sydney

    1992-09-01

    The effects of inspiratory resistance on prolonged work in a hot environment wearing a nuclear, bacteriological and chemical warfare (NBCW) mask and overgarment were assessed in 10 males. Subjects walked on a treadmill at 5 km/hr, 2% gradient, until their core temperature reached 39° C or for a duration of 90 min. Rectal temperature, heart rate, ventilation, oxygen consumption and rate of perceived breathing were measured. There were no differences between break-point time without the canister (62.2 ± 21 min) and with the canister (58.9 ± 17 min). Regression analysis indicated that the mean core temperature increased by 0.02° C for every minute of work performed and heart rate by 6 beats/min for every increase of 0.2° C in core temperature. Reduction in heat transfer brought about by wearing the protective overgarment and mask with or without the canister will significantly increase core temperature and limit the performance of moderate work to approximately 1 h in a moderately fit individual.

  18. Effectiveness of therapeutic physical exercise in the treatment of patellofemoral pain syndrome: a systematic review

    PubMed Central

    Alba-Martín, Pablo; Gallego-Izquierdo, T; Plaza-Manzano, Gustavo; Romero-Franco, Natalia; Núñez-Nagy, Susana; Pecos-Martín, Daniel

    2015-01-01

    [Purpose] The aim of this study was to analyze the effectiveness of conservative treatment of patellofemoral pain syndrome with physical exercise. [Subjects and Methods] A computer-based review conducted of four databases (PubMed, the Cochrane Library, PEDro, and the University Library) was completed based on the inclusion criteria of patellofemoral pain syndrome patients treated with physical exercise methods and examination with self-reported pain and/or functional questionnaires. [Results] The findings of ten clinical trials of moderate to high quality were evaluated to determine the effectiveness of physical exercise as conservative management for patellofemoral pain syndrome. [Conclusion] The intervention programs that were most effective in relieving pain and improving function in patellofemoral pain syndrome included proprioceptive neuromuscular facilitation stretching and strengthening exercises for the hip external rotator and abductor muscles and knee extensor muscles. PMID:26311988

  19. Influence of Hydration Status on Changes in Plasma Cortisol, Leukocytes, and Antigen-Stimulated Cytokine Production by Whole Blood Culture following Prolonged Exercise.

    PubMed

    Svendsen, Ida S; Killer, Sophie C; Gleeson, Michael

    2014-01-01

    Elevated antigen-stimulated anti-inflammatory cytokine production appears to be a risk factor for upper respiratory tract illness in athletes. The purpose of this study was to determine the effects of prolonged exercise and hydration on antigen-stimulated cytokine production. Twelve healthy males cycled for 120 min at 60% [Formula: see text] on two occasions, either euhydrated or moderately hypohydrated (induced by fluid restriction for 24 h). Blood samples were collected before and after exercise and following 2 h recovery for determination of cell counts, plasma cortisol, and in vitro antigen-stimulated cytokine production by whole blood culture. Fluid restriction resulted in mean body mass loss of 1.3% and 3.9% before and after exercise, respectively. Exercise elicited a significant leukocytosis and elevated plasma cortisol, with no differences between trials. IL-6 production was significantly reduced 2 h postexercise (P < 0.05), while IL-10 production was elevated postexercise (P < 0.05). IFN- γ and IL-2 production tended to decrease postexercise. No significant effect of hydration status was observed for the measured variables. Prolonged exercise appears to result in augmented anti-inflammatory cytokine release in response to antigen challenge, possibly coupled with acute suppression of proinflammatory cytokine production, corresponding with studies using mitogen or endotoxin as stimulant. Moderate hypohydration does not appear to influence these changes. PMID:24967270

  20. The influence of ice slushy on voluntary contraction force following exercise-induced hyperthermia.

    PubMed

    Burdon, Catriona A; Easthope, Christopher S; Johnson, Nathan A; Chapman, Phillip G; O'Connor, Helen

    2014-07-01

    This study aimed to investigate the effect of exercise-induced hyperthermia on central fatigue and force decline in exercised and nonexercised muscles and whether ingestion of ice slushy (ICE) ameliorates fatigue. Eight participants (5 males, 3 females) completed 45 s maximal voluntary isometric contractions (MVIC) with elbow flexors and knee extensors at baseline and following an exercise-induced rectal temperature (Trec) of 39.3 ± 0.2 °C. Percutaneous electrical muscle stimulation was superimposed at 15, 30 and 44 s during MVICs to assess muscle activation. To increase Trec to 39.3 °C, participants cycled at 60% maximum power output for 42 ± 11 min in 40 °C and 50% relative humidity. Immediately prior to each MVIC, participants consumed 50 g of ICE (-1 °C) or thermoneutral drink (38 °C, CON) made from 7.4% carbohydrate beverage. Participants consumed water (19 °C) during exercise to prevent hypohydration. Voluntary muscle force production and activation in both muscle groups were unchanged at Trec 39.3 °C with ICE (knee extensors: 209 ± 152 N) versus CON (knee extensors: 255 ± 157 N, p = 0.19). At Trec 39.3 °C, quadriceps mean force (232 ± 151 N) decreased versus baseline (302 ± 180 N, p < 0.001) and mean voluntary activation was also decreased (by 15% ± 11%, p < 0.001). Elbow flexor mean force decreased from 179 ± 67 N to 148 ± 65 N when Trec was increased to 39.3 °C (p < 0.001) but mean voluntary activation was not reduced at 39.3 °C (5% ± 25%, p = 0.79). After exercise-induced hyperthermia, ICE had no effect on voluntary activation or force production; however, both were reduced from baseline in the exercised muscle group. Peripheral fatigue was greater than the central component and limited the ability of an intervention designed to alter central fatigue. PMID:24971678

  1. Ingestion of glucose or sucrose prevents liver but not muscle glycogen depletion during prolonged endurance-type exercise in trained cyclists.

    PubMed

    Gonzalez, Javier T; Fuchs, Cas J; Smith, Fiona E; Thelwall, Pete E; Taylor, Roy; Stevenson, Emma J; Trenell, Michael I; Cermak, Naomi M; van Loon, Luc J C

    2015-12-15

    The purpose of this study was to define the effect of glucose ingestion compared with sucrose ingestion on liver and muscle glycogen depletion during prolonged endurance-type exercise. Fourteen cyclists completed two 3-h bouts of cycling at 50% of peak power output while ingesting either glucose or sucrose at a rate of 1.7 g/min (102 g/h). Four cyclists performed an additional third test for reference in which only water was consumed. We employed (13)C magnetic resonance spectroscopy to determine liver and muscle glycogen concentrations before and after exercise. Expired breath was sampled during exercise to estimate whole body substrate use. After glucose and sucrose ingestion, liver glycogen levels did not show a significant decline after exercise (from 325 ± 168 to 345 ± 205 and 321 ± 177 to 348 ± 170 mmol/l, respectively; P > 0.05), with no differences between treatments. Muscle glycogen concentrations declined (from 101 ± 49 to 60 ± 34 and 114 ± 48 to 67 ± 34 mmol/l, respectively; P < 0.05), with no differences between treatments. Whole body carbohydrate utilization was greater with sucrose (2.03 ± 0.43 g/min) vs. glucose (1.66 ± 0.36 g/min; P < 0.05) ingestion. Both liver (from 454 ± 33 to 283 ± 82 mmol/l; P < 0.05) and muscle (from 111 ± 46 to 67 ± 31 mmol/l; P < 0.01) glycogen concentrations declined during exercise when only water was ingested. Both glucose and sucrose ingestion prevent liver glycogen depletion during prolonged endurance-type exercise. Sucrose ingestion does not preserve liver glycogen concentrations more than glucose ingestion. However, sucrose ingestion does increase whole body carbohydrate utilization compared with glucose ingestion. This trial was registered at https://www.clinicaltrials.gov as NCT02110836. PMID:26487008

  2. WISE 2005: LBNP Exercise and Flywheel Resistive Exercise as an Effective Countermeasure Combination

    NASA Technical Reports Server (NTRS)

    Meuche, S.; Schneider, S. M.; Lee, S. M. C.; Macias, B. R.; Smith, S. M.; Watenpaugh, D. E.; Hargens, A. R.

    2006-01-01

    Long-term exposure to microgravity can cause a severe musculoskeletal loss and cardiovascular deconditioning in astronauts. In this report, the effectiveness of combined supine treadmill exercise in a lower body negative pressure chamber (LBNPex) and flywheel resistive exercise (Rex) countermeasures was determined to prevent bone loss, reduced aerobic upright exercise capacity and reduced muscle strength. We hypothesized that exercise subjects (EX) would show less decrease in bone mineral density (BMD), peak oxygen consumption (VO2pk) and knee extensor strength (KES) than control subjects (CON). Sixteen healthy female subjects (34 plus or minus 4yrs, 164 plus or minus 6.5cm, 58 plus or minus 5kg; mean plus or minus SD) participated in a 60-d 6 degree head-down tilt bed rest (BR) study after providing written informed consent. Subjects were assigned to one of two groups: a non- exercising CON group or an EX group performing LBNPex 2-4 d/wk and Rex every 3rd-d. VO2pk was measured with a maximal, graded, upright treadmill test performed pre-BR and on 3-d after BR. BMD was assessed pre-BR and 3-d after BR by dual energy x-ray absorptiometry total body DEXA scan (DEXA; HOLOGIC QDR 4500 Elite ). A Cybex dynamometer was employed to measure the isokinetic KES before and 5-d after BR. Two-way repeated measures ANOVA were performed with time as the repeated factor. Statistical significance was set at p less than 0.05. CON experienced a significant decrease in BMD in the trochanter (PRE: 0.670 0.045; POST: 0.646 0.352 g(raised dot) per square centimeter) and in the whole hip (PRE: 0.894 0.059; POST: 0.858 0.057 g(raised dot) per square centimeter). BMD also decreased significantly in EX in the trochanter (PRE: 0.753 plus or minus 0.0617; POST: 0.741 plus or minus 0.061 g(raised dot) per square centimeter) and whole hip (PRE: 0.954 plus or minus 0.067; POST: 0.935 plus or minus 0.069 g(raised dot) per square centimeter). BMD losses were significantly less in EX than in CON

  3. Supine Treadmill Exercise in Lower Body Negative Pressure Combined with Resistive Exercise Counteracts Bone Loss, Reduced Aerobic Upright Exercise Capacity and Reduced Muscle Strength

    NASA Technical Reports Server (NTRS)

    Meuche, Sabine; Schneider, S. M.; Lee, S. M. C.; Macias, B. R.; Smith, S. M.; Watenpaugh, D. E.; Hargens, A. R.

    2006-01-01

    Long-term exposure to weightlessness leads to cardiovascular and musculoskeletal deconditioning. In this report, the effectiveness of combined supine treadmill exercise in a lower body negative pressure chamber (LBNPex) and flywheel resistive exercise (Rex) countermeasures was determined to prevent bone loss, reduced aerobic upright exercise capacity and reduced muscle strength. We hypothesized that exercise subjects would show less decrease in bone mineral density (BMD), peak oxygen consumption (VO2pk) and knee extensor strength (KES) than control subjects. Sixteen healthy female subjects participated in a 60-d 6(sup 0) head-down tilt bed rest (BR) study after providing written informed consent. Subjects were assigned to one of two groups: a non-exercising control group CON or an exercise group EX performing LBNPex 2-4 d/wk and Rex every 3rd-d. VO2pk was measured with a maximal, graded, upright treadmill test performed pre-BR and on 3-d after BR. BMD was assessed before and 3-d after BR. Isokinetic KES was measured before and 5-d after BR. Two-way repeated measures ANOVA were performed. Statistical significance was set at p less than 0.05. CON experienced a significant decrease in BMD in the trochanter (PRE: 0.670 plus or minus 0.045; POST: 0.646 plus or minus 0.352 g (raised dot) per square centimeter) and in the whole hip (PRE=0.894 plus or minus 0.059; POST: 0.858 plus or minus 0.057 g (raised dot) per square centimeter). BMD also decreased significantly in EX in the trochanter (PRE: 0.753 plus or minus 0.0617; POST: 0.741 plus or minus 0.061 g (raised dot) per square centimeter) and whole hip (PRE: 0.954 plus or minus 0.067; POST: 0.935 plus or minus 0.069 g (raised dot) per square centimeter). BMD losses were significantly less in EX than in CON subjects. VO2pk was significantly decreased in the CON after BR (PRE: 38.0 plus or minus 4.8; POST: 29.9 plus or minus 4.2 ml (raised dot) per kilogram per minute), but not in the EX (PRE: 39.0 plus or minus 2.0; POST

  4. Roles of nitric oxide synthase and cyclooxygenase in leg vasodilation and oxygen consumption during prolonged low-intensity exercise in untrained humans.

    PubMed

    Schrage, William G; Wilkins, Brad W; Johnson, Christopher P; Eisenach, John H; Limberg, Jacqueline K; Dietz, Niki M; Curry, Timothy B; Joyner, Michael J

    2010-09-01

    The vasodilator signals regulating muscle blood flow during exercise are unclear. We tested the hypothesis that in young adults leg muscle vasodilation during steady-state exercise would be reduced independently by sequential pharmacological inhibition of nitric oxide synthase (NOS) and cyclooxygenase (COX) with NG-nitro-L-arginine methyl ester (L-NAME) and ketorolac, respectively. We tested a second hypothesis that NOS and COX inhibition would increase leg oxygen consumption (VO2) based on the reported inhibition of mitochondrial respiration by nitric oxide. In 13 young adults, we measured heart rate (ECG), blood pressure (femoral venous and arterial catheters), blood gases, and venous oxygen saturation (indwelling femoral venous oximeter) during prolonged (25 min) steady-state dynamic knee extension exercise (60 kick/min, 19 W). Leg blood flow (LBF) was determined by Doppler ultrasound of the femoral artery. Whole body VO2 was measured, and leg VO2 was calculated from blood gases and LBF. Resting intra-arterial infusions of acetylcholine (ACh) and nitroprusside (NTP) tested inhibitor efficacy. Leg vascular conductance (LVC) to ACh was reduced up to 53±4% by L-NAME+ketorolac infusion, and the LVC responses to NTP were unaltered. Exercise increased LVC from 4±1 to 33.1±2 ml.min(-1).mmHg(-1) and tended to decrease after L-NAME infusion (31±2 ml.min(-1).mmHg(-1), P=0.09). With subsequent administration of ketorolac LVC decreased to 29.6±2 ml.min(-1).mmHg(-1) (P=0.02; n=9). While exercise continued, LVC returned to control values (33±2 ml.min(-1).mmHg(-1)) within 3 min, suggesting involvement of additional vasodilator mechanisms. In four additional subjects, LVC tended to decrease with L-NAME infusion alone (P=0.08) but did not demonstrate the transient recovery. Whole body and leg VO2 increased with exercise but were not altered by L-NAME or L-NAME+ketorolac. These data indicate a modest role for NOS- and COX-mediated vasodilation in the leg of exercising

  5. The Effects of Nandrolone Decanoate Along with Prolonged Low-Intensity Exercise on Susceptibility to Ventricular Arrhythmias.

    PubMed

    Binayi, Fateme; Joukar, Siyavash; Najafipour, Hamid; Karimi, Abdolah; Karimi, Ali; Abdollahi, Farzane; Masumi, Yaser

    2016-01-01

    We examined the influence of chronic administration of nandrolone decanoate with low-intensity endurance swimming exercise on susceptibility to lethal ventricular arrhythmias in rat. The animal groups included the control group, exercise group (EX), nandrolone group (Nan), vehicle group (Arach), trained vehicle group (Arach + Ex) and trained nandrolone group (Nan + Ex) that treated for 8 weeks. Then, arrhythmia induction was performed by intravenous infusion of aconitine and electrocardiogram recorded. Then, malondialdehyde (MDA), hydroxyproline (HYP) and glutathione peroxidase of heart tissue were measured. Chronic administration of nandrolone with low-intensity endurance swimming exercise had no significant effect on blood pressure, heart rate and basal ECG parameters except RR interval that showed increase (P < 0.05). Low-intensity exercise could prevent the incremental effect of nandrolone on MDA and HYP significantly. It also increased the heart hypertrophy index (P < 0.05) and reduced the abating effect of nandrolone on animal weighting. Nandrolone along with exercise significantly increased the duration of VF (P < 0.05) and reduced the VF latency (P < 0.05). The findings suggest that chronic co-administration of nandrolone with low-intensity endurance swimming exercise to some extent facilitates the occurrence of ventricular fibrillation in rat. Complementary studies are needed to elucidate the involved mechanisms of this abnormality. PMID:25636207

  6. Effects of supplementation with free glutamine and the dipeptide alanyl-glutamine on parameters of muscle damage and inflammation in rats submitted to prolonged exercise.

    PubMed

    Cruzat, Vinicius Fernandes; Rogero, Marcelo Macedo; Tirapegui, Julio

    2010-01-01

    In this study, we investigated the effect of the supplementation with the dipeptide L-alanyl-L-glutamine (DIP) and a solution containing L-glutamine and L-alanine on plasma levels markers of muscle damage and levels of pro-inflammatory cytokines and glutamine metabolism in rats submitted to prolonged exercise. Rats were submitted to sessions of swim training for 6 weeks. Twenty-one days prior to euthanasia, the animals were supplemented with DIP (n = 8) (1.5 g.kg(-1)), a solution of free L-glutamine (1 g.kg(-1)) and free L-alanine (0.61 g.kg(-1)) (G&A, n = 8) or water (control (CON), n = 8). Animals were killed at rest before (R), after prolonged exercise (PE-2 h of exercise). Plasma concentrations of glutamine, glutamate, tumour necrosis factor-alpha (TNF-alpha), prostaglandin E2 (PGE2) and activity of creatine kinase (CK), lactate dehydrogenase (LDH) and muscle concentrations of glutamine and glutamate were measured. The concentrations of plasma TNF-alpha, PGE2 and the activity of CK were lower in the G&A-R and DIP-R groups, compared to the CON-R. Glutamine in plasma (p < 0.04) and soleus muscle (p < 0.001) was higher in the DIP-R and G&A-R groups relative to the CON-R group. G&A-PE and DIP-PE groups exhibited lower concentrations of plasma PGE2 (p < 0.05) and TNF-alpha (p < 0.05), and higher concentrations of glutamine and glutamate in soleus (p < 0.001) and gastrocnemius muscles (p < 0.05) relative to the CON-PE group. We concluded that supplementation with free L-glutamine and the dipeptide LL-alanyl-LL-glutamine represents an effective source of glutamine, which may attenuate inflammation biomarkers after periods of training and plasma levels of CK and the inflammatory response induced by prolonged exercise. PMID:19885855

  7. Caffeine vs caffeine-free sports drinks: effects on urine production at rest and during prolonged exercise.

    PubMed

    Wemple, R D; Lamb, D R; McKeever, K H

    1997-01-01

    We compared the effects of caffeinated vs non-caffeinated carbohydrate electrolyte (CE) drinks on urine volume (UV), free water clearance (CH2O), fractional excretion of water (FEH2O), and osmolar excretion during 4 h of rest or 1 h rest followed by 3 h of cycling at 60% VO2max in six subjects. We also tested maximal performance at 85% VO2max following the 3-h exercise trials. Throughout the two resting trials and the two rest + exercise trials, subjects ingested CE (total volume = 35 ml/kg) without (PLAC) or with (CAFF) caffeine (25 mg/dl). Blood samples were collected, and body weight and UV were recorded every hour. Urine and blood were analyzed for osmolality and creatinine, and plasma catecholamine concentrations were determined. At rest, mean (+/-SE) UV between 60 min and 240 min was greater for CAFF (1843 +/- 166 ml) vs PLAC (1411 +/- 181 ml) (p < 0.01); during exercise the difference in UV between CAFF (398 +/- 32 ml) and PLAC (490 +/- 57 ml) was not significant. Cycling performance was unaffected by caffeine. Plasma catecholamine concentrations were not different between PLAC and CAFF but were greater during exercise than rest (p < 0.01) and may have counteracted the diuretic effect of caffeine observed at rest. Thus, CAFF consumed in CE during moderate endurance exercise apparently does not compromise bodily hydration status. PMID:9059904

  8. Dietary Supplementation with the Microalga Galdieria sulphuraria (Rhodophyta) Reduces Prolonged Exercise-Induced Oxidative Stress in Rat Tissues

    PubMed Central

    Carfagna, Simona; Napolitano, Gaetana; Barone, Daniela; Pinto, Gabriele; Venditti, Paola

    2015-01-01

    We studied the effects of ten-day 1% Galdieria sulphuraria dietary supplementation on oxidative damage and metabolic changes elicited by acute exercise (6-hour swimming) determining oxygen consumption, lipid hydroperoxides, protein bound carbonyls in rat tissue (liver, heart, and muscle) homogenates and mitochondria, tissue glutathione peroxidase and glutathione reductase activities, glutathione content, and rates of H2O2 mitochondrial release. Exercise increased oxidative damage in tissues and mitochondria and decreased tissue content of reduced glutathione. Moreover, it increased State 4 and decreased State 3 respiration in tissues and mitochondria. G. sulphuraria supplementation reduced the above exercise-induced variations. Conversely, alga supplementation was not able to modify the exercise-induced increase in mitochondrial release rate of hydrogen peroxide and in liver and heart antioxidant enzyme activities. The alga capacity to reduce lipid oxidative damage without reducing mitochondrial H2O2 release can be due to its high content of C-phycocyanin and glutathione, which are able to scavenge peroxyl radicals and contribute to phospholipid hydroperoxide metabolism, respectively. In conclusion, G. sulphuraria ability to reduce exercise-linked oxidative damage and mitochondrial dysfunction makes it potentially useful even in other conditions leading to oxidative stress, including hyperthyroidism, chronic inflammation, and ischemia/reperfusion. PMID:25874021

  9. Dietary supplementation with the microalga Galdieria sulphuraria (Rhodophyta) reduces prolonged exercise-induced oxidative stress in rat tissues.

    PubMed

    Carfagna, Simona; Napolitano, Gaetana; Barone, Daniela; Pinto, Gabriele; Pollio, Antonino; Venditti, Paola

    2015-01-01

    We studied the effects of ten-day 1% Galdieria sulphuraria dietary supplementation on oxidative damage and metabolic changes elicited by acute exercise (6-hour swimming) determining oxygen consumption, lipid hydroperoxides, protein bound carbonyls in rat tissue (liver, heart, and muscle) homogenates and mitochondria, tissue glutathione peroxidase and glutathione reductase activities, glutathione content, and rates of H2O2 mitochondrial release. Exercise increased oxidative damage in tissues and mitochondria and decreased tissue content of reduced glutathione. Moreover, it increased State 4 and decreased State 3 respiration in tissues and mitochondria. G. sulphuraria supplementation reduced the above exercise-induced variations. Conversely, alga supplementation was not able to modify the exercise-induced increase in mitochondrial release rate of hydrogen peroxide and in liver and heart antioxidant enzyme activities. The alga capacity to reduce lipid oxidative damage without reducing mitochondrial H2O2 release can be due to its high content of C-phycocyanin and glutathione, which are able to scavenge peroxyl radicals and contribute to phospholipid hydroperoxide metabolism, respectively. In conclusion, G. sulphuraria ability to reduce exercise-linked oxidative damage and mitochondrial dysfunction makes it potentially useful even in other conditions leading to oxidative stress, including hyperthyroidism, chronic inflammation, and ischemia/reperfusion. PMID:25874021

  10. The effect of ice-slushy consumption on plasma vasoactive intestinal peptide during prolonged exercise in the heat.

    PubMed

    Burdon, Catriona A; Ruell, Patricia; Johnson, Nathan; Chapman, Phillip; O'Brien, Sinead; O'Connor, Helen T

    2015-01-01

    The aim of this study was to determine the effect of exercise in the heat on thermoregulatory responses and plasma vasoactive intestinal peptide concentration (VIP) and whether it is modulated by ice-slushy consumption. Ten male participants cycled at 62% V̇O2max for 90min in 32°C and 40% relative humidity. A thermoneutral (37°C) or ice-slushy (-1°C) sports drink was given at 3.5mlkg(-1) body mass every 15min during exercise. VIP and rectal temperature increased during exercise (mean±standard deviation: 4.6±4.4pmolL(-1), P=0.005; and 1.3±0.4°C, P<0.001 respectively) and were moderately associated (r=0.35, P=0.008). While rectal temperature and VIP were not different between trials, ice-slushy significantly reduced heat storage (P=0.010) and skin temperature (time×trial interaction P=0.038). It appears that VIP does not provide the signal linking cold beverage ingestion and lower skin temperature in the heat. PMID:25526655

  11. Handgrip and general muscular strength and endurance during prolonged bedrest with isometric and isotonic leg exercise training

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Starr, J. C.; Van Beaumont, W.; Convertino, V. A.

    1983-01-01

    Measurements of maximal grip strength and endurance at 40 percent max strength were obtained for 7 men 19-21 years of age, 1-2 days before and on the first recovery day during three 2-week bedrest (BR) periods, each separated by a 3-week ambulatory recovery period. The subjects performed isometric exercise (IME) for 1 hr/day, isotonic exercise (ITE) for 1 hr/day, and no exercise (NOE) in the three BR periods. It was found that the mean maximal grip strength was unchanged after all three BR periods. Mean grip endurance was found to be unchanged after IME and ITE training, but was significantly reduced after NOE. These results indicate that IME and ITE training during BR do not increase or decrease maximal grip strength, alghough they prevent loss of grip endurance, while the maximal strength of all other major muscle groups decreases in proportion to the length of BR to 70 days. The maximal strength reduction of the large muscle groups was found to be about twice that of the small muscle groups during BR. In addition, it is shown that changes in maximal strength after spaceflight, BR, or water immersion deconditioning cannot be predicted from changes in submaximal or maximal oxygen uptake values.

  12. Concurrent Exercise on a Gravity-Independent Device during Simulated Microgravity

    PubMed Central

    Cotter, Joshua A.; Yu, Alvin; Haddad, Fadia; Kreitenberg, Arthur; Baker, Michael J.; Tesch, Per A.; Baldwin, Kenneth M.; Caiozzo, Vincent J.; Adams, Gregory R.

    2014-01-01

    Purpose To examine the effect of a high-intensity concurrent training program utilizing a single gravity-independent device on maintaining skeletal muscle function and aerobic capacity during short-term unilateral lower limb suspension (ULLS). Methods Nineteen subjects (10 male; 9 female; 21.0 ± 2.5 yr, 65.4 ± 12.2 kg) were separated into 2 groups: 1) 10 day unilateral lower limb suspension only (ULLS; n = 9) and 2) 10 day ULLS plus aerobic and resistance training (ULLS+EX; n = 10). Exercise was performed on a single gravity-independent Multi-Mode Exercise Device (M-MED) with alternating days of high-intensity interval aerobic training and maximal exertion resistance training. Results Aerobic capacity increased by 7% in ULLS+EX (P < 0.05). Knee extensor and ankle plantar flexor three repetition max increased in the ULLS+EX group (P < 0.05) but this change was only different than ULLS in the plantar flexors (P < 0.05). Peak torque levels decreased with ULLS but were increased for the knee extensors and attenuated for the ankle plantar flexors with ULLS+EX (P < 0.05). A shift towards type IIx myosin heavy chain mRNA occurred with ULLS and was reversed with ULLS+EX in the vastus lateralis (P < 0.05) but not the soleus. Myostatin and atrogin increased with ULLS in both the vastus lateralis and soleus but this change was mitigated with ULLS+EX only in the vastus lateralis (P = 0.0551 for myostatin; P < 0.05 for atrogin). Citrate synthase was decreased in the soleus during ULLS but was increased with ULLS+EX (P < 0.05). Conclusion These results indicate that an M-MED class countermeasure device appears to be effective at mitigating the deconditioning effects of microgravity simulated during a modified-ULLS protocol. PMID:25160844

  13. Exercises

    MedlinePlus

    ... Obstructive Pulmonary Disease (COPD) COPD: Lifestyle Management Exercises Exercises Make an Appointment Refer a Patient Ask a ... riding a stationary bike. Medication to Help You Exercise People with COPD often use a metered-dose ...

  14. Effectiveness of ice-vest cooling in prolonging work tolerance time during heavy exercise in the heat for personnel wearing Canadian forces chemical defense ensembles

    SciTech Connect

    Bain, B.

    1991-01-01

    Effectiveness of a portable, ice-pack cooling vest (Steelevest) in prolonging work tolerance time in chemical defense clothing in the heat (33 C dry bulb, 33% relative humidity or 25 C WBGT) was evaluated while subjects exercised at a metabolic rate of approx. 700 watts. Subjects were six male volunteers. The protocol consisted of a 20 minute treadmill walk at 1.33 m/s. and 7.5% grade, followed by 15 minutes of a lifting task, 5 minutes rest, then another 20 minutes of lifting task for a total of one hour. The lifting task consisted of lifting of 20 kg box, carrying it 3 meters and setting it down. This was followed by a 6 m walk (3m back to the start point and 3 m back to the box) 15 sec after which the lifting cycle began again. The work was classified as heavy as previously defined. This protocol was repeated until the subjects were unable to continue or they reached a physiological endpoint. Time to voluntary cessation or physiological endpoint was called the work tolerance time. Physiological endpoints were rectal temperature of 39 C, heart rate exceeding 95% of maximum for two consecutive minutes or visible loss of motor control or nausea. The cooling vest had no effect on work tolerance time, rate of rise of rectal temperature or sweat loss. It was concluded that the Steelvest ice-vest is ineffective in prolonging work tolerance time and preventing increases in rectal temperature while wearing chemical protective clothing.

  15. Spartathlon, a 246 kilometer foot race: effects of acute inflammation induced by prolonged exercise on circulating progenitor reparative cells.

    PubMed

    Goussetis, Evgenios; Spiropoulos, Antonia; Tsironi, Maria; Skenderi, Katerina; Margeli, Alexandra; Graphakos, Stelios; Baltopoulos, Panayiotis; Papassotiriou, Ioannis

    2009-01-01

    Endothelial progenitor cells (EPCs) and the recently described circulating fibrocytes (CFs) are strongly associated with tissue repair. We investigated the kinetics of both "repair" progenitor cells in healthy athletes who participated in the "Spartahlon" ultradistance foot race (246 km continuous running exercise), which provides a unique model of inducing dramatic systemic inflammatory changes. Peripheral blood mononuclear cells (PBMCs) were isolated from 10 volunteer athletes, who completed successfully the race, before, at the end, and at 48 h post-race. EPCs and CFs were detected as endothelial colony-forming units (CFU-ECs) and as the number of adherent with a spindle-shaped morphology Collagen I(+) cells detected after 6-day culture of PBMCs, respectively. The marked increase of plasma levels of CRP, IL-6, SAA, MCP-1, IL-8, sVCAM-1, sICAM-1, thrombomodulin (sTM) and NT-pro-BNP at the end of race established acute inflammation and tissue injury. EPCs increased by nearly eleven-fold in peripheral blood at the end of the race from 44.5+/-2.5/ml to 494.6+/-27.9/ml and remained increased 428.5+/-31.5/ml at 48 h post-race (p<0.0001). The number of the fibrocytes cultured from PBMCs obtained before, at the end, and 48 h post-race did not reveal any significant difference. These findings indicate that bone marrow responses to acute inflammatory damage, induced by exhausting exercise, with a rapid release of EPCs but not CFs into circulation. Given the ability of EPCs to promote angiogenesis and vascular regeneration, we may suggest that this kind of cell mobilization may serve as a physiologic repair mechanism in acute inflammatory tissue injury. PMID:19233694

  16. The Accumulative Effect of Concentric-Biased and Eccentric-Biased Exercise on Cardiorespiratory and Metabolic Responses to Subsequent Low-Intensity Exercise: A Preliminary Study

    PubMed Central

    Gavin, James Peter; Myers, Stephen; Willems, Mark Elisabeth Theodorus

    2015-01-01

    The study investigated the accumulative effect of concentric-biased and eccentric-biased exercise on cardiorespiratory, metabolic and neuromuscular responses to low-intensity exercise performed hours later. Fourteen young men cycled at low-intensity (~60 rpm at 50% maximal oxygen uptake) for 10 min before, and 12 h after: concentric-biased, single-leg cycling exercise (CON) (performed ~19:30 h) and eccentric-biased, double-leg knee extension exercise (ECC) (~06:30 h the following morning). Respiratory measures were sampled breath-by-breath, with oxidation values derived from stoichiometry equations. Knee extensor neuromuscular function was assessed before and after CON and ECC. Cardiorespiratory responses during low-intensity cycling were unchanged by accumulative CON and ECC. The RER was lower during low-intensity exercise 12 h after CON and ECC (0.88 ± 0.08), when compared to baseline (0.92 ± 0.09; p = 0.02). Fat oxidation increased from baseline (0.24 ± 0.2 g·min−1) to 12 h after CON and ECC (0.39 ± 0.2 g·min−1; p = 0.01). Carbohydrate oxidation decreased from baseline (1.59 ± 0.4 g·min−1) to 12 h after CON and ECC (1.36 ± 0.4 g·min−1; p = 0.03). These were accompanied by knee extensor force loss (right leg: −11.6%, p < 0.001; left leg: −10.6%, p = 0.02) and muscle soreness (right leg: 2.5 ± 0.9, p < 0.0001; left leg: 2.3 ± 1.2, p < 0.01). Subsequent concentric-biased and eccentric-biased exercise led to increased fat oxidation and decreased carbohydrate oxidation, without impairing cardiorespiration, during low-intensity cycling. An accumulation of fatiguing and damaging exercise increases fat utilisation during low intensity exercise performed as little as 12 h later. PMID:26839613

  17. Exercise training, but not resveratrol, improves metabolic and inflammatory status in skeletal muscle of aged men

    PubMed Central

    Olesen, Jesper; Gliemann, Lasse; Biensø, Rasmus; Schmidt, Jakob; Hellsten, Ylva; Pilegaard, Henriette

    2014-01-01

    The aim was to investigate the metabolic and anti-inflammatory effects of resveratrol alone and when combined with exercise training in skeletal muscle of aged human subjects. Healthy, physically inactive men (60–72 years old) were randomized to either 8 weeks of daily intake of 250 mg resveratrol or placebo or to 8 weeks of high-intensity exercise training with 250 mg resveratrol or placebo. Before and after the interventions, resting blood samples and muscle biopsies were obtained and a one-legged knee-extensor endurance exercise test was performed. Exercise training increased skeletal muscle peroxisome proliferator-activated receptor-γ co-activator-1α mRNA ∼1.5-fold, cytochrome c protein ∼1.3-fold, cytochrome c oxidase I protein ∼1.5-fold, citrate synthase activity ∼1.3-fold, 3-hydroxyacyl-CoA dehydrogenase activity ∼1.3-fold, inhibitor of κB-α and inhibitor of κB-β protein content ∼1.3-fold and time to exhaustion in the one-legged knee-extensor endurance exercise test by ∼1.2-fold, with no significant additive or adverse effects of resveratrol on these parameters. Despite an overall ∼25% reduction in total acetylation level in skeletal muscle with resveratrol, no exclusive resveratrol-mediated metabolic effects were observed on the investigated parameters. Notably, however, resveratrol blunted an exercise training-induced decrease (∼20%) in protein carbonylation and decrease (∼40%) in tumour necrosis factor α mRNA content in skeletal muscle. In conclusion, resveratrol did not elicit metabolic improvements in healthy aged subjects; in fact, resveratrol even impaired the observed exercise training-induced improvements in markers of oxidative stress and inflammation in skeletal muscle. Collectively, this highlights the metabolic efficacy of exercise training in aged subjects and does not support the contention that resveratrol is a potential exercise mimetic in healthy aged subjects. PMID:24514907

  18. A rare knee extensor mechanism injury: Vastus intermedius tendon rupture

    PubMed Central

    Cetinkaya, Engin; Aydin, Canan Gonen; Akman, Yunus Emre; Gul, Murat; Arikan, Yavuz; Aycan, Osman Emre; Kabukcuoglu, Yavuz Selim

    2015-01-01

    Introduction Quadriceps tendon injuries are rare. There is a limited number of studies in the literature, reporting partial quadriceps tendon ruptures. We did not find any study reporting an isolated vastus intermedius tendon injury in the literature. Presentation of case A 22 years old professional rugby player with the complaints of pain in the right lower limb, decreased range of motion in right knee and a mass in the mid-anterior of the right thigh applied following an overloading on his hyperflexed knee during a rugby match. T2 sequence magnetic resonance images revealed discontinuity in the vastus intermedius tendon and intramuscular hematoma. The patient has been conservatively treated. Discussion Quadriceps tendon ruptures generally occur after the 4th decade in the presence of degenerative changes. Our case is a young professional rugby player. Isolated vastus intermedius tendon rupture is unusual. Conservative treatment is performed as the intermedius tendon is in the deepest layer of the quadriceps muscle. Conclusion We report the first case of isolated rupture of the vastus intermedius tendon in the literature and we claim that disorder may be succesfully treated with conservative treatment and adequate physiotheraphy. PMID:26298093

  19. Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise.

    PubMed

    Périard, J D; Racinais, S

    2015-06-01

    This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750 kJ self-paced time trial in HOT (35 °C) and COOL (20 °C) conditions. Exercise time was longer in HOT (56 min) compared with COOL (49 min; P < 0.001). Power output in HOT was significantly lower from 40% of work completed onward (P < 0.01). Rectal temperature increased to 39.6 ± 0.6 °C (HOT) and 38.8 ± 0.5 °C (COOL; P < 0.01). Skin temperature, skin blood flow, and heart rate were higher throughout HOT compared with COOL (P < 0.05). A similar increase in ventilation (P < 0.05) and decrease in end-tidal partial pressure of CO2 (PETCO2 ; P < 0.05) occurred in both conditions. Arterial blood pressure and oxygen uptake were lower from 50% of work completed onward in HOT compared with COOL (P < 0.01). MCA Vmean increased at 10% in both conditions (P < 0.01), decreasing thereafter (P < 0.01) and to a greater extent in HOT from 40% of work completed onward (P < 0.05). Therefore, despite a comparable ventilatory response and PETCO2 in the HOT and COOL conditions, the greater level of thermal strain developing in the heat appears to have exacerbated the reduction in MCA Vmean, in part via increases in peripheral blood flow and a decrease in arterial blood pressure. PMID:25943664

  20. Inhibition of α-adrenergic vasoconstriction in exercising human thigh muscles

    PubMed Central

    Wray, D Walter; Fadel, Paul J; Smith, Michael L; Raven, Peter; Sander, Mikael

    2004-01-01

    The mechanisms underlying metabolic inhibition of sympathetic responses within exercising skeletal muscle remain incompletely understood. The aim of the present study was to test whether α2-adrenoreceptor-mediated vasoconstriction was more sensitive to metabolic inhibition than α1-vasoconstriction during dynamic knee-extensor exercise. We studied healthy volunteers using two protocols: (1) wide dose ranges of the α-adrenoreceptor agonists phenylephrine (PE, α1 selective) and BHT-933 (BHT, α2 selective) were administered intra-arterially at rest and during 27 W knee-extensor exercise (n = 13); (2) flow-adjusted doses of PE (0.3 μg kg−1 l−1) and BHT (15 μg kg−1 l−1) were administered at rest and during ramped exercise (7 W to 37 W; n= 10). Ultrasound Doppler and thermodilution techniques provided direct measurements of femoral blood flow (FBF). PE (0.8 μg kg−1) and BHT (40 μg kg−1) produced comparable maximal reductions in FBF at rest (−58 ± 6 versus−64 ± 4%). Despite increasing the doses, PE (1.6 μg kg−1 min−1) and BHT (80 μg kg−1 min−1) caused significantly smaller changes in FBF during 27 W exercise (−13 ± 4 versus−3 ± 5%). During ramped exercise, significant vasoconstriction at lower intensities (7 and 17 W) was seen following PE (−16 ± 5 and −16 ± 4%), but not BHT (−2 ± 4 and −4 ± 5%). At the highest intensity (37 W), FBF was not significantly changed by either drug. Collectively, these data demonstrate metabolic inhibition of α-adrenergic vasoconstriction in large postural muscles of healthy humans. Both α1- and α2-adrenoreceptor agonists produce comparable vasoconstriction in the resting leg, and dynamic thigh exercise attenuates α1- and α2-mediated vasoconstriction similarly. However, α2-mediated vasoconstriction appears more sensitive to metabolic inhibition, because α2 is completely inhibited even at low workloads, whereas α1 becomes progressively inhibited with increasing workloads. PMID

  1. Exerciser

    NASA Technical Reports Server (NTRS)

    Lem, J. D.

    1977-01-01

    The Mark I exerciser which was added for the second and third Skylab missions, was used for a number of arm and leg exercises. This unit is a modified version of a commercial device. This is an iso-kinetic, or constant velocity, exerciser which retards the speed at which the user is allowed to move. The user applies a maximum effort and the device automatically varies the opposing resistance to maintain speed of translation at a constant preselected value.

  2. Movement-Related Cortical Potential Amplitude Reduction after Cycling Exercise Relates to the Extent of Neuromuscular Fatigue

    PubMed Central

    Spring, Jérôme Nicolas; Place, Nicolas; Borrani, Fabio; Kayser, Bengt; Barral, Jérôme

    2016-01-01

    Exercise-induced fatigue affects the motor control and the ability to generate a given force or power. Surface electroencephalography allows researchers to investigate movement-related cortical potentials (MRCP), which reflect preparatory brain activity 1.5 s before movement onset. Although the MRCP amplitude appears to increase after repetitive single-joint contractions, the effects of large-muscle group dynamic exercise on such pre-motor potential remain to be described. Sixteen volunteers exercised 30 min at 60% of the maximal aerobic power on a cycle ergometer, followed by a 10-km all-out time trial. Before and after each of these tasks, knee extensor neuromuscular function was investigated using maximal voluntary contractions (MVC) combined with electrical stimulations of the femoral nerve. MRCP was recorded during 60 knee extensions after each neuromuscular sequence. The exercise resulted in a significant decrease in the knee extensor MVC force after the 30-min exercise (−10 ± 8%) and the time trial (−21 ± 9%). The voluntary activation level (VAL; −6 ± 8 and −12 ± 10%), peak twitch (Pt; −21 ± 16 and −32 ± 17%), and paired stimuli (P100 Hz; −7 ± 11 and −12 ± 13%) were also significantly reduced after the 30-min exercise and the time trial. The first exercise was followed by a decrease in the MRCP, mainly above the mean activity measured at electrodes FC1-FC2, whereas the reduction observed after the time trial was related to the FC1-FC2 and C2 electrodes. After both exercises, the reduction in the late MRCP component above FC1-FC2 was significantly correlated with the reduction in P100 Hz (r = 0.61), and the reduction in the same component above C2 was significantly correlated with the reduction in VAL (r = 0.64). In conclusion, large-muscle group exercise induced a reduction in pre-motor potential, which was related to muscle alterations and resulted in the inability to produce a maximal voluntary contraction. PMID:27313522

  3. Movement-Related Cortical Potential Amplitude Reduction after Cycling Exercise Relates to the Extent of Neuromuscular Fatigue.

    PubMed

    Spring, Jérôme Nicolas; Place, Nicolas; Borrani, Fabio; Kayser, Bengt; Barral, Jérôme

    2016-01-01

    Exercise-induced fatigue affects the motor control and the ability to generate a given force or power. Surface electroencephalography allows researchers to investigate movement-related cortical potentials (MRCP), which reflect preparatory brain activity 1.5 s before movement onset. Although the MRCP amplitude appears to increase after repetitive single-joint contractions, the effects of large-muscle group dynamic exercise on such pre-motor potential remain to be described. Sixteen volunteers exercised 30 min at 60% of the maximal aerobic power on a cycle ergometer, followed by a 10-km all-out time trial. Before and after each of these tasks, knee extensor neuromuscular function was investigated using maximal voluntary contractions (MVC) combined with electrical stimulations of the femoral nerve. MRCP was recorded during 60 knee extensions after each neuromuscular sequence. The exercise resulted in a significant decrease in the knee extensor MVC force after the 30-min exercise (-10 ± 8%) and the time trial (-21 ± 9%). The voluntary activation level (VAL; -6 ± 8 and -12 ± 10%), peak twitch (Pt; -21 ± 16 and -32 ± 17%), and paired stimuli (P100 Hz; -7 ± 11 and -12 ± 13%) were also significantly reduced after the 30-min exercise and the time trial. The first exercise was followed by a decrease in the MRCP, mainly above the mean activity measured at electrodes FC1-FC2, whereas the reduction observed after the time trial was related to the FC1-FC2 and C2 electrodes. After both exercises, the reduction in the late MRCP component above FC1-FC2 was significantly correlated with the reduction in P100 Hz (r = 0.61), and the reduction in the same component above C2 was significantly correlated with the reduction in VAL (r = 0.64). In conclusion, large-muscle group exercise induced a reduction in pre-motor potential, which was related to muscle alterations and resulted in the inability to produce a maximal voluntary contraction. PMID:27313522

  4. Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate only versus carbohydrate plus whey or casein hydrolysate.

    PubMed

    Oosthuyse, Tanja; Millen, Aletta M E

    2016-06-01

    Cardiac function is often suppressed following prolonged strenuous exercise and this may occur partly because of an energy deficit. This study compared left ventricular (LV) function by 2-dimensional echocardiography and tissue Doppler imaging (TDI) before and after ∼2.5 h of cycling (2-h steady-state 60% peak aerobic power output plus 16 km time trial) in 8 male cyclists when they ingested either placebo, carbohydrate-only (CHO-only), carbohydrate-casein hydrolysate (CHO-casein), or carbohydrate-whey hydrolysate (CHO-whey). No treatment-by-time interactions occurred, but pre-to-postexercise time effects occurred selectively. Although diastolic function measured by pulsed-wave Doppler early-to-late (E/A) transmitral blood flow velocity was suppressed in all trials from pre- to postexercise (mean change post-pre exercise: -0.53 (95% CI -0.15 to -0.91)), TDI early-to-late (e'/a') tissue velocity was significantly suppressed pre- to postexercise only with placebo, CHO-only, and CHO-whey (septal and lateral wall e'/a' average change: -0.62 (95% CI -1.12 to -0.12); -0.69 (95% CI -1.19 to -0.20); and -0.79 (95% CI -1.28 to -0.29), respectively) but not with CHO-casein (-0.40 (95% CI -0.90 to 0.09)). LV contractility was, or tended to be, significantly reduced pre- to postexercise with placebo, CHO-only, and CHO-whey (systolic blood pressure/end systolic volume change, mm Hg·mL(-1): -0.8 (95% CI -1.2 to -0.4), p = 0.0003; -0.5 (95% CI -0.9 to -0.02), p = 0.035; and -0.4 (95% CI -0.8 to 0.04), p = 0.086, respectively), but not with CHO-casein (-0.3 (95% CI -0.8 to 0.1), p = 0.22). However, ejection fraction (EF) and ventricular-arterial coupling were significantly reduced pre- to postexercise only with placebo (placebo change: EF, -4.6 (95% CI -8.4 to -0.7)%; stroke volume/end systolic volume, -0.3 (95% CI -0.6 to -0.04)). Despite no treatment-by-time interactions, pre-to-postexercise time effects observed with specific beverages may be meaningful for athletes

  5. Exercise

    MedlinePlus

    ... article Exercise / physical activity with MS Judy Boone, physical therapist Lynn Williams, Dan Melfi and Dave Altman discuss ... adjusted as changes occur in MS symptoms. A physical therapist experienced with MS can be helpful in designing, ...

  6. Efficacy of exercise training in SCT patients--who benefits most?

    PubMed

    Wiskemann, J; Kuehl, R; Dreger, P; Schwerdtfeger, R; Huber, G; Ulrich, C M; Jaeger, D; Bohus, M

    2014-03-01

    Patients undergoing allo-HCT often experience a substantial loss in physical performance. We have recently published the general effectiveness of an exercise intervention in 105 allo-HCT patients on physical performance and psychosocial well-being. However, predictor variables for differentiated treatment response remained unclear. To determine the impact of basic physical performance on treatment response, we assessed muscle strength and endurance performance at four assessment points before and after allo-HCT. The exercise group started training 2 weeks before admission and ended 6-8 weeks after discharge. Comparing initially fit with unfit classified patients, the fit patients lost 31% of the strength of the knee-extensors, whereas the unfit patients lost only 1% (P<0.05). For endurance capacity, fit patients lost 4% of their walking capability, whereas unfit patients gained 13% (P<0.05). The individual percent change was statistically different at the 0.05 level in all measures of physical performance. Individual training response in allo-HCT patients strongly depends on the initial physical performance level. Unfit patients can be trained safely and may benefit more from this exercise intervention than fit patients. This result is of major clinical relevance and should encourage hematologists to promote exercise even more in impaired/unfit allo-HCT patients. PMID:24317122

  7. Attenuation of eccentric exercise-induced muscle damage conferred by maximal isometric contractions: a mini review

    PubMed Central

    Lima, Leonardo C. R.; Denadai, Benedito S.

    2015-01-01

    Although, beneficial in determined contexts, eccentric exercise-induced muscle damage (EIMD) might be unwanted during training regimens, competitions and daily activities. There are a vast number of studies investigating strategies to attenuate EIMD response after damaging exercise bouts. Many of them consist of performing exercises that induce EIMD, consuming supplements or using equipment that are not accessible for most people. It appears that performing maximal isometric contractions (ISOs) 2–4 days prior to damaging bouts promotes significant attenuation of EIMD symptoms that are not related to muscle function. It has been shown that the volume of ISOs, muscle length in which they are performed, and interval between them and the damaging bout influence the magnitude of this protection. In addition, it appears that this protection is not long-lived, lasting no longer than 4 days. Although no particular mechanisms for these adaptations were identified, professionals should consider applying this non-damaging stimulus before submitting their patients to unaccustomed exercised. However, it seems not to be the best option for athletes or relatively trained individuals. Future, studies should focus on establishing if ISOs protect other populations (i.e., trained individuals) or muscle groups (i.e., knee extensors) against EIMD, as well as investigate different mechanisms for ISO-induced protection. PMID:26578972

  8. Shear-Wave Elastography Assessments of Quadriceps Stiffness Changes prior to, during and after Prolonged Exercise: A Longitudinal Study during an Extreme Mountain Ultra-Marathon.

    PubMed

    Andonian, Pierre; Viallon, Magalie; Le Goff, Caroline; de Bourguignon, Charles; Tourel, Charline; Morel, Jérome; Giardini, Guido; Gergelé, Laurent; Millet, Grégoire P; Croisille, Pierre

    2016-01-01

    In sports medicine, there is increasing interest in quantifying the elastic properties of skeletal muscle, especially during extreme muscular stimulation, to improve our understanding of the impact of alterations in skeletal muscle stiffness on resulting pain or injuries, as well as the mechanisms underlying the relationships between these parameters. Our main objective was to determine whether real-time shear-wave elastography (SWE) can monitor changes in quadriceps muscle elasticity during an extreme mountain ultra-marathon, a powerful mechanical stress model. Our study involved 50 volunteers participating in an extreme mountain marathon (distance: 330 km, elevation: +24,000 m). Quantitative SWE velocity and shear modulus measurements were performed in most superficial quadriceps muscle heads at the following 4 time points: before the race, halfway through the race, upon finishing the race and after recovery (+48 h). Blood biomarker levels were also measured. A significant decrease in the quadriceps shear modulus was observed upon finishing the race (3.31±0.61 kPa) (p<0.001) compared to baseline (3.56±0.63 kPa), followed by a partial recovery +48 h after the race (3.45±0.6 kPa) (p = 0.002) across all muscle heads, as well as for each of the following three muscle heads: the rectus femoris (p = 0.003), the vastus medialis (p = 0.033) and the vastus lateralis (p = 0.001). Our study is the first to assess changes in muscle stiffness during prolonged extreme physical endurance exercises based on shear modulus measurements using non-invasive SWE. We concluded that decreases in stiffness, which may have resulted from quadriceps overuse in the setting of supra-physiological stress caused by the extreme distance and unique elevation of the race, may have been responsible for the development of inflammation and muscle swelling. SWE may hence represent a promising tool for monitoring physiologic or pathological variations in muscle stiffness and may be useful for

  9. Effects of blood flow restriction duration on muscle activation and microvascular oxygenation during low-volume isometric exercise.

    PubMed

    Cayot, Trent E; Lauver, Jakob D; Silette, Christopher R; Scheuermann, Barry W

    2016-07-01

    The purpose of the investigation was to observe how varying occlusion durations affected neuromuscular activation and microvascular oxygenation during low-volume isometric knee extension exercise. Healthy, recreationally active males performed isometric knee extension at a variety of submaximal intensities under different blood flow restriction (BFR) occlusion durations. The occlusion pressure (130% SBP) was applied either 5 min prior to exercise (PO), immediately prior to exercise (IO) or not during exercise (CON). Surface electromyography (sEMG) and near-infrared spectroscopy (NIRS) was used to record the neuromuscular activation and microvascular oxygenation of the knee extensors during exercise. No difference in sEMG was observed in the vastus lateralis or vastus medialis during any exercise condition or any submaximal intensity. PO elicited greater microvascular deoxygenation (deoxy-[Hb + Mb]) compared to CON (P≤0·05) at all submaximal intensities and also compared to IO at 20% maximal voluntary contraction (MVC). IO resulted in a greater deoxy-[Hb + Mb] response during low-intensity exercise (20% and 40% MVC) compared to CON (P≤0·05). These findings suggest that applying BFR 5 min before exercise can enhance the exercise-induced metabolic stress (i.e. deoxy-[Hb + Mb]), measured via NIRS, during low-intensity exercise (20% MVC) compared to applying BFR immediately prior to exercise. Furthermore, the increased metabolic stress observed during IO is attenuated during high-intensity (60% MVC, 80% MVC) exercise when compared to CON conditions. Knowledge of the changes in exercise-induced metabolic stress between the various occlusion durations may assist in developing efficient BFR exercise programmes. PMID:25564998

  10. Effects of exercise-induced muscle damage on resting metabolic rate, sub-maximal running and post-exercise oxygen consumption.

    PubMed

    Burt, Dean Gareth; Lamb, Kevin; Nicholas, Ceri; Twist, Craig

    2014-01-01

    Exercise-induced muscle damage (EIMD), described as the acute weakness of the musculature after unaccustomed eccentric exercise, increases oxidative metabolism at rest and during endurance exercise. However, it is not known whether oxygen uptake during recovery from endurance exercise is increased when experiencing symptoms of EIMD. Therefore, the purpose of this study was to investigate the effects of EIMD on physiological and metabolic responses before, during and after sub-maximal running. After a 12 h fast, eight healthy male participants completed baseline measurements comprising resting metabolic rate (RMR), indirect markers of EIMD, 10 min of sub-maximal running and 30 min of recovery to ascertain excess post-exercise oxygen consumption (EPOC). Measurements were then repeated at 24 and 48 h after 100 Smith-machine squats. Data analysis revealed significant (P<0.05) increases in muscle soreness and creatine kinase (CK) and decreases in peak knee extensor torque at 24 and 48 h after squatting exercise. Moreover, RMR, physiological, metabolic and perceptual responses during sub-maximal running and EPOC were increased in the two days after squatting exercise (P<0.05). It is suggested that the elevated RMR was a consequence of a raised energy requirement for the degradation and resynthesis of damaged muscle fibres. The increased oxygen demand during sub-maximal running after muscle damage was responsible for the increase in EPOC. Individuals engaging in unaccustomed resistance exercise that results in muscle damage should be mindful of the increases in resting energy expenditure and increased metabolic demand to exercise in the days that follow. PMID:23566074

  11. The impact of 100 hours of exercise and sleep deprivation on cognitive function and physical capacities.

    PubMed

    Lucas, Samuel J E; Anson, J Greg; Palmer, Craig D; Hellemans, Ien J; Cotter, James D

    2009-05-01

    In this study, we examined the effect of 96-125 h of competitive exercise on cognitive and physical performance. Cognitive performance was assessed using the Stroop test (n = 9) before, during, and after the 2003 Southern Traverse adventure race. Strength (MVC) and strength endurance (time to failure at 70% current MVC) of the knee extensor and elbow flexor muscles were assessed before and after racing. Changes in vertical jump (n = 24) and 30-s Wingate performance (n = 27) were assessed in a different group of athletes. Complex response times were affected by the race (16% slower), although not significantly so (P = 0.18), and were dependent on exercise intensity (less so at 50% peak power output after racing). Reduction of strength (P < 0.05) of the legs (17%) and arms (11%) was equivalent (P = 0.17). Reductions in strength endurance were inconsistent (legs 18%, P = 0.09; arms 13%, P = 0.40), but were equivalent between limbs (P = 0.80). Similar reductions were observed in jump height (-8 +/- 9%, P < 0.01) and Wingate peak power (-7 +/- 15%, P = 0.04), mean power (-7 +/- 11%, P < 0.01), and end power (-10 +/- 11%, P < 0.01). We concluded that: moderate-intensity exercise may help complex decision making during sustained stress; functional performance was modestly impacted, and the upper and lower limbs were affected similarly despite being used disproportionately. PMID:19437188

  12. Sarcoplasmic reticulum function and muscle contractile character following fatiguing exercise in humans

    PubMed Central

    Hill, Christopher A; Thompson, Martin W; Ruell, Patricia A; Thom, Jeanette M; White, Michael J

    2001-01-01

    This study examined the alterations in calcium release, calcium uptake and calcium ATPase activity of skeletal muscle sarcoplasmic reticulum in response to a bout of intense dynamic knee extensor exercise, and the relationship between these changes and alterations in muscle contractile characteristics in the human quadriceps. In biopsy samples taken from the vastus lateralis, sarcoplasmic reticulum calcium release and calcium uptake were significantly depressed (P < 0.01 and 0.05, respectively) immediately following the exercise with no alteration in the sarcoplasmic reticulum Ca2+-ATPase activity. A 33 % reduction in the maximum voluntary isometric torque was found following the exercise, with reduced torques from electrically evoked isometric contractions at low frequencies of stimulation (10 and 20 Hz) but not at higher frequencies (50 and 100 Hz). The depressed calcium release was correlated (P < 0.05) with a decreased ratio of torques generated at 20:50 Hz, indicating an involvement in low frequency fatigue; however, no correlations between the muscle relaxation times or rates of change of torque and calcium uptake were observed. PMID:11251066

  13. Effects of a low-volume, vigorous intensity step exercise program on functional mobility in middle-aged adults.

    PubMed

    Doheny, Emer P; McGrath, Denise; Ditroilo, Massimiliano; Mair, Jacqueline L; Greene, Barry R; Caulfield, Brian; De Vito, Giuseppe; Lowery, Madeleine M

    2013-08-01

    Aging-related decline in functional mobility is associated with loss of independence. This decline may be mitigated through programs of physical activity. Despite reports of aging-related mobility impairment in middle-aged adults, this age group has been largely overlooked in terms of exercise programs that target functional mobility and the preservation of independence in older age. A method to quantitatively assess changes in functional mobility could direct rehabilitation in a proactive rather than reactive manner. Thirty-three healthy but sedentary middle-aged adults participated in a four week low-volume, vigorous intensity stepping exercise program. Two baseline testing sessions and one post-training testing session were conducted. Functional mobility was assessed using the timed up and go (TUG) test, with its constituent sit-to-walk and walk-to-sit phases examined using a novel inertial sensor-based method. Additionally, semi-tandem balance and knee extensor muscle isometric torque were assessed. Trunk acceleration during walk-to-sit reduced significantly post-training, suggesting altered movement control due to the exercise program. No significant training-induced changes in sit-to-walk acceleration, TUG time, balance or torque were observed. The novel method of functional mobility assessment presented provides a reliable means to quantify subtle changes in mobility during postural transitions. Over time, this exercise program may improve functional mobility. PMID:23568151

  14. Creatine ingestion augments dietary carbohydrate mediated muscle glycogen supercompensation during the initial 24 h of recovery following prolonged exhaustive exercise in humans.

    PubMed

    Roberts, Paul A; Fox, John; Peirce, Nicholas; Jones, Simon W; Casey, Anna; Greenhaff, Paul L

    2016-08-01

    Muscle glycogen availability can limit endurance exercise performance. We previously demonstrated 5 days of creatine (Cr) and carbohydrate (CHO) ingestion augmented post-exercise muscle glycogen storage compared to CHO feeding alone in healthy volunteers. Here, we aimed to characterise the time-course of this Cr-induced response under more stringent and controlled experimental conditions and identify potential mechanisms underpinning this phenomenon. Fourteen healthy, male volunteers cycled to exhaustion at 70 % VO2peak. Muscle biopsies were obtained at rest immediately post-exercise and after 1, 3 and 6 days of recovery, during which Cr or placebo supplements (20 g day(-1)) were ingested along with a prescribed high CHO diet (37.5 kcal kg body mass(-1) day(-1), >80 % calories CHO). Oral-glucose tolerance tests (oral-GTT) were performed pre-exercise and after 1, 3 and 6 days of Cr and placebo supplementation. Exercise depleted muscle glycogen content to the same extent in both treatment groups. Creatine supplementation increased muscle total-Cr, free-Cr and phosphocreatine (PCr) content above placebo following 1, 3 and 6 days of supplementation (all P < 0.05). Creatine supplementation also increased muscle glycogen content noticeably above placebo after 1 day of supplementation (P < 0.05), which was sustained thereafter. This study confirmed dietary Cr augments post-exercise muscle glycogen super-compensation, and demonstrates this occurred during the initial 24 h of post-exercise recovery (when muscle total-Cr had increased by <10 %). This marked response ensued without apparent treatment differences in muscle insulin sensitivity (oral-GTT, muscle GLUT4 mRNA), osmotic stress (muscle c-fos and HSP72 mRNA) or muscle cell volume (muscle water content) responses, such that another mechanism must be causative. PMID:27193231

  15. Hemodynamic responses to small muscle mass exercise in heart failure patients with reduced ejection fraction.

    PubMed

    Barrett-O'Keefe, Zachary; Lee, Joshua F; Berbert, Amanda; Witman, Melissa A H; Nativi-Nicolau, Jose; Stehlik, Josef; Richardson, Russell S; Wray, D Walter

    2014-11-15

    To better understand the mechanisms responsible for exercise intolerance in heart failure with reduced ejection fraction (HFrEF), the present study sought to evaluate the hemodynamic responses to small muscle mass exercise in this cohort. In 25 HFrEF patients (64 ± 2 yr) and 17 healthy, age-matched control subjects (64 ± 2 yr), mean arterial pressure (MAP), cardiac output (CO), and limb blood flow were examined during graded static-intermittent handgrip (HG) and dynamic single-leg knee-extensor (KE) exercise. During HG exercise, MAP increased similarly between groups. CO increased significantly (+1.3 ± 0.3 l/min) in the control group, but it remained unchanged across workloads in HFrEF patients. At 15% maximum voluntary contraction (MVC), forearm blood flow was similar between groups, while HFrEF patients exhibited an attenuated increase at the two highest intensities compared with controls, with the greatest difference at the highest workload (352 ± 22 vs. 492 ± 48 ml/min, HFrEF vs. control, 45% MVC). During KE exercise, MAP and CO increased similarly across work rates between groups. However, HFrEF patients exhibited a diminished leg hyperemic response across all work rates, with the most substantial decrement at the highest intensity (1,842 ± 64 vs. 2,675 ± 81 ml/min; HFrEF vs. control, 15 W). Together, these findings indicate a marked attenuation in exercising limb perfusion attributable to impairments in peripheral vasodilatory capacity during both arm and leg exercise in patients with HFrEF, which likely plays a role in limiting exercise capacity in this patient population. PMID:25260608

  16. Pre-Exercise Hyperhydration-Induced Bodyweight Gain Does Not Alter Prolonged Treadmill Running Time-Trial Performance in Warm Ambient Conditions

    PubMed Central

    Gigou, Pierre-Yves; Dion, Tommy; Asselin, Audrey; Berrigan, Felix; Goulet, Eric D. B.

    2012-01-01

    This study compared the effect of pre-exercise hyperhydration (PEH) and pre-exercise euhydration (PEE) upon treadmill running time-trial (TT) performance in the heat. Six highly trained runners or triathletes underwent two 18 km TT runs (~28 °C, 25%–30% RH) on a motorized treadmill, in a randomized, crossover fashion, while being euhydrated or after hyperhydration with 26 mL/kg bodyweight (BW) of a 130 mmol/L sodium solution. Subjects then ran four successive 4.5 km blocks alternating between 2.5 km at 1% and 2 km at 6% gradient, while drinking a total of 7 mL/kg BW of a 6% sports drink solution (Gatorade, USA). PEH increased BW by 1.00 ± 0.34 kg (P < 0.01) and, compared with PEE, reduced BW loss from 3.1% ± 0.3% (EUH) to 1.4% ± 0.4% (HYP) (P < 0.01) during exercise. Running TT time did not differ between groups (PEH: 85.6 ± 11.6 min; PEE: 85.3 ± 9.6 min, P = 0.82). Heart rate (5 ± 1 beats/min) and rectal (0.3 ± 0.1 °C) and body (0.2 ± 0.1 °C) temperatures of PEE were higher than those of PEH (P < 0.05). There was no significant difference in abdominal discomfort and perceived exertion or heat stress between groups. Our results suggest that pre-exercise sodium-induced hyperhydration of a magnitude of 1 L does not alter 80–90 min running TT performance under warm conditions in highly-trained runners drinking ~500 mL sports drink during exercise. PMID:23016126

  17. Pre-exercise hyperhydration-induced bodyweight gain does not alter prolonged treadmill running time-trial performance in warm ambient conditions.

    PubMed

    Gigou, Pierre-Yves; Dion, Tommy; Asselin, Audrey; Berrigan, Felix; Goulet, Eric D B

    2012-08-01

    This study compared the effect of pre-exercise hyperhydration (PEH) and pre-exercise euhydration (PEE) upon treadmill running time-trial (TT) performance in the heat. Six highly trained runners or triathletes underwent two 18 km TT runs (~28 °C, 25%-30% RH) on a motorized treadmill, in a randomized, crossover fashion, while being euhydrated or after hyperhydration with 26 mL/kg bodyweight (BW) of a 130 mmol/L sodium solution. Subjects then ran four successive 4.5 km blocks alternating between 2.5 km at 1% and 2 km at 6% gradient, while drinking a total of 7 mL/kg BW of a 6% sports drink solution (Gatorade, USA). PEH increased BW by 1.00 ± 0.34 kg (P < 0.01) and, compared with PEE, reduced BW loss from 3.1% ± 0.3% (EUH) to 1.4% ± 0.4% (HYP) (P < 0.01) during exercise. Running TT time did not differ between groups (PEH: 85.6 ± 11.6 min; PEE: 85.3 ± 9.6 min, P = 0.82). Heart rate (5 ± 1 beats/min) and rectal (0.3 ± 0.1 °C) and body (0.2 ± 0.1 °C) temperatures of PEE were higher than those of PEH (P < 0.05). There was no significant difference in abdominal discomfort and perceived exertion or heat stress between groups. Our results suggest that pre-exercise sodium-induced hyperhydration of a magnitude of 1 L does not alter 80-90 min running TT performance under warm conditions in highly-trained runners drinking ~500 mL sports drink during exercise. PMID:23016126

  18. Effects of Combined Aerobic and Resistance Exercise on Exercise Capacity, Muscle Strength and Quality of Life in HIV-Infected Patients: A Systematic Review and Meta-Analysis

    PubMed Central

    Gomes Neto, Mansueto; Conceição, Cristiano Sena; Carvalho, Vitor Oliveira; Brites, Carlos

    2015-01-01

    Background Many HIV-infected patients demonstrate disability and lower aerobic capacity. The inclusion of resistance training combined with aerobic exercise in a single program is known as combined aerobic and resistance exercise (CARE) and seems to be an effective strategy to improve muscle weakness, as well as aerobic capacity in HIV-infected patients. We performed a meta-analysis to investigate the effects of CARE in HIV-infected patients. Methods We searched MEDLINE, Cochrane Controlled Trials Register, EMBASE, CINAHL (from the earliest date available to august 2014) for controlled trials that evaluated the effects of CARE in HIV-infected patients. Weighted mean differences (WMD) and 95% confidence intervals (CIs) were calculated, and heterogeneity was assessed using the I2 test. Results Seven studies met the study criteria. CARE resulted in improvement in Peak VO2 WMD (4.48 mL·kg-1·min-1 95% CI: 2.95 to 6.0), muscle strength of the knee extensors WMD (25.06 Kg 95% CI: 10.46 to 39.66) and elbow flexors WMD (4.44 Kg 95% CI: 1.22 to 7.67) compared with no exercise group. The meta-analyses also showed significant improvement in Health status, Energy/Vitality and physical function domains of quality of life for participants in the CARE group compared with no exercise group. A nonsignificant improvement in social function domain of quality of life was found for participants in the CARE group compared with no exercise group. Conclusions Combined aerobic and resistance exercise may improve peak VO2, muscle strength and health status, energy and physical function domains of quality of life and should be considered as a component of care of HIV-infected individuals. PMID:26378794

  19. Prolonged pregnancy.

    PubMed

    Hollis, Brian

    2002-04-01

    Prolonged pregnancy is defined as any pregnancy that lasts 294 days or more. It is now well recognized that prolonged pregnancy is associated with an increased risk of perinatal mortality and morbidity. It is these complications of pregnancy that have led obstetricians to adopt a policy of induction of labour before the onset of the post-term period. The induction of labour between 41 and 42 weeks is, however, a very crude strategy for reducing term and post-term stillbirth rates. Although the risk of fetal death is increased after 42 weeks, many more fetuses die in utero between 37 and 42 weeks than die in the post-term period. It appears that smaller term fetuses run a greater risk than their larger counterparts, and that current methods of antepartum assessment of the term fetus are still inadequate. It behoves us as obstetricians to improve our capabilities in identifying the compromised fetus at term. This review puts into perspective the most recent publications and highlights areas requiring further study. PMID:11914699

  20. Effects of stabilization exercises with a Swiss ball on neck-shoulder pain and mobility of adults with prolonged exposure to VDTs.

    PubMed

    Ahn, Jeoung-Ah; Kim, Joong-Hwi; Bendik, Anthony L; Shin, Ju-Yong

    2015-04-01

    [Purpose] This study compared the effects on neck-shoulder pain and mobility of strengthening exercises for the neck flexors and scapular retractors performed on a Swiss ball and a mat. [Subjects] Twenty student volunteers were the subjects. [Methods] The students were randomly assigned to two groups: Mat group (n=10), and Swiss ball group (n=10). At pre-test, post-test, and 1-week follow-up pain was assessed using the visual analogue scale (VAS), the pain pressure threshold (PPT) of the shoulder was measured with an algometer, and neck mobility was measured with a Zebris. [Results] The data analysis revealed that there was a significant decrease in pain and significant increase in neck flexion in both groups, and the Swiss ball group showed better results. [Conclusion] Strengthening the neck flexors and scapular retractors for stabilization of the neck using exercises on a Swiss ball was more effective at reducing the pain and stabilizing the neck than mat exercises. PMID:25995537

  1. Oral antioxidants improve leg blood flow during exercise in patients with chronic obstructive pulmonary disease.

    PubMed

    Rossman, Matthew J; Trinity, Joel D; Garten, Ryan S; Ives, Stephen J; Conklin, Jamie D; Barrett-O'Keefe, Zachary; Witman, Melissa A H; Bledsoe, Amber D; Morgan, David E; Runnels, Sean; Reese, Van R; Zhao, Jia; Amann, Markus; Wray, D Walter; Richardson, Russell S

    2015-09-01

    The consequence of elevated oxidative stress on exercising skeletal muscle blood flow as well as the transport and utilization of O2 in patients with chronic obstructive pulmonary disease (COPD) is not well understood. The present study examined the impact of an oral antioxidant cocktail (AOC) on leg blood flow (LBF) and O2 consumption during dynamic exercise in 16 patients with COPD and 16 healthy subjects. Subjects performed submaximal (3, 6, and 9 W) single-leg knee extensor exercise while LBF (Doppler ultrasound), mean arterial blood pressure, leg vascular conductance, arterial O2 saturation, leg arterial-venous O2 difference, and leg O2 consumption (direct Fick) were evaluated under control conditions and after AOC administration. AOC administration increased LBF (3 W: 1,604 ± 100 vs. 1,798 ± 128 ml/min, 6 W: 1,832 ± 109 vs. 1,992 ± 120 ml/min, and 9W: 2,035 ± 114 vs. 2,187 ± 136 ml/min, P < 0.05, control vs. AOC, respectively), leg vascular conductance, and leg O2 consumption (3 W: 173 ± 12 vs. 210 ± 15 ml O2/min, 6 W: 217 ± 14 vs. 237 ± 15 ml O2/min, and 9 W: 244 ± 16 vs 260 ± 18 ml O2/min, P < 0.05, control vs. AOC, respectively) during exercise in COPD, whereas no effect was observed in healthy subjects. In addition, the AOC afforded a small, but significant, improvement in arterial O2 saturation only in patients with COPD. Thus, these data demonstrate a novel beneficial role of AOC administration on exercising LBF, O2 consumption, and arterial O2 saturation in patients with COPD, implicating oxidative stress as a potential therapeutic target for impaired exercise capacity in this population. PMID:26188020

  2. The effect of hip joint muscle exercise on muscle strength and balance in the knee joint after meniscal injury.

    PubMed

    Park, Sun Ja; Kim, Young Mi; Kim, Ha Roo

    2016-04-01

    [Purpose] This study aimed to evaluate the effect of hip muscle strengthening on muscle strength and balance in the knee joint after a meniscal injury. [Subjects and Methods] This randomized control study enrolled 24 patients who had undergone arthroscopic treatment after a meniscal injury and began a rehabilitative exercise program 8 weeks after surgery. Subjects were divided into 2 groups of 12 subjects each: gluteus medius resistance exercise group and control group. This study investigated muscle strength and balance in the knee joint flexor, extensor, and abductor during an 8-week period. [Results] Measurements of knee extensor muscle strength revealed no significant difference between the control group and the experimental group. Measurements of abductor muscle strength, however, identified a significant difference between the 2 groups. The groups did not differ significantly with regard to balance measurements. [Conclusion] The results of this study suggest that this subject should be approached in light of the correlation between the hip abductor and injury to the lower extremities. PMID:27190461

  3. The effect of hip joint muscle exercise on muscle strength and balance in the knee joint after meniscal injury

    PubMed Central

    Park, Sun Ja; Kim, Young Mi; Kim, Ha Roo

    2016-01-01

    [Purpose] This study aimed to evaluate the effect of hip muscle strengthening on muscle strength and balance in the knee joint after a meniscal injury. [Subjects and Methods] This randomized control study enrolled 24 patients who had undergone arthroscopic treatment after a meniscal injury and began a rehabilitative exercise program 8 weeks after surgery. Subjects were divided into 2 groups of 12 subjects each: gluteus medius resistance exercise group and control group. This study investigated muscle strength and balance in the knee joint flexor, extensor, and abductor during an 8-week period. [Results] Measurements of knee extensor muscle strength revealed no significant difference between the control group and the experimental group. Measurements of abductor muscle strength, however, identified a significant difference between the 2 groups. The groups did not differ significantly with regard to balance measurements. [Conclusion] The results of this study suggest that this subject should be approached in light of the correlation between the hip abductor and injury to the lower extremities. PMID:27190461

  4. Maximal-intensity isometric and dynamic exercise performance after eccentric muscle actions.

    PubMed

    Byrne, Christopher; Eston, Roger

    2002-12-01

    A well-documented observation after eccentric exercise is a reduction in maximal voluntary force. However, little is known about the ability to maintain maximal isometric force or generate and maintain dynamic peak power. These aspects of muscle function were studied in seven participants (5 males, 2 females). Knee extensor isometric strength and rate of fatigue were assessed by a sustained 60 s maximal voluntary contraction at 80 degrees and 40 degrees knee flexion, corresponding to an optimal and a shortened muscle length, respectively. Dynamic peak power and rate of fatigue were assessed during a 30 s Wingate cycle test. Plasma creatine kinase was measured from a fingertip blood sample. These variables were measured before, 1 h after and 1, 2, 3 and 7 days after 100 repetitions of the eccentric phase of the barbell squat exercise (10 sets x 10 reps at 80% concentric one-repetition maximum). Eccentric exercise resulted in elevations in creatine kinase activity above baseline (274+/-109 U x l(-1); mean +/- s(x)) after 1 h (506+/-116 U x l(-1), P < 0.05) and 1 day (808+/-117 U x l(-1), P < 0.05). Isometric strength was reduced (P < 0.05) for 7 days (35% at 1 h, 5% at day 7) and the rate of fatigue was lower (P < 0.05) for 3 days at 80 degrees and for 1 day at 40 degrees. Wingate peak power was reduced to a lesser extent (P < 0.05) than isometric strength at 1 h (13%) and, although the time course of recovery was equal, the two variables differed in their pattern of recovery. Eccentrically exercised muscle was characterized by an inability to generate high force and power, but an improved ability to maintain force and power. Such functional outcomes are consistent with the proposition that type II fibres are selectively recruited or damaged during eccentric exercise. PMID:12477004

  5. The effects of electrical stimulation exercise on muscles injected with botulinum toxin type-A (botox).

    PubMed

    Fortuna, Rafael; Horisberger, Monika; Vaz, Marco Aurélio; Van der Marel, Robert; Herzog, Walter

    2013-01-01

    Botulinum toxin type A (BTX-A) is a frequently used treatment modality for a variety of neuromuscular disorders. It acts by preventing acetylcholine release at the motor nerve endings, inducing muscle paralysis. Although considered safe, studies suggest that BTX-A injections create adverse effects on target and non-target muscles. We speculate that these adverse effects are reduced by direct electrical stimulation (ES) exercising of muscles. The aims were to determine the effects of ES exercise on strength, mass, and contractile material in BTX-A injected muscles, and to investigate if BTX-A injections affect non-target muscles. Seventeen New Zealand White (NZW) rabbits were divided into three groups: (1) Control group received saline injections; (2) BTX-A group received monthly BTX-A (3.5 U/kg) injections into the quadriceps for six months and (3) BTX-A+ES group received monthly BTX-A injections and ES exercise three times a week for six months. Outcome measures included knee extensor torque, muscle mass, and contractile material percentage area in injected and contralateral, non-injected quadriceps. Glycogen depletion and direct muscle stimulation were used to assess possible muscle inhibition in non-injected quadriceps. ES exercise partially prevented muscle weakness, atrophy, and contractile material loss in injected muscles, and mostly prevented muscle degeneration in contralateral, non-injected muscles. Non-injected muscles of BTX-A+ES group showed higher force with direct muscle compared to nerve stimulation, and retained glycogen following the depletion protocol, suggesting that BTX-A inhibited activation in non-target muscles. We conclude that ES exercise provides some protection from degeneration to target and non-target muscles during BTX-A treatments. PMID:23122225

  6. Prolonged ingestion of prehydrolyzed whey protein induces little or no change in digestive enzymes, but decreases glutaminase activity in exercising rats.

    PubMed

    Nery-Diez, Ana Cláudia C; Carvalho, Iara R; Amaya-Farfán, Jaime; Abecia-Soria, Maria Inés; Miyasaka, Célio K; Ferreira, Clécio da S

    2010-08-01

    Because consumption of whey protein hydrolysates is on the increase, the possibility that prolonged ingestion of whey protein hydrolysates affect the digestive system of mammals has prompted us to evaluate the enzymatic activities of pepsin, leucine-aminopeptidase, chymotrypsin, trypsin, and glutaminase in male Wistar rats fed diets containing either a commercial whey isolate or a whey protein hydrolysate with medium degree of hydrolysis and to compare the results with those produced by physical training (sedentary, sedentary-exhausted, trained, and trained-exhausted) in the treadmill for 4 weeks. The enzymatic activities were determined by classical procedures in all groups. No effect due to the form of the whey protein in the diet was seen in the activities of pepsin, trypsin, chymotrypsin, and leucine-aminopeptidase. Training tended to increase the activity of glutaminase, but exhaustion promoted a decrease in the trained animals, and consumption of the hydrolysate decreased it even further. The results are consistent with the conclusion that chronic consumption of a whey protein hydrolysate brings little or no modification of the proteolytic digestive system and that the lowering of glutaminase activity may be associated with an antistress effect, counteracting the effect induced by training in the rat. PMID:20482282

  7. Effects of diets supplemented with branched-chain amino acids on the performance and fatigue mechanisms of rats submitted to prolonged physical exercise.

    PubMed

    Falavigna, Gina; Alves de Araújo, Jonas; Rogero, Marcelo Macedo; Pires, Ivanir Santana de Oliveira; Pedrosa, Rogério Graça; Martins, Eivor; Alves de Castro, Inar; Tirapegui, Julio

    2012-11-01

    This study aimed to determine the effects of diets chronically supplemented with branched-chain amino acids (BCAA) on the fatigue mechanisms of trained rats. Thirty-six adult Wistar rats were trained for six weeks. The training protocol consisted of bouts of swimming exercise (one hour a day, five times a week, for six weeks). The animals received a control diet (C) (n = 12), a diet supplemented with 3.57% BCAA (S1) (n = 12), or a diet supplemented with 4.76% BCAA (S2) (n = 12). On the last day of the training protocol, half the animals in each group were sacrificed after one hour of swimming (1H), and the other half after a swimming exhaustion test (EX). Swimming time until exhaustion was increased by 37% in group S1 and reduced by 43% in group S2 compared to group C. Results indicate that the S1 diet had a beneficial effect on performance by sparing glycogen in the soleus muscle (p < 0.05) and by inducing a lower concentration of plasma ammonia, whereas the S2 diet had a negative effect on performance due to hyperammonemia (p < 0.05). The hypothalamic concentration of serotonin was not significantly different between the 1H and EX conditions. In conclusion, chronic BCAA supplementation led to increased performance in rats subjected to a swimming test to exhaustion. However, this is a dose-dependent effect, since chronic ingestion of elevated quantities of BCAA led to a reduction in performance. PMID:23201847

  8. The effect of rowing ergometry and resistive exercise on skeletal muscle structure and function during bed rest.

    PubMed

    Krainski, Felix; Hastings, Jeffrey L; Heinicke, Katja; Romain, Nadine; Pacini, Eric L; Snell, Peter G; Wyrick, Phil; Palmer, M Dean; Haller, Ronald G; Levine, Benjamin D

    2014-06-15

    Exposure to microgravity causes functional and structural impairment of skeletal muscle. Current exercise regimens are time-consuming and insufficiently effective; an integrated countermeasure is needed that addresses musculoskeletal along with cardiovascular health. High-intensity, short-duration rowing ergometry and supplemental resistive strength exercise may achieve these goals. Twenty-seven healthy volunteers completed 5 wk of head-down-tilt bed rest (HDBR): 18 were randomized to exercise, 9 remained sedentary. Exercise consisted of rowing ergometry 6 days/wk, including interval training, and supplemental strength training 2 days/wk. Measurements before and after HDBR and following reambulation included assessment of strength, skeletal muscle volume (MRI), and muscle metabolism (magnetic resonance spectroscopy); quadriceps muscle biopsies were obtained to assess muscle fiber types, capillarization, and oxidative capacity. Sedentary bed rest (BR) led to decreased muscle volume (quadriceps: -9 ± 4%, P < 0.001; plantar flexors: -19 ± 6%, P < 0.001). Exercise (ExBR) reduced atrophy in the quadriceps (-5 ± 4%, interaction P = 0.018) and calf muscle, although to a lesser degree (-14 ± 6%, interaction P = 0.076). Knee extensor and plantar flexor strength was impaired by BR (-14 ± 15%, P = 0.014 and -22 ± 7%, P = 0.001) but preserved by ExBR (-4 ± 13%, P = 0.238 and +13 ± 28%, P = 0.011). Metabolic capacity, as assessed by maximal O2 consumption, (31)P-MRS, and oxidative chain enzyme activity, was impaired in BR but stable or improved in ExBR. Reambulation reversed the negative impact of BR. High-intensity, short-duration rowing and supplemental strength training effectively preserved skeletal muscle function and structure while partially preventing atrophy in key antigravity muscles. Due to its integrated cardiovascular benefits, rowing ergometry could be a primary component of exercise prescriptions for astronauts or patients suffering from severe

  9. On the contribution of group III and IV muscle afferents to the circulatory response to rhythmic exercise in humans

    PubMed Central

    Amann, Markus; Runnels, Sean; Morgan, David E; Trinity, Joel D; Fjeldstad, Anette S; Wray, D Walter; Reese, Van R; Richardson, Russell S

    2011-01-01

    Abstract We investigated the role of skeletal muscle afferent feedback in circulatory control during rhythmic exercise in humans. Nine healthy males performed single leg knee-extensor exercise (15/30/45 watts, 3 min each) under both control conditions (Ctrl) and with lumbar intrathecal fentanyl impairing μ-opioid receptor-sensitive muscle afferents. Cardiac output and femoral blood flow were determined, and femoral arterial/venous blood samples were collected during the final minute of each workload. To rule out cephalad migration of fentanyl to the brainstem, we documented unchanged resting ventilatory responses to different levels of hypercapnia. There were no haemodynamic differences between conditions at rest. However, during exercise cardiac output was ∼20% lower with fentanyl blockade compared to control (P < 0.05), secondary to a 6% and 13% reduction in heart rate and stroke volume, respectively. Throughout exercise mean arterial pressure (MAP) was reduced by 7% (P < 0.01) which is likely to have contributed to the 15% fall in femoral blood flow. However, MAP was not completely responsible for this peripheral haemodynamic change as vascular conductance was also attenuated (∼9%). Evidence of increasing noradrenaline spillover (P = 0.09) implicated an elevation in sympathetic outflow in this response. The attenuated femoral blood flow during exercise with fentanyl was associated with a 17% reduction in leg O2 delivery (P < 0.01) and a concomitant rise in the arteriovenous O2 difference (4–9%), but leg O2 consumption remained 7–13% lower than control (P < 0.05). Our findings reveal an essential contribution of continuous muscle afferent feedback to ensure the appropriate haemodynamic and ultimately metabolic response to rhythmic exercise in humans. PMID:21646407

  10. Impact of resistance exercise during bed rest on skeletal muscle sarcopenia and myosin isoform distribution

    NASA Technical Reports Server (NTRS)

    Bamman, M. M.; Clarke, M. S.; Feeback, D. L.; Talmadge, R. J.; Stevens, B. R.; Lieberman, S. A.; Greenisen, M. C.

    1998-01-01

    Because resistance exercise (REx) and bed-rest unloading (BRU) are associated with opposing adaptations, our purpose was to test the efficacy of REx against the effects of 14 days of BRU on the knee-extensor muscle group. Sixteen healthy men were randomly assigned to no exercise (NoEx; n = 8) or REx (n = 8). REx performed five sets of leg press exercise with 80-85% of one repetition maximum (1 RM) every other day during BRU. Muscle samples were removed from the vastus lateralis muscle by percutaneous needle biopsy. Myofiber distribution was determined immunohistochemically with three monoclonal antibodies against myosin heavy chain (MHC) isoforms (I, IIa, IIx). MHC distribution was further assessed by quantitative gel electrophoresis. Dynamic 1-RM leg press and unilateral maximum voluntary isometric contraction (MVC) were determined. Maximal neural activation (root mean squared electromyogram) and rate of torque development (RTD) were measured during MVC. Reductions (P < 0.05) in type I (15%) and type II (17%) myofiber cross-sectional areas were found in NoEx but not in REx. Electrophoresis revealed no changes in MHC isoform distribution. The percentage of type IIx myofibers decreased (P < 0.05) in REx from 9 to 2% and did not change in NoEx. 1 RM was reduced (P < 0.05) by 9% in NoEx but was unchanged in REx. MVC fell by 15 and 13% in NoEx and REx, respectively. The agonist-to-antagonist root mean squared electromyogram ratio decreased (P < 0.05) 19% in REx. RTD slowed (P < 0.05) by 54% in NoEx only. Results indicate that REx prevented BRU-induced myofiber atrophy and also maintained training-specific strength. Unlike spaceflight, BRU did not induce shifts in myosin phenotype. The reported benefits of REx may prove useful in prescribing exercise for astronauts in microgravity.

  11. Associated decrements in rate of force development and neural drive after maximal eccentric exercise.

    PubMed

    Farup, J; Rahbek, S K; Bjerre, J; de Paoli, F; Vissing, K

    2016-05-01

    The present study investigated the changes in contractile rate of force development (RFD) and the neural drive following a single bout of eccentric exercise. Twenty-four subjects performed 15 × 10 maximal isokinetic eccentric knee extensor contractions. Prior to and at 24, 48, 72, 96, and 168 h during post-exercise recovery, isometric RFD (30, 50 100, and 200 ms), normalized RFD [1/6,1/2, and 2/3 of maximal voluntary contraction (MVC)] and rate of electromyography rise (RER; 30, 50, and 75 ms) were measured. RFD decreased by 28-42% peaking at 48 h (P < 0.01-P < 0.001) and remained depressed at 168 h (P < 0.05). Normalized RFD at 2/3 of MVC decreased by 22-39% (P < 0.01), peaked at 72 h and returned to baseline at 168 h. These changes in RFD were associated with a decrease in RER at 48 h-96 h (P < 0.05-P < 0.001). Accumulated changes (area under curve) revealed a greater relative decrease in accumulated RFD at 100 ms by -2727 ± 309 (%h; P < 0.05) and 200 ms by -3035 ± 271 (%h; P < 0.001) compared with MVC, which decreased, by -1956 ± 234 (%h). In conclusion, RFD and RER are both markedly reduced following a bout of maximal eccentric exercise. This association suggests that exercise-induced decrements in RFD can, in part, be explained decrements in neural drive. PMID:25944178

  12. The acute effects of flotation restricted environmental stimulation technique on recovery from maximal eccentric exercise.

    PubMed

    Morgan, Paul M; Salacinski, Amanda J; Stults-Kolehmainen, Matthew A

    2013-12-01

    Flotation restricted environmental stimulation technique (REST) involves compromising senses of sound, sight, and touch by creating a quiet dark environment. The individual lies supine in a tank of Epsom salt and water heated to roughly skin temperature (34-35° C). This study was performed to determine if a 1-hour flotation REST session would aid in the recovery process after maximal eccentric knee extensions and flexions. Twenty-four untrained male students (23.29 ± 2.1 years, 184.17 ± 6.85 cm, 85.16 ± 11.54 kg) participated in a randomized, repeated measures crossover study. The participants completed 2 exercise and recovery protocols: a 1-hour flotation REST session and a 1-hour seated control (passive recovery). After isometric muscle strength testing, participants were fatigued with eccentric isokinetic muscle contractions (50 repetitions at 60°·s) of the nondominant knee extensors and flexors. Blood lactate, blood glucose, heart rate, OMNI-rating of perceived exertion for resistance exercise (OMNI-RPE), perceived pain, muscle soreness, and isometric strength were collected before exercise, after treatment, and 24 and 48 hours later. A multivariate analysis of covariance found that treatment had a significant main effect on blood lactate, whereas subsequent univariate analyses of variance found statistical significance with the immediate posttreatment blood lactate measures. The results indicate that flotation REST appears to have a significant impact on blood lactate and perceived pain compared with a 1-hour passive recovery session in untrained healthy men. No difference was found between conditions for muscle strength, blood glucose, muscle soreness, heart rate, or OMNI-RPE. Flotation REST may be used for recreational and professional athletes to help reduce blood lactate levels after eccentric exercise. PMID:23478477

  13. Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training

    PubMed Central

    Owerkowicz, Tomasz; Cotter, Joshua A.; Haddad, Fadia; Yu, Alvin M.; Camilon, Marinelle L.; Hoang, Theresa; Jimenez, Daniel; Kreitenberg, Arthur; Tesch, Per A.; Caiozzo, Vincent J.; Adams, Gregory R.

    2016-01-01

    Background Although a number of exercise systems have been developed to mitigate the physiological deconditioning that occurs in microgravity, few have the capacity to positively impact multiple physiological systems and still meet the volume/mass requirements needed for missions beyond low earth orbit. The purpose of this study was to test the gravity-independent Multi-Mode Exercise Device (M-MED) for both resistance (RE) and aerobic (AE) training stimuli. Methods Eight men and nine women (mean age 22.0±0.4 years) completed five weeks of training on the M-MED: RE 4×7 squats two days a week, and AE 4×4-min rowing bouts at ~90% VO2max three days a week. Pre- and post-training data collection included an aerobic capacity test, MR imaging, strength testing, and vastus lateralis muscle biopsy. Results VO2max increased 8%, 3RM strength 18%, and quadriceps femoris cross-sectional area (CSA) 10%. Knee extensor strength increased at all isokinetic speeds tested. Subjects also demonstrated improved resistance to fatigue in knee extension. At the cellular and molecular level, the biopsy revealed increases in mixed myofiber CSA (13%), citrate synthase activity (26%), total RNA concentration (24%), IGF-I mRNA (77%), Type IIa Myosin Heavy Chain (MHC) mRNA (8%), and concomitant decrease in Type IIx MHC mRNA (−23%). None of the changes were gender-specific. Discussion Both the functional outcomes and biomarker changes indicate that a very low volume of M-MED exercise results in robust adaptation in the cardiovascular and musculoskeletal systems. The M-MED has the potential to provide a wide range of countermeasure exercises and should be considered for testing in ground-based spaceflight simulation. PMID:26802373

  14. Effects of ankle joint mobilization with movement and weight-bearing exercise on knee strength, ankle range of motion, and gait velocity in patients with stroke: a pilot study

    PubMed Central

    An, Chang-Man; Won, Jong-Im

    2016-01-01

    [Purpose] The purpose of this study was to investigate the effects of ankle joint mobilization with movement on knee strength, ankle range of motion, and gait velocity, compared with weight-bearing exercise in stroke patients. [Subjects and Methods] Thirty subjects with chronic stroke were divided into three groups: MWM (n = 12), WBE (n = 8), and control (n = 10). All groups attended physical therapy sessions 3 times a week for 5 weeks. Subjects in the MWM group performed mobilization with movement exercises, whilst participants in the WBE group performed weight-bearing exercises. Knee peak torque, ankle range of motion, and spatiotemporal gait parameters were evaluated before and after the interventions. [Results] Knee extensor peak torque increased significantly in both MWM and WBE groups. However, only the MWM group showed significant improvement in passive and active ankle range of motion and gait velocity, among the three groups. [Conclusion] Ankle joint mobilization with movement intervention is more effective than simple weight-bearing intervention in improving gait speed in stroke patients with limited ankle motion. PMID:27065565

  15. Quadriceps exercise intolerance in patients with chronic obstructive pulmonary disease: the potential role of altered skeletal muscle mitochondrial respiration.

    PubMed

    Gifford, Jayson R; Trinity, Joel D; Layec, Gwenael; Garten, Ryan S; Park, Song-Young; Rossman, Matthew J; Larsen, Steen; Dela, Flemming; Richardson, Russell S

    2015-10-15

    This study sought to determine if qualitative alterations in skeletal muscle mitochondrial respiration, associated with decreased mitochondrial efficiency, contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Using permeabilized muscle fibers from the vastus lateralis of 13 patients with COPD and 12 healthy controls, complex I (CI) and complex II (CII)-driven State 3 mitochondrial respiration were measured separately (State 3:CI and State 3:CII) and in combination (State 3:CI+CII). State 2 respiration was also measured. Exercise tolerance was assessed by knee extensor exercise (KE) time to fatigue. Per milligram of muscle, State 3:CI+CII and State 3:CI were reduced in COPD (P < 0.05), while State 3:CII and State 2 were not different between groups. To determine if this altered pattern of respiration represented qualitative changes in mitochondrial function, respiration states were examined as percentages of peak respiration (State 3:CI+CII), which revealed altered contributions from State 3:CI (Con 83.7 ± 3.4, COPD 72.1 ± 2.4%Peak, P < 0.05) and State 3:CII (Con 64.9 ± 3.2, COPD 79.5 ± 3.0%Peak, P < 0.05) respiration, but not State 2 respiration in COPD. Importantly, a diminished contribution of CI-driven respiration relative to the metabolically less-efficient CII-driven respiration (CI/CII) was also observed in COPD (Con 1.28 ± 0.09, COPD 0.81 ± 0.05, P < 0.05), which was related to exercise tolerance of the patients (r = 0.64, P < 0.05). Overall, this study indicates that COPD is associated with qualitative alterations in skeletal muscle mitochondria that affect the contribution of CI and CII-driven respiration, which potentially contributes to the exercise intolerance associated with this disease. PMID:26272320

  16. Treadmill exercise within lower body negative pressure protects leg lean tissue mass and extensor strength and endurance during bed rest.

    PubMed

    Schneider, Suzanne M; Lee, Stuart M C; Feiveson, Alan H; Watenpaugh, Donald E; Macias, Brandon R; Hargens, Alan R

    2016-08-01

    Leg muscle mass and strength are decreased during reduced activity and non-weight-bearing conditions such as bed rest (BR) and spaceflight. Supine treadmill exercise within lower body negative pressure (LBNPEX) provides full-body weight loading during BR and may prevent muscle deconditioning. We hypothesized that a 40-min interval exercise protocol performed against LBNPEX 6 days week(-1) would attenuate losses in leg lean mass (LLM), strength, and endurance during 6° head-down tilt BR, with similar benefits for men and women. Fifteen pairs of healthy monozygous twins (8 male and 7 female pairs) completed 30 days of BR with one sibling of each twin pair assigned randomly as the non-exercise control (CON) and the other twin as the exercise subject (EX). Before and after BR, LLM and isokinetic leg strength and endurance were measured. Mean knee and ankle extensor and flexor strength and endurance and LLM decreased from pre- to post-BR in the male CON subjects (P < 0.01), but knee extensor strength and endurance, ankle extensor strength, and LLM were maintained in the male EX subjects. In contrast, no pre- to post-BR changes were significant in the female subjects, either CON or EX, likely due to their lower pre-BR values. Importantly, the LBNPEX countermeasure prevents or attenuates declines in LLM as well as extensor leg strength and endurance. Individuals who are stronger, have higher levels of muscular endurance, and/or have greater LLM are likely to experience greater losses during BR than those who are less fit. PMID:27495299

  17. Evidence of skeletal muscle metabolic reserve during whole body exercise in patients with chronic obstructive pulmonary disease.

    PubMed

    Richardson, R S; Sheldon, J; Poole, D C; Hopkins, S R; Ries, A L; Wagner, P D

    1999-03-01

    When freed from central cardiorespiratory limitations, healthy human skeletal muscle has exhibited a significant metabolic reserve. We studied the existence of this reserve in 10 severely compromised (FEV1 = 0.97 +/- SE 0.01) patients with chronic obstructive pulmonary disease (COPD). To manipulate O2 supply and O2 demand in locomotor and respiratory muscles, subjects performed both maximal conventional two-legged cycle ergometry (large muscle mass) and single-leg knee extensor exercise (KE, small muscle mass) while breathing room air (RA), 100% O2, and 79% helium + 21% O2 (HeO2). With each gas mixture, peak ventilation, peak heart rate, and perceived breathlessness were lower in KE than cycle exercise (p < 0. 05). Arterial O2 saturation and maximal work capacity increased in both exercise modalities while subjects breathed 100% O2 (work: +10% bike, +25% KE, p < 0.05). HeO2 increased maximal work capacity on the cycle (+14%, p < 0.05) but had no effect on KE. HeO2 resulted in the greatest maximum minute ventilation in both bike and KE (p < 0. 05) but had no effect on arterial O2 saturation. Thus, a skeletal muscle metabolic reserve in these patients with COPD is evidenced by: (1) greater muscle mass specific work in KE; (2) greater work rates with higher fraction of inspired oxygen (FIO2); (3) an even greater effect of FIO2 during KE (i.e., when the lungs are less challenged); and (4) the positive effect of HeO2 on bicycle work rate. This skeletal muscle metabolic reserve suggests that reduced whole body exercise capacity in COPD is the result of central restraints rather than peripheral skeletal muscle dysfunction, while the beneficial effect of 100% O2 (with no change in maximum ventilation) suggests that the respiratory system is not the sole constraint to oxygen consumption. PMID:10051266

  18. The comparison of cold-water immersion and cold air therapy on maximal cycling performance and recovery markers following strength exercises

    PubMed Central

    Hayter, Kane J.; Schumann, Moritz; Deakin, Glen B.

    2016-01-01

    This study examined the effects of cold-water immersion (CWI) and cold air therapy (CAT) on maximal cycling performance (i.e. anaerobic power) and markers of muscle damage following a strength training session. Twenty endurance-trained but strength-untrained male (n = 10) and female (n = 10) participants were randomised into either: CWI (15 min in 14 °C water to iliac crest) or CAT (15 min in 14 °C air) immediately following strength training (i.e. 3 sets of leg press, leg extensions and leg curls at 6 repetition maximum, respectively). Creatine kinase, muscle soreness and fatigue, isometric knee extensor and flexor torque and cycling anaerobic power were measured prior to, immediately after and at 24 (T24), 48 (T48) and 72 (T72) h post-strength exercises. No significant differences were found between treatments for any of the measured variables (p > 0.05). However, trends suggested recovery was greater in CWI than CAT for cycling anaerobic power at T24 (10% ± 2%, ES = 0.90), T48 (8% ± 2%, ES = 0.64) and T72 (8% ± 7%, ES = 0.76). The findings suggest the combination of hydrostatic pressure and cold temperature may be favourable for recovery from strength training rather than cold temperature alone. PMID:27069791

  19. Exhausting stretch-shortening cycle (SSC) exercise causes greater impairment in SSC performance than in pure concentric performance.

    PubMed

    Horita, T; Komi, P V; Hämäläinen, I; Avela, J

    2003-02-01

    The purpose of the present study was to investigate the fatigue effect of repeated exhaustive stretch-shortening cycle (SSC) exercise on concentric muscle function. Ten healthy male subjects performed SSC exercise [92 (30) jumps] on a special sledge apparatus. Exhaustion occurred on average within 3 min. A squat jump (SJ) test utilizing a concentric-only action was performed immediately before and after the SSC exercise, and then 10 min, 20 min, 2 days and 4 days later. In addition, a drop jump (DJ) test using an SSC was also performed immediately before and 20 min after the SSC exercise, and 2 days and 4 days later. During jump tests, lower limb joint moment, power, and work contributions were analyzed by using the kinetic and kinematic data. The fatigue exercise was characterized by a relatively high blood lactate concentration [7.2 (0.8) mmol x l(-1)] and a 2-day delayed increase in serum creatine kinase activity [486 (300) U x l(-1)]. SJ performance decreased markedly immediately after the SSC exercise (P<0.05) and then recovered within 10 min. In contrast, DJ performance and knee joint contribution showed a delayed decrease 2 days after the SSC exercise bout. The surface electromyographic (EMG) activity of the lower limb muscles showed no obvious change in the SJ in comparison to the DJ, although in the latter there was a delayed decrease of knee extensor EMG during the pre-activation and braking phases. The results suggest that isolated concentric muscle function is affected mainly by acute metabolic fatigue after SSC exercise. During a follow-up period after the exercise, changes in hip and knee joint contribution in SJ showed a different recovery pattern compared to those in eccentric DJ. It could be suggested that exhaustive SSC exercise would mainly influence the relative power-work balance between the hip and knee joints during the eccentric phase of SSC. Thus different motor control strategies may account for the distinctive fatigue responses observed

  20. Erythrocyte-dependent regulation of human skeletal muscle blood flow: role of varied oxyhemoglobin and exercise on nitrite, S-nitrosohemoglobin, and ATP.

    PubMed

    Dufour, Stéphane P; Patel, Rakesh P; Brandon, Angela; Teng, Xinjun; Pearson, James; Barker, Horace; Ali, Leena; Yuen, Ada H Y; Smolenski, Ryszard T; González-Alonso, José

    2010-12-01

    The erythrocyte is proposed to play a key role in the control of local tissue perfusion via three O(2)-dependent signaling mechanisms: 1) reduction of circulating nitrite to vasoactive NO, 2) S-nitrosohemoglobin (SNO-Hb)-dependent vasodilatation, and 3) release of the vasodilator and sympatholytic ATP; however, their relative roles in vivo remain unclear. Here we evaluated each mechanism to gain insight into their roles in the regulation of human skeletal muscle blood flow during hypoxia and hyperoxia at rest and during exercise. Arterial and femoral venous hemoglobin O(2) saturation (O(2)Hb), plasma and erythrocyte NO and ATP metabolites, and leg and systemic hemodynamics were measured in 10 healthy males exposed to graded hypoxia, normoxia, and graded hyperoxia both at rest and during submaximal one-legged knee-extensor exercise. At rest, leg blood flow and NO and ATP metabolites in plasma and erythrocytes remained unchanged despite large alterations in O(2)Hb. During exercise, however, leg and systemic perfusion and vascular conductance increased in direct proportion to decreases in arterial and venous O(2)Hb (r(2) = 0.86-0.98; P = 0.01), decreases in venous plasma nitrite (r(2) = 0.93; P < 0.01), increases in venous erythrocyte nitroso species (r(2) = 0.74; P < 0.05), and to a lesser extent increases in erythrocyte SNO (r(2) = 0.59; P = 0.07). No relationship was observed with plasma ATP (r(2) = 0.01; P = 0.99) or its degradation compounds. These in vivo data indicate that, during low-intensity exercise and hypoxic stress, but not hypoxic stress alone, plasma nitrite consumption and formation of erythrocyte nitroso species are associated with limb vasodilatation and increased blood flow in the human skeletal muscle vasculature. PMID:20852046

  1. Erythrocyte-dependent regulation of human skeletal muscle blood flow: role of varied oxyhemoglobin and exercise on nitrite, S-nitrosohemoglobin, and ATP

    PubMed Central

    Patel, Rakesh P.; Brandon, Angela; Teng, Xinjun; Pearson, James; Barker, Horace; Ali, Leena; Yuen, Ada H. Y.; Smolenski, Ryszard T.; González-Alonso, José

    2010-01-01

    The erythrocyte is proposed to play a key role in the control of local tissue perfusion via three O2-dependent signaling mechanisms: 1) reduction of circulating nitrite to vasoactive NO, 2) S-nitrosohemoglobin (SNO-Hb)-dependent vasodilatation, and 3) release of the vasodilator and sympatholytic ATP; however, their relative roles in vivo remain unclear. Here we evaluated each mechanism to gain insight into their roles in the regulation of human skeletal muscle blood flow during hypoxia and hyperoxia at rest and during exercise. Arterial and femoral venous hemoglobin O2 saturation (O2Hb), plasma and erythrocyte NO and ATP metabolites, and leg and systemic hemodynamics were measured in 10 healthy males exposed to graded hypoxia, normoxia, and graded hyperoxia both at rest and during submaximal one-legged knee-extensor exercise. At rest, leg blood flow and NO and ATP metabolites in plasma and erythrocytes remained unchanged despite large alterations in O2Hb. During exercise, however, leg and systemic perfusion and vascular conductance increased in direct proportion to decreases in arterial and venous O2Hb (r2 = 0.86–0.98; P = 0.01), decreases in venous plasma nitrite (r2 = 0.93; P < 0.01), increases in venous erythrocyte nitroso species (r2 = 0.74; P < 0.05), and to a lesser extent increases in erythrocyte SNO (r2 = 0.59; P = 0.07). No relationship was observed with plasma ATP (r2 = 0.01; P = 0.99) or its degradation compounds. These in vivo data indicate that, during low-intensity exercise and hypoxic stress, but not hypoxic stress alone, plasma nitrite consumption and formation of erythrocyte nitroso species are associated with limb vasodilatation and increased blood flow in the human skeletal muscle vasculature. PMID:20852046

  2. Skeletal muscle blood flow and oxygen uptake at rest and during exercise in humans: a pet study with nitric oxide and cyclooxygenase inhibition.

    PubMed

    Heinonen, Ilkka; Ilkka, Heinonen; Saltin, Bengt; Bengt, Saltin; Kemppainen, Jukka; Jukka, Kemppainen; Sipilä, Hannu T; Oikonen, Vesa; Vesa, Oikonen; Nuutila, Pirjo; Pirjo, Nuutila; Knuuti, Juhani; Juhani, Knuuti; Kalliokoski, Kari; Kari, Kalliokoski; Hellsten, Ylva; Ylva, Hellsten

    2011-04-01

    The aim of the present study was to determine the effect of nitric oxide and prostanoids on microcirculation and oxygen uptake, specifically in the active skeletal muscle by use of positron emission tomography (PET). Healthy males performed three 5-min bouts of light knee-extensor exercise. Skeletal muscle blood flow and oxygen uptake were measured at rest and during the exercise using PET with H(2)O(15) and (15)O(2) during: 1) control conditions; 2) nitric oxide synthase (NOS) inhibition by arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA), and 3) combined NOS and cyclooxygenase (COX) inhibition by arterial infusion of L-NMMA and indomethacin. At rest, inhibition of NOS alone and in combination with indomethacin reduced (P < 0.05) muscle blood flow. NOS inhibition increased (P < 0.05) limb oxygen extraction fraction (OEF) more than the reduction in muscle blood flow, resulting in an ∼20% increase (P < 0.05) in resting muscle oxygen consumption. During exercise, muscle blood flow and oxygen uptake were not altered with NOS inhibition, whereas muscle OEF was increased (P < 0.05). NOS and COX inhibition reduced (P < 0.05) blood flow in working quadriceps femoris muscle by 13%, whereas muscle OEF and oxygen uptake were enhanced by 51 and 30%, respectively. In conclusion, by specifically measuring blood flow and oxygen uptake by the use of PET instead of whole limb measurements, the present study shows for the first time in humans that inhibition of NO formation enhances resting muscle oxygen uptake and that combined inhibition of NOS and COX during exercise increases muscle oxygen uptake. PMID:21257921

  3. Exercise Induced Cardiac Fatigue Following Prolonged Exercise in Road Cyclists

    ERIC Educational Resources Information Center

    Wyatt, Frank; Pawar, Ganesh; Kilgore, Lon

    2011-01-01

    The purpose of this study was to examine cardiac function following a 100-mile ride in high ambient temperatures by healthy, competitive cyclists. Methods: Subjects were six (n=6) competitive cyclists racing in a 100-mile road race. Measures (pre/post) included: body mass (kg); E:A ratio (ventricular compliance); stroke volume (ml); ejection…

  4. Effects of Constant and Doublet Frequency Electrical Stimulation Patterns on Force Production of Knee Extensor Muscles

    PubMed Central

    Cometti, Carole; Babault, Nicolas; Deley, Gaëlle

    2016-01-01

    This study compared knee extensors’ neuromuscular fatigue in response to two 30-minute stimulation patterns: constant frequency train (CFT) and doublet frequency train (DFT). Fifteen men underwent two separate sessions corresponding to each pattern. Measurements included torque evoked by each contraction and maximal voluntary contractions (MVC) measured before and immediately after the stimulation sessions. In addition, activation level and torque evoked during doublets (Pd) and tetanic contractions at 80-Hz (P80) and 20-Hz (P20) were determined in six subjects. Results indicated greater mean torque during the DFT stimulation session as compared with CFT. But, no difference was obtained between the two stimulation patterns for MVC and evoked torque decreases. Measurements conducted in the subgroup depicted a significant reduction of Pd, P20 and P80. Statistical analyses also revealed bigger P20 immediate reductions after CFT than after DFT. We concluded that DFT could be a useful stimulation pattern to produce and maintain greater force with quite similar fatigue than CFT. PMID:27167066

  5. SIMULTANEOUS BILATERAL TEAR OF THE KNEE EXTENSOR MECHANISM IN A PRE-ADOLESCENT: CASE REPORT

    PubMed Central

    Albuquerque, Rodrigo Pires; Giordano, Vincenzo; Albuquerque, Maria Isabel Pires; Carvalho, Antonio Carlos Pires; do Amaral, Ney Pecegueiro; Barretto, João Maurício

    2015-01-01

    Unilateral tearing of a patellar tendon and a contralateral sleeve fracture in a pre-adolescent are rare lesions. We report a case in which a pre-adolescent sustained a fall while jumping during a soccer match. No predisposing risk factors were identified. The injuries were treated with surgical repairs and transosseous suturing. The aim of this study was to present a case of spontaneous concurrent tearing of the extensor mechanism of the knee in a pre-adolescent. PMID:27047882

  6. Knee Extensor and Flexor Torque Development with Concentric and Eccentric Isokinetic Training

    ERIC Educational Resources Information Center

    Miller, Larry E.; Pierson, Lee M.; Nickols-Richardson, Sharon M.; Wootten, David F.; Selmon, Serah E.; Ramp, Warren K.; Herbert, William G.

    2006-01-01

    This study assessed muscular torque and rate of torque development following concentric (CON) or eccentric (ECC) isokinetic training. Thirty-eight women were randomly assigned to either CON or ECC training groups. Training consisted of knee extension and flexion of the nondominant leg three times per week for 20 weeks (SD = 1). Eccentric training…

  7. PROTECTION DEVICE ON THE REPAIR OF RUPTURES OF KNEE EXTENSOR MECHANISM

    PubMed Central

    Arguello Frutos, Carlos Francisco; Arbix Camargo, Osmar Pedro; Severino, Nilson Roberto; Leite Cury, Ricardo de Paula; de Oliveira, Victor Marques; Aihara, Tatsuo; Avakian, Roger

    2015-01-01

    To evaluate results obtained using the protection device technique for osteosintesis or suture of extensor mechanism lesions. Material and Methods: The authors reviewed 18 charts of patients submitted to protection device technique due to traumatic lesion of extensor mechanism that had occurred between the anterior tibial tuberosity and the apical portion of patella. Age ranged from 22 to 69 years, with a mean of 44 years. Male patients prevailed, with 67% of the cases. The most affected spot was, in 83% of the cases, the apical distal third. A protocol was created to collect data, listing the patients and the clinical history from their medical records. Results: The authors observed consolidation of the patella fracture in all 17 patients, and cicatrization of the patellar ligament in one patient. Pain was described in four patients. There were no complications related to the procedure. Conclusion: The protection device showed to be efficient when used in surgical treatment of lesions between the apical patella and the anterior tibial tuberosity, providing active and passive mobility in the early postoperative time. PMID:26998454

  8. Exercise: Benefits of Exercise

    MedlinePlus Videos and Cool Tools

    ... show that people with arthritis, heart disease, or diabetes benefit from regular exercise. Exercise also helps people ... or difficulty walking. To learn about exercise and diabetes, see "Exercise and Type 2 Diabetes" from Go4Life®, ...

  9. Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men

    PubMed Central

    2012-01-01

    Background Increased amino acid availability stimulates muscle protein synthesis, however, aged muscle appears less responsive to the anabolic effects of amino acids when compared to the young. We aimed to compare changes in myofibrillar protein synthesis (MPS) in elderly men at rest and after resistance exercise following ingestion of different doses of soy protein and compare the responses to those we previously observed with ingestion of whey protein isolate. Methods Thirty elderly men (age 71 ± 5 y) completed a bout of unilateral knee-extensor resistance exercise prior to ingesting no protein (0 g), or either 20 g or 40 g of soy protein isolate (0, S20, and S40 respectively). We compared these responses to previous responses from similar aged men who had ingested 20 g and 40 g of whey protein isolate (W20 and W40). A primed constant infusion of L-[1-13 C]leucine and L-[ring-13 C6]phenylalanine and skeletal muscle biopsies were used to measure whole-body leucine oxidation and MPS over 4 h post-protein consumption in both exercised and non-exercised legs. Results Whole-body leucine oxidation increased with protein ingestion and was significantly greater for S20 vs. W20 (P = 0.003). Rates of MPS for S20 were less than W20 (P = 0.02) and not different from 0 g (P = 0.41) in both exercised and non-exercised leg muscles. For S40, MPS was also reduced compared with W40 under both rested and post-exercise conditions (both P < 0.005); however S40 increased MPS greater than 0 g under post-exercise conditions (P = 0.04). Conclusions The relationship between protein intake and MPS is both dose and protein source-dependent, with isolated soy showing a reduced ability, as compared to isolated whey protein, to stimulate MPS under both rested and post-exercise conditions. These differences may relate to the lower postprandial leucinemia and greater rates of amino acid oxidation following ingestion of soy versus whey protein. PMID

  10. Inhibition of nitric oxide and prostaglandins, but not endothelial-derived hyperpolarizing factors, reduces blood flow and aerobic energy turnover in the exercising human leg.

    PubMed

    Mortensen, Stefan P; González-Alonso, José; Damsgaard, Rasmus; Saltin, Bengt; Hellsten, Ylva

    2007-06-01

    Prostaglandins, nitric oxide (NO) and endothelial-derived hyperpolarizing factors (EDHFs) are substances that have been proposed to be involved in the regulation of skeletal muscle blood flow during physical activity. We measured haemodynamics, plasma ATP at rest and during one-legged knee-extensor exercise (19 +/- 1 W) in nine healthy subjects with and without intra-arterial infusion of indomethacin (Indo; 621 +/- 17 microg min(-1)), Indo + N(G)-monomethyl-L-arginine (L-NMMA; 12.4 +/- 0.3 mg min(-1)) (double blockade) and Indo + L-NMMA + tetraethylammonium chloride (TEA; 12.4 +/- 0.3 mg min(-1)) (triple blockade). Double and triple blockade lowered leg blood flow (LBF) at rest (P<0.05), while it remained unchanged with Indo. During exercise, LBF and vascular conductance were 2.54 +/- 0.10 l min(-1) and 25 +/- 1 mmHg, respectively, in control and they were lower with double (33 +/- 3 and 36 +/- 4%, respectively) and triple (26 +/- 4 and 28 +/- 3%, respectively) blockade (P<0.05), while there was no difference with Indo. The lower LBF and vascular conductance with double and triple blockade occurred in parallel with a lower O(2) delivery, cardiac output, heart rate and plasma [noradrenaline] (P<0.05), while blood pressure remained unchanged and O(2) extraction and femoral venous plasma [ATP] increased. Despite the increased O(2) extraction, leg was 13 and 17% (triple and double blockade, respectively) lower than control in parallel to a lower femoral venous temperature and lactate release (P<0.05). These results suggest that NO and prostaglandins play important roles in skeletal muscle blood flow regulation during moderate intensity exercise and that EDHFs do not compensate for the impaired formation of NO and prostaglandins. Moreover, inhibition of NO and prostaglandin formation is associated with a lower aerobic energy turnover and increased concentration of vasoactive ATP in plasma. PMID:17347273

  11. Isolated quadriceps training increases maximal exercise capacity in chronic heart failure: The role of skeletal muscle convective and diffusive oxygen transport

    PubMed Central

    Esposito, Fabio; Reese, Van; Shabetai, Ralph; Wagner, Peter D.; Richardson, Russell S.

    2011-01-01

    Objectives This study sought to elucidate the mechanisms responsible for the benefits of small muscle mass exercise training in patients with chronic heart failure (CHF). Background How central cardiorespiratory and/or peripheral skeletal muscle factors are altered with small muscle mass training in CHF is unknown. Methods We studied muscle structure and oxygen (O2) transport and metabolism at maximal cycle (whole body) and knee-extensor exercise (KE) (small muscle mass) in 6 healthy controls and 6 patients with CHF who then performed 8 weeks of KE training (both legs, separately) and repeated these assessments. Results Pre-training cycling and KE peak leg O2 uptake (VO2peak) were ~17% and ~15% lower, respectively, in the patients compared to controls. Structurally, KE training increased quadriceps muscle capillarity and mitochondrial density by ~21 and ~25%, respectively. Functionally, despite not altering maximal cardiac output, KE training increased maximal O2 delivery (~54%), arterial-venous O2 (a–v O2) difference (~10%), and muscle O2 diffusive conductance (DMO2) (~39%) (assessed during KE), thereby increasing single leg VO2peak by ~53%, to a level exceeding that of the untrained controls. Post-training, during maximal cycling, O2 delivery (~40%), a–v O2 difference (~15%), and DMO2 (~52%) all increased, yielding an increase in VO2peak of ~40%, matching the controls. Conclusions In the face of continued central limitations, clear improvements in muscle structure, peripheral convective and diffusive O2 transport, and subsequently O2 utilization support the efficacy of local skeletal muscle training as a powerful approach to combat exercise intolerance in CHF. PMID:21920265

  12. Local temperature-sensitive mechanisms are important mediators of limb tissue hyperemia in the heat-stressed human at rest and during small muscle mass exercise.

    PubMed

    Chiesa, Scott T; Trangmar, Steven J; Kalsi, Kameljit K; Rakobowchuk, Mark; Banker, Devendar S; Lotlikar, Makrand D; Ali, Leena; González-Alonso, José

    2015-07-15

    Limb tissue and systemic blood flow increases with heat stress, but the underlying mechanisms remain poorly understood. Here, we tested the hypothesis that heat stress-induced increases in limb tissue perfusion are primarily mediated by local temperature-sensitive mechanisms. Leg and systemic temperatures and hemodynamics were measured at rest and during incremental single-legged knee extensor exercise in 15 males exposed to 1 h of either systemic passive heat-stress with simultaneous cooling of a single leg (n = 8) or isolated leg heating or cooling (n = 7). Systemic heat stress increased core, skin and heated leg blood temperatures (Tb), cardiac output, and heated leg blood flow (LBF; 0.6 ± 0.1 l/min; P < 0.05). In the cooled leg, however, LBF remained unchanged throughout (P > 0.05). Increased heated leg deep tissue blood flow was closely related to Tb (R(2) = 0.50; P < 0.01), which is partly attributed to increases in tissue V̇O2 (R(2) = 0.55; P < 0.01) accompanying elevations in total leg glucose uptake (P < 0.05). During isolated limb heating and cooling, LBFs were equivalent to those found during systemic heat stress (P > 0.05), despite unchanged systemic temperatures and hemodynamics. During incremental exercise, heated LBF was consistently maintained ∼ 0.6 l/min higher than that in the cooled leg (P < 0.01), with LBF and vascular conductance in both legs showing a strong correlation with their respective local Tb (R(2) = 0.85 and 0.95, P < 0.05). We conclude that local temperature-sensitive mechanisms are important mediators in limb tissue perfusion regulation both at rest and during small-muscle mass exercise in hyperthermic humans. PMID:25934093

  13. Positron emission tomography detects greater blood flow and less blood flow heterogeneity in the exercising skeletal muscles of old compared with young men during fatiguing contractions

    PubMed Central

    Rudroff, Thorsten; Weissman, Jessica A; Bucci, Marco; Seppänen, Marko; Kaskinoro, Kimmo; Heinonen, Ilkka; Kalliokoski, Kari K

    2014-01-01

    The purpose of this study was to investigate blood flow and its heterogeneity within and among the knee muscles in five young (26 ± 6 years) and five old (77 ± 6 years) healthy men with similar levels of physical activity while they performed two types of submaximal fatiguing isometric contraction that required either force or position control. Positron emission tomography (PET) and [15O]-H2O were used to determine blood flow at 2 min (beginning) and 12 min (end) after the start of the tasks. Young and old men had similar maximal forces and endurance times for the fatiguing tasks. Although muscle volumes were lower in the older subjects, total muscle blood flow was similar in both groups (young men: 25.8 ± 12.6 ml min−1; old men: 25.1 ± 15.4 ml min−1; age main effect, P = 0.77) as blood flow per unit mass of muscle in the exercising knee extensors was greater in the older (12.5 ± 6.2 ml min−1 (100 g)−1) than the younger (8.6 ± 3.6 ml min−1 (100 g)−1) men (age main effect, P = 0.001). Further, blood flow heterogeneity in the exercising knee extensors was significantly lower in the older (56 ± 27%) than the younger (67 ± 34%) men. Together, these data show that although skeletal muscles are smaller in older subjects, based on the intact neural drive to the muscle and the greater, less heterogeneous blood flow per gram of muscle, old fit muscle achieves adequate exercise hyperaemia. Key points The results of previous studies that attempted to demonstrate the effects of ageing on skeletal muscle blood flow are controversial because these studies used indirect assessments of skeletal muscle blood flow obtained via whole limb blood flow measurements that provide no information on the distribution of blood flow within particular muscles. We used positron emission tomography to measure blood flow per gram of muscle in old and young men with similar levels of physical activity

  14. Changes in Indirect Markers of Muscle Damage and Tendons After Daily Drop Jumping Exercise with Rapid Load Increase

    PubMed Central

    Paleckis, Vidas; Mickevičius, Mantas; Snieckus, Audrius; Streckis, Vytautas; Pääsuke, Mati; Rutkauskas, Saulius; Steponavičiūtė, Rasa; Skurvydas, Albertas; Kamandulis, Sigitas

    2015-01-01

    The aim of this study was to assess changes in indirect markers of muscle damage and type I collagen degradation, as well as, patellar and Achilles tendon morphological differences during nine daily drop-jumps sessions with constant load alternated with rapid increases in load to test the hypothesis that frequent drop-jump training results in negative muscular and tendon adaptation. Young men (n = 9) performed daily drop jump workouts with progression every 3 days in terms of number of jumps, platform height and squat amplitude. Voluntary and electrically evoked knee extensor torque, muscle soreness, blood plasma creatine kinase (CK) activity and carboxyterminal cross-linked telopeptide (ICTP), patellar and Achilles tendon thickness and cross-sectional area (CSA) were assessed at different time points during the training period and again on days 1, 3, 10 and 17 after the training. The findings were as follows: (1) steady decline in maximal muscle strength with major recovery within 24 hours after the first six daily training sessions; (2) larger decline in electrically induced muscle torque and prolonged recovery during last three training sessions; (3) increase in patellar and Achilles tendons CSA without change in thickness towards the end of training period; (4) increase in jump height but not in muscle strength after whole training period. Our findings suggest that frequent drop-jump sessions with constant load alternated with rapid increases in load do not induce severe muscle damage or major changes in tendons, nonetheless, this type of loading is not advisable for muscle strength improvement. Key points Frequent drop jump training induces activation mode dependent muscle torque depression late in the training period. No significant changes in the thickness of patellar and Achilles tendons are observed during frequent training, while CSA increases towards the end of training period. Longitudinal effect for jump height but not for muscle strength is evident

  15. Piroxicam fails to reduce myocellular enzyme leakage and delayed onset muscle soreness induced by isokinetic eccentric exercise

    PubMed Central

    Croisier, J-L.; Monfils, T.; Deby-Dupon, G.; Fafchamps, M.; Venneman, I.; Crielaard, J-M.; Juchmès-Ferir, A.; Lhermerout, C.; Lamy, M.; Deby, C.

    1996-01-01

    To test the hypothesis that delayed onset muscular soreness (DOMS) following intense eccentric muscle contraction could be due to increased production of prostaglandin E2 (PGE2), ten healthy male subjects were studied. Using a double-blind randomized crossover design, each subject performed two isokinetic tests separated by a period of at least 6 weeks: once with placebo, and once with piroxicam (Feldene®). They were given one capsule containing either placebo or piroxicam (20 mg) per day for 6 days with initial doses given starting 3 days prior to isokinetic testing. Exercise consisted of eight stages of five maximal contractions of the knee extensor and flexor muscle groups of both legs separated by 1 min rest phases, on a Kin Trex device at 60°/s angular velocity. The subjective presence and intensity of DOMS were evaluated using a visual analogue scale immediately after, and 24 and 48 h after each test. The mean plasma concentration of PGE2 measured at rest and after exercise was significantly lower in the group treated with piroxicam (p < 0.05). However, statistical analysis (two-way ANOVA test) revealed that exercise did not cause any significant change of mean plasma PGE2 over time in either of the two groups. Eccentric work was followed by severe muscle pain in extensor and flexor muscle groups. Maximal soreness was noted 48 h postexercise. Serum creatine kinase activity and the serum concentration of myoglobin increased significantly, and reached peak values 48 h after exercise in both experimental conditions (p < 0.001). By paired t-test, it appeared that there were no significant differences in the serum levels of these two markers of muscle damage between the two groups at any time point. We conclude that: (1) oral administration of piroxicam fails to reduce muscle damage and DOMS caused by strenuous eccentric exercise; and (2) the hypothetical role of increased PGE2 production in eccentric exercise-induced muscle damage, DOMS, and reduced isokinetic

  16. Changes in the human blood coagulating system during prolonged hypokinesia

    NASA Technical Reports Server (NTRS)

    Filatova, L. M.; Anashkin, O. D.

    1978-01-01

    Changes in the coagulating system of the blood were studied in six subjects during prolonged hypokinesia. Thrombogenic properties of the blood rose in all cases on the 8th day. These changes are explained by stress reaction due to unusual conditions for a healthy person. Changes in the blood coagulating system in the group subjected to physical exercise and without it ran a practically parallel course. Apparently physical exercise is insufficient to prevent such changes that appear in the coagulating system of the blood during prolonged hypokinesia.

  17. Aerobic exercise training improves whole muscle and single myofiber size and function in older women

    PubMed Central

    Konopka, Adam R.; Douglass, Matthew D.; Minchev, Kiril; Kaminsky, Leonard A.; Trappe, Todd A.; Trappe, Scott

    2009-01-01

    To comprehensively assess the influence of aerobic training on muscle size and function, we examined seven older women (71 ± 2 yr) before and after 12 wk of cycle ergometer training. The training program increased (P < 0.05) aerobic capacity by 30 ± 6%. Quadriceps muscle volume, determined by magnetic resonance imaging (MRI), was 12 ± 2% greater (P < 0.05) after training and knee extensor power increased 55 ± 7% (P < 0.05). Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of individual slow (MHC I) and fast (MHC IIa) myofibers, myosin light chain (MLC) composition, and muscle protein concentration. Aerobic training increased (P < 0.05) MHC I fiber size 16 ± 5%, while MHC IIa fiber size was unchanged. MHC I peak power was elevated 21 ± 8% (P < 0.05) after training, while MHC IIa peak power was unaltered. Peak force (Po) was unchanged in both fiber types, while normalized force (Po/cross-sectional area) was 10% lower (P < 0.05) for both MHC I and MHC IIa fibers after training. The decrease in normalized force was likely related to a reduction (P < 0.05) in myofibrillar protein concentration after training. In the absence of an increase in Po, the increase in MHC I peak power was mediated through an increased (P < 0.05) maximum contraction velocity (Vo) of MHC I fibers only. The relative proportion of MLC1s (Pre: 0.62 ± 0.01; Post: 0.58 ± 0.01) was lower (P < 0.05) in MHC I myofibers after training, while no differences were present for MLC2s and MLC3f isoforms. These data indicate that aerobic exercise training improves muscle function through remodeling the contractile properties at the myofiber level, in addition to pronounced muscle hypertrophy. Progressive aerobic exercise training should be considered a viable exercise modality to combat sarcopenia in the elderly population. PMID:19692660

  18. [Prolonged or chronic fatigue of unknown origin].

    PubMed

    Favrat, Bernard; Guessous, Idris; Gonthier, Ariane; Cornuz, Jacques

    2015-04-22

    Although prolonged or chronic fatigue is a very common complaint in primary care medicine, a biomedical obvious cause is often not found. In such a case, for women between 18 and 50 years with a ferritin level of less than 50 µg/l in the absence of anaemia, an iron supplementation may be associated with an improvement in fatigue. Appropriate treatment is also important for depression, anxiety or insomnia. In other cases, the approach is essentially non-pharmacological in the form of lifestyle advice, empathy and cognitive behavioural therapy as well as progressive and adapted physical exercises. PMID:26072601

  19. Preservation of human performance capacity under prolonged space flight conditions

    NASA Technical Reports Server (NTRS)

    Yeremin, A. V.; Bogdashevskiy, R. M.; Baburin, Y. F.

    1975-01-01

    Prophylactic measures directed toward preservation of health and maintenance of the performance ability of a man during prolonged space flight stress center on the selection of optimum work and rest cycles, physical exercises, the use of pharmacological agents, conditioning of the cardiovascular apparatus, etc. A specially selected set of hormone and pharmacological preparations is recommended to stimulate hemopoiesis.

  20. The Influence of Oral L-Glutamine Supplementation on Muscle Strength Recovery and Soreness Following Unilateral Knee Extension Eccentric Exercise.

    PubMed

    Legault, Zachary; Bagnall, Nicholas; Kimmerly, Derek S

    2015-10-01

    The study aimed to examine the effects that L-glutamine supplementation has on quadriceps muscle strength and soreness ratings following eccentric exercise. It was hypothesized that glutamine ingestion would quicken the recovery rate of peak force production and decrease muscle soreness ratings over a 72-hr recovery period. Sixteen healthy participants (8♀/8♂; 22 ± 4 years) volunteered in a double-blind, randomized, placebo-controlled crossover study. Supplement conditions consisted of isoenergetic placebo (maltodextrin, 0.6 g·kg-1·day-1) and L-glutamine (0.3 g·kg-1·day-1 + 0.3 g·kg-1·day-1 maltodextrin) ingestion once per day over 72 hr. Knee extensor peak torque at 0°, 30°, and 180° per second and muscle soreness were measured before, immediately following, 24, 48, and 72 hr posteccentric exercise. Eccentric exercise consisted of 8 sets (10 repetitions/set) of unilateral knee extension at 125% maximum concentric force with 2-min rest intervals. L-glutamine resulted in greater relative peak torque at 180°/sec both immediately after (71 ± 8% vs. 66 ± 9%), and 72 hr (91 ± 8% vs. 86 ± 7%) postexercise (all, p < .01). In men, L-glutamine produced greater (p < .01) peak torques at 30°/ sec postexercise. Men also produced greater normalized peak torques at 30°/sec (Nm/kg) in the L-glutamine condition than women (all, p < .05). In the entire sample, L-glutamine resulted in lower soreness ratings at 24 (2.8 ± 1.2 vs. 3.4 ± 1.2), 48 (2.6 ± 1.4 vs. 3.9 ± 1.2), and 72 (1.7 ± 1.2 vs. 2.9 ± 1.3) hr postexercise (p < .01). The L-glutamine supplementation resulted in faster recovery of peak torque and diminished muscle soreness following eccentric exercise. The effect of L-glutamine on muscle force recovery may be greater in men than women. PMID:25811544

  1. Central alterations of neuromuscular function and feedback from group III-IV muscle afferents following exhaustive high-intensity one-leg dynamic exercise.

    PubMed

    Pageaux, Benjamin; Angius, Luca; Hopker, James G; Lepers, Romuald; Marcora, Samuele M

    2015-06-15

    The aims of this investigation were to describe the central alterations of neuromuscular function induced by exhaustive high-intensity one-leg dynamic exercise (OLDE, study 1) and to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations and their recovery are associated with changes in afferent feedback. Both studies consisted of two time-to-exhaustion tests at 85% peak power output. In study 1, voluntary activation level (VAL), M-wave, cervicomedullary motor evoked potential (CMEP), motor evoked potential (MEP), and MEP cortical silent period (CSP) of the knee extensor muscles were measured. In study 2, mean arterial pressure (MAP) and leg muscle pain were measured during MO. Measurements were performed preexercise, at exhaustion, and after 3 min recovery. Compared with preexercise values, VAL was lower at exhaustion (-13 ± 13%, P < 0.05) and after 3 min of recovery (-6 ± 6%, P = 0.05). CMEP area/M area was lower at exhaustion (-38 ± 13%, P < 0.01) and recovered after 3 min. MEP area/M area was higher at exhaustion (+25 ± 27%, P < 0.01) and after 3 min of recovery (+17 ± 20%, P < 0.01). CSP was higher (+19 ± 9%, P < 0.01) only at exhaustion and recovered after 3 min. Markers of afferent feedback (MAP and leg muscle pain during MO) were significantly higher only at exhaustion. These findings suggest that the alterations in spinal excitability and CSP induced by high-intensity OLDE are associated with an increase in afferent feedback at exhaustion, whereas central fatigue does not fully recover even when significant afferent feedback is no longer present. PMID:25855308

  2. Impaired Hyperemic Response to Exercise Post Stroke

    PubMed Central

    Durand, Matthew J.; Murphy, Spencer A.; Schaefer, Kathleen K.; Hunter, Sandra K.; Schmit, Brian D.; Gutterman, David D.; Hyngstrom, Allison S.

    2015-01-01

    Individuals with chronic stroke have reduced perfusion of the paretic lower limb at rest; however, the hyperemic response to graded muscle contractions in this patient population has not been examined. This study quantified blood flow to the paretic and non-paretic lower limbs of subjects with chronic stroke after submaximal contractions of the knee extensor muscles and correlated those measures with limb function and activity. Ten subjects with chronic stroke and ten controls had blood flow through the superficial femoral artery quantified with ultrasonography before and immediately after 10 second contractions of the knee extensor muscles at 20, 40, 60, and 80% of the maximal voluntary contraction (MVC) of the test limb. Blood flow to the paretic and non-paretic limb of stroke subjects was significantly reduced at all load levels compared to control subjects even after normalization to lean muscle mass. Of variables measured, increased blood flow after an 80% MVC was the single best predictor of paretic limb strength, the symmetry of strength between the paretic and non-paretic limbs, coordination of the paretic limb, and physical activity. The impaired hemodynamic response to high intensity contractions was a better predictor of lower limb function than resting perfusion measures. Stroke-dependent weakness and atrophy of the paretic limb do not explain the reduced hyperemic response to muscle contraction alone as the response is similarly reduced in the non-paretic limb when compared to controls. These data may suggest a role for perfusion therapies to optimize rehabilitation post stroke. PMID:26630380

  3. The effects of short-term detraining on exercise performance in soccer players.

    PubMed

    Joo, Chang Hwa

    2016-02-01

    The aim of the present study was to determine whether 1 week of training cessation can affect exercise performance in well-trained soccer players. Upon the completion of a competitive season, 11 male soccer players went through 1-week training cessation. Performances in the 5-m (1.05±0.04 sec vs 1.02±0.03 sec, P=0.03) and 10-m (1.79±0.06 sec vs 1.74±0.06 sec, P=0.03) sprints were significantly increased after 1 week of detraining with a trend for an increase in the 20-m sprint performance (3.07±0.06 sec vs 3.02±0.07 sec, P=0.06). However, the repeated sprint performance (total sprint time [45.7±2.6 sec vs 48.0±2.6 sec, P=0.01] and fatigue index [5.8%±2.8% vs 7.8%±3.2%; P=0.04]) were reduced. In addition, no significant differences were observed for the 30 m (4.23±0.06 sec vs 4.24±0.09 sec, P=0.63), agility (right: 8.08±0.17 sec vs 8.03±0.37 sec, P=0.54; left: 8.05±0.21 sec vs 8.04±0.30 sec, P=0.84), coordination (13.98±1.21 sec vs 14.06±1.34 sec, P=0.75), Yo-Yo intermittent recovery level 2 (1,040.0±291.8 m vs 1,134.5±232.7 m, P=0.08), and knee extensors and flexors peak torques at all applied angular velocities (P<0.05) after detraining. These results indicate that short-term detraining for well-trained soccer players has a significant effect on the speed endurance performance. It is therefore important for the players and their coaches to plan a suitable training program to maintain exercise performance especially speed endurance during off-season. PMID:26933661

  4. The effects of short-term detraining on exercise performance in soccer players

    PubMed Central

    Joo, Chang Hwa

    2016-01-01

    The aim of the present study was to determine whether 1 week of training cessation can affect exercise performance in well-trained soccer players. Upon the completion of a competitive season, 11 male soccer players went through 1-week training cessation. Performances in the 5-m (1.05±0.04 sec vs 1.02±0.03 sec, P=0.03) and 10-m (1.79±0.06 sec vs 1.74±0.06 sec, P=0.03) sprints were significantly increased after 1 week of detraining with a trend for an increase in the 20-m sprint performance (3.07±0.06 sec vs 3.02±0.07 sec, P=0.06). However, the repeated sprint performance (total sprint time [45.7±2.6 sec vs 48.0±2.6 sec, P=0.01] and fatigue index [5.8%±2.8% vs 7.8%±3.2%; P=0.04]) were reduced. In addition, no significant differences were observed for the 30 m (4.23±0.06 sec vs 4.24±0.09 sec, P=0.63), agility (right: 8.08±0.17 sec vs 8.03±0.37 sec, P=0.54; left: 8.05±0.21 sec vs 8.04±0.30 sec, P=0.84), coordination (13.98±1.21 sec vs 14.06±1.34 sec, P=0.75), Yo-Yo intermittent recovery level 2 (1,040.0±291.8 m vs 1,134.5±232.7 m, P=0.08), and knee extensors and flexors peak torques at all applied angular velocities (P<0.05) after detraining. These results indicate that short-term detraining for well-trained soccer players has a significant effect on the speed endurance performance. It is therefore important for the players and their coaches to plan a suitable training program to maintain exercise performance especially speed endurance during off-season. PMID:26933661

  5. Nutrition Coupled with High-Load Traditional or Low-Load Blood Flow Restricted Exercise During Human Limb Suspension

    NASA Technical Reports Server (NTRS)

    Hackney, K. J.; Everett, M.; Ploutz-Snyder, L. L.

    2011-01-01

    High-load resistance exercise (HRE) and low-load blood flow restricted (BFR) exercise have demonstrated efficacy for attenuating unloading related muscle atrophy and dysfunction. In recreational exercisers, protein consumption immediately before and/or after exercise has been shown to increase the skeletal muscle anabolic response to resistance training. PURPOSE: To compare the skeletal muscle adaptations when chocolate milk intake was coupled with HRE or low-load BFR exercise [3 d/wk] during simulated lower limb weightlessness. METHODS: Eleven subjects were counterbalanced [based on age and gender] to HRE (31 +/- 14 yr, 170 +/- 13 cm, 71 +/- 18 kg, 2M/3W) or low-load BFR exercise (31 +/- 12 yr, 169 +/- 13 cm, 66 +/- 14 kg, 2M/4W) during 30 days of unilateral lower limb suspension (ULLS). Both HRE and BFR completed 3 sets of single leg press and calf raise exercise during ULLS. BFR exercise intensity was 20% of repetition maximum (1RM) with a cuff inflation pressure of 1.3 systolic blood pressure (143 4 mmHg). Cuff pressure was maintained during all 3 sets including rest intervals (90s). HRE intensity was 75% 1RM and was performed without cuff inflation. Immediately (<10 min) before and after exercise 8 fl oz of chocolate milk (150 kcal, 2.5g total fat, 22g total carbohydrate, 8g protein) was consumed to optimize acute exercise responses in favor of muscle anabolism. ULLS analog compliance was assessed from leg skin temperature recordings and plantar accelerometry. Muscle cross-sectional area (CSA) for knee extensor and plantar flexor muscle groups were determined from analysis of magnetic resonance images using ImageJ software. 1RM strength for leg press and calf raise was assessed on the Agaton exercise system. Muscular endurance during leg press and calf raise was evaluated from the maximal number of repetitions performed to volitional fatigue using 40% of pre-ULLS 1RM. RESULTS: Steps detected by plantar acceleometry declined by 98.9% during ULLS relative to an

  6. Effects Of Exercise During Bed Rest

    NASA Technical Reports Server (NTRS)

    Greenleaf, John E.; Bernauer, Edmund M.

    1993-01-01

    Pair of reports adds to growing body of knowledge of physical deconditioning caused by prolonged bed rest and effectiveness of various exercise regimens in preserving or restoring fitness. Major objective to determine what regimens to prescribe to astronauts before flight, during prolonged weightlessness, and immediately before returning to Earth. Knowledge also benefits patients confined by illness or injury. First report discusses experiment on effects of two types of periodic, intense, short-duration exercise during bed rest. Experiment also discussed in documents "Effects Of Exercise During Prolonged Bed Rest" (ARC-12190), and "Isotonic And Isokinetic Exercise During Bed Rest" (ARC-12180). Second report reviews knowledge acquired with view toward development of protocols for exercise regimens.

  7. [Excessive energy drink consumption caused marked QT prolongation. Case report].

    PubMed

    Tomcsányi, János; Jávor, Kinga

    2015-10-25

    The authors report a case of a 22-year-old man with atypical chest pain after consumption of six energy drinks (1.5 liter containing 470 mg coffein) with vodka. On admission ECG showed marked QT/QTc prolongation (QT/QTc, 520/580 msec). Next day the QT/QTc returned to fully normal (QT/QTc, 360/430 msec). It was assumed that the patient had a silent long QT syndrome and that high dose of highly caffeinated energy drink triggered the (paradoxical) prolonged QT/QTc. The authors conclude that excessive energy drink intake with alcohol or during physical exercise should be avoided. PMID:26477618

  8. Questionable Exercises.

    ERIC Educational Resources Information Center

    Liemohn, Wendell; Haydu, Traci; Phillips, Dawn

    1999-01-01

    This publication presents general guidelines for exercise prescription that have an anatomical basis but also consider the exerciser's ability to do the exercise correctly. It reviews various common questionable exercises, explaining how some exercises, especially those designed for flexibility and muscle fitness, can cause harm. Safer…

  9. On the biomechanics of cycling. A study of joint and muscle load during exercise on the bicycle ergometer.

    PubMed

    Ericson, M

    1986-01-01

    The aim of the study was to quantify the load induced in the lower limb joints and muscles during exercise on a bicycle ergometer and to study how these loads changed with adjustments of the bicycle ergometer or cycling technique. The forces, load moments and muscular power output acting on and about the hip, knee and ankle joints during cycling were determined using cine-film, pedal force measurements and biomechanical calculations based upon static and dynamic mechanics. The muscular activity of eleven lower limb muscles was recorded and quantified using EMG. The load moments acting about the bilateral hip, knee and ankle joint axes were found to be generally lower than those induced during normal level walking. The varus and valgus load moments acting about the antero-posterior knee joint axis were approximately the same as those induced during walking. The tibio-femoral compressive joint force and the anteriorly directed tibio-femoral shear force mainly stressing the anterior cruciate ligament were low. The talocrural joint compressive force and achilles tendon tensile force were low compared to those in level walking. The magnitude of lower limb muscular activity during cycling approximated that obtained during walking, with three major exceptions. M. vastus medialis et lateralis were more activated during cycling than during walking, and tibialis anterior was less activated. The hip extensor muscles produced 27%, hip flexors 4%, knee extensors 39%, knee flexors 10% and ankle plantar flexors 20% of the total positive mechanical work. Of the four parameters studied (workload, pedalling rate, saddle height, pedal foot position) workload was the most important adjustment factor for change of joint load and muscular activity. An increased pedalling rate increased the muscular activity in most of the muscles investigated, generally without changing the joint load. Increased saddle height decreased the maximum flexing knee load moment, but did not significantly

  10. Blood flow-restricted exercise in space

    PubMed Central

    2012-01-01

    Prolonged exposure to microgravity results in chronic physiological adaptations including skeletal muscle atrophy, cardiovascular deconditioning, and bone demineralization. To attenuate the negative consequences of weightlessness during spaceflight missions, crewmembers perform moderate- to high-load resistance exercise in conjunction with aerobic (cycle and treadmill) exercise. Recent evidence from ground-based studies suggests that low-load blood flow-restricted (BFR) resistance exercise training can increase skeletal muscle size, strength, and endurance when performed in a variety of ambulatory populations. This training methodology couples a remarkably low exercise training load (approximately 20%–50% one repetition maximum (1RM)) with an inflated external cuff (width, ranging between approximately 30–90 mm; pressure, ranging between approximately 100–250 mmHg) that is placed around the exercising limb. BFR aerobic (walking and cycling) exercise training methods have also recently emerged in an attempt to enhance cardiovascular endurance and functional task performance while incorporating minimal exercise intensity. Although both forms of BFR exercise training have direct implications for individuals with sarcopenia and dynapenia, the application of BFR exercise training during exposure to microgravity to prevent deconditioning remains controversial. The aim of this review is to present an overview of BFR exercise training and discuss the potential usefulness of this method as an adjunct exercise countermeasure during prolonged spaceflight. The work will specifically emphasize ambulatory BFR exercise training adaptations, mechanisms, and safety and will provide directions for future research. PMID:23849078

  11. Fluid balance and exercise.

    PubMed

    Maughan, R J

    1992-10-01

    The rate of metabolic heat production during prolonged exercise may be increased to 15-20 times that at rest. Evaporation of sweat secreted onto the skin can effectively limit the rise in body temperature which would otherwise occur, but results in the loss of water and electrolytes from the body. Dehydration and an increased thermal load can accelerate the onset of fatigue during exercise. The available evidence supports the idea that ingestion of fluids during prolonged exercise can improve performance. Heart rate and rectal temperature will generally be lower, and plasma volume will be better maintained when fluids are given. There is, however, no general agreement on the optimum formulation nor on the frequency or volume of drinking that is most appropriate. In practice, the ideal solution will depend on a number of factors, including the duration and intensity of the exercise, the environmental conditions and the characteristics of the individual. The variation between individuals is, however, large and the optimum strategy can only be established by subjective experience. PMID:1483752

  12. Exercise-induced purpura.

    PubMed

    Ramelet, Albert-Adrien

    2004-01-01

    Exercise-induced purpura (EIP) occurs on the lower legs after unusual or major muscular activity, as in marathon runners or as after long walks, especially in the mountains in hot weather. In leisure walkers, patients are otherwise healthy females. There is no relation with chronic venous disorder. Erythematous, urticarial or purpuric plaques arise on the lower leg, usually sparing the skin compressed by socks. Symptoms include itch, pain and a burning sensation. Histopathology demonstrates leukocytoclastic vasculitis. The lesions fade after some days, with frequent relapses at further muscular exercises and may be prevented in some cases by compression, intake of venoactive drugs and local application of steroids. EIP is not uncommon, even if very few descriptions have yet been published. It appears to be consecutive to venous stasis induced by an acute failure of the muscle pump of the calf and thermoregulation decompensation, after a prolonged and unusual exercise, such as running or walking in hot weather. PMID:15178910

  13. Function of a large biarticular hip and knee extensor during walking and running in guinea fowl (Numida meleagris)

    PubMed Central

    Carr, Jennifer A.; Ellerby, David J.; Marsh, Richard L.

    2011-01-01

    SUMMARY Physiological and anatomical evidence suggests that in birds the iliotibialis lateralis pars postacetabularis (ILPO) is functionally important for running. Incorporating regional information, we estimated the mean sarcomere strain trajectory and electromyographic (EMG) amplitude of the ILPO during level and incline walking and running. Using these data and data in the literature of muscle energy use, we examined three hypotheses: (1) active lengthening will occur on the ascending limb of the length–tension curve to avoid potential damage caused by stretch on the descending limb; (2) the active strain cycle will shift to favor active shortening when the birds run uphill and shortening will occur on the plateau and shallow ascending limb of the length–tension curve; and (3) measures of EMG intensity will correlate with energy use when the mechanical function of the muscle is similar. Supporting the first hypothesis, we found that the mean sarcomere lengths at the end of active lengthening during level locomotion were smaller than the predicted length at the start of the plateau of the length–tension curve. Supporting the second hypothesis, the magnitude of active lengthening decreased with increasing slope, whereas active shortening increased. In evaluating the relationship between EMG amplitude and energy use (hypothesis 3), we found that although increases in EMG intensity with speed, slope and loading were positively correlated with muscle energy use, the quantitative relationships between these variables differed greatly under different conditions. The relative changes in EMG intensity and energy use by the muscle probably varied because of changes in the mechanical function of the muscle that altered the ratio of muscle energy use to active muscle volume. Considering the overall function of the cycle of active lengthening and shortening of the fascicles of the ILPO, we conclude that the function of active lengthening is unlikely to be energy conservation and may instead be related to promoting stability at the knee. The work required to lengthen the ILPO during stance is provided by co-contracting knee flexors. We suggest that this potentially energetically expensive co-contraction serves to stabilize the knee in early stance by increasing the mechanical impedance of the joint. PMID:21957104

  14. Sleep and exercise: a reciprocal issue?

    PubMed

    Chennaoui, Mounir; Arnal, Pierrick J; Sauvet, Fabien; Léger, Damien

    2015-04-01

    Sleep and exercise influence each other through complex, bilateral interactions that involve multiple physiological and psychological pathways. Physical activity is usually considered as beneficial in aiding sleep although this link may be subject to multiple moderating factors such as sex, age, fitness level, sleep quality and the characteristics of the exercise (intensity, duration, time of day, environment). It is therefore vital to improve knowledge in fundamental physiology in order to understand the benefits of exercise on the quantity and quality of sleep in healthy subjects and patients. Conversely, sleep disturbances could also impair a person's cognitive performance or their capacity for exercise and increase the risk of exercise-induced injuries either during extreme and/or prolonged exercise or during team sports. This review aims to describe the reciprocal fundamental physiological effects linking sleep and exercise in order to improve the pertinent use of exercise in sleep medicine and prevent sleep disorders in sportsmen. PMID:25127157

  15. Oxygen cost of dynamic or isometric exercise relative to recruited muscle mass

    PubMed Central

    Elder, Christopher P; Mahoney, Edward T; Black, Christopher D; Slade, Jill M; Dudley, Gary A

    2006-01-01

    Background Oxygen cost of different muscle actions may be influenced by different recruitment and rate coding strategies. The purpose of this study was to account for these strategies by comparing the oxygen cost of dynamic and isometric muscle actions relative to the muscle mass recruited via surface electrical stimulation of the knee extensors. Methods Comparisons of whole body pulmonary Δ V˙ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacuWGwbGvgaGaaaaa@2DEA@O2 were made in seven young healthy adults (1 female) during 3 minutes of dynamic or isometric knee extensions, both induced by surface electrical stimulation. Recruited mass was quantified in T2 weighted spin echo magnetic resonance images. Results The Δ V˙ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacuWGwbGvgaGaaaaa@2DEA@O2 for dynamic muscle actions, 242 ± 128 ml • min-1 (mean ± SD) was greater (p = 0.003) than that for isometric actions, 143 ± 99 ml • min-1. Recruited muscle mass was also greater (p = 0.004) for dynamic exercise, 0.716 ± 282 versus 0.483 ± 0.139 kg. The rate of oxygen consumption per unit of recruited muscle (V˙O2RM MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacuqGwbGvgaGaaiabb+eapnaaBaaaleaacqaIYaGmdaahaaadbeqaaiabbkfasjabb2eanbaaaSqabaaaaa@32B0@) was similar in dynamic and isometric exercise (346 ± 162 versus 307 ± 198 ml • kg-1 • min-1; p = 0.352), but the V˙O2RM MathType@MTEF@5

  16. Troponin and exercise.

    PubMed

    Gresslien, T; Agewall, S

    2016-10-15

    Cardiac troponins are the preferred biomarkers in diagnostic of myocardial infarction, but these markers also can rise in response to exercise. Multiple studies have assessed troponins post-exercise, but the results have varied and there have been disagreements about the mechanism of troponin release. The aim of this paper was to review the literature, and to consider factors and mechanisms regarding exercise-induced increase of troponin. 145 studies were found after a search in pubmed and inclusion of additional articles found in the reference list of the first articles. Results showed that troponin rises in 0-100% of subjects after prolonged heavy exercise like marathon, but also after short-term and intermittent exercise like 30min of running and basketball. The variation can be due to factors like intensity, age, training experience, variation in sample size, blood sample timing and troponin assay. The pattern of troponin level post-exercise corresponds to release from the cytosolic compartment of cardiomyocytes. Increased membrane permeability might be caused by production of reactive oxygen species or alterations in calcium, pH, glucose/fat metabolism or in communication between integrins. Other suggested mechanisms are increased cardiovascular stress, inflammation, vasculitis, release of troponin degradation products in "blebs", dehydration, impaired renal clearance and expression of cardiac troponin in skeletal muscle. It can be concluded that both heavy and light exercise may cause elevated troponin, which have to be considered when patient are suspected to have a myocardial infarction. Several factors probably influence post-exercise levels of troponin, but the mechanism of release is most likely physiologic. PMID:27420587

  17. Exercise Prescription.

    ERIC Educational Resources Information Center

    Ribisl, Paul M.

    If exercise programs are to become effective in producing the desired results, then the correct exercise prescription must be applied. Four variables should be controlled in the prescription of exercise: (a) type of activity, (b) intensity, (c) duration, and (d) frequency. The long-term prescription of exercise involves the use of a (a) starter…

  18. Plasma atriopeptin response to prolonged cycling in humans.

    PubMed

    Perrault, H; Cantin, M; Thibault, G; Brisson, G R; Brisson, G; Beland, M

    1991-03-01

    The exercise-induced increase in plasma atriopeptin (ANP) has been related to exercise intensity. The independent effect of duration on the ANP response to dynamic exercise remains incompletely documented. The purpose of this study was to describe the time course of plasma ANP concentration during a 90-min cycling exercise protocol and to examine this in light of concurrent variations in plasma arginine vasopressin (AVP), aldosterone (ALD), and catecholamine (norepinephrine and epinephrine) concentrations as well as plasma renin activity (PRA). Seven male and four female healthy college students (23 +/- 2 yr) completed a prolonged exercise protocol on a cycle ergometer at an intensity of 67% of maximal O2 uptake. Venous blood was sampled through an indwelling catheter at rest, after 15, 30, 45, 60, and 90 min of exercise, and after 30 min of passive upright recovery. Results (means +/- SE) indicate an increase in ANP from rest (22 +/- 2.6 pg/ml) at 15 min of exercise (45.3 +/- 7.4 pg/ml) with a further increase at 30 min (59.4 +/- 9.8 pg/ml) and a leveling-off thereafter until completion of the exercise protocol (51.7 +/- 10.7 pg/ml). In plasma ALD and PRA, a significant increase was found from rest (ALD, 21.4 +/- 6.4 ng/dl), PRA, 2.5 +/- 0.5 ng.ml-1.h-1 after 30 min of cycling, which continued to increase until completion of the exercise (ALD 46.6 +/- 8.7 ng/dl, PRA 9.5 +/- 0.9 ng.ml-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1827790

  19. Dynamic asymmetry of phosphocreatine concentration and O2 uptake between the on- and off-transients of moderate- and high-intensity exercise in humans

    PubMed Central

    Rossiter, H B; Ward, S A; Kowalchuk, J M; Howe, F A; Griffiths, J R; Whipp, B J

    2002-01-01

    The on- and off-transient (i.e. phase II) responses of pulmonary oxygen uptake (V̇O2) to moderate-intensity exercise (i.e. below the lactate threshold, θL) in humans has been shown to conform to both mono-exponentiality and ‘on-off’ symmetry, consistent with a system manifesting linear control dynamics. However above θL the V̇O2 kinetics have been shown to be more complex: during high-intensity exercise neither mono-exponentiality nor ‘on-off’ symmetry have been shown to appropriately characterise the V̇O2 response. Muscle [phosphocreatine] ([PCr]) responses to exercise, however, have been proposed to be dynamically linear with respect to work rate, and to demonstrate ‘on-off’ symmetry at all work intenisties. We were therefore interested in examining the kinetic characteristics of the V̇O2 and [PCr] responses to moderate- and high-intensity knee-extensor exercise in order to improve our understanding of the factors involved in the putative phosphate-linked control of muscle oxygen consumption. We estimated the dynamics of intramuscular [PCr] simultaneously with those of V̇O2 in nine healthy males who performed repeated bouts of both moderate- and high-intensity square-wave, knee-extension exercise for 6 min, inside a whole-body magnetic resonance spectroscopy (MRS) system. A transmit-receive surface coil placed under the right quadriceps muscle allowed estimation of intramuscular [PCr]; V̇O2 was measured breath-by-breath using a custom-designed turbine and a mass spectrometer system. For moderate exercise, the kinetics were well described by a simple mono-exponential function (following a short cardiodynamic phase for V̇O2,), with time constants (τ) averaging: τV̇O2,on 35 ± 14 s (± s.d.), τ[PCr]on 33 ± 12 s, τV̇O2,off 50 ± 13 s and τ[PCr]off 51 ± 13 s. The kinetics for both V̇O2 and [PCr] were more complex for high-intensity exercise. The fundamental phase expressing average τ values of τV̇O2,on 39 ± 4 s, τ[PCr]on 38 ± 11 s

  20. Compulsive Exercise

    MedlinePlus

    ... of power to help them cope with low self-esteem. Although compulsive exercising doesn't have to accompany ... a downward spiral of negative thinking and low self-esteem. continue Why Is Exercising Too Much a Bad ...

  1. Exercise & Sleep

    MedlinePlus

    ... on. Feature: Back to School, the Healthy Way Exercise & Sleep Past Issues / Fall 2012 Table of Contents ... helps kids. Photo: iStock 6 "Bests" About Kids' Exercise At least one hour of physical activity a ...

  2. Physiology Of Prolonged Bed Rest

    NASA Technical Reports Server (NTRS)

    Greenleaf, John E.

    1991-01-01

    Report describes physiological effects of prolonged bed rest. Rest for periods of 24 hours or longer deconditions body to some extent; healing proceeds simultaneously with deconditioning. Report provides details on shifts in fluid electrolytes and loss of lean body mass, which comprises everything in body besides fat - that is, water, muscle, and bone. Based on published research.

  3. Measures that Prolong Work Life.

    ERIC Educational Resources Information Center

    Nusberg, Charlotte

    1986-01-01

    Discusses measures that have been adopted by France, Great Britain, Sweden, the Netherlands, the United States, and Japan to prolong the work life of older workers. Measures include job transfer and exemption, dismissal protection, retirement policies, and reintegration of unemployed older workers. (JOW)

  4. Prolonged abulia following putaminal hemorrhage.

    PubMed

    Nagaratnam, N; Fanella, S; Gopinath, S; Goodwin, A

    2001-01-01

    Abulia, akinetic mutism, and other conditions causing reduced activity and slowness are a continuum of severity of behavior. Unilateral lesions usually cause transient symptoms. This article describes a patient with prolonged abulia lasting 12 weeks after aspontaneous left putaminal hemorrhage. He developed seizures that could be a contributing factor. The pathophysiologic mechanisms are discussed. PMID:17903806

  5. Caffeine and exercise.

    PubMed

    Paluska, Scott A

    2003-08-01

    Caffeine is the most commonly consumed drug in the world, and athletes frequently use it as an ergogenic aid. It improves performance and endurance during prolonged, exhaustive exercise. To a lesser degree it also enhances short-term, high-intensity athletic performance. Caffeine improves concentration, reduces fatigue, and enhances alertness. Habitual intake does not diminish caffeine's ergogenic properties. Several mechanisms have been proposed to explain the physiologic effects of caffeine, but adenosine receptor antagonism most likely accounts for the primary mode of action. It is relatively safe and has no known negative performance effects, nor does it cause significant dehydration or electrolyte imbalance during exercise. Routine caffeine consumption may cause tolerance or dependence, and abrupt discontinuation produces irritability, mood shifts, headache, drowsiness, or fatigue. Major sport governing bodies ban excessive use of caffeine, but current monitoring techniques are inadequate, and ethical dilemmas persist regarding caffeine intake by athletes. PMID:12834577

  6. Morning Exercise

    ERIC Educational Resources Information Center

    Schmitt, Natalie Crohn

    2006-01-01

    In this article, Natalie Schmitt recalls her teaching experiences with morning exercise programs, beginning with her first teaching job as assistant Morning Exercise teacher at the Francis W. Parker School in Chicago. In the Morning Exercises, students were encouraged to employ all means of expression: speaking, drawing, dancing, singing, acting.…

  7. Propofol-associated QTc prolongation

    PubMed Central

    Scalese, Michael J.; Herring, Holly R.; Rathbun, R. Chris; Skrepnek, Grant H.; Ripley, Toni L.

    2016-01-01

    Objectives: Propofol is a preferred agent for sedation in patients in the intensive care unit (ICU) due, in part, to its established safety profile. Despite this, recent case reports have suggested a potential for prolongation of the corrected QT interval (QTc) in ICU patients receiving propofol, though limited empirical work has been conducted to evaluate this association. As such, the purpose of this study was to assess the relationship between propofol infusion and QTc prolongation in a historical cohort of ICU patients. Methods: A single-center, historical, observational, pre-post cohort analysis of medical records from admitted patients ⩾18 years old with cardiovascular disease was conducted, involving cases who received propofol infusion for ⩾3 hours with sequential electrocardiogram monitoring from 2006 to 2012. A multivariable, generalized linear model regression was employed to assess the primary outcome of on-propofol QTc interval (QTc2), controlling for various demographic and clinical factors. Results: A total of 96 patients met inclusion criteria, averaging 56.1 ± 14.1 years of age and 86.1 ± 25.0 kg, with 37.5% being female. A mean prolongation in QTc interval of 30.4 ± 55.5 ms (p < 0.001) was observed during the propofol infusion, with 43.8% of cases exhibiting an on-infusion QTc2 of ⩾ 500 ms. Regression analyses suggested that prolongation in on-propofol QTc was independently associated with baseline QTc interval and amiodarone use, while weight as inversely associated with QTc2 (p < 0.05). Conclusion: This historical cohort analysis of adult ICU patients receiving propofol suggests that on-infusion QTc prolongation was associated with increasing baseline QTc interval and with amiodarone use. Further research is needed to evaluate the clinical significance and cause-and-effect relationship between potential QTc changes and propofol use in the ICU. PMID:27298717

  8. Prolonged stimulus exposure reveals prolonged neurobehavioral response patterns.

    PubMed

    Johnson, Brett A; Woo, Cynthia C; Zeng, Yu; Xu, Zhe; Hingco, Edna E; Ong, Joan; Leon, Michael

    2010-05-15

    Although it has been shown repeatedly that minimum response times in sensory systems can be quite short, organisms more often continue to respond to sensory stimuli over considerably longer periods of time. The continuing response to sensory stimulation may be a more realistic assessment of natural sensory responses, so we determined for how long a stimulus would evoke a response in naïve, freely moving animals. Specifically, we determined for how long such rats responded to odorants during continuous passive exposures by monitoring their sniffing with whole-body plethysmography. We found that naïve rats continue to sniff odorants vigorously for up to 3 minutes, much longer than what has been reported for highly trained, highly motivated rats. Patterns of 2-deoxyglucose (2-DG) uptake in the glomerular layer of the rat olfactory bulb also were seen after only 1-5 minutes of odorant exposure, overlapping with the period of increased respiration to odorants. Moreover, these 2-DG uptake patterns closely resembled the patterns that emerge from prolonged odorant exposures, suggesting that activity mapping over prolonged periods can identify areas of activity that are present when rats are still attending and responding to odorant stimuli. Given these findings, it seems important to consider the possibility that prolonged exposure to other sensory stimuli will reveal more realistic neural response patterns. PMID:20232477

  9. Brain glycogen supercompensation following exhaustive exercise.

    PubMed

    Matsui, Takashi; Ishikawa, Taro; Ito, Hitoshi; Okamoto, Masahiro; Inoue, Koshiro; Lee, Min-Chul; Fujikawa, Takahiko; Ichitani, Yukio; Kawanaka, Kentaro; Soya, Hideaki

    2012-02-01

    Brain glycogen localized in astrocytes, a critical energy source for neurons, decreases during prolonged exhaustive exercise with hypoglycaemia. However, it is uncertain whether exhaustive exercise induces glycogen supercompensation in the brain as in skeletal muscle. To explore this question, we exercised adult male rats to exhaustion at moderate intensity (20 m min(-1)) by treadmill, and quantified glycogen levels in several brain loci and skeletal muscles using a high-power (10 kW) microwave irradiation method as a gold standard. Skeletal muscle glycogen was depleted by 82-90% with exhaustive exercise, and supercompensated by 43-46% at 24 h after exercise. Brain glycogen levels decreased by 50-64% with exhaustive exercise, and supercompensated by 29-63% (whole brain 46%, cortex 60%, hippocampus 33%, hypothalamus 29%, cerebellum 63% and brainstem 49%) at 6 h after exercise. The brain glycogen supercompensation rates after exercise positively correlated with their decrease rates during exercise. We also observed that cortical and hippocampal glycogen supercompensation were sustained until 24 h after exercise (long-lasting supercompensation), and their basal glycogen levels increased with 4 weeks of exercise training (60 min day(-1) at 20 m min(-1)). These results support the hypothesis that, like the effect in skeletal muscles, glycogen supercompensation also occurs in the brain following exhaustive exercise, and the extent of supercompensation is dependent on that of glycogen decrease during exercise across brain regions. However, supercompensation in the brain preceded that of skeletal muscles. Further, the long-lasting supercompensation of the cortex and hippocampus is probably a prerequisite for their training adaptation (increased basal levels), probably to meet the increased energy demands of the brain in exercising animals. PMID:22063629

  10. [Recovery after prolonged muscular work].

    PubMed

    Viru, A A; Varrik, E V; Eépik, V E; Smirnova, T A; Viru, M A

    1985-11-01

    Increased protein, tyrosine and 3-methylhistidine content has been observed in the skeletal muscles of rats 2-24 h after a 10-hour swimming period. This was accompanied by a significant rise in 3-methylhistidine excretion during the second day of the recovery period. Such combination of alterations suggests simultaneous augmentation of both protein synthesis and decomposition in the muscles after active work. The start of the alterations coincides with post-exercise increase of blood corticosterone level (2-6 h after work) and with the achievement of glycogen supercompensation in the liver and muscles. PMID:4063500