Exercise-Induced Fatigue in One Leg Does Not Impair the Neuromuscular Performance in the Contralateral Leg but Improves the Excitability of the Ipsilateral Corticospinal Pathway

To investigate the influence of pre-induced fatigue in one leg on neuromuscular performance and corticospinal responses of the contralateral homologous muscles, three experiments were conducted with different exercise protocols; A (n = 12): a 60 s rest vs. time-matched sustained left leg knee extension maximum voluntary contraction (MVC), B (n = 12): a 60 s rest vs. time-matched left leg MVC immediately followed by 60 s right leg MVC, and C (n = 9): a similar protocol to experiment B, but with blood flow occluded in the left leg while the right leg was performing the 60 s MVC. The neuromuscular assessment included 5 s knee extensions at 100%, 75%, and 50% of MVC. At each force level, transcranial magnetic and peripheral nerve stimuli were elicited to investigate the influence of different protocols on the right (tested) knee extensors’ maximal force output, voluntary activation, corticospinal excitability, and inhibition. The pre-induced fatigue in the left leg did not alter the performance nor the neuromuscular responses recorded from the right leg in the three experiments (all p > 0.3). However, enhanced corticospinal pathway excitability was evident in the tested knee extensors (p = 0.002). These results suggest that the pre-induced fatigue and muscle ischemia in one leg did not compromise the central and peripheral components of the neuromuscular function in the tested contralateral leg.

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Hyperthermia and central fatigue during prolonged exercise in humans

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.3.1055 ◽

2001 ◽

Vol 91 (3) ◽

pp. 1055-1060 ◽

Cited By ~ 349

Author(s):

Lars Nybo ◽

Bodil Nielsen

Keyword(s):

Core Temperature ◽

Maximal Oxygen Consumption ◽

Knee Extensor ◽

Central Fatigue ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Extensors ◽

Total Force ◽

Impaired Performance

The present study investigated the effects of hyperthermia on the contributions of central and peripheral factors to the development of neuromuscular fatigue. Fourteen men exercised at 60% maximal oxygen consumption on a cycle ergometer in hot (40°C; hyperthermia) and thermoneutral (18°C; control) environments. In hyperthermia, the core temperature increased throughout the exercise period and reached a peak value of 40.0 ± 0.1°C (mean ± SE) at exhaustion after 50 ± 3 min of exercise. In control, core temperature stabilized at ∼38.0 ± 0.1°C, and exercise was maintained for 1 h without exhausting the subjects. Immediately after the cycle trials, subjects performed 2 min of sustained maximal voluntary contraction (MVC) either with the exercised legs (knee extension) or with a “nonexercised” muscle group (handgrip). The degree of voluntary activation during sustained maximal knee extensions was assessed by superimposing electrical stimulation (EL) to nervus femoralis. Voluntary knee extensor force was similar during the first 5 s of contraction in hyperthermia and control. Thereafter, force declined in both trials, but the reduction in maximal voluntary force was more pronounced in the hyperthermic trial, and, from 30 to 120 s, the force was significantly lower in hyperthermia compared with control. Calculation of the voluntary activation percentage (MVC/MVC + EL) revealed that the degree of central activation was significantly lower in hyperthermia (54 ± 7%) compared with control (82 ± 6%). In contrast, total force of the knee extensors (MVC + force from EL) was not different in the two trials. Force development during handgrip contraction followed the same pattern of response as was observed for the knee extensors. In conclusion, these data demonstrate that the ability to generate force during a prolonged MVC is attenuated with hyperthermia, and the impaired performance is associated with a reduction in the voluntary activation percentage.

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Effects of caffeine on neuromuscular function

Journal of Applied Physiology ◽

10.1152/jappl.1999.87.2.801 ◽

1999 ◽

Vol 87 (2) ◽

pp. 801-808 ◽

Cited By ~ 145

Author(s):

J. M. Kalmar ◽

E. Cafarelli

Keyword(s):

Repeated Measures ◽

Isometric Force ◽

Neuromuscular Function ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Extensors ◽

Double Blind ◽

Twitch Interpolation ◽

Motor Unit Firing ◽

The Right

This double-blind, repeated-measures study examined the effects of caffeine on neuromuscular function. Eleven male volunteers [22.3 ± 2.4 (SD) yr] came to the laboratory for control, placebo, and caffeine (6 mg/kg dose) trials. Each trial consisted of 10 × 1-ms stimulation of the tibial nerve to elicit maximal H reflexes of the soleus, four attempts at a maximal voluntary contraction (MVC) of the right knee extensors, six brief submaximal contractions, and a 50% MVC held to fatigue. Isometric force and surface electromyographic signals were recorded continuously. The degree of maximal voluntary activation was assessed with the twitch-interpolation technique. Single-unit recordings were made with tungsten microelectrodes during the submaximal contractions. Voluntary activation at MVC increased by 3.50 ± 1.01 (SE) % ( P < 0.01), but there was no change in H-reflex amplitude, suggesting that caffeine increases maximal voluntary activation at a supraspinal level. Neither the force-EMG relationship nor motor unit firing rates were altered by caffeine. Subjects were able to hold a 50% MVC for an average of 66.1 s in the absence of caffeine. Time to fatigue (Tlim) increased by 25.80 ± 16.06% after caffeine administration ( P < 0.05). There was no significant change in Tlim from pretest to posttest in the control or placebo trials. The increase in Tlim was associated with an attenuated decline in twitch amplitude, which would suggest that the mechanism is, at least in part, peripheral.

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Skin Cooling Alters the Activation Patterns of Different Heads of the Quadriceps

Canadian Journal of Applied Physiology ◽

10.1139/h05-110 ◽

2005 ◽

Vol 30 (2) ◽

pp. 127-139 ◽

Cited By ~ 5

Author(s):

Ryuta Kinugasa ◽

Kazumasa Yoshida ◽

Takayuki Watanabe ◽

Kousuke Kuchiki ◽

Akira Horii

Keyword(s):

Isometric Force ◽

Vastus Lateralis ◽

Maximum Voluntary Contraction ◽

Force Production ◽

Transverse Relaxation Time ◽

Knee Extension ◽

Voluntary Contraction ◽

Activation Patterns ◽

Skin Cooling ◽

The Right

The purpose of this study was to examine the effect of selective skin cooling over m. vastus lateralis (VL) on the activation patterns of quadriceps femoris muscle during knee extension exercise (KEE) using muscle function magnetic resonance imaging (mfMRI). The isometric force production of the right thigh was tested in 7 healthy young men at maximum voluntary contraction (MVC), and the transverse relaxation time (T2) value was taken from mfMR images at rest and immediately after KEE with 4 sets of 10 repetitions at a load equal to 60% of their 10-rep maximum, with and without skin cooling. The cooling was carried out by ice pack on the surface of the skin of the VL for 3 min before resting mfMRI and MVC tests, and before KEE, during KEE, and during the KEE rest intervals. The percent change in T2 of the m. vastus intermedius was significantly increased by skin cooling in comparison to the change without skin cooling, p < 0.05. This result suggests that skin cooling alters the activation pattern of the different heads of the quadriceps. Key words: cold, mfMRI, synergy, recruitment, neuromuscular plasticity

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Improving the measurement of TMS-assessed voluntary activation in the knee extensors

10.31236/osf.io/v74p9 ◽

2018 ◽

Author(s):

Jeanne Dekerle ◽

Aaron Greenhouse-Tucknott ◽

James Graeme Wrightson ◽

lisa Schäfer ◽

Paul Ansdell

Keyword(s):

Isometric Exercise ◽

Femoral Nerve ◽

Internal Validity ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Alternative Methods ◽

Knee Extensors ◽

Post Exercise ◽

Assessment Protocol ◽

Neuromuscular Assessment

The present study was designed to test the accuracy, validity, reliability and sensitivity of the main outcomes of alternative methods for the measure of TMS-assessed voluntary activation (VATMS) in the knee extensors. Ten healthy recreationally active males (24 ± 5 years) completed a neuromuscular assessment protocol (NMA) before and immediately after a fatiguing isometric exercise, consisting of two sets of five contractions (50%, 62.5%, 75%, 87.5%, and 100% of Maximal Voluntary Contraction; MVC) with superimposed TMS-evoked twitches (SITs) for calculation of VATMS (1x5C vs. 2x5C). The protocol was performed on two separate occasions for the measurement of between-day reliability. Where deemed appropriate, comparisons were made with a routinely used protocol [i.e. 50%, 75%, and 100% of MVC (1x3C) performed three times (3x3C)] from re-analysed data (Dekerle et al., 2018). Confidence intervals for the measure of a key determinant of VATMS (estimated resting twitch) were similar between 1x5C and 2x5C but improved by six-fold when compared to 1x3C (P<0.05). Potentiated twitch force evoked via percutaneous electrical stimulation of the femoral nerve was unchanged from pre- to post-NMA at baseline for 1x5C (P>0.05) but decreased for 2x5C and 3x3C (P<0.05). Its recovery post-exercise was lesser for 1x5C compared to 2x5C and 3x3C (P<0.05), with no difference between the latter two (P>0.05). Absolute reliability was strong enough for both 1x5C and 2x5C to depict a true detectable change in the sample’s VATMS following the fatiguing exercise (TEM < 3% at rest, <9% post-exercise) but 2x5C was marginally more sensitive to individual’s changes at baseline. In conclusion, both 1x5C and 2x5C provide reliable measures of VATMS. However, the 1x5C protocol may hold stronger internal validity.

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Locomotor exercise induces long-lasting impairments in the capacity of the human motor cortex to voluntarily activate knee extensor muscles

Journal of Applied Physiology ◽

10.1152/japplphysiol.90911.2008 ◽

2009 ◽

Vol 106 (2) ◽

pp. 556-565 ◽

Cited By ~ 84

Author(s):

Simranjit K. Sidhu ◽

David J. Bentley ◽

Timothy J. Carroll

Keyword(s):

Motor Cortex ◽

Motor Nerve ◽

Maximum Voluntary Contraction ◽

Voluntary Activation ◽

Exercise Session ◽

Knee Extensors ◽

Central Component ◽

Control Session ◽

Cycling Exercise ◽

Human Motor Cortex

Muscle fatigue is a reduction in the capacity to exert force and may involve a “central” component originating in the brain and/or spinal cord. Here we examined whether supraspinal factors contribute to impaired central drive after locomotor endurance exercise. On 2 separate days, 10 moderately active individuals completed a locomotor cycling exercise session or a control session. Brief (2 s) and sustained (30 s) isometric knee extension contractions were completed before and after locomotor exercise consisting of eight, 5-min bouts of cycling at 80% of maximum workload. In the control session, subjects completed the isometric contractions in a rested state. Twitch responses to supramaximal motor nerve stimulation and transcranial magnetic stimulation were obtained to assess peripheral force-generating capacity and voluntary activation. Maximum voluntary contraction (MVC) force during brief contractions decreased by 23 ± 6.3% after cycling exercise and remained 12 ± 2.8% below baseline 45 min later ( F1,9 > 15.5; P < 0.01). Resting twitch amplitudes declined by ∼45% ( F1,9 = 28.3; P < 0.001). Cortical voluntary activation declined from 90.6 ± 1.6% at baseline to 80.6 ± 2.1% after exercise ( F1,9 = 28.0; P < 0.001) and remained significantly reduced relative to control 30–45 min later (80.6 ± 3.4%; F1,9 = 10.7; P < 0.01). Thus locomotor exercise caused a long-lasting impairment in the capacity of the motor cortex to drive the knee extensors. Force was reduced more during sustained MVC after locomotor exercise than in the control session. Peripheral mechanisms contributed relatively more to this force reduction in the control session, whereas supraspinal fatigue played a greater role in sustained MVC reduction after locomotor exercise.

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Long-Term Microgravity Effects on Isometric Handgrip and Precision Pinch Force with Visual and Proprioceptive Feedback

International Journal of Aerospace Engineering ◽

10.1155/2018/1952630 ◽

2018 ◽

Vol 2018 ◽

pp. 1-11

Author(s):

Ilario Puglia ◽

Michele Balsamo ◽

Marco Vukich ◽

Valfredo Zolesi

Keyword(s):

Maximum Voluntary Contraction ◽

Space Station ◽

Voluntary Contraction ◽

Force Output ◽

Isometric Handgrip ◽

Short Term ◽

Space Flights ◽

Pinch Force ◽

Long Duration

The study and analysis of human physiology during short- and long-duration space flights are the most valuable approach in order to evaluate the effect of microgravity on the human body and to develop possible countermeasures in prevision of future exploratory missions and Mars expeditions. Hand performances such as force output and manipulation capacity are fundamental for astronauts’ intra- and extravehicular activities. Previous studies on upper limb conducted on astronauts during short-term missions (10 days) indicated a temporary partial reduction in the handgrip maximum voluntary contraction (MVC) followed by a prompt recovery and adaptation to weightlessness during the last days of the mission. In the present study, we report on the “Crew’s Health: Investigation on Reduced Operability” (CHIRO) protocol, developed for handgrip and pinch force investigations, performed during the six months increment 7 and increment 8 (2003-2004) onboard International Space Station (ISS). We found that handgrip and pinch force performance are reduced during long-term increments in space and are not followed by adaptation during the mission, as conversely reported during short-term increment experiments. The application of protocols developed in space will be eligible to astronauts during long-term space missions and to patients affected by muscle atrophy diseases or nervous system injury on Earth.

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Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles

Journal of Applied Physiology ◽

10.1152/japplphysiol.00230.2004 ◽

2004 ◽

Vol 97 (5) ◽

pp. 1693-1701 ◽

Cited By ~ 118

Author(s):

C. J. de Ruiter ◽

R. D. Kooistra ◽

M. I. Paalman ◽

A. de Haan

Keyword(s):

Muscle Activation ◽

Knee Extensor ◽

Surface Emg ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Angle ◽

Time Integral ◽

Voluntary Contractions ◽

Torque Development

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90° knee angle. Experiments were performed in subjects ( n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle, voluntary MRTD and stimulated MRTD were similar ( P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent ( P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 ± 3.1 to 83.3 ± 3.2% and were positively related ( r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.

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Effect of voluntary vs. artificial activation on the relationship of muscle torque to speed

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.6.2215 ◽

1990 ◽

Vol 69 (6) ◽

pp. 2215-2221 ◽

Cited By ~ 82

Author(s):

G. A. Dudley ◽

R. T. Harris ◽

M. R. Duvoisin ◽

B. M. Hather ◽

P. Buchanan

Keyword(s):

Knee Extensor ◽

Voluntary Activation ◽

Knee Extensors ◽

Angular Velocities ◽

The Central Nervous System ◽

The Right ◽

Artificial Activation ◽

Relationship Of ◽

The Relationship ◽

Eccentric Actions

The speed-torque relationship of the right knee extensor muscle group was investigated in eight untrained subjects (28 +/- 2 yr old). Torque was measured at a specific knee angle during isokinetic concentric or eccentric actions at nine angular velocities (0.17-3.66 rad/s) and during isometric actions. Activation was by "maximal" voluntary effort or by transcutaneous tetanic electrical stimulation that induced an isometric torque equal to 60% (STIM 1) or 45% (STIM 2) of the voluntary isometric value. Torque increased (P less than 0.05) to 1.4 times isometric as the speed of eccentric actions increased to 1.57 rad/s for STIM 1 and STIM 2. Thereafter, increases in eccentric speed did not further increase torque. Torque did not increase (P greater than 0.05) above isometric for voluntary eccentric actions. As the speed of concentric actions increased from 0.00 to 3.66 rad/s, torque decreased (P less than 0.05) more (P less than 0.05) for both STIM 1 and STIM 2 (two-thirds) than for voluntary activation (one-half). As a result of these responses, torque changed three times as much (P less than 0.05) across speeds of concentric and eccentric actions with artificial (3.4-fold) than voluntary (1.1-fold) activation. The results indicate that with artificial activation the normalized speed-torque relationship of the knee extensors in situ is remarkably similar to that of isolated muscle. The relationship for voluntary activation, in contrast, suggests that the ability of the central nervous system to activate the knee extensors during maximal efforts depends on the speed and type of muscle action performed.

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Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

PLoS ONE ◽

10.1371/journal.pone.0242324 ◽

2020 ◽

Vol 15 (11) ◽

pp. e0242324

Author(s):

Jonathan Harnie ◽

Thomas Cattagni ◽

Christophe Cornu ◽

Peter McNair ◽

Marc Jubeau

Keyword(s):

Isometric Contraction ◽

Vastus Lateralis ◽

Force Production ◽

Knee Extensor ◽

Acute Effect ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Tendon Vibration ◽

Knee Angle

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

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Force fluctuations are modulated by alternate muscle activity of knee extensor synergists during low-level sustained contraction

Journal of Applied Physiology ◽

10.1152/japplphysiol.00418.2004 ◽

2004 ◽

Vol 97 (6) ◽

pp. 2121-2131 ◽

Cited By ~ 47

Author(s):

Motoki Kouzaki ◽

Minoru Shinohara ◽

Kei Masani ◽

Tetsuo Fukunaga

Keyword(s):

Correlation Coefficient ◽

Muscle Activity ◽

High Frequency ◽

Vastus Lateralis ◽

Frequency Component ◽

Knee Extension ◽

Voluntary Contraction ◽

High Frequency Component ◽

Knee Extensors ◽

Force Fluctuations

The study examined the hypothesis that altered synergistic activation of the knee extensors leads to cyclic modulation of the force fluctuations. To test this hypothesis, the force fluctuations were investigated during sustained knee extension at 2.5% of maximal voluntary contraction force for 60 min in 11 men. Surface electromyograms (EMG) were recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles. The SD of force and average EMG (AEMG) of each muscle were calculated for 30-s periods during alternate muscle activity. Power spectrum of force was calculated for the low- (≤3 Hz), middle- (4–6 Hz), and high-frequency (8–12 Hz) components. Alternate muscle activity was observed between RF and the set of VL and VM muscles. The SD of force was not constant but variable due to the alternate muscle activity. The SD was significantly greater during high RF activity compared with high VL and VM activity ( P < 0.05), and the correlation coefficient between the SD and AEMG was significantly greater in RF [0.736 (SD 0.095), P < 0.05] compared with VL and VM. Large changes were found in the high-frequency component. During high RF activity, the correlation coefficient between the SD and high-frequency component [0.832 (SD 0.087)] was significantly ( P < 0.05) greater compared with other frequency components. It is suggested that modulations in knee extension force fluctuations are caused by the unique muscle activity in RF during the alternate muscle activity, which augments the high-frequency component of the fluctuations.

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