scholarly journals Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions

2008 ◽  
Vol 105 (4) ◽  
pp. 1199-1209 ◽  
Author(s):  
Sandra K. Hunter ◽  
Gabrielle Todd ◽  
Jane E. Butler ◽  
Simon C. Gandevia ◽  
Janet L. Taylor
Keyword(s):  
Young Adults ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Old Adults ◽  
Flexor Muscles ◽  
Fatiguing Exercise ◽  
Voluntary Contractions ◽  
Potential Area ◽  
Period Duration

This study compared the contribution of supraspinal fatigue to muscle fatigue in old and young adults. Transcranial magnetic stimulation (TMS) of motor cortex was used to assess voluntary activation during maximal voluntary contractions (MVCs) of elbow flexor muscles in 17 young adults (25.5 ± 3.6 yr; mean ± SD) and 7 old adults (73.0 ± 3.3 yr). Subjects performed a fatigue task involving six sustained MVCs (22-s duration, separated by 10 s). Young adults exhibited greater reductions in maximal voluntary torque (67 ± 15% of baseline) than the old (37 ± 6%; P < 0.001). Increments in torque (superimposed twitch) generated by TMS during sustained MVCs increased for the young and old ( P < 0.001) but were larger for the old adults at the start of the sustained contractions and during recovery ( P < 0.05). Voluntary activation was less for the old adults at the start of some sustained contractions and during recovery ( P = 0.02). Motor-evoked potential area increased similarly with age during the fatiguing task but was greater for the old adults than young during recovery. Silent period duration lengthened less for the old adults during the fatigue task. At the end of the fatiguing task, peak relaxation rate of muscle fibers had declined more in the young than the old adults. The greater endurance with age is largely due to a difference in mechanisms located within the muscle. However, recovery from the fatiguing exercise is impaired for old adults because of greater supraspinal fatigue than in the young.

scholarly journals Supraspinal fatigue impedes recovery from a low-intensity sustained contraction in old adults

2012 ◽  
Vol 112 (5) ◽  
pp. 849-858 ◽  
Author(s):  
Tejin Yoon ◽  
Bonnie Schlinder-Delap ◽  
Manda L. Keller ◽  
Sandra K. Hunter
Keyword(s):  
Young Adults ◽  
Pressor Response ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Age Difference ◽  
Task Failure ◽  
Old Adults ◽  
Sustained Contraction ◽  
Low Intensity

This study determined the contribution of supraspinal fatigue and contractile properties to the age difference in neuromuscular fatigue during and recovery from a low-intensity sustained contraction. Cortical stimulation was used to evoke measures of voluntary activation and muscle relaxation during and after a contraction sustained at 20% of maximal voluntary contraction (MVC) until task failure with elbow flexor muscles in 14 young adults (20.9 ± 3.6 yr, 7 men) and 14 old adults (71.6 ± 5.4 yr, 7 men). Old adults exhibited a longer time to task failure than the young adults (23.8 ± 9.0 vs. 11.5 ± 3.9 min, respectively, P < 0.001). The time to failure was associated with initial peak rates of relaxation of muscle fibers and pressor response ( P < 0.05). Increments in torque (superimposed twitch; SIT) generated by transcranial magnetic stimulation (TMS) during brief MVCs, increased during the fatiguing contraction ( P < 0.001) and then decreased during recovery ( P = 0.02). The increase in the SIT was greater for the old adults than the young adults during the fatiguing contraction and recovery ( P < 0.05). Recovery of MVC torque was less for old than young adults at 10 min post-fatiguing contraction (75.1 ± 8.7 vs. 83.6 ± 7.8% of control MVC, respectively, P = 0.01) and was associated with the recovery of the SIT ( r = −0.59, r2 = 0.35, P < 0.001). Motor evoked potential (MEP) amplitude and the silent period elicited during the fatiguing contraction increased less for old adults than young adults ( P < 0.05). The greater fatigue resistance with age during a low-intensity sustained contraction was attributable to mechanisms located within the muscle. Recovery of maximal strength after the low-intensity fatiguing contraction however, was impeded more for old adults than young because of greater supraspinal fatigue. Recovery of strength could be an important variable to consider in exercise prescription of old populations.

scholarly journals Supraspinal fatigue does not explain the sex difference in muscle fatigue of maximal contractions

2006 ◽  
Vol 101 (4) ◽  
pp. 1036-1044 ◽  
Author(s):  
Sandra K. Hunter ◽  
Jane E. Butler ◽  
Gabrielle Todd ◽  
Simon C. Gandevia ◽  
Janet L. Taylor
Keyword(s):  
Sex Difference ◽  
Young Men ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Elbow Flexor ◽  
Cortical Stimulation ◽  
Voluntary Activation ◽  
Men And Women ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles

Young women are less fatigable than young men for maximal and submaximal contractions, but the contribution of supraspinal fatigue to the sex difference is not known. This study used cortical stimulation to compare the magnitude of supraspinal fatigue during sustained isometric maximal voluntary contractions (MVCs) performed with the elbow flexor muscles of young men and women. Eight women (25.6 ± 3.6 yr, mean ± SD) and 9 men (25.4 ± 3.8 yr) performed six sustained MVCs (22-s duration each, separated by 10 s). Before the fatiguing contractions, the men were stronger than the women (75.9 ± 9.2 vs. 42.7 ± 8.0 N·m; P < 0.05) in control MVCs. Voluntary activation measured with cortical stimulation before fatigue was similar for the men and women during the final control MVC (95.7 ± 3.0 vs. 93.3 ± 3.6%; P > 0.05) and at the start of the fatiguing task ( P > 0.05). By the end of the six sustained fatiguing MVCs, the men exhibited greater absolute and relative reductions in torque (65 ± 3% of initial MVC) than the women (52 ± 9%; P < 0.05). The increments in torque (superimposed twitch) generated by motor cortex stimulation during each 22-s maximal effort increased with fatigue ( P < 0.05). Superimposed twitches were similar for men and women throughout the fatiguing task (5.5 ± 4.1 vs. 7.3 ± 4.7%; P > 0.05), as well as in the last sustained contraction (7.8 ± 5.9 vs. 10.5 ± 5.5%) and in brief recovery MVCs. Voluntary activation determined using an estimated control twitch was similar for the men and women at the start of the sustained maximal contractions (91.4 ± 7.4 vs. 90.4 ± 6.8%, n = 13) and end of the sixth contraction (77.2 ± 13.3% vs. 73.1 ± 19.6%, n = 10). The increase in the area of the motor-evoked potential and duration of the silent period did not differ for men and women during the fatiguing task. However, estimated resting twitch amplitude and the peak rates of muscle relaxation showed greater relative reductions at the end of the fatiguing task for the men than the women. These results indicate that the sex difference in fatigue of the elbow flexor muscles is not explained by a difference in supraspinal fatigue in men and women but is largely due to a sex difference of mechanisms located within the elbow flexor muscles.

Supraspinal fatigue during intermittent maximal voluntary contractions of the human elbow flexors

2000 ◽  
Vol 89 (1) ◽  
pp. 305-313 ◽  
Author(s):  
Janet L. Taylor ◽  
Gabrielle M. Allen ◽  
Jane E. Butler ◽  
S. C. Gandevia
Keyword(s):  
Evoked Potential ◽  
Intermittent Exercise ◽  
Human Subjects ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Central Fatigue ◽  
Duty Cycles ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Voluntary Contractions

Responses to transcranial magnetic stimulation in human subjects ( n = 9) were studied during series of intermittent isometric maximal voluntary contractions (MVCs) of the elbow. Stimuli were given during MVCs in four fatigue protocols with different duty cycles. As maximal voluntary torque fell during each protocol, the torque increment evoked by cortical stimulation increased from ∼1.5 to 7% of ongoing torque. Thus “supraspinal” fatigue developed in each protocol. The motor evoked potential (MEP) and silent period in the elbow flexor muscles also changed. The silent period lengthened by 20–75 ms (lowest to highest duty cycle protocol) and recovered significantly with a 5-s rest. The MEP increased in area by >50% in all protocols and recovered significantly with 10 s, but not 5 s, of rest. These changes are similar to those during sustained MVC. The central fatigue demonstrated by the torque increments evoked by the stimuli did not parallel the changes in the electromyogram responses. This suggests that part of the fatigue developed during intermittent exercise is “upstream” of the motor cortex.

Older Adults Use a Unique Strategy to Lift Inertial Loads With the Elbow Flexor Muscles

2000 ◽  
Vol 83 (4) ◽  
pp. 2030-2039 ◽  
Author(s):  
Andrew E. Graves ◽  
Kurt W. Kornatz ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Elbow Joint ◽  
Muscle Activation ◽  
Angular Displacement ◽  
Elbow Flexor ◽  
Lengthening Contractions ◽  
Old Adults ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Target Force

The purpose of this study was to determine the effect of age on the ability to exert steady forces and to perform steady flexion movements with the muscles that cross the elbow joint. An isometric task required subjects to exert a steady force to match a target force that was displayed on a monitor. An anisometric task required subjects to raise and lower inertial loads so that the angular displacement around the elbow joint matched a template displayed on a monitor. Steadiness was measured as the coefficient of variation of force and as the normalized standard deviation of wrist acceleration. For the isometric task, steadiness as a function of target force decreased similarly for old adults and young adults. For the anisometric task, steadiness increased as a function of the inertial load and there were significant differences caused by age. Old adults were less steady than young adults during both shortening and lengthening contractions with the lightest loads. Furthermore, old adults were least steady when performing lengthening contractions. These behaviors appear to be associated with the patterns of muscle activation. These results suggest that different neural strategies are used to control isometric and anisometric contractions performed with the elbow flexor muscles and that these strategies do not change in parallel with advancing age.

Neural adaptations in quadriceps muscle after 4 weeks of local vibration training in young versus older subjects

2018 ◽  
Vol 43 (5) ◽  
pp. 427-436 ◽  
Author(s):  
Robin Souron ◽  
Thibault Besson ◽  
Thomas Lapole ◽  
Guillaume Y. Millet
Keyword(s):  
Vastus Lateralis ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Emg Activity ◽  
Local Vibration ◽  
Jump Performance ◽  
Vibration Training ◽  
Older Subjects

This study investigated the effects of a 4-week local vibration training (LVT) on the function of the knee extensors and corticospinal properties in healthy young and older subjects. Seventeen subjects (9 young and 8 older) performed 3 testing sessions: before (PRE1) and after (PRE2) a 4-week resting period to control the repeatability of the data as well as after the LVT (POST). Jump performance, maximal voluntary contraction (MVC) and electromyographic (EMG) activity on vastus lateralis and rectus femoris muscles were assessed. Single-pulse transcranial magnetic stimulation (TMS) allowed evaluation of cortical voluntary activation (VATMS), motor evoked potential (MEP) area, and silent period (SP) duration. All training adaptations were similar between young and older subjects (p > 0.05) and the following results reflect the pooled sample of subjects. MVC (+11.9% ± 8.0%, p < 0.001) and VATMS (+3.6% ± 5.2%, p = 0.004) were significantly increased at POST compared with PRE2. Maximal vastus lateralis EMG was significantly increased at POST (+21.9% ± 33.7%, p = 0.03). No changes were reported for MEPs on both muscles (p > 0.05). SPs recorded during maximal and submaximal contractions decreased in both muscles at POST (p < 0.05). Vertical jump performance was increased at POST (p < 0.05). LVT seems as effective in young as in older subjects to improve maximal functional capacities through neural modulations occurring at least partly at the supra-spinal level. Local vibration may be used as an efficient alternative training method to improve muscular performance in both healthy young and older subjects.

scholarly journals Eight weeks of local vibration training increases dorsiflexor muscle cortical voluntary activation

2017 ◽  
Vol 122 (6) ◽  
pp. 1504-1515 ◽  
Author(s):  
Robin Souron ◽  
Adrien Farabet ◽  
Léonard Féasson ◽  
Alain Belli ◽  
Guillaume Y. Millet ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Output Curve ◽  
Input Output ◽  
Local Vibration ◽  
Vibration Training

The aim of this study was to evaluate the effects of an 8-wk local vibration training (LVT) program on functional and corticospinal properties of dorsiflexor muscles. Forty-four young subjects were allocated to a training (VIB, n = 22) or control (CON, n = 22) group. The VIB group performed twenty-four 1-h sessions (3 sessions/wk) of 100-Hz vibration applied to the right tibialis anterior. Both legs were tested in each group before training (PRE), after 4 (MID) and 8 (POST) wk of training, and 2 wk after training (POST2W). Maximal voluntary contraction (MVC) torque was assessed, and transcranial magnetic stimulation (TMS) was used to evaluate cortical voluntary activation (VATMS), motor evoked potential (MEP), cortical silent period (CSP), and input-output curve parameters. MVC was significantly increased for VIB at MID for right and left legs [+7.4% ( P = 0.001) and +6.2% ( P < 0.01), respectively] and remained significantly greater than PRE at POST [+12.0% ( P < 0.001) and +10.1% ( P < 0.001), respectively]. VATMS was significantly increased for right and left legs at MID [+4.4% ( P < 0.01) and +4.7% ( P < 0.01), respectively] and at POST [+4.9% ( P = 0.001) and +6.2% ( P = 0.001), respectively]. These parameters remained enhanced in both legs at POST2W. MEP and CSP recorded during MVC and input-output curve parameters did not change at any time point for either leg. Despite no changes in excitability or inhibition being observed, LVT seems to be a promising method to improve strength through an increase of maximal voluntary activation, i.e., neural adaptations. Local vibration may thus be further considered for clinical or aging populations. NEW & NOTEWORTHY The effects of a local vibration training program on cortical voluntary activation measured with transcranial magnetic stimulation were assessed for the first time in dorsiflexors, a functionally important muscle group. We observed that training increased maximal voluntary strength likely because of the strong and repeated activation of Ia spindle afferents during vibration training that led to changes in the cortico-motoneuronal pathway, as demonstrated by the increase in cortical voluntary activation.

scholarly journals A Methodological Framework to Capture Neuromuscular Fatigue Mechanisms Under Stress

2021 ◽  
Vol 2 ◽  
Author(s):  
Oshin Tyagi ◽  
Ranjana K. Mehta
Keyword(s):  
Imaging Techniques ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Central Fatigue ◽  
Brain Regions ◽  
Functional Brain Imaging ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Electromyographic Activity ◽  
Fatigue Development

Neuromuscular fatigue is exacerbated under stress and is characterized by shorter endurance time, greater perceived effort, lower force steadiness, and higher electromyographic activity. However, the underlying mechanisms of fatigue under stress are not well-understood. This review investigated existing methods of identifying central mechanisms of neuromuscular fatigue and the potential mechanisms of the influence of stress on neuromuscular fatigue. We found that the influence of stress on the activity of the prefrontal cortex, which are also involved in exercise regulation, may contribute to exacerbated fatigue under stress. We also found that the traditional methods involve the synchronized use of transcranial magnetic stimulation, peripheral nerve stimulation, and electromyography to identify the contribution of supraspinal fatigue, through measures such as voluntary activation, motor evoked potential, and silent period. However, these popular techniques are unable to provide information about neural alterations upstream of the descending drive that may contribute to supraspinal fatigue development. To address this gap, we propose that functional brain imaging techniques, which provide insights on activation and information flow between brain regions, need to be combined with the traditional measures of measuring central fatigue to fully understand the mechanisms behind the influence of stress on fatigue.

Specific modulation of spinal and cortical excitabilities during lengthening and shortening submaximal and maximal contractions in plantar flexor muscles

2014 ◽  
Vol 117 (12) ◽  
pp. 1440-1450 ◽  
Author(s):  
Julien Duclay ◽  
Benjamin Pasquet ◽  
Alain Martin ◽  
Jacques Duchateau
Keyword(s):  
Muscle Activation ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Plantar Flexor ◽  
Lengthening Contractions ◽  
Flexor Muscles ◽  
Plantar Flexor Muscles

This study investigated the influence of the torque produced by plantar flexor muscles on cortical and spinal excitability during lengthening and shortening voluntary contractions. To that purpose, modulations of motor-evoked potential (MEP) and Hoffmann (H) reflex were compared in the soleus (SOL) and medial gastrocnemius (MG) during anisometric submaximal and maximal voluntary contraction (MVC) of the plantar flexor muscles. For the submaximal shortening and lengthening contractions, the target torque was set at 50% of their respective MVC force. The results indicate that the amplitudes of both MEP and H-reflex responses, normalized to the maximal M wave, were significantly ( P < 0.05) lower during lengthening compared with shortening submaximal contraction. For these two parameters, the reduction reached, respectively, 22.1 and 31.9% for the SOL and 34.5 and 29.3% for the MG. During MVC, normalized MEP and H reflex of the SOL were both reduced significantly by 19.9% ( P < 0.05) and 29.9% ( P < 0.001) during lengthening and shortening contraction, respectively, whereas no significant change ( P > 0.05) was observed for MG. In addition, the silent period in the ongoing electromyogram (EMG) activity following the MEP was significantly ( P < 0.01) briefer during lengthening than shortening contractions but did not differ ( P > 0.05) between contraction intensities and muscles. Together, these results indicate that cortical and spinal mechanisms involved in the modulation of muscle activation during shortening and lengthening contractions differ between synergistic muscles according to the torque produced. Data further document previous studies reporting that the specific modulation of muscle activation during lengthening contraction is not torque dependent.

Increased ventilation does not impair maximal voluntary contractions of the elbow flexors

2008 ◽  
Vol 104 (6) ◽  
pp. 1674-1682 ◽  
Author(s):  
Janette L. Smith ◽  
Jane E. Butler ◽  
Peter G. Martin ◽  
Rachel A. McBain ◽  
Janet L. Taylor
Keyword(s):  
Exercise Performance ◽  
Voluntary Contraction ◽  
Elbow Flexor ◽  
Voluntary Activation ◽  
Neural Drive ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Muscle Groups ◽  
Voluntary Contractions ◽  
Limb Exercise

Exercise performance is impaired by increased respiratory work, yet the mechanism for this is unclear. This experiment assessed whether neural drive to an exercising muscle was affected by cortically driven increases in ventilation. On each of 5 days, eight subjects completed a 2-min maximal voluntary contraction (MVC) of the elbow flexor muscles, followed by 4 min of recovery, while transcranial magnetic stimulation tested for suboptimal neural drive to the muscle. On 1 day, subjects breathed without instructions under normocapnia. During the 2-min MVC, ventilation was ∼3.5 times that at rest. On another day, subjects breathed without instruction under hypercapnia. During the 2-min MVC, ventilation was ∼1.5 times that on the normocapnic day. On another 2 days under normocapnia, subjects voluntarily matched their breathing to the uninstructed breathing under normocapnia and hypercapnia using target feedback of the rate and inspiratory volume. On a fifth day under normocapnia, the volume feedback was set to each subject's vital capacity. On this day, ventilation during the 2-min MVC was approximately twice that on the uninstructed normocapnic day (or ∼7 times rest). The experimental manipulations succeeded in producing voluntary and involuntary hyperpnea. However, maximal voluntary force, fatigue and voluntary activation of the elbow flexor muscles were unaffected by cortically or chemically driven increases in ventilation. Results suggest that any effects of increased respiratory work on limb exercise performance are not due to a failure to drive both muscle groups optimally.

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

2003 ◽  
Vol 95 (1) ◽  
pp. 373-384 ◽  
Author(s):  
Evangelos A. Christou ◽  
Minoru Shinohara ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Eccentric Contractions ◽  
Emg Activity ◽  
Target Velocity ◽  
Movement Velocity ◽  
Movement Accuracy ◽  
Old Adults ◽  
Emg Amplitude ◽  
First Dorsal Interosseus ◽  
Voluntary Contractions

The purpose of the study was to assess the effect of movement velocity on the relation between fluctuations in acceleration and the ability to achieve a target velocity during voluntary contractions performed by young (29.5 ± 4.3 yr) and old (74.9 ± 6.2 yr) adults. Subjects performed concentric and eccentric contractions with the first dorsal interosseus muscle while lifting a submaximal load (15% of maximum) at six movement velocities (0.03–1.16 rad/s). Fluctuations in acceleration, the accuracy of matching the target velocity, and electromyographic (EMG) activity were determined from three trials for each contraction type and movement velocity. The fluctuations in acceleration increased with movement velocity for both concentric and eccentric contractions, but they were greatest during fast eccentric contractions (∼135%) when there was stronger modulation of acceleration in the 5- to 10-Hz bandwidth. Nonetheless, EMG amplitude for first dorsal interosseus increased with movement velocity only for concentric and not eccentric contractions. Consistent with the minimum variance theory, movement accuracy was related to the fluctuations in acceleration for both types of contractions in all subjects. For a given level of fluctuations in acceleration, however, old subjects were three times less accurate than young subjects. Although the EMG amplitude at each speed was similar for young and old adults, only the young adults modulated the power in the EMG spectrum with speed. Thus the fluctuations in acceleration during voluntary contractions had a more pronounced effect on movement accuracy for old adults compared with young adults, probably due to factors that influenced the frequency-domain characteristics of the EMG.

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