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Kazunori Nosaka - One of the best experts on this subject based on the ideXlab platform.
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contralateral repeated bout effect of eccentric exercise of the Elbow Flexors
Medicine and Science in Sports and Exercise, 2016Co-Authors: Trevor C Chen, Hsinlian Chen, Mingju Lin, Kazunori NosakaAbstract:ABSTRACTPurposeThis study compared the magnitude of the repeated bout effect (RBE) for different time intervals between two bouts of eccentric exercise of the Elbow Flexors to better understand the contralateral RBE (CL-RBE).MethodsUntrained young men (22.0 ± 1.8 yr) were allocated to either a contr
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Differences in post-exercise T2 relaxation time changes between eccentric and concentric contractions of the Elbow Flexors.
European Journal of Applied Physiology, 2016Co-Authors: Eisuke Ochi, Yosuke Tsuchiya, Kazunori NosakaAbstract:Purpose This study compared maximal eccentric (ECC) and concentric (CON) contractions of the Elbow Flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage.
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changes in the number of circulating cd34 cells after eccentric exercise of the Elbow Flexors in relation to muscle damage
Journal of Sport and Health Science, 2015Co-Authors: Hoseong Lee, Makii Muthalib, Takayuki Akimoto, Kazunori NosakaAbstract:Background: It has been reported that strenuous exercise increases the number of bone marrow-derived progenitor cells such as CD34 þ cells in the blood, but no previous studies have investigated the changes in circulating CD34 þ cells following resistance exercise. This study tested the hypothesis that the number of CD34 þ cells in the blood would increase after eccentric exercise of the Elbow Flexors, but decrease in recovery, and the magnitude of the changes would be dependent on the magnitude of muscle damage. Methods: Nine men (28.0 � 6.6 years) performed exercises consisting of 10 sets of six maximal voluntary eccentric contractions of the Elbow Flexors with their non-dominant arm. Six of them performed the same exercise with the same arm 4 weeks later. Changes in indirect markers of muscle damage were measured before, within 10 min after, and at 24, 48, 72, and 96 h after eccentric exercise. Differential leukocyte counts (total leukocytes, neutrophils, lymphocytes, monocytes) and CD34 þ cells in the blood were measured before, immediately after, and at 2, 24, 48, 72, and 96 h following the exercises. Results: After eccentric exercise, significant (p < 0.05) decreases in maximal voluntary isometric contraction torque and increases in delayed onset muscle soreness and plasma creatine kinase activity were observed. However, no significant changes in leukocytes and CD34 þ cells were evident. The changes in muscle damage markers were significantly (p < 0.05) smaller following the second exercise session as compared with the first exercise session, but the changes in leukocytes and CD34 þ cells were not significantly different between sessions. Conclusion: These results did not support the hypothesis, and showed that eccentric exercise-induced muscle damage to the Elbow Flexors did not influence the number of circulating CD34 þ cells.
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comparison in responses to maximal eccentric exercise between Elbow Flexors and knee extensors of older adults
Journal of Science and Medicine in Sport, 2014Co-Authors: Felipe Romano Damas Nogueira, Kazunori Nosaka, Cleiton Augusto Libardi, Felipe C Vechin, Claudia Regina Cavaglieri, Mara Patricia Traina ChaconmikahilAbstract:Abstract Objectives To compare the susceptibility of Elbow Flexors (EF) and knee extensors (KE) to eccentric exercise-induced muscle damage in older individuals, since ageing could modulate the difference in the susceptibility to muscle damage between muscles. Design Cross-sectional and cross-over study design. Methods Eight older (61.6 ± 1.8 years) adults performed 5 sets of 6 maximal isokinetic (90° s −1 ) eccentric contractions of the EF (range of motion: 80–20°) and KE (30–90°) with the non-dominant limb in a randomised, counterbalanced order with 2 weeks between bouts. Maximal voluntary isometric (MVC-ISO) and concentric contraction torque, optimum angle, range of motion (ROM), muscle soreness and serum creatine kinase (CK) activity were measured before, immediately after (except CK), and 24, 48, 72 and 96 h following exercise. Normalised changes in the variables following exercise were compared between EF and KE by a mixed model analysis of variance. Results Only MVC-ISO and ROM demonstrated significant group effects ( p p > 0.05) were found between EF and KE for any of the dependent variables changes. Conclusions These results suggest that the KE of older adults are relatively as susceptible to muscle damage as their EF, or at the very least, the difference between EF and KE are small for older adults.
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do dominant and non dominant arms respond similarly to maximal eccentric exercise of the Elbow Flexors
Journal of Science and Medicine in Sport, 2013Co-Authors: Michael J Newton, Dale W. Chapman, Paul Sacco, Kazunori NosakaAbstract:Abstract Objectives Two common models to investigate the effect of interventions on muscle damage include using two groups in which one group receives an intervention while the other acts as control, and using contralateral limbs of one group. The latter model is based on the assumption that changes in markers of muscle damage are similar between limbs, but this has not been examined systematically. Design This study compared changes in muscle damage markers between dominant and non-dominant arms following maximal eccentric exercise of the Elbow Flexors. Methods Eighteen men performed 60 maximal eccentric Elbow flexions of each arm separated by 4 weeks with the order of testing between arms randomised. Maximal voluntary isometric torque, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and muscle soreness before and for 7 days following exercise were compared between arms using two-way repeated measures ANOVA. Results No significant differences between arms were evident for any of the markers, but significant ( P Conclusions These results show that the order affected the responses of dominant and non-dominant arms to the eccentric exercise; however, the contralateral limb design appears to be usable if bout order is counterbalanced and randomised among participants.
Simon C. Gandevia - One of the best experts on this subject based on the ideXlab platform.
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effects of aging and sex on voluntary activation and peak relaxation rate of human Elbow Flexors studied with motor cortical stimulation
Age, 2013Co-Authors: Joery P Molenaar, Chris J. Mcneil, Simon C. Gandevia, Marlous S BrediusAbstract:Data are equivocal on whether voluntary activation is preserved or decreased in old compared to young adults. Further, data are scant on the effect of age on the rate of muscle relaxation when the muscle is contracting voluntarily. Assessment of both measures with transcranial magnetic stimulation (TMS) yields information which cannot be obtained with traditional peripheral nerve stimulation. Hence, voluntary activation and peak relaxation rate of the Elbow Flexors were assessed with TMS during repeated maximal efforts in 30 men and 28 women between the ages of 22–84 years. Voluntary activation was similar for the two sexes (P = 0.154) and was not affected by age in men (96.2 ± 2.7 %; P = 0.887) or women (95.1 ± 3.0 %; P = 0.546). Men had a significantly faster peak rate of relaxation than women in absolute units (−880.0 ± 223.2 vs. −360.2 ± 78.5 Nm/ s, respectively; P < 0.001) and when normalized to subject strength (−12.5 ± 2.1 vs. −8.7 ± 1.0 s−1, respectively; P < 0.001). Absolute and normalized relaxation rates slowed with age in men (P = 0.002 and P = 0.006, respectively), but not women (P = 0.142 and P = 0.950, respectively). Across the age range studied, all subjects, regardless of age or sex, were able to achieve high voluntary activation scores for the Elbow Flexors (~95 %). In contrast, peak relaxation rate was markedly faster in men than women and slowed with age in men but not women. Normalization of relaxation rates to strength did not affect the influence of age or sex.
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firing of antagonist small diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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altered responses of human Elbow Flexors to peripheral nerve and cortical stimulation during a sustained maximal voluntary contraction
Experimental Brain Research, 1999Co-Authors: Janet L. Taylor, Jane E Butler, Simon C. GandeviaAbstract:The short-latency electromyographic response evoked by transcranial magnetic stimulation (MEP) increases in size during fatigue, but the mechanisms are unclear. Because large changes occur in the muscle action potential, we tested whether changes in the response to stimulation of the peripheral motor nerve could fully account for the increase in the MEP. Subjects (n=8) performed sustained maximal voluntary contractions (MVCs) of the right Elbow Flexors for 2 min. During the contraction, the MEP and the response to supramaximal stimulation of motor-nerve fibres in the brachial plexus were alternately recorded. During the contraction, responses to motor-nerve stimulation increased in area by 87±35% (mean±SD) in the biceps brachii and 74±30% in the brachioradialis, but the area of the MEPs increased by 153±86% and 175±122%, respectively. Thus, the increase in the MEP was greater than the increase in the peripheral M-wave. The onset latency of the MEP in the biceps brachii increased by 0.7±0.6 ms (range: –0.2 to 1.9 ms) during the sustained contraction. A smaller increase occurred in response to peripheral nerve stimulation (0.3±0.3 ms; from –0.3 to 0.9 ms). In the contralateral Elbow Flexors, neither responses to transcranial magnetic stimulation nor responses to motor-nerve stimulation changed in size or latency. During the sustained contraction, the short silent period after stimulation of the peripheral nerve (48±5 ms in biceps brachii and 48±4 ms in brachioradialis) increased in duration by about 12 ms (to 61±12 ms and 60±9 ms, respectively), whereas the silent period following transcranial magnetic stimulation increased from 238±39 ms in biceps brachii and 243±34 ms in brachioradialis to 325±41 ms and 343±42 ms, respectively. During a sustained MVC, while the motor responses to peripheral and to cortical stimulation grow concurrently, growth of the MEP cannot be entirely accounted for by changes in the muscle action potential. Hence, some of the increase in MEP size during fatigue must reflect changes in the central nervous system. Increased latency of the MEPs and lengthening of the peripherally evoked silent period are consistent with decreased excitability of the alpha motoneurone pool. Thus, an increased response from the motor cortex to the magnetic stimulus remains a likely contributor to the increase in the size of the MEP in fatigue.
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muscle force perceived effort and voluntary activation of the Elbow Flexors assessed with sensitive twitch interpolation in fibromyalgia
The Journal of Rheumatology, 1996Co-Authors: T A Miller, G M Allen, Simon C. GandeviaAbstract:Objective. To measure maximal voluntary strength and central activation without fatigue, and to assess both peripheral and central components of muscle fatigue of the Elbow flexor muscles, during exercise, in a group of patients with fibromyalgia (FM) (n = 11). Results are compared with data from control subjects (n = 36). Methods. Maximal voluntary activation and strength of Elbow Flexors were quantified using twitch interpolation during attempted maximal isometric contractions both in unfatigued muscles and during fatigue produced by 45 min of submaximal exercise. Results. Maximal voluntary strength of the Elbow Flexors before and during exercise was within the normal range. Central fatigue did not develop to a greater extent in the patient group. No patient had a decline in twitch amplitude during exercise below the 95% confidence limit for the decline in control subjects. However, the increment in perceived effort (Borg Scale) was abnormally large in 5 patients during the fatiguing exercise. Conclusion. Neither poor motivation, reflex pain inhibition, nor muscle contractile failure are important in the pathogenesis of fatigue in patients with FM. However, the subjective response to exercise is commonly excessive.
Janet L. Taylor - One of the best experts on this subject based on the ideXlab platform.
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firing of antagonist small diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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altered responses of human Elbow Flexors to peripheral nerve and cortical stimulation during a sustained maximal voluntary contraction
Experimental Brain Research, 1999Co-Authors: Janet L. Taylor, Jane E Butler, Simon C. GandeviaAbstract:The short-latency electromyographic response evoked by transcranial magnetic stimulation (MEP) increases in size during fatigue, but the mechanisms are unclear. Because large changes occur in the muscle action potential, we tested whether changes in the response to stimulation of the peripheral motor nerve could fully account for the increase in the MEP. Subjects (n=8) performed sustained maximal voluntary contractions (MVCs) of the right Elbow Flexors for 2 min. During the contraction, the MEP and the response to supramaximal stimulation of motor-nerve fibres in the brachial plexus were alternately recorded. During the contraction, responses to motor-nerve stimulation increased in area by 87±35% (mean±SD) in the biceps brachii and 74±30% in the brachioradialis, but the area of the MEPs increased by 153±86% and 175±122%, respectively. Thus, the increase in the MEP was greater than the increase in the peripheral M-wave. The onset latency of the MEP in the biceps brachii increased by 0.7±0.6 ms (range: –0.2 to 1.9 ms) during the sustained contraction. A smaller increase occurred in response to peripheral nerve stimulation (0.3±0.3 ms; from –0.3 to 0.9 ms). In the contralateral Elbow Flexors, neither responses to transcranial magnetic stimulation nor responses to motor-nerve stimulation changed in size or latency. During the sustained contraction, the short silent period after stimulation of the peripheral nerve (48±5 ms in biceps brachii and 48±4 ms in brachioradialis) increased in duration by about 12 ms (to 61±12 ms and 60±9 ms, respectively), whereas the silent period following transcranial magnetic stimulation increased from 238±39 ms in biceps brachii and 243±34 ms in brachioradialis to 325±41 ms and 343±42 ms, respectively. During a sustained MVC, while the motor responses to peripheral and to cortical stimulation grow concurrently, growth of the MEP cannot be entirely accounted for by changes in the muscle action potential. Hence, some of the increase in MEP size during fatigue must reflect changes in the central nervous system. Increased latency of the MEPs and lengthening of the peripherally evoked silent period are consistent with decreased excitability of the alpha motoneurone pool. Thus, an increased response from the motor cortex to the magnetic stimulus remains a likely contributor to the increase in the size of the MEP in fatigue.
Chris J. Mcneil - One of the best experts on this subject based on the ideXlab platform.
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the effects of forearm position and contraction intensity on cortical and spinal excitability during a submaximal force steadiness task of the Elbow Flexors
Journal of Neurophysiology, 2020Co-Authors: Alexandra F Yacyshyn, Jennifer M Jakobi, Samantha L Kuzyk, Chris J. McneilAbstract:To address conflicting reports about the effect of forearm position on spinal and cortical excitability of the Elbow Flexors, we examine the influence of contraction intensity. For the first time, ...
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effects of aging and sex on voluntary activation and peak relaxation rate of human Elbow Flexors studied with motor cortical stimulation
Age, 2013Co-Authors: Joery P Molenaar, Chris J. Mcneil, Simon C. Gandevia, Marlous S BrediusAbstract:Data are equivocal on whether voluntary activation is preserved or decreased in old compared to young adults. Further, data are scant on the effect of age on the rate of muscle relaxation when the muscle is contracting voluntarily. Assessment of both measures with transcranial magnetic stimulation (TMS) yields information which cannot be obtained with traditional peripheral nerve stimulation. Hence, voluntary activation and peak relaxation rate of the Elbow Flexors were assessed with TMS during repeated maximal efforts in 30 men and 28 women between the ages of 22–84 years. Voluntary activation was similar for the two sexes (P = 0.154) and was not affected by age in men (96.2 ± 2.7 %; P = 0.887) or women (95.1 ± 3.0 %; P = 0.546). Men had a significantly faster peak rate of relaxation than women in absolute units (−880.0 ± 223.2 vs. −360.2 ± 78.5 Nm/ s, respectively; P < 0.001) and when normalized to subject strength (−12.5 ± 2.1 vs. −8.7 ± 1.0 s−1, respectively; P < 0.001). Absolute and normalized relaxation rates slowed with age in men (P = 0.002 and P = 0.006, respectively), but not women (P = 0.142 and P = 0.950, respectively). Across the age range studied, all subjects, regardless of age or sex, were able to achieve high voluntary activation scores for the Elbow Flexors (~95 %). In contrast, peak relaxation rate was markedly faster in men than women and slowed with age in men but not women. Normalization of relaxation rates to strength did not affect the influence of age or sex.
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firing of antagonist small diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
David S. Kennedy - One of the best experts on this subject based on the ideXlab platform.
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firing of antagonist small diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.
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Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of Elbow Flexors
The Journal of Physiology, 2013Co-Authors: David S. Kennedy, Chris J. Mcneil, Simon C. Gandevia, Janet L. TaylorAbstract:Key points • Maintained firing of fatigue-sensitive small-diameter muscle afferents is reported to reduce voluntary activation of the homonymous (fatigued) muscle. • Our study determined if firing of fatigue-sensitive afferents from Elbow extensor muscles reduces voluntary activation and torque of the non-fatigued Elbow Flexors. • We examined voluntary activation of the Elbow Flexors by measuring changes in superimposed twitches evoked by magnetic cortical stimulation during maximal voluntary contractions. • Following a fatiguing contraction of Elbow extensors, the voluntary drive to unfatigued flexor muscles was reduced with continued activation of small-diameter muscle afferents produced by a blood pressure cuff inflated to maintain muscle ischaemia. • Continued discharge of small-diameter muscle afferents from one muscle can decrease voluntary drive to another muscle in the same limb and can reduce its maximal voluntary torque. Abstract During muscle fatigue, firing of small-diameter muscle afferents can decrease voluntary activation of the fatigued muscle. However, these afferents may have a more widespread effect on other muscles in the exercising limb. We examined if the firing of fatigue-sensitive afferents from Elbow extensor muscles in the same arm reduces torque production and voluntary activation of Elbow Flexors. In nine subjects we examined voluntary activation of Elbow Flexors by measuring changes in superimposed twitches evoked by transcranial magnetic stimulation of the motor cortex during brief (2–3 s) maximal voluntary contractions (MVC). Inflation of a blood pressure cuff following a 2-min sustained MVC blocked blood flow to the fatigued muscle and maintained firing of small-diameter afferents. After a fatiguing Elbow flexion contraction, maximal flexion torque was lower (26.0 ± 4.4%versus 67.9 ± 5.2% of initial maximal torque; means ±s.d.; P < 0.001) and superimposed twitches were larger (4.1 ± 1.1%versus 1.8 ± 0.2% ongoing MVC, P= 0.01) with than without ischaemia. After a fatiguing Elbow extensor contraction, maximal flexion torque was also reduced (82.2 ± 4.9%versus 91.4 ± 2.3% of initial maximal torque; P= 0.007), superimposed twitches were larger (2.7 ± 0.7%versus 1.3 ± 0.2% ongoing MVC; P= 0.02) and voluntary activation lower (81.6 ± 8.2%versus 95.5 ± 6.9%; P= 0.04) with than without ischaemia. After a fatiguing contraction, voluntary drive to the fatigued muscles is reduced with continued input from small-diameter muscle afferents. Furthermore, fatigue of the Elbow extensor muscles decreases voluntary drive to unfatigued Elbow Flexors of the same arm. Therefore, firing of small-diameter muscle afferents from one muscle can affect voluntary activation and hence torque generation of another muscle in the same limb.