Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of elbow flexors

Kennedy, David; McNeil, Chris J.; Gandevia, Simon C.; Taylor, Janet L.

doi:10.1113/jphysiol.2012.248559

Cited by 51 publications

(85 citation statements)

References 54 publications

(98 reference statements)

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“…Across participants, those who reported higher final perceived effort were stronger and hence had higher target torques. This relationship is consistent with an influence of fatigue-sensitive small-diameter afferents on perceived effort, as higher muscle forces lead to higher intramuscular pressure, poorer perfusion, and increased concentrations of metabolites (Kennedy et al 2013; Kennedy et al 2014; Kennedy et al 2015). However, this is unlikely to be the only factor underlying increasing effort.…”

Section: Discussionsupporting

confidence: 81%

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

et al. 2016

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This study determined whether short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) change during a sustained submaximal isometric contraction. On two days, 12 participants (6 men, 6 women) performed brief (7-s) elbow flexor contractions before and after a 10-minute fatiguing contraction; all contractions were performed at the level of integrated electromyographic activity (EMG) which produced 25% maximal unfatigued torque. During the brief 7-s and 10-minute submaximal contractions, single (test) and paired (conditioning-test) transcranial magnetic stimuli were applied over the motor cortex (5s apart) to elicit motor evoked potentials (MEPs) in biceps brachii. SICI and ICF were elicited on separate days, with a conditioning-test interstimulus interval of 2.5ms and 15ms respectively. On both days, integrated EMG remained constant while torque fell during the sustained contraction by ~51.5% from control contractions, perceived effort increased 3 fold and MVC declined by 21–22%. For SICI, the conditioned MEP during control contractions (74.1±2.5% of unconditioned MEP) increased (less inhibition) during the sustained contraction (last 2.5 min: 86.0±5.1%; P<0.05). It remained elevated in recovery contractions at 2 minutes (82.0±3.8%; P<0.05) and returned toward control at 7-mins recovery (76.3±3.2%). ICF during control contractions (conditioned MEP 129.7±4.8% of unconditioned MEP) decreased (less facilitation) during the sustained contraction (last 2.5 min: 107.6±6.8% P<0.05) and recovered to 122.8±4.3% during contractions after 2 minutes of recovery. Both intracortical inhibitory and facilitatory circuits become less excitable with fatigue when assessed during voluntary activity, but their different time courses of recovery suggest different mechanisms for the fatigue-related changes of SICI and ICF.

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Section: Discussionsupporting

confidence: 81%

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

et al. 2016

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“…; Kennedy et al . ), motor unit rotation during exercise (Bawa & Murnaghan, ), or alterations of motor unit firing rate during exercise (Bigland‐Ritchie et al . ).…”

Section: Discussionmentioning

confidence: 99%

“…; Kennedy et al . ), is likely progressively increased throughout the all‐out protocol. It may, therefore, be anticipated that the attenuation of group III/IV muscle afferent feedback will exacerbate the ATP cost of contraction only during the latter portion of the all‐out protocol, when activation of these muscle afferents is high and motor unit recruitment strategies are highly influential on exercise performance.…”

Section: Introductionmentioning

confidence: 99%

Influence of group III/IV muscle afferents on small muscle mass exercise performance: a bioenergetics perspective

Broxterman

Hureau

Layec

et al. 2018

The Journal of Physiology

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The direct influence of group III/IV muscle afferents on exercise performance remains equivocal. Therefore, all-out intermittent isometric single-leg knee-extensor exercise and phosphorous magnetic resonance spectroscopy ( P-MRS) were utilized to provide a high time resolution assessment of exercise performance and skeletal muscle bioenergetics in control conditions (CTRL) and with the attenuation of group III/IV muscle afferent feedback via lumbar intrathecal fentanyl (FENT). In both conditions, seven recreationally active men performed 60 maximal voluntary quadriceps contractions (MVC; 3 s contraction, 2 s relaxation), while knee-extensor force and P-MRS were assessed during each MVC. The cumulative integrated force was significantly greater (8 ± 6%) in FENT than CTRL for the first minute of the all-out protocol, but was not significantly different for the second to fifth minutes. Total ATP production was significantly greater (16 ± 21%) in FENT than CTRL throughout the all-out exercise protocol, due to a significantly greater anaerobic ATP production (11 ± 13%) in FENT than CTRL with no significant difference in oxidative ATP production. The ATP cost of contraction was not significantly different between FENT and CTRL for the first minute of the all-out protocol, but was significantly greater (29 ± 34%) in FENT than in CTRL for the second to fifth minutes. These findings reveal that group III/IV muscle afferents directly limit exercise performance during small muscle mass exercise, but, due to their critical role in maintaining skeletal muscle contractile efficiency, with time, the benefit from muscle afferent attenuation is negated.

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“…The reduced exercise capacity and accelerated neuromuscular fatigue within the tested muscle groups have been attributed to central inhibitory factors mediated by afferent feedback from pre‐fatigued muscles (Kennedy et al . ; Sidhu et al . ; Halperin et al .…”

Section: Introductionmentioning

confidence: 99%

Effects of pre‐induced fatigue vs. concurrent pain on exercise tolerance, neuromuscular performance and corticospinal responses of locomotor muscles

Aboodarda

Iannetta

Emami

et al. 2020

The Journal of Physiology

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Key points Fatigue and muscle pain induced in a remote muscle group has been shown to alter neuromuscular performance in exercising muscles. Inhibitory neural feedback associated with activation of mechano‐ and metabo‐sensitive muscle afferents has been implicated in this phenomenon. The present study aimed to quantify and compare the effects of pre‐induced fatigue and concurrent rising pain (evoked by muscle ischaemia) on the contralateral leg exercise capacity, neuromuscular performance, and corticomotor excitability and inhibition of knee extensor muscles. Pre‐induced fatigue in one leg had a greater detrimental effect than the concurrent rising pain on the contralateral limb cycling capacity. Furthermore, pre‐induced fatigue, but not concurrent rising pain, reduced corticospinal inhibition recorded from tested contralateral muscles. Regardless of the origin or mechanisms modulating sensory afferents during single‐leg cycling exercise (i.e. pre‐induced fatigue vs. concurrent rising pain), the limit of exercise tolerance remained the same and exercise was terminated upon achievement of a sensory tolerance limit. Abstract Individuals often need to maintain voluntary contractions during high intensity exercise in the presence of fatigue and pain. This investigation examined the effects of pre‐induced fatigue and concurrent rising pain (evoked by muscle ischaemia) in one leg on motor fatigability and corticospinal excitability/inhibition of the contralateral limb. Twelve healthy males undertook four experimental protocols including unilateral cycling to task failure at 80% of peak power output with: (i) the right‐leg (RL); (ii) the left‐leg (LL); (iii) RL immediately preceded by LL protocol (FAT‐RL); and (iv) RL when blood flow was occluded in the contralateral (left) leg (PAIN‐RL). Participants performed maximal and submaximal 5 s right‐leg knee extensions during which transcranial magnetic and femoral nerve electrical stimuli were delivered to elicit motor‐evoked and compound muscle action potentials, respectively. The pre‐induced fatigue reduced the right leg cycling time‐to‐task failure (mean ± SD; 332 ± 137 s) to a greater extent than concurrent pain (460 ± 158 s), compared to RL (580 ± 226 s) (P < 0.001). The maximum voluntary contraction force declined less following FAT‐RL (P < 0.019) and PAIN‐RL (P < 0.032) compared to RL. Voluntary activation declined and the corticospinal excitability recorded from knee extensors increased similarly after the three conditions (P < 0.05). However, the pre‐induced fatigue, but not concurrent pain, reduced corticospinal inhibition compared to RL (P < 0.05). These findings suggest that regardless of the origin and/or mechanisms modulating sensory afferent feedback during single‐leg cycling (e.g. pre‐induced fatigue vs. concurrent rising pain), the limit of exercise tolerance remains the same, suggesting that exercise will be terminated upon achievement of sensory tolerance limit.

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Firing of antagonist small‐diameter muscle afferents reduces voluntary activation and torque of elbow flexors

Cited by 51 publications

References 54 publications

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

Influence of group III/IV muscle afferents on small muscle mass exercise performance: a bioenergetics perspective

Effects of pre‐induced fatigue vs. concurrent pain on exercise tolerance, neuromuscular performance and corticospinal responses of locomotor muscles

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