The Effects of Sex and Motoneuron Pool on Central Fatigue

Yacyshyn, Alexandra F.; Nettleton, Jane; McNeil, Chris J.

doi:10.1249/mss.0000000000001536

Cited by 11 publications

(8 citation statements)

References 35 publications

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“…The changes during the 2-min EF MVC in this study are in agreement with previouslyreported changes from the beginning to end of 2-min MVCs [e.g. (Butler et al, 2003;Taylor et al, 1996) Of the studies that have employed 2-min MVCs, (Butler et al, 2003;McNeil et al, 2009;Taylor et al, 1996;Taylor et al, 1999;Yacyshyn et al, 2018) only McNeil et al (2009) has reported a change (i.e. increase in SPTMS duration from control MVCs at 9 s) between pre-exercise control contractions and the first measurements (i.e.…”

Section: Upper Limbssupporting

confidence: 92%

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Sustained Maximal Voluntary Contractions Elicit Different Neurophysiological Responses in Upper- and Lower-Limb Muscles in Men

et al. 2019

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This study compared the effects of fatigue on corticospinal responsiveness in the upper-and lower-limb muscles of the same participants. Seven healthy males performed a 2-min maximal voluntary isometric contraction of the elbow flexors or knee extensors on four separate days. Electromyographic responses were elicited by nerve stimulation (maximal Mwave) in all sessions and by transcranial magnetic stimulation (motor-evoked potential; silent period) and spinal tract stimulation (cervicomedullary or thoracic motor-evoked potentials; silent period) in one session each per limb. During sustained maximal voluntary contractions, motor-evoked potential area normalised to M-waves increased from baseline in biceps brachii (155 ± 55%) and rectus femoris (151 ± 44%) (both p ≤ 0.045). At the end of maximal voluntary contractions, spinal tract motor-evoked potential area normalised to M-waves was smaller than baseline in biceps brachii (74 ± 23%; p = 0.012) but not rectus femoris (108 ± 40%; p = 0.999). The ratio of motor-evoked potential to spinal tract-evoked potential areas increased dramatically from 90 to 115 s in biceps brachii (p = 0.001) but not in rectus femoris (p = 0.999). Silent period durations increased similarly in both muscles (p ≤ 0.008) after transcranial and spinal stimulation. Sustained maximal contractions elicit different neurophysiological adjustments in upper-and lower-limb muscles. Specifically, motoneuronal excitability was reduced in biceps brachii, but not in rectus femoris, and this reduction required greater compensatory adjustments from the motor cortex. Therefore, changes in cortical and spinal excitability during sustained maximal exercise are likely specific to the muscle performing the task.

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Section: Upper Limbssupporting

confidence: 92%

“…Two-minute MVCs have been frequently used to assess neuromuscular fatigue in both the upper [e.g. (Butler et al, 2003;Taylor et al, 1996;Yacyshyn et al, 2018)] and lower [e.g. (Goodall et al, 2009;Kennedy et al, 2016)] limbs.…”

Section: Introductionmentioning

confidence: 99%

Sustained Maximal Voluntary Contractions Elicit Different Neurophysiological Responses in Upper- and Lower-Limb Muscles in Men

et al. 2019

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“…Although our study provides evidence that fatigue and recovery of motoneuron excitability depends on the muscle performing the exercise in young men, women exhibit different fatigue 483 characteristics than men (Hunter 2009) and are generally less fatigable than men for sustained isometric contractions (Hunter 2014). Nevertheless, recent evidence shows no effect of sex on motoneuron excitability after an isometric sustained contractions (Yacyshyn et al 2018).…”

Section: Limitations 481contrasting

confidence: 53%

Spinal contribution to neuromuscular recovery differs between elbow-flexor and knee-extensor muscles after a maximal sustained fatiguing task

Vernillo

Temesi

Martin

et al. 2020

Journal of Neurophysiology

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Data from studies of elbow-flexor (EF) or knee-extensor (KE) muscles suggest that a fatigue-related decrease in motoneuron excitability only occurs in EF. It is unknown how motoneuron excitability changes after sustained fatiguing maximal voluntary isometric contractions (MVICs) in EF and KE in the same participants. In two sessions, eight healthy men performed a 2-min MVIC of EF or KE to induce fatigue with brief MVICs before and six times after the 2-min MVIC. Electromyographic responses elicited by corticospinal tract stimulation at the transmastoid [cervicomedullary motor-evoked potential (CMEP)] or thoracic [thoracic motor-evoked potential (TMEP)] level were recorded from EF and KE, respectively. To account for muscle excitability, CMEPs and TMEPs were normalized to maximal M-wave (Mmax) elicited by peripheral nerve stimulation during each brief MVIC. Immediately after the 2-min MVIC, biceps brachii and brachioradialis CMEP/Mmax were 88% (SD 11%) (P = 0.026) and 87% (SD 12%) (P = 0.029) of pre-MVIC values, respectively, and remained lower than PRE after 5 s of recovery [91% (SD 8%), P = 0.036 and 87% (SD 13%), P = 0.046, respectively]. No subsequent time points differed from PRE (all P ³ 0.253). TMEP/Mmax for rectus femoris and vastus lateralis were not different from PRE at any time during the recovery period (all P > 0.050). A different recovery pattern in motoneuron excitability occurred in EF as it recovered by 60 s whereas KE motoneurons were unaffected by the fatiguing task. The present findings may contribute to better understand muscle-specific neurophysiological differences in spinal excitability.

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“…Finally, although the influence of sex on the development of neuromuscular fatigue during exercise remains unclear (26,45,53), exercise pressor reflex function has been documented to differ between men and women (20,30). Therefore, as afferent blockade might have different cardiovascular consequences in men versus women, we chose to limit this investigation to male participants.…”

Section: Significance Of Group Iii/iv-mediated Limitation To Endurance Exercisementioning

confidence: 99%

Pharmacological attenuation of group III/IV muscle afferents improves endurance performance when oxygen delivery to locomotor muscles is preserved

Hureau

Weavil

Thurston

et al. 2019

Journal of Applied Physiology

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We sought to investigate the role of group III/IV muscle afferents in limiting endurance exercise performance, independently of their role in optimizing locomotor muscle O2 delivery. While breathing 100% O2 to ensure a similar arterial O2 content ([Formula: see text]) in both trials, eight male cyclists performed 5-km time trials under control conditions (HCTRL) and with lumbar intrathecal fentanyl (HFENT) impairing neural feedback from the lower limbs. After each time trial, common femoral artery blood flow (FBF) was quantified (Doppler ultrasound) during constant-load cycling performed at the average power of the preceding time trial. The assessment of end-tidal gases, hemoglobin content and saturation, and FBF facilitated the calculation of leg O2 delivery. Locomotor muscle activation during cycling was estimated from vastus lateralis EMG. With electrical femoral nerve stimulation, peripheral and central fatigue were quantified by pre- to postexercise decreases in quadriceps twitch torque (ΔQtw) and voluntary activation (ΔVA), respectively. FBF (~16 mL·min−1·W−1; P = 0.6), [Formula: see text] (~24 mL O2/dL; P = 0.9), and leg O2 delivery (~0.38 mL O2·min−1·W−1; P = 0.9) were not different during HCTRL and HFENT. Mean power output and time to completion were significantly improved by 9% (~310 W vs. ~288 W) and 3% (~479 s vs. ~463 s), respectively, during HFENT compared with HCTRL. Quadriceps muscle activation was 9 ± 7% higher during HFENT compared with HCTRL ( P < 0.05). ΔQtw was significantly greater in HFENT compared with HCTRL (54 ± 8% vs. 39 ± 9%), whereas ΔVA was not different (~5%; P = 0.3) in both trials. These findings reveal that group III/IV muscle afferent feedback limits whole body endurance exercise performance and peripheral fatigue by restricting neural activation of locomotor muscle. NEW & NOTEWORTHY Group III/IV muscle afferent feedback facilitates endurance performance by optimizing locomotor muscle O2 delivery but also limits performance by restricting neural drive to locomotor muscle. To isolate the performance-limiting effect of these sensory neurons, we pharmacologically attenuated their central projection during a cycling time trial while controlling for locomotor muscle O2 delivery. With no difference in leg O2 delivery, afferent blockade attenuated the centrally mediated restriction in motoneuronal output and improved cycling performance.

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The Effects of Sex and Motoneuron Pool on Central Fatigue

Abstract: The findings do not support the concept that equivocal findings regarding sex differences in central fatigue are related to augmented effects of group III/IV afferent feedback in males compared with females.

Cited by 11 publications

References 35 publications

Sustained Maximal Voluntary Contractions Elicit Different Neurophysiological Responses in Upper- and Lower-Limb Muscles in Men

Sustained Maximal Voluntary Contractions Elicit Different Neurophysiological Responses in Upper- and Lower-Limb Muscles in Men

Spinal contribution to neuromuscular recovery differs between elbow-flexor and knee-extensor muscles after a maximal sustained fatiguing task

Pharmacological attenuation of group III/IV muscle afferents improves endurance performance when oxygen delivery to locomotor muscles is preserved

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