Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Pereira, Hugo M.; Schlinder-Delap, Bonnie; Keenan, Kevin G.; Negro, Francesco; Farina, Dario; Hyngstrom, Allison S.; Nielson, Kristy A.; Hunter, Sandra K.

doi:10.1152/japplphysiol.00821.2018

Cited by 28 publications

(26 citation statements)

References 76 publications

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“…Muscle damage resulted in increased torque variability during submaximal isometric contractions immediately post exercise, as well as 24 hours after, corroborating previous work (14,49,53,89). This behaviour was observed regardless of age and despite the greater torque variability of older adults at baseline, that has previously been related to the age-related increase in variability of the common synaptic input to motoneurons (12,76). Thus, our results suggest that control of muscle force is equally perturbed in young and older adults following damaging exercise.…”

Section: Disruptions In Motor Performance and Muscle Activitysupporting

confidence: 87%

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

Škarabot

Ansdell

Temesi

et al. 2019

Journal of Applied Physiology

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A bout of maximal lengthening contractions is known to produce muscle damage, but confers protection against subsequent damaging bouts, with both tending to be lower in older adults. Neural factors contribute to this adaptation, but the role of the corticospinal pathway remains unclear. Twelve young (27 ± 5 yr) and 11 older adults (66 ± 4 yr) performed two bouts of 60 maximal lengthening dorsiflexions 2 weeks apart. Neuromuscular responses were measured preexercise, immediately postexercise, and at 24 and 72 h following both bouts. The initial bout resulted in prolonged reductions in maximal voluntary torque (MVC; immediately postexercise onward, P < 0.001) and increased creatine kinase (from 24 h onward, P = 0.001), with both responses being attenuated following the second bout ( P < 0.015), demonstrating adaptation. Smaller reductions in MVC following both bouts occurred in older adults ( P = 0.005). Intracortical facilitation showed no changes ( P ≥ 0.245). Motor-evoked potentials increased 24 and 72 h postexercise in young ( P ≤ 0.038). Torque variability ( P ≤ 0.041) and H-reflex size ( P = 0.024) increased, while short-interval intracortical inhibition (SICI; P = 0.019) and the silent period duration (SP) decreased ( P = 0.001) in both groups immediately postexercise. The SP decrease was smaller following the second bout ( P = 0.021), and there was an association between the change in SICI and reduction in MVC 24 h postexercise in young adults ( R = −0.47, P = 0.036). Changes in neurophysiological responses were mostly limited to immediately postexercise, suggesting a modest role in adaptation. In young adults, neural inhibitory changes are linked to the extent of MVC reduction, possibly mediated by the muscle damage–related afferent feedback. Older adults incurred less muscle damage, which has implications for exercise prescription. NEW & NOTEWORTHY This is the first study to have collectively assessed the role of corticospinal, spinal, and intracortical activity in muscle damage attenuation following repeated bouts of exercise in young and older adults. Lower levels of muscle damage in older adults are not related to their neurophysiological responses. Neural inhibition transiently changed, which might be related to the extent of muscle damage; however, the role of processes along the corticospinal pathway in the adaptive response is limited.

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Section: Disruptions In Motor Performance and Muscle Activitysupporting

confidence: 87%

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

Škarabot

Ansdell

Temesi

et al. 2019

Journal of Applied Physiology

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“…We observed a main effect of sex on the variability in MUFR, such that females had greater variability in their MUFR than males in the 20% MVC condition, though this was not observed in the 50% MVC condition. Similarly, at very low contraction intensities and using high-density surface EMG, Pereira et al (2019) demonstrated females have greater oscillations in the common synaptic input than males during single-and dual-task conditions. There is a general paucity of data on sex differences in variability of MUFR at different contraction intensities, thus making the intensity-dependent sex difference observed here a novel observation that should be explored further.…”

Section: Emgmentioning

confidence: 83%

Force Control and Motor Unit Firing Behavior Following Mental Fatigue in Young Female and Male Adults

Kowalski

Anita

2020

Front. Integr. Neurosci.

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The neuromuscular mechanisms leading to impaired motor performance in the presence of mental fatigue remain unclear. It is also unknown if mental fatigue differentially impacts motor performance in males and females. The purpose of this study was to assess the impact of mental fatigue on force production and motor unit (MU) firing behavior in males and females. Methods: Nineteen participants performed 10-s isometric dorsiflexion (DF) contractions at 20 and 50% maximum voluntary contraction (MVC) before, during, and after completing 22 min of the psychomotor vigilance task (PVT), to induce mental fatigue. The DF force and indwelling MU firing behavior of the tibialis anterior (TA) was measured before and immediately following the PVT and within the first and final minutes of the PVT. Results: Force steadiness and motor unit firing rate (MUFR) variability did not change during or following the PVT at either contraction intensity (p ≥ 0.16). Overall, females had more variability than males in MUFR during the 20% MVCs (15.98 ± 2.19 vs. 13.64 ± 2.19%, p = 0.03), though no sex differences were identified during the 50% MVCs (p = 0.20). Mean MUFR decreased following mental fatigue in both sexes in the 20% MVC condition (14.79 ± 3.20 vs. 12.92 ± 2.53 Hz, p = 0.02), but only in males during the 50% MVC condition (18.65 ± 5.21 vs. 15.03 ± 2.60 Hz, p = 0.01). Conclusions: These results suggest possible sex and contraction intensity-specific neuromuscular changes in the presence of mental fatigue.

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“…These factors, amongst others, are suggested to contribute to a sex difference in force steadiness (Jakobi, Haynes, & Smart, 2018), although the authors concluded that despite a clear sex difference in steadiness, the underlying mechanisms are unclear. One recent investigation using high‐density surface electromyography (Pereira et al., 2019) demonstrated no differences in discharge rate, but showed that females experienced greater oscillations in the common synaptic input to motor units. This greater coefficient of variation in the common synaptic input has been associated with the coefficient of variation of force during sustained submaximal contractions (Farina & Negro, 2015).…”

Section: Sex Differences Within Physiological Systemsmentioning

confidence: 99%

Physiological sex differences affect the integrative response to exercise: acute and chronic implications

Ansdell

Thomas

Hicks

et al. 2020

Experimental Physiology

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213

179

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The anatomical and physiological differences between males and females are thought to determine differences in the limits of human performance. The notion of studying sex as a biological variable has recently been emphasized in the biosciences as a vital step in enhancing human health. In this review, we contend that the effects of biological sex on acute and chronic responses must be studied and accounted for when prescribing aerobic exercise, much like any intervention targeting the optimization of physiological function. Emerging evidence suggests that the response of physiological systems to exercise differs between males and females, potentially mediating the beneficial effects in healthy and clinical populations. We highlight evidence that integrative metabolic thresholds during exercise are influenced by phenotypical sex differences throughout many physiological systems. Furthermore, we discuss evidence that female skeletal muscle is more resistant to fatigue elicited by equivalent dosages of high-intensity exercise. How the different acute responses affect the long-term trainability of males and females is considered, with discussion about tailoring exercise to the characteristics of the individual presented within the context of biological sex. Finally, we highlight the influence of endogenous and exogenous sex hormones on physiological responses to exercise in females. Sex is one of many mediating influences on the outcomes of exercise, and with careful experimental designs, physiologists can advance the collective understanding of diversity in physiology and optimize outcomes for both sexes.

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Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Cited by 28 publications

References 76 publications

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

Force Control and Motor Unit Firing Behavior Following Mental Fatigue in Young Female and Male Adults

Physiological sex differences affect the integrative response to exercise: acute and chronic implications

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