Half marathon induces changes in central control and peripheral properties of individual motor units in master athletes

Cogliati, Marta; Cudicio, Alessandro; Martinez‐Valdes, Eduardo; Tarperi, Cantor; Schena, Federico; Orizio, Claudio; Negro, Francesco

doi:10.1016/j.jelekin.2020.102472

Cited by 20 publications

(19 citation statements)

References 47 publications

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“…The maintained DR across ankle plantar-flexion angles can be explained by differences in twitch force and motor unit recruitment at different joint angles. Recent research has shown that changes in twitch force can affect motor unit firing frequency; therefore, low twitch forces can be compensated by increasing DR and high twitch forces, require less DR to maintain the required force level (Inglis et al 2011 ; Martinez‐Valdes et al 2020a , b ; Cogliati et al 2020a ). Considering this observation, previous studies have reported that whole-muscle stimulation at low rates generates the maximal force at longer muscle lengths.…”

Section: Discussionmentioning

confidence: 99%

“…8 The bar plot shows the mean and standard deviation of the twitch area slope across the three positions for the stimulated contractions, short (orange), optimal (blue), and long (green) length. The statistical difference across muscle length is reported (P < 0.01) has shown that changes in twitch force can affect motor unit firing frequency; therefore, low twitch forces can be compensated by increasing DR and high twitch forces, require less DR to maintain the required force level (Inglis et al 2011;Martinez-Valdes et al 2020a, b;Cogliati et al 2020a). Considering this observation, previous studies have reported that whole-muscle stimulation at low rates generates the maximal force at longer muscle lengths.…”

Section: The Effect Of Muscle Length On Motor Unit Firing Propertiesmentioning

confidence: 99%

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The force-generation capacity of the tibialis anterior muscle at different muscle–tendon lengths depends on its motor unit contractile properties

et al. 2021

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Purpose Muscle–tendon length can influence central and peripheral motor unit (MU) characteristics, but their interplay is unknown. This study aims to explain the effect of muscle length on MU firing and contractile properties by applying deconvolution of high-density surface EMG (HDEMG), and torque signals on the same MUs followed at different lengths during voluntary contractions. Methods Fourteen participants performed isometric ankle dorsiflexion at 10% and 20% of the maximal voluntary torque (MVC) at short, optimal, and long muscle lengths (90°, 110°, and 130° ankle angles, respectively). HDEMG signals were recorded from the tibialis anterior, and MUs were tracked by cross-correlation of MU action potentials across ankle angles and torques. Torque twitch profiles were estimated using model-based deconvolution of the torque signal based on composite MU spike trains. Results Mean discharge rate of matched motor units was similar across all muscle lengths (P = 0.975). Interestingly, the increase in mean discharge rate of MUs matched from 10 to 20% MVC force levels at the same ankle angle was smaller at 110° compared with the other two ankle positions (P = 0.003), and the phenomenon was explained by a greater increase in twitch torque at 110° compared to the shortened and lengthened positions (P = 0.002). This result was confirmed by the deconvolution of electrically evoked contractions at different stimulation frequencies and muscle–tendon lengths. Conclusion Higher variations in MU twitch torque at optimal muscle lengths likely explain the greater force-generation capacity of muscles in this position.

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Section: Discussionmentioning

confidence: 99%

Section: The Effect Of Muscle Length On Motor Unit Firing Propertiesmentioning

confidence: 99%

The force-generation capacity of the tibialis anterior muscle at different muscle–tendon lengths depends on its motor unit contractile properties

et al. 2021

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“…Fortuitously, recent advances in technology have enabled us to sample from large populations of concurrently active MUs, by using high-density surface electromyography (HDsEMG) array electrodes and blind source separation algorithms (Holobar & Zazula, 2007;Negro et al 2016) with great success (Yavuz et al 2015;Del Vecchio et al 2018;Thompson et al 2018;Cogliati et al 2020;Del Vecchio et al 2020;Hassan et al 2020;Kim et al 2020;Martinez-Valdes et al 2020). This non-invasive technology has created an opportunity to further study the age-related alterations in the neuromuscular system by sampling from many concurrently active MUs.…”

Section: Introductionmentioning

confidence: 99%

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Hassan

Fajardo

Cummings

et al. 2021

The Journal of Physiology

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support-information-section).Altamash Hassan is a biomedical engineer who earned his PhD from Northwestern University. During his time at Northwestern, he was mentored by Dr Julius P. A. Dewald, and his research investigates the neural control of movement through analyses of motor unit firing patterns in both healthy and pathological states. Investigating the effects of ageing on motor unit behaviour stemmed from an informal discussion with Dr Gregory Pearcey and provides the foundation for future investigations of interventions aimed at ameliorating motor deficits associated with ageing, and providing appropriate age-matched controls for those deficits seen in individuals post-stroke.

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“…Fortuitously, recent advances in technology have enabled us to sample from large populations of concurrently active MUs, by using high-density surface electromyography (HD-sEMG) array electrodes and blind source separation algorithms (Holobar & Zazula, 2007;Negro et al, 2016) with great success (Yavuz et al, 2015;Del Vecchio et al, 2018;Thompson et al, 2018;Cogliati et al, 2020;Del Vecchio et al, 2020;Hassan et al, 2020;Kim et al, 2020;Martinez-Valdes et al, 2020). This non-invasive technology has created an opportunity to further study the age-related alterations in the neuromuscular system by sampling from many concurrently active MUs.…”

Section: Introductionmentioning

confidence: 99%

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Hassan

Fajardo

Cummings

et al. 2021

Preprint

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Aging is a natural process that causes alterations in the neuromuscular system, which contribute to weakness and reduced quality of life. Reduced firing rates of individual motor units (MUs) likely contribute to weakness, but the mechanisms underlying reduced firing rates are not clear. Persistent inward currents (PICs) are crucial for the initiation, gain control, and maintenance of motoneuron firing, and are directly proportional to the level of monoaminergic input. Since the concentration of monoamines (i.e. serotonin and norepinephrine) are reduced with age, we sought to determine if estimates of PICs are reduced in older (>60 years old) compared to young adults (<35 years old). We decomposed MU spike trains from high-density surface electromyography over the biceps brachii and triceps brachii during isometric ramp contractions to 20% of maximum. Estimates of PICs (i.e. ΔF) were computed using the paired MU analysis technique. Regardless of the muscle, peak firing rates of older adults were reduced by ~1.6 pulses per second (pps) (P = 0.0292), and ΔF was reduced by ~1.9 pps (P < 0.0001), compared to young adults. We further found that age predicted ΔF in older adults (P = 0.0261), resulting in a reduction of ~1pps per decade, but there was no relationship in young adults (P = 0.9637). These findings suggest that PICs are reduced in older adults, and, further, age is a significant predictor of estimates of PICs in older adults. Reduced PIC magnitude represents one plausible mechanism for reduced firing rates and weakness in older individuals.

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Half marathon induces changes in central control and peripheral properties of individual motor units in master athletes

Cited by 20 publications

References 47 publications

The force-generation capacity of the tibialis anterior muscle at different muscle–tendon lengths depends on its motor unit contractile properties

The force-generation capacity of the tibialis anterior muscle at different muscle–tendon lengths depends on its motor unit contractile properties

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

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