Endurance-exercise training adaptations in spinal motoneurones: potential functional relevance to locomotor output and assessment in humans

Power, Kevin E.; Lockyer, Evan J.; Botter, Alberto; Vieira, Taian; Button, Duane C.

doi:10.1007/s00421-022-04918-2

Cited by 17 publications

(13 citation statements)

References 81 publications

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“…Monopolar, high-density EMGs were filtered (2nd order Butterworth, 15-350 Hz) and decomposed through an automatic and validated algorithm (Holobar & Zazula, 2007), separately for each 20-s holding phase. After decomposition, the firing instants of identified MUs were used to trigger and average single differential EMGs over 30 ms epochs and inspected for spurious units (Del Vecchio et al, 2020; Power et al, 2022). Only units whose firing rates were stable over the entire contraction (pauses shorter than 500 ms) and whose action potential propagation (i.e.…”

Section: Methodsmentioning

confidence: 99%

“…After decomposition, the firing instants of identified MUs were used to trigger and average single differential EMGs over 30 ms epochs and inspected for spurious units (Del Vecchio et al, 2020;Power et al, 2022). Only units whose firing rates were stable over the entire contraction (pauses shorter than 500 ms) and whose action potential propagation (i.e.…”

Section: Motor Unit Decompositionmentioning

confidence: 99%

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Independent synaptic inputs to motor neurons driving antagonist muscles

Borzelli

Vieira

Botter

et al. 2022

Preprint

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The CNS may produce the same endpoint trajectory or torque profile with different muscle activation patterns. What differentiates these patterns is the presence of co-contraction, which does not contribute to joint torque generation but allows to modulate mechanical impedance. Whether co-contraction is controlled through the same synaptic input to motor neurons involved in generating joint torque is still unclear. We hypothesized that co-contraction is controlled through a specific synaptic input, independent from that underlying the control of torque. To test this hypothesis, we asked participants to concurrently generate multi-directional isometric forces at the hand and to modulate the co-contraction of arm muscles to displace and stabilize a virtual end-effector. The firings of motor units were identified through decomposition of High-Density EMGs collected from two antagonist muscles, Biceps Brachii and Triceps Brachii. We found significant peaks in the coherence between the neural drive to the two muscles, suggesting the existence of a common input modulating co-contraction across different exerted forces. Moreover, the within-muscle coherence computed after removing the component synchronized with the drive to the antagonist muscle or with the exerted force revealed two subsets of motor neurons that were selectively recruited to generate joint torque or modulate co-contraction. This study is the first to directly investigate the extent of shared versus independent control of antagonist muscles at the motor neuron level in a task involving concurrent force generation and modulation of co-contraction.

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Section: Methodsmentioning

confidence: 99%

Section: Motor Unit Decompositionmentioning

confidence: 99%

Independent synaptic inputs to motor neurons driving antagonist muscles

Borzelli

Vieira

Botter

et al. 2022

Preprint

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show abstract

“…Increases in physical activity levels could have varied tremendously from individual to individual, which might explain lower effects of exercise in some studies. Finally, we did not include peripheral markers of NP, i.e., motor unit remodeling, an avenue that future research should target (Alix-Fages et al, 2022;Power et al, 2022) and it remains unclear if neuroimaging and neurochemical markers are reflective of NP.…”

Section: Limitations and Future Directionsmentioning

confidence: 99%

The impact of aerobic and resistance training intensity on markers of neuroplasticity in health and disease

Hortobágyi

Vetrovsky

Balbim

et al. 2022

Ageing Research Reviews

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“…This observation carries at least 2 implications: (a) the decomposition algorithm successfully identified active MUs even after an unloading period, and (b) while comparing MUs properties before and after severe interventions, close attention has to be paid to the comparability of the decomposed pool of MUs. 50 Therefore, longitudinal tracking of the same MUs provides stronger evidence of changes affecting the single MU, although it significantly reduces the number of investigated MUs (about 20% of the total pool) and the statistical power. In addition, MUs tracking might preferentially identify MUs with a better-preserved action potential shape and, therefore, those less affected by the intervention.…”

Section: Discussionmentioning

confidence: 99%