Motor unit-based synergies in a non-compartmentalized muscle

Ricotta, Joseph; Nardon, Mauro; De, Sayan D; Jiang, Jinrui; Graziani, William; Latash, Mark L.

doi:10.1007/s00221-023-06606-9

Cited by 13 publications

(11 citation statements)

References 59 publications

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“…In addition, the single‐factor ANOVA is considered a robust statistical test against violations to the normality assumption and restricts Type I error to 5% (Salkind 2007). Other studies on motor unit modes have verified the use of ANOVAs (Madarshahian & Latash 2022; Madarshahian et al., 2021; Ricotta et al., 2023).…”

Section: Methodsmentioning

confidence: 85%

“…As summarized by Ricotta, Nardon, et al. (2023), the Bernstein criteria for a synergy comprise two components: (1) a stable group of elements (e.g. muscles, motor units) that alleviates the problem of motor redundancy; and (2) a capacity to ensure dynamic stability of salient variables (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…To evaluate the capacity of a set of motor unit modes to enable dynamical stability, Ricotta, Nardon, et al. (2023) examined the modes extracted from motor units in the tibialis anterior muscle during isometric contractions when tracking a sinusoidal target. The discharge times of motor units were identified in the recordings obtained from two five‐pin electrodes placed over the muscle and converted to discharge rates that were averaged over 50 ms intervals (5% time‐windows) during each of the 17 cycles in the three 20 s epochs in a single trial.…”

Section: Discussionmentioning

confidence: 99%

“…The classification of these modules (or modes) as synergies, however, requires the demonstration that a stable set of elements ensures dynamic stability and hence serve a functionally relevant purpose. Although some studies have demonstrated that motor unit modules can satisfy the synergy criteria for some tasks (Ricotta, De, et al., 2023; Ricotta, Nardon, et al., 2023), others have not met both criteria (Del Vecchio et al., 2023; Levine et al., 2023). The motor unit modes observed in our study have not met both criteria, and thus an assessment of functional significance is not possible.…”

Section: Discussionmentioning

confidence: 99%

“…(2023) and Ricotta, Nardon, et al. (2023) identified modes derived from the discharge times of motor units in tibialis anterior during isometric contractions and found that they were able to ensure dynamical stability when participants performed a cyclical force‐tracking task. This finding was interpreted as evidence for the possibility of synergistic control at the level of motor unit modes (Madarshahian & Latash 2022).…”

Section: Introductionmentioning

confidence: 99%

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Motor unit modes in the calf muscles during a submaximal isometric contraction are changed by brief stretches

Weinman,

Del Vecchio,

Mazzo

et al. 2024

The Journal of Physiology

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The purpose of our study was to investigate the influence of a stretch intervention on the common modulation of discharge rate among motor units in the calf muscles during a submaximal isometric contraction. The current report comprises a computational analysis of a motor unit dataset that we published previously (Mazzo et al., 2021). Motor unit activity was recorded from the three main plantar flexor muscles while participants performed an isometric contraction at 10% of the maximal voluntary contraction force before and after each of two interventions. The interventions were a control task (standing balance) and static stretching of the plantar flexor muscles. A factorization analysis on the smoothed discharge rates of the motor units from all three muscles yielded three modes that were independent of the individual muscles. The composition of the modes was not changed by the standing‐balance task, whereas the stretching exercise reduced the average correlation in the second mode and increased it in the third mode. A centroid analysis on the correlation values showed that most motor units were associated with two or three modes, which were presumed to indicate shared synaptic inputs. The percentage of motor units adjacent to the seven centroids changed after both interventions: Control intervention, mode 1 decreased and the shared mode 1 + 2 increased; stretch intervention, shared modes either decreased (1 + 2) or increased (1 + 3). These findings indicate that the neuromuscular adjustments during both interventions were sufficient to change the motor unit modes when the same task was performed after each intervention. imageKey points Based on covariation of the discharge rates of motor units in the calf muscles during a submaximal isometric contraction, factor analysis was used to assign the correlated discharge trains to three motor unit modes. The motor unit modes were determined from the combined set of all identified motor units across the three muscles before and after each participant performed a control and a stretch intervention. The composition of the motor unit modes changed after the stretching exercise, but not after the control task (standing balance). A centroid analysis on the distribution of correlation values found that most motor units were associated with a shared centroid and this distribution, presumably reflecting shared synaptic input, changed after both interventions. Our results demonstrate how the distribution of multiple common synaptic inputs to the motor neurons innervating the plantar flexor muscles changes after a brief series of stretches.

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Section: Methodsmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Motor unit modes in the calf muscles during a submaximal isometric contraction are changed by brief stretches

Weinman,

Del Vecchio,

Mazzo

et al. 2024

The Journal of Physiology

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Control of motor output during steady submaximal contractions is modulated by contraction history

Darendeli,

Enoka

2024

Exp Brain Res

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The purpose of the study was to investigate the influence of contraction history on force steadiness and the associated EMG activity during submaximal isometric contractions performed with the dorsiflexor muscles. The key feature of the protocol was a triangular ramp contraction performed in the middle of a steady contraction at a lower target force. The target force during the ramp contraction was 20% MVC greater than that during the steady contraction. Thirty-seven healthy individuals (21 men and 16 women) performed the submaximal tasks with the ankle dorsiflexors. Electromyography (EMG) signals were recorded from tibialis anterior with a pair of surface electrodes. The coefficient of variation for force was significantly greater during the second steady contraction compared with the first one at each of the seven target forces (p < 0.015; d = 0.38–0.92). Although the average applied force during the steady contractions before and after the triangular contraction was the same (p = 0.563), the mean EMG amplitude for the steady contractions performed after the triangular contraction was significantly greater at each of the seven target forces (p < 0.0001; d = 0.44–0.68). Also, there were significant differences in mean EMG frequency between the steady contractions performed before and after the triangular contraction (p < 0.01; d = 0.13–0.82), except at 10 and 20% MVC force. The greater force fluctuations during a steady submaximal contraction after an intervening triangular contraction indicate a change in the discharge characteristics of the involved motor units.

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Explaining the influence of practice on the grooved pegboard times of older adults: role of force steadiness

Daneshgar,

Tvrdy,

Enoka

2024

Exp Brain Res

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Motor unit-based synergies in a non-compartmentalized muscle

Cited by 13 publications

References 59 publications

Motor unit modes in the calf muscles during a submaximal isometric contraction are changed by brief stretches

Motor unit modes in the calf muscles during a submaximal isometric contraction are changed by brief stretches

Control of motor output during steady submaximal contractions is modulated by contraction history

Explaining the influence of practice on the grooved pegboard times of older adults: role of force steadiness

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