Research article summary:

Motor-unit synchronization alters spike-triggered average force in simulated contractions.

Abstract Extract:
The purpose of the study was to quantify the effect of motor-unit synchronization on the spike-triggered average forces of a population of motor units. Muscle force was simulated by defining mechanical and activation characteristics of the motor units, ... (Full abstract text below)

Published 2002Jul in Journal: J Neurophysiol (Language : eng)

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1. J Neurophysiol. 2002 Jul;88(1):265-76

Motor-unit synchronization alters spike-triggered average force in simulated contractions.

Taylor AM, Steege JW, Enoka RM

Department of Kinesiology and Applied Physiology, University of Colorado, Boulder, Colorado 80309-0354, USA.

The purpose of the study was to quantify the effect of motor-unit synchronization on the spike-triggered average forces of a population of motor units. Muscle force was simulated by defining mechanical and activation characteristics of the motor units, specifying motor neuron discharge times, and imposing various levels of motor-unit synchronization. The model comprised 120 motor units. Simulations were performed for motor units 5-120 to compare the spike-triggered average responses in the presence and absence of motor-unit synchronization with the motor-unit twitch characteristics defined in the model. To synchronize motor-unit activity, selected motor-unit discharge times were adjusted; this kept the number of action potentials constant across the three levels of synchrony for each motor unit. Because there was some overlap of motor-unit twitches even at minimal discharge rates, the simulations indicated that spike-triggered averaging underestimates the twitch force of all motor units and the contraction time of motor units with contraction times longer than 49 ms. Although motor-unit synchronization increased the estimated twitch force and decreased the estimated contraction time of all motor units, spike-triggered average force changed systematically with the level of synchrony in motor units 59-120 (upper 90% of the range of twitch forces). However, the reduction in contraction time was similar for moderate and high synchrony. In conclusion, spike-triggered averaging appears to provide a biased estimate of the distribution of twitch properties for a population of motor units because twitch fusion causes an underestimation of twitch force for slow units and motor-unit synchronization causes an overestimation of force for fast motor units.

PMID : 12091552 [PubMed - Indexed for MEDLINE]

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Full Author Information

First Name	LastName	Initials
Anna M	Taylor	AM
Julie W	Steege	JW
Roger M	Enoka	RM

Affiliation: Department of Kinesiology and Applied Physiology, University of Colorado, Boulder, Colorado 80309-0354, USA.

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