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Distribution of motor unit potential velocities in short static and prolonged dynamic contractions at low forces: use of the within-subject's skewness and standard deviation variables.

Klaver-Król, EG, Henriquez, NR, Oosterloo, SJ, Klaver, P, Bos, JM and Zwarts, MJ (2007) Distribution of motor unit potential velocities in short static and prolonged dynamic contractions at low forces: use of the within-subject's skewness and standard deviation variables. Eur J Appl Physiol, 101 (5). pp. 647-658.

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Abstract

Behaviour of motor unit potential (MUP) velocities in relation to (low) force and duration was investigated in biceps brachii muscle using a surface electrode array. Short static tests of 3.8 s (41 subjects) and prolonged dynamic tests (prolonged tests) of 4 min (30 subjects) were performed as position tasks, applying forces up to 20% of maximal voluntary contraction (MVC). Four variables, derived from the inter-peak latency technique, were used to describe changes in the surface electromyography signal: the mean muscle fibre conduction velocity (CV), the proportion between slow and fast MUPs expressed as the within-subject skewness of MUP velocities, the within-subject standard deviation of MUP velocities [SD-peak velocity (PV)], and the amount of MUPs per second (peak frequency=PF). In short static tests and the initial phase of prolonged tests, larger forces induced an increase of the CV and PF, accompanied with the shift of MUP velocities towards higher values, whereas the SD-PV did not change. During the first 1.5-2 min of the prolonged lower force levels tests (unloaded, and loaded 5 and 10% MVC) the CV and SD-PV slightly decreased and the MUP velocities shifted towards lower values; then the three variables stabilized. The PF values did not change in these tests. However, during the prolonged higher force (20% MVC) test, the CV decreased and MUP velocities shifted towards lower values without stabilization, while the SD-PV broadened and the PF decreased progressively. It is argued that these combined results reflect changes in both neural regulatory strategies and muscle membrane state.

Item Type: Article
Authors :
NameEmailORCID
Klaver-Król, EGUNSPECIFIEDUNSPECIFIED
Henriquez, NRUNSPECIFIEDUNSPECIFIED
Oosterloo, SJUNSPECIFIEDUNSPECIFIED
Klaver, Pp.klaver@surrey.ac.ukUNSPECIFIED
Bos, JMUNSPECIFIEDUNSPECIFIED
Zwarts, MJUNSPECIFIEDUNSPECIFIED
Date : November 2007
Identification Number : https://doi.org/10.1007/s00421-007-0494-8
Uncontrolled Keywords : Adolescent, Adult, Data Interpretation, Statistical, Electromyography, Humans, Male, Middle Aged, Motor Neurons, Muscle Contraction, Muscle Fibers, Skeletal, Neural Conduction
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 10:40
Last Modified : 17 May 2017 14:51
URI: http://epubs.surrey.ac.uk/id/eprint/828720

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