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J Mot Behav. 2002 Mar;34(1):67-81.

Modeling variability of force during isometric contractions of the quadriceps femoris.

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Department of Kinesiology and Applied Physiology, University of Illinois at Urbana-Champaign, USA.


The authors modeled variability of force during continuous isometric contractions of the quadriceps femoris. Twenty adults (aged 25 +/- 6 years old) performed isometric leg extensions. Target forces were 11 percentages of maximum voluntary contraction (%MVC), ranging from 2 to 95%, and 5 absolute levels, from 25 to 225 N. The authors used standard deviation of absolute force, coefficient of variation, and signal-to-noise ratio as measures of variability. The results suggested a nonlinear relationship between variability and level of force, which could best be expressed as %MVC and not as absolute force. Variability for continuous isometric contractions was described best by a sigmoidal logistic function. The sigmoidal pattern of variability as a function of %MVC is consistent with physiological mechanisms.

[Indexed for MEDLINE]

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