title: Modeling variability of force during isometric contractions of the quadriceps femoris.
abstract: 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.
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Illinois at Urbana-Champaign, USA. echristo@colorado.edu
authors.forename: Evangelos A
authors.initials: EA
authors.lastname: Christou
authors.forename: Michael
authors.initials: M
authors.lastname: Grossman
authors.forename: Les G
authors.initials: LG
authors.lastname: Carlton
mesh_terms: D000328:Adult; D005269:Femur; D006801:Humans; D007537:Isometric Contraction; D016015:Logistic Models; D018482:Muscle, Skeletal / Q000502:physiology*