title: Muscle activity while running at 20%-50% of normal body weight.
abstract: Little information exists on how body weight (BW) support influences running biomechanics. The study aim was to determine how reducing BW by 50%-80% influences muscle activity while running at different speeds. Subjects (n = 7) ran at 100%, 115%, 125% of preferred speed at 100%, 50%, 40%, 30%, 20% of BW per speed. Average (AVG) electromyography of the rectified signal was compared (within subject design; 3-speeds × 5-BW, repeated measures ANOVAs; biceps femoris [BF], rectus femoris [RF], tibialis anterior [TA], gastrocnemius [GA]). RF, BF, and GA AVG were not influenced by BW-speed interaction (p > .05) and increased across speeds (p < .05). RF and GA AVG signal was reduced as BW was reduced (p < .05), but BF only tended to be different (p = .08). TA was influenced by BW-speed interaction (p < .05) with EMG decreasing across BW (p < .05) while increasing across speeds except at 100% BW. Overall, muscle activity increased with speed and decreased by BW reductions.
authors.affiliation: Department of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada 89154, USA. john.mercer@unlv.edu
authors.forename: John A
authors.initials: JA
authors.lastname: Mercer
authors.forename: Bryon C
authors.initials: BC
authors.lastname: Applequist
authors.forename: Kenji
authors.initials: K
authors.lastname: Masumoto
mesh_terms: D000328:Adult; D001835:Body Weight / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D056865:Ideal Body Weight; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012420:Running / Q000502:physiology*