title: Changes in force-velocity and power output of upper and lower extremity musculature in young subjects following 20 days bed rest.
abstract: Ten healthy sedentary students were exposed to 20 days bed rest (BR) to study the effect of simulated weightlessness on force(F)-velocity(V) characteristics and power(P) output of upper and lower limb movements. F, V and P were measured using a special dynamometer applicable to single joint movements [elbow flexion(EF) and extension(EE), knee flexion(KF) and extension(KE), and hip flexion] or multi-joint movements (squatting). Physiological cross-sectional areas(PCSA) of KF and KE muscles were measured by a magnetic resonance imaging technique. After BR, attenuation in P were observed in lower limb movements (decreased by 19.8-43.6% for squatting, KF and KE), in upper limb movements on the other hand, the decreases in P were not significant (approximately -5% for EF and EE). Decrease in P in lower limb were more pronounced in heavier loaded conditions which were characterized by decreases in both F and V. For KF and KE, decreases in maximal static F (-18.9 to approximately -26.8%) were more pronounced than the decreases observed in the PCSA (approximately -7%), resulting in decreases in specific tension (-12.3 to approximately -22.1%). Neural excitation potentials to generate maximal muscle tension or P might also be influenced by weightlessness.
authors.affiliation: Department of Life Sciences (Sports Sciences), The University of of Tokyo.
authors.forename: K
authors.initials: K
authors.lastname: Funato
authors.forename: A
authors.initials: A
authors.lastname: Matsuo
authors.forename: H
authors.initials: H
authors.lastname: Yata
authors.forename: H
authors.initials: H
authors.lastname: Akima
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: A
authors.initials: A
authors.lastname: Gunji
authors.forename: T
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D004551:Elbow Joint; D015444:Exercise / Q000502:physiology; D005260:Female; D006621:Hip Joint; D006801:Humans; D007719:Knee Joint; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology* / Q000503:physiopathology; D009133:Muscular Atrophy / Q000209:etiology / Q000503:physiopathology*; D005082:Physical Exertion / Q000502:physiology; D019415:Torque