title: Knee and ankle joint torque-angle relationships of multi-joint leg extension.
abstract: The force-length-relation (F-l-r) is an important property of skeletal muscle to characterise its function, whereas for in vivo human muscles, torque-angle relationships (T-a-r) represent the maximum muscular capacity as a function of joint angle. However, since in vivo force/torque-length data is only available for rotational single-joint movements the purpose of the present study was to identify torque-angle-relationships for multi-joint leg extension. Therefore, inverse dynamics served for calculation of ankle and knee joint torques of 18 male subjects when performing maximum voluntary isometric contractions in a seated leg press. Measurements in increments of 10° knee angle from 30° to 100° knee flexion resulted in eight discrete angle configurations of hip, knee and ankle joints. For the knee joint we found an ascending-descending T-a-r with a maximum torque of 289.5° ± 43.3 Nm, which closely matches literature data from rotational knee extension. In comparison to literature we observed a shift of optimum knee angle towards knee extension. In contrast, the T-a-r of the ankle joint vastly differed from relationships obtained for isolated plantar flexion. For the ankle T-a-r derived from multi-joint leg extension subjects operated over different sections of the force-length curve, but the ankle T-a-r derived from isolated joint efforts was over the ascending limb for all subjects. Moreover, mean maximum torque of 234.7 ± 56.6 Nm exceeded maximal strength of isolated plantar flexion (185.7 ± 27.8 Nm). From these findings we conclude that muscle function between isolated and more physiological multi-joint tasks differs. This should be considered for ergonomic and sports optimisation as well as for modelling and simulation of human movement.
authors.affiliation: Department of Biomechanics in Sports, Faculty of Sport and Health Science, Technische Universität München, Connollystr. 32, 80809 Munich, Germany. d.hahn@sp.tum.de
authors.forename: Daniel
authors.initials: D
authors.lastname: Hahn
authors.forename: Matthias
authors.initials: M
authors.lastname: Olvermann
authors.forename: Jan
authors.initials: J
authors.lastname: Richtberg
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Seiberl
authors.forename: Ansgar
authors.initials: A
authors.lastname: Schwirtz
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque