Effect of series elasticity on isokinetic torque-angle relationship in humans.
The influence of muscle series elasticity on the relationship between torque and joint angle during dynamic contractions was studied. The torque-angle relationship during the maximal isokinetic knee extension was determined for six male subjects (25-45 years) at 0.52, 1.05, 1.57, 2.09, 2.62, 3.49 rad/s. The knee joint angle at which peak torque was observed showed a systematic shift to more extended positions, i.e., the quadriceps muscle-tendon unit length became shorter as the velocity increased [from 1.01 (0.12) rad (0.52 rad/s) to 0.75 (0.14) rad (3.49 rad/s), mean (SD)]. The corresponding difference in muscle-tendon unit length between 0.52 and 3.49 rad/s, estimated from the angle shift at peak torque and the moment arm length change of the quadriceps muscles, was 9 (4) mm. The relationship between estimated changes in muscle-tendon unit length and muscle force of the vastus lateralis and intermedius (VLI) over the seven velocities (including isometric contraction, 0 rad/s) coincided with the load-elongation properties of the series elastic component of VLI, determined separately in vivo by ultrasonography when the same subjects performed a ramp isometric knee extension. The results suggest that the torque-angle relationship is affected by the interaction between contractile and elastic components, and that peak torque angle shift is attributable to the elongation of tendinous tissues as a function of force applied to them.
Kawakami
Y
Y
Department of Life Sciences (Sports Sciences), Graduate School of Arts and Sciences, University of Tokyo, Komaba, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan. kawakami@idaten.c.u-tokyo.ac.jp
Kubo
K
K
Kanehisa
H
H
Fukunaga
T
T
D000328:Adult; D004548:Elasticity; D004576:Electromyography; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D019415:Torque