Biomechanical comparison of the role of bi-articular rectus femoris in standing broad jump and vertical jump

抄録

The role of bi-articular rectus femoris (RF) in motion control and energy transportation was investigated in jumping motions. Standing broad jumps (BJ) and vertical jumps (VJ) of six male subjects (mean body height 1.71 m, mean body mass 62.8 kg) were analyzed by inverse dynamics. Length of muscle tendon complex (MTC) was estimated for RF and mono-articular vastus medialis (VM), from joint angles. Surface EMG signals were recorded from RF and VM. These values were compared between BJ and VJ. Mechanical energy (sum of potential and translational kinetic energy) that provided to the mass center of body (MCB), by the instant of take off was not significantly different between BJ (301 J) and VJ (308 J). Angular velocity of head, arms and trunk segment was larger in BJ (4.06 rads^-1) than in VJ (1.86 rads^-1) , at the instant of take off. Hip extension was more freely executed in BJ than in VJ. Longer eccentric phase of RF MTC was observed in BJ than in VJ, which suggested that muscle force of RF was lower in BJ. Larger EMG activity was observed for RF in VJ than in BJ (ratio of peak value of low pass filtered signal, VJ/BJ=1.50). This difference could not be observed for VM. Contribution of hip joint in total positive work was larger in BJ (55%) than in VJ (44%), whereas contribution of ankle joint was larger in VJ (33%) than in BJ (24%). These data supported the hypothesis that the action of RF controlled the rotational motion of HAT segment, at the same time transferring the mechanical energy from hip to knee joint.