Annual ECSS-Congress, Bruges 2012
||[MO-PM37] Training and Testing: Fatique and neuromuscular physiology
||High Live 1
Date & time:
||26.06.2015 / -
|Title of the paper:
Muscle synergies of lower limbs during vertical jump
||Takagi, H.1, Hagio, S.1, Kouzaki, M.1
||1: Kyoto University
||Graduate School of Human and Environmental Studies
In human vertical jump, multiple muscles are activated in a timely way and in a moment, in order to generate hip joint torque and knee joint torque ankle joint torque. Hence, very complicated and precise control is required in human vertical jump. In the study of motor control, muscle synergy, neural control mechanism activating multiple muscles coordinately was suggested (Tresch et al., 1999; Ting and Macpherson, 2005; d’Avella et al., 2003). Human vertical jump may be low-dimensionally achieved by muscle synergies. Therefore, the purpose of this study is to clarify how the CNS control human vertical jump based on muscle synergy.
Subjects performed different types of maximum jump, i.e., squat and countermovement jumps with and without arms swing. There were 5 trials with a sufficient rest for removing fatigue between each type of jump. During tasks, the vertical and horizontal ground reaction forces, the three-dimensional position coordinate of locations of the 29 anatomical landmarks and electromyogram (EMGs) of 24 muscles in right side were measured. The EMGs were divided by standard deviation of each muscle and were combined into matrix. The nonnegative matrix factorization was applied to extract individual muscle synergies and their activation coefficients of muscle synergies (Lee and Seung, 1999; Tresch et al., 1999).
Muscle synergies and their activation coefficients were extracted from all subjects for each task. In countermovement jump, the peaks of activation coefficients come at the similar timing and rhythm for all subjects. Muscle weighting of synergies activated in the second phase from the last were similar for all subjects (r = 0.42 - 0.74). Muscle synergies in other phases were differ among subjects, but there are similar synergies activated in different timing.
The significance finding was that 4 or 5 muscle synergies were extracted from EMGs of 24 muscles in countermovement jump to sufficiently reconstruct the original EMG. That suggests that human vertical jump is low-dimensionally achieved by muscle synergies. The peaks of activation coefficients occur at the similar timing and rhythm for all subjects, while muscle synergies activated in the same timing were differ among subjects. In human jump, the CNS inherently utilizes similar muscle synergies and timing of activation of muscle synergies has similarity, but how order the CNS activates the muscle synergies are different among individuals.
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