An EMG study of balance control after unexpected external perturbations in handstand: A preliminary study

Abstract

The purpose of this study was to examine the muscle synergy during handstand perturbed by external disturbances. Five members of a male university gymnastics club were asked to handstand on a landing mat. A series of disturbances were applied to each subject by colliding a 1.0 kg object suspended from a 2.8 m high horizontal bar like a pendulum with the lower legs of the subject. The electromyographic (EMG) signals were measured from 8 muscles during the trial and muscle synergy was extracted using non-negative matrix factorization (NMF). Two patterns of synergy were extracted: One showed the synchronized activations of the wrist flexors, posterior deltoid, and rectus abdominis, which prevented the gymnast from bending toward dorsal direction at wrist and intervertebral joints during a handstand. The other showed the synchronized activations of the anterior deltoid, posterior deltoid, wrist extensors, and multifidus, which prevented the gymnast from bending toward the ventral direction at shoulder, wrist, and intervertebral joints during a handstand. The results suggest that two antagonistic patterns of muscle synergy control the balance and posture of handstand when perturbed in the ventral-dorsal directions. Further studies are indicated to confirm these findings.