Abstract
This study investigated muscle synergy during smash shot in badminton and compared synergies of advanced players (more than 7 years experience) and beginner players (less than 3 years experience). The dominant hand of all players was the right side. Muscle activities were recorded on both sides of the rectus abdominis, external oblique (EO), internal oblique/transversus abdominis (IO/TrA), and erector spinae. Additionally, the right side of the biceps brachii, triceps brachii, flexor carpi radialis, flexor carpi ulnaris, and flexor digitorum profundus muscle activities were recorded. All data was obtained using surface electromyography. Synergy was extracted from electromyography signals using nonnegative matrix factorization. Extracted synergies in each group were compared using scalar product (SP) which is the similarity index. As a result, two synergies were extracted in the beginner players and three synergies were extracted in advanced players. Beginner and advanced players had one synergy in common (SP = 0.86) that was mainly on the left side of the EO. It activated in the early stroke and had a role of side bending from the left to hit the shuttlecock at a higher point. Another synergy that had coactivation of the IO/TrA and forearm muscles at impact was extracted only for advanced players and it may enhance the smash shot performance in badminton.
Highlights
Bernstein proposed the “module hypothesis,” and recently, based on this concept, a neural control mechanism during locomotion was investigated through electromyography (EMG) using nonnegative matrix factorization (NMF) [1]
Two synergies were extracted from the novice players (VAF: 0.92 ± 0.01) and three synergies were extracted from the advanced players (VAF: .93 ± 0.03)
This result indicated that there was no problem for intrareliability in this study
Summary
Bernstein proposed the “module hypothesis,” and recently, based on this concept, a neural control mechanism during locomotion was investigated through electromyography (EMG) using nonnegative matrix factorization (NMF) [1]. From NMF, EMG is divided into muscle synergy and an activation coefficient. Muscle synergy indicates the muscle combination to be mobilized and activation coefficient indicates the activation timing of muscle synergy. The modules include these factors and human movements are performed by the combination of several modules. Sawers et al reported that the number of synergies of elite dancers during walking was lots than that of beginners [7]. From these reports, synergy is different due to competitive level and beginners may improve if they get the synergy as elite athletes. It is considered that to clarify the difference of synergy due to competitive level is important information for athletes and coaches
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