Muscle synergy of the periarticularis shoulder muscles during a wheelchair propulsion motion for wheelchair basketball

We aimed to investigate the muscle synergy of the periarticularis shoulder muscles during wheelchair propulsion motion for wheelchair basketball in healthy participants to obtain fundamental data, as a first attempt.

Twelve healthy adult males with no previous wheelchair driving experience were included in this study. The task was a wheelchair propulsion motion of 20 m with the maximum effort of the participants. Surface electromyography data of 10 muscles (Anterior deltoid; AD, Middle deltoid; MD, Posterior deltoid; PD, Biceps brachii; BB, Triceps brachii; TB, Pectoralis major; PM, Serratus anterior; SA, Infraspinatus; IS, Upper trapezius; UT, Latissimus dorsi; LD) involved in shoulder joint movements were measured during the task using a digital-signal processing (DSP) wireless dry-type myoelectric sensor (SS-EMGD-HMAG; Sports Sensing Corporation, Japan). Muscle synergies were extracted using non-negative matrix factorization analysis of the electromyography data. All data analyses were performed using the MATLAB numerical analysis software (MATLAB R2023a; MathWorks, Inc., USA).

Four muscle synergies were identified during wheelchair propulsion. In the push phase, muscle synergies consisting of AD, BB, PM, and SA and those consisting of AD, TB, PM, and SA were extracted, indicating that the push movement was performed by two muscle synergies centered on the shoulder flexor muscles. In the recovery phase, synergies consisting of the shoulder extensors (PD, TB) and muscles that contributed to shoulder girdle stabilization (MD, PD, IS, UT, LD) were extracted, respectively.

We found that healthy individuals underwent wheelchair propulsion using the four muscle synergies. Generally, the push phase is the period during which tires are pushed forward, and the recovery phase is the period for preparing for the next push motion. The two synergies in the push phase may have contributed to the acquisition of forward propulsion, whereas those in the recovery phase may have acted to the backward movement of the upper limbs and stabilize the shoulder girdle at that time. Since differences in muscle synergy are associated with injury occurrence, we will investigate muscle synergy in wheelchair basketball players based on these data to elucidate the mechanism of shoulder pain occurrence as a next attempt.

This study results on healthy participants provide basic muscle synergy data for wheelchair propulsion motion without the influence of disability or pain. In the future, comparison with data from wheelchair basketball players may offer insights into injury prevention and performance improvement.