Author(s): HUNG, Y., WANG, C.K., LIAO, C.J., HE, C.S., Institution: NATIONAL CHUNG CHENG UNIVERSITY, Country: TAIWAN, Abstract-ID: 1567

INTRODUCTION:
Volleyball is an overhead sport where the shoulder joint endures high-frequency arm-swinging and ball-hitting loads during competition and training. Consequently, shoulder strength and stability are often regarded as critical factors influencing athletic performance and shoulder injury risk (1). In practical training, both machine-based and free-weight exercises can enhance shoulder joint strength. The former reduces movement variability and enhances training safety by fixing the exercise trajectory, while the latter emphasizes multi-joint coordination and core stability engagement (2). However, direct comparative studies on shoulder joint training interventions for female volleyball players remain relatively scarce. This study aims to investigate the effects of machine training versus free weight training on shoulder joint strength, stability, and athletic performance in female volleyball athletes.
METHODS:
This study recruited 33 healthy female volleyball athletes (aged 18–25 years) with regular training experience. Participants were randomly assigned to either a mechanical resistance training intervention or a free weight resistance training intervention for the shoulder joint strength. The training intervention lasted four weeks, with three sessions per week. shoulder joint strength, spike velocity, and stability were measured both before and after the intervention. Shoulder joint isokinetic strength was assessed at 60°/s and 180°/s. Spiking velocity was measured using a radar gun. Stability was evaluated using the closed kinetic chain upper limb stability test. Statistical analysis employed a two-factor mixed design repeated measures ANOVA with a significance level set at α = 0.05.
RESULTS:
The results indicate that the group × time interaction effects for all variables were not significant. Mean power during isokinetic strength testing at 60°/s and 180°/s shoulder internal rotation exhibited a main effect of time (η_p^2 = 0.300 and 0.183, respectively; p < 0.001, p = 0.013), with post-test values significantly higher than pre-test values. Both spike velocity (η_p^2 = 0.271; p = .002) and stability (η_p^2 = 0.685; p < .001) exhibited main effects of time, with post-test values significantly higher than pre-test values.
CONCLUSION:
This study demonstrates that a four-week shoulder joint resistance training program enhances female volleyball players' average power during shoulder internal rotation, shoulder joint stability, and spike velocity. However, no significant differences were observed between machine-based training and free weight training after the four-week intervention, indicating comparable training efficacy for both methods. Therefore, coaches and athletes may flexibly incorporate either machine-based or free-weight training into routine programs based on equipment accessibility, safety considerations, and individual athlete needs. The choice of training modality will not diminish the effectiveness of performance enhancement.