Author(s): WEN-TING, W., YIN-HUA, C., Institution: NATIONAL TAIWAN SPORT UNIVERSITY, Country: TAIWAN, Abstract-ID: 1648

INTRODUCTION:
Previous studies have reported lower anticipation accuracy in predicting the spike direction and movement type for left-handed volleyball players (1). Similar tendency was observed in anticipating the tennis serve direction and depth for left-handed serves even they were mirrored from right-handed ones (2). This phenomenon is attributed to lower perceptual familiarity with left-handed movements. However, whether there are movement coordination differences between left- and right-handed players remains unexamined.
METHODS:
Three left-handed and three right-handed skilled volleyball players were recruited to perform 3 standing overhead float serves. Two high-speed cameras (240 fps) were used to record their serves, and the best trial from each player was selected for analysis. The trajectories of bilateral shoulders, elbows, wrists, hips, knees, and ankles were digitized using Kwon 3D. The resultant 12 joint angle time-series, along with trunk rotation, were input to Principal Component Analysis (PCA) to examine the movement coordination patterns of each serve.
RESULTS:
Compared to right-handed players, left-handed players showed larger dominant ankle angle (130° > 107°) and a smaller non-dominant ankle angle (112° < 128°) at ball contact. The 13 kinematic time-series were effectively represented by 3 components, explaining approximately 80% of the variance. The first component, which included six to nine kinematic time-series, was primarily contributed by bilateral shoulder and knee angles across all serves, highlighting their key role in this type of serve. For two left-handed and one right-handed player, the dominant hip angle, but not the dominant elbow angle, was included in the first component. This suggested that their arm posture remained relatively stable during preparation phase, while changes in the dominant hip angle characterized their movement coordination patterns. Additionally, the trunk rotation was not included in the first component for the two left-handed players. This was due to their shoulder and hip rotating in a similar manner, whereas other players exhibited greater shoulder rotation compared to hip rotation.
CONCLUSION:
The findings of this study suggest that bilateral shoulders and knees movements play an important role in standing overhead float serves. The absence of trunk rotation and dominant elbow angle in the first component for the two left-handed players suggested that their movements provided fewer distinguishable cues compared to right-handed players. This may explain why the movements of left-handed players are more difficult to predict.
REFERENCES:
(1) Hagemann, N. Atten Percept Psychophys. 2009.
(2) Loffing et al., Atten Percept Psychophys, 2012