Comparison of center of pressure trajectory characteristics in table tennis during topspin forehand loop between superior and intermediate players

Introduction and Objectives
Several previous studies have reported that momentum generation depends on foot drive largely in striking motions. Based on this case, the purpose of this study was to investigate the differences in the center of pressure (COP) trajectory under the dominant foot during forehand loop between superior and intermediate players. The whole motion was divided into two key events: backswing and forward swing corresponding to the stage from preparation
to backward-end and the stage from backward-end to forward-end, respectively. Variables as COP anterior-posterior displacement (Dx), medial-lateral displacement (Dy), and velocity ratio between forward swing and backswing (Rf/b) were included.
MethodsThirteen superior (national Division I) and thirteen intermediate (national Division II) male table tennis players volunteered to participate in this study. Novel Pedar insole plantar pressure measurement system (Novel GmbH, Munich, Germany) was used to record COP trajectory. A ball machine projected topspin balls directly to the foreside of the subject's court. All subjects were required to perform single crosscourt forehand loop with maximal power wearing unified
training footwear. At least five successful trials were performed for one subject. Independent samples t-test were taken for each dependent variable. The level of significance was set at p < 0.05.
ResultsDx of superior players at backward-end located more laterally compared with that of intermediate players. No
significant difference was found in Dx at forward-end between two skilled levels. Dy of superior players was obviously smaller at backward-end and forward-end. The data of Rf/b for superior group was significantly higher than the intermediate group. At backward-end, superior players transferred body weight more sufficiently to the racket-side resulting in larger Dx, which may facilitate momentum generation and distal velocity. Dy for the intermediate group located closer to the forefoot region, suggesting that the heel was off the ground, and this may decrease stability of players during this stage. At forward-end, Dx would not be influenced by skilled level. The smaller Dy of superior players contributes to resume to preparation for the next stroke. In addition, for superior players, the slower COP shift velocity during backswing provided a more stable basis for the following stage. While the faster velocity during forward swing related to a forceful lower limb drive which was considered as the "starting point" of kinetic chain.

Conclusion Significant differences between two skilled levels were found in Dx during backswing, Dy during bothbackward and forward swing and Rf/b. The key results indicated that superior players possessed better ability of motion control and technique manipulation. Table tennis coaches and players should pay more attention to stability training and enhancing push-off effect.
References: [1] Elliott, Brit J Sport Med, 40: 392-396, 2006.
[2] Bonnet et al., J Biomech, 47: 1603-1608, 2014.
Disclosure of Interest: None Declared