This study explored the performance of the Sitting Volleyball serve by investigating the causal factors associated with ball velocity. Thirty-seven athletes underwent anthropometry and strength assessment and performed ten successful maximal effort serves. Ball velocity was measured using a sports radar gun. The hip, shoulder, elbow and wrist angles at the instant of ball impact as well as the height of ball impact were estimated through two-dimensional motion analysis. The causal relationships between variables were described through a linear Structural Equation Model and a Directed Acyclic Graph. Results showed that a smaller hip angle determines a greater shoulder angle, which in turn causes a greater elbow angle. A more open elbow angle together with a greater vertical reach allowed for a greater height of ball impact. Finally, increased height of ball impact along with greater abdominal strength are beneficial for higher ball velocity. These results underlined that the Sitting Volleyball serve is a multifactorial stroke involving anthropometric, technical and strength factors and suggest that athletes should improve their abdominal strength and master the technique necessary to perform the serve with the shoulder and the elbow joints fully extended in order to produce the greatest possible impact on the ball.

本研究通过调查与球速度相关的因果因素来探讨坐式排球发球的性能。三十七名运动员接受了人体测量和力量评估，并成功完成了十次最大努力发球。使用运动雷达枪测量球速度。通过二维运动分析估计球撞击瞬间的髋、肩、肘、腕角度以及球撞击的高度。通过线性结构方程模型和有向无环图描述变量之间的因果关系。结果表明，较小的髋部角度决定了较大的肩部角度，进而导致更大的肘部角度。更开放的肘​​部角度和更大的垂直范围可以实现更高的击球高度。最后，增加球冲击高度以及增强腹部力量有利于提高球速。这些结果强调了坐式排球发球是一种涉及人体测量、技术和力量因素的多因素击球，并建议运动员应提高腹部力量并掌握在肩关节和肘关节完全伸展的情况下进行发球所需的技术，以便产生对球的最大可能的影响。