Graduate School of Sport Sciences, Waseda University, Tokorozawa, Saitama, Japan.
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan.
PLoS One. 2021 Sep 14;16(9):e0257295. doi: 10.1371/journal.pone.0257295. eCollection 2021.
Among tennis coaches and players, the standard volley and drop volley are considered basically similar, but muscles need to be relaxed (deactivation) just at the moment of impact when hitting the drop volley. However, this is not evidence-based. The aim of this study was to clarify racket head trajectory and muscle activity during the drop volley and to compare them with those of the standard volley. We hypothesized that 1) the racket head would move less forward for the drop volley than for the standard volley and 2) the wrist and elbow muscles be relaxed for the drop volley at the time of ball impact. Eleven male college students with sufficient tennis experience volunteered to participate in this study. Wireless EMG sensors recorded activation of the four arm muscles. Each subject performed the standard volley or the drop volley with both a forehand and a backhand from a position near the net. Four high speed video cameras (300 Hz) were set up on the court to measure ball speed and racket head trajectory. Returned ball speed of the drop volley was significantly lower than that of the standard volley (p < 0.05). The racket head moved less forward than in the standard volley, supporting the first hypothesis. Muscle activity of the drop volley, just before and after ball impact for both the forehand and backhand, was lower than that of the standard volley. However, the activity was in the form of a gradual increase as impact time approached, rather than a sudden deactivation (relaxation), which did not support the second hypothesis. For the drop volley, lower muscle activity in the forearm enabled a softer grip and thus allowed a "flip" movement of the racket to diminish the speed of the returned ball.
在网球教练和运动员中，标准截击和低截击被认为基本相似，但在击打低截击时，肌肉需要在击球瞬间放松（失活）。然而，这并没有得到证据的支持。本研究旨在阐明低截击时的球拍头轨迹和肌肉活动，并将其与标准截击进行比较。我们假设 1）低截击时球拍头向前移动的距离比标准截击时小，2）在球撞击时，手腕和肘部肌肉在低截击时放松。11 名有足够网球经验的男性大学生自愿参加了这项研究。无线肌电图传感器记录了 4 个手臂肌肉的激活情况。每个受试者在靠近球网的位置用正手和反手进行标准截击或低截击。在球场上设置了四个高速摄像机（300Hz）来测量球速和球拍头轨迹。低截击的回球速度明显低于标准截击（p<0.05）。球拍头向前移动的距离比标准截击小，这支持了第一个假设。与标准截击相比，无论是正手还是反手，低截击的球前和球后肌肉活动都较低。然而，活动形式是逐渐增加，而不是突然失活（放松），这并不支持第二个假设。对于低截击，前臂的肌肉活动较低，使握拍更软，从而允许球拍“翻转”运动，降低回球速度。
