Kinematic differences in the in-match serve between top-ranked and lower-ranked Women's Tennis Association players

Although high serve velocity is recognized as a decisive factor in women's tennis, the specific in-match kinematic variations that distinguish top-ranked players from lower-ranked competitors remain under-investigated.

The videos of the first serve were collected at competition venues from seven top-ranked players (ranked within the top 40 as of September 2019) and ten lower-ranked players (ranked outside the top 100). Joint angles were calculated using three-dimensional projection angle method based on the kinematic data obtained from FM3DMotion software. Independent-samples t-test and Mann-Whitney U test were employed to compare the kinematic differences between the two groups.

Ball velocity, elbow angle at maximum knee flexion, elbow angle at the racket's lowest position, and peak elbow angular velocity during the cocking phase were greater in top-ranked players (p < 0.05). The center of mass to racket side foot distance, shoulder external rotation angle at maximum knee flexion, occurrence time of hip peak linear velocity, and ranges of trunk flexion/extension and lateral flexion during the acceleration phase were greater in lower-ranked players (p < 0.05).

Kinematics such as an elevated upper arm and open elbow at MKF, a rapid elbow flexion during cocking phase, and dominant trunk rotation are characteristic of elite players. These patterns may serve as potential technical targets for developing players aiming to optimize serve velocity.