Professional tennis players' serve: correlation between segmental angular momentums and ball velocity

The purpose of the study was to identify the relationships between segmental angular momentum and ball velocity between the following events: ball toss, maximal elbow flexion (MEF), racket lowest point (RLP), maximal shoulder external rotation (MER), and ball impact (BI). Ten tennis players performed serves recorded with a real-time motion capture. Mean angular momentums of the trunk, upper arm, forearm, and the hand-racket were calculated. The anteroposterior axis angular momentum of the trunk was significantly related with ball velocity during the MEFRLP, RLPMER, and MERBI phases. The strongest relationships between the transverse-axis angular momentums and ball velocity followed a proximal-to-distal timing sequence that allows the transfer of angular momentum from the trunk (MEFRLP and RLPMER phases) to the upper arm (RLPMER phase), forearm (RLPMER and MERBI phases), and the hand-racket (MERBI phase). Since sequence is crucial for ball velocity, players should increase angular momentums of the trunk during MEFMER, upper arm during RLPMER, forearm during RLPBI, and the hand-racket during MERBI.