# The Hidden Link in the Kinematic Chain: The Influence of the Tossing arm on Head and Serve Kinematics in Tennis

## TL;DR

This study shows how changing the timing of a tennis player's tossing arm affects the ball's trajectory and overall serve mechanics.

## Contribution

The study reveals new insights into how the tossing arm's motion influences serve kinematics and performance.

## Key findings

- Early tossing arm adduction leads to a steeper downward ball trajectory.
- Late tossing arm adduction results in a flatter ball trajectory, reducing accuracy.
- Altered tossing arm timing increases ball toss height and forward position without affecting head kinematics.

## Abstract

The control and placement of the ball toss are critical features of the tennis serve. Whereas much attention has been given to the ball's trajectory, the motion of the tossing arm has been overlooked. This study aimed to describe the kinematics of the tossing arm and its impact on full‐body kinematics and serve performance. Ten high‐performance male tennis players were studied using a 10‐camera, 250 Hz VICON T‐series motion analysis system capturing full‐body, racquet, and ball kinematics. Each participant executed ten maximum effort first serves with instructions to (i) serve normally, (ii) adduct the tossing arm early and (iii) adduct the tossing arm late. While head kinematics remained unaffected by the serve condition, the ball toss was higher and further forward in both altered conditions, increasing serve duration (p < 0.001). Players compensated by extending the preparation phase's proportion of the serve by 4.3% in both conditions. Serve trajectory was ∼3° steeper downwards (p < 0.001) in the early condition and ∼1° flatter (p = 0.020) in the late condition than participants' normal serve. In summary, alterations to the tossing arm elicited the expected changes in the serve's post‐impact ball trajectory, but coaches must monitor several unintended consequences.

Compared to the player's normal serves, adducting the tossing arm earlier resulted in a steeper downward ball trajectory, whereas adducting the tossing arm later resulted in a flatter ball trajectory, hindering its accuracy.In both tossing arm conditions, the ball toss was higher and further forward; however, it had no significant impact on the position of the head.Altering the timing of tossing arm adduction impacted the serve's temporality, where players would extend the preparation phase in proportion to the entire service motion

Compared to the player's normal serves, adducting the tossing arm earlier resulted in a steeper downward ball trajectory, whereas adducting the tossing arm later resulted in a flatter ball trajectory, hindering its accuracy.

In both tossing arm conditions, the ball toss was higher and further forward; however, it had no significant impact on the position of the head.

Altering the timing of tossing arm adduction impacted the serve's temporality, where players would extend the preparation phase in proportion to the entire service motion