Title: BALL AND RACQUET KINEMATICS OF THE FIRST AND SECOND SERVES PERFORMED BY ELITE TENNIS PLAYERS
Abstract: 867 The purpose of this study was to quantify the pre- and post-impact 3-D kinematics of the ball and racquet during the first and second serves performed by elite tennis players. Five male and four female right-handed professional players (world singles rankings ranged from 3 to 137) served as the subjects. Data were collected during the tennis competition of the 1996 Atlanta Olympic Games using two high-speed cameras (200 Hz). For each subject, one first serve and one second serve that landed at the same location were analyzed. A two-way ANOVA (sex x serve type) with repeated measures (p ≤ .05) was performed for each parameter. The results indicate that, regardless of the sex and serve type, the ball traveled forward and to the left during the flight phase before impact. However, the pre-impact ball forward location of the first serve was significantly more in front and had a higher forward velocity than the corresponding values found for the second serve. Significant main effects were found for post-impact ball velocity with first serves and males having higher ball velocities. On average, the decreases in post-impact ball velocity from the first to second serve were 17.6% and 30.5% for the males and females, respectively. Although not statistically significant, a decrease in forward velocity (p = .065) and an increase in vertical velocity (p = .082) were found in the pre-impact racquet velocity when the serve type changed from first to second. Because the pre-impact racquet speed and orientation for the two serve types did not differ significantly, it seems that the major adjustments made by the players when going from the first to second serve were in the changes in pre-impact ball location and the direction of the pre-impact racquet velocity. Supported in part by the IOC, ACOG, and UIUC Research Board.