Short-term effects of light and heavy load interventions on service velocity and precision in elite young tennis players.

OBJECTIVE This study was conducted to investigate the acute effects of a complex throwing intervention set-up, with light or heavy loads, on the service velocity of elite junior tennis players. METHODS On 3 separate test days, 13 elite juniors (mean (SD) 12.3 (0.8) years, 149 (9) cm, 37.5 (5.5) kg) performed four sets of six serves with different between-set conditions. In a cross-over design, the players performed respectively 6, 4 and 2 maximum effort throws with a 200 g ball (LI, light intervention), 6, 4 and 2 maximum effort throws with a 600 g ball (HI, heavy intervention) and no throws (NI, no intervention) during the 2 min in between-set period. Participants were instructed to serve, with maximum speed, to a target near the midline of the deuce court service box. A two-factor analysis of variance was used to determine the effects of intervention type and set number on "service velocity", "service precision" (eg, percentage of serves in) and "service touch" (11 point rating scale). RESULTS Mean (SD) service velocity decreased significantly in HI (124.3 (7.8) km/h) as compared to NI (126.6 (9.3) km/h, p<0.05, effect size d = 0.26), yet no such differences were found between LI (125.2 (7.9) km/h) and NI. Service velocity also remained constant between sets (p = 0.406). Service precision and service touch were unaffected by the interventions. CONCLUSIONS Under the conditions of our study, a heavy throwing intervention during service training has no beneficial effect on service velocity in young elite tennis players (under 14).