FACTORS RELATED TO THE DEVELOPMENT OF BALL SPEED AND TO THE INCIDENCE OF ONE-LEGGED LANDINGS IN THE FRONT-ROW VOLLEYBALL ATTACK

A three-dimensional video analysis was used to identify factors related to the development of ball speed and to the incidence of one-legged landings in high-outside, front-row volleyball attacks. At ball contact, hand speed was 11.9±O.9 m·s-1 (mean±SD). Post-impact ball speed was 19.4±2.3 m·s-1. Shoulder and elbow rotations accounted for about 75% of hand speed at the instant of ball contact while the speed of the CM itself accounted for about 16% of hand speed. Trunk rotation and wrist rotation contributed 11 % and 2% to hand speed, respectively. Attackers possessed forward somersaulting, counterclockwise twisting, and counterclockwise "cartwheeling" angular momentum that resulted in faster hand speeds at contact but also a tendency for one-legged landings. Unfortunately. factors contributing to one-legged landings could not be clearly identified

DETERMINISTIC FACTORS OF OVERALL BALL CONTACT HEIGHT DURING HIGH-OUTSIDE FRONT-ROW VOLLEYBALL ATTACKS

The purpose of this study was to quantify the deterministic factors of overall ball contact height among elite level volleyball attackers. Thirty-two trials collected from nine members of the 1999 USA National A2 Team were subjected to 3D analysis. Results demonstrated that takeoff height (CM height at takeoff) and reach height (vertical distance between the hand and CM at contact) accounted for 86.7% of the overall ball contact height. Flight height (in-flight CM elevation) accounted for only 14% of overall height. Reach height was the only meaningful sUb-height that was significantly correlated with overall ball contact height (r=O.70) and appeared to be most sensitive to technique-related differences in performance. Horizontal approach speeds used by the athletes in this study were relatively slow (3.4±O.3 m·s-1) but were positively correlated with flight height (r=O.60)

Addition of an approach to a swimming relay start

Influence sur les vitesses verticale et horizontale du plongeon de départ et sur la performance après 10 mètres de nage, de l'ajout de différents pas d'approche avant le plongeon