Reaction Times in Volleyball Block: A Biomechanical Analysis.

INTRODUCTION – AIM OF THE STUDY: Blocking is an indispensable feature of winning volleyball teams. Among the fundamental components of efficient block execution the reaction time is especially important (Vint1). There is a large body of research in the sphere of experimental psychology (Pesce Anzeneder e.g2), but less in applied situation (Dorfhman3, Westphal4). Biomechanical analysis of the block in volleyball was not presented data relative to this important aspect (Quade5 and Lobietti6 e.g). The aim of this study was to collect data on block reaction time by means of stereo-photogrammetry and to compare tendencies from the different type of block. METHODS: This study analysed block techniques used by 10 male volleyball players (age 26.7, height 192.4 m, weight 86.7 kg) of B1 Italian League. 3D kinematics were estimated by means of stereo-photogrammetry (Vicon Motion Systems, Oxford, UK). Six infrared cameras (max resolution 300.000 pixel, frequency 100 Hertz) filmed markers (diameter 14 mm) attached to the body (45), the net (4) and the stick (2). Players had to carry out block exercises as answer to a stimulus: an operator on the other side of the net moved the stick up, right or left in order to simulate the possible sets in zone 2, 3 or 4. Players had to jump vertically or after a lateral move (slide or cross step). The reaction time was calculated as the difference between the frame of the first movement of the COMr (Centre of mass of trunk and lower body) and the frame of the first movement of the stick. Obtained results were further analysed to allow the comparison depending on the block technique used. Statistical Analysis: The T-Test (α=0.05) was performed to analyse differences between the vertical jump and block with lateral move. RESULTS: The subjects were fastest to react when they executed the slide towards right (254±27 msec), while they were slowest when they had to execute a vertical Jump (343±54 msec). T-tests showed significant differences between vertical jump and the jump with right movement using both techniques: slide (t=0.0009) and cross (t=0.007). To the left significant differences were not found (t=0.15 comparing with the slide and t=0.14 with the cross). The reaction time was faster moving to the right (t=0.006) than the left. CONCLUSIONS: Examined players were faster to react in lateral moves than in vertical jumps. We can suppose that the reason for this is that in the real game ouside blockers are ready to move laterally instead of jumping vertically. REFERENCES: 1. VINT, P., (1997). “Qualitative Analysis of a volleyball Blocking Performance”. University of North Carolina at Greensboro. 2. PESCE ANZENEDER, C. et al. (1997). “Attività cerebrale e prestazione attentiva nel pallavolista”, Sds/Rivista di cultura sportiva, Anno XVI, n. 39, 53-62 3. DORFMAN, P. W., (1977). “Timing and anticipation: a developmental perspective”, Journal of Motor Behaviour, Vol. 9 No. 1, 67-79 4. WESTPHAL, G. et al. (1985). “ Zur Antizipationsfähigkeit des Blockspielers im Volleyball“, Leistungssport 6/85 5. QUADE, K. (1993) “Zur Funktion und Belastung der unteren Extremitäten bei volleyballspezifischen Sprüngen”, SFT-Verlag Erlensee. 6. LOBIETTI, R. et al. (2006). “Blocking the quick attack in volleyball: a 3D kinematical analysis”, Department of Sport Science and Kinesiology University of Salzburg 14-18 July 2006 (eds.), Salzburg