Abstract des Autors

Field tests were performed in 10 volleyball (VB) players (4 females and 6 males) in order to obtain an index of mechanical work efficiency (my' = Wmec/Woxy) while athletes played a game. Wmec was the mechanical work output, obtained by means of home made video image analysis software, by summing potential, kinetic translational and kinetic rotational energies of running and jumping athletes. Woxy was the oxidative energy consumption obtained from O2 consumption (VO2) by a telemetry device (Cosmed K2) that also gave values of pulmonary ventilation (VE) and heart rate (HR). VB were studied at rest before a game (R), during attacking phases (A) and during defensive phases (D). At R were found: VE = 11+/-1 l/min, HR = 78+/-7 b/ min, VO2 = 3.71+/-1.1 ml/kg/min, Woxy = 75.1+/-22.3 J/kg/min. During A all variables increased: VE = 49+/-6 l/min, HR=149+/-15 b/min, VO2 = 23.1+/-3.3 ml/kg/min, Woxy=482.8+/-69.0 J/kg/min, and Wmec 275.5+/-57.0 J/kg/min with my' = 0.57+/-0.09. In D HR (-9%), VE, VO2 and Woxy (-18%) wre reduced when compared to A, decreasing my' to 0.21+/-0.05. On the other hand my' was found higher than 0.25 during A indicating an anaerobic contribution to energy expenditure; in D the my' lower than 0.25 indicated a restoration of anaerobic energy sources. It might be proposed that a greater difference in my' values between A and D also means a higher anaerobic energy contribution to the volleyball game. Verf.-Referat