External mechanical work versus oxidative energy consumption ratio during a basketball field test.

BACKGROUND: A field test consisting of 5 continuous runs at the maximum speed possible, playing the ball, starting from the centre line to the basket with a final shot, was studied in order to obtain an index of mechanical work efficiency in basketball players (micro-index=Jmec/Joxy) and evaluate the correlation between micro-index and velocity, acceleration, mechanical power and lactacid anaerobic capacity, respectively. METHODS: Eight male basketball players were studied; Jmec was the external mechanical work output obtained by means of a video image analysis software which gave the potential and the kinetic translational energies of athletes running and jumping and their velocity, acceleration and mechanical power. By means of a telemetric device (Kosmed K4), for measuring O2 consumption ( VO2), we obtained oxidative work (Joxy). By using this device we also assessed the excess of CO2, which was considered an index of lactacid anaerobic capacity. RESULTS: Non-parametric Spearman statistics revealed a significant correlation between mu index and mean velocity (p<0.01, r=0.90), acceleration (p<0.05, r=0.78), mechanical power (p<0.05 r=0.76) and CO2 excess (p<0.01, r=0.95). Consequently athletes who had the best index of mechanical efficiency also had the best biomechanical quality and the greatest lactacid anaerobic capacity. CONCLUSIONS: This study strongly supports the hypothesis that in basketball anaerobic capacity is important in achieving high values of speed, acceleration, mechanical power and endurance velocity.

Field test for mechanical efficiency evaluation in matching volleyball players.

Field tests were performed in 10 volleyball (VB) players (4 females and 6 males) in order to obtain an index of mechanical work efficiency (mu' = 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 x min(-1), HR = 78 +/- 7b x min(-1), VO2 = 3.71 +/- 1.1 ml x kg(-1) x min(-1), Woxy = 75.1 +/- 22.3 J x kg(-1) x min(-1). During A all variables increased: VE = 49 +/- 6l x min(-1), HR = 149 +/- 15 b x min(-1), VO2 = 23.1 +/- 3.3ml x kg(-1) x min(-1), Woxy = 482.8 +/- 69.0 J x kg(-1) x min(-1), and Wmec 275.5 +/- 57.0 J x kg(-1) x min(-1) with mu'=0.57 +/- 0.09. In D HR (-9%), VE, VO2 and Woxy (-18%) were reduced when compared to A, decreasing mu' to 0.21 +/- 0.05. On the other hand mu' was found higher than 0.25 during A indicating an anaerobic contribution to energy expenditure; in D the mu' lower than 0.25 indicated a restoration of anaerobic energy sources. It might be proposed that a greater difference in mu' values between A and D also means a higher anaerobic energy contribution to the volleyball game.