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 (μ' = W_mec/W_oxy) while athletes played a game. W_mec 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. W_oxy was the oxidative energy consumption obtained from O₂ consumption (VO₂) by a telemetry device (Cosmed K2) that also gave values of pulmonary ventilation (V_E) 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: V_E = 11 ± 1 l·min^-1, HR = 78 ± 7b· min^-1, VO₂ = 3.71 ± 1.1 ml · kg^-1 · min^-1, W_oxy = 75.1 ± 22.3 J · kg^-1 · min^-1. During A all variables increased: V_E = 49 ± 61 · min^-1, HR = 149 ± 15 b · min^-1, VO₂ = 23.1 ± 3.3 ml · kg^-1 · min^-1, W_oxy = 482.8 ± 69.0 J · kg^-1 min^-1, and W_mec 275.5 ± 57.0 J · kg^-1 · min^-1 with μ' = 0.57 ± 0.09. In D HR (- 9 %), V_E, VO₂ and W_oxy (-18 %) were reduced when compared to A, decreasing μ' to 0.21 ± 0.05. On the other hand m' was found higher than 0.25 during A indicating an anaerobic contribution to energy expenditure; in D the μ' lower than 0.25 indicated a restoration of anaerobic energy sources. It might be proposed that a greater difference in μ' values between A and D also means a higher anaerobic energy contribution to the volleyball game.

Key words

Video-mage analysis - telemetry transmission - volleyball - mechanical efficiency - field tests - oxygen consumption