Energy expenditure during oxygen deficit of submaximal concentric and eccentric exercise.

Aerobic (MR) and anaerobic (Man) energy production was determined in five subjects during the 1st min of concentric and eccentric exercise (steady-state energy expenditure approximately 415 W in both situations). Man was obtained by solving the heat balance equation, MR + Man - S = (R + C + E) +/- parallel to W parallel to, all other variables of which could be measured [S is heat storage; (R + C + E) are the radiative, convective, and evaporative heat losses; and W is work output]. The size of the O2 deficit was similar whatever the type of exercise (99 +/- 19 W concentric and 102 +/- 19 W eccentric). MR + Man was lower than the steady-state MR in both types of exercise (concentric; 364 +/- 19 and 407 +/- 24 W, respectively, and eccentric; 346 +/- 25 and 430 +/- 21 W, respectively). The size of the O2 deficit during the 1st min of muscular exercise is imposed by the steady-state energy requirement whatever the type of exercise. The smaller energy expenditure during this phase is probably due to less energy being released when creatinge phosphate is split without resynthesis (O2 deficit) than during splitting and resynthesis of high-energy phosphate bonds (steady state).