Effect of previous supramaximal work on lacticaemia during supra-anaerobic threshold exercise

Summary

Twelve male and female subjects (eight trained, four untrained) exercised for 30 min on a treadmill at an intensity of maximal O₂ consumption (% $\dot V$O_2max) 90.0%, SD 4.7 greater than the anaerobic threshold of 4 mmol ·1⁻¹ (Th_an =83.6% $\dot V$O_2max, SD 8.9). Time-dependent changes in blood lactate concentration ([la_b]) during exercise occurred in two phases: the oxygen uptake ($\dot V$O₂) transient phase (from 0 to 4 min) and the $\dot V$O₂ steady-state phase (4–30 min). During the transient phase, [la_b] increased markedly (l.30 mmol · l ⁻¹ · min ⁻¹, SD 0.13). During the steady-state phase, [la_b] increased slightly (0.02 mmol · 1⁻¹ · min⁻¹, SD 0.06) and when individual values were considered, it was seen that there were no time-dependent increases in [la_b] in half of the subjects. Following hyperlacticaemia (8.8 mmol -l⁻¹, SD 2.0) induced by a previous 2 min of supramaximal exercise (120% $\dot V$O_2max), [la_b] decreased during the $\dot V$O₂ transient (−0.118 mmol · 1⁻¹ · min⁻¹, SD 0.209) and steady-state (−0.088 mmol · 1⁻¹ · min ⁻¹, SD 0.103) phases of 30 min exercise (91.4% $\dot V$O_2max, SD 4.8). In conclusion, it was not possible from the Th_an to determine the maximal [la_b] steady state for each subject. In addition, lactate accumulated during previous supramaximal exercise was eliminated during the $\dot V$O₂ transient phase of exercise performed at an intensity above the Th_an. This effect is probably largely explained by the reduction in oxygen deficit during the transient phase. Under these conditions, the time-course of changes in [la_b] during the $\dot V$O₂ steady state was also affected.