Plasma lactate and plasma volume recovery in adults and children following high-intensity exercises

Aim: To compare plasma lactate concentration recovery kinetics when measured and corrected for variations in plasma volume between children and adults. Methods: Nine boys (11.3 +/- 1.1 y) and 8 men (21.9 +/- 1.9 y) performed a maximal and a supramaximal exercise until exhaustion. Plasma lactate concentrations, haemoglobin and haernatocrit were measured at rest, immediately on completion of exercise and after the 2nd, 5th, 12th and 30th minute of recovery. The plasma lactate concentrations and the rate of recovery were corrected for variations in plasma volume. Results: The maximal decreases in plasma volume were significantly higher in adults than in children for maximal exercise (-18.7 +/- 2.6% vs -14.5 +/- 3.2%; p < 0.05), but similar for the supramaximal exercise (-16.9 +/- 3.4% vs -15.2 +/- 3.4%). During recovery, measured and corrected plasma lactate concentrations were significantly higher in adults. The rate of plasma lactate recovery was higher in adults for maximal exercise only. The same results were obtained when the rates of plasma lactate decrease were calculated from corrected plasma lactate concentrations. Conclusion: The correction of the plasma lactate concentrations for variations in plasma volume did not influence the comparison of the concentrations obtained in adults and children, or their rate of recovery.