Whether age-related differences in blood lactate concentrations (BLC) reflect specific BLC kinetics was analyzed in 15 prepubescent boys (age 12.0 ± 0.6 yr, height 1.54 ± 0.06 m, body mass 40.0 ± 5.2 kg), 12 adolescents (16.3 ± 0.7 yr, 1.83 ± 0.07 m, 68.2 ± 7.5 kg), and 12 adults (27.2 ± 4.5 yr, 1.83 ± 0.06 m, 81.6 ± 6.9 kg) by use of a biexponential four-parameter kinetics model under Wingate Anaerobic Test conditions. The model predicts the lactate generated in the extravasal compartment (A), invasion ( k1), and evasion ( k2) of lactate into and out of the blood compartment, the BLC maximum (BLCmax), and corresponding time (TBLCmax). BLCmax and TBLCmax were lower ( P < 0.05) in boys (BLCmax 10.2 ± 1.3 mmol/l, TBLCmax 4.1 ± 0.4 min) than in adolescents (12.7 ± 1.0 mmol/l, 5.5 ± 0.7 min) and adults (13.7 ± 1.4 mmol/l, 5.7 ± 1.1 min). No differences were found in A related to the muscle mass (AMM) and k1 between boys (AMM: 22.8 ± 2.7 mmol/l, k1: 0.865 ± 0.115 min−1), adolescents (22.7 ± 1.3 mmol/l, 0.692 ± 0.221 min−1), and adults (24.7 ± 2.8 mmol/l, 0.687 ± 0.287 min−1). The k2 was higher ( P < 0.01) in boys (2.87 10−2 ± 0.75 10−2 min−1) than in adolescents (2.03 × 10−2 ± 0.89 × 10−2 min−1) and adults (1.99 × 10−2 ± 0.93 × 10−2 min−1). Age-related differences in the BLC kinetics are unlikely to reflect differences in muscular lactate or lactate invasion but partly faster elimination out of the blood compartment.
How adolescents and adults translate motivational value to action: Age-related shifts in strategic physical effort exertion for monetary rewards.
