Relationship of Maximal Lactate Steady State to Performance at Fixed Blood Lactate Reference Values in Children

This investigation set out to estimate exercise intensity and blood lactate corresponding to the maximal lactate steady state (MLaSS) and also examined the relationship between performance at the MLaSS with performance at fixed blood lactate reference values of 2.5 and 4.0 mmol•1^-1. Cardiopulmonary responses at peak treadmill exercise and blood lactate reference values were measured in 10 boys and 8 girls ages 13-14 years. The 2.5 mmol•1¹ reference value represented 84±7% peak VO₂ in boys and 82±6% peak VO₂ in girls. Corresponding values at the 4.0 mmol•1^-1 level were 93±6% and 90±5% peak VO₂. MLaSS occurred at 77±7% peak VO₂ in boys and 76±7% peak VO₂ in girls. Blood lactate at the MLaSS was 2.1±0.5 mmol•l^-1 in boys and 2.3±0.6 mmol•l^-1 in girls. Cardiopulmonary and heart rate responses at the MLaSS were not significantly different from corresponding responses at the 2.5 mmol•l^-1 reference value. In contrast, cardiopulmonary responses at the 4.0 mmol•l^-1 reference level were significantly higher than those at the MLaSS. These data indicate that a 2.5 mmol•l^-1 criterion for assessing aerobic performance in children may be the most appropriate.