BLOOD LACTATE AND PYRUVATE CONCENTRATIONS, AND THEIR RATIO DURING EXERCISE IN HEALTHY-CHILDREN - DEVELOPMENTAL PERSPECTIVE

Blood concentrations of lactate normally increase during and after int ense exercise as does the ratio of concentrations of lactate to pyruva te (L:P). Since there appear to be differences in blood lactate concen trations on exercise, in muscle metabolic enzyme activities, and in an aerobic capacity between children and adults, we speculated that there would be age related differences in lactate and pyruvate concentratio ns, and their ratio among children. Whole blood concentrations of lact ate and pyruvate were measured in 28 healthy children aged 7-17 years, split into three age groups: less than 11, 11-14, and 15-17 years. Bl ood was drawn at rest, immediately after 6 min of exercise at one-thir d and two-thirds of maximum work capacity (W-max), and 20 min after co mpletion of work. Lactate and pyruvate concentrations increased signif icantly from rest to exercise at two-thirds W-max [similar to 72% of p eak oxygen consumption (VO2peak)]. Whereas greater increments in lacta te concentration were seen with groups of increasing age, exercise-rel ated increments in pyruvate concentrations were no different among age groups. There was a significant rise in L:P ratio on exercise, with g reater increments found from the youngest to the oldest group. There w ere no sex differences. We concluded that in healthy children exercisi ng at similar to 70% of VO2peak there is a rise in blood lactate conce ntration in excess of that of pyruvate, such that the L:P ratio rises to a degree determined by age. This suggests age dependent changes, pe rhaps coincident with puberty, in pathways involved in lactate product ion and/or elimination.