Lactate disposal in resting trained and untrained forearm skeletal muscle during high intensity leg exercise

At a given oxygen uptake (VO₂) and exercise intensity blood lactate concentrations are lower following endurance training. While decreased production of lactate by trained skeletal muscle is the commonly accepted cause, the contribution from increased lactate removal, comprising both uptake and metabolic disposal, has been less frequently examined. In the present study the role of resting skeletal muscle in the removal of an arterial lactate load (approximately 11 mmol·-l^-1) generated during high intensity supine leg exercise (20 min at approximately 83% maximal oxygen uptake) was compared in the untrained (UT) and trained (T) forearms of five male squash players. Forearm blood flow and the venoarterial lactate concentration gradient were measured and a modified form of the Fick equation used to determine the relative contributions to lactate removal of passive uptake and metabolic disposal. Significant lactate uptake and disposal were observed in both forearms without any change in forearm VO₂. Neither the quantity of lactate taken up [UT, 344.2 (SEM 118.8) μmol·100 ml^-1; T, 330.3 (SEM 85.3) μmol·100 ml^-1] nor the quantity disposed of [UT, 284.0 (SEM 123.3) μmol·100 ml^-1, approximately 83% of lactate uptake; T, 300.8 (SEM 77.7) μmol·100 ml^-1, approximately 91% of lactate uptake] differed between the two forearms. It is concluded that while significant lactate disposal occurs in resting skeletal muscle during high intensity exercise the lower blood lactate concentrations following endurance training are unlikely to result from an increase in lactate removal by resting trained skeletal muscle.