DISTINCTIVE EFFECTS OF 3 DIFFERENT MODES OF EXERCISE ON OXYGEN-UPTAKE, HEART-RATE AND BLOOD LACTATE AND PYRUVATE

We intended to investigate the effects of different modes of exercise on oxygen uptake (VO2), the heart rate and the levels of lactate and pyruvate in venous blood. For this, untrained male subjects performed three modes of exercise with a treadmill (TR), a bicycle ergometer (UP) and a supine leg ergometer (SU). The percentage of maximal oxygen uptake (% VO2max) and VO2/weight for TR were significantly higher than those for UP or SU at lactate levels of 2, 3 and 4 mmol/l. The heart rate was also higher for TR than for SU at these lactate levels. The correlations of blood lactate with % VO2max, VO2/weight and the heart rate were significant for TR and SU, but not for UP. Blood lactate levels were lower for TR than for SU or UP at 60, 70, 80% VO2max, whereas the values for UP were lower than those for SU only at 60% VO2max. Blood pyruvate levels were always lower for TR than for SU. The ratios of lactate/pyruvate differed for TR and SU only at 60% VO2max. For a given mode of exercise, blood lactate and the ratio of lactate/pyruvate increased with an increase in % VO2max, but those of pyruvate did not. These results reveal that the relationships between any two of lactate, pyruvate, VO2 and the heart rate are different at different modes of exercise, and that blood lactate depends on adaptation of muscles to a mode of exercise rather than on the quantity of muscles mobilized.