Studies on the Peripheral Circulation and Metabolism in Man I. Oxygen utilization and lactate‐pyruvate formation in the legs at rest and during exercise in healthy subjects

Abstract Arterial and femoral venous oxygen and lactate‐pyruvate was studied at rest, during and after leg exercise in 15 healthy human males. At rest in the supine position the femoral venous oxygen saturation was 53–81 per cent. A few minutes after starting work, the venous oxygen saturation was 22–42 per cent and a slight but steady decrease was observed on continued work. Five minutes after work, the venous oxygen saturation was significantly higher than at rest before work. The pH of the femoral venous blood decreased from mean 7.41 to 7.25 at maximal load. The venous lactate rose during exercise to 4.45–8.66 mM/liter and the venous‐arterial lactate difference to mean 0.85 mM/liter at a heart rate of 160–187/minute. After exercise the lactate decreased successively in most cases but had even 30 min later not reached the initial level before work. The venous pyruvate concentration was 0.09‐0.15 mM/liter at rest, and increased successively during exercise to 0.22‐0.35 mM/liter at the highest loads. A further increase in pyruvate was obtained during the first minutes after work. The increase in“excess of lactate”, as calculated from the lactate‐pyruvate ratio, during exercise was practically parallel to that in total lactate, indicating that during work the total lactate is a good indicator of the adequacy of oxygen supply to the tissues. After exercise, however, there was a discrepancy between the total and excess of lactate, the latter decreasing much more rapidly. No difference was obtained between older and younger subjects concerning increase in pulse rate or changes in oxygen saturation and blood lactate‐pyruvate during exercise. After work lactate decreased more slowly in the older subjects than in the younger.