Abstract

To test the hypothesis that maximal 02 uptake (V02max) can be limited by 02 diffusion in the peripheral tissue, we kept 02 delivery (blood flow x arterial 02 content (Ca02)) to maximally contracting muscles equal between 1) low flow-high Ca02 and 2) high flow-low Ca02 conditions. The hypothesis predicts, because of differences in the capillary P02 profile, that the former condition will result in both a higher V02max and muscle effluent venous P02 (Pv02). We studied the relations among V02max, Pv02, and 02 delivery during maximal isometric contractions in isolated, in situ dog gastrocnemius muscle (n = 6) during these two conditions. 02 delivery was matched by varying arterial 02 partial pressure and adjusting flow to the muscle accordingly. A total of 18 matched 02 delivery pairs were obtained. As planned, 02 delivery was not significantly different between the two treatments. In contrast, V02max was significantly higher, as was Pv02 in the low flow-high Ca02 treatment compared with the high flow-low Ca02 treatment. The rate of fatigue was greater in the high flow-low Ca02 condition, as was lactate output from the muscle and muscle lactate concentration. The results of this study show that V02max is not uniquely dependent on 02 delivery and support the hypothesis that V02max can be limited by peripheral tissue 02 diffusion. Verf.-Referat