Hypothesis: local vascular regulation is a key to flow limited muscle function.

The ability of canine oxidative skeletal muscle in situ to maintain developed isometric force is flow limited during twitch contractions at greater than 3 Hz. This limitation implies a mismatching of blood flow and the metabolic rate. The blood flow past a muscle cell is determined by the number of capillaries per fibre, the vascular conductance, the capillaries perfused and vascular autoregulation. Of these, capillary number is regulated on a time scale of days while the other three require seconds to minutes. Each of the regulatory systems involves hypoxia, adenosine and the eicosanoids as contributing factors which would predict that regulatory systems working on the same time scale should change in parallel. This does not appear to be the case at high metabolic rates. The resulting mismatching of flow and metabolism accelerates the fatigue process. This peripheral vascular limitation can exist without a central cardiovascular limit being reached.