Leg blood flow during exercise in man in relation to muscle fibre composition.

Fibre composition in the vastus lateralis muscle, leg blood flow, oxygen uptake and respiratory exchange ratio were determined in 12 healthy male volunteers during submaximal exercise (50% of V02 max). The percentage of slow-twitch fibres varied from 26 to 66. Mean leg blood flow during exercise was 4.68 +/- 0.191.min-1. The blood flow and respiratory exchange ratio correlated positively to the percentage of slow-twitch fibres in the vastus muscles. No correlation was found between the muscle fibre composition and either oxygen uptake heart rate or mechanical efficiency. The results with a dependence of muscle blood flow and carbon dioxide release to muscle fibre composition support the view that the arrangement of the vascular bed and blood supply differ between fast-twitch and slow-twitch muscle fibres in humans.