Oxygen Transport in Skeletal Muscle: How Many Blood Capillaries Surround Each Fibre?
Implicit in a number of recent studies on the capillary bed in skeletal muscle is the idea that exercise training (1,2,3) or adaptation to the chronic hypoxia of high altitude (4,5) might lead to a compensatory increase in capillary density per mm2 of cross-section. Although such an increase might occur without an actual change in the ratio of capillaries to fibres (C/F ratio) simply as a result of the fibres growing smaller in diameter, the underlying assumption is that the C/F ratio might itself increase and that in some way this would lead to improved oxygenation of the tissue. This is a difficult concept to accept since blood capillaries, which run parallel to the fibres, are never found within the fibres themselves but are located around the perimeter of each fibre. The question we have to ask ourselves is this: how many capillaries are needed around the perimeter of a muscle fibre in order to provide uniform O2 transport to that fibre?
KeywordsMethylene Blue Tissue Oxygenation Oxygen Transport Capillary Density Striate Muscle Fibre
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