A New Measurement of Tissue Capillarity: the Capillary-to-fibre Perimeter Exchange Index

The surface area of contact between capillaries and muscle fibres has been suggested to be the site of greatest oxygen flux density in the movement of oxygen from the capillaries to the muscle fibres. A new measurement of tissue capillarity, designed specifically for use on non-perfusion fixed muscle tissue (i.e., that obtained via needle biopsy), is presented that describes the capillary supply from this perspective. The Capillary-to-Fibre Perimeter Exchange Index (the CFPE Index) is derived as the quotient of the individual capillary-to-fibre ratio (i.e., the capillary-to-fibre ratio calculated for each fibre individually) and the fibre perimeter. This method is suggested to provide a means of quantitating potential alterations in the capacity for oxygen flux (e.g., as may occur in response to a training intervention) and any carrier- or receptor-mediated aspect of blood-tissue exchange between the capillaries and muscle-fibres (e.g., insulin or glucose delivery).