Vascular control of nutrient delivery by flow redistribution within muscle: implications for exercise and post-exercise muscle metabolism.

There is evidence for non-nutritive flow routes within, or associated with, skeletal muscle. Large capillary-like structures are possible candidates. The proportion of flow distributed between nutritive and non-nutritive routes appears to be tightly regulated and can control muscle metabolism and contraction by regulating delivery and product removal. The portion of flow that is carried by the non-nutritive routes at rest affords a flow reserve for amplifying nutrient delivery as muscle begins to work and may determine post-exercise metabolism. Inappropriate signals, however, may diminish nutritive flow to the detriment of muscle performance and post-exercise recovery. New technologies should allow the identification of the non-nutritive routes.