Partitioning locomotor energy use among and within muscles Muscle blood flow as a measure of muscle oxygen consumption

Linking the mechanics and energetics of locomotion in vertebrates has been hampered by a lack of information regarding the energy use of individual skeletal muscles in vivo. Here, we present a review of the available data concerning the relationship between the rates of skeletal muscle blood flow and oxygen consumption (V(O2)). In active muscle, during aerobically supported exercise, there is a linear relationship between these variables, irrespective of the muscle fiber type and intensity of exercise through most of the aerobic exercise range. We conclude that the rate of blood flow is the best available indicator of aerobic metabolic rate in multiple individual muscles or regions of muscles during locomotion. The practical considerations of using the injectable microsphere technique to measure muscle blood flow in this context are discussed.