MARSH, R.L.; ELLERBY, D.J.; BUCHANAN, C.I.; CARR, F.A.; HENRY, H.T.; Northeastern University; Northeastern University; Northeastern University; Northeastern University; Northeastern University: Energetic cost of swing and stance phases during running as indicated by muscle blood flow.

Discussions on the cost of swing versus stance phase during running have taken place largely in the absence of data that would indicate specifically how much energy is being consumed by muscles active during different parts in the stride. Mechanical measurements indicate that considerable energy could be used to accelerate the limbs during swing, but some researchers have suggested that most or all of this energy is stored and recovered elastically. We have addressed this problem by measuring blood flow to all the hindlimb muscles of running guinea fowl using colored microspheres injected into the systemic circulation. A considerable body of data indicates that muscle blood flow is recruited by local mechanisms proportional to the local metabolic rate. Our data on guinea fowl supports this idea that muscle flow is highly specific and proportional to muscle metabolic rate. Our blood flow data, in conjunction with electromygraphic activity indicating when the muscles are active, suggests that muscles active during swing use approximately 30% of the energy consumed by the legs. Although the cost of swing is considerably less than the cost of stance, at least in guinea fowl, this cost is a substantial part of the overall cost of running. Supported by NIH grant AR47337.