The body as a bioenergetic system--lessons from systems engineering and comparative physiology.

This introductory review considers some concepts of energy supply and demand from the perspective of a systems engineer looking at comparative physiology. The non-steady-state response of oxygen uptake shows major differences between animal species. Similarly, maximal oxygen uptake shows between-species differences. It is suggested that the systems engineering approach could help in understanding questions concerning the interrelationship of these observations.