Skeletal muscle: master or slave of the cardiovascular system?

Skeletal muscle and cardiovascular system responses to exercise are so clos ely entwined that it is often difficult to determine the effector from the affector. The purpose of this manuscript and its companion papers is to hig hlight (and perhaps assist in unraveling) the interdependency between skele tal muscle and the cardiovascular system in both chronic and acute exercise . Specifically, we elucidate four main areas: 1) how a finite cardiac outpu t is allocated to a large and demanding mass of skeletal muscle, 2) whether maximal muscle oxygen uptake is determined peripherally or centrally, 3) w hether blood flow or muscle metabolism set the kinetic response to the star t of exercise, and 4) the matching of structural adaptations in muscle and the microcirculation in response to exercise. This manuscript, the product of an American College of Sports Medicine Symposium, unites the thoughts an d findings of four researchers, each with different interests and perspecti ves, but with the common intent to better understand the interaction betwee n oxygen supply and metabolic demand during exercise.