Muscle blood flow during exercise: the limits of reductionism. Med. Sci. Sports Exerc., Vol. 31, No. 7, pp. 1036-1040, 1999. This paper attempts to integrate some important concepts about the various mechanisms that are thought to cause blood flow to rise during rhythmic exercise. Mechanisms including the muscle pump, substances released by skeletal muscle, substances transported by blood, and factors released by nerves have been postulated to contribute to the rise in muscle blood flow during exercise. Additionally, the factors that initiate the dilation may not be those which sustain it. Although there is normally a close relationship between contractile activity, metabolic rate, and muscle blood flow, this relationship can be disrupted under a variety of circumstances and the active skeletal muscle overperfused. This delinking of flow and metabolism raises important questions about the nature of the vasodilating substances responsible for the rise in blood flow during exercise. We propose that understanding the mechanisms responsible for the "delinking" of flow and metabolism, along with a more synergistic view of current concepts, can provide new insight into the mechanisms which govern exercise hyperemia.
Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905
Submitted for publication February 1998.
Accepted for publication October 1998.
The authors wish to thank Janet Beckman for her secretarial assistance, Tamara Eickhoff for her assistance in preparing the figures. The author's work on this topic has been supported by HL-46493, RR-585, GM-08288, the Mayo Foundation, and the Glen L. and Lyra M. Ebling Cardiology Research Endowment.
Address for correspondence: Michael J. Joyner, M.D., Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail: firstname.lastname@example.org.