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Muscle metaboreceptor modulation of cutaneous active vasodilation
C G Crandall1, D P Stephens, J M Johnson
1Institute for Exercise and Environmental Medicine, Presbyterian Hospital, Dallas, TX 75231, USA. Crandall@utsw.swmed.edu
Medicine and Science in Sports and Exercise
|May 5, 1998
Summary
Muscle metaboreceptors, not central command, primarily reduce skin blood flow during exercise in heat. This finding is crucial for understanding thermoregulation and exercise physiology in hyperthermic conditions.
Area of Science:
- Physiology
- Thermoregulation
- Exercise Science
Background:
- Isometric handgrip exercise during hyperthermia decreases cutaneous vascular conductance (CVC).
- This reduction is attributed to the inhibition of the cutaneous active vasodilator system.
Purpose of the Study:
- To determine if muscle metaboreceptors initiate the reduction in CVC during isometric handgrip exercise in hyperthermia.
- To differentiate the roles of muscle metaboreceptors, central command, and mechanoreceptors in this response.
Main Methods:
- Seven subjects performed two bouts of isometric handgrip exercise in hyperthermia with postexercise ischemia (PEI).
- Forearm skin blood flow (laser-Doppler) and sweat rate were measured.
- Adrenergic vasoconstrictor function was blocked with bretylium iontophoresis to isolate active vasodilator function.
Main Results:
- Isometric exercise in hyperthermia reduced CVC at both control and bretylium-treated sites, with reductions persisting through PEI.
- The reduction in CVC was primarily observed at control sites, indicating inhibition of the active vasodilator system.
- Sweat rate increased significantly during exercise and PEI in hyperthermia.
Conclusions:
- Muscle metaboreceptors are the primary mediators of reduced CVC during isometric exercise in hyperthermia.
- Central command and muscle mechanoreceptors appear to have a lesser role in inhibiting the active vasodilator system during hyperthermic exercise.