The Influence of Warm Hydrotherapy on the Cardiovascular System and Muscle Relaxation

Five female and five male subjects with no known cardiovascular abnormalities nor any neuromuscular disorders were examined during exercise on a cycle ergometer or a 30 min immersion in warm water with and without exercise to determine the effects of immersion on cardiac output, heart rate, blood pressure, forearm blood flow, muscle blood flow, skin blood flow and muscle relaxation. Muscle relaxation was measured by the resistance to passively moving the leg through a 60° arc and by measurement of the Hoffman (H) reflex. The results of these experiments showed that 1) passive heating caused the greatest relaxation in muscle 2) most of the increase in blood flow to the limb during passive heating or exercise was to skeletal muscle 3) cardiac output increased modestly as did heart rate during passive exposure or light exercise in a therapeutic pool and 4) blood pressure was generally decreased during warm water immersion.