EFFECT OF MUSCLE CONTRACTION VELOCITY ON CARDIORESPIRATORY RESPONSES DURING REPETITIVE ISOMETRIC AND ISOKINETIC EXERCISE

PURPOSE: We investigated the effects of muscle contraction velocity on cardiorespiratory responses during exercise in human to test the hypothesis that the responses to exercise with slow muscle contraction velocity (close to static exercise) were greater than with fast contraction velocity (close to dynamic exercise). METHOD: Eight males performed repetitive one-leg extension exercise, repeating 0.5-s muscle contraction and 1.0-s relaxation, for 3 minutes at various knee angular velocities of 0, 30, 60, 120, and 180 degree per second (dps). They performed these trials at intensity levels corresponding to 20, 30, and 40% of maximal power at each velocity (% TTI max (=% tension-time index maximal)). RESULT: The increases in oxygen uptake (VO2), heart rate, mean blood pressure, and minute ventilation from the resting level were greater as the muscle contraction velocity increased, compared to a given % TTI max. Linear regression analysis between VO2 and other responses revealed that cardiorespiratory responses were greater at a given VO2 as the muscle contraction velocity increased. CONCLUSION: These results did not support the hypothesis, and suggest that muscle contraction velocity affects the magnitudes of cardiorespiratory responses during both repetitive isometric and repetitive isokinetic exercise, and that energy efficiency is better during mild contraction velocity.