Muscle recruitment patterns regulate physiological responses during exercise of the same intensity

On different days, 10 men performed 30-min sessions of cycling at 50-55% of their peak oxygen uptake ((V) over dot O-2); one at 40 rpm and another at 80 rpm. Rectal temperature, heart rate (HR), mean arterial pressure (MAP), plasma lactate, glucose, insulin, and cortisol were measured before exercis e, during the 15th and 30th min of exercise, and at 5 and 10 min postexerci se. Rating of perceived exertion (RPE) was assessed 15 and 30 min into exer cise. Electromyography established cadence-specific different intensities o f quadriceps activation during cycling. At minute 30 of exercise and 5 min postexercise, HR was significantly (P < 0.05) greater at 40 rpm than at 80 rpm. MAP remained elevated longer after the 40-rpm than after the 80-rpm bo ut. Similarly, exercise-induced increases in plasma lactate persisted longe r after the 40-rpm bout. Cortisol levels were elevated only at 40 rpm. RPE was higher during the slower cadence. These data indicated that the more pr onounced muscle activation pattern associated with pedaling at 40 rpm resul ted in greater physiological and psychophysiological stress than that obser ved at 80 rpm even though (V) over dot O-2 was the same.