The effects of muscle mass on metabolic responses and perceived exertion during prolonged exercise

This study compared the effects of arm and leg (A+L) and leg (L) exercise on metabolic responses and ratings of perceived exertion, using an air-braked cycle ergometer (Schwinn Air-Dyne). Twelve healthy subjects performed a maximal graded exercise tests with L and A+L. Subsequently, they performed a 30 minute exercise bout at 70% of VO_2max using L and A+L. Oxygen uptake (VO₂), ventilation (V_E), respiratory exchange ratio (R), heart rate (HR) and ratings of perceived exertion (RPE) were measured throughout all tests. Venous blood samples were taken 3-5 minutes after incremental test completion and at 10 minute intervals during the endurance test. Using planned contrasts, it was determined that RPE and R values for A+L exercise were significantly lower (p < 0.05) compared to L exercise at 147, 171, 196, and 221 Watts during the incremental test. In addition, VO₂ was higher for A+L versus L exercise at 74, 122, 147, 171, and 196 Watts (p<0.05). RPE, blood LA, and R values were significantly higher (p < 0.05) for L compared to A+L exercise throughout the endurance test. These results demonstrate that during prolonged work at moderately high intensities, RPE, R, and blood LA are lower for combined A+L versus L work. Further, the decrease in RPE appears to be due to a reduction in peripheral factors (blood LA and muscle strain) during A+L exercise.

Key words: ratings of perceived exertion, oxygen uptake, VO_2max, blood lactate accumulation, respiratory exchange ratio, heart rate, and power output.