HERMAN, C. W., P. R. NAGELKIRK, J. M. PIVARNIK, and C. J. WOMACK. Regulating Oxygen Uptake during High-Intensity Exercise Using Heart Rate and Rating of Perceived Exertion. Med. Sci. Sports Exerc., Vol. 35, No. 10, pp. 1751–1754, 2003.
Purpose: The purpose of this study was to comparatively evaluate the use of heart rate (HR) or rating of perceived exertion (RPE) in eliminating the slow component of oxygen uptake (V̇O2) during high-intensity aerobic exercise.
Methods: Nine sedentary males (age = 23.9 ± 4.6 yr, height = 177.4 ± 10.1 cm, weight = 75.28 ± 12.95 kg) completed three 15-min submaximal exercise cycle ergometer tests based on: 1) constant power output (PO) corresponding to 75% V̇O2max (PO75), 2) HR corresponding with 75% V̇O2max (HR75), and 3) RPE response corresponding with 75% V̇O2max (RPE75). V̇O2, HR, RPE, and blood lactate concentration [La−] were measured during all tests. Data were analyzed using repeated measures analysis of variance, and post hoc means comparisons were performed using a Fisher’s LSD test.
Results: End-exercise V̇O2 was significantly higher than the respective 3-min V̇O2 for the PO75 and RPE75 tests, but not the HR75 test. End-exercise V̇O2 was significantly greater for the PO75 test than both the RPE75 and HR75 tests, but there was no significant difference between end-exercise V̇O2 for the RPE75 and HR75 tests. End-exercise HR and RPE were significantly higher for the PO75 test than both the RPE75 and HR75 tests. There were no significant differences between the RPE75 and HR75 tests for end-exercise HR or end-exercise RPE.
Conclusion: Results suggest using both HR and RPE are effective at reducing the slow component of V̇O2 that occurs during high-intensity exercise.
At the onset of constant-load exercise, oxygen uptake (V̇O2) increases rapidly, followed by a slower rise until steady-state V̇O2 is achieved. However, during exercise where an increase in blood lactate concentration (blood [La−]) is evident, a slow, continuous increase in oxygen uptake occurs instead of steady-state V̇O2 kinetics (17). This delayed increase in V̇O2 is commonly known as the “slow component” of V̇O2 (7) and can result in a profound underestimation of exercise V̇O2. In sedentary populations, lactate threshold (LT) occurs at less than 60% of V̇O2max (16). Therefore, it is likely that a slow component of V̇O2 commonly occurs at frequently prescribed exercise intensities in this population. However, methods to reduce the slow component and elicit steady-state V̇O2 during high-intensity exercise have not been established.
Heart rate (HR) increases in direct proportion to V̇O2 during aerobic exercise (10). Thus, maintaining a constant HR could result in a constant V̇O2. Because the magnitude of the slow component is closely associated with the magnitude of blood [La−] accumulation during exercise (4,7,18), rating of perceived exertion (RPE) is also a promising tool for reducing or eliminating the slow component, as there is a strong association between RPE and blood [La−] that is evident regardless of exercise mode (8) or training status (13). Furthermore, Stoudemire et al. (15) observed that adjusting intensity to elicit a target RPE resulted in constant blood [La−] and V̇O2.
Currently, the American College of Sports Medicine (ACSM) recommends basing aerobic exercise intensity on a power output or velocity, HR, and/or RPE associated with a target V̇O2 (6). However, the comparative utility of manipulating exercise intensity based on HR and RPE to decrease the slow component of V̇O2 has not been evaluated. Therefore, the purpose of this study was to compare the use of HR and RPE in reducing the slow component of V̇O2 during high-intensity exercise.