Comparisons Between Exercise of Constant and Variable Intensity

Abstract

1899 An exercise regimen in which intensity varies has become popular within recent years. However, whether it is more demanding than an equivalent exercise of constant intensity remains unknown. Purpose: The present investigation was undertaken to compare physiological and perceptual responses between exercise of constant (CON) and variable intensity (VAR). Method: Fifteen subjects including 7 males and 8 females (23 ± 5 yr, 72 ± 17 kg, and 171 ± 10 cm) underwent two experimental trials. During each trial, subjects performed a 30-min cycle exercise that was followed by a 30-min recovery period. In CON, exercise was performed at 65% of maximal heart rate (HR max). In VAR, the similar intensity was also achieved, although the protocol entailed alternating phases of both higher (∼80% HRmax) and lower (∼50% HRmax) intensity arranged similarly to what is designed for a typical Spinning™ workout. Oxygen uptake (VO2) and heart rate (HR) were measured throughout both exercise and recovery, whereas ratings of perceived exertion (RPE) were recorded during exercise only. Plasma lactate concentrations [La] were determined at the end of exercise and recovery. Results: No differences in average VO2, HR and RPE were found during exercise between CON and VAR. During recovery, however, both VO2 and HR exhibited a slower decline in VAR and average VO2 and HR were higher (p<0.05) in VAR than CON (0.33 ± 0.03 vs. 0.26 ± 0.02 l.min−1 and 91 ± 3 vs. 80 ± 2 beats. min−1, respectively). [La] was higher (p<0.05) at the end of exercise in VAR than CON (7.2 ± 0.8 vs. 2.7 ± 0.3 mM), but became similar at the end of recovery. Conclusion: An exercise regimen in which intensity varies exerts no added effect upon physiological and perceptual responses during exercise so long as an overall intensity is kept the same. However, this exercise arrangement provokes more persistent elevation in VO2 and HR following exercise and this augmented post-exercise metabolism may be mediated in part by elevated [La].