Purpose: The present investigation was undertaken to compare metabolic and perceptual responses between exercise performed at constant intensity (CON) and with a Spinning(R) protocol of variable intensity (VAR). Method: Fifteen subjects, including seven males and eight 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 protocol that was followed by a 30-min recovery period. Exercise was performed at 67 +/- 3% (means +/- SD) of HRmax in CON. In VAR, the similar intensity (68 +/- 4% HRmax) was also achieved, although the protocol entailed alternating phases of both higher and lower intensity arranged similarly to what is designed for a typical Spinning(R) workout. Oxygen uptake ([latin capital V with dot above]O2) and HR were measured at rest and throughout both exercise and recovery, whereas RPE were recorded during exercise only. Plasma lactate concentrations [La] were determined at rest, the end of exercise, and the end of recovery. Results: No differences in average [latin capital V with dot above]O2, HR, and RPE were found during exercise between CON and VAR. However, average [latin capital V with dot above]O2 and HR were higher (P < 0.05) in VAR than CON (0.33 +/- 0.03 vs 0.26 +/- 0.02 L[middle dot]min-1 and 91 +/- 3 vs 80 +/- 2 beats[middle dot]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 mmol[middle dot]L-1), but became similar at the end of recovery. Conclusion: An exercise regimen in which intensity varies exerts no added effect on metabolic and perceptual responses during exercise as long as the average intensity is kept the same. However, VAR resulted in a greater [latin capital V with dot above]O2 after exercise, and this augmented postexercise oxygen consumption may be mediated in part by elevated plasma [La].
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