Cardiorespiratory Responses to Constant and Varied-Load Interval Training Sessions

Abstract

Purpose: To compare the cardiorespiratory responses of a traditional session of high-intensity interval training session with that of a session of similar duration and average load, but with decreasing workload within each bout in cyclists and runners. Methods: A total of 15 cyclists (maximal oxygen uptake [(V)over dotO(2)max] 62 [6] mL.kg(-1).min(-1)) and 15 runners ((V)over dotO(2)max 58 [4] mL.kg(-1).min(-1)) performed both sessions at the maximal common tolerable load on different days. The sessions consisted of four 4-minute intervals interspersed with 3 minutes of active recovery. Power output was held constant for each bout within the traditional day, whereas power started 40 W (2 km.h(-1)) higher and finished 40 W (2 km.h(-1)) lower than average within each bout of the decremental session. Results: Average oxygen uptake during the high-intensity intervals was higher in the decremental session in cycling (89 [4]% vs 86 [5]% of (V)over dotO(2)max, P= .002) but not in running (91 [4]% vs 90 [4]% of (V)over dotO(2)max, P = .38), as was the time spent >90% of (V)over dotO(2)max and the time spent >90% of peak heart rate. Average heart rate (P < .001), pulmonary ventilation (P < .001), and blood lactate concentration (P < .001) were higher during the decremental sessions in both cycling and running. Conclusions: Higher levels of physiological perturbations were achieved during decremental sessions in both cycling and running. These differences were, however, more prominent in cycling, thus making cycling a more attractive modality for testing the effects of a training intervention.