Cardiorespiratory Responses to Constant and Varied-Load Interval Training Sessions

Int J Sports Physiol Perform. 2021 Jul 1;16(7):1021-1028. doi: 10.1123/ijspp.2020-0104. Epub 2021 Feb 19.


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˙O2max] 62 [6] mL·kg-1·min-1) and 15 runners (V˙O2max 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˙O2max, P = .002) but not in running (91 [4]% vs 90 [4]% of V˙O2max, P = .38), as was the time spent >90% of V˙O2max 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.

Keywords: cycling; endurance; high-intensity interval training; running.

MeSH terms

  • Heart Rate
  • High-Intensity Interval Training*
  • Humans
  • Oxygen Consumption
  • Pulmonary Ventilation
  • Running*