Exercise Intensities and Isocalorification of Energy Expenditure

Running exercise intensity was determined by %HR_max. In the current study, LI exercise was defined as 40% VO_2max (∼63% HR_max), MI as 60% VO_2max (∼75% HR_max), and HI as 85% VO_2max (∼91% HR_max). In sessions 2 and 3, participants warmed up for 5 min so that their %HR_max became stable at the correct intensity before starting the CCPT test whilst running. HI exercise consisted of 10 min warm-up at 40% VO_2max (∼63% HR_max), followed by 4 min × 4 min interval session at 85% VO_2max with 3 min × 3 min recoveries at 40% VO_2max between each interval effort. The HI protocol ended with a 3 min cool-down session at 40% VO_2max. To equate total work performed by the three exercise intensities for sessions 4–6, total oxygen cost for every individual was calculated from the HI protocol (22 min at 40% VO_2max and 16 min at 85% VO_2max), similarly to what has been shown before (Rognmo et al., 2004):

To calculate the running times at LI and MI with the same oxygen cost as the HI protocol: