Figure 1. Mean and peak heart rate responses (expressed as %HRmax determined in the VO2max test) over all training sessions for HIIT-R and HIIT-F. HIIT-R, high-intensity interval training running group; HIIT-F, high-intensity interval training functional group; %HRpeakHIIT, peak heart rate during the training session, expressed as a % of the HRmax determined by the treadmill test; %HRmeanHIIT, mean heart rate during the training session, expressed as a % of the HRmax determined by the treadmill test; *indicates statistically significant result (between-groups).