Figure 1. Maximal running speed (VIFT), peak heart rate (HRpeak), blood lactate ([La]b) and rating of perceived exertion (RPE) reached with each protocol, expressed as a percentage of the values reached at the end of the original 30-15IFT. *: p < 0.05 vs. 30-15IFT, †: p < 0.05 vs. 30-15IFT-LINE, ‡: difference vs. 30-15IFT-LINE with effect size considered as moderate (>0.5)