Impact of High-Intensity Interval Training on Different Slopes on Aerobic Performance: A Randomized Controlled Trial

This study investigated the impact of six high-intensity interval training (HIIT) running sessions on 1% or 10% slopes on various physiological and performance parameters in 25 men. The participants underwent assessments of VO2max, time to exhaustion on 1% slope (TLim1%), and time to exhaustion on 10% slope (TLim10%) in the initial three visits. They were then randomly assigned to control (CON), HIIT on 1% slope (GT1%), or HIIT on 10% slope (GT10%) groups. Over three weeks, participants performed six HIIT sessions with equalized workload based on their individual maximal oxygen uptake (vVO2max). The sessions comprised 50% of TLim, with a 1:1 ratio of exercise to recovery at 50% vVO2max. The results indicated significant improvements in VO2max and peak velocity (VPeak) after HIIT on both slopes. Heart rate (HR) differed between sessions for GT1%, while no significant differences were observed for GT10%. Ratings of perceived exertion (RPE) were significantly reduced for GT1% after the third session, with a similar trend for GT10%. In summary, six HIIT sessions on a 1% or 10% slope effectively enhanced VO2max and VPeak, but there was no improvement in TLim performance, suggesting no adaptive transfer between training groups.