Int J Sports Physiol Perform. 2017 Jan 04;:1-22
The purpose of this study was to compare physiological responses and perceived exertion among well trained cyclists (n=63) performing three different high intensity interval training (HIIT) prescriptions differing in work bout duration and accumulated duration, but all prescribed with maximal session effort. Data are presented as mean(Standard Deviation). Subjects (male, 38(8) y, VO2peak 62(6) mL.kg(-1) min(-1)) completed up to 24 HIIT sessions over 12 weeks as part of a training intervention study. Sessions were prescribed as 4x16 min, 4x8 min, or 4x4 min with 2 min recovery periods (8 sessions of each prescription, balanced over time). Power output, HR, and RPE were collected during and after each work bout. Session RPE was reported after each session. Blood lactate samples were collected throughout the 12 weeks. Physiological and perceptual responses during > 1400 training sessions were analyzed. HIIT sessions were performed at 95(5), 106(5), and 117(6)% of 40min TT power during 4x16, 4x8, and 4x4 min sessions respectively with peak HR in each work bout averaging 89(2), 91(2) and 94(2)% HRpeak. Blood lactate concentration was 4.7(1.6), 9.2(2.4) and 12.7(2.7) mMol.L(-1). Despite the common prescription of maximal session effort, RPE and sRPE increased with decreasing accumulated work duration (AWD), tracking relative HR. Only 8% of 4x16 min sessions reached RPE 19-20, versus 61% of 4x4 min sessions. We conclude that within the HIIT duration range, performing at "maximal session effort" over a reduced AWD is associated with higher perceived exertion both acutely and post exercise. This may have important implications for HIIT prescription choices.