The purpose of this study was to compare physiological responses and perceived exertion among well-trained cyclists (n = 63) performing 3 different high-intensity interval-training (HIIT) prescriptions differing in work-bout duration and accumulated duration but all prescribed with maximal session effort. Subjects (male, mean ± SD 38 ± 8 y, VO 2peak 62 ± 6 mL · kg -1 · min -1 ) completed up to 24 HIIT sessions over 12 wk as part of a training-intervention study. Sessions were prescribed as 4 × 16, 4 × 8, or 4 × 4 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 wk. Physiological and perceptual responses during >1400 training sessions were analyzed. HIIT sessions were performed at 95% ± 5%, 106% ± 5%, and 117% ± 6% of 40-min time-trial power during 4 × 16-, 4 × 8-, and 4 × 4-min sessions, respectively, with peak HR in each work bout averaging 89% ± 2%, 91% ± 2%, and 94% ± 2% HR peak . Blood lactate concentrations were 4.7 ± 1.6, 9.2 ± 2.4, and 12.7 ± 2.7 mmol/L. Despite the common prescription of maximal session effort, RPE and sRPE increased with decreasing accumulated work duration (AWD), tracking relative HR. Only 8% of 4 × 16-min sessions reached RPE 19-20, vs 61% of 4 × 4-min sessions. The authors 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 postexercise. This may have important implications for HIIT prescription choices.
Keywords: perceived exertion, session RPE, training load, endurance athletes, cyclingIt is generally accepted that successful endurance athletes must balance a large overall training frequency and volume of training with regular exposure to demanding high-intensity interval-training sessions (HIIT), characterized by repeated work bouts in the 85% to 100% VO 2 max range. HIIT sessions are typically prescribed as a fixed number of repetitions of a given duration/distance, separated by fixed recovery periods (eg, 4 × 8 min, 2-min recovery). The work bout duration, recovery period, and accumulated work duration (AWD) of a HIIT prescription all have independent influences on physiological responses. [1][2][3] We have previously suggested that an athlete's execution of an interval training prescription can be likened to solving for the unknown value in an algebraic equation; work bout duration, rest period duration, and accumulated work duration are known values and average work intensity is the unknown value "solved for" by the athlete. 1-3 HIIT sessions often approximate a maximum training effort. The motivated athlete's solution of the intervaltraining prescription is a pacing process guided by perception of effort during work periods and perception of recovery during rest periods.Others and we have recently compared different HIIT work intensity × AWD combinations, ...