Short

We assessed the short-term effects of varying the volume of high-intensity interval training (HIIT) on psychological and physiological responses of 23 healthy adult males (M？=？21 years; M peak oxygen uptake [VO2peak]？=？47.2 ml·kg？1·min？1). Participants were randomly assigned to low- and very-low-volume HIIT groups and engaged in nine supervised exercise sessions over three weeks. The low-volume HIIT group performed 8-12 60-second work bouts on a cycle ergometer at the peak power output achieved during the incremental test, interspersed by 75 seconds of low-intensity active recovery. The very-low-volume HIIT performed 4-6 work bouts with the same intensity, duration, and rest intervals. During training, participants’ ratings of perceived exertion (Borg Category Ratio-10 scale) and their affective responses (Feeling Scale ？5/+5) during the last 15 seconds of each work bout were recorded. Physiological data were VO2peak, endurance, and anaerobic performance before and after the intervention. Throughout training, participants in the very-low-volume group (relative to the low-volume group) reported lower ratings of perceived exertion in Week 1 (M？=？4.1 vs. M？=？6.3; p？<？.01) and Week 3 (M？=？4.0 vs. M？=？6.2; p？<？.01), and higher affective response in these same two weeks (Week 1: M？=？1.9 vs. M？=？0.3; p？=？.04; Week 3: M？=？2.1 vs. M？=？0.9; p？=？.06). Regarding physical fitness, Wingate peak power increased significantly after training in the very-low-volume HIIT group (M？=？1,049 W vs. M？=？1,222 W; p？<？.05), but not in the low-volume HIIT group (M？=？1,050 W vs. M？=？1,076 W). No significant change was found after training in physiological variables of peak power output, VO2peak, and endurance performance. In summary, in this short-term training period, the very-low-volume HIIT enhanced anaerobic capacity and was perceived as less strenuous and more pleasurable than low-volume HIIT