Affective responses during and after reduced volume high-intensity interval exercise

Purpose: High-intensity interval exercise (HIIE) is a time efficient mode of health-enhancing activity that may appeal to the many individuals who cite limited time as a barrier to exercise. Many HIIE protocols are extremely challenging and generate less positive affect than continuous submaximal exercise. To counter this, reduced volume HIIE protocols have been developed, however the affective responses to these have not been examined. This study compared the acute affective responses during and after reduced volume HIIE, continuous moderate (CM) and continuous high-intensity (CH) exercise. Methods: Twelve healthy, physically active, untrained males participated (mean ± SD age 25 ± 7 y, height 177 ± 7 cm, body mass (BM) 76.5 ± 12.2 kg). In a randomised, Latin-square, crossover fashion, participants completed three exercise sessions: CM exercise (30 min cycling at 85% of ventilatory threshold (VT)), CH exercise (cycling at 105% of VT matched with CM for total work), and HIIE (10 x 6 sec cycle sprints interspersed with 60 sec passive recovery). Affective valence and perceived activation were measured before exercise, at the end of the warm-up, every 20% of exercise time, and 1, 5, 10, and 15 min post-exercise. Affective valence and perceived activation at each time point were represented in the circumplex model. Data were analysed to determine statistical significance, and effect sizes evaluated the magnitude of differences. Results: The CM and CH trials were equal for total work (P = 1.0), but differed statistically in duration and intensity (P < 0.001). The HIIE trial was statistically shorter and involved less work than both continuous trials (P < 0.001). Affective valence during exercise was not statistically influenced by trial (P = 0.35), time (P = 0.06), or trial x time interaction (P = 0.08). However, the largest reduction in affective valence occurred in the CH trial (-1.75 ± 2.42 units), followed by the HIIE (-1.17 ± 1.99 units) and CM trials (-0.42 ± 1.38 units). Affective valence post-exercise was not statistically influenced by trial (P = 0.10) and at 5 min post-exercise statistically exceeded end-exercise values in all trials (P = 0.48). Perceived activation during exercise was statistically greater in the HIIE (P = 0.001) and CH (P = 0.02) trials vs. the CM trial. Circumplex profiles varied by trial, and there was no evidence of negative affect in any trial. Discussion: Affective valence decreased more during the HIIE and CH trials compared to the CM trial, suggesting HIIE is not less aversive than CH. Unsurprisingly, participants reported higher activation during CH and HIIE. In contrast to previous studies, no negative circumplex values were observed during or after HIIE, suggesting that lower volume HIIE is more palatable. The lack of statistical difference between trials in post-exercise affective responses suggests that the affective ‘rebound effect’ is evident for all trials. Conclusion: Although a lower volume HIIE protocol leads to similar reductions in affect as CH exercise, responses remain positive and rebound rapidly. These findings, coupled with the time-efficiency of HIIE, suggest it may be an attractive alternative exercise prescription.