When Moderate Becomes Unpleasant and Intense Is Manageable: Exercise Intensity and Duration Interact to Regulate Exercise Enjoyment and Changes in Affective Valence.

Exercise at higher intensities has been hypothesized to lead to greater decreases in affective valence, negatively impacting exercise enjoyment and adherence. Thus, findings that high-intensity interval training and sprint interval training (SIT) may be enjoyed more than moderate-intensity continuous training appear paradoxical. The aim of the present study was to examine whether this can be explained by an Intensity × Duration interaction effect. Twenty-nine participants (18 women; mean [standard deviation] age: 24 [5] years, body mass index: 23.4 [3.2] kg/m2, V˙O2max: 39.5 [6.5] ml·kg-1·min-1) performed five cycling sessions involving either 30 min at 80%, 100%, or 110% of the ventilatory threshold (VT), SIT (22-min session including 4 × 30-s all-out sprints), or reduced-exertion high-intensity interval training (REHIT; 10-min session including 2 × 20-s all-out sprints). The decrease in affective valence during exercise was faster with higher intensities, but the brief duration of supramaximal sprints attenuated the absolute drop (no significant differences between REHIT, -0.7 [0.5]; 80% VT, -0.7 [0.5]; and 100% VT, -1.3 [0.6]; significantly greater decreases during SIT, -1.9 [0.6] and 110% VT, -3.0 [0.7]; both p < .01 vs. REHIT and 80% VT). REHIT involved lower exposure to reduced affect compared with the other trials (p < .001), and greater remembered enjoyment (physical activity enjoyment scale: 88 [16] compared with SIT, 71 [22], p < .001, and 110% VT, 73 [20], p = .003; no significance compared with 80% VT, 82 [18] or 100% VT, 76 [21]). Seventy-two percent of participants expressed a preference for REHIT. In conclusion, we provide evidence for an Intensity × Duration interaction effect for changes in affective valence during exercise. This explains the paradoxical finding that despite more rapid decreases in affective valence during exercise, high-intensity interval training/SIT can be enjoyed more than moderate-intensity continuous training.