The effect of a shortened sprint, reduced exertion high-intensity interval training (REHIT) protocol on affective response and peak oxygen uptake

The minimum amount of exercise that has been shown to improve peak oxygen uptake (V̇ O2peak) is reduced-exertion, high-intensity interval training (REHIT) incorporating two 20 s maximal exertion cycle sprints within a 10-min exercise session (Metcalfe et al., 2011, European Journal of Applied Physiology, 112, 2767–2775). However, hedonistic theories of motivation propose that exercise above a certain intensity threshold results in physiological responses that negatively influence affective valence (i.e. increasing sensations of displeasure). This could lead to avoidance of the activity and poor exercise adherence. Given that sensation of exertion is a function of intensity and duration, it is plausible that reducing the time spent ‘sprinting’ may attenuate any negative affect associated with periods of high-intensity exercise. Accordingly, the aims of this study were to investigate affective response to a novel, shortened-sprint REHIT protocol; and to test the effect of this protocol on V̇ O2peak. With institutional ethics approval, 24 men (age 21.2 ± 1.9 years; mass, 80.2 ± 6.8 kg; BMI, 25.5 ± 1.8 kg·m2) were randomly assigned to one of two conditions: (1) shortened-sprint REHIT (8 × 5 s sprints), or (2) traditional REHIT (2 × 20 s sprints). Participants completed 15 exercise sessions over a 5–7-week period, with V̇O2peak determined using a ramp cycling test pre- and post-intervention. Affect and rating of perceived exertion (RPE) were measured during exercise using the Feeling Scale (FS) and the 15-point Borg scale, respectively. Enjoyment was recorded 5-min after cessation of activity using the Exercise Enjoyment Scale. Factorial (condition × time) mixed ANOVA’s were used to compare differences between groups. Affective valence was more favourable for shortened-sprint REHIT compared to traditional REHIT (1.6 ± 0.6 vs. 0.2 ± 1 FS units, respectively; where 1 is ‘fairly good’ and 0 is ‘neutral’; P = 0.001, d =
1.62). Similarly, peak RPE values were lower for shortened sprint REHIT (14.4 ± 0.9 vs. 16.2 ± 1.1, P = 0.001, d = −1.71). However, there was no difference in enjoyment. Compared to baseline, V̇O2peak increased in both groups (6% for shortened-sprint REHIT [d = –0.36] and 9% for traditional REHIT [d = –0.53], both P = 0.01), although there was considerable heterogeneity in training response within each group. The results suggest both conditions improve fitness without overly compromising cognitive and affective response, and as such may be genuinely time-efficient yet tolerable approaches to exercise. The challenge of translating this research into real-world practice remains.