The effects of two weeks low-volume self-regulated high-intensity interval training on cardiorespiratory fitness, exercise enjoyment, and intentions to repeat

This study investigated the effect of low-volume self-regulated high-intensity interval training (SR-HIIT) on cardiorespiratory fitness (CRF), exercise enjoyment, and intentions to repeat. Ten untrained, physically active adults (five males and five females, age: 20.3 ± 0.5 years) undertook a 2-week control period followed by 2-weeks SR-HIIT (6 x 10 min cycle ergometer sessions). Sessions involved alternate bouts at a rating of perceived exertion of 17 (work) and 11 (recovery), with bout durations self-regulated by the participant. Maximal aerobic capacity showed a small increase from post-control (3.14 ± 1.03 L.min-1) to post-training (3.45 ± 1.14 L.min-1; ̅diff 0.31, 95%CI 0.06 L.min-1, d = 0.28, 95%CL 0.11, 0.45). First ventilatory threshold showed a large increase from post-control (65.6 ± 2.1% V̇O2max) to post-training (68.0 ± 2.4% V̇O2max; ̅diff 2.4, 95%CI 1.2%, d = 0.96, 95%CL 0.27, 1.62). Post-exercise enjoyment showed small (̅diff 3.5, 95%CI 8.1 AU, d = 0.31) and medium (̅diff 6.9, 95%CI 6.7 AU, d = 0.68) increases from SR-HIIT session 1-3 and 3-6, respectively. There were trivial to medium increases in intention to repeat SR-HIIT once per week (d = 0.06 to 0.63) and three times per week (d = 0.28 to 0.60). Low-volume SR-HIIT elicits meaningful improvements in CRF, is enjoyable, and facilitates good intentions to repeat, and may be an additional option for implementing HIIT to improve general population health and fitness