Assessing the feasibility of a reduced exertion, low-volume, high-intensity interval training (HIT) protocol: a pilot study’ Journal of Sports Sciences

Divergence between the evolutionary design of our genome and lifestyle triggers cardiometabolic dis- ease, including diabetes mellitus. Various iterations of low-volume, high-intensity interval training (HIT) can improve risk factors in a manner considered more time-efficient than traditional exercise guide- lines. However, the intensity of HIT may present another barrier to participation. Reduced-exertion HIT has shown beneficial effects with relatively low ratings of perceived exertion (RPE) in healthy young participants (Metcalfe et al., 2011,European Journal of Applied Physiology, 112, 2767–2775). The aim of this study was to replicate thisfinding to assess fea- sibility for a larger trial using diabetic patients. With institutional ethics approval, 11 recreationally active participants (3 females, 8 males; age 22.3 ± 7.3 years; stature 1.73 ± 0.1 m; mass 71.9 ± 13.6 kg; BMI 23.8 ± 2.2 kg · m −2 ) (mean ± SD) took part in an HIT intervention consisting 10 min of cycling at 60 W interspersed with 2 × 10–20 s cycling sprints against a braking force equal to 7.5% of body weight. The number of sprints increased over the course of the intervention (2 × 10 s in week 1; 2 × 15 s in weeks 2–3 and 2 × 20 s in week 4). A warm-up (3 min at 30–60 W) and cool down (3 min at 30 W) were also included. Participants performed this activity two to three times per week, resulting in a total duration of exercise per week of 20–30 min. RPE was reported immediately after completion of each HIT session. Whole blood fasting glucose, peak oxygen uptake and body composition were also mea- sured before and after the 4-week intervention. HIT resulted in higher average RPE values (17 ± 1) than those reported by Metcalfe et al. (~13 ± 1). VO 2peak was increased post-intervention (49.27 ± 9.17 ml · kg −1 · min −1 [95% CI 43.11–55.43]) compared to baseline (48.27 ± 9.23 ml · kg −1 · min −1 [95% CI 42.07–54.47]) (P= 0.02). However, fasting glucose and body composition were not different. The results suggest that short-duration (4 weeks) reduced-exertion HIT can improve aerobic capacity. However, the intensity of the protocol might be intolerable for most people, presenting a significant barrier to exercise for lessfit patients with conditions such as diabetes. The volume–intensity relationship of HIT could be consideredad infinitum; however, the acceptability of the activity to those for whom the intervention is intended needs consideration.