Can reduced-exertion, high-intensity interval training combat the deleterious cardiometabolic effects of a sedentary lifestyle?

Purpose: Reduced-exertion high-intensity interval training (REHIT) has been shown to have positive benefits on health that are comparable to benefits induced by high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), but with significantly less training time. Mechanisms behind this are thought to include increased mitochondrial activity (leading to improved cardiorespiratory fitness) and glycogen depletion and elevated GLUT-4 levels, leading to improved glucose levels. This low-effort, time-saving exercise recommendation could prove useful in attenuating the risk factors of the Metabolic Syndrome (MetS) in sedentary populations. Methods: In a randomized crossover design, ten sedentary subjects (7 F, 3 M) who possessed at least two risk factors for MetS underwent three weeks of thrice-weekly REHIT training (10 min/session) on a CAR.O.L ™ cycle ergometer unit and three weeks of a control period. Before, mid-way, and after the study, VO2 max, blood pressure (SBP and DBP), heart rate, body composition, waist circumference (WC), fasting insulin, fasting glucose, HbA1c, fasting blood lipids, and physical activity were measured. After weeks 1, 2, 4, and 5, fasting blood lipids and glucose and vitals were measured. Results: Two subjects did not complete more than six rides and were not included in the statistical analysis, in addition to one individual that was considered a statistical outlier. No adverse responses to the intervention were reported, and the subjects reported feeling energized after and enjoying most of the rides. HbA1c (-0.47 ± 0.18%; p=0.023) and glucose (-8.0 ± 2.88 mg/dL; p=0.017) were significantly reduced in the REHIT group when compared to the control group. Additionally, the MetS z-score was reduced in 5 of the 7 subjects and, on average, was reduced by 0.69±1.06 in the REHIT group. No significant change was found in VO2 max, fasting insulin, or body fat. Conclusions: Three weeks of thrice-weekly REHIT significantly improved HbA1c and glucose measures, and SBP and WC were notably reduced. REHIT was also effective at reducing the MetS z-score in 5 of the 7 subjects. Workplace-based, unsupervised REHIT exercise is a useful and well-tolerated tool to reduce cardiometabolic risk in a sedentary population.