Cardiorespiratory fitness and accelerometer-determined physical activity following one year of free-living high-intensity interval training and moderate-intensity continuous training: a randomized trial

• Published in: The international journal of behavioral nutrition and physical activity Vol. 17; no. 1; p. 25
• Main Authors: Jung, M E, Locke, S R, Bourne, J E, Beauchamp, M R, Lee, T, Singer, J, MacPherson, M, Barry, J, Jones, C, Little, J P
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 26-02-2020; BioMed Central; BMC
• Subjects: Accelerometers; Cardiorespiratory fitness; Circulatory system; Counseling; Cycling; Diabetes; Exercise; Exercise intensity; Exercise tests; Fitness training programs; Health aspects; Health behavior; Health behaviour change; Heart rate; High intensity interval training; Interval training; Laboratories; Medical examination; Methods; Obesity; Physical activity adherence; Physical fitness; Physiological aspects; Physiology; Respiratory system; Type 2 diabetes; Canada; United States > US; Physical activity adherence; Health behaviour change; High-intensity interval training; Cardiorespiratory fitness
• ISSN: 1479-5868; 1479-5868
• DOI: 10.1186/s12966-020-00933-8

Free-living adherence to high-intensity interval training (HIIT) has not been adequately tested. This randomized trial examined changes in cardiorespiratory fitness (CRF) and accelerometer-measured purposeful physical activity over 12 months of free-living HIIT versus moderate-intensity continuous training (MICT).
Ninety-nine previously low-active participants with overweight/obesity were randomly assigned to HIIT (n = 47) or MICT (n = 52). Both interventions were combined with evidence-based behaviour change counselling consisting of 7 sessions over 2 weeks. Individuals in HIIT were prescribed 10 X 1-min interval-based exercise 3 times per week (totalling 75 min) whereas individuals in MICT were prescribed 150 min of steady-state exercise per week (50 mins 3 times per week). Using a maximal cycling test to exhaustion with expired gas analyses, CRF was assessed at baseline and after 6 and 12 months of free-living exercise. Moderate-to-vigorous physical activity of 10+ minutes (MVPA10+) was assessed by 7-day accelerometry at baseline, 3, 6, 9, and 12 months. Intention to treat analyses were conducted using linear mixed models.
CRF was improved over the 12 months relative to baseline in both HIIT (+ 0.15 l/min, 95% CI 0.08 to 0.23) and MICT (+ 0.11 l/min, 95% CI 0.05 to 0.18). Both groups improved 12-month MVPA10+ above baseline (HIIT: + 36 min/week, 95% CI 17 to 54; MICT: + 69 min/week, 95% CI 49 to 89) with the increase being greater (by 33 min, 95% CI 6 to 60) in MICT (between group difference, P = 0.018).
Despite being prescribed twice as many minutes of exercise and accumulating significantly more purposeful exercise, CRF improvements were similar across 12 months of free-living HIIT and MICT in previously low-active individuals with overweight/obesity.