Feasibility of a progressive HIIT model of exercise for patients with Type 2 Diabetes Mellitus enrolled in cardiac rehabilitation

A link exists between Type 2 Diabetes Mellitus (T2DM) and developing cardiovascular disease (CVD). Lifestyle interventions targeting T2DM and CVD are required. Cardiac rehabilitation (CR) offers a multidisciplinary approach for management. High-intensity interval training (HIIT) may provide equivalent benefit compared to moderate-intensity continuous exercise (MICE) in improving cardiorespiratory fitness and glycemic control. HIIT should be considered when prescribing exercise for patients with T2DM; however, feasibility research is required. The objective of this study was to determine the feasibility of progressive HIIT in patients with T2DM. Patients in a 24-week CR program provided research consent at 12-weeks. Feasibility was assessed using intervention adherence, drop-out rate/reason, patient satisfaction and safety. Patients completed the HIIT protocol 3-times/week, at 80-95% HRR. Patients started at stage 1 (10x30-sec high intensity:30-sec recovery) and progressed to Stages 2-4 every 3 weeks according to patient desire and achievement of target work rate without adverse events. Possible progressions included Stage-2 (10x1-min high intensity:1-min recovery), Stage-3 (6x2-min high intensity:2-min recovery) and Stage-4 (4x4-min high intensity:3-min recovery). Twenty-two participants consented to participation and seventeen (60.2±12.4-years) completed the program (23% drop-out rate). Adherence to on-site HIIT sessions was 79% and at-home unsupervised sessions was 70%. Five patients (4 females) remained at Stage 1; 4 (2 females) progressed to Stage 2; 7 (2 females) progressed to Stage 3; and one (male) progressed to Stage 4. Satisfaction surveys revealed patients enjoyed HIIT as much as MICE (p=0.29). No HIIT-related adverse events were reported. Progressive HIIT is feasible, enjoyable, and safe among patients with T2DM.