Acute, short- and medium-term cardiometabolic outcomes of high-intensity interval training compared to moderate-intensity continuous training in men living with type 2 diabetes
Wormgoor, Shohn Gerhard
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Type 2 diabetes (T2D) is a progressive disease, requiring the adoption of behaviours to help delay the progression of life-threatening diabetic complications. Literature indicates high-intensity interval training (HIIT) as a suitable option, in the short-term, for pursuing improved cardiometabolic health in individuals with T2D. However, no randomised controlled trial (RCT) has been conducted using HIIT combined with resistance training (HIIT+RT) to determine the glycaemic control and markers of macro- and microvascular complication effects in people with T2D - nor compared the durability of such effects. The study aimed to compare the acute, short- and medium-term effects of HIIT+RT to moderate-intensity continuous training (MICT+RT), on glucose control and diabetic complication markers. My study recruited T2D men about to exercise in a real-world setting and, firstly, compared the acute physiological responses (APR) to a HIIT+RT or MICT+RT session; secondly, compared the short-term effects of a 12-week structured intervention of either HIIT+RT or MICT+RT on glucose control and complication markers; and finally, compared the medium-term durability of benefits from such training interventions after a 6-month follow-up. Twenty-three men having moderate-duration T2D presented as sedentary, class II obese (≥35.0 kg/m2), and while taking prescribed medications had elevated glycated haemoglobin (HbA1c) and were pre-hypertensive. Participants performed supervised MICT+RT (progressing to 26-min at 55% maximum estimated workload [eWLmax]) or HIIT+RT (progressing to two variations in which twelve 1-min bouts at 95% eWLmax interspersed with 1-min recovery bouts, alternated with eight 30-sec bouts at 120% eWLmax interspersed with 2:15 min recovery bouts). In assessing the APR, peak heart rate, workload and perceived exertion were higher for HIIT+RT (P=0.04, P<0.001 and P<0.001, respectively), although energy expenditure and peak systolic and diastolic blood pressure responses were similar between groups (P=0.47, P=0.71, P=0.56, respectively). The acute blood glucose responses were similar across all time points (P>0.05). However, there were acute exaggerated responses (using exercise termination indicators) reported to a similar extent (P=0.39) for both MICT+RT (64%) and HIIT+RT (36%) participants. To account for fixed and random effects within the study sample, mixed-effect models were used to determine significance of change and to evaluate group*time interactions. Beyond improvements in aerobic capacity (P<0.001) for both groups, both training modalities elicited similar group*time interactions (P>0.05) while experiencing benefits for HbA1c (P=0.01), subcutaneous adiposity (P<0.001) and heart rate variability (P=0.02) during the 12-week intervention. Adiposity (P<0.001) and aerobic capacity (P<0.001) were significantly maintained in both groups at the 6-month follow-up. In addition, during the interventions, SPs in both MICT+RT and HIIT+RT experienced favourable reductions in medication usage. The study reported inter-individual variability of change, exaggerated physiological responses and the precautionary respite afforded to the participants. The findings appear to indicate that, over the short- or medium-term, HIIT+RT is not superior to MICT+RT for the improvements experienced in both groups for HbA1c, subcutaneous adiposity and heart rate variability. This indicates that current guidelines are efficacious and exercise professionals can be confident including MICT+RT (cognisant of appropriate supervision) into their training prescriptions to help men with T2D reduce the progression of macro- and microvascular complication markers.