The effect of a high intensity interval training program on health-related outcomes in older adults

Low levels of regular physical activity in older adults may lead to accelerated declines in overall health and functional capacity. Moderate continuous aerobic training (MCAT) has generally been recommended to combat the prevalence of lifestyle diseases in older adults, however adherence rates to this type of training are low, which necessitates the need for a viable alternative. High intensity interval training (HIIT) has been successfully implemented in young and clinical populations, yet there is limited evidence that advocates the use of HIIT in older adults to attain health benefits. Thus, the primary aim of this study was to determine the effect of HIIT on health-related outcomes in older adults. Twenty four sedentary older adults (age 62.8 ± 6.5 years; 37.3 ± 7.6 % body fat) volunteered for the 16 week HIIT and MCAT intervention. Participants were randomly assigned into 2 experimental groups: HIIT or MCAT. HIIT consisted of 4 stages of 4 minutes treadmill running at 90-95% of age predicted maximum heart rate (APMHR) with 3 minutes of active recovery between intervals. MCAT consisted of treadmill walking for 47 minutes at 70-75% of APMHR. The participants were tested for body composition, insulin resistance, blood lipids, functional capacity, cardiorespiratory fitness and quality of life, pre and post intervention. The pre-post intra-group changes were compared using paired t-tests and the magnitude of differences between groups was calculated using Cohen’s effect sizes. In addition the time x group interaction effects between HIIT and MCAT were calculated using 2x2 ANOVA. Both HIIT and MCAT elicited significant improvements in body fat percentage (HIIT: 1.9% vs MCAT: 2.2%), sagittal abdominal diameter (HIIT: 1.7cm vs MCAT: 1.6cm), Stellenbosch University https://scholar.sun.ac.za iii waist circumference (HIIT: 4.1cm vs MCAT: 4.4cm) and hip circumference (HIIT: 5cm vs MCAT: 5.1cm) (p < 0.05). In addition, HIIT significantly improved fasting plasma glucose (HIIT: 0.3mmol/l vs MCAT: 0.1mmol/l) and cardiorespiratory fitness (HIIT: 7.6ml/kg/min vs MCAT: 1.8ml/kg/min) relative to MCAT (p < 0.05). Although not statistically significant, HIIT also exerted a greater practically significant improvement on the lipid profile and functional capacity relative to MCAT (ES = 0.41, 0.30 respectively). In contrast, MCAT succeeded in improving quality of life to a greater extent relative to HIIT, especially with regards to bodily pain (ES = 0.64). These results demonstrate that HIIT is a viable, tolerable and beneficial form of exercise in older adults. Although both HIIT and MCAT are able to significantly improve body composition, HIIT had a greater practically significant effect on insulin resistance, functional capacity and cardiorespiratory fitness relative to MCAT in older adults. These benefits translate into a reduced cardiovascular disease risk as well as an improvement in activities of daily living. Despite HIIT inducing a greater amount of bodily pain in participants, HIIT still elicited favourable changes in health outcomes.National Research Foundatio