Abstract

The majority of adults in England are classified as overweight or obese, with sedentary behaviours a contributing factor to an ever-increasing prevalence. Regular exercise and physical activity can combat obesity-related ill-health, with benefits sought from both cardiovascular- and strength-based exercise. As such, both exercise types are included in exercise guidelines, though few individuals meet recommendations. Same-session Concurrent exercise Training (CT) may be the most time-efficient manner to complete both exercise types. The incorporation of High-Intensity Interval Training (HIIT) as the cardiovascular component may further maximise time efficiency and physiological benefit. A review of the literature revealed that it was key to establish a feasible CT protocol, with an enjoyable and repeatable HIIT protocol with low between-subject variations in the intensity of exercise achieved. In respect to obesity-related health outcome measures, CT was evidenced to provide a wealth of beneficial adaptations to a wide range of cardiometabolic health factors, with body composition changes the primary outcome sought by individuals engaging in exercise interventions. Therefore, we aimed to; 1) synthesise the current evidence-base on the utility and effect of CT as an exercise mode for individuals with obesity, particularly including the use of HIIT and the common methodologies employed; 2) determine the efficacy, reliability and feasibility of using individualised HIIT designs, for more accurate prescription of HIIT for individuals with obesity; 3) establish the feasibility and evaluate the intervention fidelity of completing combined HIIT and RT exercise training programmes in overweight and obese persons; and 4) determine the use and effectiveness of CT compared to HIIT on improving cardiometabolic outcomes in individuals with obesity. A systematic review and meta-analysis of CT programmes in overweight and obesity alongside a test-retest reliability study for a HIIT protocol and an 8-week exercise training feasibility study were undertaken. Meta-analysis revealed that CT could improve body composition, though the true effect of reductions in body mass (MD -1.7kg, 95% CI: -3.6, 0.1) were unclear. CT was effective in improving components of cardiometabolic health, but little research examined the effect of including HIIT. We show that a 10 x 60 second HIIT protocol dosed at an intensity of 80% delta was both repeatable and reliable, with typical error of internal load (VO2 2.2%, HR 2.8%) considerably lower than RPE (9.1%). We also demonstrate 8-week CT and HIIT exercise training programmes with good intervention fidelity and low between-subject variations in heart rate (0.03 & 0.02 beats.min-1). The 8-week CT programme incorporating HIIT was feasible, enjoyable and well-adhered to with low rates of adverse events in overweight and obese males. Moreover, CT caused greater reductions in body mass (MD: 2.0kg 95% CI: -0.7, 4.6) than HIIT-only, alongside greater improvements in LV EDV (MD 21.55ml 95% CI: 8.72, 34.38) and other factors including strength. However, the observed changes are unclear, with a small sample size and wide confidence intervals demonstrating uncertainty in the true effect and whether this is a meaningful change. This work requires further investigation, though, it is clear that focus should be given to cardiometabolic health more generally, rather than a sole emphasis on weight loss from exercise interventions.