Fitness, function, activity and screen time – can benefits from a 12 week exercise program be maintained? The RESIST study (#71)
Adolescent obesity is associated with poor fitness and decreased capacity to perform functional tasks. This study examined the effect of a structured exercise program as part of a lifestyle intervention on fitness, physical function, physical activity and screen time.
Participants were obese 10-17 year olds, with insulin resistance participating in a 12 month RCT, known as RESIST. The primary aim of RESIST was to determine the optimal dietary macronutrient content to improve insulin sensitivity. As part of RESIST, 99 adolescents participated in two supervised exercise sessions per week for 12 weeks. Fitness (peak oxygen uptake) and physical function (exercise time and anaerobic threshold) were measured by gas analysis during the Bruce treadmill protocol at baseline, post intervention and at follow up 6 months after completion of the exercise intervention. Physical activity and screen time were measured by a validated questionnaire (CLASS) and body composition by dual energy x-ray absorptiometry.
At baseline peak oxygen uptake (VO2max) was low (estimated marginal mean±SEM = 23.8±0.5mL/kg/min), as was exercise time and anaerobic threshold, however, all improved post intervention by 5.8% [95%CI: 0.8 to 11.3], 8.5% [95%CI: 3.8 to 13.3] and 19.7% [95%CI: 10.4 to 29.0], respectively. These improvements were maintained at follow up. Compared to baseline, post intervention physical activity levels increased by 21 minutes/day [95%CI: 7 to 35] and screen time decreased by 48 minutes/day [95%CI: 17 to 78] but had returned to baseline levels by follow up. Decreased percentage body fat was associated with increased peak oxygen uptake (r=-0.24, P=0.032) and increased exercise time (r=-0.30, P=0.008).
A structured exercise program can lead to sustainable improved aerobic fitness, including improved exercise tolerance, facilitating functional task performance. However, fitness levels were still low, warranting further investigation into optimal exercise interventions and strategies to improve physical activity and screen time long-term.