The effects of resistance exercise on insulin sensitivity in adolescents

Abstract

Background: An escalating incidence of type 2 diabetes among adolescents is causing concern. This is thought to be sparked by rising population-wide prevalence of insulin resistance. Resistance exercise has been shown to reduce insulin resistance, however only immediate, post-intervention effects have been demonstrated. The use of resistance exercise by adolescents in managing insulin resistance in the long-term has not been evaluated. Purpose: To assess the effects, up to six months, of a physiotherapist-supervised, resistance exercise program on insulin sensitivity, cardiorespiratory fitness, muscle strength, physical activity levels, and anthropometric measures among adolescents with insulin resistance. Methods: Participants with insulin resistance were recruited from a database of patients from a pediatric chronic disease prevention program. They completed a supervised 10-week resistance exercise program, 60-minutes, three times per week. A body positive approach was used focusing on health behaviours. Using a repeated-measures design, participants were assessed during an observational run-in control period then at pre, post, and 6-month follow-up assessments. The primary outcome was insulin sensitivity, measured by the oral glucose tolerance test. Secondary outcomes included cardiorespiratory fitness, muscle strength, physical activity level, and anthropometric measures. Results: Thirteen participants (14.16±1.19 years old; 8 males, 5 females) completed the intervention. Improvements in insulin sensitivity were found, observed as reduced fasting insulin [F(₂,₂₂)=7.54,p=0.003,ηp²=0.41], fasting glucose [F(₂,₂₂)=3.58,p=0.045,ηp²=0.25], and HOMA-IR [F(₂,₂₂)=7.60,p=0.003,ηp²=0.41], which were maintained at follow-up. Cardiorespiratory fitness, waist circumference, and waist-to-hip ratio also significantly improved at post and follow-up. Daily physical activity levels improved but not significantly. Upper and lower body muscle strength significantly increased post-intervention but returned to pre-assessment values at follow-up. Conclusion: The findings suggest that a supervised 10-week resistance exercise program (60-minute, three times per week) improves insulin sensitivity, cardiorespiratory fitness, waist circumference, and waist-to-hip ratio in adolescents who are at high risk of developing type 2 diabetes. Importantly, these benefits are maintained up to six months. Supervised, resistance exercise adds significant long-term benefit in the management of insulin resistance in adolescents.