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, postintervention 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,ηp 2 =0.41], fasting glucose [F(2,22)=3.58,p=0.045,ηp 2 =0.25], and HOMA-IR [F(2,22)=7.60,p=0.003,ηp 2 =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 followup. Conclusion: The findings suggest that a supervised 10-week resistance exercise program (60minute, 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. A sincere thank-you to Dr. Michelle Ploughman for encouraging me to initiate this project and for her support as a motivator, editor, and colleague. A heartfelt thank-you to Dr. Tracey Bridger for listening to me day in and out with ideas and questions. Thank you to Dr. Laurie Twells for introducing me to the field of clinical epidemiology. My unconditional love pours out to my husband, Darrell, my son, Chase, and our everchanging family. Darrell, without your daily support this project would not have happen; you are my ro...