App-supported resistance training linked to lean mass and bone gains in youth with type 1 diabetes

BACKGROUND: Compared to their healthy peers, children and adolescents with type 1 diabetes are at an increased risk of adverse changes in body composition, including increased fat mass along with reductions in lean and bone mass. Although exercise has shown promise in improving body mass index in this population, the individual effects of resistance training on specific body composition parameters remain understudied. The aim of the study was to evaluate the effects of resistance training supported by the mHealth application Diactive-1 on body composition in children and adolescents with type 1 diabetes. METHODS: Sixty-two participants with type 1 diabetes (aged 8-18 years old; 48% females) participated in a 24-week randomised controlled trial and were assigned to either the usual care group (n = 32) or the exercise group (n = 30). The intervention was delivered via the Diactive-1 app, which generates progressive overload resistance training programmes tailored to real-time glycaemia and provides educational support. Body composition was assessed using anthropometry and dual-energy X-ray absorptiometry, with fat, lean and bone measurements standardised by age, sex and ethnicity. Linear mixed models were used to evaluate between-group differences in change over time under both intention-to-treat (ITT) and per-protocol (PP) approaches. RESULTS: At 24 weeks, in the ITT analysis, the intervention group showed greater gains in lean mass (mean difference [MD] = 0.88 kg; 95% confidence interval [CI] 0.09 to 1.66; Hedges' g = 0.568) and whole-body bone mineral content less head (MD = 32.40 g; 95% CI 6.90 to 57.89; g = 0.644) compared with those in the usual care group. No changes were observed in anthropometric measures, fat mass-related regions or standardised variables (p > 0.05). The risk of probable sarcopenia was lower in the intervention group (relative risk [RR] = 0.17; 95% CI 0.04 to 0.73; Cohen's h = 0.987) than in the usual care group. Findings were directionally consistent in the PP analysis. CONCLUSIONS: This intervention increased bone-related outcomes and was associated with modest gains in lean mass and a lower risk of probable sarcopenia in youths with type 1 diabetes. These findings highlight the potential of the Diactive-1 app as an adjunct tool to support musculoskeletal health in youths with type 1 diabetes. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06048757.