Gender and academic year as moderators of the efficacy of mobile app interventions to promote physical activity in adolescents: a randomized controlled trial

No previous study has analyzed differences in the effectiveness of mobile app–based interventions according to gender and academic year on adolescents’ physical activity, body composition, and fitness. This randomized controlled trial examined changes in physical activity, kinanthropometric and derived variables, and fitness after a 10-week, school-promoted mobile app intervention. Four hundred adolescents (210 males, 190 females; mean age 13.96 ± 1.21 years) were randomized by class to experimental (n=240) or control (n=160) groups. The experimental group used one of four apps (Strava, Pacer, MapMyWalk, Pokémon Go) at least three times weekly, with step targets increasing from 7000/day (week 1) to 12,500/day (week 10); controls continued usual activities. App use was higher in females (71.1%) than males (50.0%; p<0.001) and in higher academic years (e.g., 74.4% in 4th vs 53.8% in 1st; p<0.001). App use prevented increases in fat-related variables (BMI, fat mass, sum of 3 skinfolds, waist and hip girths). Moderation analyses showed significant gender effects for BMI, corrected calf girth, fat mass, handgrip (right/left), and countermovement jump; and academic-year effects for height, sum of 3 skinfolds, waist and hip girths, corrected calf girth, and fat mass. Mobile apps appear to be a valuable alternative to promote physical activity, reduce fat-related variables, and improve selected fitness outcomes, especially in females and adolescents in higher academic years. Trial registration: ClinicalTrials.gov NCT04860128.