The effects of resistance exercise snacks via a mobile health app on musculoskeletal strength in sedentary young women: a randomized controlled trial

OBJECTIVE: This study aims to evaluate the effects of an eight-week Exercise Snacks (ES) program based on a mobile app on musculoskeletal strength in sedentary young women. METHODS: Sixty sedentary young women were randomly assigned to the ES group (n=30) or the control group (n=30). Participants in the ES group completed an eight-week exercise program with 75 minutes per week. Outcome measures before and after intervention included maximal strength (peak torque, maximal force output), explosive strength (standing long jump), and muscular endurance (total work at 180°/s, bodyweight squats to failure). We used two-way repeated measures analysis of variance (ANOVA) (time × group) with Bonferroni post hoc tests, and effect sizes were reported as partial eta squared ( η p 2 ). p < 0.05 was statistically significant. RESULTS: Significant group × time interactions were observed for all outcomes (p < 0.05). In the ES group, peak torque at 60°/s increased from 115.68 ± 33.92 N·m to 128.40 ± 36.88 N·m, while the control group showed a change from 116.76 ± 30.32 N·m to 118.85 ± 30.20 N·m (p = 0.011, η p 2 = 0.107). Maximal force output in the ES group increased from 568.07 ± 43.45 N to 579.61 ± 46.35 N, compared to the control group, which decreased from 558.98 ± 44.26 N to 557.46 ± 45.16 N (p = 0.026, η p 2 = 0.083). The standing long jump improved from 165.20 ± 10.45 cm to 172.17 ± 10.72 cm in the ES group, whereas the control group improved from 167.27 ± 9.98 cm to 168.43 ± 9.74 cm (p < 0.001, η p 2 = 0.258). Total work at 180°/s in the ES group increased from 722.82 ± 109.39 J to 812.85 ± 128.35 J, while the control group showed an increase from 738.86 ± 81.02 J to 760.73 ± 79.80 J (p < 0.001, η p 2 = 0.285). Lastly, the number of bodyweight squat repetitions increased from 27.87 ± 9.66 to 32.53 ± 10.88 in the ES group, compared to the control group, which increased from 25.67 ± 7.22 to 27.73 ± 7.90 (p = 0.019, η p 2 = 0.091). CONCLUSIONS: 75 minutes of resistance exercise snacks per week is an effective strategy for promoting musculoskeletal strength in sedentary women. Further studies should explore the underlying physiological mechanisms.