Comparison of a Proposed Strength Training Program Using Indirect 1RM Versus Mobile Application Recommendations for Body Fat Loss: A Quasi-Experimental Study

Obesity represents a major public health crisis in Mexico, affecting over 70% of adults, and although strength training is effective for improving body composition, direct maximal strength testing (1RM) poses risks in this population. Mobile applications have emerged as popular tools for exercise prescription, yet their effectiveness compared to supervised, scientifically-based protocols remains unknown. To compare the effects of a supervised strength training program based on indirect 1RM estimation (S1RM group) versus a mobile application-generated program (App group) on body composition, anthropometric measures, and strength gains in male adults with obesity. Twenty male participants (BMI ≥ 30 kg/m2) were randomly assigned to either the S1RM group or the App group. Both groups trained three times per week for 12 weeks. Body composition (bioelectrical impedance), anthropometric measures (waist and hip circumference), and estimated 1RM were assessed pre- and post-intervention. A mixed repeated-measures ANOVA (Group × Time) was conducted, with effect sizes (η2p) and 95% confidence intervals calculated. Both groups showed significant improvements in most outcomes (p < 0.05). However, significant group × time interactions favored the S1RM group for waist circumference (F(1,18) = 14.50, p = 0.001, η2p = 0.45) and hip circumference (F(1,18) = 217.90, p < 0.001, η2p = 0.92). A significant between-group difference was also observed for visceral fat (F(1,18) = 4.91, p = 0.040, η2p = 0.21). For muscle and fat mass, interactions showed large effect sizes (η2p = 0.18–0.19) with trends toward significance (p = 0.057–0.096). Strength increased significantly in all exercises for the S1RM group (14.9–22.0%, p < 0.01). These findings support the implementation of indirect 1RM estimation methods in obesity populations and highlight the added value of professional supervision in strength training programs.