Effects of a 20-Week School-Based Periodized Strength Training Program on Motor Performance in Children

Regular physical activity and supervised strength training are recognized components of healthy growth and motor development during childhood. Although linear and nonlinear periodized strength training are widely used approaches for organizing resistance training, limited information is available regarding their comparative application in school-aged children, particularly within school-based programs. This randomized controlled trial compares two periodized strength training models implemented over a 20-week intervention in schoolchildren to assess muscular power and speed/agility using standardized motor performance assessments.

Inclusion Criteria: * Schoolchildren enrolled in one of the participating educational institutions. * Approximately 12-13 years of age. * Willing to participate in the study. * Written informed consent provided by parents or legal guardians. * Availability to participate in all assessment sessions. Exclusion Criteria: * Medical history that prevented participation in sports practice (cardiovascular disease, neurological disease, or chronic respiratory disease). * Musculoskeletal injuries and/or bone malformations at the time of the study. * Recent injury before study participation. * Absence during pre-test or post-test assessments. * Failure to attend at least 80% of the intervention sessions (experimental groups). * Participation in systematic physical activity or organized sports outside the school setting. * Lack of written parental or legal guardian consent.