Strength Gains Across Performance Levels and Sexes: A Meta-Analytical Perspective

Background Strength adaptations decrease with increasing training status. However, the inconsistent classification of training status in sports science impairs the comparability and interpretation of findings. This meta-analysis therefore investigates the impact of performance level on strength adaptations, while also assessing the validity of a common training status classification. Methods A PRISMA-guided search (PubMed, Web of Science, and SPORTDiscus) identified studies involving ≥ 6 weeks or at least eight resistance training sessions in healthy adults aged 18–40 years, assessing strength in the back squat, bench press, or deadlift. Performance levels were classified according to established criteria. Random-effects models were used to estimate pooled mean differences, with subgroup analyses performed according to performance level and sex. Results A total of 128 studies, comprising 4357 participants, were included. Resistance training elicited significant strength gains across all performance levels (MD = 1.6 kg/wk; 95%CI: 1.5 to 1.8 kg/wk, p  ≤ 0.001). However, only beginners exhibited significant greater improvements compared to higher performance levels (p = 0.02), while no differences were detected between intermediate, advanced, and highly advanced individuals. Male participants showed greater absolute ( p  ≤ 0.001) and relative ( p  = 0.049) strength gains than females (p < 0.001). Conclusion This meta-analysis confirms that resistance training induces strength adaptations at all performance levels, with the most pronounced gains being experienced by beginners. Differences in strength gains among intermediate, advanced and highly advanced individuals, as classified by existing models, could not be demonstrated. This indicates insufficient validity of the current classification systems. Additionally, gaps in the literature, such as the underrepresentation of highly trained females and deadlift assessments, highlight the need for standardized, empirically validated classification criteria in resistance training research.