THE INFLUENCE OF RESISTANCE TRAINING VARIABLES ON MUSCLE STRENGTH: A SYSTEMATIC REVIEW AND META-ANALYSIS

Abstract

BACKGROUND Development of muscle strength through resistance training (RT) is associated with health and performance benefits. Prescribing resistance training utilising six different variables (sets × repetitions × exercises × intensity × frequency × duration) is complex to optimise outcomes. It is unclear if, the prescription of these variables to derive a composite variable, RT dosage, influences the development of muscle strength. OBJECTIVES: This study aimed to investigate if variations in RT dosage influence muscle strength. METHODS CINAHL, MEDLINE, and SPORTDiscus were systematically searched; adults performing RT were compared against non-exercise controls where muscle strength was assessed. Only randomised controlled trials assessing chest and quadriceps muscle strength were considered. The six RT variables were extracted from eligible studies and were multiplied to generate RT dosage. Quadratic non-linear regressions were performed on pooled muscle strength data. Variable importance and model selection were performed to explore different linear combinations of RT variables to determine the most effective variable in developing muscle strength. RESULTS 207 articles were eligible that enabled the calculation of RT dosage. Meta-analyses confirmed a significant effect of RT on muscle strength (SMD ≥ 1.3, CI = 1.1-1.6, p < 0.001). Quadratic non-linear regression models for the chest and quadriceps strength indicated that RT dosage as a continuous variable showed a significant dose-response for muscle strength (SMD = > 1.5, CI = 0.01-3.1, P < 0.05). The individual variables of most importance to develop muscle strength appear to be volume and duration (p < 0.03). CONCLUSIONS As expected, RT significantly influences muscle strength and as RT dosage increases, so too does muscle strength; however, only up to a point (∼1.5 million arbitrary units) before further increases in RT dosage don’t appear to further develop muscle strength. Prescription of RT volume and duration should be prioritised for developing muscle strength.