Journal of Trainology



April 2020; Vol. 9, No. 1: Pages 20-32

Does increasing an athletes' strength improve sports performance? A critical review with suggestions to help answer this, and other, causal questions in sport science

James Steele, James Fisher, Derek Crawford


Objectives: Researchers and practitioners in sports science aim to generate, and apply, knowledge to improve sports performance. One area of interest is the role that muscular strength, and thus approaches to improve this (i.e. resistance training), has upon sports performance. In this review we briefly consider the evidence regarding an answer to the causal question "Does increasing an athletes' strength improve sports performance?". Design & Methods: We first consider the Applied Research Model for the Sport Sciences (ARMSS) to frame the problem and answer this. We then highlight barriers to answering it (and other causal questions) before offering suggestions to address these. Results: Muscular strength typically differentiates elite and non-elite athletes, and is correlated with proxy measures of sports performance. However, there is insufficient evidence to make a definitive statement regarding the causal effect of muscular strength upon sports performance. Conclusions: Considering the ARMSS, evidence is lacking whether improving muscular strength is causally related to sports performance. Present evidence is primarily observational and cross-sectional, experimental evidence is limited and focused upon proxy measures of sports performance, primarily conducted in small samples, and with little consideration regarding meaningfulness of effects. Suggestions to help improve research in this area and better answer this question include: larger sample sizes, determination of smallest effect sizes of interest for outcomes including muscular strength and proxy measures of sports performance (using both anchoring and/or expert opinion), and use of causal inference methods for observational data (actual sports performance, performance indicators, and fitness measures) including graphical causal diagrams and mediation analysis.

Received February 8, 2020; accepted April 28, 2020