Skip to main content

Research Repository

Advanced Search

Interpreting magnitude of change in strength and conditioning: effect size selection, threshold values and Bayesian updating.

Swinton, Paul Alan; Burgess, Katherine; Hall, Andy; Greig, Leon; Psyllas, John; Aspe, Rodrigo; Maughan, Patrick; Murphy, Andrew


Rodrigo Aspe

Patrick Maughan


The magnitude of change following strength and conditioning (S&C) training can be evaluated comparing effect sizes to threshold values. This study conducted a series of meta-analyses and compiled results to identify thresholds specific to S&C, and create prior distributions for Bayesian updating. Pre- and post-training data from S&C interventions were translated into standardised mean difference (SMDpre) and percentage improvement (%Improve) effect sizes. Four-level Bayesian hierarchical meta-analysis models were conducted to compare effect sizes, develop prior distributions, and estimate 0.25-, 0.5-, and 0.75-quantiles to determine small, medium, and large thresholds respectively. Data from 643 studies comprising 6574 effect sizes were included in the analyses. Large differences in distributions for both SMDpre and %Improve were identified across outcome domains (strength, power, jump and sprint performance), with analyses of the tails of the distributions indicating potential large overestimations of SMDpre values. Future evaluations of S&C training will be improved using Bayesian approaches featuring the information and priors developed in this study. To facilitate an uptake of Bayesian methods within S&C, an easily accessible tool employing intuitive Bayesian updating was created. It is recommended that the tool and specific thresholds be used instead of isolated effect size calculations and Cohen's generic values when evaluating S&C training.


SWINTON, P.A., BURGESS, K., HALL, A., GREIG, L., PSYLLAS, J., ASPE, R., MAUGHAN, P. and MURPHY, A. 2022. Interpreting magnitude of change in strength and conditioning: effect size selection, threshold values and Bayesian updating. Journal of sports sciences [online], 40(18), pages 2047-2054. Available from:

Journal Article Type Review
Acceptance Date Sep 21, 2022
Online Publication Date Oct 2, 2022
Publication Date Dec 31, 2022
Deposit Date Sep 23, 2022
Publicly Available Date Sep 23, 2022
Journal Journal of sports sciences
Print ISSN 0264-0414
Electronic ISSN 1466-447X
Publisher Taylor and Francis
Peer Reviewed Peer Reviewed
Volume 40
Issue 18
Pages 2047-2054
Keywords Athletic performance; Muscular strength training; Effect size; Power; Prior; Strength and conditioning (S&C)
Public URL
Related Public URLs (Supplementary Data)