Comparative effect size distributions in strength and conditioning and implications for future research: a meta-analysis.

Swinton, Paul Alan; Murphy, Andrew

Abstract

Controlled experimental designs are frequently used in strength and conditioning (S&C) to determine which interventions are most effective. The purpose of this large meta-analysis was to quantify the distribution of comparative effect sizes in S&C to determine likely magnitudes and inform future research regarding sample sizes and inference methods. Baseline and follow-up data were extracted from a large database of studies comparing at least two active S&C interventions. Pairwise comparative standardised mean difference effect sizes were calculated and categorised according to the outcome domain measured. Hierarchical Bayesian meta-analyses and meta-regressions were used to model overall comparative effect size distributions and correlations, respectively. The direction of comparative effect sizes within a study were assigned arbitrarily (e.g. A vs. B, or B vs. A), with bootstrapping performed to ensure effect size distributions were symmetric and centred on zero. The middle 25, 50, and 75% of distributions were used to define small, medium, and large thresholds, respectively. A total of 3874 pairwise effect sizes were obtained from 417 studies comprising 958 active interventions. Threshold values were estimated as: small = 0.14 [95%CrI: 0.12 to 0.15]; medium: = 0.29 [95%CrI: 0.28 to 0.30]; and large = 0.51 [95%CrI: 0.50 to 0.53]. No differences were identified in the threshold values across different outcome domains. Correlations ranged widely (0.06 ≤ r ≤0.36), but were larger when outcomes within the same outcome domain were considered. The finding that comparative effect sizes in S&C are typically below 0.30 and can be moderately correlated has important implications for future research. Sample sizes should be substantively increased to appropriately power controlled trials with pre-post intervention data. Alpha adjustment approaches used to control for multiple testing should account for correlations between outcomes and not assume independence.

Citation

SWINTON, P.A. and MURPHY, A. [2024]. Comparative effect size distributions in strength and conditioning and implications for future research: a meta-analysis. International journal of strength and conditioning [online], (accepted). To be made available from: https://journal.iusca.org/index.php/Journal/issue/view/9

• Journal Article Type: Article
• Acceptance Date: Jan 19, 2024
• Deposit Date: Jan 25, 2024
• Publicly Available Date: Jan 25, 2024
• Journal: International journal of strength and conditioning
• Print ISSN: 2634-2235
• Electronic ISSN: 2634-2235
• Publisher: International Universities Strength and Conditioning Association (IUSCA)
• Peer Reviewed: Peer Reviewed
• Keywords: S&C; Evaluation; Effect size; Statistical power; Sample size
• Public URL: https://rgu-repository.worktribe.com/output/2218514
• Related Public URLs: https://rgu-repository.worktribe.com/output/1764885 (Pre-print published on SportRixiv)