Current Issues in Randomization in Sports Science Research: Limitations, Misconceptions, and Alternatives: Narrative Review

Abstract

Abstract Randomization is a central methodological component of experimental research because it supports causal inference, reduces selection bias, and improves the comparability of intervention groups. However, its implementation in sports science presents distinct methodological, ethical, and logistical challenges, including small and highly specialized samples, limited access to elite athletes, competition schedules, training constraints, intervention adherence, and difficulties in controlling contextual factors such as nutrition, recovery, and physical activity outside the study protocol. This narrative review examines the practical and methodological challenges associated with randomization in sports science and highlights common sources of bias, including inadequate allocation procedures, pseudo-randomization, poor adherence, and incomplete reporting. Random allocation procedures such as simple, block, stratified, and response-adaptive randomization remain valuable when appropriately aligned with the research question and study context, while randomized trial designs may include parallel-group, clusterrandomized, crossover, and stepped-wedge cluster-randomized structures. When conventional randomized trials are difficult to implement, quasi-experimental designs may provide alternative causal-inference strategies, whereas pragmatic trial frameworks and Bayesian inferential methods may be incorporated within randomized or nonrandomized studies. Mendelian randomization, by contrast, is a distinct observational causal-inference method that uses genetic variants as instrumental variables and does not involve investigator-controlled allocation to experimental conditions. The review also considers digital tools such as randomizeR, RRApp, and OxMaR, which may support transparent allocation generation and reproducible reporting. Overall, this review emphasizes the need to balance methodological rigor with real-world feasibility in sport and exercise settings. By providing practical guidance on allocation strategies, studydesign selection, bias mitigation, causal interpretation, and transparent reporting, this work aims to support researchers in designing studies that are ethically sound, contextually appropriate, and scientifically robust.