The myth of contextual interference learning benefit in sports practice: A systematic review and meta-analysis

The contextual interference (CI) model hypothesizes random practice (high CI) leads to inferior acquisition, but superior retention and transfer capabilities compared to blocked practice (low CI). These phenomena are well established in laboratory settings. However, the transfer to applied settings, particularly in sports practice is still under discussion. The aim of this systematic review and meta-analysis is to evaluate the possible generalisability of the CI phenomenon in sports-based contexts with regard to performance outcomes. Up to April 16th, 2022, five electronic databases (PubMed, Web of Science, Scopus, Taylor & Francis, and SciELO) were used to search for relevant studies investigating differences between blocked and random schedules at post-acquisition, retention, and/or transfer tests. Using the PICOS criteria, a total of 933 records were screened. Outcomes evaluating the acquisition, retention, and/or transfer performances in sports skills in healthy participants were included. The quality of the selected studies was scored using the PEDro scale. Thirty-seven studies were selected, of which twenty-seven were of good quality and the remaining ten were rated as fair quality. Out of 205 overall pooled outcomes, only 43 performance outcomes (21%) agreed with the CI phenomenon after the acquisition (18 out of 103), retention (19 out of 84), and/or transfer (6 out of 36) phases. No statistically significant overall difference between blocked and random practice was detected at post-acquisition (effect size (ES) = 0.1, p = 0.154), retention (ES = −0.159, p = 0.141) or transfer testing (ES = −0.243, p = 0.071). The subgroup analysis showed inferior acquisition and superior retention following random practice only in individuals aged 20–24 years (ES = 0.282, p = 0.030 during the acquisition, and ES = −0.405, p = 0.011 during retention), with no difference at transfer testing for this specific age group. No similar significant effects have been concurrently identified during both acquisition and retention phases in any of the remaining subgroups (e.g., examined based on experience level, sports, skills, and testing protocol categories). The present results suggest CI effects can only be confirmed under very limited conditions, which seriously challenges the extension of CI effects to the sport context in general. Problematic conclusions for children's learning are discussed, as well as future research strategies to better understand counterintuitive learning approaches.