The effects of chronic and acute physical activity on working memory performance in healthy participants: a systematic review with meta-analysis of randomized controlled trials

BACKGROUND Understanding how physical activity (PA) influences cognitive function in populations with cognitive impairments, such as dementia, is an increasingly studied topic yielding numerous published systematic reviews. In contrast, however, there appears to be less interest in examining associations between PA and cognition in cognitively healthy individuals. Therefore, the objective of this review was to evaluate and synthesize randomized controlled trial (RCT) studies that investigated the effects of both chronic and acute PA on working memory performance (WMP) in physically and cognitively healthy individuals. METHODS Following the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines, a systematic review of studies published between August 2009 and December 2016 was performed on RCTs investigating the effects of chronic and acute PA on WMP with healthy participants as the sample populations. Searches were conducted in Annual Reviews, ProQuest, PsycARTICLES, PsycINFO, PubMed, and Web of Science. Main inclusion criteria stipulated (1) healthy sample populations, (2) PA interventions, (3) WMP as an outcome, and (4) RCT designs. Descriptive statistics included cohort and intervention characteristics and a risk of bias assessment. Analytical statistics included meta-analyses and moderation analyses. RESULTS From 7345 non-duplicates, 15 studies (eight chronic PA and seven acute PA studies) met the inclusion criteria and were evaluated. Overall, there was noticeable variance between both cohort and intervention characteristics. Sample populations ranged from primary school children to retirement community members with PA ranging from cycling to yoga. The majority of studies were characterized by "low" or "unclear" risk of selection, performance, detection, attrition, reporting, or other biases. Meta-analysis of chronic PA revealed a significant, small effect size while analysis of acute PA revealed a non-significant, trivial result. Age and intensity were significant moderators while allocation concealment, blinding, and intervention length were not. CONCLUSIONS Chronic PA can significantly improve WMP while acute PA cannot. The limiting factors for acute PA studies point to the diversity of working memory instruments utilized, unequal sample sizes between studies, and the sample age groups. Large-scale, high-quality RCTs are needed in order to provide generalizable and more powerful analysis between PA and WMP in a systematic approach.