Unraveling the miscellaneous physical and psychological effects of unstructured physical activity interventions on adults: A systematic review and meta-analysis of the current evidence.

BACKGROUND: Physical inactivity is a leading cause of mortality worldwide. Unstructured physical activity refers to bodily movements performed spontaneously or habitually while embedded in daily life contexts and has emerged as a potential strategy to promote sustainable exercise habits. The evidence suggests that unstructured physical activity may affect adults' physical and psychological outcomes, although the directions of these effects remain unclear.

OBJECTIVE: To synthesize the effects of unstructured physical activity interventions on adults' physical and psychological outcomes.

METHOD: For this systematic review and meta-analysis, nine databases (PubMed, Embase, Web of Science, Cochrane Library, CINAHL, PsycINFO, China National Knowledge Infrastructure, WanFang, China Science and Technology Journal Database) were searched up to February 2026 for randomized controlled trials evaluating the effects of interventions on physical (activity, function, body composition, sleep) and psychological (self-efficacy, anxiety, depression, happiness, stress, fatigue) outcomes in adults. The risk of bias was assessed using the Cochrane Risk of Bias Tool 2, and evidence quality was assessed by the Grading of Recommendations, Assessment, Development, and Evaluation method. Pooled effects were analyzed using fixed- or random-effects models in Review Manager. Narrative syntheses were adopted when a meta-analysis was inappropriate.

RESULTS: Studies (n = 38) involving 8551 adults that investigated the lifestyle-integrated functional exercise, zero-time exercise, walking, and standing categories were included. The results of the meta-analysis indicated that the interventions significantly improved moderate-to-vigorous physical activity, vigorous physical activity, sedentary time, step counts, step time, systolic blood pressure, self-efficacy, and depression. Narrative analyses suggested that the interventions improved light physical activity, sedentary time, muscle strength, balance, and fatigue but did not significantly affect blood pressure, weight, waist circumference, sleep, or self-efficacy. The effects of moderate physical activity and moderate-to-vigorous physical activity were inconsistent. Sensitivity analyses suggested limited robustness for improving light physical activity, grip strength, balance, and body mass index. Subgroup analyses were unable to substantially reduce the heterogeneity of several outcomes (e.g., moderate-to-vigorous physical activity, sedentary time, step counts, standing time, lower limb muscle strength, weight, self-efficacy, anxiety, depression). No severe adverse events were reported.

CONCLUSIONS: Unstructured physical activity interventions provide a convenient approach to improve adults' physical activity and psychological outcomes. However, the observed effects varied across outcomes, and substantial heterogeneity remained in several analyses; therefore, the findings should be interpreted with caution. In addition, the included studies involved diverse populations, and future research should further examine the effectiveness of such interventions in specific populations and explore their long-term effects.