The Multidimensional Impact of Exercise Timing on Health: A Systematic Review

This systematic review aims to determine whether exercise timing influences different health indicators. The search, conducted until May 2025 across PubMed, Web of Science, EBSCO, China National Knowledge Infrastructure, and Wanfang databases, reviewed 2,937 articles. This review included randomized controlled trials in English that explored exercise timing for various populations, excluding unspecified exercise timing, animal studies, and low-quality articles. A total of 43 studies with 3,543 participants were included. The risk of bias was assessed using the Cochrane Risk of Bias 2 tool, and study characteristics and results were tabulated. Current evidence suggests that exercise timing may differentially impact health dimensions: afternoon exercise may improve metabolism in metabolic disorders; postdinner exercise might enhance blood glucose control for type 2 diabetes; premeal exercise could reduce appetite for overweight and obese individuals; evening exercise may improve sleep quality for sleep disorders but may negatively affect early chronotypes; morning exercise may enhance athlete performance, while afternoon exercise may promote the recovery of ordinary individuals; and morning exercise should be approached cautiously in cardiovascular risk groups. However, contradictions in some dimensions highlight the need for further rigorous research to solidify implications for exercise prescriptions. The study protocol was prospectively registered on PROSPERO (ID: CRD42024595984).