Optimising exercise time-of-day for cardiometabolic health: Insights from a systematic review and meta-analysis in varied adult cohorts

We systematically investigate whether the time-of-day influences physiological responses to exercise. PubMed, CENTRAL and Web of Science were searched until June 2023. Studies must have been clinical trials with human participants classed as healthy, 'overweight' or obese, with type 2 diabetes mellitus (T2DM) or with treated/pre-hypertension. Single exercise bouts (acute: T-1; T-2) and training programmes (chronic: T-3) performed in the morning (AmEx) and in the afternoon/evening (PmEx) were included. Data were extracted for <i>V</i>.O2max/peak, vascular glucose and blood pressure (BP). 625 participants were included. PmEx resulted in significantly lower blood pressure vs. AmEx in the following analyses: mean arterial blood pressure (MABP) at T-1 (Standard Mean Differences (SMD) = 0.50; 95% CI : 0.12, 0.88) and T-2 (SMD = 0.35; 95% CI : 0.06, 0.65); systolic BP at T-2 (SMD = 0.32; 95% CI : 0.05, 0.58; n = 9 studies) and T-3 (SMD = 0.32; 95% CI: 0.02, 0.62) and diastolic BP at T-2 (SMD = 0.34; 95% CI : 0.05, 0.63). Similarly, blood glucose levels were lower for PmEx in participants with T2DM and/or overweight and obesity at T-3 (SMD = 0.45; 95% CI: 0.06, 0.83). PmEx elicits significant reductions in multiple analyses vs. AmEx.