The effects of evening high-intensity exercise on sleep in healthy adults: A systematic review and meta-analysis

Moderate-intensity exercise is generally recommended for improving sleep, whereas, high-intensity exercise (HIE) prior to bedtime is often discouraged. We conducted a systematic review and meta-analysis to determine if acute or regular (chronic) HIE performed before bedtime disrupts nighttime sleep of healthy adult, good sleepers compared with a no-exercise control. Six databases (PubMed, EMBASE, Scopus, Web of Science, CENTRAL, and PsycINFO) were searched from inception to 31st May, 2021. Studies were experimental trials published in English language, objectively (polysomnography, actigraphy) and/or subjectively assessed sleep after evening HIE in sedentary and physically fit, good sleepers (aged 18-50 y old). The revised Cochrane risk of bias tool for randomized trials was used to assess risk of bias in the included studies. The random-effects model was used for the meta-analyses. We included 15 acute evening HIE studies in the meta-analysis with a total of 194 participants. Acute evening HIE ending 0.5-4 h before bedtime decreased rapid eye movement sleep (-2.34%; p = 0.002) compared with a no-exercise control. No other significant sleep changes occurred. A regular evening HIE did not disrupt nighttime sleep. Overall, acute evening HIE performed 2-4 h before bedtime does not disrupt nighttime sleep of healthy, young and middle-aged adults. PROSPERO, protocol registration number: CRD42020218299.