Effects of exercise timing and intensity on physiological circadian rhythm and sleep quality: a systematic review.
Level 1 - systematic review of randomized trials
Systematic review of interventional trials
PubMed 37946447 · doi:10.20463/pan.2023.0029
What was done
A PRISMA-compliant systematic review was conducted across PubMed, ScienceDirect, Web of Science, and Embase. Included studies evaluated adult humans undergoing exercise interventions of varying timing or intensity compared to non-exercise controls or baseline. Eligible outcomes were physiological circadian rhythm markers (cortisol, melatonin, or core body temperature) alongside subjective or objective sleep quality measurements.
What was found
Nine articles comprising 201 participants (77.1% male) were identified. Acute evening exercise delayed melatonin rhythm and elevated nocturnal core body temperature without negatively impacting non-rapid eye movement sleep or sleep efficiency. Core body temperature returned to baseline within 30–120 minutes following prolonged exercise. No differences in sleep quality were found between acute high-intensity and moderate-intensity exercise. Long-term morning exercise tended to lower post-awakening cortisol concentrations and improve sleep quality. The abstract reported qualitative trends with no numerical effect sizes or confidence intervals.
Why it matters
This review suggests that acute evening or high-intensity exercise modifies circadian biomarkers like melatonin and core temperature without meaningfully worsening sleep efficiency, challenging generic guidance against evening physical activity.
Limits
The total sample size is very small (9 studies, 201 participants) and predominantly male (77.1%). The abstract reports findings narratively without quantitative meta-analytic pooling or exact effect estimates, and long-term exercise timing protocols remain sparsely studied.
Cited by
- context Intense exercise in the late afternoon or evening can triple or quadruple baseline cortisol levels for several hours.