Interactions of cortisol, testosterone, and resistance training: influence of circadian rhythms.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing literature without systematic methodology
PubMed 20560706 · doi:10.3109/07420521003778773
What was done
This narrative review synthesizes literature examining how circadian rhythms, core body temperature, and diurnal fluctuations in testosterone and cortisol influence acute resistance exercise performance and long-term training adaptations.
What was found
The abstract provides no quantitative metrics or effect sizes. It describes that sports performance across energy systems and contraction types typically peaks in the late afternoon alongside elevated core temperature. Although baseline resting testosterone and cortisol are highest in the morning, resistance exercise elicits a larger relative testosterone increase in the late afternoon. Adaptations in strength and hypertrophy are reported to favor late-afternoon training, although regular morning training can attenuate time-of-day performance deficits.
Why it matters
It clarifies that basal morning hormone peaks do not necessarily dictate optimal training times, pointing instead to late-afternoon neuromuscular readiness and exercise-induced hormonal responsiveness for resistance adaptations.
Limits
The review presents a narrative synthesis rather than a systematic meta-analysis, omitting search criteria, sample sizes, and quantitative effect sizes. It does not account for confounders such as sleep quality, nutritional timing, or chronotype variations across different athletic populations.
Cited by
- supports Data show that 3 hours after waking and 11 hours after waking are optimal times for mental and physical performance due to body temperature and cortisol rhythms.