No clear influence of menstrual cycle phase or hormonal contraceptive use on heat acclimation adaptations: A systematic review and meta-analysis

Studies were categorized by menstrual cycle phase (follicular and luteal), hormonal status (naturally menstruating and hormonal contraceptive users), reporting type (pooled or separate phases), and HA protocol type (isothermal or fixed work rate). Seven studies were included. Most assessed HA within a single menstrual phase; therefore, findings primarily represent between-subject responses rather than direct comparisons of hormonal effects.

No consistent differences were observed between menstrual cycle phases or hormonal contraceptive users. HA protocol type influenced only the exercising heart rate, with fixed-work-rate protocols producing greater reductions than isothermal protocols. Current evidence does not demonstrate a clear influence of menstrual cycle phase or hormonal contraceptive use on physiological adaptations to HA.

Adaptations appear to be more strongly influenced by HA protocol characteristics. However, conclusions remain limited by small sample sizes, inconsistent menstrual cycle verification, and the predominance of between-subject study designs, highlighting the need for well-controlled longitudinal research in females.</p> <p></p><p>Physiological responses to HA appear to be consistent across protocols as well as menstrual cycle and hormonal contraceptive phases.</p><p>Heat acclimation protocol may influence physiological adaptations more than hormonal status.</p><p>Evidence for menstrual cycle–related effects on HA remains inconclusive, mainly due to methodological limitations, including inaccurate menstrual cycle phase classification, a lack of hormonal verification, and limited use of within-subject designs, which highlight the need for more rigorously controlled studies.</p><p></p> <p>Physiological responses to HA appear to be consistent across protocols as well as menstrual cycle and hormonal contraceptive phases.</p> <p>Heat acclimation protocol may influence physiological adaptations more than hormonal status.</p> <p>Evidence for menstrual cycle–related effects on HA remains inconclusive, mainly due to methodological limitations, including inaccurate menstrual cycle phase classification, a lack of hormonal verification, and limited use of within-subject designs, which highlight the need for more rigorously controlled studies.</p>