Heat Therapy During Reduced Physical Activity

Inclusion Criteria:

* Adults aged 18 years or older
* Healthy men and premenopausal women
* Able and willing to provide written informed consent
* Able to perform knee-extension cycling exercise
* Stable habitual physical activity for at least 3 months before enrollment
* Pass the American College of Sports Medicine (ACSM) Preparticipation Health Screening
* Not currently taking medications known to affect cardiovascular function (e.g., antihypertensive medications or beta-blockers)
* No regular sauna or hot-tub use (fewer than six exposures during the previous 2 months)
* Willing and able to comply with all study procedures, including temporary reduction of physical activity, daily sauna visits, physiological testing, and follow-up assessments

Exclusion Criteria:

* Younger than 18 years of age
* Failure to pass the ACSM Preparticipation Health Screening
* Unable or unwilling to perform exercise testing
* Current cigarette or marijuana use
* Pregnant or planning to become pregnant during the study
* History or current diagnosis of cardiovascular disease, metabolic disease, or cognitive impairment
* Use of medications known to influence cardiovascular function or exercise tolerance (e.g., antihypertensive medications or beta-blockers)
* Regular sauna or hot-tub use (six or more exposures during the previous 2 months)
* History of heat-related illness
* Any condition that, in the opinion of the investigators, would interfere with safe participation or interpretation of study results
* Inability to understand the study procedures or provide informed consent