Heat Therapy During Reduced Physical Activity

The purpose of this randomized controlled trial is to determine whether daily Finnish dry sauna therapy attenuates the adverse cardiovascular, muscular, and metabolic effects of seven days of experimentally reduced physical activity in healthy adults. Participants will be randomized to one of three groups: (1) maintained habitual physical activity with daily sauna therapy, (2) reduced physical activity with daily room-temperature sauna visits (control), or (3) reduced physical activity with daily sauna therapy. Reduced physical activity will be achieved by decreasing daily step count to approximately 1,000 steps per day with the assistance of a power wheelchair. Outcome measures include vascular endothelial function, exercise tolerance, muscle protein synthesis, body composition, blood pressure, glucose regulation, and physiological responses to heat exposure. The study will determine whether passive heat therapy can serve as a practical intervention to preserve cardiometabolic health during short periods of reduced mobility.

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