Chronic Heat Therapy for Improving Vascular Health
Condition: Cardiovascular Diseases
MeSH terms: Cardiovascular Diseases
Study type: Interventional

Summary: 
      The purpose of the study is to investigate whether long-term heat therapy (i.e. 8 weeks of
      hot tub 4-5x per week) improves biomarkers of cardiovascular health in young, healthy,
      able-bodied individuals. Although exercise is a potent means of improving cardiovascular
      health, many patients are unable to exercise effectively, and thus there is high demand for
      novel therapies to better manage cardiovascular risk in these patients. If successful, this
      study will set the groundwork for heat therapy to be used as an alternative treatment in
      patients who have limited exercise capabilities for the prevention of cardiovascular disease.
    

Detailed description: 
      Exercise training is a potent means of improving cardiovascular (CV) risk; however, exercise
      is challenging for many patient populations. Passive heat therapy may provide a simple and
      effective alternative to exercise for improving CV health, and no one has yet studied the
      physiological benefits of chronic heat exposure in humans. Heat exposure induces the
      expression of heat shock proteins, which can have a multitude of beneficial effects on the CV
      system, many of which are common to exercise training. In particular, these benefits include
      upregulation of many cellular pathways associated with improved vascular function, a
      predominant contributor to CV health. The goal of the study is to determine the effects of
      chronic passive heat therapy on vascular function in young, healthy, able-bodied individuals.
      The investigators will perform a randomized-controlled trial in which subjects participate in
      8 weeks of either heat therapy or thermoneutral water immersion (sham). Heat therapy will
      entail 8 weeks of hot water immersion sufficient to raise core temperature >38.5°C for 1h,
      4-5 times per week. Thermoneutral water immersion will entail 8 weeks of immersion in 36°C
      water for the same duration as heat therapy. In both subject groups, the investigators will
      measure various well-established biomarkers of vascular function before and after 8 weeks of
      heat therapy, including measures of arterial stiffness (arterial compliance, beta-stiffness,
      and pulse wave velocity), endothelium-dependent dilation (flow-mediated dilation), and intima
      media thickness. The investigators will investigate the effects of heat therapy on the
      microvasculature and on the mechanisms behind improvements in vascular function in the
      cutaneous microcirculation, an ideal site for pharmacodissecting the molecular pathways
      involved, using microdialysis paired with laser-Doppler flowmetry. If successful, these
      studies will serve as a basis for developing heat therapy as a novel means of improving CV
      risk, which has the potential to reshape the treatment of patient populations with limited
      exercise capabilities.
    

Intervention name(s): Heat therapy; Thermoneutral water immersion
Intervention type(s): Other; Other
Intervention description(s): Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for heat therapy sessions. In each session, subjects will be immersed in a 40°C hot tub for up to 90min in order to increase body core temperature to 38.5°C and, once there, maintain it between 38.5-39.0°C for 60min.; Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for thermoneutral water immersion sessions. In each session, subjects will be immersed in a 36°C tub for 90min in order to maintain body core temperature at a constant level.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Blood vessels; Heat; Cardiovascular diseases