Chronic Heat Therapy for Improving Vascular Health

NCT ID: NCT02518399

Last Updated: 2017-10-26

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2013-04-30
• Study Completion Date: 2016-04-30

Brief 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.

Conditions

Cardiovascular Diseases

Keywords

Blood vessels; Heat; Cardiovascular diseases

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: PREVENTION
• Blinding Strategy: NONE

Study Groups

Heat therapy

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.

Group Type: EXPERIMENTAL

Heat therapy

Intervention Type: OTHER

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.

Thermoneutral water immersion

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.

Group Type: SHAM_COMPARATOR

Thermoneutral water immersion

Intervention Type: OTHER

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.

Interventions

Heat therapy

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.

Intervention Type: OTHER

Thermoneutral water immersion

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.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Young, healthy, able-bodied

Exclusion Criteria

• Diagnosis of any chronic diseases related to the cardiovascular system (e.g. hypertension, cardiovascular disease, diabetes, etc.),
• Currently taking prescription medications (except contraceptives)
• Body mass index over 27 kg/m2
• Current smoking
• Currently pregnant or breast-feeding

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 40 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Oregon

OTHER

Sponsor Role: lead

Responsible Party

Christopher T Minson, PhD

Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

University of Oregon

Eugene, Oregon, United States

Countries

United States

References

Brunt VE, Howard MJ, Francisco MA, Ely BR, Minson CT. Passive heat therapy improves endothelial function, arterial stiffness and blood pressure in sedentary humans. J Physiol. 2016 Sep 15;594(18):5329-42. doi: 10.1113/JP272453. Epub 2016 Jun 30.

Reference Type: RESULT

PMID: 27270841 (View on PubMed)

Other Identifiers

14PRE20380300

Identifier Type: OTHER_GRANT

Identifier Source: secondary_id

09272013.025

Identifier Type: -

Identifier Source: org_study_id