None listed
Conditions
Brief summary
High blood pressure is a major risk factor for heart disease, and many people are interested in non-medication ways to support heart health. This study aims to understand how exposure to heat (sauna bathing), cold water, and combinations of heat and cold affect blood pressure and heart function in adults. In this study, participants will take part in several supervised sessions involving sauna bathing, cold-water immersion, or both, completed in different orders. Heart rate and blood pressure will be measured before, during, and after each session, and again the following day. By comparing responses within the same person across different conditions, the study will assess how heat, cold, and combined heat–cold exposure influence short-term cardiovascular responses. The study hypothesis is that sauna bathing will temporarily lower blood pressure, and that adding cold-water immersion may change or enhance these effects, compared with heat or cold exposure alone. The findings will help improve understanding of the safety and potential cardiovascular benefits of sauna and cold-water practices.
Interventions
This study investigates the acute and adaptive cardiovascular effects of heat exposure (sauna bathing), cold-water immersion, and combined heat–cold contrast therapy.
Acute randomised cross-over trial):
Participants complete four experimental exposure conditions in a randomised, within-subject cross-over design, with a minimum 48-hour washout period between sessions. A physiologist will administer these experimental procedures. will The four conditions are:
Heat only: 15 minutes of passive hea
This study investigates the acute and adaptive cardiovascular effects of heat exposure (sauna bathing), cold-water immersion, and combined heat–cold contrast therapy. Acute randomised cross-over trial): Participants complete four experimental exposure conditions in a randomised, within-subject cross-over design, with a minimum 48-hour washout period between sessions. A physiologist will administer these experimental procedures. will The four conditions are: Heat only: 15 minutes of passive heat exposure in a wood-fired sauna (approximately 80–90 °C, 5–20% humidity). Cold only: 3 minutes of chest-depth cold-water immersion (approximately 10–12 °C). Heat + cold (single cycle): 15 minutes of sauna exposure immediately followed by 3 minutes of cold-water immersion. Heat + cold (three cycles): Three repeated cycles of 15 minutes in the sauna followed by 3 minutes of cold-water immersion. This will be continuous with no break in-between each cycle. Physiological and perceptual measures are collected at baseline (pre-exposure), immediately post-exposure, 30 minutes post-exposure, and 24 hours post-exposure. All sessions are conducted under standardised conditions with continuous monitoring for safety.
Sponsors
University of Otago
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to 70 Years
Healthy volunteers
Yes
Inclusion criteria
Adults aged 18–70 years Able to provide written informed consent Resting seated blood pressure at screening and on the day of testing within the following range: Systolic blood pressure (SBP): 90–179 mm Hg, and Diastolic blood pressure (DBP): 60–99 mm Hg, and Asymptomatic at the time of testing Individuals with a broad range of blood pressure, including: Normotensive participants (SBP < less than 140 mm Hg and DBP less than 90 mm Hg, not on antihypertensive therapy), and Participants with hypertension (SBP greater than 140 mm Hg and/or DBP greater than 90 mm Hg, or on stable antihypertensive therapy) If taking antihypertensive medication, dose must be stable for =30 days Willing and able to attend all study visits, including follow-up assessments at 24 hours post-exposure Willing to comply with pre-visit standardisation requirements (e.g. hydration, avoidance of alcohol and strenuous exercise prior to sessions) Able to safely undertake sauna bathing and cold-water immersion as determined by screening procedures For participants with menstrual cycles: Willing to have study sessions scheduled during the follicular phase (cycle days 1–14), where applicable
Exclusion criteria
Uncontrolled blood pressure, defined as: Systolic blood pressure (SBP) greater than 180 mm Hg, or Diastolic blood pressure (DBP) greater than 100 mm Hg at screening or on the day of testing Symptomatic hypotension or resting SBP less than 90 mm Hg or DBP less than 60 mm Hg with symptoms History of cardiac arrhythmia, including atrial fibrillation, or abnormal rhythm on screening Recent cardiovascular event, including myocardial infarction within the past 3 months Severe aortic stenosis or other clinically significant structural heart disease Red-flag symptoms at screening or prior to exposure (e.g. chest pain, presyncope, syncope, severe headache, neurological symptoms) Pregnancy or suspected pregnancy Acute illness or infection, including fever or infectious disease within the past 3 weeks History of orthostatic hypotension Inflammatory or medical conditions that may impair tolerance to heat or cold exposure (e.g. acute inflammatory rheumatoid arthritis) Active skin conditions that increase infection risk or impair heat tolerance (e.g. open wounds, oozing rashes, cholinergic urticaria) Any other medical condition deemed by the investigators to pose an unacceptable safety risk during heat or cold exposure
Outcome results
None listed