The Acute Physiological and Perceptual Responses to an Infrared Sauna Blanket - Towards Home-Based Passive Heat Therapy

Passive heat therapy interventions, such as sauna bathing and hot-water immersion, have been shown to improve cardiometabolic health outcomes in healthy and clinical populations. However, most of such heating modalities are costly and inaccessible. PURPOSE: This study investigated the acute physiological and perceptual responses to passive heat therapy using a low-cost and accessible infrared sauna blanket in healthy, young adults. METHODS: Eight participants (2 females, age: 20±1 yrs, BMI: 25±7 kg/m2) completed two randomized trials: HEAT consisted of 60 min of supine rest in an infrared sauna blanket set to ~75 °C (MiHIGH, Australia), whereas during CONTROL the sauna blanket remained off. In both trials, nude body mass and venous blood samples to determine serum interleukin-6 (IL-6) concentration were collected before and immediately after, while sublingual temperature, heart rate, blood pressure and perceptual responses were assessed throughout the session. RESULTS: Sublingual temperature rose from 36.8±0.3°C to 38.2±0.3°C at the end of HEAT, compared with no change during CONTROL (36.7±0.4°C to 36.6±0.3°C; condition x time ppp = 0.017). There was no change in diastolic blood pressure in either trial (HEAT: 74±10 mmHg to 70±6 mmHg, CONTROL: 73±11 mmHg to 69±12 mmHg; time p = 0.108). Total sweat loss was 1.3±0.7 L in HEAT, compared with 0.3±0.3 L after CONTROL (condition pp = 0.171). Thermal sensation (8±1 out of 1 to 9), thermal comfort (4±1 out of 0 to 4) and basic affect (-3±3 out of -5 to +5) reported at the end of HEAT reached close to the upper limit of the scale ranges. CONCLUSION: A single session of passive infrared sauna blanket exposure induced pronounced thermoregulatory and cardiovascular responses in our sample of young healthy adults, consistent with the acute heat stress observed with more traditional heating modalities such as Finnish sauna. These findings indicate that this particular type of infrared sauna blanket may represent a practical, low-cost tool to engage in passive heat therapy, which also paves the way for future home-based passive heat therapy studies.