Body Mass Loss in Dry Sauna and Heart Rate Response to Heat Stress

Abstract

Objectives: The aim of the study was to determine the effects of sauna-induced heat exposure on body mass loss (BML) and its relationships with basic anthropometric and physiological variables. Methods: The sample comprised 230 healthy adult males aged 21.0 ± 1.08 years (age range: 20.0-24.5 years). Body surface area (BSA) was determined and two groups of individuals with high BSA (BSA H ; n = 58) and low BSA (BSA L ; n = 74) were extracted. The intervention consisted of two 10-min dry sauna sessions separated by a 5-min interlude. Pre-, peri-, and post-sauna measures of nude body mass (BM) and heart rate (HR) were taken. Results: BML differed between BSA groups by 0.28 kg (74.81%). Absolute and relative BML most strongly correlated with BM and BSA (p < 0.001). Among the four considered height-weight indexes, the Quetelet I Index and Body Mass Index showed the strongest associations (p < 0.001) with BML whereas the weakest were with the Rohrer Index (p < 0.01) and Slenderness Index ( p < 0.05). Compared with BML, differences in HR were relatively minor (from 9.90% to 18.07%) and a significant association was observed between BML and HR at rest (p < 0.01) and in 10 th and 20 th min of sauna bathing (p < 0.001). Conclusions: The magnitude of BML in healthy adult males after passive heat exposure was dependent on BM and concomitantly BSA. The physiological cost of dry saunainduced thermal strain (as assessed by BML and HR) is greater in individuals with high BM and BSA. BM and HR monitoring is also recommended in order to minimize the risk of homeostatic imbalance and cardiovascular events and this cohort should more frequently cool the body and consume a greater volume of fluids during sauna bathing. Evidence Level II; Prospective comparative study.

The Effects of Repeated Thermal Stress on the Physiological Parameters of Young Physically Active Men Who Regularly Use the Sauna: A Multifactorial Assessment

“…Heart rate is one of the key physiological parameters that change significantly under the influence of thermal stress in a dry sauna. The HR increases significantly even during short stays in the sauna that do not exceed 20 min [21], and it is highly elevated when sauna bathing lasts 45 min and longer. These correlations were investigated by Pilch et al [12] in a study of ten healthy men aged 25-28 years who attended three 15-min sessions in a dry sauna and a steam sauna, with 5-min breaks in between.…”

“…The exposure to thermal stress decreases body mass [18], mainly due to the loss of total body water [21]. The loss of bodily fluids has been estimated at 0.23-2.3 L, depending on the intensity of the physiological processes induced by thermal stress and duration of heat exposure [22].…”

Endocrine Effects of Repeated Hot Thermal Stress and Cold Water Immersion in Young Adult Men

“…15%) ( Podstawski et al, 2019 ). During repeated sauna exposure, a strong relationship was also noted between body mass loss, body surface area and heart rate response in healthy adult males ( Boraczyński et al, 2018 ).…”