Abstract
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 (BSAH; n = 58) and low BSA (BSAL; 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 10th and 20th 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 sauna-induced 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.
Highlights
Dry (Finnish) sauna is commonly administered for its therapeutic benefits,[1] including improved resistance to infection, reduction of toxins, and inducement of psychological and physiological relaxation.[2,3] Sauna is routinely prescribed as an alternative non-pharmacological treatment for patients with certain lifestyle-related medical conditions to relieve symptoms and improve wellness.[2]
This finding is reflected in the magnitude of the coefficient of variation (CV) for the entire sample (45.38%), which was disproportionately larger compared with the CV of the other anthropometric measures (2.88–11.72%) and heart rate (HR) (6.95–9.78%)
Weaker correlations were observed with Rohrer’s index (RI) (p < 0.01) while Slenderness index (SI) correlated with body mass loss (BML) at the threshold of statistical significance (p < 0.05)
Summary
Dry (Finnish) sauna is commonly administered for its therapeutic benefits,[1] including improved resistance to infection, reduction of toxins, and inducement of psychological and physiological relaxation.[2,3] Sauna is routinely prescribed as an alternative non-pharmacological treatment for patients with certain lifestyle-related medical conditions to relieve symptoms and improve wellness.[2] Compared with other whole-body heating therapies, it is well tolerated by the majority of healthy individuals over a wide age range.[4] Sauna bathing is known to benefit the nervous, hormonal, cardiovascular systems[5,6] by inducing a number of positive responses.[4,7]. To eliminate excess body heat, a number of autonomic responses occur including increased heart rate (HR), elevated blood catecholamine concentration, vasodilatation (increasing to 6–8 L/min), intensified lung ventilation, and, most importantly, enhanced perspiration.[4,6,7,8,9] Out of these, vapor evaporation by means of sweating and convective heat exchange (via air flow in lung alveoli and mucous membranes) are essential in situations of thermal stress.[10,11] As the primary thermoregulatory mechanism for heat dissipation, sweating begins when body core temperature crosses a threshold of approximately 37° C
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