Sauna Session Research Articles

Vascular Function after Sauna Bathing in Healthy Older Adults

Repeated heat exposure by immersion in warm water improves vascular function in healthy young adults. This observation could explain the health benefits of sauna bathing reported in population‐based studies, in which regular sauna sessions lasting more than 19 minutes were shown to significantly decrease the risk of cardiovascular mortality. However, it is unknown if such sauna durations improve vascular function in older adults. The purpose of this study was to determine if 20 min of sauna bathing acutely improves vascular function in healthy older adults.Six older adults (4 women) without cardiovascular disease and risk factors (age range: 57–71 yrs) underwent a sauna bathing session consisting of 2 bouts of 10 min in a dry Finnish sauna (80°C) separated by 10 min of seated rest outside the sauna. Prior to and following sauna bathing, flow‐mediated dilation (FMD) of the brachial artery in response to reactive hyperemia induced by 5 min of forearm ischemia was assessed by Doppler ultrasound after a minimum of 30 min rest in the supine position in a quiet and thermoneutral environment. The percent change in artery diameter from baseline to peak was used as an index of macrovascular function, whereas post‐occlusive reactive hyperemia (PORH), estimated by the brachial artery flow area‐under‐the‐curve above baseline during the 3 min following ischemia, was used to evaluate microvascular function. Heart rate (HR), mean arterial pressure (MAP), oral temperature (Toral) and mean skin temperature (Tsk) were monitored throughout the study.Sauna caused an increase in HR (55 ± 8 to 86 ± 10 bpm, P<0.01), mean Tsk (33.0 ± 0.5 to 40.7 ± 0.7°C, P<0.01) and Toral (36.7 ± 0.3 to 37.4 ± 0.2°C, P=0.025) while changes in MAP were not statistically different (100 ± 8 to 90 ± 4 mmHg, p=0.137). At the time of FMD assessment, HR (53 ± 5 and 52 ± 5 bpm, P=0.56), MAP (92 ± 6 and 90 ± 5 mmHg, P=0.59) and Toral (36.8 ± 0.3 and 36.9 ± 0.1 °C, P=0.27) were similar before and after sauna bathing, whereas mean Tsk was elevated prior to the post‐sauna FMD assessment (34.3 ± 0.4 vs. 32.9 ± 0.5°C, P<0.01). FMD was similar before and after sauna bathing (4.79 ± 2.21% vs. 4.86 ± 2.73%, P=0.93). PORH was also similar before and after sauna bathing (286 ± 198 vs. 380 ± 168 ml, P=0.18).These preliminary results indicate that macro‐ and microvascular functions are unaffected by two 10 min bouts of sauna bathing at 80°C in healthy older adults.Support or Funding InformationFunded by Fondation de l'Institut de cardiologie de Montréal and by Fonds de Recherche du Québec – Santé.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Impaired sperm function in infertile men relies on the membrane sterol pattern.

Membrane cholesterol removal appears a key step for the gain of fertility potential during sperm maturation. However, the membrane sterol pattern in sperm cells from infertile patients, with impaired sperm parameters, has been poorly investigated. To elucidate a causative link between sperm membrane composition in male fertility, here we have investigated the levels of cholesterol and its oxidized derivatives 7β-hydroxycholesterol and 7-keto-cholesterol in sixteen infertile patients with oligo-asthenozoospermia and 16 normozoospermic (N) fertile subjects. Furthermore, ten of 16N fertile subjects agreed to receive a defined testicular thermal challenge by adhering to a programme of sauna sessions for 1month. Semen samples were obtained from each of the participants, and sperm parameters were assessed according to the World Health Organization criteria. Sperm levels of cholesterol, 7β-hydroxycholesterol and 7-keto-cholesterol were quantified by ultra-pressure liquid chromatography mass spectrometry. The results showed that oligo-asthenozoospermia patients had a huge amount of cholesterol content compared with fertile subjects (12.40±6.05μg/106 cells vs. 0.45±0.28μg/106 cells, p<0.001, N and oligo-asthenozoospermia, respectively). Also, oxidized derivatives were significantly higher in oligo-asthenozoospermia patients (7β-hydroxycholesterol: 1.96±1.03ng/106 cells vs. 0.075±0.05ng/106 cells, p<0.001 and 7-keto-cholesterol: 1.11±0.72ng/106 cells vs. 0.005±0.003ng/106 cells, p<0.001). Moreover, sauna exposure, in parallel with a progressive worsening of sperm motility parameters, was associated with a reversible increase in sperm cholesterol after the third and fourth week of treatment, whilst 7β-hydroxycholesterol and 7-keto-cholesterol levels showed an earlier enhancement starting from the second week. Our data show for the first time in humans a strong difference in the cholesterol and its oxidized derivatives of infertile and fertile subjects. These findings suggest a strict biochemical link relating testis function, sperm membrane status and male fertility potential.

Sauna Bathing and Risk of Psychotic Disorders: A Prospective Cohort Study

Objective: Sauna bathing has been suggested to promote mental well-being and relaxation, but the evidence is uncertain with respect to mental disorders. We aimed to assess the association of frequency of sauna bathing with risk of psychosis in the Kuopio Ischemic Heart Disease prospective population-based study. Subjects and Methods: Baseline sauna bathing habits were assessed in 2,138 men aged 42–61 years who had no history of psychotic disorders. Participants were classified into three groups based on the frequency of sauna bathing (once, 2–3, and 4–7 times per week). Results: During a median follow-up of 24.9 years, 203 psychotic disorders were recorded. A total of 537, 1,417, and 184 participants reported having a sauna bath once a week, 2–3 times, and 4–7 times per week, respectively. In Cox regression analysis adjusted for age, compared to men who had 1 sauna session per week, the hazard ratio (95% confidence intervals) of psychosis for 4–7 sauna sessions per week was 0.23 (0.09–0.58). In a multivariable model adjusted for several risk factors and other potential confounders, the corresponding hazard ratio was 0.21 (0.08–0.52). The association was similar after further adjustment for total energy intake, socioeconomic status, physical activity, and C-reactive protein (0.22 [0.09–0.54]) and was unchanged on additional adjustment for duration of a sauna session and temperature of the sauna bath (0.23 [0.09–0.57]). Conclusion: Our study suggests a strong inverse and independent association between frequent sauna bathing and the future risk of psychotic disorders in a general male population.

Association of High Cardiovascular Fitness and the Rate of Adaptation to Heat Stress.

This study aimed to compare changes in genes expression associated with inflammation and apoptosis in response to heat stress caused by sauna between people with varying cardiorespiratory fitness levels. We hypothesis that high cardiorespiratory level caused higher positive changes after four weeks of sauna bathing. Blood samples were taken at rest before and after the first and last sauna sessions and 48 hours after the last sauna session and used to assay HSP70 (HSPA1A), HSP27 (HSPB1), interleukin 6 (IL6), and interleukin 10 (IL10) genes expression in blood with quantitative real-time qRT-PCR. Overall, small decreases in rest values of HSPA1A and IL6 mRNA, increase in HSPB1 mRNA, and a significant increase in IL10 mRNA were observed after four weeks of exposure to heat stress. Our findings suggest that an adaptive response to heat stress (an anti-inflammatory response) occurs faster in people with higher cardiorespiratory fitness.

Frequent sauna bathing may reduce the risk of pneumonia in middle-aged Caucasian men: The KIHD prospective cohort study.

Emerging evidence suggests sauna bathing to be linked with numerous health benefits. Having frequent sauna baths has been found to be associated with reduced risk of acute and chronic disease conditions. Sauna bathing may reduce the risk of respiratory diseases; however, the evidence is uncertain. We aimed to assess the association of frequency of sauna bathing with risk of pneumonia. Baseline sauna bathing habits were assessed by administration of questionnaires in a prospective cohort of 2210 men aged 42-61 years. During a median follow-up of 25.6 years, 375 hospital diagnosed cases of pneumonia were recorded. In age-adjusted analyses, the hazard ratios (HRs) 95% confidence intervals (CIs) of pneumonia were 0.67 (0.53-0.83) and 0.53 (0.34-0.84) for participants who had 2-3 and ≥4 sauna sessions per week respectively compared with participants who had≤1 sauna session per week. After further adjustment for several major risk factors, the HRs were 0.69 (0.55-0.86) and 0.56 (0.35-0.88) respectively. The associations remained on additional adjustment for total energy intake, socioeconomic status, physical activity, and C-reactive protein, 0.72 (0.57-0.90) and 0.63 (0.39-1.00) respectively. Frequent sauna baths is associated with reduced pneumonia risk in a middle-aged male Caucasian population.

Sauna Bathing and Incident Hypertension: A Prospective Cohort Study.

Sauna bathing is associated with reduced cardiovascular risk, but the mechanisms underlying this beneficial effect are not entirely understood. We aimed to assess the relationship between sauna bathing and risk of incident hypertension. Frequency of sauna bathing was ascertained using questionnaires in the Kuopio Ischemic Heart Disease Study, a prospective cohort study conducted in Eastern Finland that comprised a population-based sample of 1,621 men aged 42 to 60 years without hypertension at baseline. The incidence of hypertension was defined as a physician diagnosis of hypertension, systolic blood pressure (SBP) >140 mm Hg, diastolic blood pressure >90 mm Hg, or use of antihypertensive medication. During a median follow-up of 24.7 years, 251 incident cases (15.5%) were recorded. In Cox regression analysis adjusted for baseline age, smoking, body mass index, and SBP; compared to participants reporting 1 sauna session per week, the hazard ratio for incident hypertension in participants reporting 2 to 3 sessions and 4 to 7 sessions was 0.76 (95% confidence interval: 0.57-1.02) and 0.54 (0.32-0.91), respectively. The corresponding hazard ratios were similar after further adjustment for glucose, creatinine, alcohol consumption, heart rate, family history of hypertension, socioeconomic status, and cardiorespiratory fitness: 0.83 (95% confidence interval: 0.59-1.18) and 0.53 (0.28-0.98), respectively. Regular sauna bathing is associated with reduced risk of hypertension, which may be a mechanism underlying the decreased cardiovascular risk associated with sauna use. Further epidemiological and experimental studies could help elucidate the effects of sauna bathing on cardiovascular function.

Heat Transfer Analysis of the Human Eye During Exposure to Sauna Therapy

Among the reported health benefits of a sauna session are weight loss, detoxification of the body, and improved blood circulation. Side effects of sauna therapy, both beneficial and detrimental, also exist. It is well known that the human eye is one of the most sensitive parts of the entire human body when exposed to high ambient temperature and humidity levels such as in sauna therapy. This sauna heat interacts with the human eye and may lead to a variety of ocular effects due to radiation emitted by the heater and high ambient temperature. However, the resulting thermophysiologic response of the human eye to various exposure conditions during sauna therapy is not well understood. Therefore, it is of interest to investigate the potential ocular effects that may occur during sauna exposure. This study presents a numerical analysis of heat transfer in a heterogeneous model of a human eye exposed to sauna. The heat transfer model is developed based on porous media theories. In the heterogeneous human eye model, the effects of room air temperature and heater temperature on the intraocular temperature increase are systematically investigated. The study intends to focus attention on the different heat transfer characteristics between conventional sauna (mainly convection) and infrared sauna (mainly radiation). The results show that at the same room air temperature, the circulatory patterns within the anterior chamber of the eye in regard to infrared sauna are more rapid than those for the conventional sauna. Moreover, eye temperature is also higher in the infrared sauna than in the conventional sauna. The maximum temperatures of the eye exposed to conventional and infrared saunas at room air temperature of 80°C are 48.25°C and 52.90°C, respectively. From the values obtained, a guideline can be recommended to indicate the limitations in regard to temperature increase in the human eye due to sauna therapy.

The Comparison of the Wrestlers’ Status of some Physical, Physiological and Growth Hormone Status after Resting, Competition and Sauna Sessions

The aim of this study is to compare some of the physical, physiological, and growth hormone status during the resting, training and after the sauna sessions (80-100°C and10-15% humidity) for wrestlers. Blood samples, for Growth Hormone (GH) were taken and stored during resting time, before breakfast in the morning, after training and the completion of sauna sessions. According to the results of the study; in body temperature and during resting and after training and sauna sessions (p<0.01), in the number of heart beats (NOV), both between resting status and training, sauna sessions and between training and sauna sessions (p<0.01), in reaction time (with right and left hand) both between resting status and training, and between training and sauna sessions (p<0.01), in GH both between resting time and sauna sessions, and between training and sauna sessions, results were stated statistically significant (p<0.01).

The effect of sauna bathing on lipid profile in young, physically active, male subjects.

The aim of the study was to evaluate effects of Finnish sauna bathing on lipid profile in healthy, young men. Sixteen male subjects (20-23 years) were subjected to 10 sauna bathing sessions in a Finnish sauna every 1 or 2 days. The mean sauna temperature was 90±2°C, while humidity was 5-16%. Each session consisted of three 15-minute parts and a 2-minute cool-down between them. The following measurements were taken before and after the sauna sessions: body mass, heart rate, body skinfold thickness. The percentage fat content and then, the lean body mass were calculated. Total cholesterol, triacylglycerols, lipoprotein cholesterol LDL and HDL were measured in blood samples. A statistically significant decrease of total cholesterol and LDL cholesterol was observed during 3 weeks of sauna treatment and in the week afterwards. A significant decline in triacylglycerols was found directly after the 1st and 24 h directly after the 10th sauna session. After the 10th sauna session the level of HDL cholesterol remained slightly increased, but this change was not statistically significant. A decrease in blood plasma volume was found directly after the 1st and the last sauna bathing session due to perspiration. An adaptive increase in blood plasma volume was also found after the series of 10 sauna sessions. Ten complete sauna bathing sessions in a Finnish sauna caused a reduction in total cholesterol and LDL cholesterol fraction levels during the sessions and a gradual return of these levels to the initial level during the 1st and the 2nd week after the experiment. A small, statistically insignificant increase in HDL-C level and a transient decline in triacylglycerols were observed after those sauna sessions. The positive effect of sauna on lipid profile is similar to the effect that can be obtained through a moderate-intensity physical exercise.

Effect of a Single Finnish Sauna Session on White Blood Cell Profile and Cortisol Levels in Athletes and Non-Athletes

The aim of the present study was to investigate the effect of Finnish sauna bathing on a white blood cell profile, cortisol levels and selected physiological indices in athletes and non-athletes. The study evaluated 9 trained middle-distance runners and 9 male non-athletes. The subjects from both groups participated in 15-minute sauna sessions until their core temperature rose by 1.2°C (mean temperature in the sauna room was 96° ± 2°C; relative humidity was 15 ± 3%) with a 2 minute cool down with water at a temperature of 19–20°C. Body mass was measured before and after the session and blood samples were taken for tests. Rectal temperature was monitored at five-minute intervals during the whole session. Serum total protein, haematological indices and cortisol levels were determined. Sauna bathing caused higher body mass loss and plasma volume in the athletes compared to the group of non-athletes. After the sauna session, an increased number of white blood cells, lymphocyte, neutrophil and basophil counts was reported in the white blood cell profile. Higher increments in leukocyte and monocyte after the sauna bathing session were recorded in the group of athletes compared to untrained subjects. The obtained results indicated that sauna bathing stimulated the immune system to a higher degree in the group of athletes compared to the untrained subjects.

Seminal and molecular evidence that sauna exposure affects human spermatogenesis

What are the effects of continuous sauna exposure on seminal parameters, sperm chromatin, sperm apoptosis and expression of genes involved in heat stress and hypoxia? Scrotal hyperthermia by exposure to sauna can induce a significant alteration of spermatogenesis. Several authors have evidenced that high temperature has dramatic effects on spermatogenesis. A longitudinal time-course study. Data from 10 subjects exposed to Finnish sauna were collected before sauna (T0), after 3 months of sauna sessions (T1) and after 3 (T2) and 6 months (T3) from the end of sauna exposure. Ten normozoospermic volunteers underwent two sauna sessions per week for 3 months, at 80-90°C, each lasting 15 min. Sex hormones, sperm parameters, sperm chromatin structure, sperm apoptosis and expression of genes involved in heat stress and hypoxia were evaluated at the start, at the end of sauna exposure and after 3 and 6 months from sauna discontinuation. Student's t-test for paired data was used for statistical analysis. At the end of sauna exposure, we found a strong impairment of sperm count and motility (P < 0.001), while no significant change in sex hormones was present. Decreases in the percentage of sperm with normal histone-protamine substitution (78.7 ± 4.5 versus 69.0 ± 4.1), chromatin condensation (70.7 ± 4.7 versus 63.6 ± 3.3) and mitochondrial function (76.8 ± 4.9 versus 54.0 ± 6.1) were also evident at T1, and strong parallel up-regulation of genes involved in response to heat stress and hypoxia was found. All these effects were completely reversed at T3. Absence of subjects with abnormal sperm parameters was the major limitation of this study. Our data demonstrated for the first time that in normozoospermic subjects, sauna exposure induces a significant but reversible impairment of spermatogenesis, including alteration of sperm parameters, mitochondrial function and sperm DNA packaging. The large use of Finnish sauna in Nordic countries and its growing use in other parts of the world make it important to consider the impact of this lifestyle choice on men's fertility. No external funding was sought for this study and the authors have no conflict of interest to declare.

Thermal stress and oxidant–antioxidant balance in experienced and novice winter swimmers

The adaptation of human organism to environmental stress plays an important role in maintaining good health. The exposure to both low and high ambient temperature may provoke thermal stress and such a condition potentially leads to the excessive production of reactive oxygen species, which may result in oxidative stress. The purpose of the study was to determine the effect of one session of swimming in ice-cold water and one hot sauna session (performed few months later) on oxidant–antioxidant balance in two groups of healthy volunteers: 21 experienced winter swimmers and 19 people who participated in winter swimming for the first time (novices). The activity of antioxidant enzymes: catalase, superoxide dismutase and glutathione peroxidase was measured in erythrocytes of studied persons. Moreover, in blood plasma and erythrocytes the concentration of lipid peroxidation products was estimated. No statistically significant differences in initial values of antioxidant enzymes activity and lipid peroxidation products level were revealed between experienced and novice winter swimmers. The crucial antioxidant enzyme that neutralizes reactive oxygen species generated as a result of thermal stress seems to be catalase, since statistically significant changes of CAT activity after sauna were observed. Increased TBARS level observed as a result of sauna bath proves that exposure of organism to high ambient temperature is a source of oxidative stress. However, such a stress was hardly noticed in regular winter swimmers. The regular baths in cold water combined with sauna probably lead to adaptive changes that protect the organism against harmful effects of thermal stress.

Effects of Sauna Alone Versus Postexercise Sauna Baths on Short-term Heart Rate Variability in Patients With Untreated Hypertension

We measured the effects of sauna bathing alone or a 30-minute exercise session followed by sauna bathing on short-term heart rate variability (HRV) in subjects with untreated hypertension. Ten patients with untreated hypertension (age 59 ± 10 years) were randomly assigned to (1) a control resting session, (2) two 8-minute sauna-only sessions (S), or (3) a 30-minute aerobic exercise session at 75% of maximal heart rate followed by a sauna session (ES). Spectral analysis of HRV was measured with a Polar S810 heart rate monitor at baseline, during the sauna session, and 15 and 120 minutes after the sauna session (T15 and T120). A Fast Fourier Transformation was used to quantify the power spectral density of the low-frequency (LF) and high-frequency (HF) bands. For S and ES conditions, LF (NU, normalized unit) and LF/HF were significantly higher (P < .05 and P < .01) in the first and second sauna sessions, and HF (NU) was significantly lower (P < .05, first sauna). At baseline and T15 for S and ES versus control, LF (NU) and LF/HF were significantly higher (P < .05), and HF (NU) was significantly lower (P < .05), without any effect of the 30-minute exercise session. A single sauna session induced a significant alteration of autonomic cardiovascular control in patients with untreated hypertension, with an increased sympathetic and decreased parasympathetic drive. These alterations were normalized within 15 to 120 minutes after sauna bathing. Additional studies are required to document long-term effects of chronic sauna bathing on autonomic control in patients with hypertension.

The Effects of Repeated Thermal Therapy on Quality of Life in Patients with Type II Diabetes Mellitus

Decreased quality of life in diabetes is associated with poor health outcomes. Far-infrared sauna treatments improve the quality of life for those with chronic pain, chronic fatigue syndrome, depression, and congestive heart failure. The objective of this study is to determine whether far-infrared saunas have a beneficial effect on quality of life in those with type II diabetes. This was a sequential, longitudinal, interrupted time series design study. The setting was Fraser Lake BC, a rural village in central British Columbia, Canada. All patients of the Fraser Lake Community Health Center with type II diabetes were invited to participate in this study. The study consisted of 20-minute, 3 times weekly infrared sauna sessions, over a period of 3 months. To assess quality of life, subjects completed the 36-item Short-form Health Survey Version 2 (SF-36v2) questionnaire as well as "Zero-to-Ten" Visual Analogue Scales. Baseline study parameters were measured within 1 week prior to commencing sauna sessions. Postintervention measurements were collected between 1 and 3 days after the last sauna session. Physical health, general health, and social functioning indices of the SF-36v2 improved. Visual Analogue Scales for stress and fatigue improved. Far-infrared sauna use maybe associated with improved quality of life in people with type II diabetes mellitus. Uptake of infrared saunas use is greater than the uptake of other lifestyle interventions.

Do Far-infrared Saunas Have Cardiovascular Benefits in People with Type 2 Diabetes?

OBJECTIVE Far-infrared saunas are beneficial for the treatment of congestive heart failure, hypertension and obesity. As such, they may have a beneficial effect on cardiovascular (CV) health in those with type 2 diabetes. Our objective is to examine whether or not there are quantitative CV benefits from infrared sauna use. METHODS The intervention consisted of 20-minute, thriceweekly infrared sauna sessions, over a period of 3 months. The following CV risk factors were measured: weight, height, waist circumference, blood pressure (BPtru), glycated hemoglobin (A1C), fasting blood glucose and cholesterol profile. Baseline study parameters were measured within one week prior to commencing sauna sessions. Post-intervention measurements were collected between 1 and 3 days after the last sauna session. RESULTS Systolic blood pressure decreased by 6.4 mm Hg (124±12 vs. 118±15 mm Hg, 95% CI 0.01-12.71 p=0.05), and there was a trend toward decreased waist circumference (115.0±13.4 vs. 112.7±11.9 cm, 95% CI 0.4-5.1 p=0.10). All other measurements did not change significantly. There were no adverse events. Study completion rate was 75%. CONCLUSION Our results suggest that infrared sauna use may be beneficial for lowering blood pressure and waist circumference. Subject adherence to infrared sauna use is greater than adherence to other lifestyle interventions. The combination of favourable compliance/adherence, as well as effectiveness in improving blood pressure and possibly waist circumference, makes infrared sauna therapy an attractive lifestyle option.

Changes in the lipid profile of blood serumin women taking sauna baths of various duration

There is little information on lipid metabolism after sauna treatment in the literature. The present research is aimed to determine the influence of sauna baths on fat metabolism in young women. Twenty healthy, eumenhorreic, female volunteers (19-21 yr old) were exposed to Finnish sauna bath seven times every second day. In group I (n = 10) each time the sauna treatment lasted 30 min, whereas in group II (n = 10) 40 min with 5-minute break to cool down. Body mass, heart rate and blood pressure were measured before and after sauna bath. Rectal temperature was monitored during stay in sauna room. Prior to the sauna bath and during its last two minutes the minute oxygen uptake and the level of CO2 exhalation were analyzed in the exhaled air, and the respiratory quotient RQ was calculated. In the blood samples collected before the sauna bath and immediately afterwards hematocrit, hemoglobin, and lipid profile--total lipids, free fatty acids, total free fatty acids, triacylglycerols, total cholesterol (TC), high density lipids (HDL), low density lipids (LDL) were analyzed. Rectal temperature was lower in the last sauna bath than in the first one. Losses of plasma were greater during the seventh bath than during the first one. Acceleration of the metabolism of lipids occurs after every sauna bath. A reduced level of TC and LDLC and a raised level of HDL was observed after repeated sauna baths. After 2 weeks of repeated sauna session some changes in total cholesterol and concentration of LDLC were observed, while concentration of HDLC increased after 7th sauna bath in group I. Those kinds of changes may be good prognoses of ischemic heart disease prevention, but further research on the influence of sauna on fat metabolism is needed.

Predive Sauna and Venous Gas Bubbles Upon Decompression from 400 kPa

This study investigated the influence of a far infrared-ray dry sauna-induced heat exposure before a simulated dive on bubble formation, and examined the concomitant adjustments in hemodynamic parameters. There were 16 divers who were compressed in a hyperbaric chamber to 400 kPa (30 msw) for 25 min and decompressed at 100 kPa x min(-1) with a 4-min stop at 130 kPa. Each diver performed two dives 5 d apart, one with and one without a predive sauna session for 30 min at 65 degrees C ending 1 h prior to the dive. Circulating venous bubbles were detected with a precordial Doppler 20, 40, and 60 min after surfacing, at rest, and after flexions. Brachial artery flow mediated dilation (FMD), blood pressure, and bodyweight measurements were taken before and after the sauna session along with blood samples for analysis of plasma volume (PV), protein concentrations, plasma osmolality, and plasma HSP70. A single session of sauna ending 1 h prior to a simulated dive significantly reduced bubble formation [-27.2% (at rest) to 35.4% (after flexions)]. The sauna session led to an extracellular dehydration, resulting in hypovolemia (-2.7% PV) and -0.6% bodyweight loss. A significant rise of FMD and a reduction in systolic blood pressure and pulse pressure were observed. Plasma HSP70 significantly increased 2 h after sauna completion. A single predive sauna session significantly decreases circulating bubbles after a chamber dive. This may reduce the risk of decompression sickness. Sweat dehydration, HSP, and the NO pathway could be involved in this protective effect.

Calcitonin Gene-Related Peptide during Sweating in Young Healthy Women

Calcitonin gene-related peptide (CGRP) concentrations are increased in postmenopausal women and castrated men with symptomatic flushing. We wanted to determine if a CGRP increase exists in the plasma of healthy fertile-age women during sweating. Plasma concentrations of CGRP were measured by radioimmunoassay at maximal sweating during a sauna session and during bicycle exercise both at maximal and 70% of maximal work capacity in 8 healthy women of fertile age. Plasma concentrations of CGRP were unaffected (>90% statistical power) during both experimental sessions. We suggest that sweating itself does not explain the rise in CGRP concentrations observed in flushing postmenopausal women.

Effect Of Acute Thermal-induced Hypohydration On Recovery Oxygen Uptake And Heart Rate

The effects of hypohydration on measures of aerobic and anaerobic performance have been well documented. However, research investigating the effect of hypohydration on recovery patterns of VO2 and heart rate following repeated bouts of submaximal exercise has received minimal attention. Purpose To examine the effect of acute thermal-induced hypohydration on rate of recovery of VO2 and heart rate response following repeated bouts of submaximal arm crank ergometry. Methods Ten, lowrisk, male, volunteers (26.7±6 yrs) performed three, one minute arm ergometry exercise bouts, at a workrate equivalent to 1.5 W/kg of body mass, in both a euhydrated and hypohydrated condition. Hypohydration was induced via intermittent sauna exposure (six, 15 min sessions separated by 5 min of recovery) and water restriction, followed by a one-hour, thermoneutral, preexercise, recovery period. Euhydration was characterized by the same sauna exposure with water replacement equivalent to loss of body mass during each of the 15 min sauna sessions, and the same thermoneutral recovery period. The randomized, crossover design was analyzed using ANOVA with repeated measures on all factors. Results Subjects lost a sigificant (p<0.05) amount and percentage of body mass (1.9±0.35 kg; 2.3±0.36%), and showed a sigificant increase in urine specific gravity (1.015±0.007) when hypohydrated. Mean (±SE) time to recover to baseline VO2 in the euhydrated condition (363.72±41.17 s) was not sigificantly different (p>0.05) from the hypohydrated condition (339.43± 28.51 s). Mean (±SE) heart rate at recovery baseline for the euhydrated condition (60.37±3.62 bpm) was not sigificantly different than the hypohydrated condition (61.72±2.97 bpm). Conclusion Acute thermal-induced hypohydration of approximately 2.3% did not adversely affect recovery time, as measured by time to return to baseline VO2, or heart rate in low-risk male subjects following submaximal arm crank ergometry.

Sauna-Induced Rapid Weight Loss Decreases Explosive Power in Women but not in Men

This study aimed at investigating to what extent sauna-induced dehydration is effective to rapidly decrease body weight and whether this practice alters strength and/or explosive power (jump capacity) in healthy athletes. We also investigated whether the observed changes could be rapidly reversed through rehydration. Six male (aged 21.6 +/- 1.8 y) and six female (aged 24.5 +/- 3.7 y) athletes who were not familiar with weight cutting procedures were tested on three occasions: 1) before sauna, 2) after three consecutive sauna sessions (3 x 20 min at 70 degrees C, with 5 min rest interval), and 3) after one hour rehydration period (2.5 ml/kg body weight every 15 min). For rehydration, a carbohydrate beverage (6.3 % glucose, 9.5 mmol/l Na (+), 10 degrees C) was used. Evaluation consisted of body composition, strength (row-strength, handgrip-strength) and jump capacity (squat jump, counter-movement jump and elastic capacity). Sauna-induced dehydration, significantly decreased body weight in men (- 1.8 +/- 0.5 %) and women (-1.4 +/- 0.6 %). This reduction could not be rapidly reversed through rehydration. This weight cutting scheme did not affect strength or jump capacity in men. In women, a statistically significant decrease in squat jump was manifested after rehydration compared to pre-sauna values 23.7 +/- 2.2 vs. 25.2 +/- 1.4 cm, p < 0.05). The squat jump decrease in women was linearly and directly related to the percent reduction of body weight.