Cold Water Swimming-Benefits and Risks: A Narrative Review

Swimming in cold water increases the browning process by diminishing the Myostatin pathway

BACKGROUND

Brown adipose tissue (BAT) is a thermogenic tissue that uncouples oxidative phosphorylation from ATP synthesis and increases energy expenditure via non-shivering thermogenesis in mammals. Cold exposure and exercise have been shown to increase BAT and browning of white adipose tissue (WAT) in mice. This study aimed to determine whether there is an additive effect of exercise during cold exposure on markers related to browning of adipose tissue. in Wistar rats.

METHODS

Twenty-four male Wistar rats were randomly divided into three groups: Control (C, 25˚C), Swimming in Neutral (SN, 30˚C) water, and Swimming in Cold (SC, 15˚C) water. Swimming included intervals of 2-3 min, 1 min rest, until exhausted, three days a week for six weeks, with a training load of 3-6% body weight. After the experimental protocol, interscapular BAT and inguinal subcutaneous white adipose tissue (WAT) were excised, weighed, and processed for beiging marker gene expression.

RESULTS

SN and SC resulted in lower body weight gain, associated with reduced WAT and BAT volume and increased BAT number with greater effects observed in SC. Myostatin protein expression was lower in BAT, WAT, soleus muscle, and serum NC and SC compared to the C group. Expression of the interferon regulatory factor-4 (IRF4) gene in both BAT and WAT tissues was significantly greater in the SC than in the C. Expression of the PGC-1α in BAT was significantly increased in the SC compared to C and increased in WAT in NC and SC. Expression of the UCP1 in BAT and WAT increased in the SC group compared to other groups.

CONCLUSION

The findings demonstrate that six weeks of swimming training in cold water promotes additive effects of the expression of genes and proteins involved in the browning process of adipose tissue in Wistar rats. Myostatin inhibition may possess a regulator effect on the PGC-1α - UCP1 pathway that mediates adipose tissue browning.

The untapped potential of cold water therapy as part of a lifestyle intervention for promoting healthy aging

Healthy aging is a crucial goal in aging societies of the western world, with various lifestyle strategies being employed to achieve it. Among these strategies, hydrotherapy stands out for its potential to promote cardiovascular and mental health. Cold water therapy, a hydrotherapy technique, has emerged as a lifestyle strategy with the potential capacity to evoke a wide array of health benefits. This review aims to synthesize the extensive body of research surrounding cold water therapy and its beneficial effects on various health systems as well as the underlying biological mechanisms driving these benefits. We conducted a search for interventional and observational cohort studies from MEDLINE and EMBASE up to July 2024. Deliberate exposure of the body to cold water results in distinct physiological responses that may be linked to several health benefits. Evidence, primarily from small interventional studies, suggests that cold water therapy positively impacts cardiometabolic risk factors, stimulates brown adipose tissue and promotes energy expenditure-potentially reducing the risk of cardiometabolic diseases. It also triggers the release of stress hormones, catecholamines and endorphins, enhancing alertness and elevating mood, which may alleviate mental health conditions. Cold water therapy also reduces inflammation, boosts the immune system, promotes sleep and enhances recovery following exercise. The optimal duration and temperature needed to derive maximal benefits is uncertain but current evidence suggests that short-term exposure and lower temperatures may be more beneficial. Overall, cold water therapy presents a potential lifestyle strategy to enhancing physical and mental well-being, promoting healthy aging and extending the healthspan, but definitive interventional evidence is warranted.

Hydrophobia, dis/connection, and difference: Understanding Chinese immigrants' fear of coastal swimming in Aotearoa New Zealand

New Zealand's coastal blue spaces, from harbours to beaches, provide diverse wellbeing benefits but can also be sites of danger, fear, and cultural contestation. This qualitative research focuses on Chinese migrants in Auckland, a community who are underrepresented in coastal recreation and overrepresented in drowning statistics. Findings show Chinese migrants dis/connection with coastal blue space and fear of coastal swimming, derived from their homeland habitus and lack of coastal 'blue space' cultural capital. Our research contributes to the growing recognition of 'hydrophobia', and how the racialisation of leisure space impacts the potential for blue spaces and practices to be therapeutic.

Effects of swimming in cold water on lipolysis indicators via fibroblast growth factor-21 in male Wistar rats

This study aimed to investigate the effects of swimming in cold water on the release of FGF21 from various tissues and its impact on fat metabolism. Twenty Wistar rats were randomly divided into three groups: untrained (C), trained in thermo-neutral water (TN, 30 °C) and trained in cold water (TC, 15 °C). The training groups swam intervals (2-3 min) until exhaustion, 1 min rest, three days a week for six weeks, with 3-6% bodyweight load. The mRNA expression of variables was determined in white fat tissue (WAT), and FGF21 protein was also measured in the liver, brown fat tissue (BAT), serum, and muscle. The experimental protocols resulted in lower body weight gain, associated with reduced WAT volume; the most remarkable improvement was observed in the TC group. Swimming significantly increased FGF21 protein levels in WAT, BAT, and muscle tissues compared to the C group; substantial increases were in the TC group. Changes in FGF21 were highly correlated with the activation of genes involved in fat metabolisms, such as CPT1, CD36, and HSL, and with glycerol in WAT. The findings indicate a positive correlation between swimming in cold water and the activation of genes involved in fat metabolism, possibly through FGF21 production, which was highly correlated with fat-burning genes.

Effect of regular winter swimming on blood morphological, rheological, and biochemical indicators and activity of antioxidant enzymes in males

BACKGROUND

Exposure of the human body to cold water triggers numerous beneficial physiological changes. The study aimed to assess the impact of regular winter swimming on blood morphological, rheological, and biochemical indicators and activity of antioxidant enzymes in males.

METHODS

The study involved 10 male winter swimmers (the same participants examined before the season and after the season) and 13 males (not winter swimming, leading a sedentary lifestyle) in the control group. Fasting blood was collected twice: in November and in March of the following year. Basic blood morphological indicators, red cell elongation index (EI) and aggregation index (AI), concentrations of testosterone, cortisol, urea, and creatinine, as well as plasma activity of antioxidant enzymes of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were determined.

RESULTS

The data were collected from the same winter swimmers at the beginning and end of the season. Winter swimming resulted in a significant increase of EI values at a shear stress of 0.30 (p = 0.40), 0.58 (p < 0.001), 4.24 (p = 0.021), 8.23 (p = 0.001), 15.59 (p = 0.001), 30.94 (p = 0.004), and 60.00 Pa (p = 0.043); haemoglobin was lower than before the season (p < 0.027). No significant changes were observed in AI, AMP, T1/2, the levels of urea, creatinine, eGFR, testosterone, cortisol, or the activity of CAT or SOD. There was a statistically significant increase in GPx activity (p = 0.014) and increase in testosterone concentration (p = 0.035) in the group of winter swimmers examined before the season as compared with the control group. No statistically significant differences were found for the mean values of blood morphological indicators and other parameters.

CONCLUSIONS

Winter swimming can prove to be a health-promoting factor in males, as indicated by a rise in the deformability of red blood cells in the blood vessel system after a full season of winter swimming, leading to better body oxygenation, and improves the antioxidant defence and testosterone concentration (within standard limits) in the group of winter swimmers examined before the season as compared with the control group. Winter swimming helps maintain appropriate levels of blood rheological indicators, urea, creatinine, eGFR, cortisol, testosterone, and activity of antioxidant enzymes.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT06223087, 15.01.2024.

Water intake and obesity: By amount, timing, and perceived temperature of drinking water

Water intake has been suggested to be associated with weight control, but evidence for optimal water intake in terms of amount, timing, and temperature is sparse. Additionally, genetic predisposition to obesity, which affects satiety and energy expenditure, might interact with water intake in regulating individual adiposity risk. We conducted a cross-sectional study recruiting 172 Korean adults. Information on water intake and lifestyle factors was collected through self-reported questionnaires, and height, weight, and waist circumference (WC) were measured by researchers. The oral buccal swab was performed for genotyping of FTO rs9939609, MC4R rs17782313, BDNF rs6265 and genetic risk of obesity was calculated. Linear regression was performed to estimate mean difference in body mass index (BMI) and WC by water intake and its 95% confidence interval (95% CI). As a sensitivity analysis, logistic regression was performed to estimate odds ratio (OR) of obesity/overweight (BMI of ≥23kg/m2; WC of ≥90cm for men and of ≥80cm for women) and its 95% CI. Drinking >1L/day was significantly associated with higher BMI (mean difference: 0.90, 95% CI 0.09, 1.72) and WC (mean difference: 3.01, 95% CI 0.62, 5.41) compared with drinking ≤1L/day. Independent of total water intake, drinking before bedtime was significantly associated with lower BMI (mean difference: -0.98, 95% CI -1.91, -0.05). The results remained consistent when continuous BMI and WC were analyzed as categorical outcomes. By perceived temperature, drinking >1L/day of cold water was associated with higher BMI and WC compared with drinking ≤1L/day of water at room-temperature. By genetic predisposition to obesity, a positive association between water intake and WC was confined to participants with low genetic risk of obesity (P interaction = 0.04). In conclusion, amount, timing, and perceived temperature of water intake may be associated with adiposity risk and the associations might vary according to genetic predisposition to obesity.

Effect of a single immersion in cold water below 4 °C on haemorheological properties of blood in healthy men

Cold water immersion (CWI) involves rapid cooling of the body, which, in healthy individuals, triggers a defence response to an extreme stimulus, to which the body reacts with stress. The aim of the study was to determine the effect of CWI on hemorheological blood indicators. The study group consisted of 13 young males. Blood samples were collected before and after CWI. The assessed parameters included the complete blood count, fibrinogen, hs-C-reactive protein (CRP), proteinogram, and blood rheology factors, such as erythrocyte elongation index (EI), half-time of total aggregation, and aggregation index. Additionally, the effect of reduced temperature on primary human vascular endothelium was investigated in vitro. CWI resulted in the decrease of body temperature to 31.55 ± 2.87 °C. After CWI, neutrophil count and mean corpuscular volume (MCV) were significantly increased in the study group, while lymphocyte count was significantly decreased. Significantly higher levels of total blood protein and albumin concentration were detected after the immersion. Among hemorheological characteristics, erythrocyte EIs at shear stress values ranging from 2.19 to 60.30 Pa were significantly lower after CWI. No significant changes in other rheological, morphological or biochemical parameters were observed. In vitro, human umbilical vein endothelial cells responded to 3 h of temperature decrease to 25 °C with unchanged viability, but increased recruitment of THP-1 monocytic cells and changes in cell morphology were observed. This was the first study to evaluate the effect of single CWI on rheological properties of blood in healthy young men. The results indicate that a single CWI may increase blood protein concentrations and worsen erythrocyte deformability parameters.

The Effect of Cold-Water Swimming on Energy Metabolism, Dynamics, and Mitochondrial Biogenesis in the Muscles of Aging Rats

Our study aimed to explore the potential positive effects of cold water exercise on mitochondrial biogenesis and muscle energy metabolism in aging rats. The study involved 32 male and 32 female rats aged 15 months, randomly assigned to control sedentary animals, animals training in cold water at 5 ± 2 °C, or animals training in water at thermal comfort temperature (36 ± 2 °C). The rats underwent swimming training for nine weeks, gradually increasing the duration of the sessions from 2 min to 4 min per day, five days a week. The results demonstrated that swimming in thermally comfortable water improved the energy metabolism of aging rat muscles (increased metabolic rates expressed as increased ATP, ADP concentration, TAN (total adenine nucleotide) and AEC (adenylate energy charge value)) and increased mRNA and protein expression of fusion regulatory proteins. Similarly, cold-water swimming improved muscle energy metabolism in aging rats, as shown by an increase in muscle energy metabolites and enhanced mitochondrial biogenesis and dynamics. It can be concluded that the additive effect of daily activity in cold water influenced both an increase in the rate of energy metabolism in the muscles of the studied animals and an intensification of mitochondrial biogenesis and dynamics (related to fusion and fragmentation processes). Daily activity in warm water also resulted in an increase in the rate of energy metabolism in muscles, but at the same time did not cause significant changes in mitochondrial dynamics.

Blood Morphological and Biochemical Indicator Characteristics in Men Performing Different Physical Activities in the Cold-A Preliminary Report

This descriptive study determined whether winter swimming (WS) and outdoor amateur running (RUN) affect blood morphological and biochemical indicators in men during midseason winter swimming from November to April. There were three groups of participants, with 10 male amateurs each: RUN + WS, WS, and control. The research was performed in the middle of the winter swimming season of 2020/2021. This time period was chosen in consideration of the respondents' adaptation to winter conditions. The study involved only 10 male amateurs in each study group owing to COVID-19 pandemic restrictions, which confined people to their homes. In the RUN + WS group compared with the WS group, significant decreases in the mean corpuscular hemoglobin concentration (within standard limits) (p = 0.04) and platelet distribution width (p = 0.006) were observed, with a significant increase in the red blood cell distribution width (p = 0.008) (within standard limits). The renal function, as expressed by the estimated glomerular filtration rate, was higher in the RUN + WS group (p = 0.02) (within standard limits) compared with the WS group, and the uric acid concentration was reduced (p = 0.01). In the RUN + WS group compared with the control group, significant decreases in the leukocyte count (p = 0.02) (within standard limits), monocyte count (p = 0.04) (within standard limits), and platelet distribution width (p = 0.005) were reported. The remaining indicators presented a p-value > 0.05. The two investigated forms of physical activity had no negative effect on blood morphological or biochemical indicators in male amateurs during the winter swimming midseason.

Laboratory Analysis of the Renal Function Changes Under Long-Term Exposure to Extremely Low Ambient Temperatures: Case Report

The study subject was a healthy, 47-year-old man, a low temperature Guinness World Record holder. He spent 50 days alone in Rovaniemi, Lapland, and functioned in the ambient temperature ranging from +2°C to -37°C. He did not use sources of heat, he did not eat warm meals or drink hot water, and did not dry his clothes. He slept in an igloo, on an ice cover of 20-30 cm. He spent 10 hours a day in a sleeping bag and for the remaining time he walked, skied, or rode a bicycle, and practiced swimming. The aim of the study was a laboratory assessment of renal capacity in a man exposed to long-term extremely low ambient temperatures. The study was approved by the Ethical Committee at the Regional Medical Chamber in Krakow, Poland (approval No.: 194/KBL/OIL/2019). Twice during the observation, urine and blood were collected and analyzed: before and after the prolonged exposure to extremely low ambient temperatures. Changes were seen in many blood and urine parameters, but in urine, they were more significant. In urine, decreased values of sodium (by 53.9%), potassium (by 22.6%), creatinine (by 65.5%), urea (by 61.3%), uric acid (by 58.4%), and protein (by 50%) were observed. Neutrophil gelatinase-associated lipocalin (NGAL) increased by 34%. Absence of calcium oxalate excretion was reported relative to the value before the exposure to cold. In blood, increased values of interleukin-6 (by 60%) and β-2-microglobulin (by 26.9%) were observed. Erythropoietin decreased by 22.4%. No changes were noted in estimated glomerular filtration rate. The study subject lost 10 kg in weight. On the basis of the results obtained during the observation, it can be determined that the probable cause of changes in the laboratory results of the subject was the diet used, and not a dysfunction of the excretory system. The body weight loss and activation of compensating mechanisms focused on saving vitally important diet components, caused by the insufficient diet, exclude the theory of a negative effect of exposure to extremely low temperatures on renal filtration function.

Hypothesized mechanisms of death in swimming: a systematic review

BACKGROUND

The study aims to update the specific classification of mechanisms of death in swimming and to demonstrate these categories are reasonable, by analyzing more characteristics of death cases, evaluating the available evidence and determining their quality.

METHODS

Original articles were queried from PubMed, Web of Science, Embase databases, Cochrane Library, and Scopus. Included studies, which were evaluated as level 4 evidence or higher according to the Oxford Centre for Evidence-Based Medicine, discussed hypothesized mechanisms of death in swimming. Parameters analyzed in this study included decedents' characteristics, outcome measures, findings, methodological index for non-randomized studies (MINORS), and critical evaluation of each study classified by death mechanism.

RESULTS

A total of twenty-five studies were included for further analysis: fourteen were associated with cardiovascular diseases, two were about cerebrovascular diseases, two contained respiratory diseases, seven were about hazardous conditions and three contained other drownings, which provided evidence for mechanisms of death.

CONCLUSIONS

It is found that cardiovascular disease is the main cause or contributing factor of death in swimming. Respiratory diseases and cerebrovascular diseases are difficult to be definitive mechanism categories due to insufficient evidence. Hazardous conditions appear to be one of the possible risk factors because there are more cases of deaths from unsafe environments in swimming, but further statistics and research are still needed to support this view. Our study may have important implications for developing potential prevention strategies for sports and exercise medicine.

TRIAL REGISTRATION

PROSPERO ID (CRD42021267330). Registered Aug 13th 2021.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

The swimming habits of women who cold water swim

BACKGROUND

Cold water swimming is growing in popularity, especially among women. We have previously reported that women felt that cold water swimming helps with their menstrual and menopause symptoms. But little is known about the habits of women who cold water swim.

OBJECTIVES

To determine the habits of women who cold water swim.

DESIGN

This was a mixed-methods study.

METHODS

An online survey asked women who cold water swim about their experience of swimming and how this affected their menstrual and menopause symptoms. The survey was advertised for 2 months on social media, with a focus on advertising in cold water swimming Facebook groups. In this article, only the questions on the women's swimming habits were analyzed.

RESULTS

The analysis of 1114 women, mainly from the United Kingdom, revealed that most had been swimming for 1-5 years (79.5%). Most swim in the sea (64.4%), and only 15.5% swim alone. The majority (89.0%) swim all year around, swimming for mainly 30-60 min in the summer and 5-15 min in the winter. The women mostly swim wearing swimming costumes (skins) throughout the year. The majority of the free-text responses showed women found mental and physical benefits from cold water swimming.

CONCLUSION

It was not surprising to learn that women swim for longer in the summer than the winter, but hearing how they feel cold water swimming helps their physical and mental health is important. With the limitations on access and safety of many wild swimming sites in the United Kingdom, it is time to ensure that cold water swimming is safer and more supported.

The influence of whole-body cryotherapy or winter swimming on the lipid profile and selected adipokines

PURPOSE

The aim of this study was to investigate the effect of a series of 20 whole-body cryotherapy (WBC) sessions and 20 winter swimming sessions on the lipid profile and selected adipokines.

MATERIALS/METHODS

The experimental group consisted of 30 people who underwent a series of WBC treatments and 30 people who underwent a winter swimming. The control group consisted of 30 people - without intervention. Study 1: on the day of the commencement of whole-body cryotherapy / at the beginning of the winter swimming season; and Study 2: after a series of 20 cryotherapy sessions / at the end of the winter swimming season. The control group was also tested twice (4-week break). There were 20 WBC treatments - 5 times a week (4 weeks) and 20 cold water baths - once a week (20 weeks).

RESULTS

A statistically significant increase in the concentration of adiponectin, resistin and leptin in women and resistin and leptin in men was observed after the winter swimming season. Differences were also found in the second study between the groups of women using WBC and the control group, as well as the groups of women swimming and the control group. In men, however, these differences were observed in WBC and the control group. The significance level of α = 0.05 was adopted in the analyzes.

CONCLUSIONS

The use of WBC may changes in the lipid profile and selected adipokines in men. Regular winter swimming may changes of selected adipokines in both women and men.

Cold water swimming as an add-on treatment for depression: a feasibility study

PURPOSE

Cold water swimming (CWS) involves taking a regular dip in cold, natural waters throughout the winter. The evidence for the health benefits of CWS has been anecdotal, or from small-sample size studies. The available literature reports that CWS abolishes general tiredness, improves mood, boosts self-esteem and improves general well-being. However, research on the effects and safety of CWS as an add-on to the regular treatment of depression is limited. The aim of this study was to investigate whether it is possible and safe for patients with depression to participate in CWS.

MATERIAL AND METHODS

The study was designed as an open-label feasibility study. All patients aged 20-69 years with a diagnosis of depression from an outpatient clinic were eligible for inclusion. The intervention consisted of twice-weekly, group-based CWS.

RESULTS

Thirteen patients were initially recruited, and five patients participated on a regular basis. Although several patients had somatic comorbidities, all patients passed the somatic evaluation and were physically fit to participate in CWS. Patients who participated regularly in the CWS sessions had a well-being score of 39.2; at the end of the study, their score had increased to 54.0 and PSQI score at baseline was 10.4 (3.7); at the end of the study it was 8.0 ((3.7).

CONCLUSION

This study indicates that it is possible and safe for patients with depression to participate in regular, supervised CWS. Furthermore, regular participation in CWS may improve sleep and well-being.

The Effects of Whole-body Cold-water Immersion on Brain Connectivity Related to the Affective State in Adults Using fMRI: A Protocol of a Pre-post Experimental Design

An emerging body of behavioural studies indicates that regular swimming in cold water has positive effects on mental health and wellbeing, such as reducing fatigue, improving mood, and lessening depressive symptoms. Moreover, some studies reported immediate effects of cold-water immersion (CWI) on elevating mood and increasing a positive emotional state. However, the neural mechanisms underlying these effects remain largely unknown. The lack of studies using neuroimaging techniques to investigate how a whole-body CWI affects neural processes has partly resulted from the lack of a tested experimental protocol. Previous protocols administered tonic limb cooling (1-10 °C) while recording functional magnetic resonance (fMRI) signals. However, using very low water temperature constitutes points of contrast to painful experiences that are different from what we experience after a whole-body head-out CWI. In our protocol, healthy adults unhabituated to cold water were scanned twice: immediately before (pre-CWI) and after (post-CWI) immersion in cold water (water temperature 20 °C) for 5 min. We recorded cardiac and ventilatory responses to CWI and assessed self-reported changes in positive and negative affects. Our protocol showed reliable changes in brain connectivity after a short exposure to cold water, thus enabling its use as a tested experimental framework in future studies.

Exercise in cold: Friend than foe to cardiovascular health

Exercise has been proven to benefit human health comprehensively regardless of the intensity, time, or environment. Recent studies have found that combined exercise with a cold environment displays a synergistical beneficial effect on cardiovascular system compared to exercise in thermoneutral environment. Cold environment leads to an increase in body heat loss, and has been considered a notorious factor for cardiovascular system. Exercise in cold increases the stress of cardiovascular system and risks of cardiovascular diseases, but increases the body tolerance to detrimental insults and benefits cardiovascular health. The biological effects and its underlying mechanisms of exercise in cold are complex and not well studied. Evidence has shown that exercise in cold exerts more noticeable effects on sympathetic nervous activation, bioenergetics, anti-oxidative capacity, and immune response compared to exercise in thermoneutral environment. It also increases the secretion of a series of exerkines, including irisin and fibroblast growth factor 21, which may contribute to the cardiovascular benefits induced by exercise in cold. Further well-designed studies are needed to advance the biological effects of exercise in cold. Understanding the mechanisms underlying the benefits of exercise in cold will help prescribe cold exercise to those who can benefit from it.

Effects of 3-week repeated cold water immersion on leukocyte counts and cardiovascular factors: an exploratory study

Aim: This exploratory study aimed to investigate the effects of a 3-week repeated cold water immersion (CWI) intervention on leukocyte counts and cardiovascular factors (mean arterial pressure [MAP], heart rate [HR]) in healthy men. Methods: A total of n = 12, non-cold-adapted men (age: 25.2 ± 4.0 years; height: 177.8 ± 5.6 cm; weight: 73.8 ± 6.5 kg) were randomly allocated to the CWI or control (CON) group. The CWI group underwent a 3-week repeated CWI intervention (12min at 7°C, 4x/week). The CON group did not receive any cold exposure or therapy. Total leukocyte numbers and proportions (neutrophils, basophils, eosinophils, monocytes, lymphocytes) and cardiovascular factors (MAP, HR) were assessed at baseline and after the 3-week intervention period. Results: Total leukocyte count decreased in CWI (p = 0.027, 95% CI -2.35 to -0.20 × 103/µL) and CON (p = 0.043, 95% CI -2.75 to -0.50 × 103/µL). CWI showed a decrease in neutrophil number (p = 0.028, 95% CI -1.55 to -0.25 × 103/µL) and proportion (p = 0.046, 95% CI -6.42 to 0.56%). In contrast, CON showed no significant change (p > 0.05). No differences were found for other leukocyte subtypes in CWI or CON (all p > 0.05). MAP (p = 0.028, 95% CI -17 to -8 mmHg) and HR (p = 0.027, 95% CI -7 to -2 bpm) were reduced in CWI, whereas CON showed no change (p > 0.05). Conclusion: The results suggest no relevant effects of 3-week repeated CWI on leukocyte counts in healthy men. Due to methodological limitations, the effects on the investigated cardiovascular factors remain unclear. Further studies with larger sample sizes are needed to examine the effects on immune function and cardiovascular health.

The forgotten art of cold therapeutic properties in cancer: A comprehensive historical guide

Cold therapy has been used for centuries, from Julius Caesar to Mohandas Gandhi, as a potent therapeutic approach. However, it has been largely forgotten in modern medicine. This review explores the history of cold therapy and its potential application as a therapeutic strategy against various diseases, including cancer. We examine the different techniques of cold exposure and the use of other therapeutical approaches, such as cryoablation, cryotherapy, cryoimmunotherapy, cryothalectomy, and delivery of cryogen agents. While clinical trials using cold therapy for cancer treatment are still limited, recent research shows promising results in experimental animal cancer models. This area of research is becoming increasingly significant and warrants further investigation.

Clinical effects of Kneipp hydrotherapy: a systematic review of randomised controlled trials

OBJECTIVE

Hydrotherapy is a traditional prevention and treatment strategy. This study's aim is to systematically review all available randomised controlled trials (RCTs) investigating clinical effects of hydrotherapy according to Kneipp which is characterised by cold water applications.

METHODS

RCTs on disease therapy and prevention with Kneipp hydrotherapy were included. Study participants were patients and healthy volunteers of all age groups. MEDLINE (via PubMed), Scopus, Central, CAMbase, and opengrey.eu were systematically searched through April 2021 without language restrictions and updated by searching PubMed until April 6th 2023. Risk of bias was assessed using the Cochrane tool version 1.ResultsTwenty RCTs (N=4247) were included. Due to high heterogeneity of the RCTs, no meta-analysis was performed. Risk of bias was rated as unclear in most of the domains. Of 132 comparisons, 46 showed significant positive effects in favour of hydrotherapy on chronic venous insufficiency, menopausal symptoms, fever, cognition, emotional function and sickness absenteeism. However, 81 comparisons showed no differences between groups and 5 were in favour of the respective control group. Only half of the studies reported safety issues.

CONCLUSION

Although RCTs on Kneipp hydrotherapy seem to show positive effects in some conditions and outcomes, it remains difficult to ascertain treatment effects due to the high risk of bias and heterogeneity of most of the considered studies. Further high-quality RCTs on Kneipp hydrotherapy are urgently warranted.

PROSPERO REGISTRATION NUMBER

CRD42021237611.

Case of transient global amnesia-like syndrome after recreational cold-water swimming

We document a case of a transient global amnesia (TGA)-like syndrome following open water swimming. This case was atypical for TGA, in that symptoms were prolonged and ischaemic infarct was considered within the differential. MRI did not demonstrate any changes associated with acute ischaemia although did show a mild degree of small vessel change. With amnesia taking greater than 24 hours to resolve, we have labelled this case to be a TGA-like syndrome, provoked by the commonly reported TGA precipitant of cold water immersion. The possibility of a tiny, strategic infarct causing these symptoms was considered and antiplatelet therapy commenced.

Case report: Open water swimming as a possible treatment for asthma

Asthma is a complex medical problem for which currently available treatment can be incompletely effective. This case report describes a 49 year old woman who had suffered from asthma since her teenage years that resolved after she took up regular open water swimming. After sharing this case report with an international open water swimming community on social media, over one hundred people with asthma commented that their symptoms had also improved after taking up this activity. The mechanism whereby open water swimming might alleviate asthma has not been established. Possibilities include benefits to mental health, anti-inflammatory effects, being more fit, improved immune function and suppression of the bronchoconstrictive component of the diving reflex. Further research might usefully confirm or refute these clinical observations.

Swimming in cold water upregulates genes involved in thermogenesis and the browning of white adipose tissues

The purpose of this study was to investigate whether there is an interacting effect of six weeks of swimming in cold water on the gene expression of browning markers in adipose tissue in rodents. Twenty male Wistar rats were randomly divided into four groups: Control (C, 25 °C), Cold Exposure (CE, 4 °C), Swimming in tepid Water (STW, 30 °C), and Swimming in Cold Water (SCW, 15 °C). The swimming included 2-3 min intervals, 1 min rest, until exhaustion, three days a week for six weeks, with 3 to 6% of bodyweight overload. Rats from CE were exposed to cold for 2 h per day, five days per week. After the experimental protocol, interscapular brown (BAT) and inguinal subcutaneous white (WAT) fat tissues were excised, weighed, and processed for beiging and mitochondrial biogenesis markers gene expression. The experimental protocols resulted in an apparent increase in the number of brown adipocytes (per mm²) in the adipose deposits compared to the C group; substantial changes were observed in the SCW group. Compared to other groups, cold exposure alone increased significantly serum norepinephrine, and also β₂-adrenergic receptor expression was upregulated in the adipocytes compared to the C group. The STW group increased the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) coactivator-1 alpha (PGC-1α), β₂-adrenergic receptor, and CCAAT/enhancer-binding proteins-α(c/EBP-α) in WAT in comparison with the C group(p < 0.05). In both adipocytes, the SCW intervention significantly upregulated the expression of PGC-1α, PPAR-γ, and c/EBP-α genes in comparison with the C and CE groups. In addition, the expression of TFAM and UCP1 was upregulated substantially in the SCW group compared to other groups. Our data demonstrate that swim training and cold exposure present additive effects in the expression of genes involved in the beiging process and mitochondrial biogenesis markers in BAT and WAT. In addition, it seems that the upregulation of these genes is related to the activation of β₂-adrenergic receptors.

Sea swimming and snorkeling in tropical coastal blue spaces and mental well-being: Findings from Indonesian island communities during the COVID-19 pandemic

The COVID-19 pandemic has considerable mental health impacts. Immersive nature-based interventions, such as swimming or snorkeling, may help mitigate the global mental health crisis caused by the pandemic. To investigate this, we collected cross-sectional data from residents of coastal villages (n = 308) in Kepulauan Selayar, Indonesia. Analysis of Covariance (ANCOVA) was used with mental well-being as the outcome variable, operationalized as the Mental Component Summary (MCS) scores from the SF-12 (12-item Short Form Health Survey). After adjusting for covariates, the activity of sea swimming or snorkeling was found to be significantly associated with better mental well-being (η² = 0.036; p < 0.01). Predictive margins analysis revealed that those who engaged in sea swimming or snorkeling for one to three days a week gained a 2.7 increase in their MCS scores, compared to those who did not. A non-linear dose-response relationship was detected: for those swimming or snorkeling more than three days per week, there was only an increase of 1.7 MCS score compared to the 0-day. Overall this study contributes to the expanding of evidence base, showing that interactions with blue spaces can be beneficial for mental health, especially in a potentially stressful time such as the current pandemic.

Management implications

The positive association between the activity of swimming or snorkeling in open seas and the mental well-being of rural coastal communities in Indonesia during the COVID-19 pandemic indicates that access to coastal blue spaces is important in a time of uncertainties and high stress. Ensuring that local communities have continuous access to these spaces is the key challenge for all relevant stakeholders, particularly in light of the growing privatization of the local coastal environment for the sake of tourism. However, considering the importance that these blue spaces hold for the mental well-being of local communities, intensive dialogue amongst these stakeholders must be pursued to ensure that the development of the area does not jeopardize the collective well-being of the people already living there.

Analysis of Factors Associated With Continued Cooling of Core Temperature After Prolonged Cold-Water Swimming

PURPOSE

To assess the factors associated with continued cooling duration of core temperature (Tcore°) after prolonged outdoor cold-water swimming.

METHODS

We designed a cohort study among swimmers participating in an outdoor cold-water swim during qualifying for the English Channel Swim. The day before the event, the participants completed a demographic questionnaire, and body composition was measured using bioelectrical impedance analysis (mBCA 525, Seca). The swimming event consisted of laps over a 1000-m course, for up to 6 hours, in water at 12.5 to 13 °C. Tcore° was measured using an ingestible temperature sensor (e-Celsius, BodyCap) during and up to 1 hour after the swim.

RESULTS

A total of 14 participants (38 [11] y; N = 14, n = 11 males, n = 8 in swimming costume and n = 6 in wetsuit) were included. Before swimming, Tcore° was 37.54 (0.39) °C. The participants swam for an average of 194.00 (101.94) minutes, and mean Tcore° when exiting the water was 35.21 (1.30) °C. The duration of continued cooling was 25 (17) minutes with a minimum Tcore° of 34.66 (1.26) °C. Higher body mass index (r = .595, P = .032) and fat mass (r = .655, P = .015) were associated with longer continued cooling, independent of wetsuit wear. Also, the rate of Tcore° drop during swimming (-1.22 [1.27] °C/h) was negatively correlated with the rate of Tcore° gain after swimming (+1.65 [1.23] °C/h, r = -.682, P = .007).

CONCLUSION

Increased body mass index and fat mass were associated with Tcore° continued cooling duration after prolonged outdoor cold-water swimming at 12.5 to 13 °C. The rate of Tcore° drop during swimming was negatively correlated with the rate of rewarming.

Short-Term Head-Out Whole-Body Cold-Water Immersion Facilitates Positive Affect and Increases Interaction between Large-Scale Brain Networks

An emerging body of evidence indicates that short-term immersion in cold water facilitates positive affect and reduces negative affect. However, the neural mechanisms underlying these effects remain largely unknown. For the first time, we employed functional magnetic resonance imaging (fMRI) to identify topological clusters of networks coupled with behavioural changes in positive and negative affect after a 5 min cold-water immersion. Perceived changes in positive affect were associated with feeling more active, alert, attentive, proud, and inspired, whilst changes in negative affect reflected reductions in distress and nervousness. The increase in positive affect was supported by a unique component of interacting networks, including the medial prefrontal node of the default mode network, a posterior parietal node of the frontoparietal network, and anterior cingulate and rostral prefrontal parts of the salience network and visual lateral network. This component emerged as a result of a focal effect confined to few connections. Changes in negative affect were associated with a distributed component of interacting networks at a reduced threshold. Affective changes after cold-water immersion occurred independently, supporting the bivalence model of affective processing. Interactions between large-scale networks linked to positive affect indicated the integrative effects of cold-water immersion on brain functioning.

The Influence of Winter Swimming on Oxidative Stress Indicators in the Blood of Healthy Males

Baths in cold water are a popular physical activity performed to improve health. This study aimed to determine whether repeated cold-water exposure leads to the up-regulation of antioxidant defenses and whether or not this leads to a reduction in basal and/or acute pulses of oxidative distress in humans. The study group consisted of 28 healthy male members of the WS club (average age 39.3 ± 6.1 years). The study sessions occurred at the beginning and the end of the WS season. During the WS season, the participants took 3-min cold-water baths in a cold lake once a week. Blood samples were collected three times during each session: before the bath, 30 min after the bath, and 24 h after the bath. The activity of selected antioxidant enzymes, including superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx), as well as the concentration of lipid peroxidation (LPO) products, including thiobarbituric acid-reactive substances (TBARS) and conjugated dienes (CD), were determined in erythrocytes. The concentration of TBARS, CD, retinol, and α-tocopherol were determined in the blood plasma, whereas the level of other LPO products, including 4-hydroxynonenal and 8-iso-prostaglandin F2α, were determined in the blood serum. The repeated cold exposure up-regulated most antioxidant defenses, and this led to an attenuation of most indicators of oxidative stress at the baseline and acute pulses in response to cold exposure. In conclusion, due to regular cold exposure, the antioxidant barrier of winter swimmers was stimulated. Thus, short cold-bath sessions seem to be an effective intervention, inducing promoting positive adaptive changes such as the increased antioxidant capacity of the organism.

Health effects of voluntary exposure to cold water - a continuing subject of debate

This review is based on a multiple database survey on published literature to determine the effects on health following voluntary exposure to cold-water immersion (CWI) in humans. After a filtering process 104 studies were regarded relevant. Many studies demonstrated significant effects of CWI on various physiological and biochemical parameters. Although some studies were based on established winter swimmers, many were performed on subjects with no previous winter swimming experience or in subjects not involving cold-water swimming, for example, CWI as a post-exercise treatment. Clear conclusions from most studies were hampered by the fact that they were carried out in small groups, often of one gender and with differences in exposure temperature and salt composition of the water. CWI seems to reduce and/or transform body adipose tissue, as well as reduce insulin resistance and improve insulin sensitivity. This may have a protective effect against cardiovascular, obesity and other metabolic diseases and could have prophylactic health effects. Whether winter swimmers as a group are naturally healthier is unclear. Some of the studies indicate that voluntary exposure to cold water has some beneficial health effects. However, without further conclusive studies, the topic will continue to be a subject of debate.

The Value of Myocardium and Kidney Histopathological and Immunohistochemical Findings in Accidental Hypothermia-Related Fatalities

Background and Objectives: The post-mortem diagnosis of hypothermia is challenging in forensics. The aim of our study was to detect the kidney and heart histopathological changes that occurred in a group of hypothermia-related fatalities. Materials and Methods: The cohort included 107 cases identified in the database of our department between 2007 and 2021, which have been associated with extreme cold stress. Demographic and clinicopathological data were collected from the medico-legal reports. Archived tissue samples were evaluated to identify the histopathological features, in routine haematoxylin-eosin (H&E), Periodic acid-Schiff (PAS), and Masson's trichrome stainings, while cardiac sirtuin1 (SIRT1) and renal ubiquitin (Ub) immunostaining have been performed. Results: The majority of cases exposed to low temperatures were males (76%) from rural regions (68.2%) during the cold season. Paradoxical undressing was documented in 9.3% of cases. The common comorbidities included alcoholism (50.5%), neuropsychiatric diseases (10.3%), diabetes mellitus (3.7%), and lung tuberculosis (4.7%). The microscopic heart exam revealed areas of myocardial degeneration (100%), contraction bands (95.3%), fatty change (13.1%) and focal wavy contractile myocardial cells. Basal vacuolisation of renal tubular epithelial cells (Armanni-Ebstein lesions) (21.5%), focal tubular necrosis (7.5%), tubular renal cysts (7.5%), interstitial haemorrhages (5.6%), diabetic kidney disease (3.7%), background benign nephroangiosclerosis (42.1%), variable thickening of tubules and corpuscles basement membranes, capsular space amorphous material, and intratubular casts were identified in kidney tissue samples. Myocardial cells displayed SIRT1 weak expression, with a loss of immunopositivity correlated with areas with contraction bands, while a variable Ub expression was observed in renal corpuscles capsules, proximal, distal, and collecting renal tubules, Henle's loops, urothelium, and intratubular casts. Conclusions: In the context of the current concept that death associated with hypothermia is still a diagnosis of exclusion, our findings suggest that the microscopic exam provides relevant data that support the diagnosis of hypothermia-related fatalities in appropriate circumstances of death. A deeper insight into the histopathologic findings in hypothermic patients may lead to new therapeutic approaches in these cases.

Effects of Low-Ambient-Temperature Stimulation on Modifying the Intestinal Structure and Function of Different Pig Breeds

Simple Summary

Low ambient temperature resulted in the body’s cold stress response, while local wild boars in the middle-temperate zone performed better than commercial pigs. Therefore, three breeds—Large White (LW) pigs, a local Mashen (MS) pig breed and Jinfen White (JFW) pigs, a hybrid breed from wild boar—were investigated in an artificial climate chamber. The results implicated that low-ambient-temperature stimulation increased trypsin activity in duodenal chyme and promoted inflammatory response in Mashen pigs. The cold-resistance mechanism of MS pigs should be explored to reduce hogs’ stress caused by low-ambient-temperature stimulation.

Abstract

Ambient temperature (Ta) fluctuation is a key factor affecting the growth performance and economic returns of pigs. However, whether the response of intestinal structure and function are related to pig breeds in low Ta has not been investigated yet. In this study, Large White (LW) pigs, Jinfen White (JFW) pigs and Mashen (MS) pigs were raised in artificial climate chambers under normal Ta (25 °C) and low Ta (4 °C) for 96 h. Afterwards, the decrease in body temperature and complete blood counts (CBC) of all pigs were measured. Hematoxylin–eosin, immunohistochemical staining, qPCR and ELISA were used to investigate their intestinal mucosa integrity and inflammatory response. The results showed that MS pigs could maintain a normal body temperature and villus structure after 4 °C stimulation compared with those of LW and JFW pigs. Villus height and villus height/crypt depth of MS pigs were significantly higher than those of LW and JFW pigs at 4 °C. Low-Ta stimulation increased the digestion of carbohydrates of all pigs. Meanwhile, low Ta enhanced the activity of lipase in LW pigs and increased trypsin activity in MS and JFW pigs. Furthermore, low-Ta stimulation significantly downregulated the protein of tight junction and upregulated the mRNA expression of inflammatory cytokines in MS pigs. MS pigs also showed stronger spleen immune function at 4 °C. These results indicated that the local MS pig breed had stronger intestinal function in low Ta by producing a stronger inflammatory response, which lays the foundation for further study on the mechanism of cold tolerance in pigs.

The Use of Cryotherapy in Cosmetology and the Influence of Cryogenic Temperatures on Selected Skin Parameters—A Review of the Literature

Cryotherapy is becoming an increasingly popular method used in medicine, physiotherapy, and cosmetology. It is used in the form of whole-body cryotherapy (WBC) and local cryotherapy. It is a tool for achieving analgesic and anti-inflammatory effects. Since the beginning of its use, its influence on the mental state has also been pointed out. The aim of this study was to analyze the available literature on the effect of cryogenic temperatures on the skin and the mechanisms induced by such a stimulus and its influence on well-being. A literature search of keywords or phrases was performed in PubMed®. Various effects of WBC on skin characteristics (hydration, pH, level of transepidermal water loss), mechanisms of anti-inflammatory effects, and effects on adipocytes were shown. Research on the impact of individual skin characteristics is not consistent. Positive effects on the reduction of inflammation and oxidative stress have been noted. Cryotherapy is also successfully used in dermatology to treat lentil spots, actinic keratosis, and ingrown toenails, remove viral warts, or relieve itching in atopic dermatitis. The results of the review also indicate the effectiveness of WBC as an adjunctive treatment for obesity. The number of papers available on the direct effects of WBC on the skin is still limited, despite the fact that it represents the first contact of the human body with cryogenic temperatures. Available data show that cold as a physical stimulus can be a safe and useful tool in cosmetology.

Increasing energy expenditure through exercise and low ambient temperature offers oxidative protection to the hypothalamus after high-fat feeding to mice

The effects of weight loss produced by increased energy expenditure on measures of oxidative stress and mitochondrial damage have not been investigated in the hypothalamus of diet-induced obese mice. The present study aimed to characterize the effects of either a low housing temperature of 17°C or daily exercise on a treadmill on high-fat diet (HFD)-induced abnormalities in the hypothalamic tissue of mice. Exercise and low ambient temperature protocols were designed to produce energy deficit through increased energy expenditure. Forty mice aged 8 weeks were assigned to one of four conditions: chow diet (n = 10), HFD (n = 10), HFD and 5 weeks of either exercise training (ET; n = 10) or an ambient temperature of 17°C (n = 10). Mice were killed at the age of 31 weeks. In comparison with HFD treatment alone, both interventions reduced body adiposity (14.6% and 27.6% reduction for the ET and 17°C groups, respectively). Moreover, exposing obese mice to ET and 17°C restored mitochondrial DNA content (41.3% and 32.6% increase for the ET and 17°C groups, respectively), decreased level of lipid peroxidation as assessed by the detection of 4-hydroxy-nonenal protein adducts (12.8% and 29.4% reduction for the ET and 17°C groups, respectively) and normalized the expression levels of proinflammatory cytokines (Tnfα: 73.9% and 62%; Il1β: 54.5% and 39.6%; Il6: 33.1% and 35.6% reduction for the ET and 17°C groups, respectively), as well as several proteins associated with mitochondrial respiratory chain (OxPhos Complex I: 75.7% and 53.9%; Complex III: 33% and 36%; Complex V: 42% and 36.9% reduction for the ET and 17°C groups, respectively) in hypothalamic cells. Negative energy balance induced through either lower ambient temperature or exercise resulted in substantial and similar improvements in markers of inflammation and mitochondrial damage in the hypothalamus of mice with diet-induced obesity, potentially by reducing oxidative stress.

Temperature-Dependent Regulation of Proteostasis and Longevity

Temperature is an important environmental condition that determines the physiology and behavior of all organisms. Animals use different response strategies to adapt and survive fluctuations in ambient temperature. The hermaphrodite Caenorhabditis elegans has a well-studied neuronal network consisting of 302 neurons. The bilateral AFD neurons are the primary thermosensory neurons in the nematode. In addition to regulating thermosensitivity, AFD neurons also coordinate cellular stress responses through systemic mechanisms involving neuroendocrine signaling. Recent studies have examined the effects of temperature on altering various signaling pathways through specific gene expression programs that promote stress resistance and longevity. These studies challenge the proposed theories of temperature-dependent regulation of aging as a passive thermodynamic process. Instead, they provide evidence that aging is a well-defined genetic program. Loss of protein homeostasis (proteostasis) is one of the key hallmarks of aging. Indeed, proteostasis pathways, such as the heat shock response and aggregation of metastable proteins, are also controlled by thermosensory neurons in C. elegans. Prolonged heat stress is thought to play a critical role in the development of neurodegenerative protein misfolding diseases in humans. This review presents the latest evidence on how temperature coordinates proteostasis and aging. It also discusses how studies of poikilothermic organisms can be applied to vertebrates and provides new therapeutic strategies for human disease.

Aquatic Exercise and Mental Health: A Scoping Review

OBJECTIVES

The aims of this review were to 1) summarise the breadth and types of research regarding the impact of aquatic exercise on mental health completed to date, 2) provide a clear indication of the intervention type, volume, measurement tools used, and populations best served in relation to this activity and its effectiveness and 3) to identify domains within the literature that can be developed so recommendations can be made for future investigations.

METHOD

A scoping review was performed under the PRISMA guidelines. A systematic search of Pubmed, SPORTDiscus, PsycInfo and Google Scholar databases was conducted. Studies observing the effect of aquatic exercises on mental health and related parameters were considered for inclusion. The data from the selected studies were then extracted and analysed methodically.

PRIMARY CONDITIONS MEASURED

Depression, anxiety, mood, self-esteem, and psychological well-being were the primary mental states for which findings could be clearly extracted.

RESULTS

Of the 1635 articles that resulted from the search, 23 articles met all inclusion criteria. Of these, 12 were randomised controlled trials. Cumulatively, the findings of this review trend towards aquatic exercise being effective in generating positive changes in mental health.

CONCLUSION

Aquatic exercise, specifically winter swimming, leisure swimming, competitive swimming and aquatic aerobics, can be a promising conservative therapy for mental health management. However, it is recommended that further research be conducted to solidify these findings and establish the long-term effects of this intervention on mental health.

The Effect of Extreme Cold on Complete Blood Count and Biochemical Indicators: A Case Study

Regular exposure to a cold factor-cold water swimming or ice swimming and cold air-results in an increased tolerance to cold due to numerous adaptive mechanisms in humans. Due to the lack of scientific reports on the effects of extremely low outdoor temperatures on the functioning of the human circulatory system, the aim of this study was to evaluate complete blood count and biochemical blood indices in multiple Guinness world record holder Valerjan Romanovski, who was exposed to extremely cold environment from -5 °C to -37 °C for 50 days in Rovaniemi (a city in northern Finland). Valerjan Romanovski proved that humans can function in extremely cold temperatures. Blood from the subject was collected before and after the expedition. The subject was found to have abnormalities for the following blood indices: testosterone increases by 60.14%, RBC decreases by 4.01%, HGB decreases by 3.47%, WBC decreases by 21.53%, neutrocytes decrease by 17.31%, PDW increases by 5.31%, AspAT increases by 52.81%, AlAT increase by 68.75%, CK increases by 8.61%, total cholesterol decreases by 5.88%, HDL increases by 28.18%. Percentage changes in other complete blood count and biochemical indices were within standard limits. Long-term exposure of the subject (50 days) to extreme cold stress had no noticeable negative effect on daily functioning.

Assessment of morphological, biochemical and rheological blood indicators in men after a 24-hour stay in a thermo-climatic chamber -50°C

Purpose: The aim of the study was to evaluate morphological, biochemical, and rheological blood indicators in men staying in a cryochamber at a temperature of -50°C for 24 hours. In 2018, a scientific-survival project ‘Taming the Frost’ was conducted at the Technoclimatic Research and Working Machines Laboratory of the Cracow University of Technology, under the scientific patronage of the Rector of the Cracow University of Technology, Prof. Jan Kazior, PhD, as well as the Rector of the University of Physical Education in Krakow, the late Prof. Aleksander Tyka, PhD, and the Vice-Rector for Science, Prof. Anna Marchewka, PhD. Material and methods: The blood for the tests was collected from an ulnar vein in fasting participants by a qualified nurse, in the morning, before entering the cryochamber and after 24 hours, i.e. on leaving the cryochamber. Morphological, biochemical, and rheological blood indicators were evaluated. The study group of the scientific-survival project ‘Taming the Frost’ involved men (n=6) who stayed in a cryochamber at a temperature of -50°C for 24 hours. For each participant, a 5-ml blood sample was placed in a tube (BD Vacutainer) with EDTA K2 anticoagulant for blood morphology and blood rheological evaluations in the Blood Physiology Laboratory of the Central Research and Development Laboratory, University of Physical Education in Krakow. Another 5-ml blood sample was placed in a Vacuette tube with a clotting activator for the remaining biochemical analyses in the Department of Clinical Biochemistry of the Krakow Branch of Maria Skłodowska-Curie National Research Institute of Oncology. Results: After leaving the cryochamber with a temperature of –50°C, the participants presented statistically significant increases in monocyte count and high-density lipoprotein and creatine kinase values, as well as decreases in IgA, total cholesterol, and triglycerides. In the assessment of blood rheological indicators, statistically significant increases in the elongation index at the shear stress of 0.30, 0.58, 1.13, and 2.19 Pa and decreases in the elongation index at the shear stress of 31.03 and 60.3 Pa were observed. For red cell aggregation indicators, a statistically significant increase in total aggregation time was reported. The other indicators exhibited a significance level of p>0.05. Conclusions: Staying in a cryochamber at a temperature of -50°C for 24 hours did not exert a negative impact on morphological, biochemical, or rheological blood indicators, which implies the subjects’ adaptation to the arranged conditions.

A Possible Preventive Role of Physically Active Lifestyle during the SARS-CoV-2 Pandemic; Might Regular Cold-Water Swimming and Exercise Reduce the Symptom Severity of COVID-19?

The objective of this study was to investigate the incidence and course of COVID-19 and the risk of an upper respiratory tract infection in a group of people with physically active lifestyles. Data were collected anonymously using an online survey platform during December 2020. The age of participants ranged from 18 to 65 years. Out of 2343 participants, 11.5% overcame COVID-19 infection. Relative to the control group (CTRL), physically active, cold-water swimmers (PACW) did not exhibit a lower risk of incidence for COVID-19 (RR 1.074, CI 95% (0.710–1.625). However, PACW had a higher chance of having an asymptomatic course of COVID-19 (RR 2.321, CI 95% (0.836–6.442); p < 0.05) and a higher chance of only having an acute respiratory infection once or less per year than CTRL (RR 1.923, CI 95% (1.1641–2.253); p < 0.01). Furthermore, PACW exhibited a lower incidence of acute respiratory infection occurring more than twice per year (RR 0.258, CI 95% (0.138–0.483); p < 0.01). Cold-water swimming and physical activity may not lessen the risk of COVID-19 in recreational athletes. However, a physically active lifestyle might have a positive effect on the rate of incidence of acute respiratory infection and on the severity of COVID-19 symptoms.

Influence of Anthropometric Characteristics on Ice Swimming Performance-The IISA Ice Mile and Ice Km

Ice swimming following the rules of IISA (International Ice Swimming Association) is a recent sports discipline starting in 2009. Since then, hundreds of athletes have completed an Ice Mile or an Ice Km in water colder than 5 °C. This study aimed to expand our knowledge about swimmers completing an Ice Mile or an Ice Km regarding the influence of anthropometric characteristics (i.e., body mass, body height, and body mass index, BMI) on performance. We analyzed data from 957 swimmers in the Ice Km (590 men and 367 women) and 585 swimmers in the Ice Mile (334 men and 251 women). No differences were found for anthropometric characteristics between swimmers completing an Ice Mile and an Ice Km although water temperatures and wind chill were lower in the Ice Km than in the Ice Mile. Men were faster than women in both the Ice Mile and Ice Km. Swimming speed decreased significantly with increasing age, body mass, and BMI in both women and men in both the Ice Mile and Ice Km. Body height was positively correlated to swimming speed in women in the Ice Km. Air temperature was significantly and negatively related to swimming speed in the Ice Km but not in the Ice Mile. Water temperature was not associated with swimming speed in men in both the Ice Mile and Ice Km but significantly and negatively in women in Ice Km. In summary, swimmers intending to complete an Ice Mile or an Ice Km do not need to have a high body mass and/or a high BMI to swim these distances fast.

Acute increase in arterial stiffness after swimming in cooler water

Cold stimuli increase arterial stiffness, but it has not been explored whether arterial stiffness increases after swimming in cooler water. To investigate the effects of water temperature on changes in arterial stiffness after swimming, 13 men participated in three trials of 20-min swimming in 25 and 30°C water (S25 and S30, respectively) and sitting at poolside (CON) in random order. There were no significant differences between the S25 and S30 trials in mean swimming distance (719 vs. 722 m) and heart rate reserve during swimming (63% vs. 63%). Sublingual temperature was lower after swimming in 25°C water versus before swimming. Aortic pulse wave velocity (aortic PWV, an index of central arterial stiffness based on applanation tonometry) and brachial-ankle pulse wave velocity (baPWV, an index of systemic arterial stiffness based on air plethysmography) were higher 30 min after versus before swimming in 25°C water. Aortic PWV recovered to pre-swimming levels by 60 min after swimming in 25°C water, but baPWV was higher even at 60 min after swimming. PWVs did not change in the CON and S30 trials. Systemic vascular resistance based on Doppler ultrasonography did not change, but forearm vascular resistance based on strain-gauge plethysmography was higher 30 and 60 min after swimming in 25°C water. Heart rate was higher, but stroke volume was lower 30 min after swimming in 25°C water, resulting in no detectable change in cardiac output. In conclusion, arterial stiffness increases acutely after moderate-intensity swimming in cooler water.

Concentrations of Ca, Mg, P, Prostaglandin E2 in Bones and Parathyroid Hormone; 1,25-dihydroxyvitamin D3; 17-β-estradiol; Testosterone and Somatotropin in Plasma of Aging Rats Subjected to Physical Training in Cold Water

Exposure to low temperatures can be considered a stressor, which when applied for a specific time can lead to adaptive reactions. In our study we hypothesized that cold, when applied to the entire body, may be a factor that positively modifies the aging process of bones by improving the mechanisms related to the body's mineral balance. Taking the above into account, the aim of the study was to determine the concentration of calcium (Ca), magnesium (Mg), and phosphorus (P) in bones, and to examine bone density and concentrations of the key hormones for bone metabolism, namely parathyroid hormone (PTH), somatotropin (GH), 1,25-dihydroxyvitamin D3, 17-β estradiol, testosterone (T) in plasma, and prostaglandin E2 (PGE2) in the bone of aging rats subjected to physical training in cold water. The animals in the experiment were subjected to a series of swimming sessions for nine weeks. Study group animals (male and female respectively) performed swimming training in cold water at 5 ± 2 °C and in water with thermal comfort temperature (36 ± 2 °C). Control animals were kept in a sedentary condition. Immersion in cold water affects bone mineral metabolism in aging rats by changing the concentration of Ca, Mg, and P in the bone, altering bone mineral density and the concentration of key hormones involved in the regulation of bone mineral metabolism. The effect of cold-water immersion may be gender-dependent. In females, it decreases Ca and Mg content in bones while increasing bone density and 17-β estradiol and 1,25-dihydroxyvitamin D3 levels, and with a longer perspective in aging animals may be positive not only for bone health but also other estrogen-dependent tissues. In males, cold water swimming decreased PTH and PGE2 which resulted in a decrease in phosphorus content in bones (with no effect on bone density), an increase in 1,25-dihydroxyvitamin D3, and increase in T and GH, and may have positive consequences especially in bones and muscle tissue for the prevention of elderly sarcopenia.