Comparison of the Effects of Cryotherapy and Swimming in Cold Water – Winter Swimming on Chosen Morphological and Biochemical Blood Indices and Factors Released by Brown Adipose Tissue

Introduction: Whole-body cryotherapy and winter swimming are applied to induce physiological, organ-related, and systemic defence responses that are beneficial and effective in maintaining or restoring human body homeostasis. Purpose: The aim of the study was to evaluate blood morphological and biochemical indicators in men and women exposed to whole-body cryotherapy and winter swimming. Material and methods: From all participants (n=70) before starting 20 whole-body cryotherapy sessions and after completing the 20 whole-body cryotherapy sessions (woman n=15, men n=15), at the beginning of the winter swimming season (November) and at the end of the winter swimming season (April) (woman n=15, men n=15), and in the control group (woman n=10, men n=10), fasting blood samples were collected from an ulnar vein into vacuum tubes. Blood morphological and biochemical indicators and brown adipose tissue were determined in the Blood Physiology Department of the Central Research and Development Laboratory at the University of Physical Education in Krakow and in the Department of Analytics and Clinical Biochemistry of the Krakow Branch of Maria Sklodowska-Curie National Research Institute of Oncology. Results: In both sexes included in the study, both whole-body cryotherapy and winter swimming induce changes in selected peripheral blood morphological and biochemical indicators, mainly in the blood count, proteinogram, and chloride concentrations. The increase in the brown adipose tissue-released fibroblast growth factor-21 (FGF-21) under the influence of whole-body cryotherapy occurs in females. In contrast, no statistically significant changes were found for Nrg4. Both whole-body cryotherapy and winter swimming result in decreased values of red blood cells, haemoglobin, and iron, with sex-dependent variation. Conclusions: Cold in the form of systemic cryotherapy, similarly to winter baths, affects changes in blood morphological and biochemical parameters, while the release of FGF21 in brown adipose tissue was noted only after systemic cryotherapy.