Background and Study Aim. Continuously increasing the volume and intensity of the training sessions often leads to overtraining. It has been demonstrated that glutathione supplementation might improve the aerobic metabolism in skeletal muscle and reduce exercise-induced muscle fatigue. The aim of the study was to assess the effect of glutathione supplementation on fatigue, recovery processes, and competitive results of elite swimmers during a six-week training period. Material and Methods. Twenty-four elite swimmers (10 women and 14 men) from the Bulgarian national swimming team, with a mean age of 18.7±3.78 years, took part in this double-blind placebo control study. The swimmers from the experimental group were supplemented once a day with a capsule of 250mg glutathione, whilst the swimmers from the control group took a placebo once a day. The urine concentration levels of cortisol and cortisone, as well as the degree of overtraining, were evaluated on the 1st(T1), 14th(T2), 28th(T3), and 42nd(T4) days. Anthropometric measurements and a nutritional assessment were performed at T1 and T4. Results. The swimmers showed a gradual decrease of cortisol and cortisone during the study, with significantly lower concentrations in the experimental vs the control group at T4 (19.4 vs 42.5 ng/mL, p < 0.05). At the end of the study, the swimmers from the experimental group showed improvements in their time in 41 out of the 43 swimming events, whilst those from the control group had significantly smaller improvements (-1.66 vs -0.97%, p < 0.05). Conclusions. In conclusion, glutathione supplementation at a dose of 250mg/day for six weeks improves the adaptation of elite swimmers towards training schedules, which is likely to lead to better sports results.

Aim. Optimal balance between training intensity and recovery is of particular importance for elite swimmers in order to improve their results. The aim of this study was to record the dyna­mics of training distress, performance, and excretion of cortisol and cortisone in urine during six weeks of training in elite swimmers. Materials and Methods. Twenty-four participants (10 women and 14 men) from the national swimming team of Bulgaria took part in this study, with an average age of 18.7 ± 3.78 years. Training distress (TDS) and urine concentration of cortisol and cortisone were evaluated every two weeks. In total, the measurements were taken on the 1-st (T1), 14-th (T2), 28-th (T3) and 42-nd days (T4). Anthropometric measurements were also taken at T1 and T4, and body fat percentage and muscle mass percentage were calculated by skinfold methods. Results. The TDS score at T4 (6.92 ±7.15) was significantly lower than this at T1 (14.96 ± 10.63) and T2 (15.21 ± 12.44). The concentrations of cortisol at T3 (35.9 ± 47.7) and T4 (35.0 ± 24.2) were also significantly lower than that registered at T1 (82.7 ± 62.8). The concentration of cortisone did not show any significant differences across T1 to T4, but the sum of cortisol and cortisone urine concentration was significantly lower in T3 and T4 vs T1. Conclusion. The significantly reduced cortisol concentration in urine in T4, as well as the sum of the concentrations of cortisol and cortisone, were in line with the reduction of the TDS score in T4.

Introduction: The primary objective of this study was to assess cardiovascular risk among members of the Bulgarian Antarctic expedition and identify strategies for risk reduction. The combination of intense physical and psychological stress, prolonged cold exposure, isolation, and challenging travel conditions contributes to an increased risk of cardiovascular disease, especially given the participants’ mature age, which is a key factor in greater cardiovascular disease susceptibility. Methods: This research included 29 participants (23 males and 6 females) with average ages of 43.0±8.00 y for the males and 45.5±11.31 y for the females. All participants spent 30 d in Antarctica. They were subjected to comprehensive assessments, including anthropometric measurements, physiologic evaluations, and biochemical analyses both before departure and shortly after return. The updated SCORE2 algorithm following the European guidelines was used to estimate the 10-y cardiovascular event risk, which factored in age, blood pressure, lipid profile, and smoking status. All participants underwent the veloergometer stress test under electrocardiographic control twice, before and after the expedition. Results: The results indicated that while most participants fell into the moderate-risk category, some of them exhibited elevated-risk profiles, primarily influenced by obesity, cholesterol levels, systolic blood pressure, and serum ferritin levels. No critical cardiovascular events were reported during the expedition. Conclusion: This study highlights the importance of pre-expedition screening, including the conduct of an exercise stress test, targeted risk-factor management, and continuous monitoring for safeguarding the health and physiologic resilience of Antarctic expedition participants, ultimately underscoring the feasibility and necessity of cardiovascular prevention strategies in extreme environments.

Background: The number of people working in Antarctica has steadily increased. Identifying the characteristic functional changes in polar expeditioners can help preserve health, enhance work capacity, and improve adaptive potential in specific environments. Objective: This study aimed to evaluate the impact of a short-term (30-day) expedition in Antarctica on selected physiological parameters among expedition participants, depending on their body mass index (BMI). Methods: Thirty-four expedition members, divided into 3 BMI groups, were examined before and after a one-month stay in Antarctica. The assessments included anthropometry, body composition analysis, blood pressure (BP) evaluation, and a cycle ergometer stress test, performed up to 85% of predicted maximal heart rate (PWC85%) with gas analyses and heart rate measured at the 3rd minute after exercise completion (HR3’), used as an indicator of cardiovascular recovery. Results: After the expedition, the participants with normal weight showed a modest but significant increase in body weight and BMI, and non-significant increases in fat mass (FM) and muscle mass (MM); cardiovascular recovery and physical working capacity were improved, while aerobic fitness remained unchanged. In the overweight group, post-expedition body weight and BMI did not change significantly, although small reductions in FM and improvements in MM, BP, PWC85%, and HR3’ were observed. Returning, the participants with obesity demonstrated non-significant improvements in body composition and modest declines in BP, together with a significant improvement in HR3’. Conclusions: Comparative analysis revealed significant differences in post-expedition changes in several functional parameters between the normal-weight and obese groups. Overall, the Antarctic expedition elicited beneficial cardiovascular and functional adaptations, particularly among overweight individuals, while body composition and aerobic capacity remained unchanged across all groups.

Antarctic expeditions expose individuals to multiple and interacting stressors that may affect physiological regulation, sleep, and physical activity. This study investigated physiological responses in 28 male participants during the 34th Bulgarian Antarctic Expedition, who spent 30 days at the Antarctic research base. Physical activity and sleep duration were continuously monitored using three-dimensional inertial sensors. Salivary biomarkers of physiological responses associated with stress, cortisol, K⁺, Na⁺, the K⁺/Na⁺ ratio, total protein, and α-amylase activity, were measured before the expedition, weekly during deployment, and after return. Sleep duration increased significantly during Weeks 2 and 3 compared to Week 1. Light -intensity activity predominated over moderate-intensity activity and declined significantly over the monitoring period, whereas moderate-intensity activity decreased significantly during Week 3 compared with Week 1. Cortisol concentrations were significantly lower after return than during the pre-expedition period. Salivary K⁺ concentrations increased significantly during the Week 2 and subsequently decreased significantly after return, whereas Na⁺ concentrations remained stable throughout the mission but decreased after return. The K⁺/Na⁺ ratio declined significantly during the Weeks 2 and 3 and after expedition. Total salivary protein concentration and α-amylase activity increased at the Weeks 4 and 3, respectively, and both approached baseline following the participants’ return. The longitudinal changes in salivary biomarkers, together with alterations in physical activity and sleep duration, indicate dynamic physiological responses during and after Antarctic expedition. This minimally invasive, integrated approach may support further research on individual patterns of physiological adjustment and early deviations from adaptation, and may contribute to the development of personalized health monitoring strategies and timely preventive interventions during future Antarctic and other missions in extreme environments.