The influence of acclimatization on stress hormone concentration in serum during heat stress.

This study was aimed to examine the influence of acclimatization on the change of concentration of stress hormones in men's serum exposed to heat stress during physical training. The study included a total of 40 men, aged 19-21 years, divided randomly into four groups: CTRL group: control, exposed to the Exercise Tolerance Testing in comfortable conditions; O group: exposed to Exercise Tolerance Testing in a warm environment; P group: exposed to passive acclimation to heat for 10 days, followed by Exercise Tolerance Testing in a warm environment; A group: exposed to active acclimation to heat for 10 days, followed by Exercise Tolerance Testing in a warm environment. All participants were tested for thermoregulation and acclimatization, skin and tympanic temperature, heart rate (HR), hormonal status and sweating. The mean skin temperature was the lowest in the control group of subjects exposed to physical exertion under comfortable conditions, and at each point of measurement it was statistically significantly different from that of the other study groups (p < 0.001). Sweating intensity was statistically significantly the lowest in the CTRL group (0.32 ± 0.04 l/m2/h; p < 0.001), compared to all other groups. Cortisol was significantly altered in O group (632.2 ± 92.3; 467.2 ± 89.7), testosterone levels were significantly altered in P (19.2 ± 9.3; 16.4 ± 7.3) and in A groups (22.1 ± 12.4; 14.9 ± 9.9), while prolactin was changed in O (392.1 ± 51.3; 181.4 ± 42.3), P (595.1 ± 191.1; 191.2 ± 52.5), and A group (407.4 ± 189.3; 173.4 ± 43.9) after the experimental period. The impact of acclimatization on hormonal indicators emphasizes its importance in the response of the endocrine system of soldiers to perform military activities in warm climates.

Lactobacillus helveticus Lafti L10 Supplementation Modulates Mucosal and Humoral Immunity in Elite Athletes: A Randomized, Double-Blind, Placebo-Controlled Trial.

Michalickova, DM, Kostic-Vucicevic, MM, Vukasinovic-Vesic, MD, Stojmenovic, TB, Dikic, NV, Andjelkovic, MS, Djordjevic, BI, Tanaskovic, BP, and Minic, RD. Lactobacillus helveticus Lafti L10 supplementation modulates mucosal and humoral immunity in elite athletes: a randomized, double-blind, placebo-controlled trial. J Strength Cond Res 31(1): 62-70, 2017-To test the influence of probiotic supplementation on humoral immune response, a double-blind, placebo-controlled trial was conducted. Thirty athletes (24 males and 6 females, females: V[Combining Dot Above]O2max 38.2 ± 4.9 ml·kg·min, age 23.2 ± 1.4 years; males: V[Combining Dot Above]O2max 57.5 ± 9.2 ml·kg·min, age 24.0 ± 2.4 years, mean ± SD) were randomized either to the probiotic group (Lactobacillus helveticus Lafti L10, 2 × 10 colony-forming units) or to the placebo group. Serum and saliva samples were collected at the baseline and after 14 weeks. Total and specific antibacterial antibody levels of IgM, IgG, and IgA classes were determined for different bacteria in the serum, and in saliva, total and specific antibacterial IgA levels were examined. Total IgM was elevated in both probiotic (18%, 15-20%; mean, 90% confidence interval; p = 0.02) and placebo group (35%, 22-47%; p = 0.02), without observed differences in changes between the groups. No significant changes in IgM levels specific for tested bacteria were found. Total IgG level was constant in both groups. A significant (16%, -2.8 to 35%, p = 0.04) reduction of anti-Enterococcus faecalis IgG was noted in the placebo group, in comparison with the probiotic group. There was a substantial decrease in total IgA level in the placebo group, when measured either in serum (15%, 12-18%, p = 0.04) or in saliva (35%, -1.4 to 53%, p = 0.03). Significantly reduced levels of serum anti-lactic acid bacteria IgA antibodies in the placebo group compared with the probiotic group were detected for Lactobacillus rhamnosus LA68 (24%, 5.8-42%, p = 0.02) and for L. rhamnosus LB64 (15%, 2.7-27%, p = 0.02). Probiotic administration could have beneficial effects on systemic humoral and mucosal immune responses.

Sweat rate and fluid intake in young elite basketball players on the FIBA Europe U20 Championship.

BACKGROUND/AIM: Previous investigations in many sports indicated that continued exercise, especially in hot environments, can cause high sweat rate and huge water and electrolyte losses, thus impairing the performance of athletes. Most these studies were conducted during training sessions, but rarely during an official competition. Therefore, the aim of our study was to determine pre- and post-competition hydration, fluid intake and sweat loss of young elite basketball players during the FIBA Europe U20 Championship. METHODS: The study included 96 basketball male players, (19 ± 0.79 years) of eight national teams. Ambient temperature was 30 ± 2°C, humidity 55 ± 4% and the mean playing time in game 18.8 ± 10.5 min. The following parameters related to hydration status were measured: fluid intake, urine output, sweat rate, percent of dehydration, urine parameters (specific gravity, color and osmolarity), body mass and body surface area. RESULTS: We found that the mean fluid intake was 1.79 ± 0.8 L/h, sweat rate 2.7 ± 0.9 L/h, urine output 55 ± 61 mL and the percentage of dehydration 0.99 ± 0.7%. According to urine osmolarity more than 75% of players were dehydrated before the game and the process continued during the game. The difference in body mass (0.9 ± 0.7 kg) before and after the game was statistically significant. There were statistically significant correlations between the sweat rate and fluid intake, urine osmolarity, body mass loss, body surface area and percentage of dehydration. Fluid intake correlated with the percentage of dehydration, body mass loss, urine specific gravity and urine color. The sweat rate, which varied between the teams, was the highest for centers when this parameter was calculated on the effective time in game. CONCLUSION: Most of the athletes start competition dehydrated, fail to compensate sweat loss during the game and continue to be dehydrated, regardless what kind of drink was used. These results suggest that hydration strategies must be carefully taken into account, not only by the players, but also by the coaches and the team doctors.

The effects of acclimatization on blood clotting parameters in exertional heat stress.

BACKGROUND/AIM: Exertional heat stress is a common problem in military services. Considering the coagulation abnormalities are of major importance in development of severe heat stroke, we wanted to examine changes in hemostatic parameters in soldiers during exertional heat stress test as well as the effects of a 10-day passive or active acclimatization in a climatic chamber. METHODS: A total of 40 male soldiers with high aerobic capacity performed exertional heat stress test (EHST) either in cool [20 degrees C, 16 degrees C wet bulb globe temperature (WBGT)], or hot (40 degrees C, 29 degrees C, (WBGT) environment, unacclimatized (U) or after 10 days of passive (P) or active (A) acclimatization. Physiological strain was measured by tympanic temperatures (Tty) and heart rates (HR). Platelet count (PC), antithrombin III (AT), and prothrombin time (PT) were assessed in blood samples collected before and immediately after the EHST. RESULT: EHST in hot conditions induced physiological heat stress (increase in Tty and HR), with a significant increase in prothrombin time in the groups U and A. Platelet counts were significantly higher after the EHST compared to the basic levels in all the investigated groups, regardless environmental conditions and acclimatization state. Antithrombin levels were not affected by EHST whatsoever. CONCLUSION: In the trained soldiers, physiological heat stress caused mild changes in some serum parameters of blood clotting such as prothrombin time, while others such as antithrombin levels were not affected. Platelet counts were increased after EHST in all groups. A 10-day passive or active acclimatization in climatic chamber showed no effect on parameters investigated.