Estresse térmico e respostas fisiológicas em atletas de jiu-jitsu brasileiro submetidos a lutas simuladas em ambiente quente

Abstract

Objective: This study aims to evaluate the thermoregulatory and physiological responses during and after simulated Brazilian jiu-jitsu fights in extreme environmental. Materials and Methods: For this purpose, a descriptive and observational study was carried out with experienced male Brazilian jiu-jitsu adults who compete regularly in regional and national competitions. The sampling was non-probabilistic for convenience with twelve athletes at the age 28±3 years, body mass 84.0± 10.0 kg, height 173.0 ±6.0 cm, body mass index 27.6 ±3.7 Kg/ m2

, bodyfat % 13.5 ± 4.9, with a weekly training frequency of at least three days and duration one and a half hours. The fights took place in a covered environment during the night, with ambient temperature (AT) of 29.3 ± 0.5oC and relative humidity in air (RH) of 75.9 ± 1.1%. Heart rate, lactate, and internal and skin temperature data were collected prior to commencing the simulated fights (baseline), immediately after the end of each fight and prior to the start of the next fight. Data are presented as average, standard deviation of the mean, minimum and maximum values. The Shapiro-Wilk test was used to test the normality of the data and the Brown-Forsythe test was used for homoscedasticity. One-way

ANOVA test was used for comparing the baseline, during and post-protocol and post- hoc Student-Newman-Keuls Method, when necessary. A P <0.05 was adopted.

Results: Participants completed the first, second, third and fourth simulated fights with a heart rate of 169 ± 8, 169 ± 11, 166 ± 10 and 160 ± 13 bpm respectively and lactate 10.4 ± 3.9, 10.4 ± 4.1, 9.5 ± 3.2 and 9.9 ± 4.0 mmol / l respectively. The internal temperature increased (P< 0.001) from 36.9 ± 0.8 ° C (rest) to 38.1 ± 0.6 °C in the first fight, and then showing stable behavior up to the end of the fourth fight. In addition, the average temperature of the head (34.0 ± 1.0 °C) and skin (34.0 ± 1.0 °C) was stable throughout the protocol. There was no variance in the handgrip strength. At the end of the protocol, participants had a dehydration rate of 1.6% ± 0.9% with a total sweating value of 2.2 ± 0.6 liters. Pre- and post-protocol urine specific density was 1010,50 ± 6,88 g / mL and 1019.00 ± 10.50 g / mL, respectively. Conclusion: The thermoregulatory mechanisms were enough to maintain thermal control during simulated Brazilian Jiu-Jitsu fights. Since evaporation of sweat is the main mechanism of thermal regulation in hot environments, it led athletes to significant dehydration, which probably interfered with the intensity of the efforts during the combats, consequently interfering with lactate production, heart rate and hand grip strength. To improve fighting performance, it is important for JJB athletes to strive to start their activities in a hydrated state and to adopt more efficient rehydration strategies during and after training.