The Effects Of Endurance Exercise Combined With High-Temperature Head-Out Water Immersion On Serum Concentration Of Brain-Derived Neurotrophic Factor In Healthy Young Men

Objectives To evaluate acute changes in serum brain-derived neurotrophic factor (BDNF) concentration following combined endurance exercise and heat stress through head-out water immersion (HOI). Setting Observational study with crossover design. Methods Ten healthy young male participants performed HOI at 40 degrees C (40 degrees C HOI) or continuous cycling at 60% of maximal oxygen uptake while immersed in 40 degrees C (40 degrees C HOI-ex) or 23 degrees C water (23 degrees C HOI-ex) for 15 min. Serum BDNF, cortisol and lactate concentrations, and core temperature (T-core) were measured pre, immediately post, and 15 and 30 min post-immersion. Results BDNF concentration increased immediately and 15 min after 40 degrees C HOI-ex, but not after 40 degrees C or 23 degrees C HOI-ex. No changes in T-core concentration were observed during 23 degrees C HOI-ex (Pre; 37.3 degrees C +/- 0.3 degrees C, Post; 37.8 degrees C +/- 0.2 degrees C, Post 15; 37.4 degrees C +/- 0.3 degrees C, Post 30; 37.2 degrees C +/- 0.2 degrees C). T-core increased significantly post, post 15, and post 30 min of 40 degrees C HOI (Pre; 37.1 degrees C +/- 0.4 degrees C, Post; 38.8 degrees C +/- 0.5 degrees C, Post 15; 37.9 degrees C +/- 0.4 degrees C, Post 30; 37.9 degrees C +/- 0.2 degrees C) and 40 degrees C HOI-ex (Pre; 37.2 degrees C +/- 0.2 degrees C, Post; 40.2 degrees C +/- 0.7 degrees C, Post 15; 38.9 degrees C +/- 0.5 degrees C, Post 30; 38.3 degrees C +/- 0.5 degrees C). T-core was higher in 40 degrees C HOI-ex compared with 40 degrees C HOI and 23 degrees C HOI-ex immediately post and post 15 min. Plasma lactate and cortisol were significantly higher in 40 degrees C HOI-ex compared with 40 degrees C HOI and 23 degrees C HOI-ex after immersion (p = 0.001). Conclusion While 15 min HOI alone or thermoneutral exercise do not increase BDNF concentration, both combined may form a time-efficient strategy to acutely elevate BDNF.