Head-out immersion in hot water increases serum BDNF in healthy males

Abstract

The present findings suggested that the increase in BDNF during 20-min hot-HOI was induced by hyperthermia through enhanced production, rather than by changes in permeability of the blood-brain barrier (BBB), platelet clotting mechanisms or secretion from monocytes.

Exercise and circulating BDNF: Mechanisms of release and implications for the design of exercise interventions

“…A recent study provides exciting evidence for the possible contribution of the brain and/or vascular endothelial cells to circulating BDNF independent of exercise. Kojima et al (2017) found that 20 minutes of head-out immersion in hot water significantly increases serum BDNF, which supports previous findings that exercise performed in the heat results in significantly greater increases in serum BDNF compared to a normothermic environment (Goekint et al 2011, Lee et al 2014. These findings are especially compelling because serum BDNF increased without an accompanying increase in platelets, suggesting exclusive contribution from cellular sources (Watson 2005).…”

The Thermal Effects of Water Immersion on Health Outcomes: An Integrative Review

“…The number of measurements used to test the effects of dependent variables ranged from two to six. The study by Brunt et al [25] had the highest number of measurements (six), including one pre-test and five post-test measurements. Even in cases with a single experimental treatment, repeated (two or four) measurements were performed to investigate the short- and long-term effects of water immersion.…”

“…In the studies by Shimodozono et al [19], Bailey et al [20], and Hu et al [23], female subjects were allowed to participate in the experiment during the follicular phase of their menstrual cycle in order to control for the temperature changes due to the menstrual cycle, while middle-aged women were only enrolled if they were in the menopausal stage. In a study by Brunt et al [25], urinalysis was performed on female subjects during all experimental procedures to accurately identify their pregnancy status by assessing the level of human chorionic gonadotropin, a pregnancy hormone. In addition, other lifestyle factors, such as medication use, drinking status, smoking status, exercise status, caffeinated beverage intake, estrogen hormone therapy, and regular thermal therapy, were assessed in order to select a homogenous study population and control for the confounding effects on the treatment effect.…”

“…For example, in the study by Shimodozono et al [19], because a serum test was part of the post-test, the subjects were instructed to fast for 12 h prior to the experiment and only drink 300 ml of water on the day of the experiment. In the studies by Blunt et al [18,25], urine samples were analyzed to ensure that the first morning urine on the day of the experiment had a specific gravity ≤ 1.024 to reduce the risks associated with changes in the volume and composition of body fluids due to hydrotherapy. Subjects with a specific gravity of urine > 1.024 were instructed to drink 5 ml of water per kg body weight prior to immersion.…”

“…A total of seven articles mentioned the application of post-hoc treatment immediately after the experimental treatment, including the immediate removal of moisture after moving to an environment prepared for recovery from changes in body temperature (recovery chair, laboratory, and warm room). In the two studies by Brunt et al [18,25], the subjects were monitored until their rectal temperature reached 38.5 °C, while in the study by Herrera et al [22] that applied cold water immersion, the subjects were instructed not to apply friction to the area where the immersion was applied, in order to minimize tissue damage after the experimental treatment.…”