[Objectives] The aim of this study was to evaluate the changes in serum brain-derived neurotrophic factor (BDNF) concentrations during 15 min of combined hot bath and bicycle ergometer endurance exercise in healthy young men.  [Methods] The experiment was conducted in a parallel design. The subjects were 10 healthy men (aged 23.7±0.8 years). The experimental group performed a combination of head-out water immersion (HOI) at 40°C and bicycle ergometer exercise (40°C HOI-ex), while the control group performed only HOI at 40°C (40°C HOI). After 30 min of rest, 40°C HOI-ex or 40°C HOI was performed for 15 min, followed by a 30 min recovery period. During the experiment, heart rate, blood pressure, and core temperature (esophageal temperature) were continuously measured. Blood samples were collected at four time points: after rest, immediately after intervention, 15 min after recovery, and 30 min after recovery. Serum BDNF, P-selectin, platelet count, hemoglobin, hematocrit, plasma cortisol, and lactic acid were then measured.  [Results] A significant increase in serum BDNF concentrations was observed immediately after intervention and 15 min after recovery in the 40°C HOI-ex group compared with the values taken after resting. No changes in serum BDNF concentrations were observed in the 40°C HOI group. Core temperatures significantly increased immediately after intervention, 15 min after recovery, and 30 min after recovery compared with resting for both 40°C HOI-ex and 40°C HOI groups, with between-group differences. Platelet counts were unchanged in both 40°C HOI and 40°C HOI-ex groups. A significant increase in P-selectin was observed immediately after intervention and 15 min after recovery in the 40°C HOI-ex group compared with when at rest. No changes in P-selectin were observed in 40°C HOI.  [Discussion] The combination of hyperthermia and exercise can increase serum BDNF in a short time of 15 min by an additive effect, and the increase in serum BDNF in this study may be platelet-derived.

  [Objectives] The aim of this study was to evaluate the changes in serum brain-derived neurotrophic factor (BDNF) concentrations during 15 min of combined hot bath and bicycle ergometer endurance exercise in healthy young men.  [Methods] The experiment was conducted in a parallel design. The subjects were 10 healthy men (aged 23.7±0.8 years). The experimental group performed a combination of head-out water immersion (HOI) at 40°C and bicycle ergometer exercise (40°C HOI-ex), while the control group performed only HOI at 40°C (40°C HOI). After 30 min of rest, 40°C HOI-ex or 40°C HOI was performed for 15 min, followed by a 30 min recovery period. During the experiment, heart rate, blood pressure, and core temperature (esophageal temperature) were continuously measured. Blood samples were collected at four time points: after rest, immediately after intervention, 15 min after recovery, and 30 min after recovery. Serum BDNF, P-selectin, platelet count, hemoglobin, hematocrit, plasma cortisol, and lactic acid were then measured.  [Results] A significant increase in serum BDNF concentrations was observed immediately after intervention and 15 min after recovery in the 40°C HOI-ex group compared with the values taken after resting. No changes in serum BDNF concentrations were observed in the 40°C HOI group. Core temperatures significantly increased immediately after intervention, 15 min after recovery, and 30 min after recovery compared with resting for both 40°C HOI-ex and 40°C HOI groups, with between-group differences. Platelet counts were unchanged in both 40°C HOI and 40°C HOI-ex groups. A significant increase in P-selectin was observed immediately after intervention and 15 min after recovery in the 40°C HOI-ex group compared with when at rest. No changes in P-selectin were observed in 40°C HOI.  [Discussion] The combination of hyperthermia and exercise can increase serum BDNF in a short time of 15 min by an additive effect, and the increase in serum BDNF in this study may be platelet-derived.