Neck cooling and cognitive performance following exercise-induced hyperthermia

Purpose To assess the efficacy of neck cooling on cognitive performance following exertional hyperthermia. Methods Twelve healthy men completed two experimental trials [control (CON) and neck cooling collar (NCC)] in a counter-balanced design. They ran on a treadmill at 70 % VO2peak under warm and humid conditions (dry bulb temperature: 30.2 +/- 0.3 degrees C, relative humidity: 71 +/- 2 %) for 75 min or until volitional exhaustion. Gastrointestinal, neck and skin temperatures, heart rate and subjective ratings were assessed. Serum brain-derived neurotrophic factor (BDNF) levels were measured before and after each run. Cognitive performance comprising symbol digit matching, search and memory, digit span, choice reaction time and psychomotor vigilance test (PVT) were assessed before and after exercise. Results Mean gastrointestinal temperature was similar after exercise between trials (CON: 39.5 +/- 0.4 degrees C vs. NC: 39.6 +/- 0.3 degrees C; p = 0.15). Mean neck temperature was lowered in NCC compared to CON after the run (36.4 +/- 1.6 degrees C vs. NCC: 26.0 +/- 0.3 degrees C; p < 0.001). Exercise-induced hyperthermia improved mean reaction time in the symbol digit matching test (-134 +/- 154 ms; p < 0.05) and the PVT (-18 +/- 30 ms; p < 0.05). Maximum span was increased in the digit span test (1 +/- 2; p < 0.05). Application of NCC reduced the number of search errors made in level 3 of the search and memory test (p < 0.05). Mean serum BDNF levels were increased following exercise-induced hyperthermia in both trials (p < 0.05). Conclusion Exercise-induced hyperthermia improves working memory and alertness. Neck cooling may only enhance performance in tasks of higher complexity.