Neck cooling and cognitive performance following exercise-induced hyperthermia
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To assess the efficacy of neck cooling on cognitive performance following exertional hyperthermia.
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 °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.
Mean gastrointestinal temperature was similar after exercise between trials (CON: 39.5 ± 0.4 °C vs. NCC: 39.6 ± 0.3 °C; p = 0.15). Mean neck temperature was lowered in NCC compared to CON after the run (36.4 ± 1.6 °C vs. NCC: 26.0 ± 0.3 °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).
Exercise-induced hyperthermia improves working memory and alertness. Neck cooling may only enhance performance in tasks of higher complexity.
KeywordsHyperthermia Perceptual heat strain Short-term memory Working memory alertness Neurotrophin S100B
Neck cooling collar
Brain-derived neurotrophic factor
Psychomotor vigilance test
S100 calcium binding protein B
Peak aerobic capacity
Rating of perceived exertion
Rating of thermal sensation
Swedish performance evaluation system
Tropomyosin receptor kinase B
The authors express their gratitude to Dr. Christopher Tyler for his advice on the neck collar and Ms. Lydia Law, Dr. Frederick Tey and Ms. Tan Ying Ying for their inputs on the selection of cognitive tests. We also like to thank Ms. Yvonne Yeo, Ms. Teo Ya Shi, Ms. Jacinta Yeo and Mr. David Fun for their assistance during data collection. The authors would also like to thank all participants for their commitment to the study. The study is funded by DSO National Laboratories, Singapore, and the National University of Singapore.
Conflict of interest
All authors declare they have no conflict of interest.
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