title: Neck cooling and cognitive performance following exercise-induced hyperthermia.
abstract: OBJECTIVE
  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 °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 °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).
  
  
  CONCLUSIONS
  Exercise-induced hyperthermia improves working memory and alertness. Neck cooling may only enhance performance in tasks of higher complexity.
authors: Combat Protection and Performance Programme, Defence Medical and Environmental Research Institute, DSO National Laboratories, Singapore, Republic of Singapore, lkaiwei@dso.org.sg.
authors: Jason K W
authors: JK
authors: Lee
authors: Aldrich C H
authors: AC
authors: Koh
authors: Serene X T
authors: SX
authors: Koh
authors: Glen J X
authors: GJ
authors: Liu
authors: Amanda Q X
authors: AQ
authors: Nio
authors: Priscilla W P
authors: PW
authors: Fan
mesh_terms: D000328:Adult; D001831:Body Temperature; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood; D016022:Case-Control Studies; D003071:Cognition; D015444:Exercise; D006339:Heart Rate; D006801:Humans; D006979:Hyperthermia, Induced; D007036:Hypothermia, Induced; D008297:Male; D008568:Memory; D009333:Neck / Q000502:physiology*; D010101:Oxygen Consumption; D011597:Psychomotor Performance
chemical_list: D019208:Brain-Derived Neurotrophic Factor