title: The influence of a mild thermal challenge and severe hypoxia on exercise performance and serum BDNF.
abstract: OBJECTIVE
  To examine the isolated and combined effects of severe hypoxia and a mild thermal challenge on performance, physiological measures, cognition, and serum brain-derived neurotrophic factor (BDNF).
  
  
  METHODS
  Nine trained male athletes (age: 23 ± 3 years; W max: 333 ± 45 W) completed four experimental trials (CON: 15 °C/0 m, ALT: 15 °C/3800 m, TEMP: 25 °C/0 m, ALT + TEMP: 25 °C/3800 m) in a double blind, randomized, cross-over design. Subjects cycled for 30 min in a self-paced test starting at 75% W max, their goal was to 'perform as much work as possible in 30 min.' Power output, heart rate, blood lactate, pulse oximetry, core and skin temperature, thermal sensation, ratings of perceived exertion, reaction time (RT), and BDNF were assessed.
  
  
  RESULTS
  The amount of work produced in 30 min was reduced by temperature (F(1,8) = 7.1; p = 0.029; 360 ± 19 kJ in 15 °C; 344 ± 18 kJ in 25 °C) and altitude (F(1,8) = 94.2; p < 0.001; 427 ± 24 kJ at sea level; 277 ± 15 kJ at altitude), yet there was no interaction effect. Altitude increased mean RT (F(1,8) = 8.0; p = 0.022; 281.9 ± 9.4 ms at sea level; 289.3 ± 10.0 ms at altitude) and RT variability (F(1,8) = 8.5; p = 0.020; 44 ± 3 ms at sea level: 50 ± 4 ms at altitude). Exercise increased BDNF (F(1,8) = 15.2; p = 0.005; PRE: 21.8 ± 1.3 ng/mL; POST: 26.5 ± 2.1 ng/mL).
  
  
  CONCLUSIONS
  Exercise capacity was significantly reduced due to an increase in altitude (3800 m; -34.3%) or a 10 °C increase in ambient temperature (-3.2%). The combination of both stressors showed to be additive (-38.0 %). Altitude induced an increase in RT and RT variability presenting a deterioration in cognitive functioning during acute hypoxia. Exercise significantly increased BDNF, but no effect of altitude on the BDNF concentration was observed.
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Van Cutsem
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.|Vital Signs and Performance Monitoring, Royal Military Academy, Brussels, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Pattyn
authors.affiliation: Center for Aviation Medicine, Military Hospital Queen Astrid, Brussels, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Vissenaeken
authors.affiliation: Center for Aviation Medicine, Military Hospital Queen Astrid, Brussels, Belgium.
authors.forename: Gino
authors.initials: G
authors.lastname: Dhondt
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
authors.forename: Kevin
authors.initials: K
authors.lastname: De Pauw
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
authors.forename: Cajsa
authors.initials: C
authors.lastname: Tonoli
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.|School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Queensland, Australia.
authors.forename: Romain
authors.initials: R
authors.lastname: Meeusen
authors.affiliation: Department of Human Physiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium. bart.roelands@vub.ac.be.|Fund for Scientific Research Flanders (FWO), Brussels, Belgium. bart.roelands@vub.ac.be.
authors.forename: Bart
authors.initials: B
authors.lastname: Roelands
mesh_terms: D000328:Adult; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology*; D015308:Anaerobic Threshold; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise; D017079:Exercise Tolerance; D006358:Hot Temperature; D006801:Humans; D008297:Male; D011897:Random Allocation; D011930:Reaction Time
chemical_list: D019208:Brain-Derived Neurotrophic Factor
keywords: Altitude; Environmental temperature; Exercise; Reaction time