title: Two strategies for the acute response to cold exposure but one strategy for the response to heat stress.
abstract: OBJECTIVE
  The main aim of this study was to compare physiological and psychological reactions to heat stress between people who exhibited fast cooling (FC, n = 20) or slow cooling (SC; n = 20) responses to 14 °C cold water immersion.
  
  
  METHODS
  Forty healthy young men (19-25 years old) were recruited to this study based on their tolerance to cold exposure (FC versus SC). The heat stress was induced using immersion in bath water at 43-44 °C. Motor and cognitive performance, immune variables, markers of hypothalamic-pituitary-adrenal axis activity (i.e. stress hormone concentrations), and autonomic nervous system activity were monitored.
  
  
  RESULTS
  In the FC group, time to warm the body from a resting rectal temperature (Tre) of 37.1 ± 0.2 °C before warming to 39.5 °C was 63.7 ± 22.4 min. In the SC group, the time to warm the body from a Tre 37.1 ± 0.3 °C before warming to 39.5 °C was 67.2 ± 13.8 min (p > 0.05 between groups). The physiological stress index (PSI) after warming was 8.0 ± 0.6 and 8.2 ± 1.0 in the FC and SC groups, respectively (p > 0.05 between groups). During warming, the changes in subjective indicators of heat stress did not differ significantly between the FC (7.4 ± 0.5) and SC (7.1 ± 1.1) groups, respectively.
  
  
  CONCLUSIONS
  The increase in cortisol, epinephrine, norepinephrine, and corticosterone concentrations after passive body heating did not differ between the FC and SC groups. Heat stress did not change indicators of innate and specific immunity in the FC or the SC group. An interesting finding was that heat stress did not affect motor and cognitive function in either group, although central fatigue during 1-min maximal voluntary contraction increased after heat stress in both groups.
authors.affiliation: Sports Science and Innovation Institute, Lithuanian Sports University , Kaunas .
authors.forename: Marius
authors.initials: M
authors.lastname: Brazaitis
authors.forename: Nerijus
authors.initials: N
authors.lastname: Eimantas
authors.forename: Laura
authors.initials: L
authors.lastname: Daniuseviciute
authors.forename: Astra
authors.initials: A
authors.lastname: Vitkauskiene
authors.forename: Henrikas
authors.initials: H
authors.lastname: Paulauskas
authors.forename: Albertas
authors.initials: A
authors.lastname: Skurvydas
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D003071:Cognition / Q000502:physiology; D003080:Cold Temperature; D018882:Heat Stress Disorders / Q000503:physiopathology* / Q000523:psychology; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology; D010913:Pituitary-Adrenal System / Q000502:physiology; D013312:Stress, Physiological; D055815:Young Adult
keywords: Cold adaptation strategies; heat stress; immune system; motor and cognitive performance; stress indicators