title: Leukocyte subset responses during exercise under heat stress with carbohydrate or water intake.
abstract: OBJECTIVE
  This study investigated leukocyte subset responses to moderate-intensity exercise under heat stress, with water (W) or carbohydrate (CHO) drink ingestion.
  
  
  METHODS
  In repeated trials, 13 soldiers consumed either a W or CHO drink during 3 h of walking at 4.4 km x h(-1) with a 5% gradient (15 min rest per hour) under heat stress (35 degrees C and 55% relative humidity). The soldiers wore combat uniforms and carried water bottles and dummy rifles and ammunition, altogether weighing about 11.5 +/- 1.0 kg.
  
  
  RESULTS
  Plasma glucose concentration was significantly higher with CHO than W ingestion during exercise (p < 0.01). There were no significant differences between W and CHO conditions in exercise performance, plasma cortisol concentration, heart rate, or core temperature. CHO ingestion significantly moderated the increases in leukocyte (83% in W, 28% in CHO; p < 0.001), monocyte (60% in W, 34% in CHO; p < 0.05), and granulocyte counts (120% in W, 30% in CHO; p < 0.001), but not in lymphocyte count (41% in W, 25% in CHO).
  
  
  CONCLUSIONS
  The increases in leukocyte and subset counts during moderate-intensity exercise under heat stress may be comparable to those observed during intense exercise in cool conditions. The response of immune cell counts is blunted by CHO intake during moderate-intensity exercise in the heat, and may not occur through the cortisol pathway.
authors.affiliation: Military Physiology Laboratory, Defence Medical and Environmental Research, DSO National Laboratories, 27 Medical Drive, #09-01, Singapore 117510, Republic of Singapore. limcl@dso.org.sg
authors.forename: Chin Leong
authors.initials: CL
authors.lastname: Lim
authors.forename: Christopher
authors.initials: C
authors.lastname: Byrne
authors.forename: Serena A N
authors.initials: SA
authors.lastname: Chew
authors.forename: Laurel T
authors.initials: LT
authors.lastname: Mackinnon
mesh_terms: D000328:Adult; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004327:Drinking Behavior; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D018882:Heat Stress Disorders; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007962:Leukocytes / Q000502:physiology*; D008297:Male; D014867:Water
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D014867:Water; D006854:Hydrocortisone