Leukocyte subset responses during exercise under heat stress with carbohydrate or water intake.
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.
Lim
Chin Leong
CL
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
Byrne
Christopher
C
Chew
Serena A N
SA
Mackinnon
Laurel T
LT
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
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D014867:Water; D006854:Hydrocortisone