Should carbohydrate concentration of a sports drink be less than 8% during exercise in the heat?
Our purpose was to determine if sports drinks with 6 and 8% CHO differentially affect physiological responses or run performance in the heat. Ten men ran 32 km while ingesting: placebo (P), 6% carbohydrate-electrolyte (CE6), and 8% carbohydrate-electrolyte (CE8). At 15 km, a 250 mL drink labeled with deuterium oxide (D2O) was ingested. Blood glucose and respiratory exchange ratio were significantly higher (P < 0.05) for CE6 and CE8 compared to P. Rectal temperature (T(re)) at 32 km was higher for CE8 (40.1 +/- 0.2 degrees C) compared to P (39.5 +/- 0.2 degrees C) but similar to CE6 (39.8 +/- 0.2 degrees C). D2O accumulation was not different among drink trials. Run performance was 8% faster for CE8 (1062 +/- 31 s) compared to P (1154 +/- 56 s) and similar to CE6 (1078 +/- 33 s). Confirming the ACSM Position Stand, 8% CE are acceptable during exercise in the heat and attenuate the decline in performance.
Millard-Stafford
Mindy L
ML
Exercise Physiology Laboratory, School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA 30332-0356, USA.
Sparling
Phillip B
PB
Rosskopf
Linda B
LB
Snow
Teresa K
TK
D000328:Adult; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism*; D018592:Cross-Over Studies; D017666:Deuterium Oxide; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004573:Electrolytes / Q000008:administration & dosage / Q000494:pharmacology; D005440:Fluid Therapy; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009751:Nutritional Requirements; D012420:Running / Q000502:physiology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004573:Electrolytes; D017666:Deuterium Oxide