Carbohydrate-electrolyte replacement improves distance running performance in the heat

Med Sci Sports Exerc. 1992 Aug;24(8):934-40.


The effects of a 7% carbohydrate-electrolyte drink (CE) and an artificially sweetened placebo (P) on performance and physiological function were compared during a 40-km run in the heat. Eight highly trained male runners completed two runs on a measured outdoor course. The first 35 km of each run was performed at self-selected training pace and the last 5 km at race effort. Under a counterbalanced, double-blind design, subjects consumed 400 ml of either CE or P 30 min prior to exercise, and 250 ml every 5 km thereafter during the run. Rectal temperature, heart rate, rating of perceived exertion, sweat rate, and respiratory exchange ratio were similar during the run for CE and P. Serum Na+, K+, Cl-, total protein, osmolality, blood lactate, urea nitrogen, and % change in plasma volume were also similar for both drink conditions; however, blood glucose was significantly higher (P less than 0.01) with CE. Running performance in the last 5 km was significantly faster (P less than 0.03) during CE (21.9 min) compared with P (24.4 min). Subjects reported no differences in stomach upset, bloating, or nausea between P and CE. Results indicate that CE replacement elicits similar thermoregulatory and physiological responses during prolonged running in the heat but increases run performance and blood glucose when compared with P.

Publication types

  • Clinical Trial
  • Comparative Study
  • Controlled Clinical Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Beverages
  • Carbohydrates / pharmacology*
  • Electrolytes / pharmacology*
  • Hot Temperature
  • Humans
  • Male
  • Oxygen Consumption / drug effects
  • Running*
  • Water


  • Carbohydrates
  • Electrolytes
  • Water