The effect of carbohydrate ingestion on performance during a 30-km race

Int J Sport Nutr. 1993 Jun;3(2):127-39. doi: 10.1123/ijsn.3.2.127.


Seven experienced endurance runners completed a 30-km road race on two occasions separated by 10 days. On each occasion the subjects consumed 250 ml of either a 5% carbohydrate (CHO) solution or nonflavored tap water (W) immediately prior to the start of the race, and 150 ml of the assigned fluid every 5 km thereafter. Performance time for the CHO trial was faster compared with the time recorded for the W trial (128.3 +/- 19.9 min vs. 131.2 +/- 18.7 min [p < 0.01] respectively). Running speed was maintained throughout the race in the CHO trial, whereas a decrease in the running speed occurred after 25 km (p < 0.05) in the W trial. No difference was found between the two trials in blood glucose concentration, plasma electrolyte concentrations, body weight loss, change in plasma volume, and rating of perceived exertion. Blood lactate concentration was higher at 25 km during the CHO trial compared with the W trial (p < 0.01), but plasma FFA and glycerol concentrations were lower at 30 km during the CHO trial than during the W trial (p < 0.05). In conclusion, this study shows that performance time for a 30-km road race is improved after ingesting a 5% CHO solution.

MeSH terms

  • Adult
  • Beverages
  • Blood Glucose / metabolism
  • Dietary Carbohydrates / administration & dosage*
  • Electrolytes / blood
  • Fatty Acids, Nonesterified / blood
  • Female
  • Glycerol / blood
  • Humans
  • Lactates / blood
  • Lactic Acid
  • Male
  • Oxygen Consumption
  • Physical Endurance / physiology*
  • Running / physiology*


  • Blood Glucose
  • Dietary Carbohydrates
  • Electrolytes
  • Fatty Acids, Nonesterified
  • Lactates
  • Lactic Acid
  • Glycerol