Carbohydrate-electrolyte replacement improves distance running performance in the heat.

Area of Science:

• Sports Science
• Exercise Physiology
• Nutritional Science

Background:

• Hydration and fueling are critical for endurance athletes, especially in heat.
• Carbohydrate-electrolyte drinks (CE) are commonly used to enhance performance and fluid balance.
• The specific impact of CE on physiological responses and performance during prolonged heat exertion needs further clarification.

Purpose of the Study:

• To compare the effects of a 7% carbohydrate-electrolyte drink (CE) versus a placebo (P) on physiological function and 40-km running performance in the heat.
• To assess thermoregulatory responses, metabolic markers, and perceived exertion during prolonged exercise with CE and P.
• To evaluate the impact of CE on running speed during the final 5 km of a 40-km run.

Main Methods:

• Eight highly trained male runners participated in a double-blind, counterbalanced study.
• Subjects completed two 40-km outdoor runs in the heat, consuming either CE or P before and during exercise.
• Physiological variables (temperature, heart rate, blood markers) and performance metrics were measured.

Main Results:

• Blood glucose levels were significantly higher with CE compared to P (P<0.01).
• Running performance in the final 5 km was significantly faster with CE (21.9 min) than P (24.4 min) (P<0.03).
• Thermoregulatory and other physiological responses, as well as gastrointestinal comfort, were similar between CE and P conditions.

Conclusions:

• Carbohydrate-electrolyte replacement during prolonged running in the heat elicits similar thermoregulatory and physiological responses compared to a placebo.
• CE intake significantly enhances running performance and blood glucose levels without increasing adverse gastrointestinal symptoms.
• These findings support the use of CE drinks for improving endurance performance in hot conditions.