<qa>  What is the main source of energy in labor?There is some controversy regarding intravenous hydration of patients during labor. While the use of a fast flow of hydration appears to be recognized beneficial, the addition of glucose is less well accepted. However studies on exercise physiology clearly demonstrates improved performance of skeletal muscle by increased hydration and carbohydrate replacement during prolonged exercise. This situation is similar to the condition of the uterus in labor especially since it is now established that glucose represents its principal source of energy. 