Although, it is known that feeding with carbohydrate (CHO) during exercise improves endurance performance, the effects of glycemic index (GI ) of carbohydrate intake are less clear. This study was carried out to assess the effect of glycemic index of pre-exercise carbohydrate feeding on endurance exercise capacity.

          In a randomized clinical trial 52 endurance – trained men with mean age 21.7 ± 3 years, weight 69.3 ± 9 kg, height 178.4 ± 2 cm and BMI 22.6 ± 2 were studied. Subjects performed exercise treadmill at 70% VO₂max after ingestion: Lentil, a low glycemic index; potato, a high glycemic index; glucose and water (as a control) one hour before exercise. Blood samples were collected before and one hour after test meal and 30 minutes after
  exercise. To assess aerobic capacity VO₂max (maximum oxygen uptake) was measured at the end of the exercise trial.

          Endurance time was found to be longer after lentil than after the potato, glucose and control respectively (P < 0.05). At the end of exercise, the glucose group and control both gave lower plasma glucose concentrations. Changes of VO₂max in lentil. Potato, glucose and control group which were not statistically significant.

          This study showed that a low GI meal eaten before an event increases endurance capacity during exercise. Furthermore, the low GI meal was found to maintain glucose at higher concentrations during the later stages of exercise.