They found that the participant who followed a Low Glycemic Index (LGI) diet showed significant improvements in running performance as opposed to those who followed a High Glycemic Index (HGI) diet, which the researchers attributed to increases in blood glucose during the trial time.
This is just more evidence in favor of using low glycemic carbs rather than high glycemic, insulin-spiking carbs. Athletes are taught to use insulin spikes post-workout for recovery, but this study shows otherwise. Of course, the best carbs come from vegetables and fruits. Sugar has no place in a healthful diet.