The Effect of a Low Glycemic vs. High Glycemic PreExercise Meal in Recreationally Trained Endurance Cyclists

The purpose of this study was to examine the effects of two iso-kilocaloric (837.2 kJ) pre-exercise meals: a low glycemic meal (LGM) vs. a high glycemic meal (HGM) and a placebo meal in recreational cyclists on endurance cycling. After a 2-d high carbohydrate diet and abstention from exercise, 18 healthy recreationally trained male subjects aged 18 to 35 yrs with a VO sub(2) max of 3.94 + or - 0.6 L times min super(-1) participated in this within-subject design study. Each of three rides consisted of 2 hr of cycling exercise at 55% VO sub(2) max followed by a brief 30 min rest and a moderately high intensity ride to exhaustion at 80% VO sub(2) max. The LGM did not exert a greater ergogenic effect in this study when compared to the isokilocaloric HGM. While the effect was not statistically significant, the HGM meal outperformed the LGM and the placebo on time to exhaustion. A fiber-free, glucose-derived meal may be superior to a low glycemic fiber-free whole meal in supporting moderately high intensity exercise in some highly motivated recreationally trained endurance athletes.