Low Glycemic Index Pre-exercise Meal Attenuates Blood Leukocyte Redistribution During Subsequent Exercise

Abstract

1761 Carbohydrate ingestion during prolonged strenuous exercise attenuates the leukocytosis and subsequent neutrophilia and lymphopenia by maintaining plasma glucose concentration and minimizing stress hormone responses. Ingestion of a low glycemic index (LGI) meal before exercise has been demonstrated to better maintain plasma glucose levels during subsequent submaximal exercise compared with a high glycemic index (HGI) meal. PURPOSE: To determine whether the redistribution of leukocytes during endurance exercise is affected by the glycemic index of a preexercise high carbohydrate meal. METHODS: Eight male subjects (age 27.5 ± 1.5 yrs, body mass 72.1 ± 1.6 kg, height 1.77 ± 0.02 m, VO2max 60.7 ± 1.3 mL·kg−1·min−1; mean ± S.E.M.) performed two 90-min runs on a treadmill at 70% VO2max three hours after ingesting a HGI or LGI meal. Each isocaloric test meal contained 2 g·kg−1 body mass of carbohydrate and the glycemic index values were 77 and 37, respectively. Trials were separated by at least 7 days in counterbalanced order. Results were analysed using a two-factor (trial × time) repeated measures ANOVA with post hoc comparison as appropriate. RESULTS: Blood leukocyte and neutrophil counts were significantly lower in LGI than HGI at 90-min of exercise (8.70 ± 0.80 vs. 10.12 ± 0.94 and 4.75 ± 0.63 vs. 6.47 ± 0.77 × 109·L−1; both P < 0.05). The ratio of neutrophils/lymphocytes was significantly lower in LGI than HGI at 90-min (1.57 ± 0.17 vs. 2.28 ± 0.27, P < 0.05). Plasma glucose concentrations were significantly higher in LGI than HGI at 15-min and 45-min of exercise. However, there were no significant differences in plasma cortisol, human growth hormone and interleukin-6 concentrations between trials. CONCLUSION: Ingestion of a LGI meal 3 h before submaximal exercise attenuates the increase in circulating leukocyte and neutrophil counts, and better maintains plasma glucose concentration during subsequent exercise when compared with ingestion of a HGI meal. However, it seems to have limited effects on circulating stress hormone and cytokine responses to exercise.