Effects of glycemic index meal and CHO-electrolyte drink on cytokine response and run performance in endurance athletes

Abstract

Objective: To examine the effect of the glycemic index (GI) of a pre-exercise (PRE-ex) meal on plasma cytokine responses and endurance performance when carbohydrate-electrolyte (CHO-E) drink was consumed during exercise. Methods: Eight endurance-trained male runners (age: 28.6 ± 2.7 years; body mass: 61.9 ± 1.71 kg; over(V, ̇) O 2 max : 58.5 ± 1.6 ml kg -1 min -1 ) completed three trials in a randomized order. The pre-exercise meal consisted of either high-GI (HGI) (GI = 83), low-GI (LGI) foods (GI = 36) or control (CON) (low energy sugar-free jelly) was given to the participant 2 h before a 21-km performance run on a level treadmill. During each trial, 2 ml kg -1 BM of 6.6% CHO-E solution was consumed immediately before exercise and every 2.5-km afterward. Blood samples were collected before (pre-meal), and 120 min after ingestion the meal (120 min), immediately (POST), and 60 min (POST-60 min) after exercise. Results: No difference was found in time to complete the 21-km run between LGI and HGI. The interleukin-6 (IL-6) level increased by more than 100 times immediately after exercise in the three trials and returned to the basal level only on LGI at POST-60 min. In contrast, interleukin-2 (IL-2) level showed a transitory decrease at POST on CON (p < 0.001). Glucose concentrations did not recover to the pre-meal level by POST-60 min on HGI only. Cortisol concentrations increased throughout the exercise and were lower on LGI when compared with CON (p < 0.05) at POST-60 min. Conclusions: HGI and LGI demonstrated similar performance when CHO-E solution was consumed during a 21-km run. However, pre-exercise LGI meal attenuated the increases in cortisol and quickened the recovery of the increased IL-6 value. © 2008 Sports Medicine Australia.