Abstract

There are a wide variety of metabolic responses to the different types of carbohydrates and their influence on metabolism during endurance training. The primary aim of the study was to indicate the importance of utilizing the Glycemic Index (GI) as part of the nutritional preparation for endurance events and to investigate the advantages of ingesting a Low Glycemic Index (LGI) meal prior to exercise opposed to a High Glycemic Index (HGI) meal. Twelve healthy male and female cyclists participated in the study. The total test period was 14 days and included two different dietary interventions of 7 days each. Three exercise trails were performed. The first exercise trial was a VO2max test until exhaustion. Two maximal trials (65 - 70 % of VO2max) followed and were preceded by two dietary interventions. The dietary interventions (7 days each) had the same amount of CHO, fat and protein but the GI of the two pre-exercise meals differed. The first pre-exercise meal had a HGI, while the second had a LGI. The results of the study indicated the advantages of ingesting a LGI meal prior to endurance exercise. The difference between pre- and post-exercise blood glucose levels was significant (p<0.05). Levels decreased with an average of 0.68 mmol/L after 10 minutes of cycling. After the ingestion of the HGI meal in Test 1, the blood lactate levels were significantly higher (p<0.05) during the first 15 minutes of cycling. The total distance covered by the subjects was 22.86±4.74 km after the first dietary intervention (HGI food) and 27.43±5.90 km after the second dietary intervention (LGI food). These differences were, however, not statistically significant probably due to the small sample size. Subjects indicated that they experienced more physical strain (higher RPE values) during Test 1 (HGI food) than during Test 2 (LGI food) (p<0.05). The study results supported the suggestion that LGI food may benefit performance when eaten prior to prolonged strenuous exercise by maintaining blood glucose levels and thereby preventing hypoglycemia. Verf.-Referat