Effect of the glycaemic index of pre‐exercise carbohydrate meals on running performance

Abstract

The aim of this study was to examine the effect of pre-exercise low and high glycaemic index (GI) carbohydrate meals on running performance. Eight endurance-trained male runners (mean age 33 years, s x 01.7; V O 2max 63 ml × kg(1 × min (1 , s x 01.8) completed two trials separated by at least 7 days in a counterbalanced design. Two hours before they were to run and after an overnight fast, each participant consumed an isocaloric meal containing either low (GI 037) or high (GI077) GI carbohydrate foods (2.4 MJ; 65% carbohydrate; 15% protein; 20% fat) that provided 1.5 g carbohydrate per kilogram of body mass in random order. Each trial consisted of a 21-km performance run on a level treadmill. The participants were required to run at 70% V O 2max during the first 5 km of the run. They subsequently completed the remaining 16 km in as short a time as possible. All participants achieved a faster performance time after the consumption of the low GI meal (low vs. high GI: 98.7 min, s x 02 vs. 101.5 min, s x 02; P B0.01). Blood glucose and serum free fatty acids concentrations were higher throughout the performance run in the low GI trial. Serum insulin concentrations were higher in the high GI trial during the postpandial resting period. However, there were no differences between trials in serum insulin or blood lactate concentrations throughout exercise. Compared with the high GI trial, carbohydrate oxidation was 9.5% lower and fat oxidation was 17.9% higher during exercise in the low GI trial. In conclusion, our results indicate that compared with an isocaloric high GI meal, the consumption of a low GI meal 2 h before a 21-km performance run is a more effective means of improving performance time.

Influence of Glycemic Index-Based Menu on Endurance Performance of Athletes

“…The shorter time taken for finishing the 5-km run in high-GI group when compared with high-GI subjects is presumably because the subjects consuming low-GI meal have relatively more stable glucose availability as an energy source than those consuming high-GI meal. The result of this research is in line with the research conducted by Wong et al (2008) which suggests that the subjects with low-GI meal show faster finishing times when compared with those with high-GI meal (low GI = 98.7 minutes and high GI = 101.5 minutes). The same result of investigation is also obtained from Wu and Williams (2006), which suggest that the endurance capacity of subjects taking low-GI meal three hours before running on treadmill is larger than those with high-GI meal.…”

“…In high-GI meal, the blood glucose will be stored optimally as muscle glycogens that are reduced as they are used in doing sports. This is similar to the finding of Wong et al (2008), which suggests that the blood glucose concentration remains high during sport activity after consuming low-GI meal. Moore et al (2000) in his research also describes that the blood glucose level at fatigue point after bicycling is higher in low-GI treatment (5.2  0.6 mmol/L) than high-GI treatment (4.7  0.7 mmol/L).…”

“…In the initial training, the value of insulin concentration is similar to the fasting value in low GI, but in high GI it remains 150% higher than the value of insulin concentration when fasting. This is also suggested by research conducted by Wong et al (2008) in which he provided the mixtures of high GI and low GI meals containing 65% carbohydrates, 15% proteins, and 20% fats of the total calories. He found that the concentration of serum insulin during postprandial period is higher in high-GI meal than in low-GI meal.…”

“…10, No. 5;2014 and decreases to the fasting value in the last training in high-GI treatment (Wong et al, 2008). The reduction of carbohydrate reserve is one of the primary causes for an exacerbation of performance and an increase of fatigue during the long-term sport in sub-maximal running (Wong & Williams, 2000).…”

Comparison between Preexercise Meals Intake Effect with Different Glycemic Load on Exercise Performance in Female Athletes

“…Manipulation of GI from different sources of CHO in order to optimizing athletic performance has been investigated in different studies [8,10]. Researches show that a CHO-rich meal with LGI level is a suitable choice before prolonged exercises plan, because it causes blood glucose being more stable and maintains free fatty acids (FFA) at higher levels during exercises [11,12]. With regards to this point that increasing fat availability during exercise enhances the capacity of trained individuals to perform prolonged exercise [13].…”