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Maltodextrin's Effect on the Performance of Elite Mountain Biking Athletes During Simulated Competition and on Power Output at the Ventilatory Threshold

Human Movement

July 2011
12(3)

DOI:10.2478/v10038-011-0023-9

Authors:

Erivelton Fontana de Laat

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Purpose. To aim of this study was to analyze the effects of maltodextrin supplementation on cardiovascular and performance parameters during simulated Mountain Biking (MTB) competition as well as the cardiorespiratory and blood glucose (BG) response to a maximal test performed in a laboratory on elite MTB athletes. Methods. A total of eight male bikers [age: 28.4 ± 10.6 years; body fat: 9.46 ± 3.76 %; VO2max: 55.31 ± 4.7 mL/kg/min], participated in a double-blind study. The athletes received maltodextrin supplementation (1g/kg) or a placebo (light tangerine juice) 20 min before competition (seven 2 km laps) or before a laboratory maximal test. An incremental exercise test on a cycloergometer was performed to find any alterations in maximal HR, Watts max, VO2max, VEmax, and VO2 at the ventilatory threshold (VT), using a gas exchange analyzer. Comparisons between the simulated competition and laboratory variables (maltodextrin vs. placebo) were made using ANOVA and a two-tailed paired Student's t-test, where p < 0.05 was considered statistically significant. Results. Maltodextrin supplementation reduced 26 s in the mean time spent on completing all laps (Maltodextrin: 9 min and 16 s vs. placebo: 9 min and 35 s; p < 0.05). In laboratory testing, maltodextrin raised BG during exercise (Maltodextrin: 104.1 ± 20.9 mg/dL vs. placebo: 88.2 ± 5.3 mg/dL; p < 0.05), power output at the ventilatory threshold (Maltodextrin: 260.8 ± 12.9 vs. placebo: 150.5 ± 8.7; p < 0.05) but had no effect on cardiorespiratory variables. Conclusion. Maltodextrin was found to enhance athletic performance during MTB competition, showing that it can play an important role in supplementation strategies for these competitors.

Mean heart rate (data measured every 5 s) observed during simulated MTB competition using maltodextrin (CHO) or a placebo (data are mean; n = 8)

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Time spent on each lap during simulated MTB competition using maltodextrin (CHO) or a placebo (data are mean ± SE; n = 8)

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Five male cyclists were studied during 2 h of cycle ergometer exercise (70% VO2 max) on two occasions to examine the effect of carbohydrate ingestion on muscle glycogen utilization. In the experimental trial (CHO) subjects ingested 250 ml of a glucose polymer solution containing 30 g of carbohydrate at 0, 30, 60, and 90 min of exercise; in the control trial (CON) they received an equal volume of a sweet placebo. No differences between trials were seen in O2 uptake or heart rate during exercise. Venous blood glucose was similar before exercise in both trials, but, on average, was higher during exercise in CHO [5.2 +/- 0.2 (SE) mmol/l] compared with CON (4.8 +/- 0.1, P less than 0.05). Plasma insulin levels were similar in both trials. Muscle glycogen levels were also similar in CHO and CON both before and after exercise; accordingly, there was no difference between trials in the amount of glycogen used during the 2 h of exercise (CHO = 62.8 +/- 10.1 mmol/kg wet wt, CON = 56.9 +/- 10.1). The results of this study indicate that carbohydrate ingestion does not influence the utilization of muscle glycogen during prolonged strenuous exercise.

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The purpose of this study was to determine whether the postponement of fatigue in subjects fed carbohydrate during prolonged strenuous exercise is associated with a slowing of muscle glycogen depletion. Seven endurance-trained cyclists exercised at 71 +/- 1% of maximal O2 consumption (VO2max), to fatigue, while ingesting a flavored water solution (i.e., placebo) during one trial and while ingesting a glucose polymer solution (i.e., 2.0 g/kg at 20 min and 0.4 g/kg every 20 min thereafter) during another trial. Fatigue during the placebo trial occurred after 3.02 +/- 0.19 h of exercise and was preceded by a decline (P less than 0.01) in plasma glucose to 2.5 +/- 0.5 mM and by a decline in the respiratory exchange ratio (i.e., R; from 0.85 to 0.80; P less than 0.05). Glycogen within the vastus lateralis muscle declined at an average rate of 51.5 +/- 5.4 mmol glucosyl units (GU) X kg-1 X h-1 during the first 2 h of exercise and at a slower rate (P less than 0.01) of 23.0 +/- 14.3 mmol GU X kg-1 X h-1 during the third and final hour. When fed carbohydrate, which maintained plasma glucose concentration (4.2-5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 +/- 0.33 h; P less than 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise performed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU X kg-1 X h-1; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue.