Pre-exercise carbohydrate meal and endurance running capacity when carbohydrates are ingested during exercise.

Department of Physical Education, Sports Science and Recreation Management, Loughborough University, England, UK.
International Journal of Sports Medicine (Impact Factor: 2.37). 10/1997; 18(7):543-8. DOI: 10.1055/s-2007-972679
Source: PubMed

ABSTRACT This study examined whether combining a pre-exercise carbohydrate meal with the ingestion of a carbohydrate-electrolyte solution during exercise is better in improving endurance running capacity than a carbohydrate-electrolyte solution alone. Ten men completed three treadmill runs at 70% VO2max to exhaustion. They consumed 1.) a carbohydrate meal three hours before exercise and a carbohydrate-electrolyte solution during exercise (M + C), or 2.) a liquid placebo three hours before exercise and the carbohydrate-electrolyte solution during exercise (P + C), or 3.) a placebo three hours before exercise and placebo during exercise (P + P). When the meal was consumed (M + C) serum insulin concentrations were higher at the start of exercise, and carbohydrate oxidation rates were higher during the first 60 min of exercise compared with the values found in the P + C and P + P trials (p < 0.01). Exercise time was longer in the M + C (147.4+/-9.6 min) compared with the P + C (125.3+/-7 min) (p < 0.01). Also, exercise time was longer in M + C and P + C compared with the P + P (115.1+/-7.6 min) (p < 0.01 and p < 0.05 respectively). These results indicate that the combination of a pre-exercise carbohydrate meal and a carbohydrate-electrolyte solution further improves endurance running capacity than the carbohydrate-electrolyte solution alone.

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    ABSTRACT: Influence of high and low glycemic index meals on endurance running capacity. Med Purpose: The purpose of this study was to examine the effect of high and low glycemic index (GI) carbohydrate (CHO) pre-exercise meals on endurance running capacity. Methods: Eight active subjects (five male and three female) ran on a treadmill at ~70% [latin capital V with dot above]O 2max to exhaustion on two occasions separated by 7 d. Three hours before the run after an overnight fast, each subject was given in a single-blind, random order, isoenergetic meal of 850 ± 21 kcal (mean ± SEM; 67% carbohydrate, 30% protein, and 3% fat) containing either high (HGI) or low (LGI) GI carbohydrate foods providing 2.0 g CHO·kg -1 body weight. Results: Ingestion of the HGI meal resulted in a 580% and 330% greater incremental area under the 3-h blood glucose and serum insulin response curves, respectively. Performance times were not different between the HGI and LGI trials (113 ± 4 min and 111 ± 5 min, respectively). During the first 80 min of exercise in the LGI trial, CHO oxidation was 12% lower and fat oxidation was 118% higher than in the HGI trial. Although serum insulin concentrations did not differ between trials, blood glucose at 20 min into exercise in the HGI trial was lower than that during the LGI trial at the same time (3.6 ± 0.3 mmol·L -1 vs 4.3 ± 0.3 mmol·L -1 ; P < 0.05). During exercise, plasma glycerol and serum free fatty acid concentrations were lower in the HGI trial than in the LGI trial. Conclusions: This results demonstrate that although there is a relative shift in substrate utilization from CHO to fat when a low GI meal is ingested before exercise compared with that for a high GI meal, there is no difference in endurance running capacity. Acarbohydrate (CHO) meal ingested 3-4 h before exercise can increase liver (20) and muscle glycogen concentrations (9) as well as provide an absorbable source of CHO as it empties from the stomach (31). Pre-exercise CHO meals also affect the metabolic response and substrate utilization during exercise. Different methods have been used to study the influence of pre-exercise feeding on energy metabolism during exercise. These include using different monosaccharides, whole foods with different GI values, foods that are processed differently, and the addition of other macro-nutrients to a CHO source. A few studies have considered the GI of foods when studying the effect of pre-exercise ingestion of CHO meals (10,14,24,25). Despite differences in the metabolism of fast and slowly digested starches, the benefits from eating starch on endurance performance remain unclear. To provide high and low GI CHO meals, Thomas and Febbraio (10,24,25) used lentils and potatoes in their studies. The amount of potatoes and lentils consumed was calculated to provide 1 g CHO·kg -1 body weight (BW). However, in lentils there is significantly more protein than in potatoes. From values provided by Thomas et al. (25) the protein and energy content of the lentil meal was 208% and 36% higher, respectively, than in the potato meal. Therefore, their preexercise meals were not isoenergetic nor of the same macronutrient composition. Because of the energy differences between the test meals, the results of these studies should be interpreted with caution. Furthermore, it is not known how much of the enhanced insulinemic, depressed glycemic, and other metabolic response can be attributed to the increased protein content of the lentil meal.
    Medicine and science in sports and exercise 01/1999; 31:393-399. · 4.48 Impact Factor
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    ABSTRACT: In the last decade, research has begun to investigate the efficacy of carbohydrate supplementation for improving aspects of physical capacity and skill performance during sport-specific exercise in adolescent team games players. This research remains in its infancy, and further study would be beneficial considering the large youth population actively involved in team games. Literature on the influence of carbohydrate supplementation on skill performance is scarce, limited to shooting accuracy in adolescent basketball players and conflicting in its findings. Between-study differences in the exercise protocol, volume of fluid and carbohydrate consumed, use of prior fatiguing exercise and timing of skill tests may contribute to the different findings. Conversely, initial data supports carbohydrate supplementation in solution and gel form for improving intermittent endurance running capacity following soccer-specific shuttle running. These studies produced reliable data, but were subject to limitations including lack of quantification of the metabolic response of participants, limited generalization of data due to narrow participant age and maturation ranges, use of males and females within the same sample and non-standardized pre-exercise nutritional status between participants. There is a lack of consensus regarding the influence of frequently consuming carbohydrate-containing products on tooth enamel erosion and the development of obesity or being overweight in adolescent athletes and non-athletes. These discrepancies mean that the initiation or exacerbation of health issues due to frequent consumption of carbohydrate-containing products by adolescents cannot be conclusively refuted. Coupled with the knowledge that consuming a natural, high-carbohydrate diet ∼3–8 hours before exercise can significantly alter substrate use and improve exercise performance in adults, a moral and ethical concern is raised regarding the direction of future research in order to further knowledge while safeguarding the health and well-being of young participants. It could be deemed unethical to continue study into carbohydrate supplementation while ignoring the potential health concerns and the possibility of generating similar performance enhancements using natural dietary interventions. Therefore, future work should investigate the influence of pre-exercise dietary intake on the prolonged intermittent, high-intensity exercise performance of adolescents. This would enable quantification of whether pre-exercise nutrition can modulate exercise performance and, if so, the optimum dietary composition to achieve this. Research could then combine this knowledge with ingestion of carbohydrate-containing products during exercise to facilitate ethical and healthy nutritional guidelines for enhancing the exercise performance of adolescents. This article addresses the available evidence regarding carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescent team games players. It discusses the potential health concerns associated with the frequent use of carbohydrate-containing products by adolescents and how this affects the research ethics of the field, and considers directions for future work.
    Sports Medicine 10/2012; 42(10). · 5.32 Impact Factor
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    ABSTRACT: utilization during subsequent exercise muscle glycogen storage at rest but augments its Ingestion of a high-glycemic index meal increases You might find this additional information useful...2/707#BIBL 1 other HighWire hosted article: This article has been cited by [PDF] [Full Text] [Abstract] , August 1, 2006; 84 (2): 354-360. Am. J. utilization during subsequent exercise in women Influence of high-carbohydrate mixed meals with different glycemic indexes on substrate including high-resolution figures, can be found at: Updated information and services can be found at: Journal of Applied Physiology about Additional material and information This information is current as of August 7, 2006 .. those papers emphasizing adaptive and integrative mechanisms. It is published 12 times a year (monthly) by the American publishes original papers that deal with diverse areas of research in applied physiology, especially
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