Two recent studies (Ivy et al., Int J Sports Nutr Exerc Metab 13:382-395, 2003; Saunders et al., Med Sci Sports Exerc 36:1233-1238, 2004) reported dramatic (>25%) increases in endurance time to fatigue during cycling at 75-85% V0₂peak when subjects ingested a ~2% protein (PRO) plus ~7% carbohydrate (CHO) drink as compared to CHO alone. However, the research designs employed in these studies have been criticized for several reasons, including (1) the rate of CHO and fluid provided was less than what is considered optimal for endurance performance (i.e., 6% CHO, ingested at a rate of 15 g in 250 ml of fluid, every 15 min); and (2) the nature of the performance tests did not mimic the way in which athletes typically compete (i.e., a race, in which a given distance must be covered as quickly as possible). Purpose: To determine whether the addition of 2% Pro to a 6% CHO drink (CHO-Pro) improves 80 km cycling time trial performance as compared to a 6% CHO drink and a non-energetic sweetened placebo. Methods: Ten well-trained cyclists (25±5 y; V0₂peak = 63±5 ml/kg/min; means±SD) completed a simulated 80 km time trial (TT) on three separate occasions separated by 5-7 d. In a randomized, double-blind manner, subjects ingested either CHO-Pro, CHO or placebo at a rate of 250 ml every 15 min. All trials were performed on a Computrainer (RacerMate, Seattle, WA) using each subject's own bicycle with no temporal, verbal or physiological feedback. Venous blood samples were obtained periodically during exercise and subsequently analyzed for glucose, lactate, free fatty acids, ammonia and insulin concentrations. Results: Analysis of variance revealed that time to complete the 80 km TT was lower (P≤0.05) when subjects ingested CHO (135±9 min; mean±SD) and CHOPro (135±9) compared to placebo (141±10), with no difference between CHO-Pro and CHO. Average power output was higher (P<0.05) when subjects ingested CHO and CHO-Pro versus placebo, and work intensity averaged 81±1%, 80±1% and 78±1% of heart rate reserve for the CHO, CHO-Pro and placebo rides, respectively. Improved performance of the two CHO trials was primarily attributed to maintenance of blood glucose concentration during the later stages of exercise. Conclusion: Ingestion of a 6% CHO drink at a rate of 1 L/h improves 80 km TT performance, as compared to a non-energetic placebo, in trained male cyclists. However, the addition of 2% Pro to a 6% CHO drink provides no additional performance benefit. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22534 |
| Date | 07 1900 |
| Creators | van Essen, Martin |
| Contributors | Gibala, Martin, Human Biodynamics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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