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J Appl Physiol (March 27, 2008). doi:10.1152/japplphysiol.00878.2007
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Submitted on August 15, 2007
Accepted on March 26, 2008

Effect of Graded Fructose Co-Ingestion with Maltodextrin on Exogenous 14C-Fructose and 13C-Glucose Oxidation Efficiency and High-Intensity Cycling Performance

David Stephen Rowlands1*, Megan Stacey Thorburn1, Rhys M. Thorp1, Suzanne Broadbent1, and Xiaocai Shi2

1 Institute of Food, Nutrition and Human Health, Massey University, Wellington, Wellington, New Zealand
2 Gatorade Sport Science Institute, Chicago, Illinois, United States

* To whom correspondence should be addressed. E-mail: d.s.rowlands{at}massey.ac.nz.

The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g. fructose and glucose) produce greater carbohydrate and water absorption compared with single-carbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient utilisation of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing 13C-maltodextrin at 0.6 g·min-1 combined with 14C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g·min-1, giving fructose:maltodextrin ratios of 0.5, 0.8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g·min-1 in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (=oxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g·min-1 (98% efficiency) compared to 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits ±16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g·min-1. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and High-Fructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient utilisation of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses.







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