Whey or Casein Hydrolysate with Carbohydrate for Metabolism and Performance in Cycling.
The protein type most suitable for ingestion during endurance exercise is undefined. This study compared co-ingestion of either 15 g/h whey or casein hydrolysate with 63 g/h fructose: maltodextrin (0.8:1) on exogenous carbohydrate oxidation, exercise metabolism and performance. 2 h postprandial, 8 male cyclists ingested either: carbohydrate-only, carbohydrate-whey hydrolysate, carbohydrate-casein hydrolysate or placebo-water in a crossover, double-blind design during 2 h of exercise at 60%W max followed by a 16-km time trial. Data were evaluated by magnitude-based inferential statistics. Exogenous carbohydrate oxidation, measured from (13)CO2 breath enrichment, was not substantially influenced by co-ingestion of either protein hydrolysate. However, only co-ingestion of carbohydrate-casein hydrolysate substantially decreased (98% very likely decrease) total carbohydrate oxidation (mean±SD, 242±44; 258±47; 277±33 g for carbohydrate-casein, carbohydrate-whey and carbohydrate-only, respectively) and substantially increased (93% likely increase) total fat oxidation (92±14; 83±27; 73±19 g) compared with carbohydrate-only. Furthermore, only carbohydrate-casein hydrolysate ingestion resulted in a faster time trial (-3.6%; 90% CI: ±3.2%) compared with placebo-water (95% likely benefit). However, neither protein hydrolysate enhanced time trial performance when compared with carbohydrate-only. Under the conditions of this study, ingesting carbohydrate-casein, but not carbohydrate-whey hydrolysate, favourably alters metabolism during prolonged moderate-strenuous cycling without substantially altering cycling performance compared with carbohydrate-only.
Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, Johannesburg, South Africa.
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Oosthuyse
Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, Johannesburg, South Africa.
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M
Carstens
Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, Johannesburg, South Africa.
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AM
Millen
D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages; D001642:Bicycling / Q000502:physiology*; D002364:Caseins / Q000008:administration & dosage / Q000378:metabolism*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005632:Fructose / Q000008:administration & dosage / Q000378:metabolism; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology; D011134:Polysaccharides / Q000008:administration & dosage / Q000378:metabolism; D000067796:Whey / Q000008:administration & dosage / Q000378:metabolism*
D002364:Caseins; D004040:Dietary Carbohydrates; D011134:Polysaccharides; D005632:Fructose; C475729:casein hydrolysate; C008315:maltodextrin