Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Johannesburg, South Africa
Oosthuyse, T., Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Johannesburg, South Africa; Carstens, M., Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Johannesburg, South Africa; Millen, A.M.E., Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Johannesburg, South Africa
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. 2h postprandial, 8 male cyclists ingested either: carbohydrate-only, carbohydrate-whey hydrolysate, carbohydrate-casein hydrolysate or placebo-water in a crossover, double-blind design during 2h of exercise at 60%W <inf>max</inf> followed by a 16-km time trial. Data were evaluated by magnitude-based inferential statistics. Exogenous carbohydrate oxidation, measured from 13CO<inf>2</inf> 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±33g for carbohydrate-casein, carbohydrate-whey and carbohydrate-only, respectively) and substantially increased (93% likely increase) total fat oxidation (92±14; 83±27; 73±19g) 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. © Georg Thieme Verlag KG Stuttgart.
carbohydrate diet; casein; casein hydrolysate; fructose; maltodextrin; polysaccharide; administration and dosage; adult; athletic performance; beverage; carbohydrate diet; comparative study; controlled study; crossover procedure; cycling; diet supplementation; double blind procedure; endurance; human; male; metabolism; oxidation reduction reaction; physiology; randomized controlled trial; whey; Adult; Athletic Performance; Beverages; Bicycling; Caseins; Cross-Over Studies; Dietary Carbohydrates; Dietary Supplements; Double-Blind Method; Fructose; Humans; Male; Oxidation-Reduction; Physical Endurance; Polysaccharides; Whey