Author and graduation date: Laura Marie MISELL, June, 1998

Committee members: Mark J. Kern (Chair), Michael J. Buono, Michael Dowler

Thesis title: Chronic Medium-Chain Triglyceride Consumption and Endurance Performance in Trained Endurance Runners

The nature of medium-chained triglycerides (MCT) metabolism and past research leads to the hypothesis that chronic ingestion of MCT will enhance endurance exercise performance. The purpose of this study was to determine the effect of chronic MCT consumption on endurance performance in trained male runners. Twelve well-trained endurance runners participated in this randomized, cross-over, placebo-controlled, double-blinded study. Subjects ate a low-fat diet (~20% of kcal) and consumed fat supplement shakes containing either long-chain triglycerides (LCT) or MCT ( providing 56 and 60g fat per day, respectively) for two weeks. On the morning following each dietary phase and after an overnight fast, subjects completed a maximal treadmill test (to determine maximal oxygen uptake or VO2max) followed by an endurance treadmill test in which subjects ran at an intensity of ~85% of maximal oxygen uptake for 30 min then ~75% of maximal oxygen uptake until voluntary exhaustion. Blood samples were taken at rest and 45 minutes into the endurance test. Whole blood lactate, and serum concentrations of glucose, B-hydroxybutyrate(B-HBA), free fatty acids (FFA), glycerol and triglycerides (TG) were evaluated. Non-protein respiratory exchange ratios (RER) were assessed every 15 minutes to determine potential differences in substrate use during the endurance tests. Biomechanical data was analyzed by a 2x2 repeated measures ANOVA, while other variables were analyzed by paired t-tests. An alpha level of p<0.05 was selected as the criterion for statistical significance. VO2max was 72.4+ 2.6 and 72.0 + 2.3 ml/kg/min and running time to exhaustion was 106.5+ 8.5 and 99.8 + 6.8 min for LCT and MCT phases respectively. VO2max and running time did not differ significantly (p<0.05) between dietary phases. No diet X exercise interactions (p<0.05) were present for whole blood lactate or serum concentrations of glucose, B-HBA, FFA, glycerol or TG. RER was significantly higher (p<0.05) only at 15 min during the endurance test following the MCT dietary phase. In conclusion, findings of this study suggest that chronic MCT consumption does not cause an endurance enhancing effect in trained male runners. The conclusion is supported by the lack of significant effects on VO2max, running time to exhaustion, RER, lactate production, and serum glucose, TG, FFA, glycerol and B-HBA levels at baseline and during exercise.

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