Seven experienced male bicyclists performed four endurance test rides at 70% ( ± 5) VO₂ max on a bicycle at 90 RPM over a four week period. stationary Subjects consumed a high carbohydrate diet (70%) for two days prior to each test ride. During each test, heart rate (HR), rate of perceived exertion (RPE), VO₂ , respiratory exchange ratio (R), serum free fatty acid (FFA) and serum glucose levels were measured. One of the four test treatments was randomly administered, in a single-blind design, at 5, 25, and 40 minutes into each exercise bout. The control trial (CTR) included 50 gelatin capsules containing water, and a lemonade beverage (150 ml each) sweetened with an artificial sweetener (Saccharin). The test mixtures were made up in the same manner as the control with the addition of one of the test substances: 1) MCT oil (M), 2) glucose polymer (P) (Polycose, Ross Laboratories), 3) MCT plus glucose polymer (MP). Depending on the treatment used, MCT oil-containing capsules replaced water-capsules and/or Polycose was dissolved in the lemonade beverage. Total caloric intake of each trial, except control, was 360 calories. No significant difference was found between mean time to exhaustion for the four treatments. No significant difference was noted between treatments for R, VO₂ , and HR responses (p < 0.05). Significantly greater RPE values were found over the first 60 minutes of exercise for the Control treatment as compared to the other three treatments (p < 0.05). Repeated measures ANOVA showed that significantly higher serum glucose values existed for treatment P as compared to M and also significantly higher serum FFA values existed for treatment M as compared to both P and MCT oil with Polycose (MP) over the first 60 minutes of exercise (p < 0.05). Although the combination of MCT oil and Polycose would theoretically enhance endurance performance due to an increased supply of both FFA and glucose available for muscular metabolism, this dietary treatment was ineffective in prolonging exercise time. / Master of Science