76 / Kreider et al. R.B. Kreider, C. Melton, C. Rasmussen, J. Lundberg, and M. Greenwood are with the Exercise & Sport Nutrition Laboratory, Center for Exercise, Nutrition & Preventive Health, in the Department of Health, Human Performance & Recreation at Baylor University, Waco, TX 76798-7313. C. Earnest is with the Division of Epidemiology & Clinical Applications at The Cooper Institute for Aerobics Research, 12330 Preston Road, Dallas, TX 75230. A. Almada is with MetaResponse Sciences, Inc., 30131 Town Center Drive, #211, Laguna Niguel, CA 92677. Address correspondence to Dr. Kreider. 76 Effects of Oral D-Ribose Supplementation on Anaerobic Capacity and Selected Metabolic Markers in Healthy Males R.B. Kreider, C. Melton, M. Greenwood, C. Rasmussen, J. Lundberg, C. Earnest, and A. Almada Oral D-ribose supplementation has been reported to increase adenine nucle- otide synthesis and exercise capacity in certain clinical populations. Theoreti- cally, increasing adenine nucleotide availability may enhance high intensity exercise capacity. This study evaluated the potential ergogenic value of D- ribose supplementation on repetitive high-intensity exercise capacity in 19 trained males. Subjects were familiarized to the testing protocol and performed two practice-testing trials before pre-supplementation testing. Each test in- volved warming up for 5 min on a cycle ergometer and then performing two 30- s Wingate anaerobic sprint tests on a computerized cycle ergometer separated by 3 min of rest recovery. In the pre- and post-supplementation trials, blood samples were obtained at rest, immediately following the first and second sprints, and following 5 min of recovery from exercise. Subjects were then matched according to body mass and anaerobic capacity and assigned to ingest, in a randomized and double blind manner, capsules containing either 5 g of a dextrose placebo (P) or D-ribose (R) twice daily (10 g/d) for 5 d. Subjects then performed post-supplementation tests on the 6th day. Data were analyzed by ANOVA for repeated measures. Results revealed a significant interaction (p = .04) in total work output. Post hoc analysis revealed that work significantly declined (–18 ± 51 J) during the second post-supplementation sprint in the P group while being maintained in the R group (–0.0 ± 31 J). No significant interactions were observed in peak power, average power, torque, fatigue in- dex, lactate, ammonia, glucose, or uric acid. Results indicate that oral ribose supplementation (10 g/d for 5 d) does not affect anaerobic exercise capacity or metabolic markers in trained subjects as evaluated in this study. Key Words: exercise, sport nutrition, ergogenic aids International Journal of Sport Nutrition and Exercise Metabolism, 2003, 13, 76-86 © 2003 Human Kinetics Publishers, Inc.