This study compared two high carbohydrate (CHO) diets in 14 male runners for effects on muscle glycogen deposition, endurance, and sensations of gastrointestinal discomfort. Muscle glycogen was measured in the vastus lateralis at rest and run time to exhaustion at 75 % VO2max was measured following 3-1/2 days on a 50% CHO diet. After 14 days the subjects consumed a 20% CHO diet and continued training to reduce glycogen. During the next 3-1/2 days, subjects ran less and consumed a 90% CHO diet emphasizing pasta and rice (Pasta, n=7) or lesser amounts of pasta and rice supplemented by a maltodextrin beverage (Supplement, n=7). Glycogen was again measured, followed by a second run to exhaustion. Compared to the 50% CHO diet, Pasta increased muscle glycogen by 27.1 ± 12.2 mmoles/kg muscle (M±SE; p < 0.05) and run time by 15.7±5.9 min; Supplement increased glycogen by 43.2 ± 13.5 mmoles/kg (p < 0.05) and run time by 29.0 ± 7.4 min (p < 0.05). Total glycogen concentrations and run times were not significantly different for Pasta versus Supplement. Subjects reported less gastrointestinal discomfort and greater overall preference for Supplement than for Pasta. Thus, glycogen loading can be accomplished at least as effectively and more comfortably by substituting a maltodextrin drink for some of the pasta and rice in a glycogen loading diet.
David R. Lamb, Ann C. Snyder, and Thomas S. Baur
Nicole Leenders, W. Michael Sherman, David R. Lamb, and Timothy E. Nelson
The purpose of this study was to determine if oral creatine (CR) ingestion, compared to a placebo (PL), would enable swimmers to maintain a higher swimming velocity across repeated interval sets over 2 weeks of supplementation. Fourteen female and 18 male university swimmers consumed a PL during a 2-week baseline period. Using a randomized, double-blind design, during the next 2 weeks subjects consumed either CR or PL. Swimming velocity was assessed twice weekly during 6 × 50-m swims and once weekly during 10 × 25-yd swims. There was no effect ofCR on the 10 × 25-yd interval sets for men and women and no effect on the 6 × 50-m interval sets for women. In contrast, for men, CR significantly improved mean overall swimming velocity in the 6 × 50-m interval after 2 weeks of supplementation, whereas PL had no effect. Although ineffective in women, CR supplementation apparently enables men to maintain a faster mean overall swimming velocity during repeated swims each lasting about 30 s; however, CR was not effective for men in repeated swims each lasting about 10-15 s.