부산대학교 도서관

Dietary nitrates have been shown to increase vasodilation, mitochondrial efficiency, muscle contractility, and reduce ATP turnover which has led to improvements in measures of athletic performance in previous work. PURPOSE: To observe the effects of dietary nitrates in the form of red spinach extract (RSE) on Division I collegiate baseball players following off-season training on health and performance measures. METHODS: Division I male baseball athletes (N=16; 20.5 ± 1.7y; 90.4 ± 10.5kg; 1.82 ± 0.61m) participated in this doClinuble-blind, placebo-controlled, randomized study. Before and after 11-weeks of offseason training, athletes were tested for body composition via dual x-ray absorptiometry, muscle thickness (MT) of the rectus femoris (RF) and vastus lateralis (VL) via muscle ultrasonography, resting heart rate (HR), and blood pressure (BP) in addition to a one-repetition maximum (1RM) on bench press and a maximal Wingate anaerobic cycle test (WAnT) to evaluate physical performance. After random assignment, participants consumed 2g of RSE, or a placebo (PL) (n = 8) daily for 12 weeks. Training consisted of 2-3 days per week of a triphasic undulating resistance training program in addition to sport specific activities. Changes were analyzed using a two factor (Time x Group) between-subjects repeated measures analysis of variance. RESULTS: There were no significant time x group interactions observed for any measure of body composition, physical performance, or health (all p > 0.05). However, a trend for increased peak power in the WAnT was found for the RSE group (p = 0.095; η² = 0.200). A main effect for time was observed for training improvements in bench press 1RM (p < 0.001; η² = 0.688), increased fat-free mass (p < 0.001; η² = 0.737) and MT for the RF and VL (p < 0.001), as well as a decrease in fat mass (p = 0.005; η² = 0.449) and body fat percentage (p = 0.002; η² = 0.512). Systolic BP exhibited an increase with both groups combined (p = 0.044; η² = 0.258) with no other significant changes in HR or BP were found. Compliance for supplement intake averaged 94.9% and no significant differences between groups were observed for macronutrient or calorie intake. CONCLUSION: Chronic dietary nitrate supplementation in the form of RSE may not improve indices of health, performance, or body composition in collegiate baseball athletes. [ABSTRACT FROM AUTHOR]