The effects of a moderate dose of caffeine on female endurance runners
Cokeley, Kimberly L. T.
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Eight trained (mean VO[sub 2] max = 56.4 ml kg^-1 min^-1 ± 6.1) collegiate female crosscountry runners (ages 18-26) ran two ten-mile treadmill runs (70% of VO[sub 2] max) after ingestion of caffeine (5 mg kg bw^-1, CAF trial) or a placebo (2 mg kg- bw^-1 PLA trial) lemonade solution. Respiratory exchange ratio (RER), blood glucose, and blood triglyceride levels were measured. Three of the subjects were dropped from all statistical analyses due to unreadable glucose blood samples. There were no changes in mean blood glucose and triglyceride levels of the CAF trials when compared to PLA trials(23.8 mg dL^-1 ± 24.7 vs. 11.6 mg dL^-1 ± 19.4 for glucose and 24.3 mg dL^-1 + 17.2 vs. 26.2 mg dL^-1 ± 17.9 for triglycerides). The mean RER recordings exhibited no change (first sample to last sample expressed in percent change) when comparing CAF to PLA trials (CAF RER = 7.20% ± 5.17 and PLA RER = 6.60% ± 2.95). A Wilcoxon nonparametric test was used to analyze RER percent changes, blood triglyceride and glucose measurements. Wilcoxon Matched-Pairs Signed-Ranks Test displayed no significant results between PLA trial and CAF trial with a Z = -.4045 for RER, Z = - 1.2136 and Z = -.4045 for glucose and triglycerides respectively. The results of this investigation illustrate that there is no ergogenic effects of a 5 mg kg bw^-1 dose of caffeine on RER, blood glucose levels, or blood triglyceride levels in female collegiate runners.