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EFFECT OF LOW VERSUS HIGH DOSE CAFFEINE “COFFEE NAP” ON COGNITION, REACTION TIME, AND ISOMETRIC STRENGTH

Abstract

BACKGROUND: Caffeine is an extensively studied stimulant that has been shown to improve alertness, reaction time, and exercise performance. Caffeine consumption immediately before a nap (i.e. a “coffee nap”) has been shown to elicit improvements in cognition, but the ideal caffeine dosage is not clear. In addition, effects of coffee naps on anaerobic exercise performance are unknown. Therefore the purpose of this study was to examine the effects of high (300 mg) vs low (100 mg) dose caffeine, in combination with a 15-min nap, on cognition, reaction time, and isometric strength. METHODS: College-age females were recruited via convenience sampling to come to the laboratory on three occasions. Participants were instructed to refrain from caffeine, nicotine, and alcohol 12-hr prior to each visit, and also instructed to refrain from vigorous exercise 24-h prior and sleep as many hours as is typical for them on each night prior to study visits. Upon arrival participants consumed three capsules that were identical in appearance: 300 mg (high), 100 mg (low), or none (placebo). Placebo capsules were filled with gluten-free corn starch. After consuming the supplement, participants waited 7.5 min, were taken to a cool dark room, and told to lie down and take a nap. After 15-min, participants were woken, waited 7.5 min, and the testing session then commenced, exactly 30 min post-supplementation. Participants first completed two trials of isometric mid-thigh pull with 2 minutes rest in between trials, then completed a Tower of London (ToL) cognitive test, and finally performed reaction time testing on a Dynavision light board. Order of the three testing sessions was counterbalanced, and supplementation protocol was double-blinded. One-way ANOVA was used to compare mean scores among the high, low, and placebo trials. RESULTS: There were no statistically significant differences in ToL score, reaction time or isometric strength among the three conditions (p>0.05). CONCLUSIONS: Neither high nor low dose caffeine in combination with a 15-min nap improved cognition, reaction time, or isometric strength in college-age females.

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