Influence of caffeine on selected manual manipulation skills.

To assess the effects of caffeine on selected manual manipulation skills 16 college-age (21 +/- 1.7 yr.) caffeine-naive women (less than 90 mg/day), having avoided products containing caffeine for four days, reported for testing eight hours postprandial. Measurements included duration and frequency of error for hand steadiness, duration and frequency error for following a tracing pattern, and duration of completing a tweezer-pin placement dexterity test. Caffeine doses of either 2.5 or 5.0 mg/kg body weight or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions using a double-blind format. A 2 x 3 repeated-measures analysis of variance and a Newman-Keuls post hoc test yielded a significant difference in hand steadiness error time from pre- to posttest for 5 mg/kg but not for 2.5 mg/kg or the placebo trial. For frequency of hand steadiness error, significant changes occurred for both 5.0 and 2.5 mg/kg. A dose of 5.0 mg/kg group resulted in significant differences in both tracing error time and error frequency. As both doses of caffeine significantly increased dexterity time, it was concluded that caffeine has detrimental effects on selected performance skills of young caffeine-naive women.