Effect of Caffeine on Motor Performance by Caffeine-Naive and -Familiar Subjects

Abstract

The purpose of this investigation was to assess the effect of caffeine on selected manipulation skills by caffeine-naive and caffeine-familiar subjects. The subjects were 20 caffeine-naive (<90 mg/d) and 20 caffeine-familiar (>750 mg/d) college-age (21 ± 1.7 yr.) women. Measurements included steadiness error time and frequency, duration of tracing, error time and frequency, and dexterity. Doses of 2.5, 5.0 mg-kg⁻¹ body weight caffeine or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions. A 2 × 3 repeated-measures analysis of variance yielded a significant group difference for steadiness error time between the 5 mg·kg⁻¹ and 2.5 mg·kg⁻¹ dose and between 5 mg·kg⁻¹ and the placebo. For frequency of steadiness errors, the nonuser group posted significant gains for both 5.0 and 2.5 mg·kg⁻¹ over the placebo control. On tracing error time and error frequency, 5.0 mg·kg⁻¹ resulted in significant increases from both 2.5 mg·kg⁻¹ and the placebo group. In the caffeine-naive group, both doses of caffeine led to significant increases in dexterity time from the placebo, and the 5.0 mg·kg⁻¹ dose was significantly different from the 2.5 mg·kg⁻¹ trial. It was concluded that caffeine had detrimental effects on selected performance skills of caffeine-naive women but not in caffeine-familiar women.