Interactive Effect of Caffeine and Attention Focus on Postural Stability of Individuals with Different Levels of Physical Activity

The aim of this study was to determine the interactive effect of caffeine and attention focus on the postural stability in subjects with different levels of physical activity. 20 male students were divided into two equal groups (physically active and inactive) by the international physical activity questionnaire. Their postural sways were gathered from a force plate system during two 30-second trials with a 1-minute rest interval with no interventions in the pretest and in internal attention focus (attention to the lower extremity) and external attention focus (attention to a point on the front wall) conditions. On the second day of the experiment, subjects in both groups received 5 mg of caffeine per kg of body weight and the postural stability test was conducted under internal and external attention focus conditions after 30 minutes. The results of ANOVA with repeated measures at α=0.05 showed significant increases in the postural sways of both groups in internal and external conditions. Also, the caffeine intervention significantly increased the postural sways of both groups in internal and external conditions. Furthermore, active subjects showed less postural sways in different conditions than the inactive group. Regardless of the focus of attention, caffeine causes more postural sways in both groups with different levels of physical activity through affecting the sympathetic system and increased muscle contractions and tremor. In future studies, other factors such as individual differences in response to caffeine intake or its effect on tasks along with postural disturbances should be considered.