Dark focus of accommodation and nervous system activity.

The purpose of this study was to evaluate the relation between physical exercise and dark focus of accommodation. Varsity intercollegiate runners (N = 12) participated in the experiment. Measurements of dark focus and pulse rates were taken before and after running 400 m. The hypothesis that arousal of the sympathetic nervous system through physical exercise would result in an inward shift of the dark focus was investigated. A repeated measures t-test was used to analyze the difference of dark focus between resting and running. These findings suggest that arousal of the sympathetic nervous system does have a significant effect on dark focus of accommodation.