Increases in volume of the lower extremities have been demonstrated in some exercises of short duration and varied intensities. The purpose of this study was to determine if running on a treadmill for 15 minutes increased volume of the foot and ankle when compared with walking. Twenty-one volunteers walked during one treatment session and ran during another session. Volumetric measurements were taken before and after each exercise. A change score was calculated for each subject for both sessions. A t test for related measures demonstrated a statistically significant difference (p < or = 0.05), with a larger volume occurring after running. Increases in volume most likely would not create problems in healthy individuals. Increases, however, may be harmful in individuals with circulatory disorders or with edema as a sequela of a foot or ankle injury.