No. There is no concrete evidence that running or any other type of exercise causes varicose veins, spider veins or venous insufficiency. The calf muscles are the “venous pumps” that push the venous blood against gravity back up to the heart. Therefore, any activity that engages the calf muscles prevents stagnant blood. Theoretically, one might envision that the pounding of the column of blood in the veins from the deceleration of the foot and leg hitting the ground while running might damage the one-way valves, but there is no medical evidence that such harm takes place.