This study documents changes in momentary distribution of forces under the foot, comparing barefoot gait to that with heel cups, medial arch supports, and low-dye taping. Cholesterol crystal force plate analysis and a computerized Kistler force platform were used in the study. Low-dye taping or a heel cup significantly diminished the duration of forces under the midfoot, medializing the instant center of forces. A medial arch support shifted the instant center of forces laterally, though it did not diminish the duration of forces under the arch. The relationship between these alterations of force distribution and the treatment of common runner's ailments such as plantar fasciitis, posterior tibial tendinitis, metatarsalgia, and shin splints is much clearer in the light of these results.