The purpose of this study was to investigate the effect of heel spring(difference of heel height and forefoot height) in an otherwise non-supportive running shoe to assess the effect on ankle joint kinematics and muscle activity during running. fifteen healthy well-trained male runner volunteered for the study, Subjects were tested on a treadmill while running in minimalist running shoe(ECCO, biom) with three difference inserts: Up: 14 mm higher than forefoot, flat: heel and forefoot level, Down: heel 5 mm lower than forefoot. knee and ankle kinematics were analysed and touch down angle, minimum and maximum values and angular velocities extracted after butter worth low pass filtering at 15 Hz. on average the whole sample altered maximum ankle angle(dorsifleion) during stance systematically by showing 5 degree less maximum dorsifelexion in the up insole and 2 degree grated dorsifelexion in the down sole compared to flat. No differences in any EMG parameter were observed.