PURPOSE: The purpose of this study was to investigate the change of triceps surae activation during heel raise test in standing among knee flexion angles($0^{circ}C$, $30^{circ}C$, $45^{circ}C$, $60^{circ}C$). METHODS: Twenty healthy individuals performed unilateral plantarflexion in standing with $0^{circ}C$, $30^{circ}C$, $45^{circ}C$, $60^{circ}C$ knee flexion. Activity of medial gastrocnemius(MG), lateral gastrocnemius(LG), soleus(Sol) was recorded with surface electromyography(EMG). RESULT: The muscle activations induced the four different positions were compared and results showed that was significant difference MG and LG while the angle increase from $0^{circ}C$ to $30^{circ}C$, $45^{circ}C$, $60^{circ}C$ but Sol did not show significant differences in every angle. CONCLUSION: This study suggest that $30^{circ}C$ knee flexion is required to induce a significant mechanical disadvantage of gastrocnemius.