The purpose of this study was to investigate the effect of running economy and energy return in lower extremities according to the increase of bending stiffness of the shoes, furthermore to investigate the relationship between running economy and energy return for the improvement of sports performance. Subjects employed for this study were 10 healthy male college students who have not had the experiences in lower extremities injuries. Four different kinds of shoes in bending stiffness as with 0.56 N/mm, 0.74 N/mm, 0.96 N/mm, 1.21N/mm were used respectively. 3-D cinematography and pulmonary gas analyzer were utilized for energy return and energy consumption data during running according to the increase of bending stiffness of the shoes to obtain the following results. As the bending stiffness of running shoes increased, the statistical significance were not founded, however, the tendency of decrease in max. flexion moment and power, increase in max. extension moment and power in lower extremity joint were showed. Joints energy showed no statistical significance in phase 1, however, the tendency of lesser absorbtion as the bending stiffness of running shoes increased were showed. More energy were generated as the bending stiffness of running shoes increased in phase 2 with no statistical significance. Energy economy increased according to the increase of bending stiffness of running shoes. Negative correlation were showed between flexion moment of hip joint and energy consumption(p<0.05). Slightly higher degree of correlation between max. flexion power of hip and ankle joint and energy consumption were showed without statistical significance. Negative correlation were showed between joints energy and energy consumption for ankle joint in phase 1(p<0.05).
