The choice of running shoes contributes to the running economy（RE）, which is one of the important capacities for distance running performance. Recently, the development of running shoes with high compliance and resilience midsoles and integrated carbon-fiber plates has led to improvements in long-distance running performance. This study aimed to compare the biomechanical variables when wearing carbon-fiber plate running shoes（Nike ZoomX Vaporfly Next%: VN）and conventional running shoes （Nike Zoom Streak 7: ST7）and investigate the factors contributing to the improvement in RE. 10 long-distance runners evaluated the RE, lower limb joint angle, vertical ground reaction force, ground contact time, step frequency, and surface electromyogram with wearing two running shoes（VN and ST7）. Notable results were that 1）the VN was a 5.7% on average better RE than the ST7, 2）the ankle joint was more in a plantar flexion position throughout the support phase in the VN than the ST7. Other biomechanical variables were not significantly different between the running shoes. In addition, the most
RE improvement（17.2%）runner with the VN compared to the ST7 showed > 1SD difference in dorsi-flexion of the ankle joint, flexion of the hip joint, and an internal rotation of the ankle joint compared to an average of the ten runner’s lower limb joint angle at the support phase. On the other hand, one runner decreased RE（4.3 %）when wearing the VN compared to the ST7. This runner showed > 1SD difference in an internal rotation of the knee joint throughout the support phase compared to an average of the ten runner's lower limb joint angle. These results suggest that the VN provide superior energy returns, which contributes to the improvement of RE, but not all runners can benefit from the improvement of RE by wearing the VN.