This paper evaluated quantitative effects of vertical alignment of leg on knee trajectory, pedaling power and speed during pedaling. In general, traditional cycle fittings consisted of optimization of frame size using cyclist`s body size (static fitting) and pedaling efficiency using vertical leg alignment (dynamic fitting) during pedaling. Though both fitting methods were adopted in this study, static fitting was used for all test conditions thus the effects of dynamic fitting were evaluated. Fifteen male subjects (height 172.9 cm, weight 65.2 kg, age 25.3 years) were participated in this study. For the comparison of pedaling performance between before and after fitting, two min. submaximal pedaling tests with constant pedaling load were conducted. Results showed that the range of motion of medio-lateral direction at the knee, which represented pedaling trajectory, and the coefficient of variance of pedaling power were decreased significantly. From these results, it is believed that dynamic fitting showed positive effects such as increased pedalling kinematic stability and kinetic efficiency. Further study is necessary to evaluate the effects of the dynamic fitting through enough subjects with considering pedaling force and muscle activation.