Introduction: Soft knee braces can be used to improve stability and lower limb loads in various activities such as jogging. Support stays are installed in soft knee braces to maintain knee posture. However, support stays often make the wearing of soft knee braces uncomfortable. To wear a soft knee brace continuously, it is necessary to minimize the frequency of use of the support stays to maintain comfortability for wearing. Thus, activities that require support stays should be investigated and selected. This study aimed to investigate the effects of support stays on jogging with a soft knee brace. Methods: In the experiment, 10 young males as participants were asked to perform 10 s of jogging on a treadmill (5.7 km/h) with different brace conditions (with and without support stays). Muscle activities of quadriceps femoris and hamstrings during jogging were measured using an electromyograph. Results: The results showed that there were no significant differences in muscle activities between patients with and without support stays. Conclusions: These results indicate possibility that support stays are not necessary in short-term jogging to maintain the comfort of wearing. In the future, the effect of the support stays of soft knee braces should be investigated for more difficult or longer activities. Acknowledgements: The authors received only soft knee braces for the experiments from Nippon Sigmax Co. Ltd.