For lower limb amputees, the socket fit is affected by the physical activity performed during the day. The majority of the studies in this field include only transtibial amputees and do not examine the effects of this variable. This paper aims to determine the effect of physical activity on the volume of the residual limb (RL), the comfort, and the symmetry of gait in traumatic transfemoral amputees. RL volume and gait data of five individuals were obtained at the first time of the day and after three sessions of treadmill walking. The ratio symmetry index of selected points of gait parameters was calculated. A short comfort test was used after each session. Data were analyzed throughout the tests within each subject, and statistical analysis was performed. After the physical activity, a tendency toward volume decrease was found on almost all subjects, although it was not significant. Transfemoral amputees may have smaller volume variations than transtibial after treadmill walking tasks. Significant difference was found on the symmetry index of “swing phase (SWP).” The values of gait symmetry were consistent with previous findings regarding transfemoral amputees. The lowest symmetry was noticed on the ankle kinematics. The comfort did not significantly change with the selected amount of physical activity. In subsequent research, it is recommended to increase the intensity or time of physical activity and/or increase the number of participants. These results can help the understanding of how the socket/RL interface behaves, which can improve the design and prescription of prosthetic components.