Kinematic and kinetic analysis during forward and backward walking

Backward walking (BW) is a recently emerging exercise. However, limited studies exist regarding the motion analysis of BW compared with that of forward walking (FW). The present study identified the mechanisms of BW through kinetic analysis and focused on BW time-reversed data. A three-dimensional motion capture system was used to acquire the joint movements and to calculate the joint moments and the powers during walking. Ground reaction force curves were acquired from force plates. Each participant performed 10 FW trials and 40 BW trials with bare feet. All data were analyzed using paired t-tests (p < 0.05) to verify the significant differences between FW and BW. In BW, since the progress is in the direction in which the person cannot see, the walker's speed is generally decreased compared to FW. As a result, the stride characteristics for each respective activity showed significant differences. The characteristics of angular displacement in all joints were almost identical in FW and time-reversed BW. However, selected crucial points of joint angles were significantly different. The moment pattern of the ankle joint was very similar in FW and time-reversed BW. In the knee and the hip joint, the joint moment pattern of time-reversed BW was simpler than FW. The joint power patterns of the ankle, the knee and the hip were different in FW and BW. An original finding of this study was that the main propulsion and shock absorption joint during BW is the ankle joint. The knee and hip joint did not generate propulsion power.

► The characteristics of angular displacement in all joints were almost identical in FW and time-reversed BW. ► The characteristics of kinetics of BW in all joints were simpler and smaller than those of FW. ► EMG pattern shift and simpler shape of knee and hip joint moments could be explained as the modification of neural mechanism. ► Thus, BW could be helpful to the motor learning caused by the modification of the neural mechanism.