Force adaptation in human walking with symmetrically applied downward forces on the pelvis

The application of external constraints and/or applied forces during movement can lead to reactive as well as adaptive changes in human motion. Previous researches in the literature have usually focused on adaptation in human kinematics when external forces were applied using exoskeletons during the swing phase of gait. This work aims to study adaptation in human walking when externally applied forces are present on the pelvis both during the swing and stance phases of the gait. A novel tethered pelvic assist device (TPAD) was used to passively apply downward forces on the human pelvis while walking. During the experiment, healthy subjects walked on a treadmill at a constant speed while their kinematics and foot pressure data were recorded. Data analysis revealed that the healthy subjects exhibited both reactive as well as adaptive changes in their gait parameters. The immediate response of the subjects was to increase their hip flexion to clear their foot off the ground as they were unable to lift their pelvis to their usual height during normal motion. Seven out of eight subjects in the study resisted the downward forces to move their pelvis up. Eventually, they reached a level of downward force that they could sustain over the training. This adaptation to the downward force was reflected in the heel peak pressure values during the cycles of the gait. On removing the tethers, aftereffects in heel peak pressure during the gait cycles were observed.