Walking With a Weighted Pelvic Belt or With an Equivalent Pure Downward Force on the Pelvis: Are These Different?

In a previous study, a tethered pelvic-assist device (TPAD) was used to successfully retrain crouch gait in children with cerebral palsy by applying a downward force on the pelvis while walking on a treadmill. While the results of this study were promising, an important issue was to translate this training to the children in a more practical manner. This motivated the question in this letter whether a different intervention could result in similar improvements in the gait as seen with the TPAD. This is the motivation for this study, which compares the biomechanical differences in walking under the following two conditions. 1) The TPAD applies a pure downward force on the pelvis using tethers. 2) A weighted pelvic belt is used to apply the same downward force on the pelvis. In this case, the weight belt also increases the mass at the pelvis. A total of ten healthy subjects performed two separate experiments while walking on an instrumented treadmill. The whole-body kinematics were recorded using a motion-capture system, and the ground reaction forces were measured by the force plates embedded in the treadmill. We found no significant differences in the kinematic gait parameters of healthy subjects when the downward force, equivalent to 15% body weight, applied by the TPAD was replaced by a weighted pelvic belt having 15% body weight. However, the activation of the gastrocnemius muscle and the estimated maximum ankle torque, predicted by an inverted pendulum mathematical model, during the single support phase of walking, showed a higher increase with the weight belt when compared to a pure downward force. Thus, the weight belt, because of its simplicity, must be further considered as a more convenient candidate to translate the results of TPAD in children with cerebral palsy who suffer from crouch gait.