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 of children with Cerebral Palsy by applying a downward force on the pelvis during walking on a treadmill. While the results of this study were promising, an important issue was translating these results to special needs children with crouch gait using simpler alternative procedures. This motivates the present study to compare the biomechanical differences in walking under two conditions: (i) the TPAD applies a pure downward force on the pelvis using tethers, and (ii) a weighted pelvic belt is used to apply the same downward force on the pelvis. In the second case the weight belt also increases the mass at the pelvis. Ten healthy subjects performed two separate experiments while walking on an instrumented treadmill. The whole-body kinematics was recorded using a motion capture system and the ground reaction forces were measured by force plates embedded in the treadmill. We found no significant difference in the actual gait parameters of healthy subjects when the downwards force, equivalent to 15% body weight, applied by the TPAD was replaced by a weighted pelvic belt of 15% body weight. However, the estimated maximum ankle torque, predicted by an inverted pendulum mathematical model, during the single support phase showed a higher increase during walking with the weight belt when compared to a pure downward force. This suggests that the weight belt, due to its simplicity, may be a better medium to translate the results of TPAD in children with cerebral palsy who have a crouch gait.