RH12 Standing Data Disproves Biomechanical Mechanism for Balance-Based Torso Weighting

Thursday, May 30, 2013
Ajay Crittendon, BS , Graduate Program in Physical Therapy, San Francisco State University, San Francisco, CA
Danielle O'Neill, BS , Graduate Program in Physical Therapy, San Francisco State University, San Francisco, CA
Diane D Allen, PT, PhD , Graduate Program in Physical Therapy, San Francisco State University, San Francisco, CA
Gail L Widener, PT, PhD , Physical Therapy, Samuel Merritt University, Oakland, CA
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Background: Balance-Based Torso Weighting (BBTW) has improved gait speed and balance measures in people with multiple sclerosis (MS). While the underlying mechanism behind BBTW has not been identified, a biomechanical explanation has been suggested. Changes in center of pressure (COP) during quiet standing may directly coincide with the direction of weight placement.

Objectives: Investigate the changes in COP with and without BBTW in people with MS and healthy controls in comparison with the average weight location in the anterior-posterior or right-left directions.

Methods: 38 people, 20 with MS (EDSS mean 4.1, range 2-6) and 18 healthy controls matched for age, height and weight, stood statically for 10 seconds with feet together on a force plate in 4 conditions: eyes open and eyes closed and with and without BBTW. Weight placement on the torso was recorded and compared to the direction of COP change from the unweighted to the weighted conditions. These data were collected as part of a larger motion analysis study investigating gait changes with BBTW.

Results: Participants in the healthy control and MS groups were not significantly different in age, height and weight (t-test, p>.05). Average BBTW weighting was 1.38 pounds (0.9% body weight) and was not statistically different between groups (t-test, p>.05).  Weight placement (anterior, posterior, or right, left) was compared with COP directional data for the 4 conditions for both groups. COP displacement did not reflect BBTW weighting locations (Chi-square, p<.0001). Differences between groups revealed fewer matches between COP changes and location of weights for people with MS than for healthy controls, although this did not reach statistical significance (Chi-square, p=.0512). However, BBTW was still effective at improving gait velocity (cm/s) in people with MS (t-test, p=.004) compared to gait without weight.

Conclusions: While BBTW has been shown to increase gait speed in people with MS, these data disprove the hypothesis of a strictly biomechanical mechanism underlying its effectiveness. Further study is needed to investigate other possible mechanisms for this promising intervention.