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

Abstract

Objective To test a proposed mechanism for the effect of Balance-Based Torso-Weighting (BBTW) in people with multiple sclerosis and healthy controls. The application of light weights to the trunk may result in a biomechanical shift of postural sway in the direction of weighting, mechanically facilitating maintenance of center of mass over the base of support. Design Non-randomized controlled trial Setting motion analysis laboratory Participants 20 participants with multiple sclerosis (average EDSS 4.1) and 18 sex-, age-, height- and weight-matched controls Intervention Light weights strategically placed according to the BBTW protocol were applied to all participants following at least three walking trials and 10 seconds of quiet standing with feet together eyes open (EO) and eyes closed (EC). Measures were repeated after weighting. Main Outcome Measure Force plate center of pressure (COP) changes greater than one standard error of measurement (SEM). Results With BBTW, people with MS had larger maximum changes in COP than healthy controls in the left-right direction but not in the anterior-posterior direction. COP changes greater than one SEM occurred in the same direction of weighting 20% of the time (95% confidence interval 5%, 34%), ranging from 10% to 28% across conditions and directions of postural sway. Direction of greatest weight placement did not match the direction of change in average COP in the majority of participants with multiple sclerosis or the healthy controls in EO or EC conditions (p<.0001). Conclusions If BBTW worked via a biomechanical shift of the center of mass, COP changes should match the direction of greatest weighting with BBTW. Our data allowed us to reject this hypothesis. Future research may explore alternative mechanisms of action underlying this intervention.

Effects of Torso-Weighting on Standing Balance and Falls During the Sensory Organization Test in People with Multiple Sclerosis

“…Torso-weighting differs from the traditional rehabilitative method of placing heavier weights at the trunk or limbs to help control movement 21 because it uses light weights, generally less than 2% of body weight, strategically placed based on evidence of imbalance or asymmetry of response. 19 Previous work has shown that immediately after torso-weighting, people with MS have improved static stability with decreased sway when standing with eyes open and closed, 5,20 increased ability to resist rotational forces while standing, 5 and more optimized variability of postural sway. 22 Torso-weighting has resulted in improved dynamic stability in sit-to-stand transfers and walking 20 and in increased gait velocity, cadence, and percentage of gait cycle spent in single-limb support in people with MS. 23 However, to our knowledge, the effect of torsoweighting on falls in people with MS has not yet been studied.…”

“…The nonweighted testing always preceded the weighted testing because people have shown carryover effects of the Balance-Based Torso-Weighting for hours after the weights have been removed. 5,20 Disease Steps 24 was rated by a single researcher (G.L.W.) during the first set of clinical tests.…”

“…Future studies are planned in which nonweighted and weighted testing will occur in separate sessions to mitigate for the potential carryover effects lasting up to several hours after weights are removed. 5,20 In this study, we reduced the impact of test familiarity on immediate performance by eliminating trial 1 when analyzing equilibrium scores and fall frequency. Another limitation was the absence of an ization in this single session.…”

“…3,4 Imbalance occurs in 87% to 94% of people with MS. 3,4 Balance problems can increase the chance of falling compared with controls. 5 Between 52% and 71% 6,7 of younger and middle-aged people with MS report having fallen recently, with up to 48% having multiple falls 7 ; 41% of all falls and 50% of falls in those older than…”

Gait Changes with Balance‐Based Torso‐Weighting in People with Multiple Sclerosis

“…For instance, a weight placed anteriorly to the left may counter inability to hold against a rotational force at the pelvis. The mechanism for the effect of BBTW is unknown, although sensory augmentation may play a role because people do not mechanically shift in the direction of weighting (Crittendon et al, 2014). Previous research has shown promising results.…”