Does gait stability change over the 6-minute walk test in persons with Multiple Sclerosis? (R-12899)

Background and aim: Persons with multiple sclerosis (pwMS) show lower limb gait deficits (Comber 2017) and decreased gait stability compared to healthy control participants (Lin 2020). Previous research identified walking-related motor fatigue in pwMS by assessing the percentage change in distance walked between minute 6 and 1 of the 6-Minute Walk Test (6MWT)(Leone 2016). About onethird of PwMS showed this walking-related motor fatigue during the 6MWT. As gait instability is already evident in pwMS without clear gait impairments(Cofré Lizama 2020), it was questioned whether pwMS would show a similar fatigue related change in gait stability between minute 6 and 1 of the 6MWT. Therefore, the aim of this study was to assess whether pwMS present with altered gait stability at minute 6 compared to minute 1 of the 6MWT. Methods: Participants were included if they had: (1) a diagnosis of MS, (2) an age between 18–65 years, (3) a disease severity score from 1 to 5.5 on the Expanded Disability Status Scale (EDSS), (4) the ability to walk without walking aids. Participants were excluded if they had: (1) a relapse three months, (2) a lower limb fracture 12 months, or (3) lower limb botulinum toxin treatment six months prior to the measurement. Participants performed the 6MWT on the CAREN system (Motek, NL). They were equipped with the Human Body lower limb and trunk model to allow calculation of spatiotemporal parameters and kinematics during gait. Participants walked as fast as possible using the self-paced mode. Two familiarization rounds of 3min, including breaks, were provided. Medio-lateral and backward margins of stability (ML-MoS, BW-MoS) were calculated as the position of the extrapolated center of mass (XCoM) relative to the lateral malleolus and heel of the leading foot, respectively (Hak 2013). XCoM was defined as CoM plus its velocity times a factor: √(maximal CoM height/acceleration of gravity). Negative ML-MoS results in deviation from straight walking, and negative BW-MoS in interruption of forward progression. Average ML-MoS and BW-MoS were calculated for all steps in minute 1 and in minute 6. Additionally, MoS variability in the two directions (ML-sdMoS, BW-sdMoS) was determined over de MoS of all steps in minute 1 and in minute 6. A repeated measures ANCOVA was performed with 'time' as within factor, and the difference in walking speed between minute 6 and minute 1 as a covariate. Results: Preliminary results included data of 14 pwMS (Table 1). ML-MoS, BW-MoS and BW-sdMoS were not significantly different between minute 1 and minute 6 (ML-MoS: F=1.275,p=0.281; BWMoS: F=0.000,p=0.996; BW-sdMoS: F=0.569,p=0.465). ML-sdMoS did differ significantly between minute 1 and minute 6 (F=6.303,p=0.027). Conclusions: Our preliminary findings indicate that variability of margins of stability in the mediolateral direction increased significantly over 6 minutes of walking. Therefore, this measure of gait stability might be sensitive to assess walking-related motor fatigue in this population. Future research should confirm these preliminary results and should investigate possible asymmetry in gait stability between the most and least affected side.

Keywords:dynamic balance, fatigability, gait stability, multiple sclerosis

Disciplines:Rehabilitation sciences, Motor control