Instrumented Assessment of Motor Performance Fatigability During the 6-Min Walk Test in Mildly Affected People With Multiple Sclerosis

Abstract

There are conflicting results regarding the changes in spatio-temporal gait parameters during the 6-min walk test (6MWT) as indicators of gait-related motor performance fatigability (PF) in people with Multiple Sclerosis (pwMS). To further analyze if gait-related motor PF can be quantified using instrumented gait analysis during the 6MWT, we investigated: (i) whether gait parameters recorded during the first or second minute were more stable and thus the better baseline to assess motor PF and (ii) if the minimum toe clearance (MTC) together with “classical” spatio-temporal gait parameters can be used to quantify motor PF in pwMS. Nineteen mildly affected pwMS [12 women/7 men; 47.8 ± 9.0 years; the Expanded Disability Status Scale (EDSS): 2.7 ± 1.0] and 24 healthy controls (HC; 15 women/9 men; 48.8 ± 7.6 years) completed the 6MWT equipped with inertial measurement units. Data were analyzed using the attractor method to compare the stability of gait parameters and, besides “classical” spatio-temporal gait parameters, the MTC was calculated as a potential new marker for motor PF in pwMS as this was shown in healthy older adults. It was found that (i) gait parameters were more stable in the second than in the first minute and (ii) gait-related motor PF could not be detected based on spatio-temporal gait parameters, including the MTC. Descriptive analysis indicated a decrease in MTC variability, which is assumed to be indicative for motor PF, toward the end of the 6MWT in some pwMS. Future studies should investigate gait parameters for the assessment of motor PF in pwMS recorded during more intense and/or longer walking protocols, taking the level of disability into account. Furthermore, using gait parameters recorded in the first minute of the 6MWT as a baseline for the assessment of motor PF should be avoided.

Between-Day Reliability of the Gait Characteristics and Their Changes During the 6-Minute Walking Test in People With Multiple Sclerosis

“…34 One may argue that the first minute of the 6MWT has more variability given the adaptation in the test and, therefore, is less stable compared to the second minute and may not be used to identify motor fatigability in pwMS. 44,58 Nevertheless, our results showed good to excellent reliability for gait characteristics in minute 1, which may address this issue raised elsewhere. Finally, we did not include all possible gait characteristics for all gait domains (eg, intra/inter-limb coordination or dynamic control asymmetry) or the calculation of the Lye in all possible planes (anteroposterior, medial-lateral, and vertical), which can give extra information on walking fatigability.…”

The increased perceived exertion during the six minute walking test is not accompanied by changes in cost of walking, gait characteristics or muscle fatigue in persons with multiple sclerosis

“…These findings are in line with previous studies describing that a decrease in walking speed is not adequate for describing walking fatigability in mildly disabled pwMS (EDSS 0-3.5). (Broscheid et al, 2022;Escudero-Uribe et al, 2019) Although increased gait variability is related to gait deterioration and self-reported fatigue in pwMS with mild disability, (Shema-Shiratzky et al, 2019;Zanotto et al, 2022) the increased RPE in our study was not accompanied by an increased gait variability. This is in line with the results from Crenshaw et al reporting no change in kinetic and kinematic variability before and after fatigue assessed with an increase in RPE.…”

“…The increased RPE during the 6MWT is in line with other studies including pwMS. (Hadouiri et al, 2021;Broscheid et al, 2022) This increment is suggested to be clinically significant when compared to other patient populations. (Ries, 2005) Therefore, it can be concluded that the 6MWT induced perceived exertion.…”

A step towards understanding fatigue and the cost of walking in persons with multiple sclerosis and rheumatoid arthritis

“…Previous studies showed that persons with mild impairments (EDSS range 1-4) walk slower during the 6-minute walk test, compared to control subjects. This slower walking speed during the 6-minute walk test is accompanied by shorter step lengths and lower cadences in all levels of disability, compared to control subjects Notably, walking speed decreases with increasing disability 42,43 . As described above, gait impairments are also affected by impaired neural control which stipulates the difference from gait impairments in persons with RA.…”

“…The increased RPE during the 6MWT is in line with other studies including pwMS. 42,199 This increment is suggested to be clinically significant when compared to other patient populations. 200 Therefore, it can be concluded that the 6MWT induced perceived exertion.…”