Ecological validity of walking capacity tests following rehabilitation in people with multiple sclerosis.

Background: Walking capacity tests are commonly used to evaluate interventions aiming at reducing walking impairment in people with multiple sclerosis (pwMS). However, their ecological validity has recently been questioned. The aim of the present study was to investigate the ecological validity of the 2- and 6-minutes walking tests (2MWT and 6MWT) and the timed 25-foot walk (T25FW) after 28 days of multidisciplinary inpatient rehabilitation (MIR) in pwMS using accelerometry.

Methods: PwMS wore an accelerometer on 7 consecutive days within a 14-day period prior to MIR, performed 2/6MWT and T25FW at the beginning and at the end of MIR, followed by another 7 consecutive days of accelerometry.

Results: Significant improvements in 2/6MWT and T25FW after MIR in a cohort of 76 pwMS (mean age = 47.9, SD 8.3 years) were overall correlated to a significant gain in everyday life mobility (total steps/day). However, the correlation was strongly dependent on pre-existing walking disability defined by EDSS and only pwMS with "mild" walking impairment (EDSS 2-3.5) were able to transfer benefits measurable by walking capacity tests into improved everyday life mobility, while pwMS with "moderate to severe" walking disability (EDSS 4-6.5) were not.

Conclusion: Ecological validity of changes in walking capacity tests following MIR is strongly dependent on pre-existing walking impairment.