Meaning of walking

Cohen JA, Krishnan AV, Goodman AD, Potts J, Wang P, Havrdova E, Polman C, Rudick RA.The Clinical Meaning of Walking Speed as Measured by the Timed 25-Foot Walk in Patients with Multiple Sclerosis. JAMA Neurol. 2014 . doi: 10.1001/jamaneurol.2014.1895. [Epub ahead of print]

IMPORTANCE: Walking impairment, a common clinical manifestation of multiple sclerosis (MS), is often measured in clinical practice and clinical trials using the Timed 25-Foot Walk (T25-FW).
OBJECTIVE: To evaluate the relationship between walking speed measured by the T25-FW and the Physical Component Summary (PCS) score of the 36-Item Short Form Health Survey (SF-36) to better understand the clinical meaning of T25-FW walking speed in MS.
DESIGN, SETTING, AND PARTICIPANTS: We retrospectively analyzed data from 3 clinical trials (Natalizumab Safety and Efficacy in Relapsing-Remitting Multiple Sclerosis [AFFIRM], Safety and Efficacy of Natalizumab in Combination With Interferon Beta-1a in Patients With Relapsing-Remitting Multiple Sclerosis [SENTINEL], and International MS Secondary Progressive Avonex Controlled Trial [IMPACT]) that included T25-FW and SF-36 scores as outcomes in patients with MS. Patients had secondary-progressive MS and an Expanded Disability Status Scale score of 3.5 to 6.5 or relapsing-remitting MS and an Expanded Disability Status Scale score of 0 to 5.0.
MAIN OUTCOMES AND MEASURES:We evaluated retrospectively the relationship between the SF-36 PCS score and T25-FW walking speed at baseline and the 2-year changes from baseline.
RESULTS: Among all 2549 patients from the 3 trials, walking speed and SF-36 PCS score at baseline were significantly correlated (n = 2333; r = 0.48; P < .001). In placebo-treated patients at 2 years, the percentage of change from baseline in walking speed was significantly correlated with the change from baseline in SF-36 PCS score (r = 0.35; P < .001). Significant correlations between the change in SF-36 PCS scores and the percentage of change in walking speed at 2 years also were observed in groups receiving active treatment (r,  0.13-0.28; P ≤ .005). Among placebo-treated patients, 27.5% had a clinically meaningful worsening (≥5-point decrease) in SF-36 PCS scores during the 2 years. Walking speed declined by 21.8% in these patients after 2 years, but only by 5.4% in those without worsening of SF-36 PCS scores.
CONCLUSIONS AND RELEVANCE: In patients with MS, walking speed measured using the T25-FW correlated with SF-36 PCS scores such that a decline in walking speed of 20% to 25% corresponded to a clinically meaningful worsening of SF-36 PCS scores. A 20% to 25% decline in walking speed may be a clinically meaningful threshold for defining worsening using the T25-FW in MS clinical trials and for monitoring patients in clinical settings.

Timed walks are part of many clinical studies, but what does if mean. This study looked at the effect on timed 25meter walk and outcome and suggests that if you have a change of 20-25% this is an indicator of worsening