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. 2018 Jan:59:211-216.
doi: 10.1016/j.gaitpost.2017.10.015. Epub 2017 Oct 16.

Real-world walking in multiple sclerosis: Separating capacity from behavior

Matthew M Engelhard  1 , Stephen D Patek  1 , John C Lach  2 , Myla D Goldman  3
Affiliations

Real-world walking in multiple sclerosis: Separating capacity from behavior

Matthew M Engelhard et al. Gait Posture. 2018 Jan.

Abstract

Background: Habitual physical activity (HPA) measurement addresses the impact of MS on real-world walking, yet its interpretation is confounded by the competing influences of MS-associated walking capacity and physical activity behaviors.

Objective: To develop specific measures of MS-associated walking capacity through statistically sophisticated HPA analysis, thereby more precisely defining the real-world impact of disease.

Methods: Eighty-eight MS and 38 control subjects completed timed walks and patient-reported outcomes in clinic, then wore an accelerometer for 7days. HPA was analyzed with several new statistics, including the maximum step rate (MSR) and habitual walking step rate (HWSR), along with conventional methods, including average daily steps. HPA statistics were validated using clinical walking outcomes.

Results: The six-minute walk (6MW) step rate correlated most strongly with MSR (r=0.863, p<10-25) and HWSR (r=0.815, p<10-11) rather than average daily steps (r=0.676, p<10-11). The combination of MSR and HWSR correlated more strongly with the 6MW step rate than either measure alone (r=0.884, p<10-14). The MSR overestimated the 6MW step rate (μ=10.4, p<10-7), whereas the HWSR underestimated it (μ=-18.2, p<10-19).

Conclusions: Conventional HPA statistics are poor measures of capacity due to variability in activity behaviors. The MSR and HWSR are valid, specific measures of real-world capacity which capture subjects' highest step rate and preferred step rate, respectively.

Keywords: Accelerometry; Gait disorders/ataxia; Habitual physical activity; Habitual walking performance; Multiple sclerosis; Outcomes research; Six-Minute walk.

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Conflict of interest statement

CONFLICT OF INTEREST STATEMENT

MME, SDP, and JCL have nothing to report. MDG reports grants from Biogen Idec, grants from Novartis, other from Acorda, other from Biogen Idec, other from Novartis, personal fees from Novartis, and personal fees from Sarepta outside the submitted work.

Figures

Figure 1
Figure 1
6MW step rate and distance correlate more strongly with maximum step rate than average daily steps.
Figure 2
Figure 2
Walking step rates are lower than 6MW step rates (p<10−5), though the two are strongly correlated (left). HR elevation during the 6MW correlates (p<10−4) with the increase in step rate above their habitual walking step rate (right).
See this image and copyright information in PMC

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