Conventional habitual physical activity (HPA) statistics are poor measures of capacity due to variability in activity behaviors in people with multiple sclerosis (MS), according to a recent study. However, the maximum step rate (MSR) and habitual walking step rate (HWSR) are valid, specific measures of real-world capacity that capture subjects’ highest step rate and preferred step rate, respectively. 88 MS and 38 control subjects completed timed walks and patient-reported outcomes in clinic, then wore an accelerometer for 7 days. 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. Researchers found:

• The 6-minute walk (6MW) step rate correlated most strongly with MSR (r=0.863) and HWSR (r=0.815) rather than average daily steps (r=0.676).
• The combination of MSR and HWSR correlated more strongly with the 6MW step rate than either measure alone (r=0.884).
• The MSR overestimated the 6 MW step rate (μ=10.4), whereas the HWSR underestimated it (μ=−18.2).