Step count accuracy of StepWatch and FitBit One among individuals with a unilateral transtibial amputation

Background: Step counts, obtained via activity monitors, provide insight into activity level in the free-living environment. Accuracy assessments of activity monitors are limited among individuals with lower-limb amputations. Objectives: (1) To evaluate the step count accuracy of both monitors during forward-linear and complex walking and (2) compare monitor step counts in the free-living environment. Study design: Cross-sectional study. Methods: Adult prosthetic users with a unilateral transtibial amputation were equipped with StepWatch and FitBit One. Participants completed an in-clinic evaluation to evaluate each monitor's step count accuracy during forward linear and complex walking followed by a 7-day step count evaluation in the free-living environment. Results: Both monitors showed excellent accuracy during forward, linear walking (intraclass correlation coefficients=0.97-0.99, 95% confidence interval=0.93-0.99; percentage error=4.3%-6.2%). During complex walking, percentage errors were higher (13.0%-15.5%), intraclass correlation coefficients were 0.88-0.90, and 95% confidence intervals were 0.69-0.96. In the free-living environment, the absolute percentage difference between monitor counts was 25.4%, but the counts had a nearly perfect linear relationship. Conclusion: Both monitors accurately counted steps during forward linear walking. StepWatch appears to be more accurate than FitBit during complex walking but a larger sample size may confirm these findings. FitBit consistently counted fewer steps than StepWatch during free-living walking. Clinical relevance The StepWatch and FitBit are acceptable tools for assessing forward, linear walking for individuals with transtibial amputation. Given the results' consistenty in the free-living enviorment, both tools may ultimiately be able to be used to count steps in the real world, but more research is needed to confirm these findings.