Accuracy of 2 Activity Monitors in Detecting Steps in People With Stroke and Traumatic Brain Injury

George D. Fulk; Stephanie A. Combs; Kelly A. Danks; Coby D. Nirider; Bhavana Raja; Darcy S. Reisman

doi:10.2522/ptj.20120525

Figures

Figure.

Bland-Altman plots: (A) Bland-Altman plot demonstrating step count agreement between actual steps taken counted from video and StepWatch Activity Monitor estimated steps. Solid bold line is the mean difference between video counted steps and StepWatch Activity Monitor estimated steps, dashed lines are the 95% confidence interval. (B) Bland-Altman plot demonstrating step count agreement between actual steps taken counted from video and Fitbit Ultra activity monitor estimated steps. Solid bold line is the mean difference between video counted steps and Fitbit Ultra estimated steps, dashed lines are the 95% confidence interval. (C) Bland-Altman plot demonstrating step count agreement between actual steps taken counted from video and Yamax Digi-Walker SW-701 pedometer estimated steps. Solid bold line is the mean difference between video counted steps and Yamax Digi-Walker SW-701 pedometer estimated steps, dashed lines are the 95% confidence interval. (D) Bland-Altman plot demonstrating step count agreement between actual steps taken counted from video and Nike+ Fuelband activity monitor estimated steps. Solid bold line is the mean difference between video counted steps and Nike+ Fuelband estimated steps, dashed lines are the 95% confidence interval. Note that the scale on the y-axis is not the same between the graphs.

Tables

Table 1.

Participant Characteristics

Table 2.

Accuracy of Different Activity Monitors in All Participants (N=50)^{^a}

↵^a ICC=intraclass correlation coefficient, 95% CI=95% confidence interval, SAM=StepWatch Activity Monitor.

Table 3.

Accuracy of the Different Activity Monitors in Participants With Stroke (n=30)^{^a}

↵^a ICC=intraclass correlation coefficient, 95% CI=95% confidence interval.

Table 4.

Accuracy of the Different Activity Monitors in Participants With TBI (n=20)^{^a}

↵^a ICC=intraclass correlation coefficient, 95% CI=95% confidence interval.

Table 5.

Pearson Correlation Coefficients (r) for Relationship Between Activity Monitors' Accuracy and Clinical Variables^{^a}

↵^a SAM=StepWatch Activity Monitor.
^b Significant relationship, P<.05.

Supplementary Data

eTables

Files in this Data Supplement:

eTables (PDF) (25 KB) - This PDF contains the following eTables:
- eTable 1. Comparison of Features of Various Activity Monitors
- eTable 2. Accuracy of the Different Activity Monitors in Participants With Gait Speed of 0.58 m/s

The Bottom Line

What do we already know about this topic?

Activity monitors utilize small sensors, such as accelerometers and gyroscopes, to estimate daily stepping activity, calories burned, and other activity-related metrics of the wearer. The accuracy of many commercially available activity monitors geared toward consumer or patient use, however, is not known.

What new information does this study offer?

This study examined the accuracy of 2 activity monitors, the Fitbit Ultra and the Nike+ Fuelband, in estimating stepping activity in people with stroke and traumatic brain injury. These measurements were compared to the measurements made by a pedometer and a research-grade activity monitor, the StepWatch Activity Monitor. The study found that the StepWatch Activity Monitor was the most accurate, followed by the Fitbit Ultra. The Nike+ Fuelband and the pedometer were not accurate in estimating steps.

If you're a patient or a caregiver, what might these findings mean for you?

If you have a stroke or traumatic brain injury and can walk at speeds of 0.58 m/s or more, the Fitbit Ultra activity monitor may be a low-cost way that you can accurately measure and self-monitor walking activity in level, predictable environments.