Activity trackers are not valid for step count registration when walking with crutches

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Wearable Sensors

Background:

• Activity trackers are proposed for rehabilitation, particularly after total knee arthroplasty (TKA), to monitor physical activity.
• Patients often use crutches post-TKA, necessitating reliable activity data during this phase.

Purpose of the Study:

• To assess the concurrent validity of two activity trackers (Garmin Vivofit 3 and Nokia Go) for step counting.
• To evaluate tracker performance at different body locations (wrist, waist) during normal gait and gait with crutches.

Main Methods:

• Thirty healthy participants completed 400m walks under normal gait and with one or two crutches.
• Step counts from trackers were compared against a manual "gold standard" count.
• Validity was assessed using Intraclass Correlation Coefficients (ICC), paired t-tests, and Bland-Altman plots.

Main Results:

• Both trackers demonstrated good to excellent inter-device reliability during normal gait.
• Concurrent validity was established for normal gait, with slightly better performance for the Garmin at the wrist.
• During gait with crutches, validity was not established, with wide limits of agreement and poor ICC values, irrespective of tracker placement.

Conclusions:

• Activity trackers do not provide valid step count data during crutch-assisted gait.
• The findings highlight limitations for using activity trackers in post-operative rehabilitation settings, such as TKA recovery.
• Clinicians should be aware of these limitations when setting goals or monitoring patients using activity trackers during this phase.