Study: Phone App mSteps Accurately Measures Distance Walked

mSteps, a new phone app, could be used to precisely measure the outdoor walking distance of people affected by multiple sclerosis (MS), a recent study shows.

The study, “The mSteps pilot study: Analysis of the distance walked using a novel smartphone application in multiple sclerosis,” was published in the Multiple Sclerosis Journal. 

Clinical studies in MS often involve measuring walking distance to assess a person’s exercise capacity/mobility level. The Expanded Disability Status Scale (EDSS), commonly used in clinical research and clinical practice as a disability measure, relies on an accurate measurement of distance walked. The trundle wheel is the standard tool for acquiring this measurement.

However, if the patient is incapable of performing the test or the room does not have the right conditions, the patient often is asked to estimate the distance walked.

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Several smartwatches and phone apps have been used to accurately track distances outdoors. However, they have not been tested and validated for use in people with MS. These devices rely on a fixed-stride length, which may be less precise for people with altered walking patterns, such as MS patients.

Now, researchers from University College London (UCL) Queen Square MS Centre (QSMSC), in the U.K., developed and tested a phone app, called mSteps, as a potential reliable tool to measure the distance walked by people with MS, both indoors and outdoors, and to facilitate EDSS measurements.

mSteps was built for the iPhone platform and includes “a clock timer and distance counter, which automatically stops when the person stops moving for more than 20 seconds. Both of these counters restart when the person starts moving again,” the researchers wrote.

The MS phone app uses the phone’s inbuilt GPS to measure outdoor walking distances, while the indoor distance measurement was obtained through a Wi-Fi positioning in a mapped corridor.

Researchers conducted two studies: a pilot study to test the reliability of the measured distance walked by a smaller group of patients with mSteps; and a validation study with a larger group and comparison of the app’s accuracy with the trundle wheel.

Pilot study design

The pilot study included 25 MS patients recruited from studies already being run by the UCL QSMSC (group 1) and 10 people without MS (group 2, control group). The validation study had 100 MS patients recruited from studies in the same research center (group 3).

Groups 1 and 3 had a median EDSS score of 6, and ages ranging from 50 to 60 years. The group 2 had no known mobility impairment and a median age of 30. Group 1 performed only the indoor measurement due to unfitting weather conditions. Group 2 performed the test indoors and outdoors, and group 3 tested outdoors.

Participants were asked to stand still during the set-up of a bracelet on the arm and mSteps activation. For the pilot test, they were asked to walk at a comfortable pace without prolonged rest for 25 feet (7.62 meters), and for the validation test, for as long as they could. A researcher walked alongside the participants in both studies with a trundle wheel.

In the pilot study, the measurement given by mSteps was considered reliable if the difference to the trundle wheel result was less than 1.52 meters (20% of the 7.62 meters). The team found the outdoor tracking in group 2 to be within this limit, while the indoor results for groups 1 and 2 did not agree with the difference.

“The results from the pilot study conducted outdoors displayed a very good agreement between the application and the trundle wheel in the control cohort,” the researchers wrote. In turn, the indoor pilot study “results showed there was a lack of agreement between the mSteps application and the trundle wheel. This confirms that the indoor walk functionality of mSteps was neither reliable nor accurate.”

“The indoor functionality was built using the phone’s inbuilt accelerometer and Wi-Fi positioning. Indoor positioning systems are still being developed throughout the world, and as such there isn’t a ‘best’ solution yet,” the team added.

In the validation study, the app measurements were defined as accurate if the difference with the wheel values was less than 5 meters. Group 3 results met this limit.

“In the pilot outdoors control study, we demonstrated accuracy and reliability of the mSteps phone application and we then went on to validate this in a group of 100 PwMS suggesting that mSteps could be useful in calculating the EDSS outdoors,” the researchers concluded.

However, “there is still a need for solutions to accurately and reliably measure distance walked indoors.”

Wi-Fi positioning systems are still being developed, and a 5G network might improve indoor tracking precision in the future, according to the team.