Apple Watch Series 3 User Manual
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Using Apple Watch to Estimate
Six-Minute Walk Distance
May 2021
Overview 3 ..........................................................................................................................................
Introduction 3 ......................................................................................................................................................
In-Clinic Six-Minute Walk Test 3 .....................................................................................................................
Remotely Administered Six-Minute Walk Test 3 .............................................................................................
Estimated Six-Minute Walk Distance 4 .................................................................................................
Metric Description 4 ............................................................................................................................................
Development 5 ....................................................................................................................................................
Results 6 .............................................................................................................................................................
Discussion 8 ........................................................................................................................................................
Conclusions 9 ......................................................................................................................................
References 9.......................................................................................................................................
Using Apple Watch to Estimate Six-Minute Walk Distance
May 2021
2
Contents
Overview
With watchOS 7, Apple Watch Series 3 and later provide an estimate of the distance
users are able to walk in six minutes, a measurement that may be used in health
applications as an overall marker of an individual’s cardiovascular fitness and mobility.
This paper provides a detailed understanding of how the metric is estimated on "
Apple Watch, including testing and validation.
Introduction
In-Clinic Six-Minute Walk Test
The six-minute walk test (6MWT) is a simple method of assessing an individual’s functional capacity and
endurance. First introduced in the early 1980s as a more tolerable and similarly valid and reliable substitute
for more rigorous and expensive forms of exercise testing, the 6MWT is most often performed in a clinic
1
setting, where an individual is observed walking up and down a hallway of known length for six minutes.
The test result is the total distance walked during the six minutes, referred to as the six-minute walk
distance (6MWD). Over the approximately 40 years since its introduction, the test has been wellcharacterized in many age groups, ethnicities, and states of health and disease. It has been used as a
clinical trial endpoint for studying the efficacy of different interventions on disease, as well as a metric for
risk stratification across broad populations.
2
Despite the advantages and utility of the 6MWT, there are drawbacks to the administration and interpretation
of the test in routine practice. First, the office or clinic layout must provide an environment — typically a
hallway — of adequate length (generally 10 to 30 meters) where an individual can walk uninterrupted without
disrupting normal clinic workflows. Second, the time and associated costs required for the test can be
significant, as best practice normally calls for at least one practice test to familiarize the user with the
protocol, followed by an hour rest, then followed by a second test that generally yields a more accurate
result.
, , ,
3 4 5 6
Remotely Administered Six-Minute Walk Test
In a busy clinical setting, administration of a 6MWT may not be practical. Home-administered 6MWTs "
are strongly correlated with supervised, in-clinic exams and may be a suitable substitute. Measurements
7
of 6MWD using smartphones correlate with in-clinic measurements; however, in a study setting, only "
60 percent of at-home 6MWTs administered and measured with a smartphone were completed. Home
8
testing, while promising, may not be feasible at scale or over long time periods given low participant
compliance.
Apple Watch is changing how 6MWD is measured, and it’s helping overcome the above practical
challenges of both home testing and in-clinic exams. Using data passively collected from Apple Watch
Series 3 and later with watchOS 7, users will be able to visualize and share an estimate of their 6MWD. The
estimated six-minute walk distance (e6MWD) is based on multimodal sensor signals passively observed
over long time periods of a user’s normal behaviors, rather than a direct, single point-in-time measurement
of a six-minute walking bout. In most cases, an e6MWD will be updated weekly and available for users to
view in the Health app on an iPhone paired to their Apple Watch.
Using Apple Watch to Estimate Six-Minute Walk Distance
May 2021
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