ISO 24227:2023

INTERNATIONAL ISO
STANDARD 24227
First edition
2023-10
Validation protocol for walking speed
as extracted from various sensor
systems that measure human body
motion for the healthcare sector
Protocole de validation de la vitesse de marche extraite de divers
systèmes de capteurs mesurant les mouvements du corps humain
pour le secteur des soins de santé
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Validation protocol of walking speed as provided by various sensor systems .1
4.1 General . 1
4.2 Qualifications of the measurer . 1
4.3 Sample size and participant selection for the validation study . 2
4.4 Validation study procedure . 2
4.4.1 Establishing walking distance . 2
4.4.2 Measurement of walking speed . 2
4.4.3 Comparison of measured walking speeds . 3
5 Validation study reporting . 3
Annex A (informative) Template to report the results of a validation study .4
Annex B (informative) Sample report of the results of a validation study .5
Bibliography . 7
iii
Foreword
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iv
Introduction
Walking speed is recognized as being a reliable predictor of healthy function for people of all ages,
and in particular for the elderly, and has been referred to as one of the “vital signs” of physical health
[1]–[4]
and as one of the predictive factors of future health and death . Studies of community-dwelling
[4]
older adults (65 years and older: mean ± standard deviations age 74,2 ± 2,9 years for one study and
[5]
74,1 ± 5,7 years for another ) have shown that walking speeds faster than 1,0 m/s suggest healthier
ageing, while walking speeds slower than 0,6 m/s suggest an increased likelihood of poor health and
[4],[5]
function .
In the healthcare sector, measuring walking speed by using a stopwatch and a tape measure is the gold
[6]–[8]
standard (hereafter, reference method) . Recent new technologies enable walking speed to be
[9],[10]
measured using various sensor systems (e.g. wearable sensors, environment-embedded sensors) .
These technologies offer possible improvements on the reference method in healthcare for measuring
[10]
walking speed, such as being able to measure walking speed during daily living . Measurements taken
during daily living could produce a more accurate health index due to decreased examiner influence
and the ability to measure walking speed for longer distances and more frequently than in a clinical
setting. Further, sensor systems can be utilized to establish a fatigue index in the work environment.
There is, however, no fixed standard to validate walking speed measured by such new technologies
against the reference method. Therefore, users of such systems (e.g. physicians, therapists, ergonomists)
cannot compare the accuracy between different systems based on the same evaluation protocol.
The intent of this document is to provide manufacturers of sensor system technologies with a standard
means of validating and reporting walking speed values against the values provided by the reference
method for measuring walking speed in the healthcare sector.
There are several different fundamental technologies underlying commercially available sensor systems
that measure walking speed. This document covers these technologies, including accelerometer-based
systems, depth-sensor-based systems and global positioning system (GPS)-based systems.
v
INTERNATIONAL STANDARD ISO 24227:2023(E)
Validation protocol for walking speed as extracted from
various sensor systems that measure human body motion
for the healthcare sector
1 Scope
This document provides a procedure for the standard validation and reporting protocol of walking
speed measurements by technological sensor systems compared with the values provided by the
reference method, namely walking speed as measured by a tape measure and a stopwatch.
It does not address the detailed or specific uses of various technological sensor systems in healthcare.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
reference method
method to measure walking speed using a measuring tape and a stopwatch, often used in the healthcare
sector
3.2
parallax error
error that occurs when the observer’s eyes are positioned at an angle to the measurement markings
4 Validation protocol of walking speed as provided by various sensor systems
4.1 General
For a sensory system to be validated against the reference method for measuring walking speed, the
validation study procedure shall be followed. A validation study shall be done by comparing walking
speed as extracted by sensor systems and walking speed as measured by the reference method.
Each participant shall be measured by the sensor systems and reference method simultaneously.
The measurer shall use a stopwatch and a tape measure that is provided with an individually
serial-numbered traceable certificate from a calibration laboratory meeting the requirements of
[11]
ISO/IEC 17025 .
4.2 Qualifications of the measurer
The measurer should have learned and practised the measurement method under the supervision of a
person with clinical experience for the reference method and a representative from the manufacturer
or distributor of the sensor system.
It is preferable that the same measurer measures (or be present for measurements being taken) all
participant(s) for all test protocols. When there are multiple measurers, inter-measurer differences in
measurement accuracy can occur. Therefore, it is preferable to report inter-rater reliability, such as
intraclass correlation coefficients (case 2), by measuring the same subjects with multiple measurers.
4.3 Sample size and participant selection for the validation study
[12],[13]
Based on the sample size of the previous studies , the sample size of the validation study shall
be at least 50 data points, covering the entire walking speed range (i.e. mean ± 2 standard deviations)
of the target population intended by the sensor system design. These data are preferably collected
from multiple people walking several times each, because the walking speed extracted from the sensor
system can be affected by the parameters that vary from participa
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