Wheelchair seating

This document specifies apparatus, test methods, and disclosure requirements for determination of lateral stability properties of wheelchair seat cushions by measuring the response from the cushion to a shift in the centre of mass of the load on the cushion. It provides a method of determining changes in a particular physical and mechanical property of the cushion. It does not provide information specific to cushion performance for a particular individual user. It does not provide information related to anterior-posterior stability, nor to stability contributions from cushion edges. NOTEÂ 1Â Â Â Test conditions simulate a symmetric anatomy. NOTEÂ 2Â Â Â Loads are intended to represent those seen under the pelvis of a 40th to 60th percentile wheelchair user. This document is applicable to cushions used in situations other than a wheelchair.

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Status
Published
Publication Date
14-Jun-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
11-May-2021
Completion Date
11-May-2021
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INTERNATIONAL ISO
STANDARD 16840-13
First edition
2021-06
Wheelchair seating —
Part 13:
Determination of the lateral stability
property of a seat cushion
Reference number
ISO 16840-13:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 16840-13:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 16840-13:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviations........................................................................................................................................................................................................... 2

5 Apparatus ..................................................................................................................................................................................................................... 2

5.1 RCLI ................................................................................................................................................................................................................... 2

5.2 RCLI cover ................................................................................................................................................................................................... 2

5.3 Stability test rig ...................................................................................................................................................................................... 2

5.4 Tilt angle measurement device ................................................................................................................................................. 3

6 Test environment ................................................................................................................................................................................................. 3

7 Preparation and setup of cushion ...................................................................................................................................................... 4

7.1 Choice of cushion .................................................................................................................................................................................. 4

7.2 Preconditioning the cushion ....................................................................................................................................................... 4

8 Cushion lateral stability test method .............................................................................................................................................. 4

8.1 General ........................................................................................................................................................................................................... 4

8.2 Test procedure ......................................................................................................................................................................................... 4

8.3 Method of calculation ........................................................................................................................................................................ 5

8.4 Test report ................................................................................................................................................................................................... 6

Annex A (informative) Method for using pressure mapping to characterize behaviour of

reaction forces during the stability property test ............................................................................................................. 7

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 16840-13:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 173, Assistive products, Subcommittee

SC 1, Wheelchairs.
A list of all parts in the ISO 16840 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 16840-13:2021(E)
Introduction

The seat cushion, as the base of support for the wheelchair occupant, affects postural stability by

resisting moments when the occupant’s centre of mass is displaced. Research exploring the influence of

cushion design and setup on pelvic orientation and measures of postural stability is limited. Standard

test methods, highlighted in ISO 16840-2, should be used to characterize tissue integrity management

properties of wheelchair seat cushions such as immersion, envelopment, hysteresis, impact damping,

recovery, and horizontal stiffness.

This document provides details of test equipment and a method for the measurement of the cushion’s

ability to resist movements contributing to pelvic obliquity. Changes in pelvic obliquity, as a result of a

shift in the centre of mass, can affect stability and mobility depending on the response of the cushion,

the occupant’s core muscle strength, etc. Moments in the test method are created by shifting a vertical

load laterally on the top surface of a standard rigid cushion loading indenter (RCLI) simulating the

buttocks and upper thighs. The test method described in this document is intended to differentiate

lateral stability performance between cushions and is not appropriate for ranking cushions nor for

directly matching this characteristic with an individual occupant’s requirements. The link to clinical

efficacy, although implied, has not been validated. It is intended that this document will evolve when

the evidence of clinical relevance is confirmed. Test conditions (e.g. the RCLI) simulate a symmetric

anatomy. The loads used in this document are based on the 40th to 60th percentile wheelchair occupant

and are not intended to characterize any cushion properties under bariatric loading conditions or to

assess the weight capacity of a cushion.

There are other stability issues of relevance to the occupant, but which are not addressed in this

document. For example, because the positions of the occupant’s thighs, lower legs, and feet can

counterbalance any instability elements of the cushion, an anterior-posterior stability test carries

lesser significance to the occupant and is not included. This document also does not address aspects

of wheelchair sitting stability related to the resistance or assistance that the cushion provides to the

occupant regaining a neutral pelvis following a lateral tilt as viewed in the frontal plane. Additionally,

edge stability is not assessed. In some cases, the occupant will benefit from the stability provided by

the cushion’s edge (i.e. a strengthened edge could be of benefit in supporting the required functional

posture while the occupant is seated on the cushion). In other cases, the occupant could prefer lesser

stability at the edge to assist in transferring off the cushion.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16840-13:2021(E)
Wheelchair seating —
Part 13:
Determination of the lateral stability property of a seat
cushion
1 Scope

This document specifies apparatus, test methods, and disclosure requirements for determination of

lateral stability properties of wheelchair seat cushions by measuring the response from the cushion to

a shift in the centre of mass of the load on the cushion. It provides a method of determining changes in

a particular physical and mechanical property of the cushion. It does not provide information specific

to cushion performance for a particular individual user. It does not provide information related to

anterior-posterior stability, nor to stability contributions from cushion edges.
NOTE 1 Test conditions simulate a symmetric anatomy.

NOTE 2 Loads are intended to represent those seen under the pelvis of a 40th to 60th percentile wheelchair

user.

This document is applicable to cushions used in situations other than a wheelchair.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 7176-26, Wheelchairs — Part 26: Vocabulary

ISO 16840-2:2018, Wheelchair seating — Part 2: Determination of physical and mechanical characteristics

of seat cushions intended to manage tissue integrity
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 16840-2 and ISO 7176-26 and

the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
cushion lateral stability

cushion’s ability to resist tilting of the pelvis as viewed in the frontal plane caused by a shifting centre

of mass of occupant in a lateral direction
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 16840-13:2021(E)
3.2
cushion stability test live load

portion of the total apparatus weight applied to the test cushion that translates in the horizontal plane

to shift the centre of mass of the load relative to the test cushion during the test procedure

Note 1 to entry: Example of a live load are keys 4, 5 and 6 of Figure 1.
3.3
cushion stability test dead load

portion of the total apparatus weight applied to the test cushion that does not translate in the horizontal

plane relative to the test cushion during the test procedure
Note 1 to entry: Example of a dead load are keys 7 and 8 of Figure 1.
4 Abbreviations
RCLI Rigid Cushion Loading Indenter
5 Apparatus
5.1 RCLI
An RCLI as specified in ISO 16840-2:2018, Annex A and D.
5.2
...

INTERNATIONAL ISO
STANDARD 16840-13
First edition
Wheelchair seating —
Part 13:
Determination of the lateral stability
property of a seat cushion
PROOF/ÉPREUVE
Reference number
ISO 16840-13:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 16840-13:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 16840-13:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviations........................................................................................................................................................................................................... 2

5 Apparatus ..................................................................................................................................................................................................................... 2

5.1 RCLI ................................................................................................................................................................................................................... 2

5.2 RCLI cover ................................................................................................................................................................................................... 2

5.3 Stability test rig ...................................................................................................................................................................................... 2

5.4 Tilt angle measurement device ................................................................................................................................................. 3

6 Test environment ................................................................................................................................................................................................. 3

7 Preparation and setup of cushion ...................................................................................................................................................... 4

7.1 Choice of cushion .................................................................................................................................................................................. 4

7.2 Preconditioning the cushion ....................................................................................................................................................... 4

8 Cushion lateral stability test method .............................................................................................................................................. 4

8.1 General ........................................................................................................................................................................................................... 4

8.2 Test procedure ......................................................................................................................................................................................... 4

8.3 Method of calculation ........................................................................................................................................................................ 5

8.4 Test report ................................................................................................................................................................................................... 6

Annex A (informative) Method for using pressure mapping to characterize behaviour of

reaction forces during the stability property test ............................................................................................................. 7

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 16840-13:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 173, Assistive products, Subcommittee SC

1, Wheelchairs.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 16840-13:2021(E)
Introduction

The seat cushion, as the base of support for the wheelchair occupant, affects postural stability by

resisting moments when the occupant’s centre of mass is displaced. Research exploring the influence of

cushion design and setup on pelvic orientation and measures of postural stability is limited. Standard

test methods, highlighted in ISO 16840-2, should be used to characterize tissue integrity management

properties of wheelchair seat cushions such as immersion, envelopment, hysteresis, impact damping,

recovery, and horizontal stiffness.

This document provides details of test equipment and a method for the measurement of the cushion’s

ability to resist movements contributing to pelvic obliquity. Changes in pelvic obliquity, as a result of a

shift in the centre of mass, can affect stability and mobility depending on the response of the cushion,

the occupant’s core muscle strength, etc. Moments in the test method are created by shifting a vertical

load laterally on the top surface of a standard rigid cushion loading indenter (RCLI) simulating the

buttocks and upper thighs. The test method described in this document is intended to differentiate

lateral stability performance between cushions and is not appropriate for ranking cushions nor for

directly matching this characteristic with an individual occupant’s requirements. The link to clinical

efficacy, although implied, has not been validated. It is intended that this document will evolve when

the evidence of clinical relevance is confirmed. Test conditions (e.g. the RCLI) simulate a symmetric

anatomy. The loads used in this document are based on the 40th to 60th percentile wheelchair occupant

and are not intended to characterize any cushion properties under bariatric loading conditions or to

assess the weight capacity of a cushion.

There are other stability issues of relevance to the occupant, but which are not addressed in this

document. For example, because the positions of the occupant’s thighs, lower legs, and feet can

counterbalance any instability elements of the cushion, an anterior-posterior stability test carries

lesser significance to the occupant and is not included. This document also does not address aspects

of wheelchair sitting stability related to the resistance or assistance that the cushion provides to the

occupant regaining a neutral pelvis following a lateral tilt as viewed in the frontal plane. Additionally,

edge stability is not assessed. In some cases, the occupant will benefit from the stability provided by

the cushion’s edge (i.e. a strengthened edge could be of benefit in supporting the required functional

posture while the occupant is seated on the cushion). In other cases, the occupant could prefer lesser

stability at the edge to assist in transferring off the cushion.
© ISO 2021 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16840-13:2021(E)
Wheelchair seating —
Part 13:
Determination of the lateral stability property of a seat
cushion
1 Scope

This document specifies apparatus, test methods, and disclosure requirements for determination of

lateral stability properties of wheelchair seat cushions by measuring the response from the cushion to

a shift in the centre of mass of the load on the cushion. It provides a method of determining changes in

a particular physical and mechanical property of the cushion. It does not provide information specific

to cushion performance for a particular individual user. It does not provide information related to

anterior-posterior stability, nor to stability contributions from cushion edges.
NOTE 1 Test conditions simulate a symmetric anatomy.

NOTE 2 Loads are intended to represent those seen under the pelvis of a 40th to 60th percentile wheelchair user.

This document is applicable to cushions used in situations other than a wheelchair.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 16840-2:2018, Wheelchair seating — Part 2: Determination of physical and mechanical characteristics

of seat cushions intended to manage tissue integrity
ISO 7176-26, Wheelchairs — Part 26: Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 16840-2 and ISO 7176-26 and

the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
cushion lateral stability

cushion’s ability to resist tilting of the pelvis as viewed in the frontal plane caused by a shifting centre

of mass of occupant in a lateral direction
3.2
cushion stability test live load

portion of the total apparatus weight applied to the test cushion that translates in the horizontal plane

to shift the centre of mass of the load relative to the test cushion during the test procedure

Note 1 to entry: Example of a live load are keys 4, 5 and 6 of Figure 1.
© ISO 2021 – All rights reserved PROOF/ÉPREUVE 1
---------------------- Page: 6 ----------------------
ISO 16840-13:2021(E)
3.3
cushion stability test dead load

portion of the total apparatus weight applied to the test cushion that does not translate in the horizontal

plane relative to the test cushion during the test procedure
Note 1 to entry: Example of a dead load are keys 7 and 8 of Figure 1.
4 Abbreviations
RCLI Rigid Cushion Loading Indenter
5 Apparatus
5.1 RCLI
An RCLI as specified in ISO 16840-2:2018, Annex A and D.
5.2 RCLI cover
There shall be a denim material cover between the
...

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