ISO 11228-3:2007

INTERNATIONAL ISO
STANDARD 11228-3
First edition
2007-04-01
Corrected version
2009-11-01

Ergonomics — Manual handling —
Part 3:
Handling of low loads at high frequency
Ergonomie — Manutention manuelle —
Partie 3: Manipulation de charges faibles à fréquence de répétition
élevée





Reference number
ISO 11228-3:2007(E)
©
ISO 2007

---------------------- Page: 1 ----------------------
ISO 11228-3:2007(E)
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shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
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accepts no liability in this area.
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©  ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2007 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 11228-3:2007(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope .1
2 Normative references.1
3 Terms, definitions, symbols and abbreviated terms .2
3.1 Terms and definitions .2
3.2 Symbols and abbreviated terms .3
4 Recommendations .4
4.1 Avoiding repetitive handling tasks.4
4.2 Risk assessment.4
4.2.1 General .4
4.2.2 Hazard identification .6
4.2.2.1 General.6
4.2.2.2 Repetition.6
4.2.2.3 Posture and movement .6
4.2.2.4 Force .6
4.2.2.5 Duration and insufficient recovery.6
4.2.2.6 Object characteristics .6
4.2.2.7 Vibration and impact forces.6
4.2.2.8 Environmental conditions (lighting, climate, noise, etc.) .7
4.2.2.9 Work organization.7
4.2.2.10 Psychosocial factors (e.g. job complexity, job demands, job content) .7
4.2.2.11 Individuals .7
4.2.3 Risk estimation .8
4.2.3.1 Method 1 — Simple risk assessment.8
4.2.3.2 Method 2 — Detailed risk assessment .8
4.3 Risk reduction.12
Annex A (informative) Risk assessment — General framework and information on available
methods.13
Annex B (informative) Method 1 — Simple risk assessment checklist.16
Annex C (informative) Method 2 — OCRA method for detailed risk assessment .25
Annex D (informative) Other methods for detailed risk assessment.66
Annex E (informative) Risk reduction .70
Bibliography.73

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ISO 11228-3:2007(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 11228-3 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 3,
Anthropometry and biomechanics.
ISO 11228 consists of the following parts, under the general title Ergonomics — Manual handling:
⎯ Part 1: Lifting and carrying
⎯ Part 2: Pushing and pulling
⎯ Part 3: Handling of low loads at high frequency
This corrected version of ISO 11228-3:2007 incorporates the following corrections:
⎯ the error message substituted for Equation (C.9) has been replaced by the missing equation;
⎯ the hyperlink previously referenced as [65] in the Bibliography, no longer active, has been deleted,
together with its mention in the main body of the document, and the numbers of the other bibliographical
references following it have been adjusted accordingly.

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ISO 11228-3:2007(E)
Introduction
Handling of low loads at high frequency (repetitive work) can cause pain and fatigue, which could lead to
musculoskeletal disorders, reduced productivity, and deteriorated posture and movement co-ordination. The
latter can increase the risk of errors and may result in reduced quality and hazardous situations. Good
ergonomic design and proper organization of work are basic requirements for the avoidance of the adverse
effects mentioned.
Risk factors in repetitive work include the frequency of actions, exposure duration, postures and movement of
body segments, forces associated with the work, work organization, job control, demands on work output (e.g.
quality, task precision) and level of training/skill. Additional factors can include environmental factors, such as
climate, noise, vibration and illumination.
The recommendations provided by this part of ISO 11228 are based on available scientific evidence
concerning the physiology and epidemiology of manual work. The knowledge is, however, limited, and the
suggested guidelines are subject to change according to future research.

© ISO 2007 – All rights reserved v

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INTERNATIONAL STANDARD ISO 11228-3:2007(E)

Ergonomics — Manual handling —
Part 3:
Handling of low loads at high frequency
1 Scope
This part of ISO 11228 establishes ergonomic recommendations for repetitive work tasks involving the manual
handling of low loads at high frequency. It provides guidance on the identification and assessment of risk
factors commonly associated with handling low loads at high frequency, thereby allowing evaluation of the
related health risks to the working population. The recommendations apply to the adult working population and
are intended to give reasonable protection for nearly all healthy adults. Those recommendations concerning
health risks and control measures are mainly based on experimental studies regarding musculoskeletal
loading, discomfort/pain and endurance/fatigue related to methods of working. For the evaluation of working
postures, refer to ISO 11226.
This part of ISO 11228 is intended to provide information for all those involved in the design or redesign of
work, jobs and products.
2 Normative references
The following referenced documents are indispensable for the application 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 6385, Ergonomic principles in the design of work systems
ISO 11226, Ergonomics — Evaluation of static working postures
ISO 11228-1, Ergonomics — Manual handling — Part 1: Lifting and carrying
ISO 11228-2, Ergonomics — Manual handling — Part 2: Pushing and pulling
ISO 14738, Safety of machinery — Anthropometric requirements for the design of workstations at machinery
ISO 15534 (all parts), Ergonomic design for the safety of machinery

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ISO 11228-3:2007(E)
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 6385, ISO 11228-1, ISO 11228-2,
ISO 11226 and the following terms, definitions, symbols and abbreviated terms apply.
NOTE In the definitions involving frequency, a unit of time is mentioned because more than one method is involved,
each using a different unit, e.g. seconds in HAL (see Annex D), minutes in the OCRA Index (see Annex C) and Strain
Index (see Annex D).
3.1 Terms and definitions
3.1.1
repetitive task
task characterized by repeated work cycles
3.1.2
work cycle
sequence of (technical) actions that are repeated always the same way
3.1.3
cycle time
t
C
time, in seconds, elapsing from the moment when one operator begins a work cycle to the moment that the
same work cycle is repeated
3.1.4
technical action
elementary manual actions required to complete the operations within the cycle
EXAMPLE Holding, turning, pushing or cutting.
3.1.5
repetitiveness
characteristic of a task when a person is continuously repeating the same work cycle, technical actions and
movements
3.1.6
frequency of actions
number of technical actions per unit of time
3.1.7
force
F
physical effort of the operator required to execute the task
3.1.8
postures and movements
positions and movements of body segment(s) or joint(s) required to execute the task
3.1.9
recovery time
period of rest following a period of activity which allows restoration of musculoskeletal function (in minutes)
3.1.10
additional risk factor
object and environmental factors for which there is evidence of causal or aggravating relationship with
work-related musculoskeletal disorders of the upper limb
EXAMPLE Vibration, local pressure, cold environment or cold surfaces.
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ISO 11228-3:2007(E)
3.1.11
move
transport of an object to a given destination using the upper limbs and without walking
3.1.12
reach
shift the hand towards a prefixed destination
3.1.13
carry
transport of an object to a given destination by walking
3.2 Symbols and abbreviated terms
A additional multiplier
M
ATA actual technical action
f frequency of actions per minute
F force (N)
F basic force limit
B
F force limit
L
F force multiplier
M
j generic repetitive tasks
k constant of frequency of technical actions per minute
f
L actual load
MODA PTS modular analysis predetermined time system
MSD musculoskeletal disorders
MTA motion time analysis
MTM methods/time measurement
MVC maximum voluntary contraction
n overall number of actual technical actions within a shift
ATA
n number of exposed individuals
ep
n number of persons affected by one or more UL-WMSD
pa
n partial reference number of technical actions within a shift
RPA
n number of repetitive task(s) performed during a shift
rt
n overall number of reference technical actions within a shift
RTA
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ISO 11228-3:2007(E)
n number of technical actions in a cycle
TC
OCRA occupational repetitive action
PA prevalence (%) of persons affected
P posture multiplier
M
PTS predetermined time system
RTA reference technical action
R repetitiveness multiplier
eM
R recovery multiplier
cM
SE standard error
t net duration of each repetitive task, in minutes
cycle time, in seconds
t
C
TA technical action
t duration multiplier
M
UL-WMSD upper limb work-related musculoskeletal disorders
WF work factor
4 Recommendations
4.1 Avoiding repetitive handling tasks
Hazardous manual handling tasks should be avoided wherever possible. This can be achieved through work
enlargements, job rotation and/or mechanization/automation within the framework of a participative
ergonomics approach. In the case of repetitive handling of low loads at high frequency, many tasks can be
modified through the use of robotics or automated production systems.
NOTE A “participative ergonomics approach” signifies the practical involvement of workers, supported by suitable
communication, in planning and managing a significant amount of their work activities, with sufficient knowledge and ability
to influence both processes and outcomes in order to achieve desirable goals.
4.2 Risk assessment
4.2.1 General
When repetitive handling is unavoidable, a four-step approach in accordance with ISO Guide 51 and
ISO 14121, and involving both risk assessment and risk reduction, should be adopted. The four steps are
hazard identification, risk estimation, risk evaluation and risk reduction.
The procedure shown in Figure 1 should be adopted when carrying out a risk assessment of jobs involving the
manual handling of low loads at high frequency.
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ISO 11228-3:2007(E)

Figure 1 — Risk assessment procedure


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ISO 11228-3:2007(E)
4.2.2 Hazard identification
4.2.2.1 General
The first step of the risk assessment is to identify whether hazards exist which may expose individuals to a
risk of injury. If such hazards are present, then a more detailed risk assessment can be necessary. When
determining if one or more of the following hazards is present, consideration should be given to the guidelines
for avoiding them.
4.2.2.2 Repetition
Frequent repetitive movements give rise to a risk of injury that can vary depending on the context of the
movement pattern and the individual. As the movement cycle increases and/or the cycle time decreases, the
risk of injury increases. Repetitive movements should be avoided within a task or job.
4.2.2.3 Posture and movement
Sitting restricts overall movement of the body, particularly those of the lower leg and back. This may lead to
increased and complex loading of the back and upper extremities. Standing for prolonged periods of time
often results in pain/discomfort in the legs and lower back and can lead to venous pooling in the legs.
Complex postures involving combined movements (e.g. flexed and twisted) can present greater risk (see
ISO 11226). Whenever possible, workers should be given the option to vary between sitting and standing.
Work tasks and operations should provide variations to the working posture: both whole-body postures and
movement of specific limbs. In the work tasks, extreme ranges of joint movement should be avoided; there is
also need to avoid prolonged static postures.
4.2.2.4 Force
Forceful exertions can be harmful. Tasks should involve smooth force exertions, with the avoidance of sudden
or jerky movements. Handling precision (accurate picking and placement), and the type and nature of the grip
can introduce additional muscular activation.
4.2.2.5 Duration and insufficient recovery
Insufficient time for the body to recover between repetitive movements (i.e. lack of recovery time) increases
the risk of injury. Duration can be broken down into different levels, i.e. work shift duration, job duration, task
duration. The opportunity for recovery or rest may fall within each of these work periods.
4.2.2.6 Object characteristics
Inappropriately designed objects could have characteristics that can cause harm (e.g. contact forces, shape,
dimensions, coupling, object temperature). Inappropriately placed handholds may lead to awkward hand/arm
postures. Non-cushioned handholds and objects constructed of a smooth material increase the difficulty of
grasping the object and increase force requirements. The size and shape of the object being handled and the
coupling between it and the operator’s hands will determine the grip type and the force that the operator must
exert.
4.2.2.7 Vibration and impact forces
Exposure to hand/arm vibration, shocks or impacts can lead to a desensitizing of the hand and increase the
force necessary for gripping an object or tool. Prolonged exposure to these types of risk factors has also been
linked to vascular and neurological disorders of the upper limbs.
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ISO 11228-3:2007(E)
4.2.2.8 Environmental conditions (lighting, climate, noise, etc.)
Inappropriate lighting, hot and cold environments and high levels of noise can impose additional hazards. Wet
or contaminated surfaces are likely to inhibit the ability to exert forces and increase the risk of injury. The
designer of products shall consider environmental conditions only within the limits of the foreseeable use of
the product.
4.2.2.9 Work organization
Work organization (e.g. task duration, job duration, recovery time, shift patterns) has an important part to play
in the exposure to musculoskeletal risk factors. This should be structured to facilitate rest periods and avoid
the use of similar muscle groups over the duration of the work shift. Job rotation, job diversification and job
enlargement are all methods of structuring the work to facilitate variation and recovery within the work period.
4.2.2.10 Psychosocial factors (e.g. job complexity, job demands, job content)
Psychological response to work and workplace conditions has an important influence on general health and,
in particular, musculoskeletal health. These factors include the design, organization and management of work,
the specific impact of workplace risk factors, such as work content, and the overall social environment (i.e. the
context of work). Many of the effects of these psychosocial factors occur via stress-related processes, which
can have a direct effect on biochemical and physiological responses.
4.2.2.11 Individuals
Individual skills, training, age, gender, health problems and pregnancy are personal characteristics that can
influence performance and should be considered in the risk assessment. Skill and experience are likely to
benefit the individual when performing the task and reduce the risk of injury. Training can increase the level of
skill.
Important aspects of work design include the amount of control an individual has over his/her work, the level
of work demands, the variety of tasks he/she is required to perform and the level of support provided by
managers, supervisors and/or co-workers. Undesirable psychosocial aspects of a job contributing to a risk of
musculoskeletal disorders include the following:
⎯ workers have little or no control over their work and work methods or organization;
⎯ tasks require high levels of attention and concentration;
⎯ workers are unable to make full use of their skills;
⎯ workers have little or no involvement in decision making;
⎯ workers are expected to carry out repetitive, monotonous tasks exclusively;
⎯ work is machine- or system-paced;
⎯ work demands are perceived as excessive;
⎯ payment systems encourage working too quickly or without breaks;
⎯ work systems limit opportunities for social interaction;
⎯ high levels of effort are not balanced by sufficient reward (resources, remuneration, self-esteem, status,
etc.).
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ISO 11228-3:2007(E)
4.2.3 Risk estimation
4.2.3.1 Method 1 — Simple risk assessment
Risk estimation is performed by a simple risk assessment of jobs composed by a single repetitive task
(monotask jobs).
The procedure and checklist model presented in Annex B is preferred for the carrying out of the simple risk
assessment. There are four parts to this assessment procedure:
⎯ preliminary information describing the job task;
⎯ hazard identification and risk estimation procedure and checklist;
⎯ overall evaluation of the risk;
⎯ remedial action to be taken.
NOTE As a second choice, other simple methods and checklists given in Annex A can be used, taking into
consideration the specific characteristics of the repetitive task under examination.
Risk estimation using Method 1 should allow the classification of the risk by the three-zone approach (green,
yellow and red) and determine the consequent action to be taken. The three risk zones are defined as follows.
a) Green zone (acceptable risk)
The risk of disease or injury is negligible or is at an acceptably low level for the entire working population.
No action is required.
b) Yellow zone (conditionally acceptable risk)
There is a risk of disease or injury that cannot be neglected for the entire working population or part of it.
The risk shall be further estimated (using the more detailed assessment of Method 2), analysed together
with contributory risk factors and followed as soon as possible by redesign. Where redesign is not
possible, other measures to control the risk shall be taken.
c) Red zone (not acceptable)
There is a considerable risk of disease or injury that cannot be neglected for the operator population.
Immediate action to reduce the risk (e.g. redesign, work organization, worker instruction and training) is
necessary (see 4.3 and Annex E).
4.2.3.2 Method 2 — Detailed risk assessment
4.2.3.2.1 General criteria
If the risk estimated using Method 1 is considered to be YELLOW or RED, or if the job is composed of two or
more repetitive tasks (multitask job), the performing of a more detailed risk assessment is recommended. This
will also allow a better determination of the remedial measures to be taken.
For detailed risk assessment, OCRA (occupational repetitive action) is the preferred method (see 4.2.3.2.2). It
is recommended for the specific purposes of this part of ISO 11228 because, given the knowledge at the time
of publication, it considers all the relevant risk factors, is also applicable to “multitask jobs”, and provides
criteria — based on extensive epidemiological data — for forecasting the occurrence of UL-WMSD (upper
limb work-related musculoskeletal disorders) in exposed working populations.
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ISO 11228-3:2007(E)
Other detailed risk assessment methods are available which can be used for a detailed risk assessment,
depending on the kind of risk factors identified by Method 1, the nature of the job and the experience of the
analyst.
Annex D gives basic information about other detailed risk assessment methods useful for the purposes of this
part of ISO 11228, together with some remarks about their applicative limits at the time of publication.
Whichever method is used for detailed risk assessment, it should allow the classification of the risk by the
three-zone model and determine the consequences to be acted upon in accordance with Table 1.
Table 1 — Method 2 — Final assessment criteria
Zone Risk level Consequences
Green No risk Acceptable: no consequences
Improve structural risk factors (posture, force, technical actions, etc.)
Yellow Very low risk
or take other organizational measures
Red Risk Redesign tasks and workplaces according to priorities

4.2.3.2.2 OCRA method for detailed risk assessment
The OCRA index is the ratio between the number of actual technical actions, ATA, carried out during a work
shift and the number of reference technical actions, RTA, for each upper limb, specifically determined in the
[11], [38]
scenario under examination .
The OCRA risk assessment procedure consists of three basic steps:
a) Step 1
Calculate the frequency of technical actions/min and the overall number of ATA carried out in the shift (by
each upper limb).
b) Step 2
Calculate the overall number of RTA.
c) Step 3
Calculate the OCRA index and perform a risk evaluation.
Table 2 (ATA and RTA calculation in monotask jobs), Table 3 (ATA and RTA calculation in multitask jobs) and
Table 4 (OCRA index calculation and risk evaluation) give an overview of the procedure detailed in Annex C.
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ISO 11228-3:2007(E)
Table 2 — OCRA assessment procedure for monotask jobs — Steps 1 and 2
Calculate the overall number of actual technical actions, n , carried out in a shift by each upper limb.
Step1
ATA
a) Count the number of technical actions, n , in a cycle.
TC
Evaluate their frequency, f, per minute, considering the cycle time, t , in seconds:
b)
C

60
fn=×
TC
t
C
c) Evaluate the net duration, t, of the repetitive task in the shift, in minutes.
d) Calculate the overall number of ATA carried out in the shift:

n = f × t
ATA
Step 2 Calculate the overall number of RTA within the shift:
n = k × F × P × R × A × t × R × t
RTA f M M eM M cM M
Constant of frequency, k , of technical actions = 30/min

30
f

×
F Force multiplier
M
×
P Posture multiplier
M
×
R
Repetitiveness multiplier
eM

×
A Additional multiplier
M
×
t
Duration of the repetitive task, in minutes
=
n Partial reference number of technical actions in the shift
RPA
×
t Duration multiplier
M

×
R Recovery multiplier
cM
=
n
Overall number of RTA
RTA
NOTE See 3.2. for the complete list of symbols and abbreviated terms used in this part of ISO 11228.

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ISO 11228-3:2007(E)
Table 3 — OCRA assessment procedure for multitask jobs — Steps 1 and 2
Calculate the overall number of actual technical actions, n , carried out in a shift by each upper limb,
ATA
Step1
considering each repetitive task, j, in the shift.
a) Count the numb
...

INTERNATIONAL ISO
STANDARD 11228-3
First edition
2007-04-01

Ergonomics — Manual handling —
Part 3:
Handling of low loads at high frequency
Ergonomie — Manutention manuelle —
Partie 3: Manipulation de charges faibles à fréquence de répétition
élevée





Reference number
ISO 11228-3:2007(E)
©
ISO 2007

---------------------- Page: 1 ----------------------
ISO 11228-3:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2007 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 11228-3:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms. 2
3.1 Terms and definitions. 2
3.2 Symbols and abbreviated terms . 3
4 Recommendations. 4
4.1 Avoiding repetitive handling tasks . 4
4.2 Risk assessment. 4
4.2.1 General. 4
4.2.2 Hazard identification. 6
4.2.2.1 General . 6
4.2.2.2 Repetition. 6
4.2.2.3 Posture and movement . 6
4.2.2.4 Force. 6
4.2.2.5 Duration and insufficient recovery.6
4.2.2.6 Object characteristics. 6
4.2.2.7 Vibration and impact forces. 6
4.2.2.8 Environmental conditions (lighting, climate, noise, etc.) . 7
4.2.2.9 Work organization. 7
4.2.2.10 Psychosocial factors (e.g. job complexity, job demands, job content) . 7
4.2.2.11 Individuals. 7
4.2.3 Risk estimation . 8
4.2.3.1 Method 1 — Simple risk assessment. 8
4.2.3.2 Method 2 — Detailed risk assessment. 8
4.3 Risk reduction . 12
Annex A (informative) Risk assessment — General framework and information on available
methods . 13
Annex B (informative) Method 1 — Simple risk assessment checklist . 16
Annex C (informative) Method 2 — OCRA method for detailed risk assessment . 25
Annex D (informative) Other methods for detailed risk assessment. 66
Annex E (informative) Risk reduction . 70
Bibliography . 73

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ISO 11228-3:2007(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 11228-3 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 3,
Anthropometry and biomechanics.
ISO 11228 consists of the following parts, under the general title Ergonomics — Manual handling:
⎯ Part 1: Lifting and carrying
⎯ Part 2: Pushing and pulling
⎯ Part 3: Handling of low loads at high frequency
iv © ISO 2007 – All rights reserved

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ISO 11228-3:2007(E)
Introduction
Handling of low loads at high frequency (repetitive work) can cause pain and fatigue, which could lead to
musculoskeletal disorders, reduced productivity, and deteriorated posture and movement co-ordination. The
latter can increase the risk of errors and may result in reduced quality and hazardous situations. Good
ergonomic design and proper organization of work are basic requirements for the avoidance of the adverse
effects mentioned.
Risk factors in repetitive work include the frequency of actions, exposure duration, postures and movement of
body segments, forces associated with the work, work organization, job control, demands on work output (e.g.
quality, task precision) and level of training/skill. Additional factors can include environmental factors, such as
climate, noise, vibration and illumination.
The recommendations provided by this part of ISO 11228 are based on available scientific evidence
concerning the physiology and epidemiology of manual work. The knowledge is, however, limited, and the
suggested guidelines are subject to change according to future research.

© ISO 2007 – All rights reserved v

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INTERNATIONAL STANDARD ISO 11228-3:2007(E)

Ergonomics — Manual handling —
Part 3:
Handling of low loads at high frequency
1 Scope
This part of ISO 11228 establishes ergonomic recommendations for repetitive work tasks involving the manual
handling of low loads at high frequency. It provides guidance on the identification and assessment of risk
factors commonly associated with handling low loads at high frequency, thereby allowing evaluation of the
related health risks to the working population. The recommendations apply to the adult working population and
are intended to give reasonable protection for nearly all healthy adults. Those recommendations concerning
health risks and control measures are mainly based on experimental studies regarding musculoskeletal
loading, discomfort/pain and endurance/fatigue related to methods of working. For the evaluation of working
postures, refer to ISO 11226.
This part of ISO 11228 is intended to provide information for all those involved in the design or redesign of
work, jobs and products.
2 Normative references
The following referenced documents are indispensable for the application 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 6385, Ergonomic principles in the design of work systems
ISO 11226, Ergonomics — Evaluation of static working postures
ISO 11228-1, Ergonomics — Manual handling — Part 1: Lifting and carrying
ISO 11228-2, Ergonomics — Manual handling — Part 2: Pushing and pulling
ISO 14738, Safety of machinery — Anthropometric requirements for the design of workstations at machinery
ISO 15534 (all parts), Ergonomic design for the safety of machinery

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ISO 11228-3:2007(E)
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 6385, ISO 11228-1, ISO 11228-2,
ISO 11226 and the following terms, definitions, symbols and abbreviated terms apply.
NOTE In the definitions involving frequency, a unit of time is mentioned because more than one method is involved,
each using a different unit, e.g. seconds in HAL (see Annex D), minutes in the OCRA Index (see Annex C) and Strain
Index (see Annex D).
3.1 Terms and definitions
3.1.1
repetitive task
task characterized by repeated work cycles
3.1.2
work cycle
sequence of (technical) actions that are repeated always the same way
3.1.3
cycle time
t
C
time, in seconds, elapsing from the moment when one operator begins a work cycle to the moment that the
same work cycle is repeated
3.1.4
technical action
elementary manual actions required to complete the operations within the cycle
EXAMPLE Holding, turning, pushing or cutting.
3.1.5
repetitiveness
characteristic of a task when a person is continuously repeating the same work cycle, technical actions and
movements
3.1.6
frequency of actions
number of technical actions per unit of time
3.1.7
force
F
physical effort of the operator required to execute the task
3.1.8
postures and movements
positions and movements of body segment(s) or joint(s) required to execute the task
3.1.9
recovery time
period of rest following a period of activity which allows restoration of musculoskeletal function (in minutes)
3.1.10
additional risk factor
object and environmental factors for which there is evidence of causal or aggravating relationship with
work-related musculoskeletal disorders of the upper limb
EXAMPLE Vibration, local pressure, cold environment or cold surfaces.
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ISO 11228-3:2007(E)
3.1.11
move
transport of an object to a given destination using the upper limbs and without walking
3.1.12
reach
shift the hand towards a prefixed destination
3.1.13
carry
transport of an object to a given destination by walking
3.2 Symbols and abbreviated terms
A additional multiplier
M
ATA actual technical action
f frequency of actions per minute
F force (N)
F basic force limit
B
F force limit
L
F force multiplier
M
j generic repetitive tasks
k constant of frequency of technical actions per minute
f
L actual load
MODA PTS modular analysis predetermined time system
MSD musculoskeletal disorders
MTA motion time analysis
MTM methods/time measurement
MVC maximum voluntary contraction
n overall number of actual technical actions within a shift
ATA
n number of exposed individuals
ep
n number of persons affected by one or more UL-WMSD
pa
n partial reference number of technical actions within a shift
RPA
n number of repetitive task(s) performed during a shift
rt
n overall number of reference technical actions within a shift
RTA
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ISO 11228-3:2007(E)
n number of technical actions in a cycle
TC
OCRA occupational repetitive action
PA prevalence (%) of persons affected
P posture multiplier
M
PTS predetermined time system
RTA reference technical action
R repetitiveness multiplier
eM
R recovery multiplier
cM
SE standard error
t net duration of each repetitive task, in minutes
t cycle time, in seconds
C
TA technical action
t duration multiplier
M
UL-WMSD upper limb work-related musculoskeletal disorders
WF work factor
4 Recommendations
4.1 Avoiding repetitive handling tasks
Hazardous manual handling tasks should be avoided wherever possible. This can be achieved through work
enlargements, job rotation and/or mechanization/automation within the framework of a participative
ergonomics approach. In the case of repetitive handling of low loads at high frequency, many tasks can be
modified through the use of robotics or automated production systems.
NOTE A “participative ergonomics approach” signifies the practical involvement of workers, supported by suitable
communication, in planning and managing a significant amount of their work activities, with sufficient knowledge and ability
to influence both processes and outcomes in order to achieve desirable goals.
4.2 Risk assessment
4.2.1 General
When repetitive handling is unavoidable, a four-step approach in accordance with ISO Guide 51 and
ISO 14121, and involving both risk assessment and risk reduction, should be adopted. The four steps are
hazard identification, risk estimation, risk evaluation and risk reduction.
The procedure shown in Figure 1 should be adopted when carrying out a risk assessment of jobs involving the
manual handling of low loads at high frequency.
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ISO 11228-3:2007(E)

Figure 1 — Risk assessment procedure


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ISO 11228-3:2007(E)
4.2.2 Hazard identification
4.2.2.1 General
The first step of the risk assessment is to identify whether hazards exist which may expose individuals to a
risk of injury. If such hazards are present, then a more detailed risk assessment can be necessary. When
determining if one or more of the following hazards is present, consideration should be given to the guidelines
for avoiding them.
4.2.2.2 Repetition
Frequent repetitive movements give rise to a risk of injury that can vary depending on the context of the
movement pattern and the individual. As the movement cycle increases and/or the cycle time decreases, the
risk of injury increases. Repetitive movements should be avoided within a task or job.
4.2.2.3 Posture and movement
Sitting restricts overall movement of the body, particularly those of the lower leg and back. This may lead to
increased and complex loading of the back and upper extremities. Standing for prolonged periods of time
often results in pain/discomfort in the legs and lower back and can lead to venous pooling in the legs.
Complex postures involving combined movements (e.g. flexed and twisted) can present greater risk (see
ISO 11226). Whenever possible, workers should be given the option to vary between sitting and standing.
Work tasks and operations should provide variations to the working posture: both whole-body postures and
movement of specific limbs. In the work tasks, extreme ranges of joint movement should be avoided; there is
also need to avoid prolonged static postures.
4.2.2.4 Force
Forceful exertions can be harmful. Tasks should involve smooth force exertions, with the avoidance of sudden
or jerky movements. Handling precision (accurate picking and placement), and the type and nature of the grip
can introduce additional muscular activation.
4.2.2.5 Duration and insufficient recovery
Insufficient time for the body to recover between repetitive movements (i.e. lack of recovery time) increases
the risk of injury. Duration can be broken down into different levels, i.e. work shift duration, job duration, task
duration. The opportunity for recovery or rest may fall within each of these work periods.
4.2.2.6 Object characteristics
Inappropriately designed objects could have characteristics that can cause harm (e.g. contact forces, shape,
dimensions, coupling, object temperature). Inappropriately placed handholds may lead to awkward hand/arm
postures. Non-cushioned handholds and objects constructed of a smooth material increase the difficulty of
grasping the object and increase force requirements. The size and shape of the object being handled and the
coupling between it and the operator’s hands will determine the grip type and the force that the operator must
exert.
4.2.2.7 Vibration and impact forces
Exposure to hand/arm vibration, shocks or impacts can lead to a desensitizing of the hand and increase the
force necessary for gripping an object or tool. Prolonged exposure to these types of risk factors has also been
linked to vascular and neurological disorders of the upper limbs.
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ISO 11228-3:2007(E)
4.2.2.8 Environmental conditions (lighting, climate, noise, etc.)
Inappropriate lighting, hot and cold environments and high levels of noise can impose additional hazards. Wet
or contaminated surfaces are likely to inhibit the ability to exert forces and increase the risk of injury. The
designer of products shall consider environmental conditions only within the limits of the foreseeable use of
the product.
4.2.2.9 Work organization
Work organization (e.g. task duration, job duration, recovery time, shift patterns) has an important part to play
in the exposure to musculoskeletal risk factors. This should be structured to facilitate rest periods and avoid
the use of similar muscle groups over the duration of the work shift. Job rotation, job diversification and job
enlargement are all methods of structuring the work to facilitate variation and recovery within the work period.
4.2.2.10 Psychosocial factors (e.g. job complexity, job demands, job content)
Psychological response to work and workplace conditions has an important influence on general health and,
in particular, musculoskeletal health. These factors include the design, organization and management of work,
the specific impact of workplace risk factors, such as work content, and the overall social environment (i.e. the
context of work). Many of the effects of these psychosocial factors occur via stress-related processes, which
can have a direct effect on biochemical and physiological responses.
4.2.2.11 Individuals
Individual skills, training, age, gender, health problems and pregnancy are personal characteristics that can
influence performance and should be considered in the risk assessment. Skill and experience are likely to
benefit the individual when performing the task and reduce the risk of injury. Training can increase the level of
skill.
Important aspects of work design include the amount of control an individual has over his/her work, the level
of work demands, the variety of tasks he/she is required to perform and the level of support provided by
managers, supervisors and/or co-workers. Undesirable psychosocial aspects of a job contributing to a risk of
musculoskeletal disorders include the following:
⎯ workers have little or no control over their work and work methods or organization;
⎯ tasks require high levels of attention and concentration;
⎯ workers are unable to make full use of their skills;
⎯ workers have little or no involvement in decision making;
⎯ workers are expected to carry out repetitive, monotonous tasks exclusively;
⎯ work is machine- or system-paced;
⎯ work demands are perceived as excessive;
⎯ payment systems encourage working too quickly or without breaks;
⎯ work systems limit opportunities for social interaction;
⎯ high levels of effort are not balanced by sufficient reward (resources, remuneration, self-esteem, status,
etc.).
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ISO 11228-3:2007(E)
4.2.3 Risk estimation
4.2.3.1 Method 1 — Simple risk assessment
Risk estimation is performed by a simple risk assessment of jobs composed by a single repetitive task
(monotask jobs).
The procedure and checklist model presented in Annex B is preferred for the carrying out of the simple risk
assessment. There are four parts to this assessment procedure:
⎯ preliminary information describing the job task;
⎯ hazard identification and risk estimation procedure and checklist;
⎯ overall evaluation of the risk;
⎯ remedial action to be taken.
NOTE As a second choice, other simple methods and checklists given in Annex A can be used, taking into
consideration the specific characteristics of the repetitive task under examination.
Risk estimation using Method 1 should allow the classification of the risk by the three-zone approach (green,
yellow and red) and determine the consequent action to be taken. The three risk zones are defined as follows.
a) Green zone (acceptable risk)
The risk of disease or injury is negligible or is at an acceptably low level for the entire working population.
No action is required.
b) Yellow zone (conditionally acceptable risk)
There is a risk of disease or injury that cannot be neglected for the entire working population or part of it.
The risk shall be further estimated (using the more detailed assessment of Method 2), analysed together
with contributory risk factors and followed as soon as possible by redesign. Where redesign is not
possible, other measures to control the risk shall be taken.
c) Red zone (not acceptable)
There is a considerable risk of disease or injury that cannot be neglected for the operator population.
Immediate action to reduce the risk (e.g. redesign, work organization, worker instruction and training) is
necessary (see 4.3 and Annex E).
4.2.3.2 Method 2 — Detailed risk assessment
4.2.3.2.1 General criteria
If the risk estimated using Method 1 is considered to be YELLOW or RED, or if the job is composed of two or
more repetitive tasks (multitask job), the performing of a more detailed risk assessment is recommended. This
will also allow a better determination of the remedial measures to be taken.
For detailed risk assessment, OCRA (occupational repetitive action) is the preferred method (see 4.2.3.2.2). It
is recommended for the specific purposes of this part of ISO 11228 because, given the knowledge at the time
of publication, it considers all the relevant risk factors, is also applicable to “multitask jobs”, and provides
criteria — based on extensive epidemiological data — for forecasting the occurrence of UL-WMSD (upper
limb work-related musculoskeletal disorders) in exposed working populations.
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ISO 11228-3:2007(E)
Other detailed risk assessment methods are available which can be used for a detailed risk assessment,
depending on the kind of risk factors identified by Method 1, the nature of the job and the experience of the
analyst.
Annex D gives basic information about other detailed risk assessment methods useful for the purposes of this
part of ISO 11228, together with some remarks about their applicative limits at the time of publication.
Whichever method is used for detailed risk assessment, it should allow the classification of the risk by the
three-zone model and determine the consequences to be acted upon in accordance with Table 1.
Table 1 — Method 2 — Final assessment criteria
Zone Risk level Consequences
Green No risk Acceptable: no consequences
Improve structural risk factors (posture, force, technical actions, etc.)
Yellow Very low risk
or take other organizational measures
Red Risk Redesign tasks and workplaces according to priorities

4.2.3.2.2 OCRA method for detailed risk assessment
The OCRA index is the ratio between the number of actual technical actions, ATA, carried out during a work
shift and the number of reference technical actions, RTA, for each upper limb, specifically determined in the
[11], [38]
scenario under examination .
The OCRA risk assessment procedure consists of three basic steps:
a) Step 1
Calculate the frequency of technical actions/min and the overall number of ATA carried out in the shift (by
each upper limb).
b) Step 2
Calculate the overall number of RTA.
c) Step 3
Calculate the OCRA index and perform a risk evaluation.
Table 2 (ATA and RTA calculation in monotask jobs), Table 3 (ATA and RTA calculation in multitask jobs) and
Table 4 (OCRA index calculation and risk evaluation) give an overview of the procedure detailed in Annex C.
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ISO 11228-3:2007(E)
Table 2 — OCRA assessment procedure for monotask jobs — Steps 1 and 2
Calculate the overall number of actual technical actions, n , carried out in a shift by each upper limb.
Step1
ATA
a) Count the number of technical actions, n , in a cycle.
TC
Evaluate their frequency, f, per minute, considering the cycle time, t , in seconds:
b)
C

60
fn=×
TC
t

C
c) Evaluate the net duration, t, of the repetitive task in the shift, in minutes.
d) Calculate the overall number of ATA carried out in the shift:

n = f × t
ATA
Step 2 Calculate the overall number of RTA within the shift:
n = k × F × P × R × A × t × R × t
RTA f M M eM M cM M
Constant of frequency, k , of technical actions = 30/min

30
f

×
F Force multiplier
M
×
P Posture multiplier
M
×
R Repetitiveness multiplier
eM

×
A Additional multiplier
M
×
t
Duration of the repetitive task, in minutes
=
n Partial reference number of technical actions in the shift
RPA
×
t
Duration multiplier
M

×
R Recovery multiplier
cM
=

n
Overall number of RTA
RTA
NOTE See 3.2. for the complete list of symbols and abbreviated terms used in this part of ISO 11228.

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ISO 11228-3:2007(E)
Table 3 — OCRA assessment procedure for multitask jobs — Steps 1 and 2
Calculate the overall number of actual technical actions, n , carried out in a shift by each upper limb,
ATA
Step1
considering each repetitive task, j, in the shift.
a) Count the number of technical actions in a cycle for each repetitive task (n ):
TCj
Task A Task B Task C Task n
n n n n
TC TC TC TC
Evaluate the frequency of action per minute for each repetitive task, f , considering the cycle time for
b)
j
each repetitive task, t , in seconds:
Cj
Task A Task B Task C Task n
f f f f
c) Evaluate the net duration (t ) of each repetitive task in the shift, in minutes.
j
Task A Task B Task C Task n
t t t t
d) Calculate the overall number of ATA carried out in each repeti
...

NORME ISO
INTERNATIONALE 11228-3
Première édition
2007-04-01

Ergonomie — Manutention manuelle —
Partie 3:
Manipulation de charges faibles à
fréquence de répétition élevée
Ergonomics — Manual handling —
Part 3: Handling of low loads at high frequency





Numéro de référence
ISO 11228-3:2007(F)
©
ISO 2007

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ISO 11228-3:2007(F)
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ii © ISO 2007 – Tous droits réservés

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ISO 11228-3:2007(F)
Sommaire Page
Avant-propos. iv
Introduction . v
1 Domaine d'application. 1
2 Références normatives . 1
3 Termes, définitions, symboles et termes abrégés . 2
3.1 Termes et définitions. 2
3.2 Symboles et termes abrégés . 3
4 Recommandations. 4
4.1 Éviter les tâches de manutention répétitives .4
4.2 Évaluation des risques. 4
4.2.1 Généralités . 4
4.2.2 Identification des phénomènes dangereux. 6
4.2.2.1 Généralités. 6
4.2.2.2 Répétition. 6
4.2.2.3 Posture et mouvement. 6
4.2.2.4 Force. 6
4.2.2.5 Durée et récupération insuffisante.6
4.2.2.6 Caractéristiques des objets . 6
4.2.2.7 Vibrations et forces de choc . 7
4.2.2.8 Conditions ambiantes (éclairage, climat, bruit, etc.). 7
4.2.2.9 Organisation du travail . 7
4.2.2.10 Facteurs psychosociaux (par exemple complexité, exigences et contenu des postes
de travail) . 7
4.2.2.11 Individu. 7
4.2.3 Méthodes d'évaluation des risques . 8
4.2.3.1 Méthode 1 — Évaluation simple des risques . 8
4.2.3.2 Méthode 2 — Évaluation détaillée des risques . 9
4.3 Réduction des risques . 12
Annexe A (informative) Évaluation des risques — Cadre général et informations relatives aux
méthodes existantes . 13
Annexe B (informative) Méthode 1 — Évaluation simple des risques — Liste de contrôle pour
l'évaluation . 16
Annexe C (informative) Méthode 2 — Méthode OCRA pour l'évaluation détaillée des risques. 25
Annexe D (informative) Autres méthodes d'évaluation détaillée des risques . 68
Annexe E (informative) Réduction des risques. 73
Bibliographie . 76

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ISO 11228-3:2007(F)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de
normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée
aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du
comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,
Partie 2.
La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes
internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres
votants.
L'attention est appelée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable de ne
pas avoir identifié de tels droits de propriété et averti de leur existence.
L'ISO 11228-3 a été élaborée par le comité technique ISO/TC 159, Ergonomie, sous-comité SC 3,
Anthropométrie et biomécanique.
L'ISO 11228 comprend les parties suivantes, présentées sous le titre général Ergonomie — Manutention
manuelle:
⎯ Partie 1: Manutention verticale et manutention horizontale
⎯ Partie 2: Actions de pousser et de tirer
⎯ Partie 3: Manipulation de charges faibles à fréquence de répétition élevée
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ISO 11228-3:2007(F)
Introduction
La manipulation de charges faibles à fréquence de répétition élevée (travail répétitif) peut provoquer une
douleur et de la fatigue, susceptibles à leur tour d'entraîner des troubles musculosquelettiques, une réduction
de la productivité et une détérioration de la coordination des postures et des mouvements. Ce dernier élément
peut augmenter le risque d'erreurs et peut aboutir à une réduction de la qualité et entraîner des situations
dangereuses. Une conception ergonomique correcte et une organisation des tâches appropriée constituent
les prescriptions de base qui permettent d'éviter les effets nocifs mentionnés.
Les facteurs de risques liés à un travail répétitif incluent la fréquence des actions, la durée d'exposition, les
postures et le mouvement des segments du corps, les forces associées au travail, l'organisation du travail, la
gestion des tâches, les sollicitations en termes de résultat (par exemple qualité, précision des tâches) et le
niveau de formation/compétence. Les facteurs additionnels peuvent inclure les facteurs liés à l'environnement
comme le climat, le bruit, les vibrations et l'éclairage.
Les recommandations de la présente partie de l'ISO 11228 sont basées sur les preuves scientifiques
disponibles concernant la physiologie et l'épidémiologie du travail manuel. Les connaissances sont toutefois
limitées et les recommandations proposées sont susceptibles de modification en fonction des travaux de
recherche futurs.

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NORME INTERNATIONALE ISO 11228-3:2007(F)

Ergonomie — Manutention manuelle —
Partie 3:
Manipulation de charges faibles à fréquence de répétition
élevée
1 Domaine d'application
La présente partie de l'ISO 11228 détermine les recommandations ergonomiques applicables aux tâches
répétitives qui impliquent la manipulation de charges faibles à fréquence de répétition élevée. Elle fournit des
recommandations concernant l'identification et l'évaluation des facteurs de risques couramment associés à la
manipulation de charges faibles à fréquence de répétition élevée, qui permettent ainsi d'apprécier les risques
pour la santé de la population active. Les recommandations s'appliquent à la population active adulte et les
recommandations fournies sont destinées à assurer une protection suffisante de la quasi-totalité des adultes
en bonne santé. Ces recommandations concernant les risques pour la santé et les mesures de contrôle
reposent principalement sur les études expérimentales portant sur la charge musculosquelettique, la
gêne/douleur et l'endurance/fatigue associées aux méthodes de travail. Pour l'évaluation des postures de
travail, se reporter à l'ISO 11226.
La présente partie de l'ISO 11228 est prévue pour fournir des informations destinées à toutes les personnes
concernées par la conception initiale ou une nouvelle conception du travail, des tâches et des produits.
2 Références normatives
Les documents de référence suivants sont indispensables pour l'application du présent document. Pour les
références datées, seule l'édition citée s'applique. Pour les références non datées, la dernière édition du
document de référence s'applique (y compris les éventuels amendements).
ISO 6385, Principes ergonomiques de la conception des systèmes de travail
ISO 11226, Ergonomie — Évaluation des postures de travail statiques
ISO 11228-1, Ergonomie — Manutention manuelle — Partie 1: Manutention verticale et manutention
horizontale
ISO 11228-2, Ergonomie — Manutention manuelle — Partie 2: Actions de pousser et de tirer
ISO 14738, Sécurité des machines — Prescriptions anthropométriques relatives à la conception des postes
de travail sur les machines
ISO 15534 (toutes les parties), Conception ergonomique pour la sécurité des machines
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ISO 11228-3:2007(F)
3 Termes, définitions, symboles et termes abrégés
Pour les besoins du présent document, les termes et définitions donnés dans l'ISO 6385, l'ISO 11228-1,
l'ISO 11228-2 et l'ISO 11226 ainsi que les termes, définitions, symboles et termes abrégés suivants
s'appliquent.
NOTE Dans les définitions impliquant la fréquence, une unité de temps est mentionnée parce que plusieurs
méthodes sont appliquées, chacune utilisant des unités de temps différentes, par exemples secondes avec la méthode
HAL (voir Annexe D), minutes avec l'indice OCRA (voir Annexe C) et l'indice de déformation (voir Annexe D).
3.1 Termes et définitions
3.1.1
tâche répétitive
tâche caractérisée par des cycles de travail répétés
3.1.2
cycle de travail
séquence d'actions (techniques) répétées toujours de la même manière
3.1.3
temps de cycle
t
C
temps, en secondes, qui s'écoule entre le moment où un opérateur entame un cycle de travail et le moment
de répétition du même cycle de travail
3.1.4
action technique
actions manuelles élémentaires requises pour achever les opérations inhérentes au cycle
EXEMPLE Maintenir, tourner, pousser et couper.
3.1.5
répétitivité
caractéristique d'une tâche pour laquelle une personne répète de manière continue le même cycle de travail
et les mêmes actions techniques et mouvements
3.1.6
fréquence d'actions
nombre d'actions techniques par unité de temps
3.1.7
force
F
effort physique de l'opérateur nécessaire à l'exécution de la tâche
3.1.8
postures et mouvements
positions et mouvements du ou des segments du corps ou de la ou des articulations, nécessaires à
l'exécution de la tâche
3.1.9
temps de récupération
période de repos succédant à une période d'activité qui permet le recouvrement de la fonction
musculosquelettique (en minutes)
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3.1.10
facteur de risque additionnel
objet et facteurs liés à l'environnement dont il est prouvé qu'ils entraînent une relation, ou aggravent la relation
existante, avec les troubles musculosquelettiques des membres supérieurs liés au travail
EXEMPLE Vibration, pression locale, environnement froid ou surfaces froides.
3.1.11
déplacement
transport d'un objet vers une destination donnée, en utilisant les membres supérieurs et sans marcher
3.1.12
atteinte
déplacement de la main vers une destination prédéfinie
3.1.13
acheminement
transport d'un objet vers une destination donnée, en marchant
3.2 Symboles et termes abrégés
A multiplicateur additionnel
M
ATA action technique réelle
f fréquence d'actions par minute
F force (N)
F limite de force de base
B
F limite de force
L
F multiplicateur de force
M
j tâches répétitives génériques
k constance de fréquence des actions techniques par minute
f
L charge réelle
MODA PTS système de temps prédéterminé pour analyse modulaire
MSD troubles musculosquelettiques
MTA analyse des temps de mouvements
MTM mesure des temps et mouvements
MVC contraction volontaire maximale
n nombre d'actions techniques réelles par poste
ATA
n nombre de personnes exposées
ep
n nombre de personnes affectées par un ou plusieurs UL-WMSD
pa
n nombre de référence partiel d'actions techniques par poste
RPA
n nombre de tâche(s) répétitive(s) exécutée(s) au cours d'un poste
rt
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ISO 11228-3:2007(F)
n nombre d'actions techniques de référence par poste
RTA
n nombre d'actions techniques dans le cycle
TC
OCRA action répétitive professionnelle
PA prévalence (%) de personnes affectées
P multiplicateur de posture
M
PTS système de temps prédéterminé
RTA action technique de référence
R multiplicateur de répétitivité
eM
R multiplicateur de récupération
cM
SE erreur type
t durée nette de chaque tâche répétitive, en minutes
t temps de cycle, en secondes
C
TA action technique
t multiplicateur de durée
M
UL-WMSD troubles musculosquelettiques des membres supérieurs liés au travail
WF facteur de travail
4 Recommandations
4.1 Éviter les tâches de manutention répétitives
Il convient dans toute la mesure du possible d'éviter les tâches de manutention manuelle dangereuses.
L'extension des tâches, la rotation des postes et/ou la mécanisation/automatisation dans le cadre d'une
ergonomie participative permettent d'éviter ce type de tâches. Dans le cas d'une manipulation répétitive de
charges faibles à fréquence de répétition élevée, de nombreuses tâches peuvent être modifiées grâce à
l'utilisation de la robotique ou de systèmes de production automatisés.
NOTE L'approche ergonomique participative représente l'implication pratique des travailleurs, soutenue par une
communication appropriée dans la planification et la gestion d'une quantité significative de leurs activités de travail, avec
une connaissance suffisante et la capacité à influer à la fois sur les procédés et les résultats de manière à atteindre les
objectifs souhaitables.
4.2 Évaluation des risques
4.2.1 Généralités
Il convient d'adopter une approche d'évaluation et de réduction des risques lorsqu'une manutention répétitive
ne peut être évitée. Conformément au Guide 51 de l'ISO et à l'ISO 14121, cette approche s'articule
généralement en quatre phases: identification des phénomènes dangereux, estimation des risques,
évaluation des risques et réduction des risques.
Il convient d'adopter la procédure suivante pour l'évaluation des risques liés aux tâches qui impliquent la
manutention manuelle de charges faibles à fréquence de répétition élevée (voir Figure 1).
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ISO 11228-3:2007(F)

Figure 1 — Procédure d'évaluation des risques


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ISO 11228-3:2007(F)
4.2.2 Identification des phénomènes dangereux
4.2.2.1 Généralités
La première phase d'évaluation des risques consiste à identifier s'il existe des phénomènes dangereux
susceptibles d'exposer les individus à un risque de lésion. Si de tels phénomènes existent, une évaluation des
risques plus détaillée peut alors se révéler nécessaire. Il convient d'accorder une attention toute particulière
aux recommandations qui permettent d'éviter les phénomènes dangereux lorsqu'il s'agit de déterminer
l'existence éventuelle d'un ou de plusieurs phénomènes dangereux décrits ci-dessous.
4.2.2.2 Répétition
Des mouvements répétitifs fréquents provoquent un risque de lésion susceptible de varier selon le contexte
des mouvements types et de l'individu. L'augmentation du risque de lésion est proportionnelle à
l'augmentation du cycle de mouvement et/ou à la réduction de la durée du cycle. Il convient qu'une tâche/un
travail spécifique évite les mouvements répétitifs.
4.2.2.3 Posture et mouvement
La position assise limite le mouvement de l'ensemble du corps, en particulier celui de la jambe et du bas du
dos. Ceci peut entraîner une plus grande charge complexe exercée sur le dos et les membres supérieurs. La
position debout pendant des périodes prolongées entraîne souvent une douleur/gêne ressentie au niveau des
jambes et du bas du dos et peut aboutir à une congestion veineuse des jambes. Des postures complexes
impliquant la combinaison de mouvements (par exemple flexion et torsion) peuvent présenter un risque plus
élevé (voir l'ISO 11226). Il convient dans toute la mesure du possible de permettre aux travailleurs de choisir
entre la position assise et la position debout.
Il convient que les tâches et les opérations liées au travail prévoient des postures de travail
différentes: c'est-à-dire à la fois des postures du corps entier et le mouvement de membres spécifiques. Il
convient d'éviter tout mouvement extrême des articulations dans l'exécution des tâches, de même qu'il est
nécessaire d'éviter les postures statiques prolongées.
4.2.2.4 Force
Des efforts sous forte pression peuvent se révéler dangereux. Il convient que les tâches impliquent des efforts
sous faible pression, en évitant les mouvements soudains ou brusques. La précision de manutention (saisie et
mise en place précises), ainsi que le type et la nature de la préhension peuvent entraîner une activation
musculaire supplémentaire.
4.2.2.5 Durée et récupération insuffisante
Un temps de récupération insuffisant du corps entre des mouvements répétitifs (c'est-à-dire absence de
temps de récupération) augmente le risque de lésion. La durée peut être répartie en différents niveaux,
c'est-à-dire durée des postes, des travaux ou des tâches. La possibilité de récupération ou de repos peut
s'inscrire dans chacune de ces périodes de travail.
4.2.2.6 Caractéristiques des objets
Les caractéristiques des objets dont la conception est inappropriée peuvent représenter une source de
danger (par exemple efforts de contact, forme, dimensions, accouplement, température de l'objet). Des
poignées mal placées peuvent conduire à des postures des mains/bras inconfortables. Des poignées rigides
et des objets constitués d'une matière lisse augmentent la difficulté de préhension de l'objet et accroissent les
forces nécessaires. La dimension et la forme de l'objet manutentionné et l'interface entre ce dernier et les
mains de l'opérateur déterminent le type de préhension ainsi que la force que doit exercer ce même opérateur.
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ISO 11228-3:2007(F)
4.2.2.7 Vibrations et forces de choc
L'exposition à des vibrations main/bras, des chocs ou des impacts peut entraîner une désensibilisation de la
main et accroître la force nécessaire à la préhension d'un objet ou d'un outil. Une exposition prolongée à ces
types de facteurs de risque est également liée à des troubles vasculaires et neurologiques des membres
supérieurs.
4.2.2.8 Conditions ambiantes (éclairage, climat, bruit, etc.)
Un éclairage inapproprié, des environnements chauds et froids et des niveaux de bruit élevés peuvent
entraîner des phénomènes dangereux supplémentaires. Les surfaces humides ou contaminées sont
susceptibles de neutraliser la capacité à exercer des forces et d'augmenter le risque de lésion. Le concepteur
des produits doit tenir compte des conditions ambiantes uniquement dans les limites de l'utilisation prévisible
du produit.
4.2.2.9 Organisation du travail
L'organisation du travail (par exemple durée de la tâche ou du travail, temps de récupération, types de poste
de travail) a un rôle important dans l'exposition aux facteurs de risques musculosquelettiques. Il convient de
structurer l'organisation du travail afin de faciliter les périodes de repos et d'éviter l'utilisation de groupes
musculaires similaires pendant la durée du poste de travail. Le roulement, la diversification et l'extension des
tâches constituent autant de méthodes de structuration du travail destinées à faciliter la variation et la
récupération pendant la période de travail.
4.2.2.10 Facteurs psychosociaux (par exemple complexité, exigences et contenu des postes de
travail)
La réponse psychologique aux conditions de travail et du lieu de travail a une influence considérable sur la
santé générale de l'opérateur et, plus particulièrement, sur la santé musculosquelettique de ce dernier. Ces
facteurs incluent la conception, l'organisation et la gestion du travail, l'impact spécifique des facteurs de risque
sur le lieu de travail, tels que le contenu de la tâche et l'environnement social dans son ensemble (c'est-à-dire
le contexte de travail). Bon nombre des effets de ces facteurs psychosociaux ont pour origine des procédés
associés au stress qui peuvent avoir un effet direct sur les réponses biochimique et physiologique.
4.2.2.11 Individu
Les compétences personnelles, la formation, l'âge, le sexe, les problèmes sanitaires et la grossesse
constituent des caractéristiques individuelles susceptibles d'influencer l'exécution du travail et qu'il convient de
prendre en considération dans l'évaluation des risques. Les compétences et l'expérience sont susceptibles de
représenter un avantage pour l'individu qui exécute une tâche et de réduire le risque de lésion. La formation
peut augmenter le niveau de compétence.
Les aspects importants de la conception des tâches incluent le niveau de contrôle qu'exerce un individu sur
son travail, le niveau des besoins en termes de travail, la diversité des tâches que doivent exécuter les
individus et le niveau de soutien assuré par les dirigeants, superviseurs et/ou collègues de travail. Les
aspects psychosociaux non souhaitables d'une tâche qui contribuent à un risque de troubles
musculosquelettiques sont les suivants:
⎯ les travailleurs n'exercent qu'un contrôle limité ou n'exercent aucun contrôle sur leur travail, ainsi que sur
les méthodes ou l'organisation du travail;
⎯ les tâches requièrent des niveaux élevés d'attention et de concentration;
⎯ les travailleurs ne sont pas capables d'utiliser au mieux leurs compétences;
⎯ les travailleurs ne sont guère ou ne sont pas impliqués dans la prise de décisions;
⎯ il est prévu que les travailleurs effectuent des tâches monotones et répétitives exclusivement;
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ISO 11228-3:2007(F)
⎯ l'exécution des tâches est entraînée par une machine ou un système;
⎯ les sollicitations en termes de travail sont considérées comme excessives;
⎯ les systèmes de paiement encouragent un rythme de travail trop rapide ou sans pauses;
⎯ les systèmes de travail limitent les possibilités d'une interaction sociale;
⎯ les niveaux d'effort élevés ne sont pas compensés par un mode de récompense suffisant (ressources,
rémunération, estime de soi, statut, etc.).
4.2.3 Méthodes d'évaluation des risques
4.2.3.1 Méthode 1 — Évaluation simple des risques
L'estimation des risques consiste en une évaluation simple des risques liés aux activités comprenant une
seule tâche répétitive (activités à tâche unique).
Il est préférable d'utiliser la procédure et le modèle de liste de contrôle définis dans l'Annexe B pour
l'évaluation simple des risques. La procédure d'évaluation des risques comporte quatre parties:
⎯ informations préliminaires décrivant l'activité;
⎯ identification des phénomènes dangereux et procédure d'estimation des risques et liste de contrôle;
⎯ évaluation globale des risques;
⎯ mesure de correction à prendre.
NOTE En second choix, les autres méthodes simples et listes de contrôle mentionnées dans l'Annexe A peuvent être
utilisées, en prenant en considération les caractéristiques spécifiques de la tâche répétitive examinée.
Il convient que l'estimation des risques au moyen de la Méthode 1 permette la classification du risque par
l'approche des trois zones (verte, jaune, rouge) et traite de l'action conséquente à prendre. Les trois zones de
risque sont définies comme suit.
a) Zone verte (risque acceptable)
Le risque de maladie ou de blessure est négligeable ou à un niveau bas acceptable pour la population
active dans son ensemble. Aucune action n'est requise.
b) Zone jaune (risque acceptable sous conditions)
Il existe un risque de maladie ou de blessure qui ne peut être négligé pour la population active dans on
ensemble ou pour une partie de celle-là. Les risques doivent être estimés plus profondément (utilisant
l'évaluation plus détaillée de la Méthode 2), analysés ensemble avec les facteurs de risque concourants
et conduisant, aussi rapidement que possible, à une nouvelle conception. Si une nouvelle conception est
impossible, de nouvelles mesures pour contrôler les risques doivent être prises.
c) Zone rouge (inacceptable)
Il existe un risque considérable de maladie ou de blessure qui ne peut pas être négligé pour la population
active. Il est nécessaire de prendre des mesures immédiates pour réduire le risque (par exemple nouvelle
conception, organisation du travail, formation et entraînement du personnel) (voir 5.3 et Annexe E).
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ISO 11228-3:2007(F)
4.2.3.2 Méthode 2 — Évaluation détaillée des risques
4.2.3.2.1 Critères généraux
Si le risque déterminé au moyen de la méthode d'estimation 1 se situe dans la zone JAUNE ou ROUGE, ou si
l'activité comprend deux tâches répétitives ou plus (activité multitâche), il est recommandé d'effectuer une
évaluation des risques plus détaillée. Cette évaluation permettra également de déterminer de m
...