Ergonomic procedures for the improvement of local muscular workloads — Part 1: Guidelines for reducing local muscular workloads
ISO/TS 20646-1:2004 provides information and guidelines to properly utilise various ergonomics standards concerning the factors related to local muscular workload (LMWL), and helps develop activities to reduce LMWL in workplaces, in an effective and efficient manner. ISO/TS 20646-1:2004 is intended primarily for employers, ergonomics and occupational health-related staff in enterprises, and workers. Specific measures to reduce LMWL can be applied to non-professional activities. Although ISO/TS 20646-1:2004 provides ideas of effective and efficient measures to reduce LMWL, it does not certify the complete prevention of health problems caused by LMWL.
Procédures ergonomiques pour l'amélioration des charges de travail musculaire locales — Partie 1: Lignes directrices pour réduire les charges de travail musculaire
Standards Content (Sample)
Ergonomic procedures for the
improvement of local muscular
Guidelines for reducing local muscular
Procédures ergonomiques pour l'amélioration des charges de travail
musculaire locales —
Partie 1: Lignes directrices pour réduire les charges de travail
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Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 General guiding principles. 2
4.1 Basic principles to reduce LMWL . 2
4.2 Basic framework and responsibilities of LMWL-reduction activities. 2
4.2.1 Organization at the enterprise level . 3
4.2.2 Organization at the department level. 3
4.2.3 Advisory organization. 3
4.3 Processes for LMWL risk assessment including implementation of risk reduction activity. 3
4.3.1 Risk analysis. 3
4.3.2 Specifying risk reduction measures followed by a small trial of the improvement. 5
4.3.3 Implementation of risk reduction measures and monitoring of the effect of the activity . 5
4.3.4 Risk evaluation and drafting of new risk reduction plans . 6
Annex A (informative) Schedule form for principles, plan and implementation. 7
Annex B (informative) Checklist for hazard identification concerning local muscular workload. 8
Annex C (informative) Action-oriented checklist . 11
Annex D (informative) Questionnaire for monitoring the effects and insufficiency of risk reduction
measures concerning local muscular workloads. 14
Annex E (informative) Evaluation form for the risk reduction activity. 16
Bibliography . 17
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ISO/TS 20646-1 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 3,
Anthropometry and biomechanics.
ISO/TS 20646 consists of the following parts, under the general title Ergonomic procedures for the
improvement of local muscular workloads:
Part 1: Guidelines for reducing local muscular workloads
Part 2: Practical use of the guidelines given in Part 1
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The onset of work-related musculoskeletal disorders, such as lower-back pain and cumulative trauma
disorders, is becoming a great ergonomic concern in both industrialised and industrialising countries. The high
incidence of work-related musculoskeletal disorders is an important problem to be solved not only to improve
workers' health and the quality of working life, but also to improve productivity.
In order to solve the problem of work-related musculoskeletal disorders, it is important to work out primary
preventive measures, through improving working conditions and providing adequate health guidance and
training, as well as to establish measures for secondary prevention, treatment, and reassignment of the
workers after a long sick leave.
Above all, the establishment of primary preventive measures, mainly measures to reduce local muscular
workloads (LMWL) is considered the most effective and economic solution, in the context of cost-efficiency as
well as a better quality of working life. Various activities to reduce LMWL have already been promoted. In
addition, regarding ISO/TC 159/SC 3, new standards are being prepared to improve working conditions
relating to the factors causing LMWL. However, in order to reduce LMWL, it is indispensable to take a
comprehensive work-related perspective and find a solution, in consideration of the aforementioned factors.
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TECHNICAL SPECIFICATION ISO/TS 20646-1:2004(E)
Ergonomic procedures for the improvement of local muscular
Guidelines for reducing local muscular workloads
This part of ISO 20646 provides information and guidelines to properly utilise various ergonomics standards
concerning the factors related to local muscular workload (LMWL), and helps develop activities to reduce
LMWL in workplaces, in an effective and efficient manner. This part of ISO 20646 is intended primarily for
employers, ergonomics and occupational health-related staff in enterprises, and workers. Specific measures
to reduce LMWL can be applied to non-professional activities. Although this part of ISO 20646 provides ideas
of effective and efficient measures to reduce LMWL, it does not certify the complete prevention of health
problems caused by LMWL.
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 11226, Ergonomics — Evaluation of static working postures
ISO 11228-1, Ergonomics — Manual handling — Part 1: Lifting and carrying
ISO 12100-1:2003, Safety of machinery — Basic concepts, general principles for design — Part 1: Basic
ISO 14121, Safety of machinery — Principles of risk assessment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
local muscular workload
loads on the musculoskeletal system required for working motions, maintaining working postures and exerting
physical injury or damage to health
potential source of harm
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combination of the probability of occurrence of harm and the severity of that harm
overall process comprising a risk analysis, risk reduction measure and risk evaluation
NOTE Adapted from ISO 12100-1:2003.
combination of the specification of work situation, hazard identification and risk estimation
defining likely severity of harm and probability of its occurrence
judgement, on the basis of successive risk analysis, of whether the risk reduction objectives have been
volume of space allocated to one or more persons in the work system to complete a work task
combination of work equipment for a particular person in a work space
NOTE It is possible that several persons share a particular workstation, or that several persons alternate between
several workstations within any period of time (i.e. hourly, daily, weekly basis).
4 General guiding principles
4.1 Basic principles to reduce LMWL
The management should clarify existing and predicted LMWL, possible health- and productivity-related
problems, and publish improvement goals and targets, a basic schedule to achieve the targets, and the
organization to implement the improvement, in writing (see Annex A).
4.2 Basic framework and responsibilities of LMWL-reduction activities
As organizations draft, implement and assess LMWL-reduction plans, organizations at the enterprise level and
department level, and advisory organizations, should develop activities in a collaborative manner.
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4.2.1 Organization at the enterprise level
An organization to manage LMWL problems should be established at the enterprise level, either as part of
existing management systems for work design or occupational safety and health, or as a specifically
designated project activity. The owner or executive director with overall management authority shall be
responsible for the establishment and the conduct of this organization.
4.2.2 Organization at the department level
This refers to an organization within an individual department, for which the departmental manager should be
responsible. Its function is to draft, implement and assess the improvement plans for the department.
4.2.3 Advisory organization
This refers to an organization offering advice concerning the validity of drafting, implementation and
assessment of improvement plans. The organization can be established inside or outside the enterprise.
4.3 Processes for LMWL risk assessment including implementation of risk reduction
An LMWL-reduction plan should not be limited to a few specific factors causing loads. It should be based on
LMWL risk analysis in the workplace. On the basis of comprehensive risk assessment using this multi-factorial
analysis, specific action targets should be set to eliminate or reduce unacceptable risks. Basic processes in
achieving this target are given in 4.3.1 to 4.3.4 (see ISO 12100-1 and ISO 14121).
4.3.1 Risk analysis
To study the necessary activities to reduce the risks of increasing LMWL, risk assessment should be
implemented on the basis of risk analysis. Risk analysis should be performed based on the results of
specification of work situation, hazard identification and risk estimation.
Risk analysis should be completed by identifying priority risks that should be addressed immediately, so as to
reduce risks or reinforce the on-going measures.
184.108.40.206 Specification of work situation
To study the characteristics of the work situation at the workplace, the following items should be specified.
a) Production process, contents of work and tasks to be performed at the workplace.
b) Statistics on occupational accidents, incidence of work-related diseases and other diseases, sick leave,
c) Work organization and shift systems.
d) Work hours per day, week, month or year.
e) Operating time per day, continuous operating time and a rest system.
f) Characteristics of the workers, such as body size, muscle strength, history of injuries and diseases
affecting work, work experience, vocational education and training, and age.
220.127.116.11 Hazard identification
The following factors are the main hazards for increasing LMWL (see Annex B).
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18.104.22.168.1 Work hours and density
a) Long work hours.
b) Frequent and long overtime work.
c) Long continuous operating time.
d) Insufficient days off.
e) Uneven work density in a day, week, month or year.
f) Uneven work density between the workers.
22.214.171.124.2 Type of work
a) Lifting and carrying heavy objects (see ISO 11228-1).
b) Work requiring great physical force.
c) Repetitive monotonous work.
d) Work requiring frequent finger, hand or arm motions.
e) Work using vibrating tools.
f) Work with a keyboard or other data entry devices.
g) Precision work/work requiring high mental loads.
126.96.36.199.3 Postures and motions
a) Awkward postures and motions (see ISO 11226).
b) Continuous and/or highly frequent change in angle of joint (see ISO 11226).
c) Long-duration constrained posture (see ISO 11226).
d) Long-duration and/or long-distance walking (horizontal as well as on an inclining surface).
e) Frequent stair climbing.
188.8.131.52.4 Characteristics of work space and objects handled
a) Inadequate work space forcing an awkward posture or limited movement.
b) Layout of the workstation forcing excessive movement or awkward postures.
c) Inadequate height and dimensions of the work surface.
d) Handling work objects above the shoulder or below the knee.
e) Work space forcing the worker to maintain the same working posture.
f) Work objects which are heavy and/or require strong force.
g) Work objects which are difficult to hold or slippery.
h) Cold work environment and/or objects handled.
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a) Slippery and/or uneven floor surface.
b) Noisy environment.
c) Whole body vibration.
184.108.40.206 Risk estimation
Risk estimation should take into account the severity of the harm and probability of its occurrence and the
number of workers who will be affected.
4.3.2 Specifying risk reduction measures followed by a small trial of the improvement
To study the importance of risk factors and evaluate possible preventive measures for risk reduction, the
following factors should be considered.
Results of the risk analysis.
Ease of implementation of the risk reduction plan.
Effect of the improvement after reducing the risk.
Number of workers who will benefit.
Cost-efficiency of the plan.
Use of an action-oriented checklist is recommended to perform risk analysis, and to get hints for improvement
(see Annex C). The recommended procedure for using the checklist is as follows.
a) Organize a group to implement a checklist practice. In the group, the owner or executive director with
management authority, managers and workers of concerned sections, occupational health and safety
personnel should be involved.
b) Define the workplace to be checked.
c) Fill out the checklist individually.
d) Organize small group discussions on the risk factors found at the workplace and the factors with priority
e) Make an action plan to reduce risks for LMWL at the workplace.
f) Carry out a small trial to ensure the effect of the improvement before implementing the improvement on a
4.3.3 Implementation of risk reduction measures and monitoring of the effect of the activity
To check the effectiveness or insufficiency of the risk reduction measures, scheduled monitoring of the LMWL
level and health problems of the concerned workers should be provided. It is recommended to check the
subjective estimation of LMWL levels before and after the implementation, and subjective estimation of the
effectiveness of the improvement after the implementation (see Annex D). Statistics of sick leave relating to
LMWL and incidence of musculoskeletal diseases are also useful, to evaluate the effectiveness or
insufficiency of the risk reduction measures.
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4.3.4 Risk evaluation and drafting of new risk reduction plans
To check the effectiveness of risk reduction measures and to find any new or remaining problems, periodic
evaluations should be carr