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With the increase of the cadences, the optimization of the processes and above all the more important consideration of the men in the enterprises, ergonomics is today a high-stakes activity.

Introduction

The concept of ergonomics has long been interested in researchers. Among them are Sébastien le preste Vauban (1633-1707), who had given indications of the maximum tolerable loads for the navvies or Charles Augustin de Coulomb (1736-1806), who had carried out studies on the quantity of work Every day without fatigue. Long before him, one finds Plautus, an Italian intellectual, who in the 2nd century JC, had identified postural deformations in the stone tailors.

The creation of the term ergonomics will be the work of a polish engineer and naturalist Wojciech Jastrzebowski (1799-1882). In a booklet under the naturphilosophie published in 1857, it defined ergonomics:

By this term ergonomics, derived from the Greek ergon (work) and nomos (principle or law) we refer to the “Science of Work”, which is the use of the forces and faculties of which man was endowed by his creator. The science of Labour, understood in the broadest sense of the term “work”, can be divided into two main disciplines: The science of useful work, work that improves or is commendable, by which we hear the use of the forces and faculties of which Man has been endowed by his creator or their use for the common good, and the science of evil work, deteriorating work or undignified work by which we hear the contrary use (or intention of contrary use) of the so-called forces and faculties.

It will be from 1949 via in particular the Ergonomics Research society that real research has been carried out on this field.

The notion of ergonomics is now the subject of many standards. ISO 9001 proposes it under the term ” working environment “: “the working environment refers to the conditions under which the work performed, including physical, environmental and other factors ( such as noise, temperature, humidity, lighting or climatic conditions)“. It is also specified in directive 2006/42/EC:

Minimisation of the operator’s discomfort, fatigue and physical and psychological constraints under the intended conditions of use following the following ergonomic principles:

  • Take into account the variability of the operator (morphological data, strength and resistance).
  • Provide enough space for the movements of the different parts of the operator’s body.
  • Avoid the pace of work determined by the machine.
  • avoid monitoring that requires prolonged concentration, adapt the man-machine interface to the foreseeable characteristics of the operators .

The aim of ergonomics is to adapt work and machinery to man and not to the contrary.

In view of this issue, ergonomics extends to 3 domains:

  • Technical: Reduce and prevent the harmful effects of working conditions on the body
  • Medical: Reduction of health problems and accidents.
  • Psychological: reduction of stress, absences…

Health at work in numbers

Accidents at work

 

By definition, work-related accidents take into account all claims which have resulted in the payment of a first settlement to the employer account (daily allowance, capital annuity or death capital).

The different causes of accidents at works. It is noted that 3 classes represent 70%1 of the accidents at works.

Manual Handling

Manual handling represents all movements related to load movements from one location to another.

Advice:

  • Avoid having to carry out handling: Use aid equipment and gravity (roller rails, sloping racks…).
  • Both feet always on the ground and in support of a stable and flat area. Having your feet at 30 ° and slightly shifted is the best position to ensure stability.
  • The legs are bent at a minimum of 90 °, without being completely bent.
  • The back must always be straight.
  • The starting direction is known and allows you to position yourself correctly before lifting the load.
  • The center of gravity must be aligned with that of the load.
  • Never try to carry or handle loads that exceed your abilities.
  • The number of bending or rotating movements of the trunk required to carry out a handling must be minimised.
  • Avoid carrying loads at a height lower than the knee or above the shoulders.
  • Avoid blows and sudden movements, especially when you force or carry loads, or when bending or rotating the trunk.
  • Use upper body (trunk, pectoral muscles) to stabilize a load, and lower body (leg muscles) to obtain strength or movement.
  • Avoid clutter or confined workspace to have the volume needed to carry out a handling job.
  • Connect the maximum body surface when you need to carry a load.

Plain foot accident

The accidents on the ground floor represent the falls, slips… of our height due to a loss of balance. There are many causes:

  • Material for 20% of cases: defective material, congested or slippery surfaces,…
  • Human rights for 80% of cases: physical or mental inadequacy, inability to react,…

Advice:

  • Have a clean, uncluttered floor.
  • Be careful where we walk.
  • Attention to the loss of sensitivity of the proprioceptors after a prolonged position (e.g. seated), risk of falling. It is necessary to double the vigilance for the first 2 minutes, the time to regain this sensitivity.
  • Do not do two things at once: a person who is distracted is a person who is exposed to a risk. And moving, like assembling or screwing, is a full-fledged work activity.

Falls in height

Falls in height are defined by falling higher than our own height. In proportion to the level of accident and handling, falls in height are more serious and result in significant injuries. On their own, and even though the falls in height represent 5 times less than the accidents on the floor and the manipulations, they represent twice as many deaths, just behind the accidents by vehicle.

Advice:

  • Always have 3 points of contact.
  • Have a suitable tool, ladder, stepladder,… instead of a chair, table…
  • Respect the rules of the art for the use of ladders: the base must be equal to ¼ of the height and attach it during the work very high.

Occupational diseases

Unfortunately, occupational diseases are constantly increasing despite the important work done by companies to reduce them. We will not talk about all diseases but mainly MSD which account for more than 80% of occupational diseases.

By definition, MSD, musculoskeletal disorder, are a set of symptoms such as discomfort, weakness, inability or persistent pain in joints, muscles, tendons or other soft tissues, with or without Physical Events2. They share the following characteristics3 :

  • They are not the result of sudden or spontaneous lesions.
  • They result from the application of sustained or repeated mechanical stresses over long periods of time.
  • They can also result from mechanical stresses at the level of previously injured or already ill structures.

In other words, MSD are due to an imbalance between the functional capacities of individuals and the requirements of work situations4.6. They translate into pain, difficulties see the inability to perform tasks of everyday life.

According to international standards, a posture is maintaining a position more than 4 seconds.

The tools of Ergonomics

The tools for evaluating postures can be classified according to the body parts and the type of posture they allow to evaluate and according to their use: Quantification or prevention. 7, 8

 FrequencyForce (squeeze, push, lift ...)Posture
Upper body (back, arms, neck ...)
Lower body (leg, ankle ...)
MSD risk assessmentXXXXX
Washington ergonomicsXXXXX
TLVXX
OSHAXXX
OregeXXX
Mital tableXXXXX
NIOSH equationXXXX
Australian CodeXXXXX
SirtesXXXXX
MACXX
ARTXXXX
Snook tableXXXXX
Job strain indexXXXX
LUBAXX
RULAXXXX
OCRAXXXX
CTD RiskXXX
REBAXXXXX
QECXXXXX
ManTRAXXXXX
OWASXXXXX

It is good to recall, that in terms of ergonomics, rely only on a quantitative tool that gives a score allowing us to justify a decision is a little reducing. These tools are based on averages but in some cases can only apply to some people. The need for an assessment via medical personnel may be necessary.

In addition to the tools, ergonomics is a matter of culture, what the Japanese call the Kiken Yochi training (KYT). The KYT allows to increase the skills of the staff to identify the sources of risks. It is based on a mapping of the workspace, working conditions and incidents to exchange in groups and identify the risk factors.

Ergonomics and Lean

Beyond the need to eliminate Muda to gain in productivity, their eradications enable them to participate in the reduction of diseases and accidents at work.

However, in most cases, these Muda generate in proportion to ergonomic problems:

  • Additional efforts
  • Poor working conditions
  • of stress
  • of fatigue
  • of the nervousness
  • Extra, sometimes difficult movements

But, attention is paid to the fact that removing all Muda is not always good with regard to health.

an unnecessary shift towards productivity is not necessarily a Muda, but can be a movement allowing the regulation of muscular tension… 9, 10

Simple advice to limit ergonomic problems: Warm up11

Whatever the quality of the Positiondesign, it is necessary to warm up. Warming up is preserving its health capital of Tomorrow:

  • He prepares for the effort.
  • It maintains the flexibility of the joints.
  • It promotes blood circulation.
  • It helps in the prevention of joint accidents.
  • It improves mental readiness to a Position.

 

Below are some exercises that can be done in less than 10 minutes.

Source

1- http://www.inrs.fr/

2 – K. Kroemer (1989) – Cumulative Trauma disorders: Their recognition and ergonomics measures to avoid them

3 – M. A. Ayoub, N. E. Wittels (1989) – Cumulative Trauma Disorders

4 – L. Chew, J. C. Chijioke (1994) – Soft tissue biomechanics; Biomechanical models for stress analysis at the Position in the context of MSD

5 – NIOSH (1997)-Musculoskeletal disorders and Workplace factors: A Critical Review of epidemiologic evidence for work-related Musculoskeletal disorders of the neck, upper extremity, and low back.

6 – P. Crossed (1997) – Acting on occupational diseases – the example of MSD

7 – T. Ellis (2010) – Ergonomics: assessments and evaluations for jobs improvements

8 – J. Machaire (2001) – Evaluation and prevention of lumbar risks: Classification of methods

9 – T. Bertrand, A. Stimec (2010) – Management of contradictions and occupational health: Exploration in the countries of Lean management

10 – F. Bourgeois (2012) – what does the ergonomics that Lean does not know/do not want to see

11-J. M. Sanchez (2001)-Ergonomics of workstations

J. Machaire, N. Indesteege (1997) – Musculoskeletal disorders, risk analysis

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