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									                               MANUAL HANDLING:
   Association
paritaire du textile           Not Only a Matter of Weight
Volume 20, no 4 • April 2004

Stéphane Patenaude MSc
Ergonomist - ACE Member        Introduction                                                               Ergonomic standards

                               People responsible for health and safety in the                            Ergonomic standards are applied to varying degrees.
Introduction                   workplace are often in the dark as to the proper way                       Following is a list of the standards most widely used
                               to evaluate handling tasks. They ask themselves                            by ergonomists.
Ergonomic standards            questions such as: What is the maximum load that                           ➤ ISO Standard 11228-1
                               can be lifted without injury? Are there standards                          ➤ MMH
Factors for                    applicable to hazardous loads?                                             ➤ National Institute for Occupational Safety and
ergonomic                                                                                                    Health (NIOSH) equation
evaluation of manual           Standards have been set to “quantify” physiological
handling tasks                 limits but other aspects remain unclear like the exact                     These standards establish maximum loads for
                               link between bad posture and injuries. The                                 manual handling tasks performed under optimal
A practical example            established standards, however, are useful used to                         conditions (see Figure 1). In other words, the
                               evaluate the risks associated with specific work                           standards determine the maximum weight that can
Possible solutions             stations or tasks. If work requirements fall below the                     be safely lifted by workers. The values need to be
                               set limits, the risk level is fairly low; conversely, the                  adjusted according to five main factors affecting
Conclusion                     risk of injuries increases as the limits are exceeded.                     workers’ health and safety:
                                                                                                          ➤ lifting duration (work-time / recovery-time)
Bibliography                                                                                              ➤ lifting frequency
                                                                                                          ➤ properties of load
                                                                                                          ➤ working environment
                                                                                                          ➤ posture of worker




                               Figure 1:         Maximum load weight under optimal conditions
                                     Standard*                    Maximum                            Comments
                                                                  load weight (kg)

                                     ISO 11228-1                               25                    Load can be handled by 95 % of men and 70 % of women.


                                     MMH                                       27                    Load can be handled by 90 % of men.
                                                                                                     Maximum load for women is 20 kg.

                                     NIOSH                                     23                    Load can be handled by 90 % of the population
                                                                                                     (men and women).

                               * International Standard Organization (ISO), May 2003. Ergonomics – Manual handling. Part 1: Lifting and carrying. ISO 11228-1.

                                Mital, A., Nicholson, A.S., and Ayoub, M.M. A guide to manual materials handling (MMH). Second Edition. Taylor & Francis. 1997.

                                Water, T.R., Putz-Anderson, V., Garg, A., and Fine, L.J. Revised NIOSH equation for the design and evaluation of manual lifting tasks.
                                Ergonomics, 1993, 36 (7), 749-776
                                                                                                                                                                         1
MANUAL HANDLING
Factors for ergonomic                               Properties of the load                               compress, increasing the risk of lower back
evaluation of manual                                Third, the specific properties of the load           injuries (Chaffin, 1999).
handling tasks                                      should be taken into consideration because
                                                    they affect the way the charge is handled. The       A practical example
Lifting duration                                    weight of the load is one example. Another is
In the assessment of a work                         the location of the load: picking up loads from      Here is an illustration of a manual handling
station involving manual                            an elevated area is more likely to cause             task performed typical of the textile industry,
handling, it is crucial to                          fatigue (Genaidy, 1989, et Water, 1993). In          where a worker is lifting and stacking cones
take into account the                               addition, heavier loads increase the risk of         on a rack. Depending on the specific type of
period of time taken by                             musculoskeletal injuries (Water, 1993, et            rack, the worker lifts cones to heights varying
workers to complete                                 Hidalgo, 1997). The grip on the load is              between 25cm and 200cm from the floor.
the task. The longer this                           another important feature of the load. The           Performing this task forces the worker to
time is, the higher the degree of fatigue           grip is a function of the shape, texture (friction   adopt extreme postures (see pictures 1 and
(Asfour and Tritar, 1991). Factors such as the      rate) and balance of the load. Workers have to       2). The handling frequency is 120 cones per
frequency and duration of recovery-time also        exert greater force to handle loads with a poor      hour for an eight-hour work shift (2 cones per
affect fatigue levels and can reduce the impact     grip in a safe way. For example, handles             minute). Including recovery-time, this means
of other factors such as the total duration of      make boxes much easier to handle                     that the task is performed over a seven-hour
work and the lifting frequency per minute.          (Stälhammar, 1989).                                  period. Cones weigh 14kg each.
Periods of recovery-time allow workers to
compensate for the fatigue caused by                Working environment
repetitive handling tasks, and make it easier                       The forth factor relates to the
                                                                                                         Picture 1
for workers to sustain their work load.                             working environment. This
                                                                    includes the layout of work
Lifting frequency                                                   areas (height of surface where
The second factor is the frequency of handling                      load is picked up and
tasks, measured in number of lifts per minute.                      deposited), distances covered
This element is factored into the evaluation of                     with and without load, features
the consequences of load weight and lifting                         of circulation areas (stairs,
duration on worker fatigue. The load itself is                      graded surface, elevators, etc.)
not the only consideration and the number of        t e m p e rature and humidity rate. These
manual handling operations performed                variables directly affect the level of difficulty
within a set period of time should also be          associated with manual handling tasks
taken into account (lifting frequency). The         (Waters, 1993, et Hidalgo, 1997).
                                                                                                         Picture 2
combined effects of load weight and lifting
frequency directly affect worker fatigue            Worker posture
(Genaidy, 1989, Asfour, 1991 and                    The fifth and final element is the posture
Stälhammar, 1996). In addition, increases in        adopted by workers to carry out handling
lifting frequency diminish the worker’s             operations. The physical strength required to
capacity to assess loads (Karkowski, 1992).         perform the task
Workers who are unable to estimate loads            increases along with
correctly will not apply appropriate muscular       the distance between
effort and will tire more easily than if they had   the center of gravity
evaluated the load correctly (Pa t e n a u d e ,    of the load and that of
1997).                                              the worker. Excessive
                                                    distances also ca u s e
                                                    intervertebral disks to

2
The ergonomic evaluation of the task reveals      Possible solutions                               Conclusion
that this is a hazardous operation: according
to the five factors affecting worker health and   Once the evaluation has been completed,          When evaluating manual handling tasks, it is
safety, the maximum weight should be 12kg.        corrective measures should be taken. Here        important to take into consideration a full
                                                  are some suggestions.                            range of factors. Fo l l owing the initial
                                                                                                   assessment, use applicable standards to
                                                  Improvements to tools and                        determine potential hazards. Recommen-
                  27 kg                           working environment                              dations are then issued to reduce the risk
  Maximum weight load set by the MMH              ➤ Use a platform to install the cones, tie       factors. The impact of recommendations can
           under optimal conditions                 wires to the higher sections of the rack.      be determined by using the set standards. If
                                                  ➤ Modify the rack to reduce the surface of       the assessment reveals that standards are
                                                    the work area, by eliminating the lower        being respected, apply the recommendations.
                                                    and higher shelves of the rack.                Préventex can assist with the evaluation of
                                                                                                   handling tasks, for instance by sending a
                                                  Improvements to the                              specialist to analyze the situation and suggest
 Actual situation                                 organization of work                             appropriate solutions. Recommendations aim
                                                  ➤ Use lighter cones or lower lifting             to lower the constraints noted and can help
 • Lifting duration: 8 hours of work
                                                    frequency.                                     develop tailored solutions. Workers and
  (including 1 hour of recovery-time)
                                                  ➤ Reduce the duration of the stacking            production managers are consulted prior to
 • Lifting frequency: 120 cones per hour
                                                    operation to lower the lifting frequency. If   the implementation of any suggestions. They
 • Properties of the load: weight 14 kg,            the total amount of handling time is           may also wish to develop their own set of
  shape, size, quality of grip                      reduced, the worker will be able to handle     corrective measures; these should be
 • Working environment: height of pick up           heavier loads.                                 validated by a specialist in ergonomics to
  and deposit, location of cart                   ➤ Eliminate unnecessary handling o p e ra-       ensure they are appropriate.
                                                    tions: transferring cones to the cart
 • Posture of worker: trunk bent, shoulders
                                                    increases the lifting frequency so the
  bent over 900
                                                    original packaging should be used as often
                                                    as possible.

                                                  Improvements to work
                                                  methods
                                                  ➤ Eliminate the need to use the pliers
                  12 kg                             method for handling cones, because this
  Maximum weight load set by MMH
                                                    technique requires greater muscular
      considering actual conditions
                                                    strength. If the cones are handled
                                                    properly, workers will be able to handle
                                                    heavier loads in a safe way.
                                                  ➤ Provide training on proper work
                                                    methods. Posture is directly related to
                                                    lower back injuries and workers should
                                                    be given information on appropriate
                                                    body positions.




                                                                                                                                                3
MANUAL HANDLING
                                                             Association
                                                          paritaire du textile
Bibliography
                                                 The Préventex newsletter is published by
                                                 Préventex – Association paritaire du textile
Asfour, S.S., and Tritar, M. Endurance time
                                                 2035, Victoria avenue, suite 203
and physiological responses to prolonged         Saint-Lambert QC J4S 1H1
arm lifting. Ergonomics, 1991, 34 (3),           Telephone: (450) 671-6925
                                                 Fax: (450) 671-9267
335-342.                                         e-mail: info@preventex.qc.ca

                                                 General manager and
Chaffin, D.B., and Andersson, B.J.
                                                 newsletter editor: Michel Rouleau
Occupational biomechanics, 3rd ed. John
Wiley & Sons, inc. New York. 1999. 579 pp.       Co-chairman (Employers):
                                                 Donald Bélisle
                                                 PGI / Difco tissus de performance
Genaidy, A.M., and Asfour, S.S. Effects of
                                                 Co-chairman (Unions):
frequency and load of lift on endurance time.
                                                 Pierre-Jean Olivier
Ergonomics, 1989, 32 (1), 51-57.                 TUAC/COUTA

                                                 Coordination: Lise Laplante
Hidalgo, J., Genaidy, A., Karwowski, W.,
Christensen, D., Huston, R., and Stambourgh,     Copy editor:
                                                 Pierre Bouchard
J. A comprehensive lifting model : beyond
                                                 INDICO Communication
the NIOSH lifting equation. Ergonomics,
1997, 40 (9), 916-927.                           Translation: Paule Champoux-Blair

                                                 Graphic design: Passerelle bleue
Karwowski, W., Shumate, C., Yates, J.W.,
                                                 Printing: Imprimerie For inc.
and Pongpatana, N. Discriminability of load
heaviness : implication for psychophysical       Préventex, its managers and personnel, as
approach to manual lifting. Ergonomics,          well as authors of articles published in the
                                                 Préventex newsletter make no guarantee
1992, 35 (7-8), 729-744.                         as to the accuracy of the information
                                                 contained therein nor as to the pertinent
                                                 efficiency that may be inferred from this
Patenaude S., Marchand D., and Bélanger M.
                                                 information, and therefore accept no
Influence of load incertainty on physiological   responsibility. The information contained
demand. Short communication International        in the newsletter should not be considered
                                                 professional advice. Mention of products
Society of Electrophysiology and Kinesiology     or services by advertisers or in articles
- ISEK XII, 1998. 92-93.                         does not constitute an endorsement or
                                                 recommendation of same.

Stälhammar, H.R., Louhevaara, V., and Troup,     The Préventex newsletter is distributed free
J.D.G. Rating acceptable loads in manual         of charge to members of the textile and
                                                 knitting industries in the Province of
sorting of postural parcels. Ergonomics,         Québec. Its contents may be duplicate
1996, 39 (10), 1214-1220.                        provided prior authorisation is obtained
                                                 from Préventex and the source is
                                                 mentioned.
Stälhammar, H.R., Troup, J.D.G., and
Leskinen, T.P.J. Rating acceptable loads;        Legal deposit:
                                                 September 1st, 1994
lifting with and without handles. Int. J. Ind.   ISSN 0825-4230
Ergo., 1989, 3, 229-234.                         Printing: 2500 copies




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