Techniques of risk reduction
include: -
a)
Mechanical
assistance;
b)
Improvements
in the task;
c)
Reducing
the risk of injury from the load;
d)
Improvements
in the working environment; and
e)
Individual
selection.
Manual handling is one of the
most common cause of injury in the workplace, listed below are some important
tips on avoiding injury, remember “if in doubt, don’t lift”.
Heavy items, or even lighter
ones when held away from the body, may cause injury.
Such items should only be moved if it is necessary to do so. Large
boxes of material should be broken down and moved in sections.
Wherever practicable, the load should be lightened.
If objects require regular movement, consider obtaining and using a
mechanical aid such as a trolley. Use
the lift not the stairs; use a trolley not brute strength.
If something has to be moved and
there is potential for harm, make use of the correct techniques to minimise
the problem. Injuries may be
avoided by using the body carefully, taking care not to strain or cause undue
pressure upon the spine or the stomach.
No specific weights, which
people can safely lift, are laid down in general regulations, as much depends
on specific circumstances and the capability of the person.
Guidelines give an example of 25
kilograms maximum (reduced by one third for females).
9.5
Hazards arising from the use of Manual Handling Aids
The alternatives and aids to
manual handling include the use of a wide range of equipment including
trolleys and conveyors, and some of these bring with them their own intrinsic
risks. Staff can run trolleys
over their own or colleagues’ feet. Conveyors
carry goods that would otherwise require manual effort, but this can create
trapping hazards if poorly designed and in some cases the goods themselves in
movement may generate sufficient noise to cause damage to unprotected ears, as
in bottling plants.
It is a principle in health and
safety that when alternative methods are considered, in this case mechanical
aids to manual handling tasks, a risk assessment be carried out on the
proposed new methods rather than simple assuming that by tackling one problem
others may not arise.
9.6
Risk Reduction
|
Eliminate |
Wherever
practicable manual handling tasks should be eliminated, for example: use
the lift rather than carrying items up two flights of stairs. |
|
Tasks |
Improve the
tasks by applying the following principles: ·
improve workplace layout to
improve efficiency ·
reduce the amount of twisting
and stooping ·
avoid lifting from floor level
or above shoulder height ·
reduce carrying distances ·
avoid repetitive handling |
|
Load |
Reduce the
load and improve its handling characteristics by applying the following
principles: ·
make the load lighter or less
bulky ·
make the load easier to grip ·
make the load more stable ·
make the load less damaging to
hold |
|
Individual Capacity |
The
following should be borne in mind when carrying out an individual risk
assessment ·
strength, health and fitness
of individual ·
pregnancy ·
level of training and
information provided by employer |
|
Mechanical Aids |
All items
of equipment should be suitable and fit for the purpose |
9.6
Manual
Handling and Health
Manual Handling is defined, for
the purposes of the Manual Handling Operations Regulations 1992, as an
activity involving the movement or support of a load by hand or by bodily
force. The Regulations do not
cover bodily force exerted for any other purpose (e.g. pushing or pulling a
lever to control a machine).
The definition is arbitrary,
since hazards that accompany the application of a force will exist regardless
of the object, which is being controlled.
This is not a loophole, since legislation stemming from other EC
Directives will deal with handling issues related to design of machinery and
workplaces.
The definition of manual
handling is still very broad, and the range of injuries associated with it is
potentially wide. The risks to
health from manual handling fall within 3 main categories.
i)
Musculoskeletal
injuries (i.e. those concerning the muscular or skeletal system of the body).
ii)
Injuries
caused by the load falling onto or trapping part of the handler or someone
nearby.
iii)
Injuries
caused by the handler falling, perhaps against the load or other objects.
Musculoskeletal injuries may be
either:
a)
acute,
i.e. caused by an immediate failure of a bone, ligament or muscle, or
b)
chronic,
i.e. caused by repeated actions carried out over weeks, months, or even years.
In general, acute injuries are
associated with a few unusual exertions, such as lifting a heavy weight, while
chronic injuries are linked to repetitious actions of lower force. In an
individual case the distinction can be blurred.
Acute injuries may occur when an act triggers a failure in a part of
the body that has suffered repeated but unnoticed damage over a long period.
Similarly, when an individual is fatigued then the risk of acute injury
from relatively light forces increases. Sometimes the triggering act may seem
insignificant, such as picking up a pen or bending to pat a dog.
9.8
Back Structure and its Implications
The back has an elaborate
structure of bones, joints, ligaments and muscles and provides the support and
strength for human body functions. The
structural stability of the body depends in particular upon the spine
(comprising a number of bones, or vertebrae, one on top of another as
illustrated in Figure 1 – upper) and the supporting given from sets of
ligaments and muscles. Between
each pair of vertebrae there are separating discs of gel-filled fibrous
material that enable the spine to bend and serve to cushion the effect of
impacts. The vertebrae also
enclose the main nerve canal of the body, the spinal cord.
Figure
1 — Back structure and implications
9.9
Intervertebral Discs
Intervertebral discs are
essential for the proper operation of the back.
When forces are applied to the back, the flow of gel within the discs
ensures that the forces are distributed evenly onto the surfaces of the
vertebrae. The discs are designed
to react primarily to compression, the force acting down the spine caused by
the weight of the head and body.
The discs do not behave as if
they are completely elastic and their recovery from deformation is slow.
If compression is maintained for a period longer than 15 minutes then a
“creep” effect occurs and the disc will take longer to recover.
When forces are considerably
greater than normal, for example when carrying or holding a heavy load,
degenerative effects can also occur if there are repeated actions with
relatively light loads. Eventually,
a lifting action may force the centre of the disc out through the containing
fibres, putting pressure upon the nerves in the spinal column (see Figure 1
– lower). This is termed a prolapsed disc (often mistakenly called a
“slipped disc”) and is a painful and severe injury, with recovery taking
many months. A prolapsed disc
often requires surgery.
Actions, which lead to
relatively higher levels of damage to the disc, are twisting and stooping.
Twisting in particular causes stretching of the fibrous outer part of
the disc, while stooping actions, i.e. bending the body from the waist make
the pressure on the disc, as well as increasing considerably the total force
transmitted down the spine.
Prolapsed discs form
approximately 15% of back injuries and are less common than muscular or
ligament strains.
Summary
·
avoid
twisting
where possible
·
avoid
stooping
where possible
·
intersperse
manual handling tasks with other tasks if possible
·
allow
sufficient rest and recovery periods
9.10
Ligaments
The ligaments are bundles of
fibres, which hold the bones of the back together.
The fibres themselves are not usually elastic but are coiled up, and
the ligaments stretch by straightening out the fibres. If force is applied to ligaments when they are fully
stretched, then they may rupture. Continuous
stretching may lengthen the fibres and loosen the arrangement of the
vertebrae, making them prone to moving and trapping nerves.
Summary
·
avoid
overreaching where possible
·
minimise
frequency of stretching where possible
9.11
Muscles
Muscles play the dynamic role in
the support and movement of the back. Excessive
forces acting upon these muscles, for example when trying to stop a falling
load, can lead to tears in their fibres.
Unexpected forces can lead to injuries in unprepared muscles because
there is a lack of resistance or to extra strains on discs or ligaments.
The muscles of the stomach also
play an important role in lifting. Tensing
of the stomach muscles and holding the breath will increase the pressure
within the abdomen, enabling the force being transmitted through the spine to
be more evenly distributed. This
explains the common advice to take a deep breath and hold it before lifting.
Summary
·
minimise
throwing and catching actions
·
train
employees in safe lifting techniques
9.12
Fitness
The well-trained or fit
individual will have a broad margin of safety between his/her maximal power or
capacity on the one hand and what is being demanded of him/her physically on
the other. As work becomes
physically less demanding then some physical activity should be included to
provide the stimuli the body needs to function at best.
The less we do the less we are able to do and the vicious cycle
progresses in a downward spiral.
There are four elements of
fitness:
i)
Cardiovascular
or Oxygen Transporting System
If the job requires the heart to
pump, for example, 10 litres of blood per minute at a rate of 120 beats per
minute, it is a definite advantage if the heart is trained to pump 15 litres
of blood per minute at a rate of 150 beats per minute.
ii)
Strength
Muscles strength means that more
of our muscle fibres (each muscle has between 100,000 and 1,000,000 fibres)
are primed for work. It is achieved by high loading/low repetition exercises.
iii)
Muscle
Endurance
This also depends upon the
number of fibres primed to work but it is dependant upon the efficiency of the
chemical turnover produced by muscle contraction.
Muscle fibres work in a relay system, i.e. when the energy of some
fibres is spent others take over and so on repeating the cycle.
Endurance is achieved by low loading/high repetition exercise.
iv)
Flexibility
Flexibility would seem to be the
Cinderella of fitness. Little
attention is paid to it but it is of equal importance as each of the other
three elements. In the usual
physical training programme it is either forgotten altogether or such scant
attention is paid to it that the effects are, at best, negligible. Flexibility is of particular importance in achieving safe
manual handling skills.
9.13
The Load
The “load” is the object,
person or animal being handled, whether lifted, lowered, pushed, pulled or
carried. The features of the
load, which are relevant to the handler, are related to:
a)
the
force required to handled it
b)
its
size
c)
how
easy it is to grasp
d)
its
stability
e)
external
features that may create a hazard
9.13.1
Assessing the Load
9.13.2
Heaviness of the Load
As stated previously there is no
single safe weight for lifting or single safe force for pushing or pulling.
Safe weights depend very much on the other features of the operation,
such as the task, the environment and individual capability.
9.13.3
Shape and Size of the Load
The size and shape of the load
are factors, which influence risks to the back in manual handling.
The further the centre of gravity of the load from the body, the
greater the leverage effect on the spine, and the higher the risk of injury.
If a load has an even weight distribution, the centre of gravity is in
the centre of the load. The
centre of gravity of a large load is therefore always further away from the
body than the centre of gravity of a small load.
This is because the sheer physical bulk of a large load separates the
handler from the centre of gravity of the load.
Even if two loads weigh exactly the same, the larger load will cause
more strain due to the leverage effect.
9.13.4
Handling Points of the Load
Many loads are not particularly
easy to grasp. The load may be
large, slippery or have sharp edges. In
these cases extra grip strength is needed, which fatigues the muscles more
quickly. As handlers tire, their
grip will become weaker, and they may have to change either their grip or
their posture to maintain control of the load.
The risk of dropping the load altogether is thereby increased. Wherever possible a “power grip” should be applied to the
load. A “pinch grip” is less forceful and there is a greater risk of
fatigue. Figure 2 shows the
distinction between the two forms of grip.
9.13.5
Stability of the Load
If a load is unstable or its
contents are likely to shift during handling (e.g. containers of fluids), the
risk of injury increases since stresses on the spine are less predictable and
the handler may not be prepared.
9.13.6
External Features of the Load
Assessing hazards arising from
external features of a load is largely a matter of observation.
Factors to look out for are:
a)
sharp
or rough edges which may increase the difficulty of holding a load and cause
other hazards (splinters of wood, for example, create a risk of infection)
b)
hot
or cold objects
c)
chemical
hazards (these should be dealt with under the Control of Substances Hazardous
to Health Regulations 2002)
d)
slippery
loads, e.g. those which are wet, greasy or have a non-stick covering
e)
loads
with damaged containers.
In all of these cases,
protective gloves could be needed. Gloves,
however, may impair the grip and thereby increase the risk of dropping objects
onto the feet.
Figure 2 — Power Grip versus Pinch Grip
9.14
The Task
9.14.1
Distance of the Load from the Trunk
The distance of the load from
the trunk is a crucial feature of manual handling operations, which involve
lifting, lowering or carrying. The
further away a load is from the body, the greater the stress on the lower
back. The holder is also much
more likely to topple over when the load is held away from the body.
If the holder can press the load
into the body while lifting there is an additional frictional force, which
reduces the spinal load and the fatiguing effect of the load on the arm
muscles. As a rule of thumb, the
safe weight of a load that is held at arm’s length is approximately
one-fifth of what it would be if the load were held close to the body.
