Musculoskeletal Disorders
(Taken
from Construction Safety Association of Ontario Magazine, Autumn 2000)
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Peter Vi
Construction Safety Association of Ontario
What
are the causes and controls in construction?
WHAT ARE MUSCULOSKELETAL
DISORDERS?
Musculoskeletal disorders
(MSDs) are injuries of the muscles, nerves, tendons, ligaments, joints,
cartilage, or spinal discs. MSDs are not typically the result of any instantaneous
or acute event (such as a slip, trip, or fall) but reflect a more gradual
or chronic development.
Other expressions
used to describe MSDs include
- Repetitive Strain
Injuries (RSIs)
- Cumulative Trauma
Disorders
- Overuse Injuries
- Repetitive Motion
Disorders.
Medical terms used
to describe MSDs to various parts of the body include low back pain, tendentious,
bursitis, carpal tunnel syndrome, epicondylitis, trigger finger, thoracic
outlet syndrome, carpet layers' knee, and degenerative disc disease.
WHY ARE MSDs A
PROBLEM?
- MSDs may cause
a great deal of pain and suffering among afflicted workers.
- MSDs are among
the most common lost-time injuries. Over a five-year period, MSDs average
approximately 45% of the total annual lost-time injuries in Ontario
construction (see Figure 1).
- MSDs are among
the most costly occupational problems. As shown in Figure 2, MSDs accounted
over 41% of Workplace Safety and Insurance Board (WSIB) costs.
- Job activities
that may cause MSDs span diverse workplaces and operations.
- MSDs may decrease
productivity and the quality of products and services. Workers experiencing
aches and pains on the job may not be able to do quality work.
Figure 1: Percent of total lost-time injuries
by type of occupational injuries and illnesses. Percent of total lost-time
injuries is averaged across five years (1994-1998). Data obtained
from the Workplace Safety and Insurance Board on June 30, 1999.
Figure 2: Percent of total WSIB costs by type of occupational injuries
and illnesses. Total cost includes compensation and medical costs.
Percent of costs is averaged across five years (1994-1998). Data obtained
from the Workplace Safety and Insurance Board on June 30, 1999.
The following are
recognized as important risk factors, especially when they occur at high
levels and in combination.
1) Forceful
exertion - Force is the amount of effort required to perform a
task or job. The amount of force one can exert depends on one's posture
and the number of exertions performed. The more force that is exerted,
the greater the stress on the body. Lifting, pushing, pulling, and gripping
a tool are examples of activities that require exerting force or muscle
effort.
2) Repetitive
movements - Movements performed over and over are described as
repetitive movements. But a repetitive movement can also be an awkward
posture held for long periods of time. These movements can be of risk
to the worker because of continual stress placed on one body part without
sufficient muscle recovery time. Nailing a deck, screwing drywall, and
tying rebar are examples of repetitive tasks.
3) Awkward
postures - Postures are the positions of body parts. Unnatural
positions or awkward postures are those in which joints are held or moved
away from the body's natural position. The closer the joint is to its
end of range of motion (for instance, bending the back forward as far
as possible), the greater the stress placed on the soft tissues of that
joint, such as muscles, nerves, and tendons.
4) Secondary
risk factors
- Contact pressure
is any external pressure that is applied to soft tissues and puts stress
on those tissues. Holding tools where handles press into parts of the
hand or arm is an example of contact pressure.
- Vibration is a
secondary risk factor which can cause damage to nerves and blood tissues
as well as other soft tissues.
- Gloves can be
a risk factor for musculoskeletal disorders if they do not fit properly
or if they restrict movement of the fingers and hands.
- Temperature can
also affect muscles. Cold temperatures increase the stress placed on
soft tissues by reducing their range of motion and flexibility. Heat
affects the work rest cycles required due to the increase in fatigue
and the need for muscle recovery.
5) Combination
effect Chance of injury increases when two or more MSD risk
factors combine in one job. One factor alone is unlikely to cause a high
risk of injury. For example, performing a forceful lift once places a
worker at less risk than performing a forceful lift several times an hour.
Two approaches are
widely accepted for controlling workplace ergonomic hazards.
Engineering
Controls These are measures taken to modify the forcefulness,
repetitiveness, awkwardness, vibration levels, physical pressures, or
environmental extremes connected with a particular job. Engineering controls
are the preferred approach in preventing MSDs. Examples include modifications
of 1) the workstation layout, 2) selection and use of tools, 3) work materials,
and 4) work methods.
Administrative
Controls - Administrative controls are management-directed work
practices and policies. Administrative control strategies include 1) changes
in job rules and procedures such as scheduling more rest breaks, 2) rotating
workers through jobs that are physically tiring, and 3) training workers
to recognize ergonomic risk factors and to learn techniques for reducing
stress and strain while performing their job.
Although engineering
controls are preferred, administrative controls can be helpful as temporary
measures until engineering controls can be implemented or when engineering
controls are not technically feasible. Since administrative controls do
not eliminate hazards, the necessary precautions and safeguards must be
followed.
Interventions to
control MSDs can range from the simple to the elaborate. Modifications
to existing design can be costly, but in many circumstances the interventions
can save time and money.
The following are
examples of engineering and administrative controls aimed at reducing
MSDs in construction.
Manual handling
of tools and material
- Plan ahead to
minimize material handling.
- Improve housekeeping
to prevent trips and falls.
- Where available,
order ready-mixed mortar to decrease repetitive shoveling and exposure
to cement powder.
- Use carts, dollies,
hoists, or other mechanical handling devices.
- Increase use of
ladder hoists, gin poles, daisy chains, or cranes to move materials
on or off roofs.
- Use chain falls,
motorized buggies, carrying handles, or extension handles for carrying
large or awkward materials like drywall.
- Break loads into
smaller units. For instance, put cement in bags weighing less than 50
lb.
- Use shoulder pads
when carrying loads on shoulders.
- Employ administrative
controls such as ergonomics training, pre-job exercises, weight labeling
of materials, and encouraging two-person lifts with heavy objects.
A wall jack can help reduce the risk of MSDs for small crews
Weight of materials
and equipment
- Where possible,
use materials or equipment lighter than traditional types--for example,
lighter-weight concrete blocks and fiberglass ladders.
- Order or provide
material such as sand and cement in bags lighter than 50 lb.
Hand tools
- Use handles that
are comfortable and afford a good grip, such as rubber or spongy-type
grips.
- Make sure grips
are the right size for the hands and designed for use by either hand.
- Use hand tools
designed with a power grip for heavy work and a pinch grip for fine
work.
- Select hand tools
designed to suit a neutral wrist posture and reduce the amount of force
applied.
- Use tools that
have torque reduction, low kickback, or lighter weight when appropriate.
- Ensure adequate
power supply and proper maintenance of power tools.
Making the job a little easier: grip handle and head support
Vibration
- Use vibration-absorbing
padding on grips or handles. Anti-vibration gloves or vibration-dampened
handles are recommended on pavement breakers, tampers, torque wrenches,
needle guns, and pad sanders.
- Provide regular
maintenance and sharpening of tools.
- Use vibration-dampened
seating, devices to dampen engine or motor vibration, and vibration-dampening
flooring.
- Ensure proper
tuning and balancing of engines and motors.
- Use cutting or
powerhead vibration dampening devices.
- Isolate chassis.
- Purchase or rent
equipment that includes vibration-dampening rubber grommets on controls
and control box.
Overhead work
- Use drywall lifts,
materials lifts, duct jacks, scissor lifts, and extension poles or stands
for operating tools overhead.
- Reduce risks from
awkward work postures by using adjustable scaffolds, aerial and other
work platforms.
Work at ground
or floor level
- Use tables, benches,
or stands to bring work to waist height.
- Store materials
at waist height.
- Introduce adjustable
height scaffolds for bricklaying.
- Use pipe stands
on pipe and steam fitting jobs, D-handles or longer handles for shoveling,
rebar-tying devices, standup fastening systems for roof insulation,
rug rippers, carpet stretchers, and pipe/conduit benders.
Awkward postures
- Rent or buy equipment
that provides the best visibility so that operators don't have to lean
forward, twist, turn, or assume other awkward positions in order to
see.
- Obtain equipment
with better cab design, adjustable seats, and ergonomically designed
levers, pedals, and foot rests.
- Select equipment
with wraparound windshields, multiple mirrors, and tinted windows.
Other controls
- Repetitive
work: Use power tools, rest breaks, job rotation, and rebar-tying
devices.
- Kneeling:
Use kneepads, pants with kneepad pockets, and micro rest and stretch
breaks.
- Standing on
concrete: Use shoe inserts, sit/stand stools, bucket seats (convert
a 5 gal bucket into a seat), floor mats, and rest breaks.
In Ontario construction,
MSDs represent a large and expensive problem--45% of all lost-time injury
claims and 42% of total claim costs. The major risk factors for MSDs are
heavy manual material handling, repetitive tasks, and awkward work postures.
As these factors increase in frequency and duration, a worker's risk of
incurring an MSD rises.
Province-wide, the
construction industry faces an aging workforce and a shortage of trained
workers. These conditions--combined with a high rate of musculoskeletal
disorders, steep WSIB costs, and the medical burden to workers--can reduce
production volume and quality.
With its industry
partners--labour, management, government, manufacturers and suppliers--CSAO
is working to reduce the risk of MSDs in Ontario construction.
This paper appears in the eLCOSH website with the permission of the author
and/or copyright holder and may not be reproduced without their consent.
eLCOSH is an information clearinghouse. eLCOSH and its sponsors are not
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