MSD Risk Factors and Control Measures
Musculoskeletal disorders result from using a particular muscle or group of muscles over long periods without taking sufficient rest to allow the body to recover from the stress. There are four primary factors associated with the risk of developing MSDs.
Generally speaking, the development of MSDs requires the presence of more than one of these and the risk of injury increases with the number and severity of other risk factors.
Force
Force is the amount of effort required by the body to perform a task such as lifting, pushing, pulling, carrying, gripping etc… An injury can occur if the amount of force exceeds the body’s capabilities or when the force is used repeatedly without giving the muscles sufficient time to rest. As the amount of force required increases, so does the risk of injury.
Consider the following to minimize your risk and reduce the force(s) required to perform your daily activities:
- use mechanical aids where possible. Examples of mechanical aids include lifting devices, trolleys/carts, rolling totes
- keep equipment and tools well maintained
- use power tools instead of hand tools
- consider an alternate equipment type or design that reduces the force required
Repetition
Repeatedly performing tasks that use the same muscle groups or motion around a joint can lead to a musculoskeletal injury. This is motion is considered “repetitive” when the time to complete one cycle is less than a few minutes and performed continuously for at least 2 hours.
Consider the following to minimize your risk and reduce the repetitive nature of any tasks you perform in your daily activities:
- give your body time to recover by taking a 5-minute break from repetitive tasks every hour.
- avoid overloading single muscle groups by also using other muscle groups if possible. For example, you may be able to alternate the use of your hands.
- spread your tasks over longer periods.
Posture
Your body works at its maximum efficiency and experiences minimum stress when your body is in its natural alignment or in a “neutral” posture. Neutral posture means:
- neck and back are aligned and not twisted
- arms close to the sides of body
- wrists straight in line with forearms
- fingers naturally curled
Working in postures that take parts of your body out their neutral position are referred to as “awkward” postures. This increases the stress on the body and increases the risk of suffering a musculoskeletal injury. Awkward postures include:
- Bending wrists (up/down, sideways)
- Bending or twisting neck or back
- Extended reaches
- Above shoulder level
- Forward
- Backward
- Sideways
Consider the following to minimize your risk and avoid awkward postures from tasks you perform in your daily activities:
- Stored items:
- Store below shoulder level where possible. This is especially important for heavy items.
- Use a step ladder to bring yourself closer to items stored above should level.
- Overhead filing cabinets:
- Stand up to grab binders
- Store frequently used binders on your desktop
- Break down large binders into smaller, easier to handle binders.
- Arrange your desk top area so frequently used items can be accessed comfortably within arm’s reach.
- Turn your chair rather than twisting your back when reaching for items behind you or to your side.
- Consider a telephone headset if you use the phone frequently.
Static Postures
Static posture refers to postures that are held or maintained for an extended period to perform a particular task. Although there is little or no actual movement with static postures, the muscles become fatigued as a result of constantly contracting to hold the position. Examples of static postures include holding or gripping equipment, standing or sitting still in one place for extended periods, raising the shoulders for extended periods, tilting the head for extended periods.
Minimize the risk of fatigue or injury from static postures by:
- Job, equipment and machine design to minimize or eliminate the need to grasp and hold items for extended periods.
- Minimize static effort demands for tasks with unavoidable static effort requirements.
- Adjust working heights to keep back, arms and head in neutral posture while performing work.
Vibration
Direct contact with vibrating machines, tools and equipment can transfer the vibrations (energy) to the body through the hands, feet or seat. Repeated exposure to vibrations can affect blood vessels and nerves that can lead to musculoskeletal disorders affecting the hands, arms or the back depending on the source of the vibration. Vibration sources are characterized as:
- Hand-Arm
- Whole-Body
Hand-Arm Vibration
Hand-Arm vibration is vibration transmitted through the hands. Common sources of hand-arm vibration include electric razors, grinders, sanders, jackhammers and motorcycle handlebars.
Controls for hand-arm vibration include:
- Antivibration tools
- Antivibration gloves
- Keep hands and body warm
- Minimize vibration transfer to hands
- Avoid continuous vibration exposure. Take a 10 minute break from vibration every 1 hour of continuous exposure
Whole-Body Vibration
Whole-body vibration is vibration that is transmitted through the seat or feet. Common sources of whole-body vibration include riding motorized equipment such as tractors, construction equipment, buses and trains.
Controls for whole-body vibration include:
- Use “air-ride” suspended seats
- Ensure vehicle suspension systems are properly maintained and tires properly inflated
- Use adjustable seats with lumbar support
