WHAT RISK FACTORS CONTRIBUTE TO MSDs ( musculoskeletal disorders)?

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.