Occupation factors as contributors for upper extremity damage

Work-related musculoskeletal disorders of the  upper extremities are a leading  cause  of lost work days and a significant  economic  burden to  industry and  patient and  their families. The studies show  there are few occupational  factors as contributors  to developing  an upper  extremity  cumulative trauma injury.
 
1. High task repetition and inappropriate work/rest cycles. A job is classified as highly repetitive if the cycle time is less than 30 seconds, or if a task or motion is performed more than 50 percent of the time it takes to complete the work cycle. Work and rest cycles are the intervals of time measured during one complete task revolution.

2.Wrist/arm positions and awkward postures. Repetitive wrist flexion and extension increase carpal tunnel pressures in the wrists. In addition, awkward postures overload muscles and tendons and load joints in an asymmetrical manner, imposing a static load to the musculature and reducing nerve and muscle blood flow. Activities that use repetitive finger motions with the wrist in an exteneded position in constrained postures-such as playing a musical instrument, typing or using pinch grips-increase carpal tunnel pressures.

3.Mechanical stress concentrations/contact trauma. Direct pressure that contacts the base of the palm or the palmar surface of the fingers, such as frequent or continuous use of tools with hard, sharp edges or short handles, can cause direct compression against peripheral nerve fibers and lead to upper extremity symptoms.

4. Vibration forces on the wrists and hands. Vibrating hand-held tools can cause toxic vibration reflex and constrict blood vessels, which may damage nerve fibers.

5. Exposure to cold. Working in an cold environment and handling cold tools affects circulation to the upper extremities. Using gloves. Gloves reduce tactility and increase the amount of force that's required to hold or manipulate and object . This risk increases with poor fitting gloves and thickness.

6.Lead exposure. Constant contact or exposure to lead can impair maximal motor and sensory nerve conduction velocities of the medial nerve, which may cause carpal tunnel syndrome.
Work stress and job satisfaction. An employee's perception of the workload, work pressures and the response to early signs of fatigue and discomfort.

7. Work stress and  Job  satisfaction.
 
 8. Forces and  forceful  exertions:  static and dynamic  loading  increases muscle contraction  strength and duration, which  reduces  circulation to muscle fibers and increases recovery time requirement, static  loading  increases muscle fiber  recruitment, fatigue and  decreased  blood  perfusion.