Anthropometry – the study of human body measurement for use in classification and comparison.

Awkward Posture – occurs when a joint deviates from the neutral (natural) position, increasing the risk of injury. Specific movements are particularly suspect to awkward posture including:

• Flexion and extension of the wrist (bending up and down)
  
• Ulnar and radial deviation of the wrist (side to side movement)
  
• Abduction and flexion of the shoulder (upper arm positioned out to the sideor above shoulder level)
  
• Elevated upper extremity (hands at or above shoulder height)
  
• Flexion and extension or bending of the neck forward and back
  
• Side bending of the neck as when holding a telephone receiver on the shoulder

Biomechanical stressor – the physical aspects of workstation, tools and work processes that exert stress on the body.

Ergonomics Program – a systematic process for anticipating, identifying, analyzing and controlling hazards that can lead to work-related musculosketal disorders (WMSDs)

Force - The amount of muscular effort required to perform a task. Generally, the greater the force, the greater the degree of risk. High force has been associated with Work Related Musculoskeletal Disorders in the shoulder, neck, the low back, and the forearm, wrist and hand.

NIOSH - National Institute of Occupational Safety and Health. NIOSH is the institution that provides scientific data upon which OSHA makes recommendations.

OSHA - Occupational Safety and Health Administration. The mission of the Occupational Safety and Health Administration (OSHA) is to save lives, prevent injuries and protect the health of America's workers. To accomplish this, federal and state governments must work in partnership with the more than 100 million working men and women and their six and a half million employers who are covered by the Occupational Safety and Health Act of 1970.

Recovery Time - Recovery time is the length of rest between exertions. Short work pauses can reduce discomfort. Inadequate rest periods between exertions can decrease performance. As the duration of the uninterrupted work increases, so does the amount of recovery time needed.

Repetition - Repetition is the number of a similar exertions performed during a task. A warehouse worker may lift three boxes per minute from the floor to a countertop; an assembly worker may make 20 units per hour. Repetitive motion has been associated with injury and worker discomfort.

Risk Factor (stressor) – a characteristic of the work environment that research has shown to be associated with an elevated occurance or severity of WMSD’s. Risk factors can involve purely external exposures that act on the musculoskeletal system. They can also involve intrinsic response to a load or task, such as lifiting or rapid and awkward movement.

Static Postures – postures held over a period of time to resist the force of gravity or to stabilize a work piece. These postures are particularly stressful to the musculoskeletal system. Even if there is some movement, if the joint does not return to the neutral position and continued muscle force is required, the effect can be the same as a non-moving posture.

Physiology and Ergonomic-related Disorders or Injuries

Afferent nerves – sensory nerves supplying information, including movement, position, and other sensation, to the central nervous system.

Bursitis – inflammation of the bursae, which are fluid filled sacs located between skin and bones, or between bones and the muscles, tendons and ligaments. These fluid filled sacks cushon movement of one body part over another.

Carpal tunnel – a narrow anatomic canal or tunnel between the forearm and the wrist through which the median nerve and nine digital flexor tendons pass. It is formed by the wrist bones and a dense trans-carpal ligament.

Carpal Tunnel Syndrome (CTS) – occurs when the median nerve, which supplies most of the sensation of feeling to the thumb, index and middle fingers and half of the ring finger, gets constricted or “pinched” by inflamed muscles that surround the carpal tunnel. and becomes constricted. This pinching of the nerve causes numbness and tingling (feeling of "pins and needles”) in the area of the hand that the nerve goes to.

Cartilage – a thick, white connective tissue that attaches to the articular surfaces of bones, forming a low-friction cushion. It is structurally more rigid than tendon.

Cubital Tunnel Syndrome – occurs from a pinched nerve at the elbow commonly known as the "funny bone". This might be caused by trauma or repetitive use of the elbow and may be caused by continuous use of the elbow in a flexed position. This causes the nerve to become stretched and irritated as opposed to when the arm is extended and the nerve is in a relaxed position.

DeQuervain’s Disease – a special case of tenosynovitis that occurs in the abductor and extensor tendons of the thumb where they share a common sheath. This condition often results from combined forceful gripping and hand twisting. De Quervain's tenosynovitis typically causes pain when the thumb is folded across the palm, the fingers are wrapped over the thumb, and the wrist is forcibly bent towards the ulna.

Epicondylitis – elbow pain at the site where the proximal flexor or extensor tendons insert at the lateral or medial epicondyles (bony prominences on the inside and outside of the elbows).

Humerus – the long bone of the upper arm.

Mechanoreceptors – specialized nerve endings and sense organs that convey the senses of touch, spatiality, and pressure.

Median nerve – the nerve supplying most of the sense of sensation to the first through fourth fingers. The median nerve is the only nerve that passes through the carpal tunnel. It also controls the working of some of the thumb muscles that permit an individual to perform a pinch grip. There are other nerves that provide sensation to the rest of the hand and control other hand muscles, but they do not pass through the carpal tunnel and therefore are not involved in the carpal tunnel syndrome. The median nerve is the only nerve that passes through the carpal tunnel.

Musculoskeletal Disorders – injuries or illness of soft tissies of the upper extremity (fingers through upper arm), shoulders and neck, low back, and lower extremity (hips through toes) that is primarily caused or exacerbated by workplace risk factors, such as sustained or repeated exertions or awkward postures and manipulations. Included are disorders of the muscles, nerves, tendons, ligaments, joints, cartilage and spinal disks. Medical conditions generally develop gradually over a period of time, and do not typically result from a single instantaneous event. Examples include Carpal Tunnel Syndrome, DeQuervains’ disease, Muscle strains, Rotator Cuff Tendonitis, Synovitis, Tendonitis.

Symptoms can vary in their severity depending on the amount of exposure the individual has had. Often symptoms appear gradually as muscle fatigue or pain at work that disappears during rest. Usually symptoms become more severe as exposure continues (e.g., tingling continues when at rest, numbness or pain makes it difficult to perform the job, and finally pain is so severe that the individual is unable to perform physical work activities). Examples of symptoms include:

• Decreased range of motion
  
• Decreased grip strength
  
• Loss of function
  
• Deformity
  
• Swelling
  
• Cramping
  
• Numbness
  
• Burning
  
• Pain
  
• Tingling
  
• Aching
  
• Stiffness

Repetitive Strain Injury – injury caused by excessive wear and tear on tendons, muscles, and sensitive nerve tissues that occurs from continuous use over an extended period of time.

Synovitis – inflammation of the membranes covering tendon and joint ends.

Synovium – a lubricating tissue located at the sheaths of joints, in bursae and as the innermost layer of joint capsules. High-usage tendons, such as the finger flexor and extensor tendons, are also surrounded by lubricating synovial tissue.

Tendonitis – occurs when tendons become inflamed from repeated tensing. Eventually, the fibers of the tendon start separating, and can even break, leaving behind debris that induces more friction, more swelling, and more pain. Acute tendonitis is caused by overuse, whereas "sub-acute" tendonitis is more common, and characterized by a dull ache over the wrist and forearm that gets worse with repetitive activity.

Tenosynovitis – occurs when the tendon sheath thickens and becomes inflamed from repetitive activity that exceeds the sheath’s ability to lubricate the tendon. As a result, the area around the sheath becomes tender and painful.

Tension Neck Syndrome – a feeling of fatigue or stiffness in the neck, neck pain or headache radiating from the neck. Signs consist of at least two tender spots or palpable hardenings.

Thoracic Outlet Syndrome (TOS) – occurs when the nerves and vessels between the neck and shoulders compress from long periods of hunching or raising of the shoulders. Symptoms include pain in wrist/hand and lack of pulse in the affected arm. The last two fingers of the affected hand may be numb, tingle or turn blue due to a lack of blood.

Trigger Finger – occurs from a thickening on the tendons responsible for bending the fingers. These thickened tendons “catch” as they run in and out of the sheath or a tunnel as the fingers are bent. The most common cause of this disorder is tenosynovitis.

Ulnar nerve – an important bundle of sensory and motor nerve fibers to the arm, and particularly to the hand. Its sensory fibers provide feeling in the fifth and part of the fourth fingers.

Movements

Radial/Ulnar Deviation – the bending of the hand at the wrist, toward or away from the thumb (side to side movement)

Flexion (flek’ shun) – a bending motion that decreases the angle between bones, as in bending the fingers close to the hand, or raising the forearm and hand toward the shoulder.

Extension – a straightening motion that increases the angle between bones, as in straightening the fingers to open the hand, or moving the forearm and hand away from the shoulder.

Abduction (ab-duk’ shun) – movement away from the midline of the body, as in moving the arms straight out to the sides.

Adduction (ad-duk’ shun) – movement toward the midline of the body, as in bringing the arms back to their original position beside the body.

Rotation – a twisting or turning of a bone on its own axis, as in turning the wrist from palm up to palm down

Supination (su-pin-a’ shun) – the act of turning the palm up or forward

Pronation (pro-na’ shun) – turning of the palm down or backward