Therefore, ergonomists study human capabilities in relation to work demands
History
As early as the 18th century, doctors noted that workers must keep their body in position for long periods of time to develop both bone and muscle problems.
What two factors are working?
Static work: Musculoskeletal effort required to maintain a certain position, even a comfortable one.
Example: sit and work on the computer; Head and torso poses require small or large amounts of static work depending on the performance of the body position you choose.
Factors at Work (Continued)
Force: The amount of tension your muscles produce
Example: Tilting your head forward or backward from a neutral, upright position quadruples the amount of force acting on your lower cervical vertebrae.
An increase in muscle tension/strength required to support the head in a reclining position
3 main ergonomic principles:
Work activities should allow workers to adopt a variety of healthy and safe postures.
Muscle forces should be performed through the largest appropriate muscle groups available
Work activities S/B perform with joints at the mid-point of their ROM (eg head, trunk, UE).
the facts
The average person working at a keyboard can make 50,000 to 200,000 keystrokes a day.
Overexertion, falls and RMI are the most common causes of workplace injuries
Improper lifting causes an average of 125,000 back injuries each year.
Overuse of the muscles causes small tears and scars in the muscles; It contributes to inflammation and muscle stiffness
A bit of anatomy!!
Overuse and short repetitive movements ie: CTD, RSI, muscles, tendons, ligaments and nerves MSD disrupt balance
Brachial Plexus: Nerve group that supplies the muscles and skin of the ui, the front of the neck and becomes the femoral, ulnar, and radial nerves.
Nerves send signals to muscles to contract
When the nerve is compressed somewhere b/w point pressure and finger tip sensation is felt
What causes nerve compression or entrapment?
Repetitive movements
Tight muscles
Inflammation of surrounding tissues
Confusion of nerves
What are common nerve injuries?
Thoracic outlet syndrome: brachial plexus compression d/t muscle tightness neck neck from poor head position or sloppy posture.
S/SX: Numbness/tingling in hands, w/overhead activity or cradling phone b/w ears and shoulder
Nerve Injury (Continued)
Radial tunnel syndrome: Repetitive wrist and finger extension or outward rotation of the elbow.
S / Sx : Sensation from elbow to thumb base w / wrist weakness A common sx
Nerve Injury (Continued)
Cubital tunnel syndrome: ulnar nerve compression inside the elbow / repetitive bending of the elbow or resting your elbow on a hard surface
S/SX : Numbness or tingling and tingling in arm w/ ring and small fingers
Carpal tunnel syndrome: compression of the median nerve at the level of the carpal tunnel
Where is the carpal tunnel located? The wrist is formed by ligaments on the carpal bones in the hand
S / SX : Numbness or tingling in thumb, index or middle finger & ring finger; Often waking up "falling asleep" by @ hand
SX increased by driving or trying to place objects; Dropping items is a common complaint
Tendons and tendonitis
• Tendons are connective tissues that attach muscles to bones; Do some stretching or flipping
• Overuse of tendon, static or prolonged position = inflammation or tendinitis
• Wrist & very short arm muscles; @ High risk of injury / w
• "tennis elbow" or lateral epicondylitis affects the tendons outside the elbow of the finger organs
• "Golfer's close" or medical epicondylitis affects the tendons of the flexor muscle inside the elbow
What to do??
Prevention
Warm up and stretch before repetitive, static or prolonged activity
Take regular breaks every 20--30 minutes from any continuous posture
Respect the pain - stop the painful position or activity
Early signs of inflammatory process and early detection of tx
Maintain a neutral posture
Stand with back and neck w/ shoulder rest
Position equipment and work directly in front of your main task
Keep your upper arms close to your body, keeping your elbows at 90-100 degrees
Keep your feet flat on the floor, keeping your upper body weight on the “sit bones”.
Write as neutrally as possible; The safe zone for wrist movement in all directions is 15 degrees
Avoid bending the neck forward for prolonged periods of time (* remember to quadruple the force); Use a copy holder
Avoid prolonged standing; Muscle fatigue---get the circulation moving!
Modify functions:
Alternate actions frequently; Rotate heavy and/or repetitive tasks w/ lighter less repetitive tasks.
If the SX becomes worse, reassess alternative methods of work setup and appearance
Avoid repetitive or prolonged activity
w/wrist f in sentence or wrist deviation
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