Repetitive Strain Injury (RSI)

ECE 417/617:Elements of Software Engineering

Stan BirchfieldClemson University

You are a computer athleteA dangerous occupation:

This is also dangerous:

As a typical computer user, you “walk” several miles each day on your fingertips

(250 keystrokes / min) * (2 in / keystroke) * 4 hours = 2 miles

What is RSI?

• Repetitive Strain Injury (RSI)– is pain or nerve problems in upper extremity (hands,

arms, or shoulders)– can also include neck and back– is a soft tissue disease (muscles and nerves)– is an overuse syndrome

• Symptoms:– burning, numbness, tingling, pins-and-needles– dull aching OR specific, intense pain

• Controversial:– many deny it exists– sufferers receive little support from employers

The cost of RSI

• $20 billion per year [Information Week, Nov. 9, 1992]

• $29,000 average compensation

• accounts for 60% of all job-related injuries [Department of Labor]

• Approx. ¾ of all jobs require using a computer

Carpal tunnel syndrome

• Carpal Tunnel Syndrome is a specific type of RSI

• Swelling increases pressure on nerves to fingers

• Problem is only in wrist

• Most RSI is more widespread (neck, back, arms, shoulders)

What causes RSI?

Cantilevers

stress

Bad posture

ulnar deviation dorsiflexion

pronation

slouching

Anatomy of hand nerves

Thoracic outlet:• b/w collarbone and rib #1Brachial plexus:• braided nerves• also supplies shouder,

neck, and arm muscles

brachial plexus

Three nerves:• Median

through carpal tunnel• Ulnar

“funny bone”• Radial

extensor muscles

topview

bottomview

Traditional solutions• Surgery

• Wrist braces

• Anti-inflammatory drugs

• Pain killers

• Cortisone shots

• Ergonomic keyboard, mouse, etc.

Why should you be cautious?

Keep in mind

• Long-term problem long-term solution• The pain may move• The pain may go away temporarily, even

though the problem is not solved• Musculoskeletal system (muscles,

tendons, and bones) adapts• Body is meant to move– Ergonomics are important, but beware of

trying to achieve “perfect posture”

Outline of a solution

1. Stretching

2. Movement

3. Strength

Also posture, massage, remove wallet from back pocket,hot/cold treatment, ergonomic keyboard / mouse, better chair, ...

Computer vision syndrome (CVS)

• Computer screens are different from printed material– Contrast is not sharp– Edges of characters are not well-defined

• Our eyes have difficulty focusing– Instead, eyes drift to the resting point of

accommodation (RPA)– Eyes involuntarily move to RPA, then strain to regain

focus

• Results– Fatigue, tired eyes from continuous flexing– Dry eyes from not blinking enough

Final advice

• You think RSI will never happen to you• When you start feeling pain, you will

– ignore it– learn to bear it– expect it to go away on its own

• When your pain disappears temporarily, you will think problem is solved

• When your pain intensifies gradually, you will continue to ignore it until it is serious

Pain is your body’s way of telling you that something is wrong! Be aware! Do not ignore the symptoms! Seek help when the pain first appears, before it becomes a serious problem!

For further reading

• Damany and Bellis,It’s Not Carpal Tunnel Syndrome!

• Pascarelli, Repetitive Strain Injury