1. Copyright Catherine M. Burns1 SEATING, CTD, MUSCLE FATIGUE

2. Copyright Catherine M. Burns2 Seating Design Other cause of back pain is sitting for long duration jobs Loss of correct spinal curvature causes increased disk pressure Slumping creates uneven pressure on disks, compressing in front and compressing at the back Disk pressure standing is 30-40% lower than sitting

3. Copyright Catherine M. Burns3 Seat design Erect sitting posture provides the least stress Back rest must tilt back slightly (110 to 120 degrees) Lumbar support, ideally adjustable Arm rests Add lots of breaks to the work schedule, move around

4. Copyright Catherine M. Burns4 Cumulative Trauma Disorders Smaller exertions performed more frequently cause damage also called RSI (repetitive strain injury)

5. Copyright Catherine M. Burns5 Cumulative Trauma Disorders Fingers: Raynaud’s disease Hand/Wrist: Carpal tunnel syndrome. –rapid and repetitive finger movements –bent wrist –keyboard work Tennis/Golfer’s Elbow –tendon irritation Shoulder: Pitchers arm/Swimmers shoulder –rotator cuff irritation

6. Copyright Catherine M. Burns6 Physiology tendon irritation muscle loading due to unnatural postures blood obstruction

7. Copyright Catherine M. Burns7 Solutions Breaks and job scheduling Warm up activities Task rotation Proper workstation design

8. Copyright Catherine M. Burns8 Matching Muscles with Work Important to match muscle size with the task Use big muscles for tasks requiring alot of strength –legs vs arms –arms vs. fingers

9. Copyright Catherine M. Burns9 Matching Muscles Muscles have different strengths in different directions –hands turning inwards > outwards –pulling down > pulling up (unless legs used) –people get more strength through the vertical by using full body, eliminating moment arm on the spine

10. Copyright Catherine M. Burns10 Static vs. Dynamic Work

11. Copyright Catherine M. Burns11 Static Work Examples of static work –standing –holding things –holding arms up –pushing or pulling objects Max force is reduced in static situations –Longer rest periods needed –Higher energy rate consumption –Most activities involve both

12. Copyright Catherine M. Burns12 Effects of Static Work Physiological effects of chronic loading –arthritis in joints –tendonitis –muscle spasms –invertebral disc problems

13. Copyright Catherine M. Burns13 Standing, Static Work Effects of long periods of standing in one place –muscular fatigue –also blood flow problems due to pressure at level of feet –varicose veins, swelling, ulceration