Engineering Approaches of sitting and lying by Muhammad Arslan Yasin
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Sitting provides stability for tasks requiring visual and motor skills while being less energy consuming than standing. It places less stress on the lower extremities and lessens pressure on lower extremity circulation. When sitting, the main body weight is transferred to the seat, with some weight transferred to the floor, backrest, and armrests. Sitting erect with support for the sacrum decreases the compressive force on the lumbar discs compared to sitting in other positions such as relaxed without sacrum support, leaning forward, or leaning back. Proper desk and elbow height can also minimize shoulder muscle activity and stress on the body.
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Engineering Approaches of sitting and lying by Muhammad Arslan Yasin
- 3. Sitting
- 4. Weight Transfer: • Main body weight transferred to seat. Some transferred to floor, backrest, and armrests. Advantages: • provides stability to tasks involving visual and motor control • less energy consuming than standing • places less stress on lower extremity joints • lessens pressure on lower extremity circulation
- 5. Lower Back: Lumbar Disc Forces
- 6. Cervical Vertebrae (C1 to C7) Thoracic Vertebrae (T1 to T12) Lumbar Vertebrae (L1 to L5) Sacrum (S1 to S5) [Hall, 1999]
- 8. Chair and Disc Force Disc Force [Andersson et al., 1974a]
- 9. Disc Force [Andersson et al., 1974b] Office Desk and Disc Force
- 12. Erector Spinae Muscle • extends down the back • involved in lateral (sideways) flexion of back & extension activities, e.g. maintaining back posture in any “sitting” position • the greater the EMG (electromyography) muscle activity, the greater the compressive force on discs
- 13. Ideal desk and elbow height minimize shoulder EMG muscle activity (i.e. deltoids, trapezii, dorsal) [Engdahl, 1978] Shoulders
- 15. Higher seating changes the pelvic angle towards a more vertical posture, decreasing the compressive force on discs. But, stresses on the legs increase, which may cause swelling. Legs
- 27. LYING
- 46. Visit the Link given below to download this book! http://library1.org/_ads/30E518340912B16 31C7042C32A4B9662 These Slides are from Following Book’s CH#17 Or http://booksdescr.org/ads.php?md5=30E51 8340912B1631C7042C32A4B9662 Reference Note: To open link directly from here, first hold ctrl key and then click on link