The most natural posture of the people is standing upright, standing upright when the spine is basically a sigmoid. But compared with the standing, the sitting position is conducive to the lower part of the body's blood circulation, reduce lower limb muscle fatigue, while sitting also maintaining the body stability.
But when we sit, the pelvis to the rear of the tilt, so that the back of the sacrum is also tilted, so that the spine from the S-shaped (normal) to the arched change, so that the spine of the disc by a lot of pressure, resulting in low back pain and other diseases.
The wrong Chair seat design will make the thigh oppression, hinder the lower limb blood circulation, causing lower extremity numbness.
Spine of the disc by the pressure, the incorrect sitting position not only can not reduce the load on the waist, but increased the load. Straight waist is conducive to reducing the pressure in the intervertebral disc, but the muscle load increases, bending waist is conducive to muscle relaxation, but increased the pressure inside the disc. So the back of the tilt and shape can affect the disc and back muscles.
Body sitting size based on below:
A, sitting high: office chair 450-550mm. Sitting high according to the calf length plus the foot of the fifth percentile as the design basis. Sitting front edge should be lower than the human knee height 30 ~ 50mm, and made a radius of 25 ~ 50mm curvature. The sitting surface can not be too high nor too low. H = calf popliteal fossa high + shoe thickness (20-40mm) - proper clearance (10-20mm)
B, sitting wide: generally greater than 380mm. Armchair is not less than 460mm. Sofa and other rest chairs more than 480mm, usually 520 ~ 560. B = body shoulder width + winter coat thickness + activity margin
C, sitting deep: GB to take 400 ~ 440mm, sofa and other seats with a deep seat can take some, take 480 ~ 600mm. Designed with a depth of 5th percentile. T = seat thigh horizontal long -60mm (gap)
D, sitting and back angle: sitting (back) tilt refers to the surface (or back) and the horizontal angle. Generally take the rest chair 19 ° ~ 20 °; 98 ° ~ 112 °, for the work chair because of the work required to move forward, so the inclination should not be too large, desirable 4 ° ~ 6 °; 95 ° ~ 100 °.
E, the height of the backrest. Generally in the lower edge of the scapula is appropriate. Waist set waist cushions to 250mm is appropriate Waist position with the back of the different angles have changed.
F, handrail height: the height of the handrail refers to the distance from the upper edge of the armrest to the sitting surface, the main role is to support the weight of the arm to reduce the shoulder burden, armrest height generally take the cushion above the effective thickness of 200 ~ 300mm.
G, chair cushion: people sitting, the body weight of about 75% by about 25c ㎡ of the parts of the calcaneal nodules around to support, sedentary will produce stress fatigue, leading to hip pain numbness. If the seat surface with soft and hard cushion, you can make the contact support area increases, so that the pressure dispersion.