The average person spends 12 hours per day sitting. Most people do not notice how often they sit throughout the day because we sit when we sit constantly for short amounts of time that tend to add up: while traveling, eating, working, studying, relaxing, reading, or waiting. Our posture when sitting can have major consequences on our backs if we don’t make a conscious effort to sit right.

Random facts about sitting that make you sound smart:

• When sitting, pressure falls onto the “sit bones” (ischial tuberosities). The pressure exerted on the buttocks is estimated to be as high as 85 to 100 psi.1 If we cross our legs that pressure nearly doubles.1
• When a person sits up right in a chair with proper support, approximately two thirds of a person’s body weight are distributed to the chairs seat, backrest, and armrest.1 Benches and stools that balance your body weight on a smaller surface increase pressure even more.1
• Your feet should touch the ground in such a way that they support one third of a person’s body weight or less to minimize leg discomfort when seated.

Research shows that sitting compresses the intervertebral disk in your spine more than standing. Essentially, standing puts lets compression on your spine than sitting, but if you are going to sit let’s talk about how to do it right.2 Slumped sitting, cross-legged sitting, and extension sitting caused significantly higher compressive loads in the L3/L4 and L4/L5 intervertebral joints than upright sitting.2 Research has suggested that increased disc pressure on the spine will over-load the spine and cause the discs to wear out more quickly.1

So, how to do you reduce the stress of sitting on your sit bones and spine?

1. Dropping the incline on backrest from vertical to 110∞ (angle between the backrest and seat) will reduce the amount of disc pressure on the spine.

2. Adjust the seat of the chair in a forward tilt. A forward tilted seat pan will allow the lumbar spine to maintain lordosis and reduce pressure on the discs. Most furniture these days are built for comfort and not health, so your butt may sink lower than your knees when you sit which can irritate your spine.

3. Do not slouch! Disc pressure is greatest when sitting in a slouched posture.

4. Sit with your legs supported on the ground. Keeping your feet supported while sitting will maintain lower body circulation and prevent the weight of dangling legs contributing to low back strain.

Sources:
Jacobs K. Ergonomics For Therapists. 3rd ed. St. Louis: Mosby Elsevier; 2008.
Mengjie Huang, Hajizadeh K, Gibson I, Taeyong Lee, Huang M, Lee T. Analysis of compressive load on intervertebral joint in standing and sitting postures. Technol Health Care. 2016;24(2):215-223. doi:10.3233/THC-151100