Is sitting straight up the healthiest way to sit?

Question

When I was in school, my teacher always told me "Sit up straight stop slouching!". I am sure many others have heard this too, the thing is though, sitting up with straight back is very uncomfortable, and your back gets tired.

Not always are you told WHY you should do it either. But sometimes it's because you look lazy, and it's improper to slouch, sometimes you're told because it's better for your back to sit straight.

I focus this question on the health aspect of sitting up straight.

Blog: "Stop slouching and Sit Up Straight!"

I know, I sound like your second grade teacher, or your mother at the dinner table with those constant, nagging phrases that used to drive us nuts, “Sit up straight!”1

Now, I hear patients coming into the clinic complaining of their spouses getting on their last nerve because they’re not standing up straight. But, if your spouse is telling you to sit up straight, he/she could be saving your body from many issues.1

Sit straight up

What is good posture?

Posture is the position in which you hold your body upright against gravity while standing, sitting or lying down. Good posture involves training your body to stand, walk, sit and lie in positions where the least strain is placed on supporting muscles and ligaments during movement or weight-bearing activities.2

Correct sitting position

Sit up with your back straight and your shoulders back. Your buttocks should touch the back of your chair.2

Sitting with back at 90 degree, is not comfortable at all, even if you're being told so. And also you're told it's the best way for your back. But if something is uncomfortable, it might be a warning from your body. Is sitting straight really good for the health of your back?

Answer 1

No, sitting straight is bad for your back.

Medical paper about sitting

RESULTS

We found IVD height showed a tendency to decrease as lumbar lordosis decreased in variable sitting positions from reclining to forward flexion. The NP [nucleus pulposus] showed movement within a limited range in normal IVDs [intervertebral disc] without change of its overall area. The optimal sitting position was with a trunk-thigh angle of 135 degrees. This position was shown to cause least 'strain' on the lumbar spine, most significantly when compared with an upright 90 degree sitting posture.

Sitting up straight causes unnecessary extra strain to your back, best way to sit is in a 135 degree position.

BBC article about sitting

Spinal disk movement occurs when weight-bearing strain is placed on the spine, causing the disk to move out of place.2

Disk movement was found to be most pronounced with a 90-degree upright sitting posture. It was least pronounced with the 135-degree posture, suggesting less strain is placed on the spinal disks and associated muscles and tendons in a more relaxed sitting position. The "slouch" position revealed a reduction in spinal disk height, signifying a high rate of wear and tear on the lowest two spinal levels.2

When they looked at all test results, the researchers said the 135-degree position was the best for backs, and say this is how people should sit.2

That said there is several things that might make sitting like that difficult. First of all you might slide off leaning that much back.

"As to what is the best angle between thigh and torso when seated, reclining at 135 degrees can make sitting more difficult as there is a tendency to slide off the seat: 120 degrees or less may be better.".2

The other problem is culture. You're supposed to sit straight since that is what is considered the proper way. Health is not always taken into consideration then.

How ladies should sit gracefully

Sit up straight with legs together and heels slightly to the rear. You can sit with legs in front of you, angle your knees to either left or right side, or cross your ankles, but never sit with legs apart, it's a mortal sin to poise.

For dummies advice about Business Etiquette

Take care in the way you sit, for no other position connotes so much on its own. Think of the diversity of sitting positions that you've seen in business meetings, from practically horizontal to alert and upright. Sit with a straight back and with your legs together in front of you or crossed, either at the knee or at the ankle.

Ask men about Office Etiquette

Sit up straight: When you slouch, you seem lazy and apathetic. Good luck with that promotion if you keep it up.

Even if it's better for your health to NOT sit with your back straight it's considered lazy, to lean back as much as 135 degrees. And people around you might even complain if you sit like that.

The best way for your health is to lean back a bit more though, 'slouch' a bit, and sit comfortably.