Bleachers have no back support. If I hunch over, my lower back hurts. If I sit up straight, my lower back is fine but my shoulders and upper back hurt.
Bleachers have no back support. If I hunch over, my lower back hurts. If I sit up straight, my lower back is fine but my shoulders and upper back hurt.
Your posture muscles are mostly around the thoracic spine but are quite complicated. The weight of your head, and shape of your torso have a big impact on how much strain is placed on the muscles that enable posture. The heavier you are up high, the harder posture will likely be. Most people don’t really notice it very much.
Like after 6 weeks in a bed with a neck brace after my broken neck and back, the weight of my head felt massive. I had muscular damage, but the atrophy was also a major factor. It was so bad that getting up required rolling onto my side and using my arm to get the weight over my shoulders. Even now after 10 years, that feeling of being uncomfortable sitting without back support, is very similar to how I feel, mine bets much worse quickly, and it only takes a few minutes before I fall apart when I try.
In other words, it is mostly muscular endurance and weight.