The phrase "slouched position" means sitting or standing with a hunched or curved posture, leaning forward and not sitting or standing up straight. Full definition
It will cause less straining with a reduced slouching position. (elearningindustry.com)
We Have Kids noted that when you are in a slouched position, it puts stress on your back muscles and spine and can cause considerable back pain. (romper.com)
That's why you will see a parent slap a slouching kid on their back asking them to «stand up straight», but this only lasts a few seconds before the child goes back to a slouched position. (strengthsensei.com)