Bending over is your body's way of protecting your vital organs. If you think about it, the front of your body is fleshy and soft, but your back is kind of hard like a crab's shell. When you are injured, your body reacts as if it is under attack and so you bend over as a protective measure.
When all major body parts are flexed it is the fetal position.
On his or her back with their knees flexed
On his or her back with his or her knees flexed
On back with knees flexed in
The lithotomy position is a modification of the dorsal recumbent position, where the patient lies on their back with hips and knees flexed, and legs supported in stirrups.
the position of the upper extremities when they are abducted to 90 degrees and externally rotated at the shoulders and with the elbows flexed to 90 degrees.
back with knees flexed
If you mean as when a woman is giving birth or during pelvic examination, it's referred to as the lithotomy position.
Flex is a synonym for flexed.
A person grasps a bar with their palms facing themselves. They then pull themselves up to be eye level with the bar. Hold this position for as long as possible and keep track of how many seconds go by. This is a test used to determine endurance and strength.
On his or her back with their knees flexed
the position of the upper extremities when they are abducted to 90 degrees and externally rotated at the shoulders and with the elbows flexed to 90 degrees.