"Flexion exercises" are physical activities or movements that involve bending a joint, like your knees or elbows, to increase flexibility and strength. Full definition
They found increased rectus abdominis muscle activity when performing trunk flexion exercises with added elastic resistance from a portable device (Perfect Abs). (strengthandconditioningresearch.com)
The middle trapezius is highly activity during retraction exercises, while the lower trapezius is highly activity in abduction / flexion exercises with the arm at or above horizontal, as well as horizontal rowing. (strengthandconditioningresearch.com)
A balanced workout would include a modest number of spinal flexion exercises and, then, only if you have a healthy back, as well as few rotation exercises to target the obliques. (cathe.com)