This exercise is also a great way to improve your overall ability to perform pull-ups as it develops all of the key components, and helps you develop the full body tension and stability that is vital if you hope to thrive at doing pull-ups. That being said, it is extremely advanced so start out by performing this exercise using two arms, and if you struggle to keep your legs extended, start out with your knees bent.
For the duration of the exercise, it's vital that you do not allow your lower back to hyperextend, ribcage to flare, or arm to get pulled out of its socket. Your head, torso, and hips should remain level and in a stacked position. You will achieve this by keeping your anterior core braced, ribcage tucked towards your hips, shoulder blades retracted and depressed (drawn in towards your spine and down towards your opposite hip), glutes engaged (it's tough while being in this position), legs flexed, and feet dorsiflexed.