Hang from a pull-up bar with both of your arms fully extended (feel free to use any reasonable grip width that is comfortable for you). Your legs should be hanging straight down with the pelvis rolled slightly backwards. From this starting position, slowly raise your legs (keeping them straight) until the legs and torso create a right angle. Once in this position, hold the peak contraction briefly before slowly returning to the starting position. Pause again in the starting position. I pause in the starting position after every single repetition to make sure that I am not swinging or using momentum in order to complete the exercise. After your descent, you should be able to completely stop yourself upon arriving back in the starting position. This is how you can ensure that you are maximizing the tension on your core muscle. Repeat for the prescribed number of repetitions.