This exercise is remarkable from several perspectives. It is isometric, functional, and highly effective.
Relatively unknown outside of the gymnastics community this exercise may be the most effective abdominal exercise we know of!
The L-sit is performed by supporting the body entirely by the arms and holding the legs straight out in front. The legs’ posture in the L-sit places an enormous, if not unbearable, moment or torque about the hip that must be counteracted by the abdominals to keep both the legs up and the spine from hyperextending. The exercise is isometric; i.e., it involves no joint movement. Being isometric, CrossFit quantify its performance not in reps but by time. As for efficacy, the L-sit may have no peer among abdominal exercises.
CrossFit makes this claim not on the basis of our position on abdominal muscle functionality but on the simple observation that athletes who have developed their L-sit to the point where they can hold it for three minutes subsequently find all other abs work easy. The gymnasts’ unrivaled capacity at hip and trunk flexion is in large part due to their constant training and practice of this exercise.
The practice of the L-sit is for some very tough – they just can’t seem to find the muscles that raise and hold the legs. The key is to keep trying. Two successful approaches for working up to the L-sit include hanging from a pullup bar and raising locked legs as far as possible and holding or working the L-sit by holding one leg at a time alternately in the L posture.
Though the L-sit can be performed from nearly any horizontal surface we recommend parallel bars, parallettes, and the floor as platforms for this exercise.
The L-sit is hardest from the floor because the floor comes up quickly as the legs sag even a little bit. Using the parallettes for the very reason that it allows practice at less than perfectly horizontal leg position for the beginner, but measuring and competing at the L-sit should be done from the floor.
Measure your progress in the L-sit in 15-second increments. Give yourself one point for every fifteen seconds you can hold the “L”. Twelve points is your goal and with regular training and practice, you should be able to get to 12 points, or three minutes, within six months. During warm-up and cool-down is the natural place to play with this movement although the dedicated gymnast will find uncountable surfaces and opportunities to play with this superb exercise.