Although the L-sit does work the abdominal muscles, it is a full-body exercise that engages the quads, hip flexors, shoulders, triceps, and lats. The L-sit is an effective exercise for building abs and can be safer than other core moves that involve too much twisting or flexion. It’s important to remember that abs are built in the kitchen, so when maintaining a healthy, balanced diet, you’ll start to see those muscles pop out.