Mastering the Human Flag The human flag or side lever in gymnastics is one of my favourite exercise. It builds shoulder, oblique, abs and lower back strength synergistically. So most noteworthy it develops strength through the lateral and spiral lines of the body. Often extremely neglected muscles within the body. Ever heard of someone do a workout focused on the obliques, quadratus lumborum, tensia fasciae latae and adductors? I'm guessing never. However these muscles in conjun...