Those abdominal muscles on either side of your rectus abdominus are known as obliques, for probably obvious reasons.

These effect lateral flexion and forward flexion of the spine, in conjunction with the rectus, as well as trunk rotation, and / or lower body rotation. Please avoid confusing these superficial muscles with the intercostals, which span the space between your ribs.

	External Obliques The external obliques originate on the borders of the lower eight ribs, at the side of the chest where they dovetail into the finger-like looking serratus anterior. These muscles angle diagonally, down and inward to insert onto the front half of the crest of the ilium, inguinal ligament, crest of the pubis, fascia of the rectus abdominus at the lower front.
	Internal Obliques The Internal Obliques, run diagonally as well, yet originate below, on the upper half of the inguinal ligament, the anterior two thirds of the crest of the ilium, and the lumbar fascia, and run upward to the costal cartilages of the eighth, ninth and tenth ribs and to the linea alba.

Training Your Obliques