Location of internal and external oblique muscles
The internal abdominal oblique is a broad thin muscular sheet located on the lateral side of the abdomen while the external abdominal oblique is a paired muscle located on the lateral sides of the abdominal wall. As both names suggest, the direction of its fibres are obliquely oriented, making up the anterolateral abdominal wall. Together with the other abdominal muscles, the internal oblique affects the movements of the trunk, maintaining abdominal tension and increasing intra-abdominal pressure. The internal oblique muscle is also found deep in the external oblique with both working together to produce movements of the spine as well as to compress the abdominal viscera. As the external oblique muscle originates from the external surfaces of ribs 5-12, with the muscle fibres fanning out towards the midline and inferior margins of the abdomen, it is considered as the largest and most superficial of the lateral abdominal muscles.
Functions of internal and external oblique muscles
The internal abdominal oblique muscle has several functions that are dependent upon on the parts where the muscle contracts. Upon contraction, the internal abdominal oblique flexes the trunk, simultaneously causing compression of the intra-abdominal viscera, thereby increasing the intra-abdominal pressure which is utilised for functions including breathing, singing, defecation, and more. While the external oblique muscle has a variety of functions dependent on its contraction – either unilaterally or bilaterally. When contracted unilaterally and in synergy with the internal abdominal oblique, it rotates the trunk to the opposite side. However, when contracting bilaterally, the muscle works together the internal oblique to flex the trunk anteriority. This activity also increases the tone of the abdominal wall and positive intra-abdominal pressure, which is a part of various physiological process that includes exhalation, and labour. Along with other muscles of the abdominal wall, both internal and external oblique are highly important for maintaining normal abdominal wall tension and therefore, the contraction of these muscles play both a protecting and supporting role to reduce the risk of abdominal hernias.
Yoga poses that engage external oblique muscles
- Parivrtta Parsvakonasana (Revolving Lunge)Considered as one of the most common twisting poses due to its versatility, the revolving lunge can be performed by almost anyone – from beginner to an advanced yoga enthusiast with varying degrees of difficulty. As this position is performed, the opposite elbow is brought to the outside of the forward leg, with the body twisted towards the ceiling. This pose also stimulates the opening of the internal organs, allowing a deeper twist towards the ceiling which can be performed with the hands clasped together. To do this pose, simply stand with your feet three to four feet apart, point your right feet towards the right with your thigh at 90 degrees, extending your left leg straight with the heel lifted off the mat. Ensure that the weight is brought towards the right thigh and hinge your hip forward, twisting to the right and placing your left palm beside your right pinky toe, with your right arm extended towards the ceiling and gaze through your right thumb.2. Utthita Parsvakonasana (Side Angle Pose)