The channels (meridians) of Chinese medicine are oriented along anatomical planes. Understanding this arrangement helps understand the channels roles with movement.

The Western anatomical planes can help understand the arrangement of the channels on the body. The sagittal plane divides the left and right halves of the body. If this is a midsagittal plane (along the midline), then the plane would enter the body at the Ren Mai (Conception Vessel) and exit at the Du Mai (Governing Vessel). If the plane were moved off the midline, it would cover the Spleen, Stomach, Lung or Large Intestine channels, depending on how far lateral or medial the sagittal plane is located.

Note that for this to work for the Lung and Large Intestine channels, the person would need to be standing with the arms down by the side and the palms facing inward as opposed to standard Western anatomical position where the palms face forward. This more natural relaxed palm position is how the Chinese system references channels. With the palms facing inward, the radial aspect of the arm is forward and the sagittal plane would penetrate at the Lung and Large Intestine channels. These channels are anteromedial and anterolateral (radial, ventral and dorsal surface of the arms). These channels parallel their related Spleen and Stomach channels on the lower extremities which are also anteromedial and anterolateral.

Line represents the rectus femoris, a muscle
of the ST jingjin. It performs hip flexion and
knee extension, which are sagittal plane
movements.

The channel sinews (jingjin) of these four channels include muscles like the biceps brachii (LU), rectus femoris (ST), rectus abdominis (ST), tibialis posterior (SP), flexor hallucis brevis (SP), and pectoralis minor (LU). These muscles all attach approximately where the sagittal plane would enter the body, and they move the body in the sagittal plane. They govern elbow and shoulder flexion, hip flexion and knee extension, and trunk flexion; they lift the arch, and move the toes.

This same plane would exit the body in the back and would access the Urinary Bladder, Small Intestine, Heart, and Kidney channels. The Kidney channel does have a portion on the front of the abdomen and chest and we will return to it, but these channels generally counter the action of the front channels. Included are things like the extensor carpi ulnaris (SI and HT), triceps brachii (SI), the erector spinae (UB), the hamstrings (UB), semimembranosus (KID), and the gastrocnemius (UB) and soleus (KID). These channel sinews extend the back and hip, extend the shoulder, perform ulnar deviation of the wrist, and perform plantar flexion of the ankle.

Line represents the biceps femoris, a muscle
of the UB jingjin. It performs hip extension and
knee flexion, which are sagittal plane movements

A portion of the KID channel does travel in the abdomen, I interpret this to be the transverse abdominis, which wouldn't so much flex or extend the trunk, but would support and lengthen the spine along the midsagittal line. This works with the Urinary Bladder channel to give upright posture. The channel also travels into the chest and allows the chest to open in upright posture. Below is a video that highlights a chest opening qigong pattern which alternates between the back and the front channels, all creating movements in the sagittal plane.

The frontal plane separates the body into front and back halves. It would enter and exit the body along the sides, the lateral and medial portions of the extremities, and lateral aspects of the head and torso. This plane would travel through the shaoyang channels (Gallbladder and Sanjiao) on the lateral aspect of the extremities, torso and head, and the jueyin channels (Liver and Pericardium) on the medial aspect of the extremities.

These channels would include muscles like the abdominal obliques (GB and LIV), hip abductors (GB), hip adductors (LIV), coracobrachialis (a shoulder adductor in the P jingjin), the deltoids and upper traps (SJ and GB), and the finger extensors (SJ).

These sinew channels would move the body in the frontal plane, performing such actions as side bending, hip abduction and adduction, and shoulder abduction and adduction.

Careful examination of the muscles that side bend the body, and abduct and adduct the hip shows something interesting. These muscles, such as the abdominal obliques, zigzag around the body. While they are indeed active in side bending, they also spiral around the body and perform rotation, a transverse plane movement.

Muscles like the serratus anterior (P), the gluteus maximus (GB), the pectineus (LIV) and other muscles can be involved with side bending, but they can also rotate the body. Check out the video below to see an example of a qigong movement called the tuō yāo which highlights rotational movements involving these jingjin.