The ancient Chinese book of wisdom, the I Ching, has a hexagram devoted to the practice of yoga entitled “Keeping Still.” To paraphrase the Wilhelm translation, “Movement posits stillness as an alternative.” We move the body to position it in the postures, but ultimately we seek stillness and stability in our asanas. Co-activation of muscles is one way to achieve this quietude. There are many ways to perform co-activation, but all involve simultaneously contracting two or more muscles. For example, we can stabilize the pelvis by simultaneously contracting the psoas of the forward leg and the gluteus maximus of the rear leg in a standing pose. Stillness in the pelvis is then transmitted to the rest of the body (Fig. 1).
FIGURE 2 These images illustrate the dynamic process of co-activating the psoas and gluteus maximus using a series of standing poses that progressively turn the pelvis. You can sequence asanas in this way to awaken conscious control of these two core muscles—particularly the psoas. This new-found awareness allows you to directly contract these muscles in other pose categories, deepening trunk flexion and improving stability.
FIGURE 3 Co-activation can also be used to stabilize the shoulders and arms. Turn the palms to face down. This internally rotates the forearms and engages the pronators teres and quadratus. Externally rotate the shoulders to activate the infraspinatus and teres minor muscles of the rotator cuff. Then straighten the elbows by contracting the triceps. These actions combine internal rotation of the forearms with external rotation of the shoulders to produce a “wringing” effect across the elbows, tightening the elbow ligaments and stabilizing the joints. This creates a helical coil up and down the arms.
FIGURE 4 You can co-activate the accessory muscles of breathing to expand the ribcage, open the chest, and improve lung ventilation. Begin by contracting the rhomboids to draw the shoulder blades toward the spine. This stabilizes the scapulae and opens the chest. Maintain this position and then engage the pectoralis minor. You can isolate this muscle by attempting to roll the shoulders forward. The rhomboids will prevent the shoulders from moving, so the force of engaging the pectoralis minor is transmitted to its origin on the ribcage, lifting it. Activate the serratus anterior to expand the chest further. You will notice the breath deepening.
FIGURE 5 The foot and ankle are your connection to the earth in the standing poses. Use co-activation of muscles to stabilize this foundation. Turn the foot in and lift the arch by contracting the tibialis posterior. This muscle also bridges the two bones of the lower leg (the tibia and fibula), stabilizing the ankle joint. Begin by activating the tibialis posterior, and then engage its antagonist muscle group, the peroneus longus and brevis (located on the outside of the lower leg). To isolate the peronei, press the ball of the foot into the mat. Feel how co-contracting this agonist/antagonist group stabilizes the lower leg, ankle, and foot.
FIGURE 6 Co-contraction of the psoas and gluteus maximus stabilizes the pelvis from front to back in one-legged balancing poses. Visualize these muscles engaging during your practice.
FIGURE 7 Co-contraction takes place automatically when we stand on one leg, as in Tree Pose. The gluteus medius and tensor fascia lata are abductor muscles typically used to draw the hip away from the midline. However, these muscles also pull downward on the ilium bone of the pelvis when we stand on one leg. If they didn’t engage, the pelvis would shift over to the standing-leg side and we would lose balance. You can feel the tensor fascia lata and gluteus medius contracting by placing one hand on the outside of the hip in Vrksasana. In addition, the adductor muscles on the inner thighs co-contract to further stabilize the pelvis and hip. Visualize these muscles to gain awareness of this action.
FIGURE 8 We are sometimes instructed to “hug the thigh bone” in a yoga class. This is an example of co-contraction. You can use a series of cues that isolate the different muscles surrounding a bone in order to achieve this effect. Apply this technique to correct hyperextension of the knee. Begin by isolating the hamstrings. The cue for this is to slightly bend the knee and attempt to “scrub,” or drag, the front foot toward the back, as shown. The mat will prevent the foot from moving, but the hamstrings will engage. The hamstrings are knee flexors and contracting them prevents hyperextension. Then, maintaining tension in these muscles, engage the quadriceps to straighten the knee. From this image you can see that this agonist/antagonist muscle group, the hamstrings and quadriceps, surrounds the femur and crosses the knee joint. Co-contracting these muscles creates the “hug” that we sometimes hear about and prevents hyperextension of the knee in the pose.
