HALF-MOON POSE
The main story or the primary focus of ardha chandrasana is an intense stretch of the hamstring, gluteal, and gastrocnemius muscles on the back of the standing leg. A subplot is the balancing act that takes place in the pose. The actions of maintaining our balance and stretching the muscles on the back of the standing leg are interconnected. For example, contracting the quadriceps and hip flexors of the standing leg helps to maintain balance but also signals the muscles at the back of the leg that are stretching, the hamstrings and gluteals, to relax through the physiological process of reciprocal inhibition. Ardha Chandrasana is a natural progression from the previous two postures (Virabhadrasana II and Utthita Parsvakonasana), projecting the body forward into a balancing pose. Combining the poses in this manner creates synergy and continuity within the practice.
Use the principle of triangulation to locate the focal point in Half-Moon. Triangulation does not necessarily refer to a geometric triangle, but rather a conceptual one, wherein the actions of two structures work together to affect a third. In Ardha Chandrasana, flexing the trunk tilts the pelvis forward and draws the origin (ischial tuberosity) of the standing-leg hamstrings up; this forms one corner of the triangle. Straightening the standing leg takes the insertion of these same muscles in the other direction, forming another corner of the triangle. These two actions combine to lengthen (stretch) the standing-leg hamstrings, creating an apex for our conceptual triangle.
Now, what about the subplot in this pose, the balancing act? How can we use basic principles of physics to assist in the asana? First, if you start to lose balance, you can regain stability by bending the standing knee. Slightly lower the raised leg for additional stability. Both of these actions lower the center of gravity and make it easier to balance. Once you regain stability, engage the quadriceps to straighten the knee while keeping the hip flexed over the thigh. Use the raised leg like a tight-rope walker uses a pole. That is, if you start to fall back, shift the raised leg forward; if you start to fall forward, shift the leg back. The soundtrack of the pose is the breath; focus on your breathing to improve your balance.
BASIC JOINT POSITIONS
To activate the psoas muscle, bend forward and place the elbow on the knee and press down with the torso. Alternatively, come straight into a shallow Trikonasana. Next, bend the standing leg and step the back foot forward about one foot; at the same time, place the hand about twelve inches in front and to the outside of the standing leg.
Lean the weight forward onto the hand and begin to lift the straight back leg, like a teeter totter. Maintain the standing leg bent and align the pelvis over the ankle. Finally, lift the torso by activating the quadriceps to straighten the standing leg (extending the knee) in an action similar to a hydraulic lift. Use the upper arm for balance and as a tool to lever the chest open.
STEP 1 Laterally flex the trunk by engaging the oblique abdominals, the deep back muscles, and the hip flexors. Use the image here to aid in visualizing these muscles contracting. Notice how the rectus femoris and sartorius muscles cross the pelvis and hip, making them synergistic hip flexors. You can engage the rectus femoris by lifting the kneecap toward the pelvis.
STEP 2 Lift the back leg using the hip abductors—the gluteus medius, gluteus minimus, and tensor fascia lata. One of your goals is to have the kneecap of the raised leg facing directly forward. If it is facing upward, internally rotate the thigh bone by engaging the gluteus medius and tensor fascia lata. Activate the quadriceps to straighten the knee. Evert the foot by contracting the muscles on the outside of the lower leg, the peroneus longus and brevis. This action opens the sole of the foot, stimulating the minor chakras in this region.
STEP 3 Firmly contract the quadriceps of the standing leg. This straightens the knee, lifting the pelvis and trunk upward. Extending the knee moves the insertion of the hamstrings on the lower leg farther away from their origin on the ischial tuberosity. Contracting the quadriceps initiates reciprocal inhibition of the hamstrings, causing them to safely relax into the stretch.
STEP 4 Use the muscles on the side of the standing leg to assist in balancing. The gluteus medius, minimus, and tensor fascia lata flex the hip and stabilize the pelvis. The tensor fascia lata also synergizes the quadriceps in straightening and stabilizing the knee. Balance the contraction of the peroneus longus and brevis (eversion) with that of the tibialis anterior and posterior (inversion) to spread the weight across the sole of the foot. Maintain most of the weight on the front part of the heel.
STEP 5 Contract the upper rhomboids to draw the shoulder blade toward the midline of the back, opening the chest and turning it upward slightly. Reach toward the floor with the lower arm by activating the serratus anterior, thereby drawing the scapula away from the spine. A cue for this action is to imagine pressing your hand against a wall with your body turned sideways. Contracting the infraspinatus externally rotates the arm bone, and the triceps straighten the elbows of both arms.
SUMMARY You can see how this focuses a stretch on the muscles at the back of the standing leg—the hamstrings, gluteus maximus, and gastrocnemius. Consider the secondary stretch taking place, including the psoas of the raised leg, the upper-side erector spinae and oblique abdominals, the pectoralis major, the serratus anterior, and the biceps.
