TORTOISE POSE
The ancient yogis created an ingenious solution to stretching hard-to-access muscles—Kurmasana. In this pose we connect the arms and legs to stretch the lower back and hips. The main story here is the trunk flexing forward. Linking the elbows behind the knees creates a subplot to this story. You can see that straightening the knees presses down on the backs of the arms and flexes the trunk deeper. Contract the biceps and brachialis muscles to bend the elbows and protect them from hyperextending. When the thighs press onto the upper arms, attempting to bend the elbows with the palms fixed on the floor draws the torso deeper into the pose, giving that extra inch or two of stretch where yoga really happens.
BASIC JOINT POSITIONS
Get a feeling for the stretch by starting with the knees and elbows bent. This may be as far as you will want to go in the pose. Then gently press the backs of the knees into the upper arms, keeping the elbows bent to protect them from hyperextending. As you become more flexible, move the thighs higher up on the backs of the arms, above the elbows, to gain greater leverage in pressing the trunk down when you straighten the knees. Use poses such as the bent-knee version of Supta Padangusthasana to prepare the gluteals and upper portion of the hamstrings and Upavistha Konasana to stretch the back muscles.
STEP 1 Contract the abdominals to flex the trunk. Activate the psoas to flex the femurs. The psoas major originates from the lumbar spine and, as such, aids to draw the trunk deeper into the pose. Be aware, however, that the hips are fully flexed and that the hip flexors have limited capacity to contract further and add to this movement. In situations like this, you can connect the upper and lower extremities to deepen the pose.
STEP 2 Place the arms under the legs with the palms on the floor. Press the mounds at the base of the index fingers down to pronate the forearms, using the pronator teres and quadratus muscles. As you enter the pose, extend the elbows by contracting the triceps to deepen the placement of the arms under the legs. Attempt to lift the elbows and upper arm bones against the backs of the legs. This engages the lateral and posterior portions of the deltoids, flexing the trunk deeper. Draw the shoulders away from the ears by contracting the lower third of the trapezius.
STEP 3 Straighten the knees by activating the quadriceps. This presses the legs onto the backs of the arms and creates an intense stretch of the back muscles and of the gluteus maximus, the main hip extensor. The pull of the stretching gluteus draws the thighs into external rotation, turning the kneecaps outward. Use the tensor fascia lata to counteract this by rotating the femurs inward. The cue for this is to press the heels into the mat and attempt to drag the feet apart. The feet will not move because they are constrained on the mat, but the tensor fascia lata and gluteus medius will contract and internally rotate the femurs. If you look under the tensor fascia lata here, you will see the gluteus minimus. This muscle synergizes hip flexion and internal rotation and stabilizes the head of the femur in the socket. Visualize it in action when practicing Kurmasana.
STEP 4 Dorsiflex the ankles by contracting the tibialis anterior muscles. The feet tend to turn inward in Kurmasana. To overcome this, lift the toes using the toe extensors and evert the soles of the feet with the peroneus longus and brevis muscles on the outsides of the lower legs. Counterbalance eversion by engaging the tibialis posterior to dynamize the arches. All of this serves to open the soles of the feet, illuminating minor chakras in this region.
STEP 5 Pronate the forearms with the pronators teres and quadratus. Engage the flexors carpi radialis and ulnaris to flex the wrists. Attempt to bend the elbows by contracting the biceps and brachialis muscles. This protects them against hyperextension and deepens the pose via closed chain contraction of the biceps. Engage the quadriceps to straighten the knees and press the thighs into the backs of the arms, flexing the trunk further. This illustrates how to produce additional movement in the hips and pelvis by connecting the arms and legs.
SUMMARY All of this work results in a focused stretch of the lower back muscles, including the quadratus lumborum and erector spinae. The gluteus maximus, hamstrings, and adductor magnus also stretch. When you come out of Kurmasana, balance it with Tadasana, a posture that extends the back. Notice how your Tadasana improves after this stretch.