FIGURE 1 Co-contract the elbow flexors and knee extensors in Paschimottanasana. Engaging the biceps and brachialis muscles bends the elbows, drawing the trunk deeper into the forward fold. Activating the quadriceps extends the knees and produces reciprocal inhibition of the hamstrings, allowing them to relax into the stretch. You can see how both muscle groups contribute to the final pose.
FIGURE 2 Co-activate the psoas and rectus abdominis in forward bends. A cue for engaging the psoas is to squeeze the torso against the thighs. Contracting these muscles together flexes both the trunk and the hips, deepening the pose.
FIGURE 3 In Supta Padangusthasana A, engage the gluteals to extend the hip of the leg that remains on the ground. Do this by squeezing the buttocks and pressing the heel into the mat. At the same time, activate the psoas and its synergists on the leg that is held by the hands. Do this by drawing the foot towards the head from the hip.
Co-contracting the gluteals on one leg and the hip flexors on the other produces a “wringing” effect across the pelvis, stabilizing it.
FIGURE 4 Grip the foot and attempt to turn the palms upward (supination), locking the connection between the hands and the foot. Co-activate the muscles of the forearms, upper arms, and shoulders to draw the leg deeper into the stretch. Then engage the biceps and brachialis muscles to bend the elbows. Hold the foot tightly and draw the hands upward (as if you were lifting an object over your head). This activates the anterior deltoids. Externally rotate the shoulders by engaging the posterior deltoids, infraspinatus, and teres minor muscles. Finally, draw the scapulae down the back by contracting the lower third of the trapezius. This frees the neck and helps to open the chest.