Once all major joints of the body have been warmed up by practicing Pranayama breathing and the first few postures, you are ready for Eagle pose, garudasana! This pose opens up the joints of the ankles, knees, hips, shoulders, elbows and wrists.
By twisting your limbs "like ropes" Eagle pose creates compression of blood and lymph flow headed to spots like your legs, kidneys and the lymph nodes in your armpits. Hold the posture very still while breathing calmly, so that when you release it your elevated heart rate will send a boost of high-speed circulation to those areas. Notice a white mark on your thigh after you come out of Eagle? That's a good indicator that you’ve been maintaining a strong compression.
Using leverage to promote good alignment and open joints.
When you move your knees to the right and upper body to the left to get your feet, knees, elbows and hands in one line, you are using the leverage of one limb against to create the compression effect I mentioned above and open up your major joints. The key to not falling over while you make these adjustment is keeping your (especially lower) abdominal muscles tight and your upper body lifted away from your thighs.
Many beginners tend to lean or even hunch their bodies forward while they're setting up their Eagle, in an effort to pull their elbows down. Don't let this happen to you! Keep your upper body (when you hear the cue "upper body" in class, think mainly lower ribs upward) leaning back throughout the posture, which means (although you'll end up looking straight ahead) your spine is actually in a backward bending position. This position strengthens back and core muscles, releases tension in your lumbar spine, and compresses the kidneys.
If you can't move your knees right and upper body left, you might be sitting down too low. Try coming up a little bit and try again!
Turning your thumbs toward your face and little fingers toward the mirror will help you straighten out the wrists.
Don't fret if your elbows don't ever go below your nose. It's the intention of pulling your elbows down that gives you that amazing stretch in the shoulders, which is the whole point to this instruction.