This posture is a part of Surya Namaskaras or Sun Salutations or can be done on its own. It is a strength pose that challenges both the upper body and the core. In Surya Namaskara, we lift from Chaturanga up into Urdhva Mukha Svanasana or Upward Facing Dog.
Start in plank pose or Phalakasana, making sure your elbows are directly above your wrists. Bring your body weight slightly forward by rocking up onto your toes. Maintain a straight line from the heels to the crown of the head throughout the pose. Keep your elbows in toward the torso through the entire posture. On an exhale lower your body down until your elbows are bent at a right angle but still aligned above the wrists. Dropping below a 90 degree angle in the elbow will put pressure on the shoulder complex. Remember this is not a push up.
Drishti or gaze is down at the ground. Keep the shoulders back away from the ears and the abdominal and thigh muscles engaged. If the full Chaturanga Dandasana is too challenging, begin with the modification of knees on the ground. The same alignment is possible with the knees down, but this variation takes some of the body weight out of the arms. The knees on the ground option is also a great way to master the alignment and protect the shoulder complex.