Yoga term: Ashwa Sanchalasana
As you can see shoulders are over the knee and the knee is over the heel while the heel is being pushed into the ground with the hamstring and glute active. the leg reaching for the rear has the quads and shins active with the toes reaching towards the front of the room. The leg should be as straight as you can get it. The back of the leg is relaxed and being stretched while the glute is contracted. Keep the hips squared the front of the room. Chest also should be square and reaching to the front. Head is erect and gazing forward.