Tree Pose or Vriksasana is the Sanskrit name comes from the words vrksa meaning tree, and asana meaning pose. The Tree Pose strengthens and tones the leg muscles, ankles and feet as well as the groin, inner thigh.
If it is too difficult to straighten your arms above your head, then you can use a leather belt. Make a loop with the belt and slide it around your arms right above the elbow joints. Tighten the belt so that your arms cannot move further than shoulder-width apart from each other. Then lift your arms above your head.