I am not sure the traditional name of this pose, but we call it spinal balance or opposite hand and leg. This pose strengthens the back asymmetrically and uses the core (abdominals) for support. Always build your poses by breathing deeply. Once you have established your breathing practice, follow the directions below.
Begin on hands and knees.
Lift up your right leg and turn the toes down toward the floor.
Raise your left arm and extend it forward. Turn palm of the hand toward the center of the body.
Stretch through the heel of the raised leg and fingers of extended arm.
Change sides after a few breaths.
Modifications: Practice with the toes of the extended leg on the floor or practice without lifting the front arm.
For an additional challenge: You can bring the extended arm and leg out to the side for awkward airplane. It really strengthens the core and gets you warmed up quickly.