There are many ways to work with this posture to gain long term health benefits. Here are some of them!
This posture is used within the Sun Sequence and also as a great body preparation for the illiopsoas muscle for postures like the Lord of the Dance (Natarajasana ), the Camel and the Bow.
Dru Sun Salute
Come into the extended runner position (see image) and fold your upper body over the thigh, then as you breathe in engage your core stability and begin to raise the torso to vertical as the arms float up to about shoulder height in front of you. See if you can focus on uncurling the spine as you raise up and with the out breath, roll the spine forwards as you bring the body back to the thigh. Allow the arms to follow the body as you come forwards and down, then sweep them past the hips and up into the air behind you into the 'flight' posture. Repeat this movement a few more times. Allow the arms to raise progressively higher until they reach overhead, and if you feel comfortable, a little beyond the head so you get a great back bend - please engage your core stability muscles and gluteals, especially with the back bend to protect your back.
From the start position above sweep the arms to the side and forwards and deepen the stretch into the front knee. Turn the palms to face upwards and then pull the elbows and hands back and in towards the waist. As an addition to this movement you can also straighten the front leg as you bring the hands to the waist, then bend deeply into the front knee as the arms sweep round and out in front. Repeat several times to either side.
Energy Block Release 3 - The Thunderbolt
We use the Extended Runner in EBR 3 in the movement we call the Thunderbolt. From the start position above roll the body forwards over the thigh, hands either side of the feet. If your right leg is back, take the right hand back towards your right hip (or if left leg back draw the left hand back). Then circle the arm up and behind you till it is at the vertical with you looking to the side of your body. With a quick out breath turn the hips and body, shoulders and arm to face forward and diagonally over the front leg. The arm, torso and thigh of the back leg should all now be in alignment. Relax the body forward and down. Repeat a few times on this side to open the lungs, mobilise the shoulder joint and stretch through the back hip.