Revolved Lunge
How to do it
Step the right foot forward into a lunge, knee stacked over the ankle, left leg long behind with the knee resting on the floor. Bring the palms together in front of the chest and lengthen up through the spine. Rotate the chest toward the right leg and hook the left elbow outside the right knee, turning from the ribs rather than pulling with the arm. Keep the back leg long and heavy. To go deeper, lift the back knee off the floor, take the bottom hand to a block or the floor outside the front foot, and reach the top arm to the ceiling. Hold and breathe, then switch sides.
Why it's good for runners
Almost everything that rotates in this method happens lying down or kneeling. This is standing rotation under load, which is what running and swimming actually ask for — the trunk resisting and returning rotation while the legs are working. It is also the only shape that combines back-leg hip extension with a spinal twist, so a body that sits at ninety degrees all day gets the front of the hip opened and the mid-back turned in the same breath.
It is built on the lunge you already do every morning, so there is one new instruction on top of a position you know rather than a new shape to learn.
Common mistakes
Don't crank on the elbow. Levering against the knee turns a rotation into a shoulder shove and the spine stops moving. Don't let the back hip swing forward to buy an extra few degrees of turn — the twist is above the pelvis, and a hip that rotates with you is a hip that got out of the work. And don't chase the full version with the back knee lifted before the supported one is comfortable; knee down is the pose, not a lesser copy of it.