This low-lunge like pose is great for opening the hip flexors. If you have tight hips as many riders do, there are several complimentary poses such as pigeon and butterfly that can work the hips open. Having full range of motion in this area allows riders to maintain better position while cornering and avoid fatigue and groin injuries.
To start, move into high lunge position with forward knee above ankle, rear knee can be on the ground for an easier stretch, or lifted for a more advanced position.
The same arm as the forward leg moves under the knee and rests outside the foot. Ensure the knee stays above the ankle, a common mistake is to allow it to open to the outside which can cause injury.