This is a stretch to help improve your shoulder capsule and internal rotation. Start by lying on your side with your legs piked and your head resting on a block. Ensure your scapula or should blade is flat on the mat. With the elbow bent and keeping the shoulder at less than 90 degrees rotate the shoulder down towards the ground and hold for 1-2 minutes with deep breathing. After the stretch try and push your arm into your hand lightly at 20% this is your PAILs contraction, ramp up the contraction between 30%-max depending on your level. Hold for 10 - 15 seconds and then try to rotate the arm down away from the hand, this is your RAILs contraction. Ramp up slowly and hold for 10-15 seconds. When you release the RAILs contraction you should see a 15 degree increase in your range of motion. You can hold in this new ROM for another 30 seconds and then repeat PAILs and RAILs contractions to improve mobility further.