The supine latissimus dorsi stretch improves shoulder range-of-motion, leading to improved ease with overhead reaching activities. Because you need to engage your lower abdominal muscles to perform this exercise properly, this exercise can also help you improve activation of your lower abdominal muscles.
Get into a comfortable position lying on your back with your knees bent up and your feet flat. Your hands should be lying next to your sides with your thumbs pointing up to the ceiling.
Slowly lift both arms up overhead as far as you can without any discomfort in your shoulders. Allow the weight of gravity to stretch your shoulder muscles. Hold the end position for up to 30 seconds. Slowly bring your arms back down to the starting position.