Ask any of my clients and they have undoubtedly heard me talk about the psoas, a muscle deep inside the pelvis that connects to the lower spine and is a key stabilizer for the whole body. The latissimus dorsi, or the "lat" for short, is kind of the psoas of the upper body. It is the muscle that pulls your shoulders back and opens your chest—and it's commonly underdeveloped, helping contribute to our computer-related posture issues, including "text neck."
While well-meaning yoga and exercise instructors may tell us to "pull" our shoulders away from our ears, if the lats are not strong, this action can create unwanted tension in the neck and shoulders. Instead, I suggest a few simple exercises that, done regularly, will help you strengthen the lat, improve your posture, and relieve upper body pain.
To strengthen the lat, try a single arm row, which allow you to focus on one side of your lat muscle at a time. Choose a weight that you can perform at least eight repetitions with; don't do more than 12 repetitions. To perform a single-arm row, place your left knee and left hand onto the bench and place your right foot on the ground (or place your left elbow on your left knee, as in the illustration). Keep your back flat, hold the weight in your right arm, allow your right arm to hang toward the ground, lift your right hand upward until it is next to your chest, and lower your arm back down. After you complete the desired number of repetitions on the right side, switch to the left side.
The easiest way to stretch the lat is to lay flat on your back with legs bent, and let your arms fall to your sides in a "cactus" position (see video). Slowly raise your arms, keeping your elbows and hands in contact with the floor, then lower. Repeat eight or ten times.