Most people in our Western society, who tend to be sat at a desk or standing lazily, round their shoulders forward, when the shoulders should be drawn back together, and this causes tension and pain in the shoulders and neck over time. This will also usually mean the pectoral (chest) muscles are tight and drawing the shoulders even further forward and round!
A tight or short pectoralis minor muscle can inhibit the lower trapezius from doing its job properly. Lower trapezius muscle strengthening exercise strengthens the lower trapezius weak phasic muscles, and reduces the overly tonic (toned) pectoralis muscles; and it decreases the imbalances in scapulothoracic muscles and increases stabilisation in the neck and scapula to help lengthen the pectorals muscles and improve neck and shoulder pain and dysfunction levels.
You can test if you have weak lower trapezius muscles by doing Wall Angels; below is how you do it:
Stand with feet approximately 12" from the wall.
Place your lower back flat on the wall and work the entire spine up to be flat.
Place your head against the wall and perform a mild to moderate chin tuck.
Next, bring arms to a T with elbows bent 90 degrees.
Rotate your shoulders and forearms backwards until your forearm and hands are against or near the wall.
While maintaining hands against the wall, slowly raise your hands straight up. (If your forearms and hands come off the wall, that is your end point for now and your sign that you may have a mobility or strength deficit).
After performing that test, what did you feel? If you simply felt tightness in your chest or thoracic spine, you may be getting a false positive. To avoid that, do some stretching and try the test again. However, if you determine that mobility is not your issue and you're still getting a positive test result (forearms and hands come off the wall), you may very well have a strength deficit in the lower traps.
If so, you can even turn this Wall Angel into an exercise to strengthen the back body and improve the strength of your lower trapezius!
You can also practice Locust Yoga pose, as pictured below. It is safer if you are practising a Yoga posture for the first time that you do it with a trained Yoga teacher, before you start to do it yourself. Make sure you warm up your body, specifically your spine and shoulders, before you do this posture.
Happy practising! Remember to keep your shoulder blades drawing back towards each other in day to day life and you will improve your posture and reduce your shoulder and neck pain!!