Overload and overuse are the 2 leading causes for the cord like structure (Rotator Cuff tendon) to become inflamed. Incorrect biomechanics (the way your shoulder moves), fatigue or simply weakness are the factors that cause narrowing of small space at the top of your shoulder. This causes compression on the tendons and leads to pain and inflammation – in other words rotator cuff impingement.
Too much load or too many repetitions out of the blue overload your tendons, like swimming 100 laps or doing 100 burpees if you’re used to 50 or even something like hanging 10 loads of washing on the line. Sudden overload leads to minor tears in the muscles. This in turn causes swelling in the subacromial space (big word for the space between the shoulder blade at the top of your shoulder where the tendon goes through to the head of the humerus). Hence there will be less space for the tendons to move and shoulder movements will be painful.
Repetitive over-head throwing actions in ball sports causes the Rotator Cutt tendons to compress. Consequently this leads to pain and inflammation of the tendons.
Repetitive poor movements is another main cause of Rotator Cuff Tendinitis, for example in swimmers. As fatigue sets in with overtraining, the quality of movements will decrease and lead to pain and inflammation. The end result is Rotator Cuff tendinitis and possibly a Rotator Cuff tear if you don’t manage the training load on your shoulder.
Haven’t we all tried to paint our own house, whether that is the bathroom roof or the outside wall? The next morning you are very aware of your shoulders and neck being stiff and tight. Although it is not defined as a professional sport yet, it can still be the cause of your Rotator Cuff tendonitis. This time around it is a sudden overload of your Rotator Cuff muscles, seeing as you normally do not use the arm in that position, that will cause you to have pain and inflammation.