Too much stress -- or too many fastballs -- can cause partial tears and swelling in the tendons of the rotator cuff. Abrupt stress may even cause one of the tendons to pull away from the bone or tear in the middle of the tendon.o diagnose a rotator cuff tear, your doctor will give you a thorough physical exam. He or she will want you to move your arm in different directions to see what causes pain. In addition, your doctor might want to order the following tests: 1  X-ray of the shoulder with some special views.
In rare cases, generalized muscle weakness may be caused by another health problem, such as: 1  A problem with the minerals (electrolytes) found naturally in the body, such as low levels of potassium or sodium. 2  Infections, such as a urinary tract infection or a respiratory infection.
Muscle atrophy, often seen in people in wheelchairs, can lead to leg weakness. The power and ability to move one's legs stems from the interaction of two processes. These are the nerve signal that is sent to the muscles from the brain and passes via the spinal cord, and the muscle's intrinsic power to contract. Any interruption in this pathway in the lower limb can result in leg weakness. As such, leg weakness can be caused by a muscle disease or a nerve disease.