Both of them is the right answer but not in that order. It also depends on how much damage you have done to it. Most tears will get better with just rest and exercise but any serious partial tear or full tear may require corrective before any therapy will help.
What is important with any type of torn rotator cuff treatment is to rest the muscle and let the injury begin to heal. Carrying on through the pain of a rotator cuff is likely to leave you needing surgery as you do more damage to the muscles, so rest is the first thing that you need to do.
Along with rest, you need to reduce the inflammation before you can think about starting any form of exercise. The rotator cuff is a group of muscles that help to stabilise the shoulder joint by pulling the head of the humerus into the socket of the shoulder. They are small but vital muscles that surround the shoulder joint forming a cuff of muscle that helps to support it, in doing so they run over and sometimes under the shoulder bones.
Any inflammation to these muscles can cause pain as the inflamed tendon can catch or impinge on bone. A classic example of this is the supraspinatus muscle which runs under the collar bone and the acromion of the shoulder blade. When this muscle become inflamed it can catch on the channel of bone and start to fray. Worst case scenario is that you could end up with a snapped tendon that would leave you needing shoulder surgery.
So you must let the muscles rest. This means avoiding any of the movements that are painful. If your job includes a lot of overhead movement you may need to modify how you work. If you spend the day sitting at a desk, you might need to rearrange your desk to avoid reaching or stretching movements with the damaged arm. It might even be necessary to take a few days off to rest the arm properly.
At the same times start to reduce the inflammation. This could be by using non-steroidal anti-inflammatory drugs such as Ibuprofen and by using ice packs on the damaged muscle to help to bring down the swelling. If symptoms persist you may need to have a cortisone injection into the muscle to combat the inflammation. Your doctor should be able to do this for you.
Once the muscle has begun to settle down you can begin simple exercises aimed at strengthening your rotator cuff muscles. Don’t go rushing to the gym thinking that any kind of exercise will do the trick. It won’t. Using weights before the muscle has healed properly is likely to cause more damage.
Rotator cuff exercises use little or no resistance when recovering from an injury. They will begin with gentle exercises that do not cause any pain. If you feel pain or discomfort when exercising stop immediately as this is an indication of further damage being done. It may be that you started exercising too soon.
And don’t forget, when your shoulder is fixed and back to its full pain free movement, don’t just give up on the exercises. Rotator cuff injuries are common but most of them can be avoided by keeping the rotator cuff muscles healthy so just take five or ten minutes a day to keep them happy.