The weaker the muscle, the less frequently it should be used. If you do not have strong enough muscles for normal activities you cannot do the same activities as people with normal muscle. You modify your lifestyle and remove the strain. Stop doing heavy tasks. Look at the number of activities you have per day.
Many people feel better with fewer activities.
So you have to make your lifestyle match your muscle strength. The recommendation is to reduce body weight by re-educating your taste buds. Dr. Perry compares this to visiting a new country and learning to eat new food. The shoulder is the most mobile joint in the body. Polio patients activate twice as much of the muscle as a normal person to lift up an arm, so the muscle has less rest and fatigues more easily.