Individuals may experience weakness for different reasons. For people with MS, demyelination interrupts the flow of nerve impulses in the spinal cord or (less frequently) in the brain that keep a muscle or group of muscles functioning properly. As a result, muscles lose strength.
The management of this type of weakness is different from the management of weakness caused by inactivity, called “disuse weakness.” With the latter, a person may increase muscle strength by performing progressive resistance exercises through lifting weights. When demyelination is to blame, lifting weights or doing other repetitive exercise until tiring, strength will be further reduced – resulting in more weakness.
Should individuals with MS who are experiencing weakness perform any exercise? Absolutely, but seeing a physical therapist – one who is experienced with MS and muscle weakness caused by changes in nerve flow – is vital. While resistance exercise can worsen the problem, not using a muscle at all will result in disuse weakness or atrophy. This is seen when someone wears a cast for a period of time – the muscle shrinks while unable to exercise. A physical therapist can develop an exercise plan to keep muscles active without increasing weakness.
Other symptoms of MS and their treatments can also be involved with weakness. For instance, when taking medications for spasticity (muscle tightness), a muscle can become stronger as it relaxes and uses less energy when moving. But if too much of a spasticity medication is taken, it can have the opposite effect of increasing weakness. A doctor should also test for other conditions that can cause weakness, such as diabetes, infection, or depression.
One other important strategy to reducing muscle weakness is to be conscious of any wasted energy. Planning ahead and reserving energy for your most important or enjoyable activities during the day will enable you to have the most strength when needed. Using assistive equipment that provides support and conserves energy can be of great help in managing weakness. Treating fatigue can also help to reduce weakness, and some people may benefit from taking Ampyra® (dalfampridine), a medication approved to increase walking speed in MS.