Polio, which is sometimes referred to as poliomyelitis, is caused by an acute virus that attacks the anterior horn cells of lower motor neurons (Birk, 1997). These motor neurons are located in the front part of the spinal cord and are essential for muscle activity. The extent of motor neuron damage and the progression of the disease varies considerably in individuals with post-polio syndrome, and depends on which muscle groups were affected and how much damage was sustained during the acute stages of the disease (Nollett & Beelen, 1999).
Post-polio syndrome occurs several decades after the onset of polio. Approximately, 25 percent of individuals who contracted the polio virus during the 1940s, and 1950s report late-onset symptoms in their 40s and 50s (Pauls & Reed, 1996). Although polio has become quite rare in this country after the discovery of the Salk vaccine, persons who were born in the 1940s and 1950s are now in their 50s and 60s and are starting to experience significant mobility limitations. Common symptoms associated with post-polio syndrome include: (a) fatigue, generally described as a feeling of extreme exhaustion after minimal activities; (b) decreased endurance, which is manifested by the inability to sustain general activity; (c) new joint and muscle pain; (d) progressive weakness in muscles both affected by the polio and new muscle weakness; (e) respiratory insufficiency, which often requires ventilator support; and (e) cold intolerance that contributes to muscle weakness (Jones, Speier, Canine, Owen, & Stull, 1989).
There is some debate concerning whether or not persons with post-polio syndrome should perform resistance training exercise (Birk, 1997). Since progressive weakness is a hallmark sign of post-polio syndrome in the later years, the theory is that excessive exercise can cause an accelerated loss in function. In a recent study on resistance training in persons with post-polio syndrome, Agre, Rodriquez and Franke (1997) examined the effects of a combined program of dynamic and isometric muscle strengthening exercises in 7 individuals with post-polio syndrome and concluded that muscle strength can be significantly increased without causing adverse effects on neurological function. Although, there are few well-controlled studies on resistance training in persons with post-polio syndrome (Birk, 1997), most experts agree that not performing muscle strengthening exercises will result in a loss in function as the person ages.
Resistance Training Guidelines
1. Many polio survivors complain of new musculoskeletal pain as they grow older (Birk, 1997). The most common complaints are difficulty walking and stair climbing. This may be related to a progressive loss of muscle strength (Agre et al., 1997). The fitness instructor must understand that post-polio is a progressive disorder that may result in weakness as the person ages. In order to determine if a resistance training program should be maintained, reduced, or eliminated, it is important to communicate with the client's physician or other qualified health professional. The medical advisor should be able to determine if the program should be modified or stopped in a person who is complaining of pain or fatigue. High-intensity resistance exercise is not recommended for persons with postpolio syndrome, since it is not known if this type of exercise can cause permanent loss of function (Birk, 1997).
2. Although resistance training should be part of an exercise program for persons with post-polio syndrome, it is extremely important to keep muscle fatigue to a minimum. Overworking affected muscle groups could result in fatigue and decreased muscle function. The development of strength in persons with post-polio syndrome must be carefully monitored to assure that the program is not compromising the person's health. The fitness instructor should monitor the client closely for any signs of pain, discomfort or fatigue resulting from the program.
3. Begin with minimal resistance and progress slowly. Stay within the client's comfort level. The more deconditioned the client is, the greater the importance on preventing fatigue by starting with very light resistance. If pain or fatigue is present, switch to cardiovascular and flexibility training until it subsides.
4. Since post-polio syndrome often results in asymmetrical muscle weakness, the fitness instructor should evaluate each limb separately. The instructor should document the training protocol and determine if any new muscle weakness is associated with other aging-related changes or the resistance training program. If there is a sudden loss of function or enhanced pain or fatigue resulting from the activity, ask the client to contact his or her physician or health provider to determine if the exercise program should be modified or discontinued.