The management of new weakness in a post-polio patient can include a
strengthening exercise program, an aerobic exercise program, stretching to
decrease or prevent contractures, avoidance of muscular overuse (exercising to
the point of muscle pain and fatigue), bracing, and use of assistive devices. |
Exercise in post-polio patients has been a controversial topic for many years, primarily because of case reports of overwork weakness in these patients.[3,4] These clinical findings were supported by studies in denervated muscles of rats.[5-8] However, more recently, several studies have found that exercise can result in an increase in strength in post-polio patients many years after the acute illness. Feldman and Feldman and Soskolne were the first to report in more recent years a beneficial effect of an exercise program many years after APP. They treated 32 "PPS" muscles in six post-polio patients with an attenuated, "non-fatiguing," isotonic strengthening exercise program for at least 24 weeks, and found that 14 muscles improved in strength, 17 muscles maintained strength, and one muscle decreased in strength. However, the method of strength assessment and the changes in strength were not reported. Einarsson and Grimby and Einarsson studied the effects of a 6-week, three-times-per-week, isokinetic and isometric exercise program for the quadriceps muscles (3+ or better on manual muscle testing) in 12 post-polio patients. They found a mean increase of 29% in isometric strength and a mean increase of 24% in isokinetic strength. Muscle biopsy studies did not show a higher occurrence of histopathologic findings after training, although citrate synthase concentration increased non-significantly. Fillyaw and coworkers assessed the effect of a long-term (2-year), every-other-day, non-fatiguing, isotonic exercise program in 17 PPS patients. In each patient, one biceps muscle and one quadriceps muscle were randomly assigned to the exercise program. In 16 of 17 subjects, the maximum amount of weight a subject could lift 10 times increased by a mean of 77.7%. A significant increase of 8.4% in the maximum isometric torque occurred in the exercised muscles over the 2 years, whereas a non-significant change of --4.3% occurred in the non-exercised muscles. The authors concluded that PPS patients can benefit from a non-fatiguing, long-term exercise program, but that quantitative muscle strength testing should be performed at least every 3 months to prevent overwork weakness. Agre and coworkers have also assessed the effect of a 12-week isotonic and isometric home exercise program in seven post-polio patients. The maximum isometric strength (maximum voluntary contraction, MVC) significantly increased by 36%, endurance time at 40% MVC increased by 21%, and the tension time index increased by 18%. Fiber density, jitter, blocking, median macro-EMG amplitude, and creatine kinase did not change significantly with the exercise program.
In addition to strengthening exercise, aerobic exercise is also beneficial in post-polio patients. The effect of an aerobic exercise program on a bicycle ergometer was assessed in 37 post-polio patients by Jones and co-workers. They found that the average level of aerobic fitness in post-polio patients was 5.6 metabolic equivalents, similar to that seen in patients just after a myocardial infarction. Patients were assigned either to a 13- to 30-minute, three-times-per-week, 16-week exercise program, at up to 70% of maximum heart rate, or to no exercise. The exercised patients experienced significant increases in power attained during exercise, duration of exercise, maximum expired volume per unit time, and maximum oxygen consumption (VO2max). The non-exercising controls showed no improvement in these variables. The training effects in the exercising post-polio patients were similar to those observed in age-matched normals previously reported in the literature. Kriz and colleagues studied the effect of a 16-week, upper extremity aerobic exercise program (70% to 75% of heart rate reserve) on a cycle ergometer in 20 post-polio patients. Patients were randomly assigned either to the exercise program or to no exercise. The exercise group experienced a significant improvement compared with the non-exercise group with regard to oxygen consumption, carbon dioxide production, minute ventilation, power, and exercise time. The 19% improvement in cardiovascular fitness was similar to that previously reported in other populations. Dean and Ross also studied the effects of an aerobic exercise program in 20 post-polio patents who were randomly assigned to exercise on a horizontal treadmill or to no exercise. The training occurred three times per week for 6 weeks at 55% to 70% of age-predicted maximum heart rates. Trained subjects showed a significant improvement in economy or energy cost of walking, and thus walking duration, whereas the untrained subjects experienced no changes. No change was observed in cardio-respiratory conditioning.
In summary, exercise has been shown to be beneficial in post-polio patients, even in muscles where new weakness has been reported. The exact exercise prescription is dependent on a number of factors. Isometric exercise is most useful in muscles with less than grade 3 strength (Medical Research Council [MRC] Scale) or in muscles over a painful joint. An isotonic exercise program is most useful in muscles with grade 3 or better strength and without a painful joint. Isokinetic exercise can be used when equipment is available. An aerobic exercise program such as using a bicycle ergometer, walking, or swimming can also be useful, but preferably should be an activity that the patient enjoys in order to increase compliance. A warm-up and cool-down period with stretching exercises should also be included. Some patients may also benefit from more agressive stretching of contractures (if no contraindications exist), such as knee flexion contractures and ankle plantarflexion contractures to improve gait and stability. For the first few weeks, it is best for the patient to be monitored carefully (a few times per week), to ensure that the exercise prescription is being followed correctly and that overuse of muscles and joints does not occur. Once the patient understands the exercise program well, and demonstrates the ability to self-monitor, regular follow-up every few months is reasonable.
Even though several different types of exercise have been shown to be beneficial in the late post-polio patient, exercise should be used judiciously, and should be avoided completely in some patients. Muscle groups that are being overused may benefit from rest or supportive devices such as braces. Studies have not assessed the effect of exercise programs on patient function and general well-being, and the long-term effects of exercise in these patients are still unclear.
Overuse of muscles must be avoided in post-polio patients. In several case reports, muscle overuse in patients with past APP was thought to be the cause of increased weakness. This new weakness may be permanent. Perry and coworkers performed dynamic electromyography (in quadriceps, soleus, lower gluteus maximus, and long head of biceps femoris) during gait in 34 PPS patients, and found evidence of overuse (compared with normals). This occurred primarily in the biceps femoris (82%) and quadriceps (53%). The usefulness of creatine kinase (CK) levels in the monitoring of overuse in post-polio patients is unclear; however, Waring and McLaurin found a significant correlation between CK levels and distance walked during ambulatory activities in the previous 24 hours, indicating that CK could be a marker of overuse.
In addition, in one case report, CK was found to be markedly elevated in a post-polio patient with symptoms of weakness, fatigue, and pain. With a reduction in exercise, plasma CK levels decreased and symptoms resolved.
In a retrospective study of lower-extremity orthotic management for ambulation in 104 post-polio clinic patients, Waring and coworkers found that 78% of patients noted that appropriate orthotic prescription subjectively improved ability to walk, increased perceived walking safety, and reduced pain. Clark and co-workers have described some of the more common biomechanical deficits, and their orthotic management, in post-polio patients. These include inadequate dorsiflexion in swing, dorsiflexion collapse in stance, genu recurvatum (knee hyperextension), genu valgum (valgus deformity at the knee), and mediolateral ankle instability. In some patients, strengthening exercises may be tried first to control these deformities. If this is impossible, or not useful, orthoses may be used.
Inadequate dorsiflexion occurs secondary to weakness of ankle dorsiflexors and results in a foot drop and a tendency to fall or trip. This problem can be treated with an ankle-foot orthosis (AFO). Dorsiflexion collapse during stance can occur secondary to weak extensor muscles at the hips, knees, and ankles. This can be managed either with canes, crutches, or AFOs. Genu recurvatum in polio patients is most commonly caused by quadriceps weakness, and the resultant tendency of the patient to "lock" the knee to improve stability of the lower extremity. This deformity can cause pain and decreased efficiency of ambulation secondary to the increase in movement at the knee. In patients with mild weakness of the quadriceps, a knee orthosis or even AFO can be used to control the deformity; however, in patients with more severe weakness (MRC 3 or less), a knee-ankle-foot orthosis (KAFO) is necessary. Genu valgum deformity is usually caused by weakness of hip abductors, which causes the patient to lean laterally in stance phase to reduce the demand on this muscle group. This can also cause pain and increased energy expenditure with resultant decreased function. A KAFO with padded components on the proximal and medial tibia and distal femoral condyles is used to manage this deformity. Mediolateral ankle and subtalar joint instability is produced by weak or absent foot and ankle muscles. This can be treated with foot orthoses or an AFO. In addition to orthoses, other assistive devices that may be useful for post-polio patients to improve mobility and safety are canes, crutches, manual wheelchairs, electric wheelchairs, and motorized scooters.