The Effect of Adding Whole-Body Vibration Exercises to Home Exercise Program on Muscle Strength in Patients With Postpolio Syndrome

Post-polio syndrome (PPS) is a neurological disease that affects polio survivors at least 15 years after the initial polio infection. The description of PPS is attributed to Jean-Martin Charcot in 1875 but was only widely recognized in the early 1980s [1].

PPS is characterized by new neurological deficiencies after a period of neurological stability, especially at least 1 decade after the initial infection. PPS may manifest as new, persistent, and progressive muscle weakness, atrophy, limb fatigability, myalgia, arthralgia, and dysphagia, but also as generalized fatigue, which typically has a considerable impact on the patients' quality of life. The estimates of the percentage of polio patients affected by PPS are inconsistent, varying between 20 and 85% depending on the diagnostic criteria applied [1].

Despite its prevalence, post-polio syndrome remains surprisingly under-researched. People with PPS generally have fewer options for exercise because it may exacerbate PPS symptoms such as pain, fatigue, and muscle weakness [2].

The pathophysiological framework relating to the genesis of PPS is based on the theory of super training, considering that shortly after an episode of acute poliomyelitis, the remaining motor neurons increase the number of sprouts for the reinnervation of muscle fibers after they have been denervated. About two to three decades after the acute episode, there is a tendency to overload this system, that can be accelerated depending on individual factors especially the activities and exercises carried out that promote overuse of the affected muscles. In this case of overuse and super training, an intense metabolic demand in the residual motor units occurs, which then triggers a process of secondary neuronal death, and active inflammatory process is present in the spinal cord with increased level of cytokines in the cerebrospinal fluid but without any convincing evidence of viral reactivation. Another hypothesis for the genesis of PPS is that it results from an autoimmune disorder, a theory that is reinforced by the presence of anti-neurofilament antibodies in the cerebrospinal fluid [1, 3, 4].

There is an ongoing process of denervation and reinnervation in the muscle fibers of motor units that survived in PPS patients. Excessive physical activity accelerates the loss of motor units. Therefore, it is very important to plan the exercise so as not to cause additional harmful effects on the integrity of the muscle and survived motor units, to ensure maximal improvement and to prevent overload.