Peripheral Muscle Function in Patients With COPD

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airway obstruction and progressive deterioration of respiratory function. Patients with COPD show a limited exercise tolerance, early fatigability and progressive dyspnea, with important consequences on the ability to sustain even mild efforts and a drastic restriction in the activities of daily living. Muscle dysfunction is a systemic manifestation of COPD that contributes to exertion intolerance in individuals with COPD to the point of compromising fundamental functional activities, such as walking. Previous studies have shown, in fact, that quadriceps strength can be reduced by 20% to 30% in patients with COPD and this value is associated with an increased risk of mortality in patients with lower strength levels. In addition, loss of muscle mass or sarcopenia also occurs with a prevalence of between 8% and 67% in patients with COPD, exacerbating the picture of muscle dysfunction. One of the goals of respiratory rehabilitation is precisely the prevention of muscle dysfunction in patients with COPD. However, rehabilitation programs aimed at maintaining and recovering muscle strength are often lacking in guidance regarding target muscles, duration of sessions, and training intensity, while strength assessment is often limited by the timing and resources associated with the clinical setting in which it takes place. This makes it difficult to determine its short- and long-term effectiveness. Therefore, assessment of muscle function in patients with COPD requires tests that are simple and quick to perform, but equally capable of providing quantitative data referable to a specific characteristic of muscle strength as well as indicative of the patient's overall function. In addition, complementary measurements such as body composition and muscle mass, as well as the development of predictive models and normative values of muscle function could provide additional information on the progression