ABSTRACT
Skeletal muscle dysfunction is a frequent systemic manifestation affecting more than 40% of patients with chronic respiratory conditions. Muscle dysfunction and wasting of the lower limbs has been shown to be a significant contributor to disease morbidity and mortality, regardless of the functional impairment of the lungs. The main cause for this systemic manifestation is type I fibre atrophy because of chronic disuse of the locomotor, and to a lesser extent of the upper limb muscles due to dyspnoea. Other potential contributing factors are enhanced oxidative stress, nutritional depletion, hypoxia, hypercarbia and vitamin deficits that may add a ‘myopathic’ component to the atrophic main substrate. From the clinical point of view, peripheral muscles can be evaluated by two different approaches: their mass or thickness and their function, specifically their force-generating and endurance properties. Skeletal muscle dysfunction can be improved with relatively simple interventions such as exercise training, electrical stimulation and nutrition and in certain cases with anabolic corticosteroids. Novel molecules specifically targeting molecular pathways that are responsible for the loss of muscle mass or function are being developed with promising results.
