Skeletal muscle dysfunction as a systemic consequence of chronic obstructive pulmonary disease (COPD) has a major impact on quality of life, health care resource utilization, and mortality of patients with this disease. In fact, a vicious circle of inactivity and disuse is established in the advanced stages of the disease, inducing a progressive decline in exercise tolerance and a loss of muscle mass (especially in locomotor muscles), resulting in the inability of patients to perform even the simplest daily activities.

In this context, the multidisciplinary rehabilitation approach includes not only recovery of exercise capacity but also training aimed at restoring muscle function in patients with COPD. However, there is considerable methodological variability among muscle resistance training programs used in clinical practice with patients with COPD. This is compounded by the need to identify alternative training strategies effective in inducing functional adaptation in skeletal muscle without increasing the degree of dyspnea or fatigue in those symptomatic patients with advanced stages of disease. Among these, eccentric exercise or negative work, i.e. the stretching of the muscle during the active contraction phase, represents a valid alternative to traditional concentric training in various rehabilitation contexts. The main advantages of this training method are: 1) eccentric contraction is able to produce greater forces than isometric and concentric contraction; 2) for the same resistance, eccentric contraction has a lower metabolic cost than concentric contraction. For these reasons, eccentric exercise is a valid method of muscle strengthening in rehabilitation and in particular in those subjects unable to sustain a high cardiorespiratory effort, as in the case of patients with moderate-severe COPD. Previous studies have also shown that eccentric exercise, even at low load, produces results equivalent if not superior to traditional training with respect to some particular characteristics of muscle function such as power and hypertrophy.

However, eccentric training programs for muscle dysfunction recovery in patients with COPD are underused in clinical practice, so far. In contrast, the so called iso-weight eccentric training, more suitable for clinical practice, could also be applied to rehabilitation programs designed for COPD patients.

The aim of this study is therefore to evaluate the reliability and efficacy of a low-load eccentric exercise training program compared to usual care for the improvement of muscle function in patients with COPD.

Inclusion Criteria:

• COPD diagnosis (GOLD stage: II-III-IV), defined as post-bronchodilator forced expiratory volume in 1s (FEV1)/forced vital capacity < 0.7 and FEV1 < 80% predicted.

Exclusion Criteria:

• Restrictive lung disease, unstable conditions, recent exacerbation, infection, embolism, pneumothorax, thoracic or abdominal surgery (less than 3 months before recruitment).
• Cardiologic conditions like myocardial infarction (less than 6 months before recruitment), heart failure, or severe angina.
• Inability of perform the exercise training (e.g. orthopaedic conditions).
• Incapability to understand the instructions required to carry out the tests and assessments planned.