Exercise intolerance and reduced health status have been found in patients with sarcoidosis and has been related to skeletal muscle weakness. The present researchers reason that skeletal muscle weakness is, at least in part, related to physical inactivity and therefore partially reversible following a structured exercise training program. Nevertheless, the effects of exercise training have never been studied in patients with sarcoidosis. Therefore, the present study is undertaken to explore the effects of exercise training in patients with sarcoidosis. A priori, the following hypotheses are formulated:

• A 12-week exercise training program improves health status, quality of life and exercise capacity in patients with sarcoidosis as compared to sarcoidosis patients without exercise intervention.
• A 12-week exercise training program improves skeletal muscle function and reduces complaints of anxiety and depression in patients with sarcoidosis as compared to sarcoidosis patients without exercise intervention.
• A 12-week exercise training program reduces circulating levels of inflammatory markers in patients with sarcoidosis as compared to sarcoidosis patients without exercise intervention.

The EXTRAS study is a prospective, randomized, controlled, 24-week crossover clinical trial in which the participants are randomly assigned to receive 12 weeks of dynamic resistance and whole-body endurance exercises followed by 12 weeks without intervention or vice versa. Consenting participants will be assessed at baseline (before randomization, week 0) and at weeks 12 and 24.

Inclusion Criteria:

• Main diagnosis: previously diagnosed sarcoidosis according to the latest ATS/ERS/WASOG statement on sarcoidosis (AJRCCM 1999)

Exclusion Criteria:

• A history of neurosarcoidosis
• Undergoing structured exercise training at the time of enrollment or in the preceding 6 months
• Current participation in a pharmacological study
• Cardiovascular abnormalities on the ECG during baseline peak exercise test
• A 'normal' baseline peak oxygen uptake (≥90% of the predicted values) in combination with a 'normal' quadriceps peak torque or distance walked in 6 minutes