Within the scope of further subgroup analyses, a statistically significant improvement of the distance walked was found in 6-MWT with regard to comorbidities (COPD, arterial hypertension, chronic compensated heart failure, CHD/chronic atrial fibrillation) and to smoking behavior (data not shown). Chemotherapy performed prior to lung surgery did not influence 6-MWT and a statistically significant improvement of the walking distance at T1 and at T2 was observed in this subgroup as well (data not shown). Most likely due to the low number of subjects in the subgroups of radio- or radiochemotherapy, respectively (cf. Table 1), there was no significant difference between the distances walked at T1 and at T2 (data not shown).