Statistical analysis Sample size The applied calculations are performed on 55 patients on the basis of VO2peak; through six weeks of training 55 patients achieved an increase of 0.85 ml / kg / min in VO2peak (SD = 2,48). It is assumed that the control group in the current study will have a reduction of 0.5 ml / kg / min for VO2peak (SD = 2.48). Assumptions for calculation of patient numbers are as follows: Type 1 error 0.05, type 2 error 0.20, and success level 1.35, SD 2.48. This leads to a total number of patients of 108 (54 in each arm). This study expects a drop-out rate of 50% and therefore another 108 patients must be included, which gives a sample size of 216 patients.