Diaphragm paralysis is a possible complication of cardiac surgery. The spontaneous recovery of the diaphragm mobility is slow and partial or absent in most cases. We hypothesize that a program of diaphragm muscle training by means of the Threshold variable resistance device could improve the rate of complete diaphragm mobility recovery in a shorter time period. Patient with post-cardiosurgical diaphragm paralysis will be random assigned to the specific training protocol or to a generic non-training physical activity.