• The six-minute walking distance [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  

• Cycloergometer test: maximum power, maximum oxygen consumption, minute ventilation [ Time Frame: 1 month ] [ Designated as safety issue: No ]
  
• Inspiratory reserve volume (IRV), gasometry, dyspnea score [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  
• Measurement of voluntary maximum force and non cooperative force of the quadriceps [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  
• Area of quadriceps cross section measured with a scanner [ Time Frame: 1, 2 months ] [ Designated as safety issue: No ]
  
• Quadriceps muscle mass [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  
• Quality of life: CFQ14, BDI-TDI questionnaires [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  
• Compliance with ergocycle rehabilitation [ Time Frame: 1 month ] [ Designated as safety issue: No ]
  
• HOMA and QUICKI tests [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  
• Spirometry [ Time Frame: 0, 1, 2 months ] [ Designated as safety issue: No ]
  

Cystic fibrosis is an autosomal recessive genetic disease due to a mutation of the CFTR protein gene. The CFTR protein transports chloride ions (Cl-) across cell membranes in the lungs, pancreas, digestive tract, reproductive tract, and skin.

CFTR mutation mainly leads to a dysfunction of the pulmonary system and pancreas exocrine function.

Several studies showed that cystic fibrosis commonly induces a reduction of effort tolerance, peripheral muscular strength and work capacity.

Patients suffering from cystic fibrosis with a high endurance capacity have a lower risk of poor prognosis. Those with a severe dyspnea have a higher benefit with a force training or a combined force and endurance training than with endurance training alone.

We propose to study the effect of a quadriceps electrostimulation program, performed prior to an endurance retraining program using a cycloergometer, in patients with cystic fibrosis associated with severe pulmonary dysfunction, to enhance their muscular performance and increase their adherence to the cycloergometer retraining program.

This is a randomized trial with two groups:

Group A: experimental group, twenty patients. Six weeks with electrostimulation program followed by six weeks under a cycloergometer program.

Group B: control group, twenty patients. Six weeks with their usual physical activity followed by six weeks with a cycloergometer program.

The Randomization is stratified on expiratory volume per second. The size of randomization blocks is random because of the open design.