Inclusion Criteria:
COPD patients :
* GOLD II - III or IV
* FEV1 \<80% of predicted values
* Men and women aged 40 years and over
* French-speaking participant
* BMI \<30 kg / m²
* Stable condition (i.e. without exacerbation) for more than 15 days
* Able to express their consent in writing prior to any participation in the study
* Affiliates or beneficiaries of a social security
* Minimum score of 26 on the MMSE questionnaire of 3 months or less
Healthy volunteers :
* Men and women aged 40 years and over
* French-speaking participant
* BMI \<30 kg / m²
* No known chronic respiratory, cardiovascular, metabolic, renal or neuromuscular pathologies
* Able to express their consent in writing prior to any participation in the study
* Affiliates or beneficiaries of a social security
* Minimum score of 26 on the MMSE questionnaire of 3 months or less
For all participants :
-Subject who has not objected to the reuse of data collected
Exclusion Criteria:
* COPD patients :
* Alcoholism, i.e. \> 21 glasses a week for men and \>14 glasses a week for women
* Psychiatric pathologies or antecedent of behavioral disorders
* Patients treated with oral or systemic corticosteroids (\> 0.5 mg / kg / day for \> 7 days)
* Contraindication to the application of a magnetic field (i.e. right hip arthroplasty, pelvic / abdominal surgeries)
* Severe vision or hearing problems not corrected
* Patient oxygen dependent
* Patients in exclusion period from another research protocol
* Pregnant women (known pregnancy) or lactating women
* Patient deprived of liberty by a judicial or administrative decision
* Patient subject to a legal protection measure or unable to express their consent
* Patient who is not sufficiently fluent in reading and understanding the French language to be able to consent to participate in the study
* Patient unable to follow study procedures and to respect visits throughout the study period
* Person with a medical history that, in the opinion of the investigator, could interfere with the results of the study
* Any condition that, in the opinion of the investigator, could increase and compromise the safety of the person in the event that he / she participates in the study
* Any other reason that, in the opinion of the investigator, could interfere with the evaluation of the aims of the study
Healthy volunteers:
* Alcoholism, i.e. \> 21 glasses a week for men and \>14 glasses a week for women
* Psychiatric pathologies or antecedent of behavioral disorders
* Patients treated with oral or systemic corticosteroids (\> 0.5 mg / kg / day for \> 7 days)
* Contraindication to the application of a magnetic field (i.e. right hip arthroplasty, pelvic / abdominal surgeries)
* Severe vision or hearing problems not corrected
* Subjects in exclusion period from another research protocol
* Pregnant women (known pregnancy) or lactating women
* Regular physical activity with a frequency greater than 3 sessions per week
* Participant deprived of liberty by a judicial or administrative decision
* Participant subject to a legal protection measure or unable to express their consent
* Participant who is not sufficiently fluent in reading and understanding the French language to be able to consent to participate in the study
* Participant unable to follow study procedures and to respect visits throughout the study period
* Person with a medical history that, in the opinion of the investigator, could interfere with the results of the study
* Any condition that, in the opinion of the investigator, could increase and compromise the safety of the person in the event that he / she participates in the study
* Any other reason that, in the opinion of the investigator, could interfere with the evaluation of the aims of the study