Neuromuscular Fatigue in Chronic Obstructive Pulonary Disease

Fatigue is a prevalent symptom in Chronic Obstructive Pulmonary Disease (COPD) that limits patients in their daily living activities. It is now well established that COPD patients may have altered neuromuscular functions compared to healthy individuals. However, the different studies conducted on muscle fatigue in COPD have been done independently of any cognitive solicitation, yet present in most of daily living activities. Therefore, the aim of this research is to evaluate the impact of the disease on neuromuscular fatigue during dual-task situation (simultaneous accomplishment of a muscle contraction and a cognitive task). A better understanding of fatigue in COPD will promote the development of new perspectives in patient management.

The hypothesis is that COPD patients will exhibit increased fatigue level (compared to healthy subjects), particularly during dual-task situation. It is assumed that the higher negative effect associated with the dual-task will be related to different neurophysiological mechanisms (i.e., neuromuscular fatigue, autonomic nervous system activity, mental fatigue).

This study will include three experimental sessions for both COPD patients and healthy participants. These experimental sessions will be performed on three separate days. Each session will last between 1.5 and 2 hours.

The first session will correspond to a familiarization session with the different tests that will be performed during the two next sessions. During this first session, different functional tests will be also performed : 1-minute sit-to-stand tests and postural tests, with and without a concomitant cognitive task.

The second and third sessions will correspond to experimental sessions during which the participants will accomplish a fatiguing task in single or dual-task situation (randomized order). The cognitive task will be a memory cognitive task, called n-back task. The fatiguing tasks will involve submaximal isometric contractions of the knee extensors performed until task failure. The neuromuscular fatigue will be evaluated regularly during the fatiguing tasks (i.e. about each minute) using the magnetic stimulation of the femoral nerve in order to assess to central and peripheral determinants of the neuromuscular fatigue. Moreover, the autonomic nervous system activity (via cardiac recordings), perceived exertion and cognitive performance (in dual-task situation) will be continuously recorded during the fatiguing tasks. Before and after each fatiguing tasks, several questionnaires will be completed (i.e. mood, motivation, subjective workload) in order to evaluate the psychological determinants of performance.

Eligibility Criteria:
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

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