Muscular endurance of upper (shoulder abduction, elbow and fingers bending) and lower (knee extension) limbs during isometric and maximal muscular contractions, keeped during 30 secondes will be measured by the difference of the force between the beggining and the end of the contraction

Modification of functional abilities in walking will be measured by the maximal distance of walking (in meter) during a 6-minutes walking test

Modification of functional abilities during transferts will be measured by the maximal number of transferts sitting to standing performed during a 1-minute chair lifts test

Clinical severity of the disease will be measured with the Newcastle Mitochondrial Disease Scale for Adults (NMDAS) and its 3 first sections. Score ranges from 0 to 145. The higher the score the more severe the disease.

Quality of life will be measured with the Quality of Life in Genetic Neuromuscular Disease Questionnaire (QOL-gNMD). The QoL-gNMD is splitted in 3 domains: "Impact of Physical Symptoms" (score from 0 to 19), "Self-perception" (score from 0 to 24) and "Activities and Social Participation" (score from 0 to 27).

The tiredness felt will be measured with the Fatigue Severity Scale (FSS). The FSS is a unidimensional scale which focuses on the physical aspects of fatigue. It is a self-reported questionnaire developed to measure the impact of disabling fatigue on daily functioning. It covers several areas including physical, social, and cognitive effects. The FSS is a patient-reported outcome composed of 9-items with scores ranging from 1 = "strongly disagree" to 7 = "strongly agree".

Heteroplasmy level of mitochondrial DNA from blood and urine samples will be compared between the beginning of the training (6 months, S0), and 9 (S12) and 6 (S24) months after training period.

Muscular pain level will be measured with the visual and analog scale for pain before and after each training session. Scorer ranges from 0 to 10, 0 being "no pain" and 10 being "maximum thinkable pain"

Clinical and biological tolerance will be measured with the blood creatine phosphokinase levels before training and during training period (12 weeks before the begining of training period, at the begining of training period and 2, 4, 8, 12, 16, 20 and 24 weeks after the begining of training period)

Evolution of clinical markers (strength, endurance, global functional abilities in walking and during transferts) will be matched with number of completed training sessions, in order to identify a dose-effect relationship

RPAQ is a splited in 3 parts: physical activity within and around the house, travel to and from work and your work activity and hobbies. This questionnaire assess:

• physical activity level (inactive if score is less than 8.3 Metabolic Equivalent of Task (MET).h/week, moderate if score ranges from 8.3 to 16.7 MET.h/week or high physical activity if score is greater than 16.7 MET.h/week)
• sedentary time (settled is score is greater than 7 hours per day or not settled if score is less than or equal to 7 hours per day).

GPAQ is a splited in 3 parts: activities at work, to move from one place to another and hobbies. For each part, score is ranked according to 3 levels: low, moderate and intense.

Heteroplasmy level of mitochondrial DNA from blood and urine samples will be assessed at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).

Blood creatine phosphokinase levels will be assessed at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).

Muscular strength of upper (shoulder abduction, elbow and fingers bending) and lower (knee extension) limbs during isometric and maximal muscular contractions will be measured with a quantified muscle testing device at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0). Upper limbs strength will also measured during the developped sitting with dumbbells at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).

Modification of functional abilities in walking will be measured by the maximal distance of walking (in meter) during a 6-minutes walking test, at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).

Modification of functional abilities during transferts will be measured by the maximal number of transferts sitting to standing performed during a 1-minute chair lifts test, at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).

Quality of life will be measured with the Quality of Life in Genetic Neuromuscular Disease Questionnaire (QOL-gNMD) at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0). The QoL-gNMD is splitted in 3 domains: "Impact of Physical Symptoms" (score from 0 to 19), "Self-perception" (score from 0 to 24) and "Activities and Social Participation" (score from 0 to 27).

The tiredness felt will be measured with the Fatigue Severity Scale (FSS), at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0). The FSS is a unidimensional scale which focuses on the physical aspects of fatigue. It is a self-reported questionnaire developed to measure the impact of disabling fatigue on daily functioning. It covers several areas including physical, social, and cognitive effects. The FSS is a patient-reported outcome composed of 9-items with scores ranging from 1 = "strongly disagree" to 7 = "strongly agree".

RPAQ is a splited in 3 parts: physical activity within and around the house, travel to and from work and your work activity and hobbies. This questionnaire assess, at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0):

• physical activity level (inactive if score is less than 8.3 Metabolic Equivalent of Task (MET).h/week, moderate if score ranges from 8.3 to 16.7 MET.h/week or high physical activity if score is greater than 16.7 MET.h/week)
• sedentary time (settled is score is greater than 7 hours per day or not settled if score is less than or equal to 7 hours per day).

GPAQ is a splited in 3 parts: activities at work, to move from one place to another and hobbies. For each part, score is ranked according to 3 levels: low, moderate and intense. GPAC will be assessed at the beginning of observation phase (S-24) and 6 months later, at the beginning of the training (S0).