Muscular Rehabilitation by Eccentric Exercise After Severe COVID-19 Infection

Average change from baseline walking capacity measured by the 6-minutes walk test (6MWT), expressed in meters. All patients will be asked to cover the longest distance over a 30-meters distance in 6 min with or without stopping and with standardized verbal encouragements according to standard recommendations; to take into account a learning effect, the test will be performed twice, with the longer distance retained, expressed in meters. To prevent adverse effect, pulsed oxygen saturation (% of pSO²) and heart rate (heartbeat per minute) will be monitored continuously throughout the test by using a digital oximeter.

this test consists of assessing balance in a standing position, lifting from a chair (5 stand to-sit repetitions) and measuring 4-m walking speed (20). The patient walks 4 m at a normal and comfortable speed. The "test zone" (4 m) is preceded by an "acceleration zone" (1 m) and is followed by a "deceleration zone" (1 m). The assessor starts and stops the timing when the subject's foot meets the ground when entering and leaving the "test area", respectively.

maximum muscle strength of the quadriceps, on the dominant limb, will be measured on a bench: - Strength during isometric contraction (at 90° knee flexion) - Standardized position with the arms crossed on the chest, the absence of back support during the measurement and the maintenance of the hips and the contralateral leg to avoid any compensating movement Three reproducible measurements (±10%) will be taken at 1-min intervals, with the highest value retained.

this test consists of performing 10 knee extensions at 10% QIMS, then gradually increasing the load (10% by 10%) until exhaustion (cannot perform the movement 2 consecutive times). The value retained is the last level (% QIMS) performed.

this scale explores cognitive (10 items), physical (9 items) and psychosocial (2 items) fatigue. The MFIS included 21 items with a total score ranging from 0 to 84 with higher scores indicating a greater impact of quality of life.

This questionnaire explores 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EQ-5D-5L included 5 items independently scored from 1 to 5 (higher scores indicating a greater impact)and a 0-100 visual analogic scale exploring general health (0 means the worst heath patient can imagine, 100 means the best health patient can imagine).

measurement is in 90° elbow flexion, wrist in neutral position. Three reproducible measurements (± 10%) will be taken at 1-min intervals, with the highest value retained.

Plasma metabolome profile assessed by variation of number of blood metabolites. Changes from baseline to post-training intervention in plasma metabolome profile will be compared between excentric and concentric exercise groups.

Biopsy from the Vastus lateralis will be performed and the variation of cross sectional area measurement of muscle fibers (µm2) will be analysed and compared between excentric and concentric exercise groups from baseline to post-training intervention.

Biopsy from the Vastus lateralis will be performed and the capillarization (variation of capillary to fiber ratio) will be analysed.

Muscle adapations from baseline to post-training intervention will be compared between excentric and concentric exercise groups.

Biopsy from the Vastus lateralis will be performed and the evolution of number of satellite cell per muscle fiber will be analysed and compared between excentric and concentric exercise groups from baseline to post-training intervention.

Electrophsyiological stimulation of the quadriceps for the measurement of the neuromuscular activation before, during and after the QIF test. During this test, we measure maximal M-wave, contraction time and torque and the percentage of neuromuscular activation. Neuromuscular activation will be analysed and compared between excentric and concentric exercise groups from baseline to post-training intervention.

An infrared spectroscopy device is localized on the anterior part of the quadriceps. The device measures hemoglobin and desoxyhemoglobin concentration under the placement area. This measure is performed, before, during and after the QIF test. During this test, we measure the hemoglobin and desoxyhemoglobin concentration as well as the tissue saturation index.Quadriceps muscular Oxygen Tissue Saturation will be analysed and compared between excentric and concentric exercise groups from baseline to post-training intervention.

A gaz exchange device records the O2 uptake during the 6 minutes walk test. The O2 uptake efficiency was defined as the volume of O2 per meter used by the participant.

An infrared spectroscopy device is localized on the anterior part of the quadriceps. O2 uptake Efficiency during walk test will be analysed and compared between excentric and concentric exercise groups from baseline to post-training intervention.

A blood sample collection to measure the CPK concentration.

A blood sample collection to measure the CPK concentration.

A blood sample collection to measure the CPK concentration.

A blood sample collection to measure CRP concentration.

A blood sample collection to measure CRP concentration.

A blood sample collection to measure CRP concentration.