Clinical Signs and Changes in Cervical Muscles Activity Evaluated by Magnetic Resonance Imaging During an Endurance Test

The MRI, after identifying the region of interest for each muscle, will be used to calculate a transverse relaxation time (T2) value (in milliseconds) for each muscle at two assessment points: before and after the cervical extensor endurance test. The aim is to evaluate the changes in T2 values induced by each muscle's contribution during the endurance test. Each MRI scan will last 11 minutes.

The inertial sensor will monitor the head and neck movements during the entire duration of the Cervical Extensor Endurance Test, in the three planes of space for cervical movements and for cranio-cervical flexion/extension movement.

The maximal duration of 3 minutes of the cervical extensor endurance test

The participant must stand with both feet bare on the floor, aligning them so that the big toe of the back foot is in contact with the heel of the front foot, knees straight and eyes closed.

The aim is to hold this position for 30 seconds without changing feet or reopening the eyes.a stopwatch is used to evaluate this test, during 30 seconds maximum.

The participant sits on a chair with a backrest, a helmet with a laser pointing forward is placed on his head.

A target is placed in front of him/her, against a wall 90 cm from the participant's forehead, so that the laser points to the centre of the target when the participant is in a comfortable neutral position.

The participant's ability to reposition himself in this neutral position is assessed by asking him to perform 6 successive movements of left, right rotation, flexion and then extension, before returning to the centre of the target, as close as possible to the starting position. These movements will all be performed with the eyes closed.

The offset between the return position and the starting position will be assessed by measuring the distance in millimetres from the centre of the target to the return position of the laser.

The next movement will only be performed after a return to the neutral position, performed passively by the experimenter.

The participant lies on his or her back with arms at his or her side and knees bent so that the feet are flat on the examination table, without a pillow.

The examiner places a two-finger thickness between the participant's external occipital protuberance and the table.

The participant is asked to perform maximum craniocervical flexion combined with cervical and cervicothoracic global flexion in order to touch the examiner's fingers under the head.

He must maintain the position as long as possible, without rising or falling and without losing the cranio-cervical flexion position. The test is therefore measured in seconds with a stopwatch. The longer the duration, the better.

The participant lies on his back with arms at his sides The test tool, a Stabilizer, is folded in 3 layers and placed just below the sub-occipital ridges and inflated so that the needle reads 20 mmHg in the starting position The participant is asked to actively perform a slow, measured craniocervical flexion so that he can reach the following graduations successively over a period of 2 to 3 seconds: 22 mmHg, 24 mmHg, 26 mmHg, 28 mmHg and 30 mmHg, starting each trial at 20 mmHg. The higher the level reached correctly, the better.

The test stops when the participant: fails to reach/hold the required level for 2 - 3 seconds, performs a retraction movement to reach the required level, performs a thoracic extension to reach the required level or uses superficial cervical muscle activity (sternocleidomastoid, anterior scalene) to reach the required level. In this case, the last stop (in mmHg) reached correctly is taken as an indicator of the level of performance for this test.

The participant lies on his or her back with arms at his sides. The test tool, the Stabilizer, and placed just below the sub-occipital ridges and inflated so that the needle reads 20 mmHg in the starting position The participant is asked to actively perform a slow craniocervical flexion in order to realize 10 repetitions of 10 seconds each, at the following pressure levels: 22, 24, 26, 28 and 30 mmHg The higher the level reached correctly, the better. The test stops when the participant: fails to reach/hold the required pressure level for 10 seconds, performs a retraction movement/ thoracic extension/ uses superficial cervical muscle (sternocleidomastoid, anterior scalene) activity to reach the required pressure level. In this case, the number of repetitions correctly performed at the last level reached are used to assess the performance as follow: each successful repetition has a value of 2%, reaching 100% at the 10th repetition performed at 30 mmHg.