Sensorimotor Integration Underlying Balance Control in Individuals With Incomplete Spinal Cord Injury

Sensorimotor Integration Underlying Balance Control in Individuals With Incomplete Spinal Cord Injury

Sensorimotor Integration Underlying Balance Control in Individuals With Incomplete Spinal Cord Injury: Assessing Neural Changes After the Injury and Promoting Recovery Through Specific Training

The objectives of the study are to evaluate a 4-week mixed training paradigm consisting of explosive strength training and balance perturbation training efficacy on balance control during standing and locomotion, and to understand the mechanisms of neuroplasticity that would improve sensorimotor integration at supraspinal and spinal levels.

After obtaining their consent, participants will undertake evaluations at different times: Assessment 1 week prior to training Training over 4 weeks (nature of the training depends on the group) Assessment 1 week after training Assessment 1 month after training (follow-up) Each assessment will be divided in 2 sessions and data will be collected over 2 days, at one session per day. Days can be consecutive or non-consecutive but will be within a given week. The assessment consists of: Session 1 (S1; duration: 3h) will include presentation of the Study and obtainment of consent, clinical tests, galvanic vestibular stimulation testing, postural reactions and gait assessment. Session 2 (S2; duration: 3h) will include muscle strength, short-afference inhibition, paired pulse and trans cranial magnetic stimulation conditioning of H reflex. After the initial assessment, iSCI participants will be separated in 2 groups and will receive combination of explosive strength and balance training or no intervention. The training will span over 12 sessions (3 times per week for 4 weeks) and each training session will last approximately 1h (including effective training and installation periods).

Combined explosive strength and balance training, Balance control, Corticospinal tract, Intracortical mechanisms, Vestibular system

This group will be formed with participants with incomplete spinal cord injury. This group will perform 4 weeks of combined explosive strength and specific balance training.

This group will be formed with participants with incomplete spinal cord injury. They will perform all the evaluation before and after a 4-week period of rest (no training).

Healthy participants will be recruited based on the age and sex of the participants with incomplete spinal cord injury to realize clinical and neurophysiological cortical evaluations.

Training will consist to perform one hour of combined ankle explosive strength training and specific balance training using randomized perturbations. Explosive strength training: Participants will perform only 2 sets of 3 min (12 contractions for each set) for both lower limbs and both ankle plantar- and dorsiflexion movements. Balance specific training: Participants will be standing, secured by an adjusted harness, which do not support the weight but is strictly there to prevent a fall. They will have online visual feedback of their CoP via an avatar on the screen in front of them. Each training session will consist of 10 sequences of 3 min, including the 5 different conditions: Forward tilt of base of support; Backward tilt of base of support; Translation forward; Translation backward; Without moving their feet, participants will have to move their avatar to reach different targets placed around them on the screen, at different distance from the center.

Evaluation of the latency on Soleus and Tibialis anterior muscles EMG following backward and forward perturbations will be done.

Evaluation of isometric dorsi- and planti-flexors muscle strength in Newton will be done using a force transducer attached to the participant's feet.

A paired-pulses paradigm (two trans cranial magnetic stimulations at motor cortex level) will be used to evaluate the intracortical mechanisms

A stimulation (using TMS) at motor cortex level will be triggered just after a peripheral electrical stimulation of tibial nerve to evaluate the peripheral afferents on cortical output.

A stimulation (using TMS) at motor cortex level will be triggered just before a tibial nerve stimulation to evaluate the modulation of the H reflex by the corticospinal tract.

Galvanic vestibular stimulation will be triggered during quiet standing. EMG responses of Soleus and Tibialis Anterior muscles will be analyzed.

Galvanic vestibular stimulation will be triggered during quiet standing. The displacement of the center of pressure will be analyzed using a force platform.

FOR PARTICIPANTS WITH SPINAL CORD INJURY Inclusion Criteria: Have an incomplete lesion of spinal cord Level of spinal cord lesion between C5 and T12 At least, 6 months post-injury Be considered as AIS C or D Be able to stand without support for 15 seconds Be able to provide informed consent in English or in French Exclusion Criteria: To have cognitive deficits To have personal or family history of epilepsy To have suffered moderate or severe traumatic brain injury To have cochlear implant FOR CONTROL PARTICIPANTS Exclusion Criteria: To have orthopedics problems To have cognitive deficits To have neurological problems