Amplify Gait to Improve Locomotor Engagement in Spinal Cord Injury

Spinal cord injury (SCI) affects \~42,000 Veterans. The VA provides the single largest network of SCI care in the nation. The lifetime financial burden of SCI can exceed $3 million. A major cost of SCI is impaired mobility. Limited mobility contributes to decreased ability to work, increased care requirements, secondary injury, depression, bone mineral density loss, diabetes, and decreased cardiovascular health. Among ambulatory individuals with iSCI, residual balance deficits are common and are strongly correlated with both functional walking ability and participation in walking activities. The development of effective rehabilitation tools to improve dynamic balance would substantially improve quality of life for Veterans living with iSCI. Improving mobility through interventions that enhance dynamic balance would positively impact health, independence, and the ability to integrate into social, intellectual, and occupational environments.

Background:

Among ambulatory individuals with incomplete spinal cord injury (iSCI), residual balance deficits are common and are a primary factor limiting participation in walking activities. There is broad recognition that effective evidence-based interventions are needed to enhance dynamic balance following iSCI. However, improving dynamic balance after iSCI has proven to be very challenging. Experimental interventions that amplify self-generated movements (e.g. error augmentation) may accelerate motor learning by intensifying sensory motor feedback and facilitating exploration of alternative motor control strategies. These features may be beneficial for retraining dynamic balance after iSCI. The investigators have developed a cable-driven robot to create a movement amplification environment during treadmill walking by applying a continuous viscous force field to the pelvis that is proportional in magnitude to a participant's real-time range of motion (ROM) velocity. The purpose is to investigate if locomotor training performed in a movement amplification environment can effectively improve dynamic balance and increase participation in walking activities of individuals with iSCI.

Specific Aims:

Aim 1: To evaluate if locomotor training performed in a movement amplification environment is effective for improving dynamic balance of individuals with iSCI. The investigators' pilot data found that following locomotor training performed in a movement amplification environment three individuals with iSCI each improved dynamic balance by more than 30%. These improvements were accompanied by faster over ground walking speeds and improved reactive balance. Thus, the investigators hypothesize that improvements in dynamic balance during walking will be greater when locomotor training is performed in a movement amplification environment when compared to locomotor training performed in a traditional treadmill environment.

Aim 2: To evaluate the impact of locomotor training performed in either a movement amplification environment or in a traditional treadmill environment on participation in walking activities. Based on evidence identifying a strong relationship between balance and steps per day in ambulatory individuals with iSCI, the investigators hypothesize that training in the movement amplification environment will positively impact dynamic balance, and in turn increase participating in walking activities.

Approach:

The investigators will conduct a two-arm parallel-assignment intervention and will enroll 36 ambulatory participants with chronic motor incomplete spinal cord injury. Participants will be randomized into either a Control group receiving locomotor training or an Experimental group receiving locomotor training performed in a movement amplification environment. All participants will receive 20 training sessions. The investigators will assess changes in dynamic balance using measures that span the International Classification of Functioning, Disability and Health (ICF) framework including; 1) clinical outcome measures of gait, balance, and quality of life, 2) biomechanical assessments of the capacity to control COM motion during walking, and 3) data collected from activity monitors to quantify changes in participation in walking activities as evaluated by number of steps taken per day.

Impact:

Training dynamic balance of individuals with iSCI by amplifying their own self-generated center of mass motion during walking is a radical departure from current practice and may create effective new clinical strategies for addressing balance impairments of individuals with iSCI. Successful outcomes from the proposed trial would motivate development of clinically-feasible tools to first replicate and then to evaluate the movement amplification environment within the VA's clinical care settings. Knowledge gained from this study will expand the understanding of how individuals with iSCI learn dynamic balance and how targeted dynamic balance training impacts participation in walking activities.

Eligibility Criteria:
Inclusion Criteria:

* Medically stable with medical clearance from a physician to participate
* Neurologic level of the SCI between C1-T10 with American Spinal Injury Association (ASIA) Impairment Scale (AIS) C or D
* \> 6 months since initial injury
* Passive range of motion of the legs within functional limits and not restricting the ability to engage in locomotor training
* Able to ambulatory 10m with no physical assistance, use of assistive devices (e.g. single cane, rolling walker), and/or braces that do not cross the knee joint (e.g. anklefoot orthosis) are permitted
* Able to provide transportation to and from the testing location.

Exclusion Criteria:

* Excessive spasticity in the lower limbs as measured by a score of \> 3 on the Modified Ashworth Scale
* Inability to tolerate 30 minutes of standing
* Severe cardiovascular and pulmonary disease
* History of recurrent fractures or known orthopedic problems in the lower extremities (i.e. heterotopic ossification)
* Concomitant central or peripheral neurological injury (i.e. traumatic head injury or peripheral nerve damage in lower limbs)
* Inability to provide informed consent due to cognitive impairments
* Presence of unhealed decubiti or other skin compromise
* Enrollment in concurrent physical therapy or research involving locomotor training
* Use of braces/orthotics crossing the knee joint
* Known pregnancy