Corticospinal and Motor Behavior Responses After 6-week Transcranial Direct Current Stimulation and Neuromuscular Electrical Stimulation Combined With Motor Control Exercises in Patients With Chronic Low Back Pain

This proposed study will use a sample of convenience between the ages of 18 and 40. Subjects who has low back pain more than 3 months or a recurrent pattern of low back pain at least two episodes that interfered with activities of daily living and/or required treatment will be recruited by flyers posted in 2 university physical therapy clinics, as well as word of mouth from subjects and friends. Subjects without a history of low back pain in lifetime will be also recruited to establish normative data. Subjects who are interested in participation will undergo a screening process using inclusion-exclusion criteria checklist and receive brief information regarding the study. If they meet all inclusion criteria, the consent process will be performed.

All subjects will fill out the information sheet for demographic data. Subjects in CLBP will undergo standardized movement system impairment examination and transverse abdominis muscle thickness measurement, self-report questionnaires; pain, disability, quality of life, and fear of movement) and functional tests (5-time sit to stand test, 2-minute step test, functional reach test, prone trunk extension test and abdominal curl test). The project manager responsible for organizing the data collection and blindness will arrange the appointments with the subjects for 2 biomechanical data collection. For the subjects who refuse to participate in biomechanical lab testing, they will proceed to 6-week intervention.

In the first visit (pre-intervention visit#1), biomechanical data including motion and clinical data, lumbar stability, and cortical excitability will be collected. The body landmarks will be identified. These landmarks include 1) lumbar spinous process of T12-S2, 2) lumbar erector spinae (ES) and multifidus (LM) (3 cm lateral to L3 spinous process and 2 cm lateral to L3 spinous process, respectively), 3) bilateral lateral epicondyle of femur, and 4) bilateral lateral malleolus. Spinous process of L1, S2, bilateral lateral epicondyle of femur, and bilateral lateral malleolus will be used as locations for motion tracking sensors, while ES and LM location will be used to place surface electrode for cortical excitability measurement.

For motion and clinical observation data collection, subjects will be instructed to perform 1) sustained positions including usual sitting, corrected position in sitting, usual standing, corrected position in standing, as well as 2) functional movements including active forward bend, stand to sit, sit to stand, walking for 30 seconds, stair ascending, stair descending, and pick up a box from the floor. Then, the subjects will be asked to perform clinical movement tests including active forward bend (waiter's bow), standing with posterior tilt, single leg stance on left and right foot, single leg squat on left and right leg, supine with right and left straight leg raise tests, supine with right and left hip abduction with knee flexion tests, quadruped backward rock test, prone with right and left knee flexion tests, prone with right and left hip internal/external rotation tests, prone with right and left hip extension tests. 1-2 repetitions of practice trial will be provided to familiarize with the movement. Each subject performs 2 sets of 3 consecutive repetitions of each functional movement and clinical movement test in fixed order, while 2 assessors independently rate presence/absence of aberrant movement. Thirty-second rest will be provided between movement tests (rest period can be longer if necessary). Pain intensity, heart rate and rating of perceive exertion (RPE) will be monitored after each test. Motion sensors will be removed.

After that, subjects will undergo lumbar stability test. Two electromagnetic tracking sensors will be placed on T12 and S2 spinous processes, while one sensor will be attached to hand-held dynamometer. Subjects will be asked to position in prone on the treatment bed with both feet on the floor. A researcher will apply 10-kg compression force on L1 to L5 spinous processes for 2 seconds. This 10-kg compression force is derived from the pilot work in which the researchers plotted the graph between compression force in X-axis and posteroanterior displacement in Y-axis. The graph demonstrated plateau (no displacement even increasing in compression force) at approximately 10 kg. Then, subjects will be asked to lift both legs away from the floor presumably activating LM, while the researcher re-apply the same compression force on L1 to L5 again. Pain will be recorded when applying compression force on each spinal level. Sensor displacement will be collected to represent lumbar stability.