Lumbar Extension Strengthening in Addition to Manual Therapy and Exercise for Chronic Low Back Pain

Purpose: The purpose of this study is to determine the effect of adding lumbar strengthening exercises to a program of manual therapy and motor control exercises in individuals with chronic low back pain. Primary Aim: * Compare patient reported outcomes in individuals with cLBP that receive lumbar extensor strengthening in addition to a standard program of manual therapy \& motor control exercises compared to manual therapy \& motor control exercises alone. Secondary Aims: * Compare lumbar multifidus morphology (thickness) and extensor endurance in individuals with cLBP that receive lumbar extensor strengthening in addition to a standard program of manual therapy \& motor control exercises compared to manual therapy \& motor control exercises alone. * Compare the amount and type of healthcare utilization between the two groups during the study period and the 12-month period following enrollment in the study. Study Design: This will be a parallel randomized control trial with two arms. Participants will be randomly assigned to either the experiment (manual therapy, motor control, \& lumbar strengthening) or control (manual therapy \& motor control) group. Procedures: The following procedures will be conducted once the participant has signed and received their Informed Consent Document (ICD) and HIPAA Authorization. The initial baseline visit involves the participant completing the electronic questionnaires, lumbar multifidus assessment (via ultrasound), back endurance test, randomization, and an initial physical therapy evaluation. INITIAL VISIT - BASELINE MEASURES \& START OF TREATMENT Baseline Questionnaires: Participants will be provided a tablet to complete research questionnaires electronically, described below, using REDCap. If a tablet or the internet is not available, participants will fill out a paper copy that the research team will later transfer on to REDCap. REDCap is a secure, HIPAA-compliant web application used to build, administer, and record surveys. Baseline Ultrasound Measurement - Lumbar Multifidus Thickness: Once the surveys have been completed, study participants will have their lumbar multifidus thickness measured. The subject will lie prone with a pillow underneath their pelvis. Ultrasound images, using a curvilinear probe, of the lumbar multifidus muscle at rest will be captured. Three measurements of the muscles thickness will be captured, and the average on each side will be recorded at two vertebral segments (L4/L5 \& L5/S1). Images will be saved on a facility device for measurement. Baseline Back Endurance Performance: After completing the ultrasound measurements, subjects will perform a back endurance test (Biering-Sørensen test) on the variable angle roman chair. Subjects will be positioned prone at a 0 degree angle with their iliac crests at the edge of the hip pads and their legs stabilized on the ankle pads. The time starts once their trunk is horizontal with their hands crossed at the chest. The test will continue until the participant breaks from the horizontal posture. Randomization: Following completion of the above procedures, participants will be randomized into one of the following groups: the standard physical therapy group (SPT) consisting of manual therapy \& motor control exercises, or the experimental group consisting of the standard physical therapy protocol plus lumbar extensor strengthening exercises (SPT+LEX). The method of group assignment will be sequentially numbered opaque sealed envelopes. To minimize the risk of predicting the treatment assignment of the next eligible subject, randomization will be performed in permuted blocks of 2 or 4 with random variation of the blocking number. Both groups will begin standard physical therapy treatment on the same day as their baseline examination and will be scheduled for their subsequent appointments at the Physical Therapy clinic. The initial physical therapy evaluation will last approximately 60 minutes. The treatment groups are outlined below: Group 1- Standard Physical Therapy (SPT): Participants randomized to the SPT group (control group) will receive pragmatic treatments of manual therapy and motor control exercises based on their clinical presentation, which is consistent with standard patient care management of chronic lower back pain. They will attend a total of 10-14 visits over a course of 8 weeks, as is typical for routine care of individuals with cLBP. The treating physical therapist will use manual therapy and motor control exercise interventions that will be tailored to the patient's individual presentation. Manual therapy is used by physical therapists to improve and restore movement patterns of the spine and extremities in individuals with LBP. Examples of manual therapy interventions include joint mobilization or manipulation, manual muscle stretching, and soft-tissue mobilization. Motor control exercises (MCE) are designed to restore the coordination and timing of trunk musculature. Group 2- Standard Physical Therapy Plus Lumbar Extensor Strengthening (SPT+LEX): Participants randomized to the SPT+LEX group (experimental group) will receive the same pragmatic treatments of manual therapy and MCE as the SPT group over the same number of visits (10-14). In addition to MCE and manual therapy, this group will perform specific lumbar extensor strengthening (LEX) exercises toward the end of each physical therapy treatment visit. These LEX exercises target the lumbar extensor muscle group (to include the lumbar multifidus) and may be performed by lying prone on the edge of a bench or mat and lifting the legs to parallel while the torso is stabilized. Alternatively, they may be performed by stabilizing the hips and legs while lifting the torso to varying angles from horizontal with or without weights. LEX exercises are progressed by increasing hold times or weight, depending on the participant's tolerance and clinical progression Total time spent with the participant will be equal in both groups (40 minutes)