Investigation of Trunk Muscle Size and Function in Older Adults With Chronic Low Back Pain

Rehabilitative Ultrasound Imaging (US) is a procedure used to evaluate skeletal muscle size and function to inform clinical practice. US has been shown to be a reliable and valid tool for measuring changes in trunk muscle (i.e. abdominal and back muscle) size and activity during sub-maximal contractions in younger populations. Younger adults with low back pain as compared with healthy adults without pain demonstrate smaller back muscle size, lower back muscle activity, and greater back muscle asymmetry (differences in right side compared with left side). No trials are published evaluating muscle adaptations using US in response to clinical treatments for low back pain in the older adult population. Increased muscle size and improved muscle symmetry have been reported in younger adults with low back pain who participate in low back stabilization exercises. These exercises use voluntary contractions of the back muscles with prolonged hold times and low loads. Neuromuscular Electrical Stimulation (NMES) is a treatment modality that increases muscle activity when voluntary activity is impaired and increases muscle size. Most studies assessing muscle size and activity in response to NMES have been conducted in the knee muscles (i.e. the quadriceps), while the impact of NMES on the back muscles remains relatively unexplored. Given the potential to evaluate back muscle size and activity with US, this assessment tool may be used to document muscle adaptations to a clinical intervention in older adults with low back pain. The purpose of this study is to conduct a 6-week clinical trial to determine if NMES plus lumbar stabilization exercises (i.e. NMES AND Stabilization Exercises) is superior to lumbar stabilization exercises (i.e. Moist Heat AND Stabilization Exercises) for improving back muscle size, activity, and side-to-side (i.e. right side versus left side) symmetry in older adults with chronic low back pain (i.e. low back pain of greater than 3 months). Muscle size,