Abstract
The lumbopelvic-hip complex is comprised of a variety of muscles, including: both larger, global movers, and smaller, local stabilizers. One of the frequently studied local stabilizers is the transverse abdominis (TrA), which has documented dysfunction in the non-specific low back pain (NSLBP) population. The TrA has also been used as a representative of core function in many of these studies by providing muscle thickness changes and activation. Ultrasound imaging (USI) is commonly used to provide a real-time view of muscle thickness and is reliable in not only static, rested positions, but also during movement in functional tasks. Due to the preparatory nature of TrA contraction prior to movement, its influence on motion at the extremities becomes of great interest to further understanding the role of core stability in individuals with injury, specifically chronic musculoskeletal injury. Core or trunk involvement in other chronic musculoskeletal injuries, such as patellofemoral pain (PFP) have been a focus recently in sports medicine research. Most of the recent studies have only examined core endurance, through plank or bridging tasks, however the examination of the role of local spinal stability prior to movement could develop the understanding of this challenging pathology. The examination of effects on TrA activity in various positions and plank endurance times following a 4-week impairment-based rehabilitation program addresses both the specific core muscle activity and core endurance aspect aforementioned. Another muscle group within the lumbopelvic-hip complex that has been linked to PFP are the gluteal muscles due to their role at the hip, pelvis, and distal influences at the knee. The gluteus medius (Gmed) has been the prime muscle of interest for most researchers due to its known weakness and diminished neuromuscular control in the literature. Gluteus maximus (Gmax) contributes to this overall dysfunction, however its role as a larger, global mover becomes less of a focus in many descriptive and rehabilitation-based studies. An increase in knowledge of how the Gmax and Gmed, collectively and individually, function is important in addressing deficits found in the PFP population. Strength assessment and muscle activation, via electromyography (EMG), are the most common methods of collecting muscle function of the Gmax and Gmed. Though, these methods do not provide a visual of the actual tissue moving real-time and cannot account for spatial or morphological changes of the muscles. USI, as utilized in NSLBP, could serve this role in the PFP population and act as an adjunctive method of muscle activity assessment. Gmed and gluteus minimus ultrasound has been performed in other studies, but with only a healthy population or individuals with hip pathology. These prior studies have also predominantly used M-mode USI, which provides information on onset of muscle motion and timing, but not static images of muscle thickness obtained by the use of B-mode USI. Fascial borders of muscle tissue are necessary to visualize clearly to measure muscle thickness and B-mode imaging has been shown to have the optimal fascial view over M-mode. The determination of Gmax and Gmed activity following an impairment-based rehabilitation program assessed through USI and EMG serves as a dual approach to muscle activity in a PFP population and allows clinicians to understand not only how the glutes are activating electrically, but moving spatially as well. Due to the influence of proximal structures on chronic pathologies involving the lumbopelvic-hip complex, it is important for researchers and clinicians in the sports medicine community to identify a potential common thread between these pathologies. USI is advantageous in the determination of this potential common thread as it allows a non-invasive, real-time, reliable view of this deeper musculature. The relationship between core stability and lower extremity function has been explored recently as well and seems to be relevant to sports medicine and health care professionals, especially in regard to tracking injury occurrence and effects of rehabilitation. Since the TrA is one of the deeper local stabilizers that contracts in a preparatory manner before limb movement, it becomes of increased interest as the probable commonality. Quantification of TrA activity in individuals with chronic musculoskeletal conditions, including: NSLBP and PFP, and the comparison of those individuals to their healthy counterparts would answer the commonality question. Just as core endurance has migrated into studies of pathologies beyond just low back pain, more fine motor control at the local level is the logical next step. Therefore, the overall purpose of this study is to determine lumbopelvic-hip function, through TrA activation, core endurance, Gmax and Gmed activation, following rehabilitation in those with PFP and TrA activity at baseline in those with PFP, NSLBP, as compared to healthy individuals.
