AbstractsBiology & Animal Science

Individuals with a history of low back pain (HxLBP) may present with neuromuscular dysfunction of the trunk and lumbo-pelvic-hip musculature including the lumbar multifidus (LM) and transversus abdominis (TrA). Assessments for these muscles traditionally occur in an unloaded position, however people spend time participating in functional activities that may result in pain-generating positions. There is limited evidence to understand how testing positions affect LM and TrA function between individuals with and without a HxLBP. Dysfunction of these muscles could result in improper force attenuation at the lumbar spine, increasing risk for injury. The focus of manuscript 1 was to assess neuromuscular function of the LM and TrA through ultrasound imaging across multiple positions. We found that individuals with a HxLBP had reduced TrA function in the tabletop and seated positions. Additionally, testing position influenced muscle function across all individuals and among healthy and HxLBP individuals independently. The focus of manuscript 2 was to assess landing stiffness between individuals with and without a HxLBP and between males and females. We found that females have lower vertical stiffness and ankle joint stiffness values compared to males and that differences may exist between healthy and HxLBP individuals when accounting for gender. The focus of manuscript 3 was to assess relationships between LM and TrA muscle function and landing stiffness. We found that LM activation ratios (AR) were related to ankle and knee joint stiffness, TrA AR with vertical stiffness and PAR with both vertical stiffness measures, and lumbar spine stiffness. However, these relationships differed by HxLBP status. The combination of reduced TrA muscle function and altered force attenuation may place HxLBP individuals at risk for future episodes of low back pain.