 The purpose of the first stage of this study is to assess the association and prognostic value of respiratory variables to low back pain presentation and outcomes with standard physical therapy care. Thus, a prospective longitudinal cohort, observational repeated measures pre and post testing, design will be used for this portion of the study. Both the treating physical therapist and the patient will be blinded to the findings of the respiratory assessment in order to minimize the risk of treatment bias. Further, the physical therapy plan of care and the interventions administered will be at the therapists discretion and will not be standardized. Typically a multimodal treatment approach is used for LBP, which includes: patient education, therapeutic exercises to improve strength, flexibility, and motor control deficits, manual therapy to decrease pain and improve joint and soft tissue mobility, and physical agents for pain management. By allowing therapists to use their clinical judgment, we are maintaining a real world environment which improves generalizability of the results. Although this will introduce variability that may confound results, there is no evidence that any single treatment approach is superior for addressing all LBP patients. Thus, allowing therapists to use their clinical reasoning to subgroup and treat accordingly maintains the standard of practice for all patient care. 