Biopsychosocial Factors and Muscle Morphology After a Resistance Exercise

Inclusion Criteria: * chronic low back pain lasting ≥ 12 weeks * current pain intensity ≥ 3/10 but no higher than an 8/10 on the Numeric Pain Rating Scale (NPRS) within the past 48 hours * resistance trained (defined as 2x/week for the past 8-12 weeks) * able to read and speak English for informed consent and completion of questionnaires * willing and physically able to complete all testing and intervention sessions. Exclusion Criteria: * History of spinal surgery, fusion, or fracture within the past 6 months * diagnosed degenerative disc disease, scoliosis, or spinal pathology that precludes safe exercise participation * use of an assistive device for walking (cane, walker) within the past year * pregnancy, due to contraindications for exercise testing and ultrasound -body weight ≥ 300 lbs., which exceeds the safe capacity of the Roman chair -- * current tobacco/nicotine use * current enrollment in physical therapy or structured rehabilitation for LBP, * cardiovascular, pulmonary, metabolic, or systemic disease that increases risk during exercise * nociplastic pain conditions (e.g., fibromyalgia) or neurological conditions that confound EIH responses * inability to complete ≥ 8 Roman chair repetitions with proper form during screening * non-English speaking