Could a muscle hormone shield bones after spinal cord injury?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Participants with SCI: * age 18 years or older * traumatic SCI at the cervical level 4 or lower that occurred at least 12 months prior to the start of the study * American Spinal Injury Association Impairment Scale A, B or C * uses a manual wheelchair as primary means of mobility (30+ hours per week) * is able to perform a transfer independently to and from a wheelchair * has adequate strength and upper extremity function to operate an arm ergometer Control Participants: * age and sex-matched to participant with SCI Exclusion Criteria: Participants with SCI: * active use of medications which potentially affect bone metabolism, including: parathyroid hormone and analogs, androgenic or estrogenic steroids, bisphosphonates, oral glucocorticoids (use for more than 3 months) * history of fractures or dislocations in the upper extremity from which the participant has not fully recovered * upper limb pain or injury that interferes with the ability to perform aerobic exercise * recent hospitalization for any reason (within the past three months) * history of coronary artery disease, coronary bypass surgery or other cardiorespiratory events or conditions * likely to experience clinically significant autonomic dysreflexia and/ or orthostatic hypotension in response to vigorous exercise * endocrinopathy or metabolic disorders of the bone * e.g. Paget's disease, renal bone disease * history of allergic reaction to lidocaine * any other conditions that the person's primary care physician deems is a contraindication to participation in arm ergometry exercise stress testing or vigorous exercise * pregnant * participation in another "Greater than Minimal Risk" study. Control Participants: * active use of medications which potentially affect bone metabolism, including: parathyroid hormone and analogs, androgenic or estrogenic steroids, bisphosphonates, oral glucocorticoids (use for more than 3 months) * history of neuromuscular conditions which could influence muscle gene expression * history of lower body musculoskeletal injuries from which the participant has not fully recovered * recent hospitalization for any reason (within the past three months) * history of allergic reaction to lidocaine * any other conditions that the person's primary care physician deems is a contraindication to the performance of a vastus lateralis muscle biopsy * pregnant * participation in another "Greater than Minimal Risk" study