 Definition of Participant Samples Study Population One-hundred sixty male or female Veterans Active Duty military personnel with chronic SCI, six months duration, 21 years of age, functional use of their hands, medically stabile, and wheelchair users for indoor and outdoor mobility, will be eligible for screening. All potential participants will be Veterans Active Duty military personnel with SCI. Study participants will generally be outpatients with the exception of those inpatients who meet the eligibility criteria, and who are approved by the Site Investigator e.g., some inpatients may have been admitted for a wheelchair fitting or another non-medical reason. Non-veterans with SCI will not be. 