The purpose of this study is to test a low cost, non-invasive, wearable near-infrared spectroscopy (NIRS) sensor, previously validated for able-bodied athletes as a rehabilitation aid for war-fighters with lower extremity limb loss. This sensor can record real-time physiologic data that relates to total fitness capacity and exertion levels and may help develop individualized programs on a per-patient basis. The uniqueness of this NIRS measurement system is that it provides real-time muscular oxygenation, dehydration, and iron status during whole-body exercise, as well as training-induced adaptations. Currently, no technology like this has been tested in an amputee population. Successfully validating this technology in a wounded warrior population would provide vital information regarding tissue perfusion after injury and new opportunities for improving rehabilitation outcomes.

Inclusion Criteria:

1. Military health care beneficiary and veterans for enrollment.
2. Between 18 and 45 year old.
3. Possess a unilateral transtibial or transfemoral amputation.
4. Low risk for cardiovascular disease.
5. Ambulatory without assistive ambulatory device.

Exclusion Criteria:

1. Exclusion criteria includes individuals outside of our age range or if over the age of 18 and under the age of 45 will be excluded if found at risk according to the ACSM/AHA pre-participation screening questionnaire for exercise testing.
2. Told by a doctor that they should not exercise.
3. Orthopedic injury/surgery of the lower extremity within the last year
4. Less than 5" x 2.5" of soft tissue proximal to the prostheses (since the sensor will need to be placed on the soft tissue proximally)
5. Hip or shoulder disarticulation.
6. Regular use of medications designed to alter cardiovascular function;
7. Unwilling to comply with the study protocol.
8. Individuals with a fat layer greater than 10mm in correspondence of the location of the NIRS probe (thigh).
9. Allergic reaction to latex, cotton, or polyester, which are the primary materials of an ace bandage.