The goal of this clinical trial is to learn if a motorized prosthesis can improve mobility in individuals with amputation. The main question it aims to answer is:

• Does motorized prosthesis improve ambulation speed, balance, control, or efficiency when performing everyday activities?
• What problems arise when using a motorized prosthesis? Researchers will compare mobility of the participants when using and not using the motorized prosthesis to see if mobility and/or function improves.

Participants will perform various activities with and without the motorized prosthesis including:

• Walking at a mild incline/decline (0°-15°) on treadmill or over-ground
• Ascending or descending stairs
• Stand to sit and sit to stand transitions
• All terrain walking over ground
• Turning
• Any combination of the above-mentioned activities

Participants will perform ambulation activities (see list below) while using their prescribed prosthesis or the motorized prosthesis in conjunction with their prescribed passive prosthesis. Each ambulation activity will be tested in four different conditions:

1. Ambulation with their personal (take home) device. This condition acts as a baseline to which the ambulation with the motorized prosthesis can be compared.
2. Ambulation with the motorized prosthesis in the "off" configuration (i.e., no power is applied to the motor). This condition demonstrates the impact of the device when it is unpowered.
3. Ambulation with the motorized prosthesis in the "transparent" configuration (i.e., minimal power is applied to the motor, such that the device behaves as a free hinge). This condition demonstrates the impact of the device when it behaves as a free hinge, similar to the participants personal device.
4. Ambulation with the motorized prosthesis in the "powered" configuration (i.e., substantial electrical power is applied to the motor to replicate the function of the biological joint). This condition assesses the impact of the motorized prosthesis to improve ambulation of the participant.

Trials will take place over-ground and/or on a treadmill. Participants will walk for up to 40 minutes. Frequent breaks will be provided between trials and conditions to avoid fatigue and a maximum of 15 minutes of continuous walking will take place between breaks. When deemed necessary by the research staff or participant, crutches, canes, walkers, an overhead support system, or other ambulation or safety aid will be used to minimize the risk of a severe fall.

List of ambulation activities

1. Walking at a mild incline/decline (0°-15°) on treadmill or over-ground
2. Ascending or descending stairs
3. Stand to sit and sit to stand transitions
4. All terrain walking over ground
5. Turning
6. Any combination of the above-mentioned activities

The above conditions will be assessed using motion capture techniques in the laboratory environment which will include measures of metabolic energy consumption and muscle activity.

All terrain walking over ground will take place on campus and include Engineering, Business, and Learning resource Center buildings, the north and south quads, and campus walkways and urban trails. During all terrain walking, the participant will be attended by research personnel that will monitor subject safety.

Inclusion Criteria:

• Individuals age 18 to 85 with or without lower-limb amputation
• Able to understand and follow simple directions in English based on ability to provide verbal consent
• Able to walk at least 30 feet with or without a walking aid
• Able to safely fit into a device configuration and tolerate assistance
• Individuals with lower-limb amputation must receive physician approval to participate in the study.

Exclusion Criteria:

• Any neurological, musculoskeletal (other than lower-limb amputation) or cardiorespiratory injury, health condition (including pregnancy), or diagnosis that would affect the ability to walk as directed for short periods of time.
• Participant or caregiver report that the perspective participant's physician has recommended that they not engage in moderate intensity walking exercise.
• Subject mass greater than the engineered limit of the device (90 kg or 198 lbs) Note: No exclusions will be made on the basis of race, gender or ethnic background.

Uncertain if will publish in ICMJE journal