The Rehabilitation Enhanced by Partial Arterial Inflow Restriction (REPAIR) Study will be conducted in a patient population of individuals recovering from a traumatic diaphyseal fracture of the femur. Although the intervention can be used for any patient with muscle weakness following trauma, the persistent thigh weakness that follows a femur fracture provides a perfect model for evaluating the effectiveness of the REPAIR protocol.

Inclusion Criteria:

1. Adults ages 18-55 inclusive
2. Admitted to one of the participating clinical centers for operative treatment of a closed diaphyseal femur fracture with one of the following OTA codes: 32A, 32B or 32C (treated with an IM Nail).

Exclusion Criteria:

1. Open diaphyseal femur fracture (except low velocity gunshot wounds) or severe crushing injuries to study limb.
2. Additional fracture, dislocations or soft tissue injuries to the study limb that would compromise the ability to weight bear as tolerated and initiate PT within 28 days of definitive fixation.
3. Any fractures, dislocations or soft tissue injuries to the contralateral limb or pelvis that would compromise the ability to weight bear as tolerated and initiate PT within 28 days of definitive fixation.
4. Any treatment of the study injury in either group that would preclude application of the tourniquet cuff (e.g. vascular reconstruction, wound, flap, or skin graft).
5. Injuries to other body systems (or other medical conditions) that would preclude the ability to weight bear as tolerated and initiate PT within 28 days of definitive fixation (e.g. spinal cord deficit; severe traumatic brain injury).
6. Use of blood flow restriction (BFR) at any time between treatment and the start of physical therapy for the study.
7. Non-ambulatory pre-injury.
8. Morbidly obese (BMI > 40).
9. History of Peripheral Artery Disease and/or Peripheral Vascular Disease (PAD/PVD).
10. Current or history of venous thromboembolism.
11. Impaired circulation or peripheral vascular compromise.
12. Previous revascularization at the study injury site.
13. Extremities with dialysis access.
14. Current diagnosis of acidosis.
15. Diagnosis of sickle cell anemia.
16. Current infection of the study injury.
17. Current tumor (malignant or benign) distal to study injury and future tourniquet placement.
18. Current use of medications or supplements that are known to increase clotting risk.
19. Diagnosis of severe hypertension (blood pressure of 180/110).
20. Skin grafts in which all bleeding points must be readily distinguished.
21. Secondary or delayed surgical procedures to study injury after immobilization.
22. Vascular grafting to the study injury.
23. History of lymphotomies.
24. Current diagnosis of cancer.
25. Unable to speak either English or Spanish.
26. Severe problems with maintaining follow-up (e.g. patients who are prisoners, homeless at the time of injury, who are intellectually challenged without adequate family support, or have document psychiatric disorders).
27. Unable to provide informed consent.
28. Patient has not been cleared to start physical therapy at the time of consent.
29. Patient is pregnant.
30. Patient received BFR between date of injury and start of Physical Therapy.