Blood flow restriction (BFR) is an effective therapy for shoulder injuries, confirmed a recent Houston Methodist study that identified the optimal occlusion pressure for rehabilitating patients.

The study, published in the American Journal of Sports Medicine, found that combining upper extremity BFR with low-intensity rotator cuff training led to substantial improvements in shoulder lean mass, work capacity and strength compared to strength training alone. The optimal occlusion pressure was 50%.

"Patients who are recovering from an injury or recent surgery are often not able to perform high intensity exercises with high loads because it increases the risk of re-injuring the area," said Dr. Patrick McCulloch, study co-author and the John S. Dunn Chair in Orthopedic Surgery at Houston Methodist. "Blood flow restriction has recently gained traction with orthopedics and rehabilitation specialists because it tricks the body into thinking it's working harder than it really is, producing higher returns without higher costs."

BFR uses specialized cuffs to partially restrict blood flow to distal contracting muscles during exercise. The method enhances muscle strength without increasing the intensity of the training regimen.

Researchers in the Houston Methodist Department of Orthopedics & Sports Medicine undertook the new study to refine BFR protocols for the upper extremities. Proximal targeting of shoulder musculature under varying occlusion pressures previously had not been explored.

Shoulder injuries are the third most common musculoskeletal complaint reported in primary care. They frequently occur in contact and overhead sports and are particularly prevalent in throwing sports such as baseball or softball.

While various surgical treatments and physical therapies can improve shoulder function, pain and range-of-motion limitations can sometimes persist for years after the initial injury.

Previous studies have suggested that optimal occlusion pressures ranged from 40%-80% for safety, efficacy and adherence. However, these guidelines have predominantly relied on electromyographic amplitude (EMGa) findings for distal upper extremity musculature only.

Houston Methodist researchers attributed improvements shown in the new study to enhanced shoulder muscle activation while under occlusion, suggesting underlying metabolic and neuromuscular mechanisms.

"Interestingly, the muscles above and below the occlusion cuff both get stronger when blood flow is restricted," Dr. McCulloch noted. "We really wanted to get a better understanding of what the ideal occlusion pressure would be for a variety of targeted shoulder muscles so that we could maximize effectiveness while minimizing discomfort and risk."

To that end, Dr. McCulloch, Tyler Roehl, PT, DPT, ATC, Bradley Lambert, Ph.D., Jordan Ankerson, BS, Karen Hernandez, BS, and Corbin Hedt, PT, DPT, enlisted fifteen untrained healthy adults to participate in the BFR shoulder study.

Each participant underwent four experimental sessions, performing three rotator cuff exercises (cable external rotation, cable internal rotation and dumbbell scaption) at low intensity (20% of maximal strength) with different occlusion pressures restricting blood flow to the extremity (0%, 25%, 50% and 75%). Data was collected at five sessions spaced at least 48 hours apart for each participant.

The results indicated that proximal shoulder muscle activation is occlusion-dependent, with EMGa-measured muscle activation escalating linearly as occlusion pressure increased.

"However, there is a point of diminishing returns once you get above 50% occlusion, coupled with a notable reduction in work capacity and increase in discomfort reported by the participants," Dr. McCulloch said. "This indicates that the optimal occlusion pressure for shoulder muscle targeting during rotator cuff exercise lies somewhere around 50%, depending on the exercise and the tolerance of the individual."

Dr. McCulloch says implications for this study go beyond clinical rehabilitation settings. Professional, collegiate and youth competitive sports teams are paying attention as well and are beginning to incorporate BFR into the training of even healthy athletes.

"BFR is a potential game-changer in many respects, but it's important at this early stage that we study it carefully, so we know how different prescription parameters will influence outcomes among different groups."