Physical Therapy’s Secret Weapon: Blood Flow Restriction Training

What is Blood Flow Restriction Training?

Blood Flow Restriction Training (BFR) is a rehabilitation or training technique which utilizes a

pressurized cuff or tourniquet to restrict blood flow to a targeted limb to increase the muscle

hypertrophy (muscle growth) response to exercise with significantly reduced loads. (3) In short, it allows you to get similar muscle growth from a much lower weight or resistance. This feature of BFR makes it ideal for rehabilitating limbs which cannot handle higher resistances, such as post-operative ACL surgery patients. (3) However, it can be performed by healthy adults as well to increase response to exercise. (6)

During a workout or rehabilitation session, a blood pressure cuff or tourniquet is wrapped around the shoulder or thigh just below either the shoulder or hip joint. (5) The cuff or tourniquet is inflated to restrict between 40-90% of blood flow. (5) Next, the participant will be asked to perform an exercise, such as a bicep curl, using around 20-40% of their one-repetition maximum (1RM) weight. (5) A one-repetition maximum weight is the maximum amount of weight you can tolerate in an exercise performed for only one repetition. The 1RM is crucial for calculating the adequate resistance level for these exercises. In the literature and my clinical practice, the reps per set distribution can look like this: 30/15/15/15. (5) After completing the required 1-4 sets of exercises with appropriate rest in between, the cuff or tourniquet is loosened to allow the blood to return to the limb. This can be repeated several times but should be monitored closely as it can be dangerous if done incorrectly.

How Does Blood Flow Restriction Training Work?

The reason why blood flow restriction increases a muscle’s ability to grow has to do with the

specific biochemical requirements of our 3 types of muscle fibers. Human skeletal muscle, the muscle we intend to grow when we go to the gym (such as the quadriceps femoris or biceps brachii), has three distinct muscle fiber types: Type 1, Type 2a, and Type 2b. (4) Type 1 muscle fibers allow us to perform motor tasks that require endurance, such as running or biking for long distances, and they require high blood-oxygen levels to work properly. (4) Type 2 muscle fibers are our fast twitch muscle fibers, and they thrive in environments in which blood-oxygen levels are low, such as when we are doing moderate to intense workouts requiring a lot of oxygen like resistance training. (4) Type 2 muscle fibers (particularly Type 2b, which are responsible for intense, short bursts of muscle contraction) are the primary muscle fibers we associate with hypertrophy, or growth of the muscle that is the desired outcome of a good workout. (4) In short, BFR changes how our body uses its own muscle fibers to improve hypertrophy.

It is important to understand how our muscles work to glean the benefits of BFR. The oxygen we breathe during workouts moves from our blood into our muscles through natural biochemical processes to produce energy molecules which allow us to function, creating what is called an “anaerobic environment”. (4) Our Type 1 muscle fibers are small, while our Type 2 muscle fibers are larger. When performing exercise, our body exhausts the smallest muscle fibers first, recruiting the bigger type 2 fibers only when necessary to maximize efficiency. (4) When blood oxygen reaches low levels during moderate to intense activity, the body responds by recruiting the larger type 2 fibers. (4) Blood Flow Restriction Training works by reducing the blood-oxygen levels to a working limb and tricking out body into recruiting these type 2 fibers earlier, which increases hypertrophy. (4) Two other ways in

which BFR increases muscle growth is through the release of human growth hormone and increase in cellular swelling in the muscles, both of which increase muscle growth. (4, 6)

The physical act of cutting off blood contributes to muscle growth. First, it reduces blood flow,

which mimics the blood oxygen levels found around muscles that are exercising. (4) When blood oxygen levels are low, our blood becomes more acidic from lactic acid accumulation. Second, cutting off blood flow increases how much venous blood (or blood returning to your heart) accumulates in your muscles. (6) Venous blood has less oxygen in it than arterial blood, so the blood-oxygen levels around your muscles reduce and your muscles fatigue more quickly. (6) In response to the low blood-oxygen and muscle swelling, local receptors send messages to an area of our brain called the Hypothalamus to release growth hormone. (4)

Who Can Benefit from Blood Flow Restriction Training?

Blood Flow Restriction Training is primarily performed in physical therapy clinics or

professional athletic facilities due to its equipment requirements and potential for dangerous side effects if performed incorrectly. Like any medical procedure, the list of contraindications (cases in which the technique should not be utilized) should be considered, and includes those with:

• Vascular or clotting disorders like DVT, peripheral vascular disease, thrombophlebitis,

• poor circulation, or varicose veins (3)

• Cardiovascular issues like hypertension, cardiomyopathy, or stroke (3)

• Active infections, pregnancy, lymphedema, cancer, sickle cell disease (3)

• Open wounds, surgical sites, fractures, nerve injuries, sensory issues or tumors on the

• involved limb (3)

This is not an exhaustive list, and it is crucial to speak with your physician or physical therapist before beginning Blood Flow Restriction Therapy. In the scientific literature and my own professional practice as a licensed physical therapist, Blood Flow Restriction Therapy can be effective, under proper supervision, for the following populations:

• Recreational or Professional Athletes (3)

• Select post-operative orthopedic patients (ligament reconstructions like ACL, Meniscus

  repairs, or others) (3)

• Elderly populations (without medical contraindications) or those at risk for muscle atrophy (1, 6)

To learn more, speak with your local physical therapist, physiatrist or orthopedic

specialist about how you could benefit from Blood Flow Restriction Training. Make sure to

consult a physician before beginning any new exercise program.

Resources:

1. Baker BS, Stannard MS, Duren DL, Cook JL, Stannard JP. Does Blood Flow

Restriction Therapy in Patients Older Than Age 50 Result in Muscle Hypertrophy,

Increased Strength, or Greater Physical Function? A Systematic Review. Clin Orthop

Relat Res. 2020 Mar;478(3):593-606. doi: 10.1097/CORR.0000000000001090.

PMID: 31860546; PMCID: PMC7145054.

2. Liu H, Jiang L, Wang J. The effects of blood flow restriction training on post

activation potentiation and upper limb muscle activation: a meta-analysis. Front

Physiol. 2024 Jul 11;15:1395283. doi: 10.3389/fphys.2024.1395283. PMID:

39055689; PMCID: PMC11269198.

3. Lorenz DS, Bailey L, Wilk KE, Mangine RE, Head P, Grindstaff TL, Morrison S.

Blood Flow Restriction Training. J Athl Train. 2021 Sep 1;56(9):937-944. doi:

10.4085/418-20. PMID: 34530434; PMCID: PMC8448465.

4. Saraf A, Goyal M, Goyal K. Blood Flow Restriction Training-An Overview and

Implication in New Generation Physical Therapy: A Narrative Review. J Lifestyle

Med. 2022 May 31;12(2):63-68. doi: 10.15280/jlm.2022.12.2.63. PMID: 36157885;

PMCID: PMC9490016.

5. Vanwye WR, Weatherholt AM, Mikesky AE. Blood Flow Restriction Training:

Implementation into Clinical Practice. Int J Exerc Sci. 2017 Sep 1;10(5):649-654. doi:

10.70252/LYGQ7085. PMID: 28966705; PMCID: PMC5609669.

6. “Work Out Smarter, Not Harder, With Blood Flow Restriction Training.” Cleveland

Clinic, https://health.clevelandclinic.org/blood-flow-restriction-training. Accessed 15

Apr. 2026.