How does BFR work? And how do we use it with our patients after surgery?
A GUIDE TO BFR TRAINING, BY EXPERT PHYSICAL THERAPISTS
Blood Flow Restriction (BFR): What Is It and Why Should You Care?
If you're involved in the fitness or rehabilitation world, chances are you've heard about blood flow restriction training (BFR). Maybe you're already incorporating it into your routine, or perhaps you're skeptical, thinking it's another passing trend.
BFR isn't new or just a fad. With over 20 years of solid research backing it up, we have a strong foundation proving its effectiveness—especially in rehabilitation settings.
I'll admit, I was skeptical when I first heard about BFR as the fitness and rehab fields are filled with treatments that lack scientific backing. However, as more and more evidence emerged, it became clear that BFR is worth considering, particularly for surgery recovery.
So, what exactly is blood flow restriction (BFR) training? BFR is a rehabilitation technique that uses compressive bands to limit blood flow during exercise, reducing the oxygen supply to working muscles. This prompts the body to recruit more muscle fibers, especially those responsible for generating power and force. BFR is particularly valuable for individuals recovering from surgery, dealing with injuries, or unable to lift heavy loads, as it helps accelerate recovery and prevent muscle atrophy—without placing excessive strain on healing tissues.
How Does Blood Flow Restriction (BFR) Training Work?
Blood Flow Restriction (BFR) training works by partially restricting blood flow to a limb—allowing arterial blood to enter but limiting venous blood return. This creates a hypoxic (low oxygen) environment within the muscle, reducing the oxygen supply to working muscles. As a result, fatigue accelerates, and greater muscle fiber recruitment occurs, leading to a "muscle pump."
The "muscle pump" refers to the cellular swelling that happens during BFR, which further contributes to hypertrophy (muscle growth). When the pressure from the cuffs is released, blood rushes back into the muscle, bringing essential nutrients that support recovery and growth.
Additionally, BFR triggers a buildup of metabolic byproducts like hydrogen ions and lactate. This metabolic stress leads to cellular swelling and signals the body to increase muscle protein synthesis. The process is supported by the release of hormones such as growth hormone (GH), insulin-like growth factor-1 (IGF-1), and testosterone—all of which promote muscle growth.
By limiting blood flow, BFR prompts the body to recruit more muscle fibers—particularly the fast-twitch fibers responsible for producing power and force. This is good for individuals who can't yet handle heavy weights, as it stimulates maximal muscle engagement with submaximal loads.
BFR training is also gaining popularity for one of the main reasons people seek our services—pain relief. Recent research, though with a relatively small sample size, has shown that BFR can help improve pain tolerance during exercise, potentially due to the release of natural opioids like beta-endorphins. One study found that pain pressure thresholds in subjects who exercised with BFR cuffs were significantly higher than when those same subjects exercised at the same intensity without BFR cuffs. This suggests that BFR training may enhance pain relief during exercise more effectively than traditional methods. While more research is needed, many patients report experiencing less pain during BFR-based rehabilitation compared to exercises without it. Since higher loads might aggravate already irritable tissues, the low-load nature of BFR training makes it an appealing option.
How Do Muscles Get Stronger?
Before diving deeper into BFR, let's start with a fundamental concept: how muscles grow. Muscle adaptation occurs through neural, mechanical, and metabolic pathways, all contributing to increased strength and size.
These mechanisms require adequate load and volume.
The loading recommendations are typically prescribed along what is known as the "repetition continuum," or the "strength-endurance continuum." This concept proposes that the number of repetitions performed at a given magnitude of load will result in specific adaptations:
Strength Gains: A low repetition scheme with heavy loads (from 1 to 5 repetitions per set with 80% to 100% of your one-repetition maximum (1RM)) optimizes increases in strength.
Hypertrophy (Muscle Growth): A moderate repetition scheme with moderate loads (from 8 to 12 repetitions per set with 60% to 80% of 1RM) optimizes hypertrophic gains.
Muscular Endurance: A high repetition scheme with light loads (15 or more repetitions per set with loads below 60% of 1RM) optimizes improvements in local muscular endurance.
Repetition Continuum
The takeaway? Moderate to heavy loads (>%60 of 1RM) are essential for muscle growth and strength. But what happens when lifting heavy weights isn't appropriate—like right after knee surgery? This is where BFR training comes into play.
BFR in Action: How We Use It After Knee Surgery
After knee surgeries, patients commonly experience muscle atrophy and weakness, especially in the quadriceps. Quadriceps weakness can be as high as 30% and persist for years after surgery. This is directly linked to poorer patient-reported outcomes, decreased functional performance, delayed return to sport, and an increased risk of knee injury.
In light of that information, early strengthening is essential, BUT we must limit mechanical stress on the knee joint during the initial stages of recovery—meaning heavy loads aren't ideal for healing tissue. This is where BFR training shines. As an excellent rehabilitation tool, we use low-load BFR with our post-op patients to increase quadriceps strength and mass while minimizing knee pain and ensuring the protection of healing tissues during the early to mid phases of their rehab journey. BFR allows effective strengthening while minimizing stress on the healing tissues, making it a valuable component of post-surgical rehabilitation.
We typically start using BFR around two weeks after surgery. To allow the safe use of strengthening muscles without putting undue strain on the tissues. We use training loads that are typically 20-30% of your one-repetition maximum (1RM) with higher repetitions (15-30 reps per set).
Our protocol typically includes:
Sets and Reps: 4 sets following a 30-15-15-15 rep scheme
Load: 20-30% of 1RM
BFR Pressure: 80% of Limb Occlusion Pressure (LOP)
Frequency: 2-3 sessions per week
There are many exercises to perform with BFR after knee surgery but some common exercises include quad sets, knee extensions, straight leg raises, bridges, calf raises, and squats. We often use BFR cuffs on both legs to promote overall muscle activation. We typically perform 4-5 of these exercises in a given training session and perform these exercises at the end of the session.
How Long Do We Use BFR?
In knee rehab, we generally use BFR for 6-12 weeks post-op, when patients are still limited by pain or their ability to handle heavier loads. Once patients can tolerate weights greater than 70% of their 1RM without excessive pain or swelling, we discontinue BFR.
Is BFR Safe?
It’s important to note that anything can be unsafe in the wrong hands when used inappropriately, or in the wrong population. However, BFR training is safe. BFR has been used in a variety of musculoskeletal pathologies and to date, has not resulted in serious adverse events for those who don’t have contraindications to BFR training. Additionally, research shows the chance of blood clots or DVT is extremely low.
The contraindications to BFR training are centered around those with vascular insufficiencies or cardiac implications. People with hypertension, diabetes, a history of stroke or DVT, cardiac disease, active infections, pregnancy, clotting disorders, or other vascular insufficiencies (like varicose veins) are contraindications.
Some side effects can occur with BFR training which includes: delayed onset muscle soreness, short-lived numbness, bruising, and skin abrasions.
Safety precautions must be followed, including:
Medical screening
Blood pressure checks
Correct protocols based on limb occlusion pressure (LOP)
Application by trained professionals using validated equipment (avoid using straps or pressure based solely on leg size)
Closing Thoughts
You can for sure receive quality rehab without using blood flow restriction. However, this type of training can be a powerful tool for recovery from knee surgery. While it’s not a replacement for progressive overload in the long run, BFR allows us to safely build muscle early in the rehab process. When the patient can’t safely load their system mechanically, we can use BFR to load their system metabolically. This can be surgeon-dependent, but we typically like to start as early as two weeks post-op and continue for up to 6-12 weeks. If you’re interested in learning more or want to work with us, contact us to speak with one of our expert physical therapists.
Disclaimer
All FHPT blog and article material is intended for educational purposes only. The content provided is based on general information and is within the scope of practice of physical therapists in the state of Louisiana. It should not be interpreted as medical advice, diagnosis, or treatment recommendations. Individual results may vary, and the information shared is not intended to substitute for professional medical consultation, diagnosis, or treatment. Before making any decisions regarding your health, wellness, or treatment, it is essential to consult with a qualified healthcare provider. Fulco & Hall Performance & Therapy (FHPT) assumes no responsibility or liability for any outcomes resulting from the use or application of the information provided.
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