What is Blood Flow Restriction Training?

With blood flow restriction training skyrocketing in popularity, you’ve undoubtedly either heard the term more often recently, or seen some of your favorite athletes training with cuffs around their arms or legs. You’ve probably heard people talk about the benefits as well – but what is it exactly? By the end of this article, you’ll understand what BFR training is, how it works, and what the exact benefits are. We’ll break down the science in a digestible way that’s simple and actionable.

Blood flow restriction training is what it sounds like (sort of). It involves putting a cuff or tourniquet around either the top of your arm (just beneath your delts) or the top of your leg (just beneath your glutes) and engaging in some form of training – we’ll discuss what types of training for different goals later on in this article. This cuff partially restricts blood flow. Remember, we always have blood flow traveling from the heart to our limbs (arterial blood flow) and blood traveling from the limbs back to the heart (venous blood flow).

Arterial = TO the limbs FROM the heart
Venous = FROM the limbs TO the heart

BFR training only fully restricts venous flow. It does not fully restrict arterial flow in the way a tourniquet would. If you’ve ever had a good resistance training session, you’ve actually experienced this to some degree – even without occlusion bands. You know the infamous “pump”? Let’s take bicep curls as an example. If you complete several sets of curls, particularly with minimal rest between the sets, you’ll notice your biceps appear larger and more “full”. When a muscle is being challenged, it requires more oxygen and nutrients to power it, so the heart pumps faster and delivers that necessary blood to the biceps. The blood is coming to the muscle (arterial, remember?) faster than it’s leaving the muscle (venous), so a sort of “pooling” happens in the muscle. This physiological response is known to be beneficial in a number of ways, and blood flow restriction bands allow you to achieve it faster + to a greater degree.

Now that you know what’s happening in the body during BFR training, the next logical question is why does it work? Why does partially restricting flow during training have such strong benefits? Some of the mechanisms of BFR are still unknown (we know it works, we just can’t fully explain why). In a bit, we’ll discuss some of the science behind what we know (and what we hypothesize). 

First, it’s important to understand what the actual benefits are.

The Benefits of BFR Training

There is now a mountain of research backing the benefits of BFR training. Though there are likely benefits that are still unknown, we’ll focus on the three that have been consistently demonstrated in research.

  • Increased strength
  • Increased muscle mass
  • Increased aerobic capacity (oxygen delivery to muscle)

    BFR Training for Strength & Hypertrophy

    There’s a nice caveat to the above benefits though. We know that resistance training alone improves strength and muscle mass, so why bother with BFR? BFR training allows you to achieve similar strength and hypertrophy gains (muscle growth) as traditional resistance training at significantly lower loads (weight). This is particularly advantageous in several circumstances:

    • While injured (and can’t lift heavy)
    • In circumstances where you want to gain or maintain muscle mass without taxing the body by lifting heavy
    • During times where you have limited access to weights

    When resistance training, the weight must be heavy enough to stimulate muscle growth. Let’s take squats for example. If you’re capable of squatting 405 pounds, it’s highly unlikely that loading the bar up to 95 pounds and squatting away repeatedly will lead to any muscle growth – the weight is just too light to send a stimulus to the muscle that it needs to grow.

    Enter BFR Training.

    BFR training has repeatedly shown in research to cause muscle and strength gains at loads as low as 20% of one’s one rep max. Back to the 405-pound squat example, 95 pounds would be just above 20%. So, if you could achieve similar strength and hypertrophy gains squatting sets of 95 pounds versus weights up closer towards your one rep max (let’s say 365 pounds), I’m sure you can imagine the use cases here.

    BFR training for joint pain

    We’re made of more than just muscle obviously - we have joints, tendons, and connective tissue. Sometimes our muscles feel great, but our joints are struggling. Joints and connective tissue take longer to recover than muscle. If you’ve ever experienced this joint pain, you know how unappealing it sounds to throw heavy weight on your back and start cranking out reps. Blood flow restriction bands afford you the ability to not sacrifice your gains when the joints aren’t up for heavy loads.

    BFR trainning with weights

    BFR Training for Recovery

    Our bodies only have a certain amount of resources available to recover from training. Think of it like a gas tank – training will pull gas from that tank, and you can’t just keep pulling gas out indefinitely. Of course, proper sleep, nutrition, hydration, and stress management are the pillars of recovery. Right within that list though is proper programming. This means finding that delicate balance of pushing your body past new thresholds so it can continue to adapt without overcooking yourself.  

    Let’s look at American football players for example. It is quite common for these athletes to lose a considerable amount of muscle during the season. This is because their training focus shifts to on field work and game preparation. During the offseason, there is plenty more time and energy to devote to resistance training since the athletes don’t need to be at full capacity by gameday, and they have less on field work to perform.

    We know that losing muscle not only hinders performance, but also increases the likelihood of injury in most cases. This is a bit of a catch 22, because these athletes don’t have the resources to recover from the increased practice and skill work and still be ready to go by Saturday (or Sunday) if they continue resistance training at a high level. Constantly loading heavy weights on them would overdraw their gas tank. BFR is the “magic” alternative, as it allows them to maintain that muscle without a major energy cost. Back to the joint / connective tissue example as well, athlete’s joints are often toast after gameday, so BFR can be a hero in that department as well.

    So, in regard to BFR as a recovery tool, you could almost think of it as a means to continue your training at a “cheaper” energy cost, indirectly benefiting your recovery.

    There are also some direct recovery benefits of BFR. We’ve all heard the term “lactic acid” (or felt its effect in training). When we engage in BFR training, we see a large increase in lactate production in a shorter time frame than without BFR cuffs applied. This increase in lactate stimulates the release of other molecules and proteins that aid the recovery process, such as Growth Hormone (GH). Growth hormone promotes collagen synthesis in muscles, tendons, ligaments, and bone, which creates a favorable recovery environment.

    BFR Training for Aerobic Capacity

    Perhaps one of the most incredible benefits of BFR training is how it can enhance aerobic capacity. Before we dive into the evidence here, let’s first define aerobic capacity.

    Aerobic capacity defined simply is just your body’s ability to deliver oxygen to the working muscles + the muscle’s ability to utilize that oxygen. Blood flow restriction training can lead to significant increases in the body’s ability to perform both of those tasks.

    This was demonstrated powerfully in a study by Alan Kacin and Klemen Strazar where the efficacy of BFR bands was put to the test with ten healthy males. The interesting piece about this study is that each subject only used a BFR cuff on one leg – this allows us to largely rule out different physiological effects as “genetics” since each of the subjects effectively acted as their own control.

    They performed knee extension exercises for four weeks (four sessions per week). A BFR cuff was only applied to one leg. The load was kept at 15% of their one rep maximum. At the end of the four weeks, the number of reps the subjects could complete before muscular failure increased by 36% in the non-BFR limb and 63% in the leg that was trained with BFR. That’s a 75% increase in reps to failure achieved by BFR!

    Why is this?

    Similar to how improving strength without BFR cuffs requires heavy loads, improving aerobic capacity without BFR cuffs requires high training intensity. BFR cuffs, however, create a hypoxic environment (low muscle oxygen availability), even at lower training intensities. This forces the body to adapt and become more efficient both at delivering oxygen to working muscles and utilizing that oxygen.

    So now we know what BFR training is and what the benefits are, but how and why does it work? What’s actually happening physiologically that leads to these incredible fitness improvements?

    The Mechanisms of Blood Flow Restriction Training: Why Does BFR Work?

    We mentioned earlier in this article that many of the mechanisms of BFR are still unknown. In other words, we know it works, but can’t fully explain how it works so well. There are some known and some proposed mechanisms that likely lead to the strength, hypertrophy, and aerobic capacity increases. We’ll list them below.

    Metabolite Accumulation – Metabolites are substances that are formed during or that are necessary for metabolism. These metabolites are increased during BFR training from the lack of blood clearance out of the muscle due to the occlusion of the venous structures. This is anabolic in nature, ultimately contributing to muscle growth.

    Hypoxic Environment – As discussed above, the super-imposed hypoxic (low muscle oxygen availability) environment seems to lead to serious improvements in aerobic capacity.

    There are other potential secondary mechanisms, but for the purpose of this article, we’ll stick to the above two.

    There are obviously some phenomenal fitness gains to be made from BFR training, but should anyone not engage in it? Are there any risks?

    BFR Training Risks and Contraindications

    BFR Training is generally considered safe for most people and does not have absolute contraindications. However, all patients should be assessed for risk prior to BFR application. Special care should be taken in the following groups of patients:

    • Severe peripheral vascular disease
    • Sickle cell disease
    • Severe crush injury
    • Diabetic neuropathic patients
    • Patients with history of deep vein thrombosis and pulmonary embolism

    BFR Bands
    How to Get Started BFR Training

    SAGA produces the world’s first Bluetooth-enabled smart blood flow restriction bands. What does that mean exactly? Let’s discuss the “smart” piece first. Remember how we mentioned that BFR training partially restricts venous blood flow? By “partial” there’s actually a specific science here. Much of the research occludes the arms at 50% and legs at 80%. You wouldn’t want to just arbitrarily throw a band around your arm or leg without understanding what percentage is being restricted!

    This is where smart BFR technology comes into play. SAGA’s BFR cuffs auto-calibrate to you and then allow you to select what percentage of occlusion you’d like to train at. This allows you to mirror the benefits found in research without the guesswork.

    Second, the Bluetooth piece. SAGA’s cuffs are fully wireless and do not require a manual pump to achieve calibration. The cuffs are controlled via a user-friendly smartphone app, so you can train BFR anywhere.

    Of course, we’re partial to our cuffs, but if you’d like to learn more about them, you can check out our Instagram here or pick up a set (or two) for yourself here.

    Enjoy, and stay strong!