The complete guide to Blood Flow Restriction Training!

There has been a lot of hype around Blood Flow Restriction Training in recent years, but many people still don't know what it's all about. This comprehensive guide will introduce you to the details of this innovative training system.

Over the last two years, Blood Flow Restriction Training (BFR for short) has become increasingly popular in weight rooms around the world, but that doesn't mean it's perfectly understood by everyone. When you consider the different names (occlusion training, hypoxia training, KAATSU) by which it is known, the different styles of training (bands, cuffs and bandages) and the different goals associated with this training, the confusion seems to increase rather than decrease.

After years of researching this topic and studying it in the lab, I believe it has a lot to offer a wide range of people who want to build muscle, increase their training frequency and try something new in their workouts.

Scientists have been looking at the details of BFR training for decades, but there is also fascinating new research on the subject all the time. That's why I'm dedicating a separate guide to BFR training to answer the most common questions about this style of training. My goal is to make sure that in the future you don't have another excuse for not knowing what's going on in this exciting part of the training world.

F. What is Blood Flow Restriction training and how does it work?

BFR training involves wrapping the upper part of a leg or arm with a device such as a cuff, KAATSU bandage or even a knee bandage to restrict blood flow out of the trained muscle. During a properly performed BFR workout, blood can travel to the muscle via arterial blood flow, but because the veins are constricted by the bandage, the blood is partially prevented from leaving the muscle.

This arrangement allows the muscles to swell, which is the first mechanism of muscle growth (1). Restriction of blood flow also causes an accumulation of metabolic products such as lactic acid, which has been shown to directly stimulate muscle growth. And the direct exhaustion inflicted on the muscles forces the nervous system to recruit the largest, fast-contracting muscle fibers, which have the greatest capacity for growth (2).

Is a warm-up or warm-down necessary?

In general, a BFR workout is performed at intensities normally used for warm-up sets, which are in the range of 30 to 50% of the maximum weight for one repetition (1 RM weight). Therefore, I would only recommend a short, general warm-up of about 5 minutes duration, such as walking or light cycling, followed by 15 repetitions without bandages with the weight you are using for your first BFR set.

What should I use to wrap my limbs and how tightly should I wrap them?

Traditionally, BFR training involves the use of a special inflatable cuff known as a KAATSU cuff to restrict venous blood flow. The advantage of such a cuff is that you can precisely control the pressure and replicate it exactly during all training sessions.

Unfortunately, most exercisers do not have access to such fancy equipment, which led our lab to conduct extensive research into the practical use of BFR training. Such BFR training involves the use of an elastic bandage to restrict blood flow. In studies, we have used knee and elbow bandages, but elastic cotton bandages can also be used.

Although this is practical, one concern is that blood flow from both veins and arteries may be too restricted (3). Arteries carry blood to the muscles, while veins carry blood away from the muscles. To achieve the maximum swelling response, blood should get to the muscle and stay there.

It is important to understand this because all the potential disadvantages of BFR training come from the fact that both veins and arteries are completely tied off. In fact, there is evidence that wrapping too tightly, causing arterial occlusion, could actually reduce muscle growth in the affected area (4).

To address this issue, our lab looked at the effects of perceived pressure on blood flow during BRF exercise. We used knee bandages on the legs and used a perceived pressure of 0, 7 and 10 out of 10 in subjects, where 10 corresponds to the strongest pressure that can be achieved by the bandaging. We found that in the legs, BFR training with a perceived pressure of 7 out of 10 resulted in venous restriction but not arterial restriction. We also found that when subjects exercised at this pressure, they experienced a dramatic increase in muscle swelling, recruited more muscle, and experienced a greater amount of metabolic stress.

However, it is important to note that at a perceived pressure of 10 out of 10, both venous and arterial blood flow came to a complete stop.

Where should I bandage and how far should I bandage?

Scientific research has shown that a narrower cuff width (5 to 8 centimeters) reduces the risk of arterial occlusion compared to the use of wider cuffs (13+ centimeters). For this reason, I also recommend wrapping your arms and legs with multiple layers at the top instead of wrapping your limbs lengthwise in a spiral.

In addition, the mass of your arms and legs will also determine how tightly you should wrap them. Scientific research shows that the risk of arterial occlusion is greater with thinner limbs. For most people, I would recommend wrapping the legs with a perceived pressure of 7 out of 10 and wrapping the arms with a pressure of 6 out of 10.

Where should you wrap:

• Wrap arms and legs at the top only
• You can wrap your arms for a shoulder or chest workout and your legs for a gluteus workout. Just use common sense and keep the weights light.

Where not to wrap:

• Don't wrap your legs at knee level for your calf workout and don't wrap your arms at the elbow area for your forearm workout. In this case too, wrap your arms and legs as high up as possible.
• Do not wrap your limbs when using weights above 50% of your 1RM weight. 20 to 40% of this weight is the optimal range.

How should you wrap?

• Use a narrow bandage (5 to 9 centimeters) to minimize the risk of occlusion of the arteries.
• Use a tourniquet or elbow/knee bandages.

How not to wrap:

• Do not use wide bandages (>10 centimeters.
• Do not wrap your limbs in a spiral, which would cover a large area of the arm/leg with the bandage.

How tightly should you wrap your limbs?

• Aim for a pressure of 6 to 7 on a scale of 1 to 10.
• If in doubt, wrap your limb a little less tightly rather than too tightly. Occlusions of 40 and 80% have been shown to produce the same strength and muscle gains.
• Avoid wrapping your limbs so tightly that you feel numbness.
• Avoid wrapping your limbs so tightly that you have trouble performing more than a few repetitions. High reps (at least 15) are the norm for a BFR workout!

How heavy should I train during a BFR workout?

The primary benefit of BFR training is that you can increase your muscle mass at very low intensities. In fact, some research has shown that people who simply ran with BFR bands at low intensities were able to increase their muscle mass (5). However, we have found that resistance training results in greater muscle and strength benefits than simply walking (1).

So how hard should you train? Scientific research shows that muscle gains are possible with as little as 20% of 1RM weight. In this case, however, muscle growth will primarily come from growth in the slow-contracting muscle fibers rather than the fast-contracting muscle fibers.

One study compared moderate BFR training with 20, 30 and 40% of the 1RM weight of the test subjects. This study came to the conclusion that the fast contracting muscle fibers were not maximally recruited up to a weight of 40% of the 1RM weight. However, other studies have shown that BFR training at 80% of 1RM weight does not increase muscle fiber recruitment compared to BFR training at 40% of 1RM weight (6). In addition to this, there was less metabolic stress.

Taking this into account, for maximum muscle growth, BFR training should probably be performed at around 40% and no more than 50% of 1RM weight. However, if you are using BFR training as active recovery training, then training at 20 to 30% of your 1RM weight will still likely result in benefits in the slow contracting muscle fibers. This could be important as it is often difficult to achieve hypertrophy of these fibers.

Is it better to wrap the bandages a little too loosely or a little too tightly?

Dr. Carlos Ugrinowitsch and his colleagues conducted a study that investigated this issue (7). Ugrinowitsch was one of the first scientists to investigate the molecular mechanisms of BFR training.

In this study, the scientists placed a cuff and inflated it to either 40 or 80% of the pressure required to cause occlusion of the arteries. From a practical point of view, this would correspond to a perceived pressure of 4 or 8 on a scale of 1 to 10. Then they had the subjects perform a BFR workout with 20 or 40% of their 1RM weight.

Here's the cool result: a pressure of 40 and a pressure of 80% of an occlusion of the arteries produced the same gains in strength and muscle mass when training at 40% of 1RM weight. So the clear message is that it's better to apply the bandages a little too loosely than too tightly.

As long as you use a moderate pressure and an intensity of 40 to 50% of your 1RM weight, you should be in the right range. However, if you apply the supports too tightly, there is a risk of complete arterial occlusion (3).

Are there positive effects on muscles whose venous blood flow is not restricted?

Many people think that BFR training is only for arms and legs, but can it also be used for chest, back and gluteus? The short answer is yes - there is increased muscle activation in the muscles where venous blood flow has not been restricted.

How can this be? Simply put, by bandaging the arms and legs, the nervous system senses extreme fatigue in the limbs. Because of this, your body will do whatever it can to maintain strength and prevent failure. To compensate for this fatigue, your nervous system recruits more muscles from other areas.

For example, research published in the journal Clinical Physiology and Functional Imaging found that restricting blood flow to the arms and performing bench presses resulted in a 16% increase in muscle activation in the pectoral muscles (8). Research has also shown that individuals who train their legs with a BFT workout and then perform an arm workout achieve greater muscle growth in the arms than when they train both muscle groups separately (9).

Although the exact reasons for this are still unclear, it is possible that growth factors released during BFR training and/or circulating metabolites are able to increase the metabolic effects in the arms that were not trained with BFR training. Therefore, training the chest, back or gluteus with BFR bandages on the arms or legs could also have positive effects on the growth of these muscles.

What are the recovery requirements of BFR training compared to other forms of isolation training?

Our laboratory was the first to investigate the effects of BFR training on recovery requirements compared to low-intensity non-BFR training (3). We found that even though BFR training induced greater fatigue immediately after exercise, there was no increase in muscle damage or decrease in strength 24 hours later - which is quite impressive!

As this type of training has low recovery requirements compared to high-intensity training, it is likely that it can be performed every other day, but probably not more often. We found that 2 to 3 days of BFR training was best for gains in strength and muscle (1).

BFR training makes it necessary to train with very high repetitions (15 to 30 repetitions). If you are not used to such high repetitions, this alone can lead to a certain amount of muscle damage (10). However, it is unlikely that the bandages themselves will increase the recovery requirements.

So if you are just starting out with BFR training and are not used to metabolically demanding training, I would recommend using this type of training only twice a week at first. As soon as you have adapted to this, you can use it up to three times a week for muscle groups that are lagging behind in their development.

Which is better: doing a pure BFR phase for one muscle group or alternating strength, hypertrophy and BFR days?

My student Ryan Lowery and I conducted a study on this topic a few years ago (11). We found that periodizing with BFR training for a few weeks followed by high-intensity training resulted in a lot of muscle growth.

The rate at which you periodize should depend on your training status (12). Based on research on this topic, I would say that if you are just starting out with BFR training, alternating every few weeks will work just as well as alternating every few days (13).

As your training experience increases, I would recommend a program where you alternate your training style every few workouts.

Is it necessary or advisable to go to muscle failure in a BFR workout?

A BFR workout takes advantage of a primary growth mechanism by activating the larger, fast-twitch muscle fibers. Fast-twitch muscle fibers are recruited either through heavy resistance or exhaustion. Scientific research shows that the closer you get to the point of muscle failure, the greater the activation of fast-twitch fibers (14, 15). Thus, muscle failure during low-intensity training is likely a prerequisite for optimal muscle fiber recruitment when using BFR training.

However, training to muscle failure can be very exhausting for your nervous system (16). Therefore, I would recommend that you save training to muscle failure until the last set, rather than going to muscle failure on all BFR sets. You could start with 30 reps at 40% of your 1RM weight, pause for 30 seconds, do 15 reps, repeat this and go to muscle failure at the end.

I'm not a bodybuilder, just someone who wants to build shapely arms. Are 2 to 3 BFR workouts per week enough for serious results?

Fortunately, plenty of research has been done with non-bodybuilders (1). In these populations, we have found that 2 to 3 sessions of BFR training per week is perfect.

Should I just do a few exercises or a full BFR training session?

While most studies have looked at BFT training on its own, our lab teamed up with Bill Campbell's lab for 2 studies to examine the effects of BFT training in combination with high-intensity resistance training (2, 17).

In both studies, we found that BFR training in combination with high-intensity training is an effective way to increase muscle mass. Interestingly, in the second study, we replaced 60% of high-intensity training with BFR training and found that subjects were still able to increase their muscle mass as effectively as with 100% high-intensity training.

What does this mean for you? Firstly, BFR training can increase muscle growth both on its own and in combination with heavy training. Secondly, because BFR training causes very little muscle damage, it can be used as a replacement for up to 60% of high-intensity training during unloading phases. This gives athletes the opportunity to continue to progress while giving their joints and/or injuries the opportunity to heal.

I usually recommend using a BFR workout as a light recovery day, as a method to unload and heal, or as a method to give the muscle the rest at the end of the training session. The latter method is supported by studies showing that a heavy workout that includes a set of very light reps at the end, performed at 50% of your 1RM weight, can increase hypertrophy and strength compared to high-intensity training alone (18).

To use BFR as a workout finisher, you should perform an isolation exercise such as curls or leg extensions for 4 sets of 30, 15, 15, 15 repetitions with 3 seconds rest between sets using 20 to 40% of your 1RM weight. Do this one to three times a week.

Is BFR training safe for my cardiovascular system?

Before beginning any exercise program, it is important that you get clearance from your physician. All recommendations given in this article apply to healthy adults with no pre-existing medical conditions who are already performing high-intensity resistance training. Also, because the safety and potential benefits of BFR training have been studied in a clinical setting, it is beyond the focus of this article. However, I can address how BFR training compares to traditional resistance training in terms of the cardiovascular and nervous system.

It has been suggested by some that restricting blood flow could cause damage to the veins and ultimately affect long-term blood flow. However, scientific research shows that even when blood flow is restricted during exercise, over time (4 weeks) there is improved blood flow compared to traditional resistance training alone (19).

In addition, it has been shown that average arterial blood pressure more than doubles during heavy resistance training (80 to 100% of 1RM weight), while heart rate reaches maximal levels (20, 21). Studies with low-intensity BFR training also show an increase in blood pressure and heart rate, but these increases are only 11 to 13% (22). Thus, traditional resistance training results in much higher blood pressure and heart rate.

What is the reason for these drastic differences? You should know that when performing low-intensity BFR training, studies have generated pressure around the limbs ranging from 50 to 230 mmHg (23). During maximal, high-intensity exercise, however, the muscles contract so hard that intramuscular pressure reaches an average of 500 mmHg, which can rise to over 1000 mmHg (24, 25).

In comparison, complete arterial restriction occurs in a range of 140 to 235 mmHg external pressure (23). It has also been shown that complete blockage of blood flow during traditional resistance training occurs at 50 to 64% of an individual's 1RM weight.

It is important to recognize that traditional resistance training results in vascular occlusion even at moderate force contractions. Thus, BFR training only mimics this response at lower intensities.

What about blood clots?

Other concerns about BFR training are related to the worry that it could cause thrombosis. Thrombosis is the formation of blood clots within a blood vessel that obstructs blood flow. The three primary factors thought to be responsible for this are a predisposition to form blood clots, damage to the blood vessels and occlusion of the blood flow.

It is important to know that the formation of a blood clot is caused by an imbalance between coagulation processes and fibrinolytic processes (breakdown of coagulation products). Research using low-intensity BFR training has shown that this type of activity does not increase blood clotting, but may actually increase the breakdown of blood clots (22, 26, 27). So based on what we know, BFR training seems to be perfectly safe and harmless.

However, it is definitely important that you do not completely cut off arterial blood flow during BFR training. Remember what I said earlier: it has been shown that 40% occlusion has the same benefits as 80% occlusion, so there is no harm in using a little less pressure rather than too much.

Is BFR training safe for the nervous system?

This is a frequently asked question. In a study published in the paper Metabolism, a small percentage of BFR training sessions resulted in numbness in the corresponding arm or leg (28). This suggested that BFT training may be too demanding on the nervous system. However, further research looking at nerve conduction velocity showed no changes after 4 weeks of BFR training at 30% of 1RM weight (26).

To me, this suggests that several of the BFR workouts that resulted in numbness were likely the result of incorrect tying technique. Learn how to do it right and you should have nothing to fear.

References

1. Loenneke JP, Abe T, Wilson JM, Ugrinowitsch C, & Bemben MG (2012) Blood flow restriction: how does it work? Frontiers in Physiology, 3, 392.
2. Loenneke JP, Wilson GJ, & Wilson JM (2010) A mechanistic approach to blood flow occlusion. International Journal of Sports Medicine, 31(1), 1-4.
3. Wilson, J. M., Lowery, R. P., Joy, J. M., Loenneke, J. P., & Naimo, M. A. (2013). Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage. The Journal of Strength & Conditioning Research, 27(11), 3068-3075.
4. Kacin, A., & Strazar, K. (2011). Frequent low-load ischemic resistance exercise to failure enhances muscle oxygen delivery and endurance capacity. Scandinavian Journal of Medicine & Science in Sports, 21(6), e231-e241.
5. Fry, C. S., Glynn, E. L., Drummond, M. J., Timmerman, K. L., Fujita, S., Abe, T., ... & Rasmussen, B. B. (2010). Blood flow restriction exercise stimulates mTORC1 signaling and muscle protein synthesis in older men. Journal of Applied Physiology, 108(5), 1199-1209.
6. Takarada, Y., Takazawa, H., Sato, Y., Takebayashi, S., Tanaka, Y., & Ishii, N. (2000). Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. Journal of Applied Physiology, 88(6), 2097-2106.
7. Lixandrão, M. E., Ugrinowitsch, C., Laurentino, G., Libardi, C. A., Aihara, A. Y., Cardoso, F. N., ... & Roschel, H. (2015). Effects of exercise intensity and occlusion pressure after 12 weeks of resistance training with blood-flow restriction. European Journal of Applied Physiology, 1-10.
8. Yasuda, T., Fujita, S., Ogasawara, R., Sato, Y., & Abe, T. (2010). Effects of low-intensity bench press training with restricted arm muscle blood flow on chest muscle hypertrophy: a pilot study. Clinical Physiology and Functional Imaging, 30(5), 338-343.
9. Madarame, H., Neya, M., Ochi, E., Nakazato, K., Sato, Y., & Ishii, N. (2008). Cross-transfer effects of resistance training with blood flow restriction. Medicine and Science in Sports and Exercise, 40(2), 258.
10. Wernbom, M., Paulsen, G., Nilsen, T. S., Hisdal, J., & Raastad, T. (2012). Contractile function and sarcolemmal permeability after acute low-load resistance exercise with blood flow restriction. European Journal of Applied Physiology, 112(6), 2051-2063.
11. Lowery, R. P., Joy, J. M., Loenneke, J. P., Souza, E. O., Machado, M., Dudeck, J. E., & Wilson, J. M. (2014). Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training program. Clinical Physiology and Functional Imaging, 34(4), 317-321.
12. Monteiro, A. G., Aoki, M. S., Evangelista, A. L., Alveno, D. A., Monteiro, G. A., da Cruz Picarro, I., & Ugrinowitsch, C. (2009). Nonlinear periodization maximizes strength gains in split resistance training routines. The Journal of Strength & Conditioning Research, 23(4), 1321-1326.
13. Buford, T. W., Rossi, S. J., Smith, D. B., & Warren, A. J. (2007). A comparison of periodization models during nine weeks with equated volume and intensity for strength. The Journal of Strength & Conditioning Research, 21(4), 1245-1250.
14. Fallentin, N., Jørgensen, K., & Simonsen, E. B. (1993). Motor unit recruitment during prolonged isometric contractions. European Journal of Applied Physiology and Occupational Physiology, 67(4), 335-341.
15. Garland, S. J., Enoka, R. M., Serrano, L. P., & Robinson, G. A. (1994). Behavior of motor units in human biceps brachii during a submaximal fatiguing contraction. Journal of Applied Physiology, 76(6), 2411-2419.
16. Ahtiainen, J. P., Pakarinen, A., Kraemer, W. J., & Häkkinen, K. (2003). Acute hormonal and neuromuscular responses and recovery to forced vs maximum repetitions multiple resistance exercises. International Journal of Sports Medicine, 24(6), 410-418.
17. O'Halloran, J., Campbell, B., Martinez, N., O'Connor, S., Fuentes, J., Theilen, N., ... & Kilpatrick, M. (2014). The effects of practical vascular blood flow restriction training on skeletal muscle hypertrophy. Journal of the International Society of Sports Nutrition, 11(Suppl 1), P18.
18. Goto, K., Nagasawa, M., Yanagisawa, O., Kizuka, T., ISHII, N., & Takamatsu, K. (2004). Muscular adaptations to combinations of high-and low-intensity resistance exercises.The Journal of Strength & Conditioning Research, 18(4), 730-737.
19. Patterson, S. D., & Ferguson, R. A. (2010). Increase in calf post-occlusive blood flow and strength following short-term resistance exercise training with blood flow restriction in young women. European Journal of Applied Physiology, 108(5), 1025-1033.
20. MacDougall, J. D., Tuxen, D. S. D. G., Sale, D. G., Moroz, J. R., & Sutton, J. R. (1985). Arterial blood pressure response to heavy resistance exercise. Journal of Applied Physiology, 58(3), 785-790.
21. MacDougall, J. D., McKelvie, R. S., Moroz, D. E., Sale, D. G., McCartney, N., & Buick, F. (1992). Factors affecting blood pressure during heavy weight lifting and static contractions. Journal of Applied Physiology, 73(4), 1590-1597.
22. Takano, H., Morita, T., Iida, H., Asada, K. I., Kato, M., Uno, K., ... & Nakajima, T. (2005). Hemodynamic and hormonal responses to a short-term low-intensity resistance exercise with the reduction of muscle blood flow. European Journal of Applied Physiology, 95(1), 65-73.
23. Loenneke, J. P., Wilson, J. M., Marín, P. J., Zourdos, M. C., & Bemben, M. G. (2012). Low intensity blood flow restriction training: a meta-analysis. European Journal of Applied Physiology, 112(5), 1849-1859
24. Sylvest, O., & Hvid, N. (1959). Pressure measurements in human striated muscles during contraction. Acta Rheumatologica Scandinavica, 5(1-4), 216-222.
25. Sylvest, O., & Hvid, N. (1959). Pressure measurements in human striated muscles during contraction. Acta Rheumatologica Scandinavica, 5(1-4), 216-222.
26. Clark, B. C., Manini, T. M., Hoffman, R. L., Williams, P. S., Guiler, M. K., Knutson, M. J., ... & Kushnick, M. R. (2011). Relative safety of 4 weeks of blood flow-restricted resistance exercise in young, healthy adults. Scandinavian Journal of Medicine & Science in Sports, 21(5), 653-662.
27. Fry, C. S., Glynn, E. L., Drummond, M. J., Timmerman, K. L., Fujita, S., Abe, T., ... & Rasmussen, B. B. (2010). Blood flow restriction exercise stimulates mTORC1 signaling and muscle protein synthesis in older men. Journal of Applied Physiology, 108(5), 1199-1209.
28. Yasuda, T., Abe, T., Brechue, W. F., Iida, H., Takano, H., Meguro, K., ... & Nakajima, T. (2010). Venous blood gas and metabolite response to low-intensity muscle contractions with external limb compression. Metabolism, 59(10), 1510-1519.

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Jacob Wilson, Ph.D.