Introduction To Blood Flow Restriction (BFR) Training

“You can get stronger and gain muscle by lifting light weights”  seems like a clickbait-y type of claim, but would you be surprised to learn there’s some legitimate (and not-so legitimate) science to support a training method to do just that?

Enter Blood Flow Restriction Training.  

Blood Flow Restriction (BFR) dates back to the 1960’s, when Dr. Yoshiaki Sato used small rubberized bands as tourniquets at the top of his arms and legs during the limited exercise he could do while recovering from an injury. By reducing the blood flow, he thought, he could stimulate the muscles effectively and not only limit muscle loss, but also speed up his recovery. As the story goes, Dr. Sato reported that his method worked well and subsequently patented it as Kaatsu training.¹ Over the last 20 years or so, BFR has become a popular training method in not only sport, but also in rehabilitation settings. 

If tying off body parts for gains sounds like a good time or you would like to know more about it first, you’re in the right place. In this article, we’ll cover important concepts surrounding BFR like what it is, whether or not it works, and how-to do it. Let’s start out by defining BFR.

What is Blood Flow Restriction (BFR)?

Blood Flow Restriction (BFR) is a training technique that involves restricting venous blood flow from a working muscle while allowing arterial blood flow into the muscle. This is typically achieved using a cuff or band placed around the proximal portion of the limb.

Blood flow starts with the beating heart, which pumps out blood to the organs and tissue through arteries, and then returns to the heart through veins. Blood pressure measures the force of the blood in our arteries when the heart is contracting, e.g. the “systolic” phase of the cardiac cycle (the top number), and the blood’s force in our arteries when the heart is relaxing, e.g. the “diastolic” phase of the cardiac cycle (the “bottom” number). A blood pressure measurement of 120 mmHg / 80 mmHg refers to 120mmHg systolic over 80 mmHg diastolic. The higher pressure in the arteries compared to the veins facilitates flow of blood through the vessels of our body.

Now, suppose you placed a cuff or wrap to your arm or leg with a bit of pressure to squeeze the blood vessels in that limb. If applied tightly enough to squeeze only the veins, but not the arteries, more blood enters the limb than can exit. This causes a bit of a traffic jam in the blood vessels, delaying the oxygen and energy delivery to the working muscle in the occluded limb. This is the technique used with BFR in order to create an environment conducive to increases in muscle size and strength. ^2-11

How Does BFR Work?

Let’s go over the 3 most likely ways BFR has an effect on muscle growth (hypertrophy) and muscle strength.

Metabolic Stress

Metabolic stress  is essentially the accumulation of biochemical byproducts like hydrogen and inorganic phosphate ions, which occurs when some of the energy stores within the muscle get low during exercise. It’s what is most commonly attributed to the “burn” you feel in muscles when they are working.¹⁸ 

In general, anytime muscles are contracting during resistance training, they’re producing these metabolites, making it hard to determine whether metabolites contribute to hypertrophy or if it’s just the mechanical force from muscular contractions. Based on the present data, it appears the majority of muscular hypertrophy is caused by mechanical signals, whereas metabolites may have an indirect role. 

Because low loads are used in BFR, tension in the muscle is not as comparable to that of conventional resistance training and BFR has been shown to cause virtually no muscle damage.²⁰ This actually may be one of the other reasons it works, as muscle hypertrophy, e.g. increased muscle fiber size, occurs when muscle protein synthesis exceeds muscle protein breakdown. In other words, hypertrophy seems to lag until muscle protein breakdown is minimized and muscle protein synthesis predominates. ^37,38

Metabolic stress is one of the likely mechanisms by which BFR works, though it’s not a slam dunk. Existing evidence is conflicting regarding this topic, as there does not seem to be conclusive advantages of using continuous BFR versus intermittent BFR.^5,35,36

Motor Unit Recruitment

A motor unit is the nerve cell and all the muscle cells or fibers it has an effect on. When lifting heavier loads (above 65% of 1 RM), many of these motor units are recruited to help overcome the force required to resist or move the external load. However, with BFR, similar amounts of motor units are recruited with significantly lower loads.^5,21 The ability to recruit more motor units significantly contributes to strength and is the most likely reason for gains in strength seen with the use of BFR. 

Cellular Swelling and Cellular Hypertrophy Signaling

Cell swelling, in the case of BFR, is most likely the result of restricting blood flow out of the limb, causing muscle cells to swell. This swelling is thought to have a potential effect on muscle hypertrophy.^22,23 What is proposed in theory, is that this swelling leads to a number of other cellular mechanisms that are anabolic in nature (muscle growing).^24-26 For a further dive, you can check out this review. Though not clear yet, cell swelling may contribute to the mechanisms leading to increase in muscle size over time.

Hormonal Signaling 

As one small bonus, there are potential hormonal contributions that may be worth mentioning here. For example, there is a significant increase in growth hormone release following BFR²¹, though the impact on hypertrophy is unclear and shouldn’t be considered a primary factor at this time. For now, this is more of an interesting phenomenon but shouldn’t be considered as being a significant contributor to the effects seen with BFR.

How-To Do Blood Flow Restriction Training?

The band or wrap used in BFR training is typically applied as high up on the limb as possible. In research and healthcare settings, a specialized cuff that can measure blood pressure is often used in an effort to reduce the risk of either the cuff being too tight and occluding arterial blood flow which could be harmful, or the cuff being too loose and not delivering the intended result. However, more practical applications can be applied and will be discussed later. It should be noted here that BFR has been shown to be quite safe across different populations, limb locations, and pressures in both relatively short and long-term applications.^12-18

The loads lifted while using BFR are low compared to conventional resistance training. As a general guide, conventional resistance training is performed with loads at or above 60-65% of a 1-repetition-maximum (1RM) for sets of 1- to 20-repetitions, followed by rest periods of 2- to 5-minutes.

In contrast, the most commonly used scheme in BFR is a set of 30 repetitions, followed by 3 sets of 15 reps with 30-60 seconds of rest between sets with loads between 20-30% of 1 RM.^2-3 This protocol is sure to give you a juicy pump. You may feel that you have, for the first time, connected to what the great physique competitors of our era have been chasing and you are now on your war-path to the Olympia stage.

Blood Flow Restriction For Strength Training

If BFR does all this great stuff, then why aren’t we all using it in every training session?  First, a conventional approach to strength training is still going to be the most valuable stimulus for hypertrophy and strength gains. While BFR has been shown to yield similar results in hypertrophy when compared to conventional resistance training, it is unknown exactly how long these results can be expected as it is possible there are diminishing returns with continuous use over time. In isolation, BFR has an overall smaller effect size than conventional resistance training, though this effect may be different when BFR is combined with conventional training.⁶

If BFR gives you a massive pump, it likely comes as no surprise that it has an effect on hypertrophy. What is surprising, however, is that improvement in strength seems to be the same or even better when BFR is combined with conventional strength training interventions.^8-10 This is most likely due to the recruitment of additional motor units when using BFR despite the lower relative loads. For this reason, BFR may likely be an appropriate addition to a conventional training program where heavier loads are being lifted for part of the training session and BFR with low loads is utilized the other part of the training session.

Blood Flow Restriction For Injury Rehabilitation

BFR is often used in a rehabilitative setting as heavier loads may be unavailable, may be contraindicated following procedures, or cannot be tolerated well due to pain or instability. It has been shown that patients in these settings lose less muscle over time even when BFR is applied passively without exercise being performed²⁸. Following procedures or injury, BFR has been successfully used to minimize muscle loss, improve strength, and improve measurements related to returning to sport or activity⁴. It should be noted that when compared to rehabilitation without BFR, the BFR groups do tend to outperform the non-BFR groups.

As mentioned before, it is important to remember that BFR has been shown to provide greater benefits in strength when combined with conventional resistance training. For this reason, BFR should not be a stand-alone intervention for too long following an injury if you are looking to maximize the benefits of a well-rounded rehabilitative program. If considering the use of BFR in your rehabilitation, please consult with your healthcare provider before adding this intervention to your personal toolbox. 

Blood Flow Restriction For Recovery

A final potential benefit of BFR may be for its use as a recovery modality. Oddly, this idea stems from research on the heart. It has been shown that repeated bouts of starving the heart of oxygen and then reperfusing it with oxygen-rich blood has a positive effect on cardiac tissue health.³⁰ This idea was then taken further to assess the effect of passively occluding blood flow to muscle tissue for 2 bouts of 3 minutes following intense exercise and letting the blood naturally flow through the limb for 3 minutes between sets.²⁹ What’s great about this study is that they measured objective outcomes like jump and sprint performance 5 minutes and 24 hours after this intervention instead of something more subjective like soreness. In this study, it was shown that the passive BFR following intense exercise had some positive effects with the majority of these effects happening 24 hours after the intervention. Though this evidence may not be incredibly strong and caution should be taken in the interpretation of the results.

While there are still more questions than answers and we are far from certainty, we do have some small sample data suggesting that there may be potential benefits to using BFR for recovery of muscle function following intense bouts of exercise which may be of future interest.

When Should BFR Be Used?

The goal of blood flow restriction to achieve venous pooling without blocking arterial blood flow. To do so, research and clinical settings typically use specialized cuffs with digital measurements of the force the cuff is applying (initial pressure) and the resulting blood pressure in order to get it right.  So, how tight should the cuff be to achieve this effect? 

There’s limited evidence on target initial BFR pressures and resulting blood pressure measurements like brachial systolic blood pressure ³⁹ . The issue of how tight to make the cuff is further complicated by experimental findings showing significant differences in venous pooling due to cuff width, cuff material, exercises performed, limbs used, and individuals themselves. For example, to occlude the veins of one individual with a higher blood pressure by 80%, this amount of pressure in the cuff will be different when compared to someone with lower blood pressure to achieve the same degree of venous occlusion. The amount of pressure needed to occlude veins will also depend on the size of the limb and differences in lean mass will affect the needed pressures to obtain the same relative amount of flow restriction. 

That said, things like knee wraps and elastic bands have also been safely and effectively implemented in training and rehabilitation settings. A perceived 7 out of 10 that is “snug, but not painful pressure” has previously been used in practical settings ³¹. It seems that in studies, as well as from practical experience, that higher pressures are better tolerated on the legs than the arms which is likely due to the generally larger size of the limb and vessels there. 

Gear-wise, there are a number of specialized cuffs available if you want to track and fine-tune the specific pressures discussed above. Alternatively, you can use an adjustable elastic band to achieve the target pressure without tracking specific pressures. Our favorites for each of these categories are:

• Specialized Cuffs: SAGA BFR Cuffs
• Elastic Bands: BFR Bands on Amazon

With all of these BFR devices, we’re  targeting a  7 out of 10 pressure high up on the limb being trained. Then, perform 3-4 sets of 15-30 reps with a load that is something around 30% of a 1 RM for the movement you are about to perform while resting somewhere between 30 and 60 seconds between sets. As there is conflicting evidence, it doesn’t seem to make a considerable difference whether the cuff is kept on or released between sets (continuous vs. intermittent BFR) in respect to muscle hypertrophy or strength. However, intermittent BFR is less uncomfortable and typically tolerated better. 

BFR Summary

BFR seems to have a positive effect on hypertrophy and strength in both trained and untrained individuals^32-34. BFR is safe, causes little to no muscle damage, and is easy to recover from. In fact, it may aid recovery. For this reason, you don’t need to change your programming much to work BFR in. However, if your normal training is wearing you down, BFR can be a solid substitution for some of your training volume to continue maximizing strength and hypertrophy gains while backing off of more frequent or higher volumes of heavier, conventional lifting. 

Similarly, BFR can be extremely beneficial in the context of rehabilitation whether performing exercise with them on or passively having limbs occluded for several bouts. This can be beneficial when unable to lift heavier loads due to surgical precautions or due to discomfort with heavier loads. In general, when using BFR in a rehabilitative context, it is highly recommended to work with a healthcare professional when starting out. 

Whether used for additional gains in regular training or in the rehabilitation of a musculoskeletal injury, BFR seems to be a safe and practical tool to improve strength and hypertrophy across diverse populations.

Folks, that’s a wrap! 

References

1. Sato, Y.. (2005). The history and future of KAATSU training. International Journal of Kaatsu Training Research. 1. 1-5. 10.3806/ijktr.1.1.
2. Bjørnsen T, Wernbom M, Paulsen G, Berntsen S, Brankovic R, Stålesen H, Sundnes J, Raastad T. Frequent blood flow restricted training not to failure and to failure induces similar gains in myonuclei and muscle mass. Scand J Med Sci Sports. 2021 Jul;31(7):1420-1439. doi: 10.1111/sms.13952. Epub 2021 May 7. PMID: 33735465.
3. Hughes L, Paton B, Rosenblatt B, Gissane C, Patterson SD. Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Br J Sports Med. 2017 Jul;51(13):1003-1011. doi: 10.1136/bjsports-2016-097071. Epub 2017 Mar 4. PMID: 28259850.
4. Cognetti DJ, Sheean AJ, Owens JG. Blood Flow Restriction Therapy and Its Use for Rehabilitation and Return to Sport: Physiology, Application, and Guidelines for Implementation. Arthrosc Sports Med Rehabil. 2022 Jan 28;4(1):e71-e76. doi: 10.1016/j.asmr.2021.09.025. PMID: 35141538; PMCID: PMC8811521.
5. Suga T, Okita K, Takada S, Omokawa M, Kadoguchi T, Yokota T, Hirabayashi K, Takahashi M, Morita N, Horiuchi M, Kinugawa S, Tsutsui H. Effect of multiple set on intramuscular metabolic stress during low-intensity resistance exercise with blood flow restriction. Eur J Appl Physiol. 2012 Nov;112(11):3915-20. doi: 10.1007/s00421-012-2377-x. Epub 2012 Mar 14. PMID: 22415101; PMCID: PMC3474903.
6. Loenneke, J.P., Wilson, J.M., Marín, P.J. et al. Low intensity blood flow restriction training: a meta-analysis. Eur J Appl Physiol 112, 1849–1859 (2012). https://doi.org/10.1007/s00421-011-2167-x
7. Lowery, Ryan & Joy, Jordan & Loenneke, Jeremy & De Souza, Eduardo & Machado, Marco & Dudeck, Joshua & Wilson, Jacob. (2013). Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clinical physiology and functional imaging. 34. 10.1111/cpf.12099.
8. Luebbers PE, Fry AC, Kriley LM, Butler MS. The effects of a 7-week practical blood flow restriction program on well-trained collegiate athletes. J Strength Cond Res. 2014 Aug;28(8):2270-80. doi: 10.1519/JSC.0000000000000385. PMID: 24476782.
9. Yamanaka T, Farley RS, Caputo JL. Occlusion training increases muscular strength in division IA football players. J Strength Cond Res. 2012 Sep;26(9):2523-9. doi: 10.1519/JSC.0b013e31823f2b0e. PMID: 22105051.
10. Cook, Christian & Kilduff, Liam & Beaven, Christopher. (2013). Three Weeks of Occlusion Training Can Improve Strength and Power in Trained Athletes.. International journal of sports physiology and performance.
11. O’Halloran, John & Campbell, Bill & Martinez, Nicholas & O’Connor, Shane & Fuentes, Jonathan & Theilen, Nicholas & Wilson, Jacob & 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. P18-P18. 10.1186/1550-2783-11-S1-P18.
12. Nakajima, T., Kurano, M., Sakagami, F., Iida, H., Fukumura, K., Fukuda, T., et al. (2010). Effects of low-intensity KAATSU resistance training on skeletal muscle size/strength and endurance capacity in patients with ischemic heart disease. Int. J. KAATSU Train. Res. 6, 1–7. doi: 10.3806/ijktr.6.1
13. Brandner, C. R., Kidgell, D. J., and Warmington, S. A. (2014). Unilateral bicep curl hemodynamics: low-pressure continuous vs high-pressure intermittent blood flow restriction. Scand. J. Med. Sci. Sports 25, 770–777. doi: 10.1111/sms.12297
14. Mouser, G. J., Mattocks, K. T., Dankel, S. J., Buckner, S. L., Jessee, M. B., Bell, Z. W., et al. (2018). Very low load resistance exercise in the upper body with and without blood flow restriction: cardiovascular outcomes. Appl. Physiol. Nutr. Metab. 44, 288–292. doi: 10.1139/apnm-2018-0325
15. Pinto, R. R., Karabulut, M., Poton, R., and Polito, M. D. (2018). Acute resistance exercise with blood flow restriction in elderly hypertensive women: haemodynamic, rating of perceived exertion and blood lactate. Clin. Physiol. Funct. Imaging 38, 17–24. doi: 10.1111/cpf.12376
16. Kambič, T., Novaković, M., Tomažin, K., Strojnik, V., Božič-Mijovski, M., and Jug, B. (2021). Hemodynamic and hemostatic response to blood flow restriction resistance exercise in coronary artery disease. J. Cardiovasc. Nurs. 36, 507–516. doi: 10.1097/JCN.0000000000000699
17. Kambič, T., Novaković, M., Tomažin, K., Strojnik, V., and Jug, B. (2019). Blood flow restriction resistance exercise improves muscle strength and hemodynamics, but not vascular function in coronary artery disease patients: a pilot randomized controlled trial. Front. Physiol. 10:656. doi: 10.3389/fphys.2019.00656
18. Fry, C. S., Glynn, E. L., Drummond, M. J., Timmerman, K. L., Fujita, S., Abe, T., et al. (2010). Blood flow restriction exercise stimulates mTORC1 signaling and muscle protein synthesis in older men. J. Appl. Physiol. 108, 1199–1209. doi: 10.1152/japplphysiol.01266.2009
19. Christopher W Sundberg, Robert H Fitts, Bioenergetic basis of skeletal muscle fatigue, Current Opinion in Physiology, Volume 10, 2019, Pages 118-127, ISSN 2468-8673, https://doi.org/10.1016/j.cophys.2019.05.004.
20. Loenneke JP, Thiebaud RS, Abe T. Does blood flow restriction result in skeletal muscle damage? A critical review of available evidence. Scand J Med Sci Sports. 2014 Dec;24(6):e415-422. doi: 10.1111/sms.12210. Epub 2014 Mar 20. PMID: 24650102.
21. Takarada Y, Nakamura Y, Aruga S, Onda T, Miyazaki S, Ishii N. Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. J Appl Physiol (1985). 2000 Jan;88(1):61-5. doi: 10.1152/jappl.2000.88.1.61. PMID: 10642363.
22. Farup J, de Paoli F, Bjerg K, et al. Blood flow restricted and traditional resistance training performed to fatigue produce equal muscle hypertrophy. Scand J Med Sci Sports 25: 754–763, 2015.
23. Kim D, Loenneke JP, Ye X, et al. Low-load resistance training with low relative pressure produces muscular changes similar to high-load resistance training. Muscle Nerve 56: E126–E133, 2017.
24. Fujita S, Abe T, Drummond MJ, Cadenas JG, Dreyer HC, Sato Y, Volpi E, Rasmussen BB. Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol (1985). 2007 Sep;103(3):903-10. doi: 10.1152/japplphysiol.00195.2007. Epub 2007 Jun 14. Erratum in: J Appl Physiol. 2008 Apr;104(4):1256. PMID: 17569770.
25. Fry CS, Glynn EL, Drummond MJ, Timmerman KL, Fujita S, Abe T, Dhanani S, Volpi E, Rasmussen BB. Blood flow restriction exercise stimulates mTORC1 signaling and muscle protein synthesis in older men. J Appl Physiol (1985). 2010 May;108(5):1199-209. doi: 10.1152/japplphysiol.01266.2009. Epub 2010 Feb 11. PMID: 20150565; PMCID: PMC2867530.
26. Laurentino GC, Ugrinowitsch C, Roschel H, Aoki MS, Soares AG, Neves M Jr, Aihara AY, Fernandes Ada R, Tricoli V. Strength training with blood flow restriction diminishes myostatin gene expression. Med Sci Sports Exerc. 2012 Mar;44(3):406-12. doi: 10.1249/MSS.0b013e318233b4bc. PMID: 21900845.
27. Rolnick, Nicholas DPT, MS1; Schoenfeld, Brad J. PhD, CSCS, CSPS, FNSCA2. Blood Flow Restriction Training and the Physique Athlete: A Practical Research-Based Guide to Maximizing Muscle Size. Strength and Conditioning Journal 42(5):p 22-36, October 2020. | DOI: 10.1519/SSC.0000000000000553
28. Takarada Y, Takazawa H, Ishii N. Applications of vascular occlusion diminish disuse atrophy of knee extensor muscles. Med Sci Sports Exerc. 2000 Dec;32(12):2035-9. doi: 10.1097/00005768-200012000-00011. PMID: 11128848.
29. Beaven CM, Cook CJ, Kilduff L, Drawer S, Gill N. Intermittent lower-limb occlusion enhances recovery after strenuous exercise. Appl Physiol Nutr Metab. 2012 Dec;37(6):1132-9. doi: 10.1139/h2012-101. Epub 2012 Sep 12. PMID: 22970789.
30. Eisen A, Fisman EZ, Rubenfire M, Freimark D, McKechnie R, Tenenbaum A, Motro M, Adler Y. Ischemic preconditioning: nearly two decades of research. A comprehensive review. Atherosclerosis. 2004 Feb;172(2):201-10. doi: 10.1016/S0021-9150(03)00238-7. PMID: 15019529.
31. Wilson, Jacob M.1; Lowery, Ryan P.1; Joy, Jordan M.1; Loenneke, Jeremy P.2; Naimo, Marshall A.1. Practical Blood Flow Restriction Training Increases Acute Determinants of Hypertrophy Without Increasing Indices of Muscle Damage. Journal of Strength and Conditioning Research 27(11):p 3068-3075, November 2013. | DOI: 10.1519/JSC.0b013e31828a1ffa
32. Loenneke, Jeremy & Pujol, Thomas. (2009). The Use of Occlusion Training to Produce Muscle Hypertrophy. Strength & Conditioning Journal. 31. 77-84. 10.1519/SSC.0b013e3181a5a352.
33. Bagley, James & Rosengarten, Jakob & Galpin, Andrew. (2015). Is Blood Flow Restriction Training Beneficial for Athletes?. Strength and Conditioning. 37. 48-53. 10.1519/SSC.0000000000000132.
34. Scott, Brendan & Loenneke, Jeremy & Slattery, Katie & Dascombe, Ben. (2015). Blood flow restricted exercise for athletes: A review of available evidence. Journal of Science and Medicine in Sport. 19. 10.1016/j.jsams.2015.04.014.
35. Neto, G. R., Novaes, J. S., Salerno, V. P., Gonçalves, M. M., Piazera, B. K. L., Rodrigues-Rodrigues, T., & Cirilo-Sousa, M. S. (2017). Acute Effects of Resistance Exercise With Continuous and Intermittent Blood Flow Restriction on Hemodynamic Measurements and Perceived Exertion. Perceptual and Motor Skills, 124(1), 277-292. https://doi.org/10.1177/0031512516677900
36. Neto, Gabriel & Silva, Julio & Freitas, Lucas & Silva, Hidayane & Caldas, Danillo & Novaes, Jeffersonda & Sousa, Maria. (2019). Effects of strength training with continuous or intermittent blood flow restriction on the hypertrophy, muscular strength and endurance of men. Acta Scientiarum. Health Sciences. 41. 42273. 10.4025/actascihealthsci.v41i1.42273. 
37. Biressi S, Molinaro M, Cossu G. Cellular heterogeneity during vertebrate skeletal muscle development. Dev Biol. 2007 Aug 15;308(2):281-93. doi: 10.1016/j.ydbio.2007.06.006. Epub 2007 Jun 13. PMID: 17612520.
38. Damas F, Libardi CA, Ugrinowitsch C. The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis. Eur J Appl Physiol. 2018 Mar;118(3):485-500. doi: 10.1007/s00421-017-3792-9. Epub 2017 Dec 27. PMID: 29282529.
39. Loenneke JP, Fahs CA, Rossow LM, Thiebaud RS, Mattocks KT, Abe T, Bemben MG. Blood flow restriction pressure recommendations: a tale of two cuffs. Front Physiol. 2013 Sep 10;4:249. doi: 10.3389/fphys.2013.00249. PMID: 24058346; PMCID: PMC3767914.

There’s limited evidence on target initial BFR pressures and resulting blood pressure measurements like brachial systolic blood pressure. ³⁹