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What is Blood Flow Restriction (BFR) Training?

The world’s leading elite athletes and their coaches use Blood Flow Restriction (BFR) Training. It’s a key part of their daily training and recovery protocols. It delivers the competitive edge they seek to improve performance and aid recovery.

Man wearing Hytro BFR Tee

What is BFR Training?

Blood Flow Restriction Training is applying a strap at the top of the arms or legs, either while exercising at low intensity or when recovering from exercise, trapping blood in the muscles and causing them to swell and fatigue. This forces the body to adapt, resulting in more muscle growth, faster recovery, and better improvements in endurance than with any other training or recovery technique. Thousands of research papers from leading universities and scientific institutes prove it.1


The key to safe and effective BFR Training is achieving partial occlusion of blood flow out of the muscles without occluding blood flow into the muscle. “Occlusion” is just another word for restriction. BFR Training and Occlusion Training are exactly the same thing. It’s just like when water flows into a sink faster than it flows out. Water pools in the sink just as blood pools in the muscle.


The magic of BFR

The magic of BFR is in allowing athletes to work at lower intensities than usual. When training conventionally, lifting weights of at least 70% of one-rep max is widely considered necessary for optimal muscle growth. BFR Training allows athletes to lift at 20-30% of their one-rep max and attain similar results despite lifting light weights.2,3 By artificially increasing exercise intensity, BFR increases muscle hypertrophy beyond anything achievable with conventional weightlifting alone.


That’s not all, it goes further:

– BFR Training allows athletes to continue progressing on rest days due to reduced muscle damage and accelerated recovery.

– People recovering from injury, illness or surgery who are unable to train conventionally can use BFR as a clinical rehabilitation tool to speed up recovery, enabling muscle growth at an intensity that can be tolerated.

– BFR accelerates recovery.4-6 Athletes use BFR protocols after competing and on off days.

– Many people suffer from joint pain. BFR reduces joint and nerve pain before exercise supporting better quality movement.

– BFR is an effective and simple way to warm up structural tissues before exercise or sporting events (like a marathon or a rugby match).


Blackburn Rovers player's recover using Hytro BFR

How it works

So how specifically does it work physiologically?


First, blood pooling depletes oxygen in the muscle triggering the production of muscle-building hormones.

When the BFR strap is applied, the flow of blood out of the muscle through veins is partially restricted. The flow of blood into the muscle through arteries is not.  As a result, blood pools in the muscle. Blood pooling reduces oxygen in the muscle. The low oxygen environment causes a build-up of lactic acid and metabolic stress in the muscle. The body responds to this stress by releasing growth hormones from the brain and increasing muscle protein synthesis (MPS). MPS is the body’s principal process through which muscle is repaired and built, meaning recovery and muscle growth.


Second, oxygen depletion forces more muscle fibres to work.

Muscles are comprised of both slow-twitch and fast-twitch muscle fibres. Slow-twitch fibres require oxygen as an energy source. They are the endurance muscles that tire slowly and enable us to walk or run for long periods. Fast-twitch muscle fibres do not require oxygen for energy. They produce far more power than slow-twitch fibres and enable explosive movements, like jumping or lifting heavy weights. They tire quickly.


Oxygen depletion in the muscle causes the slow-twitch fibres to tire more quickly than normal. This in turn forces the muscle to recruit fast-twitch fibres sooner than normal. This means more muscle fibres are engaged with lighter loads improving the quality of exercise performed. The muscle is forced to work harder and the body responds by increasing MPS and, therefore, muscle growth.


Here’s another way to think about it. Without BFR, an athlete will lift heavy weights to work fast-twitch fibres and jump on a treadmill to engage slow-twitch fibres. With BFR the whole muscle is engaged quickly without the heavy weights.


Third, more energy is created and used in the muscle.

Oxygen depletion in the muscle temporarily reduces the amount of oxygen available to the muscle for energy production. 7 This process involves an extension of the capillary networks (blood vessels) that deliver oxygen and glucose to the muscle for energy production. So, the muscle develops a larger surface area of vessels through which to receive the ingredients for energy production.


The second adaptive response is mitochondrial biogenesis, a process that increases the number of mitochondria in the muscle. Mitochondria are the powerhouses of muscle cells.  They are where oxygen and glucose combine to create energy. So BFR Training increases both the size of the capillary network in the muscle and the number of mitochondria in the muscle cells, together making the muscle more efficient at creating and using energy.


Fourth, unstrapping flushes the joints while driving fresh blood and nutrients into the muscles.

When the BFR straps are released, the difference in pressure between the occluded limb and the non-occluded torso drives a powerful flush of blood across the joints . This helps to remove waste materials and inflammation from the occluded muscles and joints, while pushing fresh blood and nutrients into the muscle cells and structural tissues like tendons and ligaments.4 This process is called reperfusion, meaning the restoration of blood flow after having been blocked. It plays an incredibly important part in the effectiveness of BFR.


Fifth, the effects are systemic, impacting the whole body and not just the occluded muscles.

People often ask whether BFR Training only works for the muscles that are occluded by the strap or whether other muscles benefit as well. In other words, are the benefits of upper body BFR Training limited to biceps and triceps and lower body to quadriceps and hamstrings or do pecs and lats also reap the benefits? The answer is that BFR Training works systemically, meaning system-wide. The whole body benefits. Metabolites and hormones are produced mainly in the occluded muscles. The moment BFR straps are released, blood is flushed freely throughout the body flooding every muscle and structure with muscle-building hormones. The research proves that BFR also has a significant impact on the size and strength of muscles in the torso (pecs and lats) in addition to muscles in the occluded limbs. 8 Also, occluded muscles tire quickly, forcing the body to more heavily recruit the other muscles engaged by the particular movement pattern, enhancing the efficiency of training.


Josh Charnley wearing Hytro Tee and Shorts whilst cycling

What are the benefits of BFR Training?

BFR is an increasingly popular training and recovery protocol among elite athletes. Most professional sports teams use BFR because they know it can deliver the benefits they seek. Each professional sport is different and each prioritises the benefits of BFR differently. In the aggregate, the benefits deliver a competitive advantage, which all athletes strive for, regardless of their sport.


Stronger muscles

Muscle strength is needed to excel in just about every sport. Scientific research convincingly demonstrates that BFR Training can increase muscle strength in professional athletes by around 10% and power output by 20%.9,10 Athletes cannot afford not to do BFR. Of course, athletes live much closer to the boundaries of human potential than the general public, so it follows that untrained and less trained individuals achieve far greater increases in strength and power than well-trained athletes.


Better endurance

For the reasons described above, BFR Training triggers angiogenesis, causing the muscles to create and use more energy. More energy means better endurance. In fact, research suggests that BFR Training can significantly enhance endurance performance,11 improving time to exhaustion and VO2max by a staggering 49%12 and 11.6%13 respectively. All sports require muscular endurance, though some more than others. BFR Training protocols are increasingly becoming a standard feature of the training regime of sports ranging from football and rugby to those more typically thought of as endurance sports, such as cycling and distance running. Cyclists can spend 10 minutes strapped into BFR on a stationary bike and reap the benefits of a long outdoor training session. Long-distance runners can do the same in 10 minutes on a treadmill.  Time constraints and inclement weather are no longer a barrier to effective training.


Man and woman wearing Hytro BFR Tees whilst weight training


Accelerated recovery

BFR Training stresses the muscles to maximise the natural production of recovery hormones. Unstrapping releases pooled blood and causes the hormones to flood the body. It also flushes waste material and significantly reduces inflammation while driving fresh blood and nutrients into the muscles and structural tissues to help them recover quicker.4


Faster and better recovery means athletes can return to the pitch or intense exercise much sooner than without BFR Training, delivering a natural edge over competitors who do not use BFR. Playing matches daily or doing multi-day cycling races become easier. The research shows that BFR Training significantly accelerates recovery from exercise while reducing post-exercise muscle soreness.4-6


Accelerating recovery is a particularly powerful benefit of BFR Training when recovering from injury or surgery.14 Countless athletes use BFR to return to their normal training protocols weeks sooner than doctors and coaches predict. Equally important, BFR Training is performed with loads that are 30% or less than normal, working muscles as hard as they can be worked conventionally with heavy loads. That means that the loss of muscle size and strength post-injury and post-surgery is minimised, or even eliminated, because muscles can be worked hard putting far less strain through the healing body part. A torn tendon, broken bone or injured joint no longer means muscle loss and long rehabilitation periods to return to pre-injury baseline.


In this article, we’ve told you what BFR is, how it works and the many benefits it provides. Stronger muscles, increased endurance and faster recovery add up to improved performance, whatever the sport.  This explains why increasing numbers of professional athletes from all sports use BFR Training to maximise their personal athletic potential and outperform the competition.

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1. https://pubmed.ncbi.nlm.nih.gov/?term=bloof+flow+restriction

2. Grønfeldt, B. M., Lindberg Nielsen, J., Mieritz, R. M., Lund, H., & Aagaard, P. (2020). Effect of blood-flow restricted vs heavy-load strength training on muscle strength: Systematic review and meta-analysis. Scandinavian journal of medicine & science in sports30(5), 837–848.

3. May, Anthony & Russell, Aaron & Della Gatta, Paul & Warmington, Stuart. (2022). Muscle Adaptations to Heavy-Load and Blood Flow Restriction Resistance Training Methods. Frontiers in Physiology. 13. 10.3389.

4. Beaven, C. M., Cook, C. J., Kilduff, L., Drawer, S., & Gill, N. (2012). Intermittent lower-limb occlusion enhances recovery after strenuous exercise. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme37(6), 1132–1139.

5. Fekri-Kurabbaslou, V., Shams, S. & Amani-Shalamzari, S. (2022). Effect of different recovery modes during resistance training with blood flow restriction on hormonal levels and performance in young men: a randomized controlled trial. BMC Sports Sci Med Rehabil14, 47.

6. Arriel, R. A., Rodrigues, J. F., Souza, H., Meireles, A., Leitão, L., Crisafulli, A., & Marocolo, M. (2020). Ischemia-Reperfusion Intervention: From Enhancements in Exercise Performance to Accelerated Performance Recovery-A Systematic Review and Meta-Analysis. International journal of environmental research and public health17(21), 8161.

7. Torma, F., Gombos, Z., Fridvalszki, M., Langmar, G., Tarcza, Z., Merkely, B., Naito, H., Ichinoseki-Sekine, N., Takeda, M., Murlasits, Z., Osvath, P., & Radak, Z. (2021). Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7. Journal of sport and health science10(4), 470–477.

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 imaging30(5), 338–343.

9. Yamanaka, T., Farley, R. S., & Caputo, J. L. (2012). Occlusion training increases muscular strength in division IA football players. Journal of strength and conditioning research26(9), 2523–2529.

10. Wilk, M., Krzysztofik, M., Filip, A., Zajac, A., Bogdanis, G. C., & Lockie, R. G. (2020). Short-Term Blood Flow Restriction Increases Power Output and Bar Velocity During the Bench Press. Journal of strength and conditioning research, epub before print.

11. Bennett, H., & Slattery, F. (2019). Effects of Blood Flow Restriction Training on Aerobic Capacity and Performance: A Systematic Review. Journal of strength and conditioning research33(2), 572–583.

12. Corvino, RB, Oliveira, MFM, Santos, RP, Denadai, BS, and Caputo, F. (2014). Four weeks of blood flow restricted training increases time to exhaustion at severe intensity cycling exercise. Brazilian Journal of Cineanthropometry & Human Performance 16: 570–578.

13. Park, S., Kim, J. K., Choi, H. M., Kim, H. G., Beekley, M. D., & Nho, H. (2010). Increase in maximal oxygen uptake following 2-week walk training with blood flow occlusion in athletes. European journal of applied physiology109(4), 591–600.

14. Hughes, L., Paton, B., Rosenblatt, B., Gissane, C., & Patterson, S. D. (2017). Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. British journal of sports medicine51(13), 1003–1011.




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