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Blood Flow Restriction Training – What Is It?

Blood Flow Restriction Training – What Is It?

Blood flow restriction (BFR) training appears as though it might have been thought up by a deranged scientist in a secret Soviet lab. Heck, assuming it was used by astronauts during their stay on the International Space Training wouldn’t be a silly idea – BFR training is actually used by cosmonauts as a way of preventing muscle wastage in low gravity conditions. If you needed any validation of a training protocol, NASA is as good as it gets. 

However, just because it has applicability in space, should you consider its utilisation here on earth… in normal atmospheric conditions… where gravity produces enough resistance to prevent muscle wastage and sarcopenia- when you really think about it, for all its shortcomings, gravity is, without doubt, a lifesaver.  

BFR or occlusion training as it’s commonly known, was originally called KAATSU, invented by the Japanese. Surprisingly not named after the nations favourite wagamama dish, KA means ‘additional’ and AATSU means ‘pressure’. In that translation you begin to understand what BFR really is – additional pressure. 

Created as a way of reducing the amount of weight needed to stimulate hypertrophy, Japanese physiotherapists found that by restricting blood from leaving a working muscle, our biology can be tricked into thinking its working much harder than it really is. 

The foremost authority in exercise science, The American College of Sports Medicine (ACSM), recommends lifting a weight of at least 70% 1RM to achieve muscular hypertrophy as it is believed that anything below this intensity rarely produces substantial muscle growth (1). However, numerous studies using low-intensity exercise combined with BFR have shown muscle hypertrophy to occur with a training intensity as low as 20% 1RM (2) (3) (4).  BFR, therefore, can be great in two conditions, the elderly and the injured; both of which are incapable of training intensely enough to stimulate adaptation.

How occlusion training works

The two physiological mechanisms behind occlusion training are complex but I will try and simplify it best as I possibly can. 

Firstly, occlusion training shortcuts muscular recruitment that would normally be achieved in the latter stages of a routine set. Under traditional conditions, as a set reaches the point of failure, a muscle will utilize the fast-twitch fibres; the fibres that are capable of increasing in size. By tying a band or tourniquet around the top of a limb, fast-twitch motor units are forced to intervene in response to the accumulation of pressure (6). 

You might be wondering how a band can do this. Essentially, blood can flow into the muscle via the deeper arteries but will accumulate in the working muscle because the veins responsible for transporting blood back to the heart are under the surface of the skin, making it easy to be partially blocked (I should point out that BFR will create an almighty pump).  


This is perfectly safe when done as directed. Your arms or legs will not fall off. In case you’re worried, KAATSU has been validated, offering no greater risk than traditional training routines (5). You will, however, experience a severe burning sensation but this is apart of the second theorised reason for effectiveness.

Metabolic accumulation, or as you might know, lactic acid, has been attributed to increasing growth hormone (GH) secretion that can normally only be achieved by training to failure (7) (8).This is significant because GH is necessary for the stimulation of cell growth and repair. During anaerobic exercise (resistance training), energy is created without oxygen, which also creates lactic acid as a byproduct. Lactate formation reduces the pH of the cell to an extent that energy production is incapacitated; this is what’s commonly referred to as ‘the burn’. 

The burning sensation is only achievable when difficulty is high. By occluding the working muscle the intensity needed to create a burn is reduced. In case you’re thinking it, occlusion training will not “boost” GH secretion beyond normal physiological levels.  

Do you need to be injured to use occlusion training? 

So far, this method appears most suitable for those suffering from training difficulties. But there are other questions you might be interested in reading; will KAATSU offer any significant advantage over standard training; is it more effective for arm or leg training? This article will not exhaustively scrutinize the literature, rather it offers a brief insight into what research has been conducted to answer these questions. If you are interested in more detail, check out this review article (8). 

Can occluding increase muscle size more than standard training? 

Researchers sought to investigate this topic in healthy, well-trained individuals. Participants were split into two groups, given a controlled diet – this way we know diet did not intervene with adaptations – and were asked to perform cable arm curls either with or without occlusion. After eight weeks of training, the bicep grew equally in both groups. 


Great, occlusion training seems to work but there is one caveat – both groups performed the same volume of exercise. This is an important feature because Volume is considered one of the most important drivers of muscle hypertrophy (12)

Volume is weight (kg) x reps x sets. Using this equation, benching 30kg for 20×2 equates to 1200kg of volume. This will place the same demand on a muscle as benching twice as much weight for 5×4. In this study the BFR group simply lifted less weight but for twice as many reps; 30 reps at 30% 1RM as opposed to 15 reps at 60%. Considering this, we can draw two conclusions; one, occlusion can support muscle growth with less weight; two, occlusion is not more advantageous than standard exercise when total volume is equated. 

Is occlusion training useful for increasing strength? 

PubMed did not display any results for experiments into healthy, trained individuals, however, research has been conducted in the elderly (10). In a 16 week exercise program, participants were subjected to low-intensity training with occlusion (30-50% 1RM) versus high intensity exercise without occlusion (50-80% 1RM). Post examination revealed that BFR elicits similar increases in muscle size and isometric strength that were achieved in a traditional high intensity exercise protocol. Subjects bicep strength increased by 22% and 18% after 12 weeks of training non-occluded and occluded, respectively. 


Interestingly, volume was reduced in the occluded training group, posing a counter finding to the prior study. However, this more than likely suggests inherent methodological flaws, rather than validating that reduced volume is required in occlusion training protocols. 


Is occlusion training more effective for the upper or lower body?

The two sites of restriction have not been compared in a signal study. A possible limitation in the effectiveness of occluding the upper arm could be that the muscle size is relatively small. Compared to the quadriceps, the potential for metabolic stress and lactate accumulation needed to facilitate the GH response is limited (11). Given the two mechanisms of action, it may be more appropriate where a muscle can produce more lactate responsible for adaptation. 

How to KAATSU? 

You can only restrict blood flow in the arms or legs (if you can figure out how to occlude anything but an extremity, get in touch with the ACSM, Im sure they would love to hear from you). Don’t try and occlude the upper and lower body simultaneously, that would be stupid. 

Let’s break this down into steps:

  1. Purchase bands that can be fitted around the arm or leg. There are many options available on the market. The easiest means of BFR are knee wraps used by powerlifters during heavy squats (a: see link below). The Occlusion Cuff (b: see below) is the most technical BFR tool – for the extra investment, you get a cuff that allows you to adjust the exact tightness needed to maintain pressure in either the arm of leg.


  1. Once you have a means of occluding, the next step is adjusting the tightness needed. The pressure only needs to be high enough to block venous return. A scale of 1-10 is the easiest way to tell whether or not it’s night enough; for the arms, tie the cuff as close to the armpit for a tightness of 5/10; the leg cuff should be tightened to 7/10 around the upper thigh, close to the groin. The leg needs greater pressure because the veins are somewhat deeper beneath the skin. 
  2. Now to choose an exercise. There are no hard or fast rules to which exercise you need to perform but you might want to pick a relatively easy exercise. The advantage of an easy exercise – meaning it requires very little skill – is that it can be executed perfectly for a lot of reps. A squat requires advanced technical proficiency that is likely to diminish as the set prolongs putting you at risk of injury – not a clever idea when they’ll be squirming in pain after 3 sets. For legs; leg extensions, hamstring curls, Bulgarian split squats or a hack squat. For arms; dumbbell curls, preacher curls or any tricep extension will be effective.
  3. As we have seen, volume needs to high, while the intensity is low. Remember, the burn is what we are looking for here. Researchers will typically conduct 3-5 sets at 20-40% 1RM to complete failure (13). If you are struggling to hit 20 reps, you need to decrease the weight. Keep the bands on throughout the duration of the working sets and be prepared for the best kind of pain. 





Reference List 

  1. American College of Sports Medicine (2009). Progression Models in Resistance Training for Healthy Adults. Medicine & Science in Sports & Exercise, 41(3), pp.687-708.
  2.  Abe, T., Beekley, M., Hinata, S., Koizumi, K. and Sato, Y. (2005). Day-to-day change in muscle strength and MRI-measured skeletal muscle size during 7 days KAATSU resistance training: A case study. International Journal of KAATSU Training Research, 1(2), pp.71-76.
  3. Madarame, H., Neya, M., Ochi, E., Nakazato, K., Sato, Y. and Ishii, N. (2008). Cross-Transfer Effects of Resistance Training with Blood Flow Restriction. Medicine & Science in Sports & Exercise, 40(2), pp.258-263.
  4. Yasuda, T., Fujita, S., Ogasawara, R., Sato, Y. and 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,
  5. Loenneke, J., Wilson, J., Wilson, G., Pujol, T. and Bemben, M. (2011). Potential safety issues with blood flow restriction training. Scandinavian Journal of Medicine & Science in Sports, 21(4), pp.510-518.
  6. Meyer, R. (2006). Does blood flow restriction enhance hypertrophic signaling in skeletal muscle?. Journal of Applied Physiology, 100(5), pp.1443-1444.
  7. Kawada, S. and Ishii, N. (2008). Changes in skeletal muscle size, fibre-type composition and capillary supply after chronic venous occlusion in rats. Acta Physiologica, 192(4), pp.541-549.
  8. Loenneke, J. and Pujol, T. (2009). The Use of Occlusion Training to Produce Muscle Hypertrophy. Strength and Conditioning Journal, 31(3), pp.77-84.
  9. Lowery, R., Joy, J., Loenneke, J., de Souza, E., Machado, M., Dudeck, J. and Wilson, J. (2013). Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clinical Physiology and Functional Imaging, 34(4), pp.317-321.
  10. Takarada, Y., Takazawa, H., Sato, Y., Takebayashi, S., Tanaka, Y. and Ishii, N. (2000). Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. Journal of Applied Physiology, 88(6), pp.2097-2106.
  11. Reeves, G., Kraemer, R., Hollander, D., Clavier, J., Thomas, C., Francois, M. and Castracane, V. (2006). Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion. Journal of Applied Physiology, 101(6), pp.1616-1622.
  12. Stone, M., Potteiger, J., Pierce, K., Proulx, C., O’Bryant, H., Johnson, R. and Stone, M. (2000). Comparison of the Effects of Three Different Weight-Training Programs on the One Repetition Maximum Squat. The Journal of Strength and Conditioning Research, 14(3), p.332.
  13. Cook, S., Clark, B. and Ploutz-Snyder, L. (2007). Effects of Exercise Load and Blood-Flow Restriction on Skeletal Muscle Function. Medicine & Science in Sports & Exercise, 39(10), pp.1708-1713.


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