What is BFR?

What is Blood Flow Restriction Training?

To improve muscular strength and size it has been assumed heavy loads must to be lifted. Unfortunately, in certain populations, like older individuals, post-operative patients, or those rehabilitating an injury, high-load exercises can cause injury and not be tolerated.

Blood Flow Restriction (BFR) training is a technique in which combines low-intensity exercise with blood flow occlusion.  Occlusion in most this instance is reducing the amount of blood flow into a extremity by using a specially made medical tourniquet.  BFR allows individuals to use low loads yet achieve results similar to high intensity training. 

Blood Flow Restriction (BFR) Training

BFR training was initially developed in the 1960’s in Japan and known as KAATSU training.1 .

 BFR involves the application of a pneumatic cuff (tourniquet) to the upper arms or the upper legs. BFR can be applied to either one or two of the upper or lower extremities at a time but never all four limbs at one time. The cuff is then inflated to a specific pressure with the aim of obtaining partial arterial and complete venous occlusion. The client is then asked to perform resistance exercises at a low intensity of 20-30% of 1 repetition max (1RM), with high repetitions per set (15-30) and short rest intervals between sets (30 seconds). (2) There are non-exercising protocols for bone healing, recovery and high intensity exercise preparation.  For example, for bicep curls one can use very light dumbbells (like 2.5 or 5lb weights) with the cuffs and still gain strength and size. 

BFR Mechanisms

There are many  mechanisms for improving strength and size of a muscle with BFR.  Many of these mechanisms overlap the mechanisms from high intensity lifting.  By decreasing the amount of blood flow into the muscle (from cuff restriction), the limb becomes hypoxic (lack of oxygen).    In addition, the cuffs prevent blood from leaving the limb so swelling of the limb occurs.  The following mechanisms have been described as contributing to adaptations from BFR training: 

  • Metabolic Stress
  • Activation of Myogenic Stem Cells 
  • Release of hormones like Growth Hormone and Insulin Growth Factor
  • Hypoxia
  • Cellular Swelling

Although the exact mechanisms are not currently known, there appears to be a mixture of many mechanisms that contribute to early muscle size and strength gains when oxygen is reduced in the working limb. 


BFR requires a tourniquet to be placed on a limb. The cuff needs to be tightened to a specific pressure that occludes venous flow while still allowing partial arterial flow. 

Simple pieces of equipment such as surgical tubing or elastic straps have been used in gym settings to achieve this result. (3)  These are not advisable as you are unable to monitor the amount of blood flow occlusion. A thin diameter may also cause too much local pressure and result in tissue damage or nerve damage 


A wide cuff width of at least 5cm is recommended. Modern cuffs are shaped to fit the natural contour of the arm or thigh with a proximal to distal narrowing.  The length of the cuffs should be long enough to fully surround the limb but not so long that there is a lot of excess material


There are different methods to determine proper BFR cuff pressures.

A Doppler ultrasound can be used to determine the blood flow to the limb. The cuff is inflated to a specific pressure where the arterial blood flow is completely occluded. This is known as limb occlusion pressure (LOP) or arterial occlusion pressure (AOP). The cuff pressure is then calculated as a percentage of the LOP, normally between 40%-80%. 

Using this method is preferable as it ensures patients are  exercising at the correct pressure for them and the type of cuff being used. It is safer and makes sure that they are exercising at optimal pressures, not too high to cause tissue damage and also not too low to be ineffective. (4)

The pressure of the cuff depends upon the width of the cuff as well as the size of the limb on which the cuff is applied. 

The key to BFR is that the pressure needs to be high enough to occlude venous return and allow blood pooling but needs to be low enough to maintain the arterial inflow. Perceived wrap tightness, on a scale of 0-10 has also been used to conduct BFR training. Wilson et al (2013) found that a perceived wrap tightness of 7 out of 10 resulted in total venous occlusion but still allowed arterial inflow. (5,6)



Upper Limb:  The tourniquet is placed high on the upper arm. The cuff is inflated to restrict 40-50% of the arterial blood flow and 100% of the venous flow. Lower limb: The tourniquet is placed on the upper thigh. The cuff is inflated to restrict 60-80% of the arterial blood flow and 100% of the venous flow. With the cuff inflated to the correct pressure, normal exercises are performed at about 20-30% of 1RM. 


Exercise prescription for BFR varies, this is dependent on whether it is being applied during resistance training, aerobic training or passively without exercise. 



For optimal results, resistance training should ideally be done 2-4 times per week. BFR for hypertrophy is typically a single joint exercise modality for strength training.(7) Muscle hypertrophy can be observed within a 3 week period but most studies advocate for longer training durations of more than 3 weeks. A load of 20-40% 1RM has been shown to produce consistent muscle adaptations.  The most commonly used training volume in the literature is 75 repetitions across 4 sets (30, 15, 15, 15). Rest periods between sets are normally about 30-60 seconds. It is important to keep the cuff inflated during the rest periods to capture the metabolites. 

Intermittent pressure can also be performed.  Intermittent BFR is when the cuffs are inflated during the rest between exercise sets. 

The amount of pressure needed to occlude blood flow in the limb depends on the limb size, underlying soft tissue, cuff width and device used. The arterial occlusion pressure applied is dependent on whether it is an upper or lower limb and should be between 40%-80%.(7)


BFR can be applied during aerobic exercise and in research has normally been applied during walking or cycling.

The maximum time BFR cuffs should be worn is 20 minutes.  The minimum pressure on the lower extremities for aerobic training is 130mmHg. 


Passively applied BFR (i.e BFR is applied and no exercise is performed) is used as a recovery tool from exercise.  Passive BFR can also be used to prepare one for exercise and may help reduce muscle damage from the high intensity exercise.  This protocol is called Ischemic Preconditioning or IPC. 


Reported side effects while performing BFR exercises are fainting and dizziness, numbness, pain and discomfort, delayed onset muscle soreness. 


All individuals should be assessed for the risks and contraindications to tourniquet use before BFR application. Clients possibly at risk of adverse reactions are those with poor circulatory systems, obesity, diabetes, arterial calcification, sickle cell trait, severe hypertension, or renal compromise.(8) Potential contraindications to consider are venous thromboembolism, peripheral vascular compromise, sickle cell anaemia, extremity infection, lymphadenectomy, cancer or tumor, extremity with dialysis access, acidosis, open fracture, increased intracranial pressure vascular grafts, or medications known to increase clotting risk.(9) 


Safety implications around BFR are conflicting. Safety concerns are mainly around the formation of venous thromboembolism (deep vein thrombosis and pulmonary embolism) and muscle damage.(4) 


BFR training is the ultimate ‘biohack’.  BFR allows users to lift light weights and still achieve muscular gains and aerobic capacity changes similar to high intensity training.  BFR can be a complete game changer for those who can not tolerate heavy loads in order to maintain strength and muscle size over a lifetime. 



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  2. Loenneke JP, Fahs CA, Rossow LM, Sherk VD, Thiebaud RS, Abe T, Bemben DA, Bemben MG. Effects of cuff width on arterial occlusion: implications for blood flow Bonnieu A, Carnac G, Vernus B. Myostatin in the pathophysiology of skeletal muscle. Current genomics. 2007 Nov 1;8(7):415-22.
  3. Wilson JM, Lowery RP, Joy JM, Loenneke JP, Naimo MA. Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage. The Journal of Strength & Conditioning Research. 2013 Nov 1;27(11):3068-75.
  4. Spranger MD, Krishnan AC, Levy PD, O’Leary DS, Smith SA. Blood flow restriction training and the exercise pressor reflex: a call for concern. American Journal of Physiology-Heart and Circulatory Physiology. 2015 Sep 4;309(9):H1440-52.
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  6. McEwen JA, Owens JG, Jeyasurya J. Why is it Crucial to Use Personalized Occlusion Pressures in Blood Flow Restriction (BFR) Rehabilitation?. Journal of Medical and Biological Engineering. 2019 Apr 2;39(2):173-7.
  7. Lowery RP, Joy JM, Loenneke JP, de Souza EO, Machado M, Dudeck JE, Wilson JM. Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clinical physiology and functional imaging. 2014 Jul;34(4):317-21.
  8. Performance Physical Therapy & Wellness – Blood Flow Restriction Therapy (BFR). Available from: https://youtu.be/2fMUpxqJq48
  9. Kate Warren. Blood Flow Restriction Training and Physical Therapy | Breaking Athletic Barriers | EVOLVE PT. Available from: https://youtu.be/pDiLSj6ixTo
  10. Patterson SD, Hughes L, Warmington S, Burr J, Scott BR, Owens J, Abe T, Nielsen JL, Libardi CA, Laurentino G, Neto GR. Corrigendum: Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in physiology. 2019;10.
  11. Patterson SD, Hughes L, Warmington S, Burr J, Scott BR, Owens J, Abe T, Nielsen JL, Libardi CA, Laurentino G, Neto GR. Corrigendum: Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in physiology. 2019;10.
  12. Patterson SD, Hughes L, Warmington S, Burr J, Scott BR, Owens J, Abe T, Nielsen JL, Libardi CA, Laurentino G, Neto GR. Corrigendum: Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in physiology. 2019;10.
  13. Patterson SD, Hughes L, Warmington S, Burr J, Scott BR, Owens J, Abe T, Nielsen JL, Libardi CA, Laurentino G, Neto GR. Corrigendum: Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in physiology. 2019;10.
  14. Brandner, Christopher & May, Anthony & Clarkson, Matthew & Warmington, Stuart. (2018). Reported Side-effects and Safety Considerations for the Use of Blood Flow Restriction During Exercise in Practice and Research. Techniques in Orthopaedics. 33. 1. 10.1097/BTO.0000000000000259.
  15. DePhillipo NN, Kennedy MI, Aman ZS, Bernhardson AS, O’Brien L, LaPrade RF. Blood Flow Restriction Therapy After Knee Surgery: Indications, Safety Considerations, and Postoperative Protocol. Arthroscopy techniques. 2018 Oct 1;7(10):e1037-43.
  16. da Cunha Nascimento D, Petriz B, da Cunha Oliveira S, Vieira DC, Funghetto SS, Silva AO, Prestes J. Effects of blood flow restriction exercise on hemostasis: a systematic review of randomized and non-randomized trials. International Journal of General Medicine. 2019;12:91.
  17. Resistance training and coagulation system – Video Abstract ID 194883 Dove Medical Press Available at https://www.youtube.com/watch?v=OZjn6vAXJSE