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Blood Flow Restriction (BFR) training is a technique in which combines low-intensity exercise under reduced arterial flow conditions. BFR is quantifiably and objectively reducing the amount of blood flow into an extremity by using a specially made medical tourniquet. BFR allows individuals to use low loads yet achieve results similar to high intensity 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.

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

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 restriction 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.

Couple Running

Contraindications for BFR

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.


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