What is Blood Flow Restriction (BFR)?
Blood Flow Restriction training (BFR) was first introduced in 1966, originally popularized as “Kaatsu training” before taking the general name of BFR. It was primarily used among powerlifters and bodybuilders to increase strength and muscle hypertrophy. However, in recent years, research supports the use of blood flow restriction rehabilitation by physical therapists.
BFR is a tool that restricts venous blood flow return, which aids in lowering the mechanical stress needed for muscle hypertrophy and strength gains. Research has shown that BFR training loads at or below 50% of 1-RM, even to as low as 20-30%, improving muscle strength and hypertrophy gains.
BFR training focuses on the metabolic aspect of strength training and allows for strength gains at much lower intensities. This allows for early optimal loading intervention for healing tissue that is not capable of sustaining the higher loads necessary for a full recovery. To put this in perspective, a straight leg raise exercise with BFR, while allowing tissues to heal, is comparable to a traditional bodyweight squat.
How does BFR work?
There are two primary triggers to create physiological changes in muscle strength and hypertrophy. First, mechanical stress, and second, metabolic stress. After acute or repeated bouts of appropriate mechanical stress to the muscles that exceed tissue capacity, IGF-1 and mTOR hormones are released, which are the driving force of muscle growth and hypertrophy. When triggered, it sends a cascade effect that activates satellite cells in the sarcolemma to proliferate and bind to the muscle cells to create new muscle fibers.
To make strength and muscle hypertrophy gains through mechanical stress, one must work at or above 65% of their 1- Rep Max (RM), with adaptation time ranging between 8-12 weeks. In the rehabilitation population, patients often do not tolerate this 65% of 1 RM load. Post-surgical patients may not even be allowed to perform resistant training exercises for several weeks due to surgical precautions.
BFR training with the use of pneumatic tourniquets allows for arterial blood ow to a region while restricting venous blood ow return. This restriction creates a more robust anabolic environment for muscle growth and strength during rest periods, without joint stress or damage to non-contractile tissue.
Benefits of Blood Flow Restriction Training
It has been demonstrated that BFR training increases the endocrine response and release of hormones such as GH and IGF-1, needed for protein synthesis, by 200-300%. This heightens the cell signaling for hypertrophy and strength gains. GH also supports the building of non-contractile tissues which is needed after surgery or a severe injury.
Some other key benefits of BFR training include:
- a decrease in pain perception up to 24 hours after use
- aid in tissue repair, activation of new blood vessel growth
- increased recruitment of anaerobic muscle fibers
- increase in angiogenesis.
BFR is a safe alternative to traditional resistance training by allowing up to 50% less in exercise intensity in order to gain similar physiological results. This plays a significant role in achieving the necessary functional gains in the aging or injured population.
Indications of BFR Training
The patient populations appropriate for the use of BFR training include:
Prehab/Rehab – Injuries including sprains/ strains, Osteoarthritis, post-op patients such as TKA, ACL’s, RTC Repair, non-weight bearing patients. It is ideal for the patient needing early strength gains to improve function while minimizing the mechanical stress to the muscle and joint.
Athletes and Strength Training – May be used during rest days to reduce the mechanical load on muscles but continue to make strength gains.
General Population -Walking endurance and strength training for the aging population, depending on health status and clinical presentation.
Contradictions of BFR use
There are specific precautions to BFR training that must be adhered to. It is vital that a clinical prediction rule that combines medical signs, symptoms, and clinical findings that predict the success or failure of this procedure is to know by the clinician.
BFR venous return restriction has substantial benefits within the physical therapy practice. It allows for early optimal loading interventions for healing tissue that cannot sustain the necessary higher loads that are needed for safe and quick recovery while minimizing injury to healing tissue.