What Is Blood Flow Restriction Training?
Blood flow restriction (BFR) training has been around for some time now but it is gaining more and more attention and popularity, especially in rehabilitation settings. BFR is an exercise technique that uses some sort of a cuff wrapped around a specific site/limb that occludes venous blow flow OUT of an area and restricts arterial blow flow INTO that same area. This creates a pooling of blood effect and also promotes specific chemical releases. Research has shown these effects have a positive influence on mitigating muscle atrophy from disuse (after injury or surgery for example) and also increasing muscle hypertrophy and strength.
How Does It Work?
There is good evidence from research regarding some of the processes that occur with BFR but we are still trying to fully understand all of these physiological occurrences. One strong theory indicates that with BFR training, the hypoxic (lack of oxygen) environment and accumulation of blood causes the body to react and produces an accumulation of certain chemical response agents at the intended site. These "agents", or metabolites, induce an anabolic response of the muscle (Anabolic means building/growth; catabolic means breakdown) (1). An example of a anabolic hormone is growth hormone. This accumulation is also thought to promote an increased activation of specific myogenic cells that are primarily responsible for hypertrophy (2).
Research continues to support that BFR can produce similar hypertrophic effects utilizing 20 to 40% of your one rep max compared to the typical strength training method of 70+% percent of you 1RM.
This is not to say that you should replace all forms of strength training at high loads, as there is still benefit there, but it may be extremely useful to implement BFR on deload days or into your accessory work for example to allow for effective strength training but also recovery. Of greatest use may be in the rehabilitative settings where an individual’s ability to utilize heavy load may be compromised by injury, surgery, and or pain. This allows for earlier strength training and some research has been shown that hypertrophic gains may be seen in as little as 2 to 4 weeks in this population!
How To Determine Cuff Pressure
This is something that has been hard to standardize because everyone is different, the size of your limb matters, the cuff material makes a difference, the size of the cuff makes a difference, etc. There have been some studies and people that use a doppler ultrasound to find the limb occlusion pressure; however, these are not always accessible. An article by Patterson et al. (3) suggests "inflating the cuff being used during exercise up to the point where blood flow ceases (100% arterial occlusion pressure) and using a percentage of that pressure (e.g., 40–80% of AOP) during exercise". This requires palpating the pulse of the limb to determine when the artery is fully occluded.
You want to monitor for numbness/tingling that would indicate that cuff is likely too tight; or indicate the cuff is a non optimal size. The size of the cuff you should use is again highly dependent on the person. One note to make is this, a wider cuff make promote lower overall pressure needed for arterial occlusions; however, too large of a cuff can limit and affect limb movement during the exercise.
Exercising With BFR
In regards to load (or weight), it is recommended that about 20-40% of that person's 1RM be utilized for optimal hypertrophy via BFR. With that said, because the load is low, the reps scheme tends to be high. A commonly utilized principle across the literature is an accumulation of 75 reps amongst 4 sets of the exercises. This is often dispersed as 30 reps in the first set and then 3 sets of 15 reps after that. There is also the option to perform 3-5 sets of reps to failure but that depends on the population you are working with and may not be appropriate for a post surgical patient. Rest periods are short and typically 30-60s.
For optimal results, BFR should be used as a cycle of 2-3 times per week for 4-6 weeks. There have been some studies that have shown hypertrophic changes in as little as 3 weeks but overall, studies agree on a >3 week cycle when it comes to BFR.
The chart below from Patterson et al. (3) gives a good guideline of BFR prescriptions.
Contraindications To BFR
It is important to remember that BFR is NOT appropriate for everyone. Below are some factors that make BFR contraindicated for that particular person.
1) History of deep-vein thrombosis
2) Pregnancy
3) Varicose veins
4) High Blood pressure
5) Cardiac Disease
6) Rhabdomyolysis
BFR has been used in training environments for years but it is the new, exciting method of treatment in rehabilitative settings and research shows a lot of hope for it! Take a look at how you can implement BFR into your training or your practice as a physical therapist.
Resources:
Scott et al., 2014. Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development. Sports Med. DOI 10.1007/s40279-014-0288-1
Nielsen JL, Aagaard P, Bech RD, et al. Proliferation of myogenic stem cells in human skeletal muscle in response to low-load resistance training with blood flow restriction. J Physiol. 2012;590(Pt 17):4351–61.
Patterson Stephen D., Hughes Luke, et al. Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety. Frontiers in Physiology. 2019;533(vol 10):1664-042X. https://www.frontiersin.org/article/10.3389/fphys.2019.00533
Written by: Marissa Oxenford, PT, DPT, CMFA-cert, CF-L1 Trainer, CPT
info@redemptionphysicaltherapy.com
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