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The goal of BFR training is to maintain the inflow of blood while occluding venous return during exercise: You want to get that nutrient, hormone, and oxygen-rich blood to the muscle while delaying its escape.
This is accomplished by the application of a blood pressure cuff, knee wrap, or anything that can be tightly secured around the most proximal (closest to the midline of the body) part of a limb. If we use the arm muscles as an example, the wrap would be tightly secured around the upper arm, as close to the shoulder as possible, causing the blood to pool in the arms.
Disclaimer: BFT (Blood Flow Training) seems to be safe, however, talk a qualified1 health care practitioner should be consulted prior to implementing BFT to your work out regime.
How is it possible to restrict venous return without restricting arterial flow?
The blood in the arteries has a much higher velocity and propulsion force than the veins, so in order to occlude arterial blood flow, much higher pressure is needed. It is easier and requires less pressure to restrict blood flow in the veins because, at that point, the flow of blood is not as forceful. Think movies when someone gets an injury and the blood is squirting and pulsing out. The movie depicts an arterial injury because of the high velocity of the blood.
How Does It Work?
The exact mechanism by which BFT works is unclear, however, the most likely and agreed upon theory has to do with greater metabolic stress.
The muscles release growth factors and metabolic by-products, such as lactic acid, into the bloodstream as a result of resistance training. These growth factors and metabolic by-products are washed away with normal blood flow. By restricting venous return and allowing the blood pool, these growth factors and metabolic by-products remain in the muscle for a long period of time and therefore have more time to interact with corresponding receptors in muscle tissue.
The accumulation of metabolic by-products, such as lactic, increases intramuscular acidity and may promote hypertrophy as well as the release of growth hormone (although acute increases in growth hormone have not been shown to significantly impact hypertrophy, it is still worth noting).
The increase in acidity and the buildup of lactic acid are responsible for “the burn” that we all know and love.
Our bodies fight tooth and nail to increase oxygen flow to the area in order to decrease the acidity and restore homeostasis. It does this by increasing respiration (increased breathing rate) and increasing arterial/oxygen-rich blood flow but it can only fight for so long.
When the body is no longer able to manipulate breathing and blood flow enough to balance the acidity of our tissues, we enter what is called an anaerobic (“no oxygen”) state. As you keep working through the burn, the acidity continues to increase until you reach muscle failure. Type II muscle fibers are recruited during this anaerobic state, which is important because they have the most potential for growth.
Blood flow restriction increases the amount of deoxygenated blood in the area, which helps facilitate the creation of an anaerobic environment. The result? We reach an anaerobic environment faster and for a longer duration.
How Do We Do It? How Tight? What Set & Rep Ranges? How Often?
As mentioned above, apply the wrap at the most proximal area of your arms and legs. It is difficult to establish an optimal tightness of application due to individual factors such as limb circumference, body fat level, skin thickness, etc. Studies seem to agree on is a simple rating of 7/10 self-rated tightness.
Perform 3-5 sets to failure with 20-50% of 1 rep max with the muscle occluded the entire time. Rest periods should be 30-60 seconds between sets. After the final set, remove the wraps and restore blood flow to the muscle.
As far as how often BFR should be used, it is my personal opinion that BFR should be used like any other intensity technique that aims to increase metabolic stress, such as rest pause, drop sets, etc.
Is BFR Better Than Just Lifting Weights? I Mean, People Have Been Lifting Heavy Things and Getting Bigger and Stronger for Centuries…
Keep in mind that research only points us in the right direction for further study and isn’t meant to be the end-all be-all.
Research shows that BFR training may be more effective for hypertrophy than conventional hypertrophy training with matching loads and just as effective as conventional training with unmatched loads.
This means that BFR causes the same amount of hypertrophy as conventional training while using significantly lighter loads. BFR training has been shown to enhance hypertrophy with weights of about 20-30% of 1 rep max, which is significantly lighter than what is typically required for conventional training.
When comparing BFR training to conventional strength training, research has shown BFR and conventional training to have a similar effect on the strength with unmatched loads. This means that lifting lighter loads with BFR can increase strength just as much as conventional training with heavy loads.
That being said, there are studies that show BFR to be inferior to conventional heavy training to improve strength. Research supports that, when it comes to strength, the specificity of training is key.
If you want to lift heavy things, you have to lift heavy things.
BFR has also shown some promising results in physical therapy and rehabilitation.
Research has shown that subjects experienced increased serum growth hormone, thigh muscle size, and 1 rep max isometric strength just by walking on a treadmill with BFR applied to the legs.
Research also shows that when BFR was applied to the legs following ACL reconstruction surgery, subjects experienced more strength retention and less atrophy when compared to a control. Strength retention and less atrophy were also observed using BFR following a period of ankle immobilization and a non-weight bearing protocol.
It seems BFR may be quite an effective tool with a wide variety of implications. Variables such as power, speed, endurance, etc. Still, require further investigation at this time.
Is It Safe?
Be sure to check with a qualified health care practitioner before adding BFR to your training toolbox.
Contraindications to blood flow restriction training include a history of deep-vein thrombosis, pregnancy, varicose veins, high blood pressure and cardiac disease.
Excessive pressure and prolonged ischemia (decreased blood flow) can lead to necrosis of tissues (cell death). Even though the BFR guidelines outlined in this article do not use excessive pressure and are not being applied for long periods, caution should always be taken.
Stop use immediately and consult a qualified healthcare practitioner if you experience severe pain, dizziness, nausea, or numbness/tingling.
Keep in mind that every time you enter the gym, you are taking a risk. If not respected or properly executed, anything can be harmful. Even with perfect form, injury is a risk.
What’s the Take Home?
- With BFR, the goal is to induce fatigue, blood pooling, and muscle burning quicker and with less weight/work.
- Wrap at the most proximal areas of your arms and legs (under your shoulder and high on your inner thigh) with a 7/10 self-rated tightness.
- Perform 3-5 sets to muscular failure using 20-50% of your 1 rep max with the muscle occluded the entire time.
- Rest periods should be 30-60 seconds between sets.
- After the final set remove the wraps and restore blood flow to the muscle.
- While BFR has been shown to enhance hypertrophy and strength, it seems to have more of a positive impact on hypertrophy than strength. For strength, it may be more beneficial to stick to traditional heavy training.