You have probably seen some people performing BFR training in the gym, also known as Blood Flow Restriction Training. Trainees will have cuffs tightened around their arms as they exercise, such as performing curls, to achieve a massive pump – they think this will help build muscle.
BFR has actually been found to be a very effective training tool…in the correct scenarios. Like many trends in the fitness industry, BFR has been adopted by general lifters, often with a bit of a misunderstanding. This article will break it down.
What Is BFR Training?
BFR training (Blood Flow Restriction training) is a method of resistance training that involves restricting venous blood flow from a working muscle while maintaining arterial inflow. This is accomplished by placing cuffs on the limb above the working muscle.
As you train, oxygenated blood is pumped down into the muscle. However, as it can’t return, the blood then pools, providing your muscles with a huge pump.
Due to blood flow restriction, trainees can use lighter loads (20-40%) and still achieve similar results to those with normal loading.
In fact, research shows that when one limb undergoes BFR training, the other limb not using BFR can still yield results - what’s going on?
How Does BFR Training Work?
So, how can lifting 20% of your 1-rep max build muscle and increase strength?
There are a couple of mechanisms by which this probably works. We say probably, as researchers still aren’t 100% sure.
1. Metabolite Accumulation (Lactate, H+, etc.)
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BFR traps blood in the muscle, preventing waste products from escaping into the bloodstream.¹
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This buildup causes:
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Cellular stress → signals for muscle growth (hypertrophy)
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Stimulates afferent nerve fibers, which trigger growth hormone release from the pituitary gland
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This is how non-BFR muscles can also benefit.
2. Increased Muscle Fiber Recruitment
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Normally, you need heavy weights to activate fast-twitch (Type II) muscle fibers.
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With BFR, the muscle tires quickly due to low oxygen, forcing the body to recruit more fibers earlier.
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This results in higher muscle recruitment with less weight.
3. Cell Swelling (Muscle Cell “Pump”)
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Blood pooling causes muscle cells to swell with fluid.
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This “cellular swelling” is a mechanical signal to the body: “We’re under threat, reinforce the structure!”²
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As a result, this activates mTOR signaling and protein synthesis, exactly what you need for potential muscle growth.
Regardless, the main idea is that BFR creates a hypoxic environment that makes it “think” it’s performing high-intensity training.
What Are the Benefits Of BFR Training?
BFR training offers several benefits in weight training.¹⁻³
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Allows for Muscle and Strength Improvements with Light Weights. The primary benefit of BFR is obviously its ability to allow training adaptations with low loads
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Mitigates Mechanical Stress. Another significant benefit of BFR is that it mitigates the stress placed on your joints and tendons.
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Helps Maintain Mass In Immobilized Limbs. Research has shown that BFR can actually help mitigate muscle loss during times of immobilization.
Does BFR Really Build Muscle And Strength?
Here’s where things get taken out of context.
Yes, BFR training can build muscle and improve strength in low-load situations – with an emphasis on “low-load”.
Many people hear “BFR can build muscle!” and conclude that it’s superior to traditional weightlifting. It is not, at least in all scenarios.
Here’s a quick breakdown of when BFR is beneficial and when it’s not.
BFR And Muscle Growth
Muscle growth occurs through the combination of 3 different mechanisms. However, the roles they play are not equal.
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Mechanical Tension (Primary Mechanism) - This refers to the stress placed on the muscle and the resulting stretch. This occurs when the muscle must overcome a force, such as the weight of the object.
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Metabolic Stress (Secondary mechanism) - During heavy contractions, various metabolites are created during energy production, such as lactate. These can send various triggers that release various hormones and compounds that trigger muscle growth.
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Muscle Damage (Least important) - While once thought to be the primary factor in muscle growth, we now know that it’s not even necessary. However, it may still play a smaller role.
Now that we know how muscle growth occurs, we can compare it with the mechanisms of BFR. This is because the BFR only utilizes one of the three mechanisms: metabolic stress.
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Mechanical tension is low, as you only use low loads.
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There is less muscle damage due to less mechanical stress.
Numerous studies have demonstrated that BFR is effective in stimulating muscle growth with low loads (20-40%). However, whether it’s superior depends on the situation.
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When compared to regular resistance training using similar low loads, BFR actually shows superior muscle growth.
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When low-load BFR training is compared to high-load training (traditional resistance training), the results are either similar or the regular resistance training is more effective.
This means that BFR is the superior choice for muscle growth in certain situations when low-load is not applicable.
However, in terms of muscle growth, it doesn’t provide any superior benefits when high-load can be used.
BFR And Building Strength
Remember that building strength and building muscle occur through different physiological adaptations. To build strength, it requires an increase in neuromuscular activity, and the muscle must create a greater amount of force.
However, BFR is only supposed to be used with 20-40% of your 1RM – doing more increases the risk of injury to veins or nerves. The problem is that research has been relatively clear that a 1RM of more than 80% is needed to optimize strength.
Therefore, while BFR can increase greater muscle activation through metabolic stress, it doesn’t use maximal levels to require higher force production. Therefore;³⁻⁴
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There are no significant synchronization improvements as BFR doesn’t generate fast, coordinated firing patterns. It relies on fatigue and metabolic stress.
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BFR does not create mechanical tension to trigger coordinated firing patterns.
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There is minimal intramuscular coordination as it requires near-maximal loads so that multiple fibers must fire in precise timing under tension.
With that in mind, this doesn’t mean there are no improvements in strength.
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Studies have shown that BFR can improve strength to a greater degree at low loads.⁵ However, many of these studies also use isolation exercises, not your traditional strength exercises such as squats and deadlifts.
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When BFR is compared to using loads greater than 80% 1RM, it is less efficient.
So basically, it is effective when used for its intended purpose.
BFR And Rehab Or Special Pops
Now, this is where BFR really shines, as these populations are often unable to lift heavy weights due to injury or frailty.
When you are recovering from some sort of injury, you are limited in how much physical stress you can handle. By using BFR, an individual can utilize 20% of their 1RM and still achieve significant improvements – that’s substantial.
This applies to both strength and hypertrophy. Again, while it may not be as high as high-load training, it’s still substantial.
How To Use BFR Training To Build Your Muscles
So, if you’re a healthy individual, does BFR training have any benefits? Actually, yes. There are several legitimate uses for BFR.
1. Training While Traveling. One of the most practical applications is using BFR training while traveling. We all know that relying on gym hotels is a gamble, and while resistance bands are useful, they have their limitations.
However, you can use BFR with resistance band training, or whatever small dumbbells your hotel might have.
2. Use In Conjunction With Strength Training. While theoretical, using BFR in conjunction with traditional training could provide equal results without the buildup of stress.
For example, instead of training with high intensity 4 days a week, you could theoretically train strength with heavy loads two days a week.
Then, on the other two days, use low-load BFR training for hypertrophy and accessory work. Using the BFR mitigates mechanical tension, leading to less stress on the joints and can possibly result in shortened recovery time.
3. Lifters Who Have Achy Joints…Or Just Want A Break. You don’t need to be on bed rest or elderly to benefit from low-load BFR lifting.
Many lifters, especially those with long-term experience, often experience achy joints due to years of wear and tear on their joints. While there are various methods to work around this, using BFR provides an effective solution.
Other lifters may simply want a break from heavy lifting while still being able to lift.
Can Blood Flow Restriction Build Muscle?
Blood flow restriction can definitely help build muscle. It’s actually been shown to be superior when used in situations that only allow low loads. However, when normal loads are available, BFR doesn’t offer any additional benefits. If you’re a healthy individual, doing BFR just because it doesn't make a ton of sense. However, if you’re doing it to give your joints a break or want to experiment with its effect on your recovery, it definitely has some potential to possibly help your overall training, if used intelligently.
Reference
- Hwang, Paul S.; Willoughby, Darryn S.. Mechanisms Behind Blood Flow–Restricted Training and its Effect Toward Muscle Growth. Journal of Strength and Conditioning Research 33():p S167-S179, July 2019. | DOI: 10.1519/JSC.0000000000002384 https://pubmed.ncbi.nlm.nih.gov/30011262/
- Cholewa J, Trexler E, Lima-Soares F, et al. Effects of dietary sports supplements on metabolite accumulation, vasodilation and cellular swelling in relation to muscle hypertrophy: A focus on "secondary" physiological determinants. Nutrition. 2019;60:241-251. doi:10.1016/j.nut.2018.10.011 https://pubmed.ncbi.nlm.nih.gov/30682546/
- Pope ZK, Willardson JM, Schoenfeld BJ. Exercise and blood flow restriction. J Strength Cond Res. 2013;27(10):2914-2926. doi:10.1519/JSC.0b013e3182874721 https://pubmed.ncbi.nlm.nih.gov/23364292/
- Early KS, Rockhill M, Bryan A, Tyo B, Buuck D, McGinty J. EFFECT OF BLOOD FLOW RESTRICTION TRAINING ON MUSCULAR PERFORMANCE, PAIN AND VASCULAR FUNCTION. Int J Sports Phys Ther. 2020;15(6):892-900. doi:10.26603/ijspt20200892 https://pmc.ncbi.nlm.nih.gov/articles/PMC7727422/
- Centner, C., Wiegel, P., Gollhofer, A. et al. Effects of Blood Flow Restriction Training on Muscular Strength and Hypertrophy in Older Individuals: A Systematic Review and Meta-Analysis. Sports Med 49, 95–108 (2019). https://doi.org/10.1007/s40279-018-0994-1
Garett Reid
Author