Blood Flow Restriction training (BFR) is a technique widely used in the gym to potentiate increase in muscle mass. You may have seen it of even try, but does it work?
In this post we'll go through the science and biochemistry behind blood flow restriction training. Does it work, or it's a waste of money?
What is Blood Flow Restriction?
Blood Flow Restriction is a training technique performed using low loads in combination with blood flow oclusion. It aims to simulate the hypertrophyic effect of high loads (source).
Blood Flow Restriction was discovered and patented by a Japanase ex-footballer called Yoshiaki Sato.
He found out that using occlusion strategically could benefit his recovery from an ankle injury and minimize potential muscle loss.
Blood Flow Restriction Uses Occlusion Bands
The occlusion bands are mainly used in the upper and/or lower limbs.
By doing this, less blood is pumped through and there's less oxygen available in the muscle being contracted (source).
Science Behind Blood Flow Restriction
Induces Metabolic Stress
Blood Flow Restriction restricts oxygen available in the muscle being contracted.
Because arteries are stronger and more resistant than veins, the occlusion bands will "close" blood flow back to the heart, while some blood will keep flowing to the peripherical tissues. This leads to oxygen accumulation and higher metabolite accumulation.
Blood flow restriction can potentiate metabolic stress by increasing accumulation of metabolites in muscle cells.
The accumulated species will regulate different pathways and hormones to potentiate muscle hypertrophy.
Increases Muscle Activation
Blood flow restriction and metabolic stress increase muscle fibre recruitment (study).
More fast-twitch fibres are activated by inhibiting alpha motoneurons, supplying the action of slow-twitch fibres.
If there are more fibres recruited and activated, muscle contraction is enhanced and the ability of perform the exercise to a great intensity is also potentiated.
Potentiates Anabolic Pathways
Intracellular hydration down-regulates mTOR, and blood flow restriction seems to improve hydration (study).
In addition to that, blood flow restriction also potentiates myogenic pathways involved in satellite cells proliferation and addition of new muscle cells to muscular structures (study).
Blood flow restriction is also associated with a lower gene expression of myostatin (study). This protein negatively regulates muscle growth, and its down-regulation can potentiate muscle hypertrophy.
Hypoxia is induced by the use of blood flow restriction strategies. This is associated with higher mitochondrial biogenesis and msucle hypertrophy (study).
Not only that, but it may also potentiate the sympathetic neural activation of muscle, creating higher neural adaptations (study).
Restricted oxygen makes the exercise harder to be performed in terms of energetic availability. In this study, they found that blood flow restriction negatively affects muscle fatigue (study)
Does Blood Flow Restriction Work?
Blood flow restriction training protocols may work to take muscle hypertrophy to a higher extent.
But what happens in real life? Does Blood Flow Restriction work?
In this meta-analysis (meta-analysis), the addition of blood restriction induced higher increase in muscle size.
In addition to that, the called Kaatsu walk (walking with the occlusion bands) got better results in muscle size than walking alone.
In a calisthenic group using blood flow restriction, increases of muscle size were higher when compared to control. Blood flow restriction also increased the plasma concentrations of growth hormone (study)
Cross-Transfer Effect of Blood Flow Restriction
There is also some evidence supporting the cross transfer effect of interconnected muscles (study).
Blood flow restriction increases muscle hypertrophy when performing a biceps curl (50% RM) and leg extension (30%RM).
While both groups performed the biceps curl without occlusion, leg extension was performed both with and without it.
The group with occlusion showed higher muscle increase in the biceps, suggesting the cross transfer effect in the blood flow restriction group
Blood Flow Restriction training is a viable strategy to potentiate muscle hypertrophy.
Blood flow restriction works by inducing muscle hypertrophy by providing an hypoxic environment, increasing muscle activation and potentiating metabolic stress and anabolic pathways.
- BFR is performed using low loads of 25-50% RM and low rest times between sets
- The limited oxyegn provides hypoxic conditions and induces muscle adaptations
- Sleep deprivation is associated with lower muscle recovery and suboptimal muscle hypertrophy
- Fiber type I are highly activated during BFR, simulating the use of heavy loads
Recommended Use of Blood Flow Restriction
Blood flow restriction is not for everyone. This technique enables you to induce muscle adaptations without the need of using high loads.
But that doesn't mean adaptations are higher than with high loads.
Injured or bedridden subjects trying to mantain muscle mass could potentially benefit by 1) walking and doing normal activitities with the occlusion bands, and 2) accelerating muscle recovery by doing rehabilitation with occlusion bands.
Advanced trained subjects could also benefit from the use of Blood Flow Restriction, but it shouldn't be used all the time.
This strategy requires of high amounts of energy and muscle fatigue, being possibly conterproductive if done in excess.
During the performance of multi-joint exercise such as bench press or squat, the cross transfer effect of blood flow restriction training could potentiate the exercise (study)
Lastly, blood flow restriction could be used during the warmup of our sessions. The use of BFR could increase local blood flow on the muscle of interest and muscle oxygenation (study).
Practical Applications for Blood Flow Restriction
The use of occlusion bands require of practice and a bit of experience.
At first it might feel weird and even uncomfortable, but as you use them you will get used to it.
Blood Flow Restriction training isdone using low loads (25-50%RM) with low rest time between sets (30-60").
The goal of blood flow restriction is to accumulate metabolites and feel that 'muscle-burning'.
How to Use the Occlusion Bands
The occlusion bands are used on the limbs, both upper (arms) and lower (quadriceps).
Since there's no objectivity on the pressure exerted by the occlusion bands, you'll have to play around and get them tightly enough.
In a scale of 1-10, aim for 6-7 in both limbs. Legs are more likely to be under slightly higher pressure due to the bigger muscle size. So take that into consideration.
Muscle-burning and soreness after blood flow training is usual and you shouldn't be afraid of that.
Types of Occlusion Bands
These are the two main types of occlusion bands available:
- Elastic bands
- Belt bands
Elastic bands are more adaptable and easier to set up. They may lose tightness over time. Since you have no control over the pressure, they are sightly less accurate.
Belt bands are more accurate, as you can adjust them to your desired pressure. The belt and buckle might be uncomfortable and pinch your arm/leg once in a while
Periodize Blood Flow Restriction
Blood flow restriction shouldn't be used all the time. You should see it as a tool to induce muscle gains.
It's recommended to use it at the end of the session, when the high muscle fatigue doesn't compromise the rest of the session.
Leave it for later on the progression and leave that bullet for when you really need it.
- BFR is not for everyone and shouldn't be used abusively
- During warm-up, BFR could be used to potentiate muscle activation
- The use of occlusion bands require of practice and experience
- End of the session and/or late on the mesocycle are recommended for the use of BFR
Blood flow restriction is a useful technique to increase muscle hypertrophy.
However, not everyone should use them. Recommended use are mainly for advanced trained subjects, bedridden, or going through a muscle recovery.