Blood Flow Restriction (BFR) training is an advanced training technique that makes use of weightlifting cuff straps or wraps tied around a limb during exercise.
The goal of this training technique is to restrict the blood flow out of that limb, while still allowing blood to enter (arterial circulation).
The idea behind BFR training is that by restricting the blood from leaving the limb (venous return) it will also keep the byproducts of training in the muscles. Some of these byproducts, like lactic acid, are very important metabolites needed for muscle growth.
Lactic acid has a bad reputation as a byproduct of exercise, since it’s responsible for muscular fatigue. In reality, lactate actually has a strong anabolic effect and is essential for muscle growth. It serves a signalling molecule for hormones responsible for muscle growth. Lactic acid has been shown to have an enhancing effect on satellite cells, muscle protein synthesis and even testosterone – all of which are key elements in building muscle.
Benefits of Blood Flow Restriction (BFR) training
BFR training is also known by other names like Vascular Occlusion Training (VOT), Hypoxic Training & KAATSU.
Research shows that hypertrophy (muscle growth) can be achieved at much lower intensities when using the BFR strategy. This is potentially attributed to the increased production of growth hormone (GH) in the body during BFR training.
According to the American College of Sports Medicine (ACSM) guidelines, lifting weights at least 70% of your 1RM usually produces the greatest muscle building effects. Some studies have found that BFR training produced muscle growth at intensities of 50% of 1RM or less! This makes BFR a very appealing rehabilitation strategy for injuries, often prescribed by physiotherapists to allow the patients to increase their strength and muscle mass without putting heavy mechanical loads on the damaged tissues (muscles, tendons, ligaments).
The primary factors in building muscle are mechanical tension and metabolic stress. BFR has showed that despite the low level of mechanical load (<50% of 1RM) it can improve muscle growth by improving fast-twitch fibre recruitment, systemic and localised hormone production, cell swelling and others.
Risks of Blood Flow Restriction (BFR) training
The safety of BFR training is still being studied in clinical populations and you should always consult your doctor with any safety concerns. There are concerns that restricting blood flow can cause damage to veins, but studies have actually shown that restricting blood flow during exercise can increase the ability of veins to vasodilate, which actually increases blood flow in the long term.
It should be pointed out that restriction of blood vessels happens during “normal” resistance training as well. So what BFR training is doing is essentially mimicking this effect, but at lower intensity levels. Remember, BFR training has been shown to produce similar results in terms of muscle growth as normal training, but at considerably lower intensities.
Another concern that people have over BFR training is that it might cause blood clots. In clinical studies this has been shown to not be true and in fact, further studies have found that BFR training can actually increase the breakdown of blood clots.
The same concerns have been expressed over potential damage to the nervous system, because athletes had reported that BFR training can cause numbness in the wrapped limb. Researchers were lead to believe that BFR training could potentially be too taxing on the nervous system, however studies have found that there was no change in the speed at which nerve impulses are transmitted after 4 weeks of BFR training.
How to do Blood Flow Restriction (BFR) training
Blood Flow Restriction (BFR) training requires a wrapping a pressure cuff around a limb to the point where blood is able to enter the muscles on the limb via arterial flow, but is restricted from leaving the muscle. Common pressure cuffs used in BFR training are:
- KAATSU Band – A specialized device that, according to the manufacturer can be used safely by athletes and non-athletes of every age and ability. It works as an inflatable or fastenable band that is clipped around the ‘top of the limb’ (proximal). The device restricts venous return, making the blood ‘pool’ in the limb. The advantage of this device is that it gives you precise control over the pressure and tightness at all times.
- Elastic Wrapping – You will often see powerlifters using elastic wraps around the knees or elbows. Although the main purpose of wraps is performance enhancement or pain relief, new uses have been discovered. Using these to restrict blood flow by tieing them around a limb may be a practical and cheap option, however they may restrict both the arteries and veins. Research has shown a decrease in muscle growth, when the area has been wrapped too tight as a result of restrict arterial occlusion (blood coming in).
Applying a pressure cuff around the limb that you are working out will cause a buildup of metabolites that have been shown to induce muscle growth. At the same time, fatigue caused to the muscles signals your body to recruit the largest fast-twitch muscle fibers available to cope with the stress.
Studies have demonstrated that using a narrow cuff with a width of 5-9 cm can reduce the risk of restricting the arteries compared to cuffs with a width of 13+ cm. You want to avoid the occlusion of arteries, so make sure you don’t wrap too tight. The size of your arms and legs changes how tightly you should wrap, with research pointing out that athletes with smaller limbs are at a greater risk of occluding arteries, so be careful with it.
The infographic from bodybuilding.com below demonstrates how, where and how tightly to wrap when preparing for Blood Flow Restriction (BFR) training:
Blood Flow Restriction (BFR) F.A.Q
According to studies, BFR can increase muscle mass on its own and as a part of “normal” resistance training. Coaches have been recommending BFR for athletes during recovery training sessions as its shown to produce similar muscle growth at lower intensities than “normal” resistance training.
Studies have shown that the closer you get to failure, the more fast-twitch muscle fibers are recruited. Since BFR activates large fast-twitch muscle fibers, training till failure at low-intensity can be a great way to achieve optimal muscle-fiber recruitment.
Studies have found that while BFR training causes more fatigue compared to non-BFR training of similar intensity, there is no increase in muscle damage or decline in power 24 hours after it. Because of the lesser recovery demands, studies have shown that BFR training can be done 2-3 times per week.
This article first appeared on GYMNASIUMPOST.com on 22nd May, 2020.