Becoming fitter, stronger, and more functional is an endeavor that many of us attack with rigor every single day – and I use the word attack very deliberately here because to achieve these things you typically need to be willing to work hard.
Or at least that’s what most of us thought…
You see, there is a new modality of exercise known as Blood Flow Restriction Training that has taken the research world by storm because it appears to fly in the face of this common suggestion. But what is it? What does it actually do? And does it really work?
What is Blood Flow Restriction Training?
Blood flow restriction (BFR) training (also known as KAATSU training in certain circles) is a unique modality of exercise that involves training with an external constricting device applied to the proximal limb musculature.
The Science of Blood Flow Restriction Training
This is often done with blood pressure cuffs, elasticated muscle wraps, or specific blood flow restriction devices, with the intent to physically restrict arterial blood flow into the muscle, while also occluding venous return from the muscle.
In doing so, BFR training causes a decline in both oxygen delivery to the limb, and metabolite clearance from the limb – thus creating an extremely stressful physiological environment within the muscle tissue.
This environment has been shown to cause large increases in exercising heart rate, enhanced muscle fiber recruitment, and greatly intensified systemic hormone production (with emphasis on a number of anabolic growth factors) (Pearson, 2015). And the point of all this?
To stimulate physiological adaptation, while minimizing mechanical load.
This means that BFR training may offer a mode of exercise that can cause improvement in strength, fitness, and function in scenarios where high-intensity training may not be suitable – such as planned periods of reduced training intensity (or ‘deloads’) in athletic populations, in musculoskeletal rehabilitation settings, or even in clinical populations. Pretty cool, right?
The Benefits of Blood Flow Restriction Training
There are some serious benefits that come with BFR training in a number of different settings, making it one of the most useful training methods on the planet.
Blood Flow Restriction Training for Strength and Hypertrophy
Given the unique physiological state that BFR training has been shown to elicit within the muscle tissue, it makes sense that it has the capacity to improve muscle strength and size without the need for high mechanical loads.
Something that the research has shown time and time again. In fact, simply performing four to eight weeks of BFR resistance training with as little as 20-40% of one repetition maximum (1RM) has been shown to be enough to stimulate significant muscle hypertrophy in trained healthy adults (Loenneke, 2012).
With this comes an increase in strength that is often comparable to that caused by traditional resistance training across that same time frame.
Now just to be clear – loads that correspond with 20-40% 1RM are normally too low to elicit either hypertrophy or strong response. Which obviously suggests that BFR training in this manner is highly effective.
If we delve into this a little bit deeper, there is also a growing body of research demonstrating that weight training used in conjunction with BFR also has the capacity to cause significant improvements in muscle strength and size in older adults.
Which is pretty impressive when we consider that this is a population that typically needs to work extremely hard to see any improvements in muscle size or strength.
Moreover, these increases have also been shown to correspond with substantial improvements in functional capacity (Ladlow, 2018).
This suggests not only with this unique training modality cause large improvement in muscle strength and size, but that these improvements will also carry over to real-world scenarios.
Taking all of this into consideration, this makes BFR training the perfect means of causing substantial improvements in functional strength in those individuals who are not necessarily capable of performing high-intensity strength training (Centner, 2018). Within this, it also offers a means to improve metabolic health and stave off age-related diseases such as sarcopenia in older populations.
In short, it’s seriously effective.
How to use Blood Flow Restriction Training for Strength and Size
As BFR training is performed with the intent to maximize metabolic stress, it is performed in a slightly different manner to traditional strength training methods. With the cuff attached to the proximal portion of the arm or thigh, choose a weight that corresponds to around 30% of your 1RM.
- Perform 30 repetitions in a slow and controlled manner
- Rest for 30 seconds
- Perform another 15 repetitions
- Rest for 30 seconds
- Perform another 15 repetitions
- Rest for 30 seconds
- Perform a final set of 15 repetitions
And that is it!
This protocol can be performed for a multitude of body parts, and for numerous exercises – although most of the research has been performed using isolation exercises such as knee extensions, hamstring curls, bicep curls, and tricep extensions.
Blood Flow Restriction Training for Aerobic Fitness
Given the extremely potent effect that BFR training has been shown to have on strength and hypertrophy, there appeared to be a reason to test its potential applications with aerobic exercise. And the results have been impressive, to say the least.
Simply walking or cycling at exercise intensities as low as 30% of your maximal aerobic speed (often the equivalent of a brisk walk or gentle cycle) has been shown to cause significant improvements in aerobic fitness and performance in young adults after as little as two weeks of training (Bennett, 2018).
Similar results have been observed in older adults, with those improvements also coming with increases in numerous measures of functional capacity – again demonstrating that these improvements also have the potential to enhance the ability to live daily.
While this area of research is still relatively new in the grand scheme of things, there is enough evidence to suggest that BFR can be used in conjunction with aerobic training to cause significant improvements in aerobic fitness and performance.
In athletic populations, it may, therefore, provide a means to maintain (or even improve) fitness during times of intense competition when high levels of mechanical stress are not desirable.
Similarly, in both older and clinical populations, it may provide a way to elicit vast improvements in both aerobic fitness and cardiovascular health when high-intensity exercise may not be safe or appropriate.
How To Use Blood Flow Restriction Training for Aerobic Fitness
Somewhat different to using BFR for strength and hypertrophy, there are several different protocols appearing within the literature, some of which seem to be slightly more effective the others.
With this in mind, we simply recommend applying the cuffs to the proximal portion of the legs, and either going for a brisk walk, a light jog, or a gentle cycle for 20-40 minutes, 3-5 times per week for a total of 6-8 weeks.
This should provide more than enough opportunity to stimulate significant physiological adaption while keeping the exercise intensity low enough to reduce any central or mechanical fatigue.
Blood Flow Restriction Training for Cognitive Function
In conjunction with the above two training modalities, there has also been some research surrounding the implications that BFR may have on cognitive decline and the maintenance of normal mental health (Törpel, 2018).
You see, aging is typically accompanied by both a decline in both physical and cognitive capabilities – with a decline in one having a very strong relationship with a decline in the other. This indicates that they are heavily linked in some capacity.
Interestingly, there is a small body of evidence showing that improving physical capacity through resistance training can also have a positive impact on cognitive health and function.
You see, the metabolic stress caused by resistance training leads to a large increase in the secretion of numerous hormones that promote tissue growth – one of which is called insulin-like growth factor 1 (or IGF-1).
While IGF-1 is most commonly known for its ability to stimulate muscle growth, it can also cross the blood-brain barrier, where it physically enters the tissues of the brain.
Once in the brain, it causes the growth and development of both nervous system cells and synaptic processes, a heightened state of neuroprotection, faster rates of axon outgrowth, and enhanced brain cell maturation. The result of which is enhanced cognitive function.
Alternatively, a relationship between low levels of IGF-1 and both age-related cognitive decline and an increased risk of neurodegenerative disease has also been shown.
With all of this in mind, the increased metabolic stress caused by BFR resistance training causes even greater improvements in IGF-1 secretion – which indicates that it may indeed offer an even more potent means of improving cognitive health and function than resistance training alone!
Related Article: How to Improve Your Aerobic Capacity – Tips & Tricks
Blood Flow Restriction Training for Rehab
Using the above information, it should become pretty apparent that BFR training is the perfect way of training to enhance rehabilitation protocols.
While we know that improving strength and muscle growth is essential to restoring stability and function to any injured muscle and joint tissues, an injury typically limits our ability to perform exercise at a high enough intensity to actually elicit those adaptations.
Which is exactly where BFR comes in. By promoting muscle growth and increases in strength at lower exercise intensities, it facilitates the rehabilitation process in a very low-risk manner (Hughes, 2017).
This means that you can commence training earlier into the rehabilitation process than you would normally, fast-tracking the entire process. Pretty amazing really.
Is Blood Flow Restriction Training Safe?
Now, for the most part, BFR training has been shown to be very well tolerated – even in highly clinical populations.
However, there are a few caveats that need careful consideration (DePhillipo, 2018).
Firstly, you want to make sure that the cuff you are using is fairly wide (greater than 11cm is a good start). This better distributes the external pressure the cuff places on the muscle tissue, reducing the risk of bruising and any associated discomfort.
Secondly, you want to ensure that you use a reasonable cuff pressure.
Using blood pressure cuffs, most people recommend a sustained pressure of between 140 and 160 mmHg. This is high enough to allow venous pooling, but not so tight that it will become uncomfortable.
Finally, be aware of how you are feeling.
While the sensations associated with BFR training can be a little unpleasant, it should not be painful or overbearingly uncomfortable. If you find yourself experiencing an extreme sensation of pain, cease exercise immediately.
Take Home Message
While still undoubtedly a developing area, blood flow restriction training appears to offer an extremely potent method of training that can be applied to both resistance and aerobic exercise modalities.
As a result, it can cause significant improvements in muscle strength, muscle size, aerobic fitness, functional capacity, and even cognitive function while using very low exercise intensities.
This makes it the perfect means of eliciting a positive training effect when high-intensity exercise modalities are unsafe or not suitable.
Pearson, Stephen John, and Syed Robiul Hussain. “A review on the mechanisms of blood-flow restriction resistance training-induced muscle hypertrophy.” Sports Medicine 45.2 (2015): 187-200.
Loenneke, Jeremy P., et al. ” Low-intensity blood flow restriction training: a meta-analysis.” European journal of applied physiology 112.5 (2012): 1849-1859.
Ladlow, Peter, et al. “Low-Load Resistance Training With Blood Flow Restriction Improves Clinical Outcomes in Musculoskeletal Rehabilitation: A Single-Blind Randomized Controlled Trial.” Frontiers in physiology 9 (2018)
Centner, Christoph, et al. “Effects of Blood Flow Restriction Training on Muscular Strength and Hypertrophy in Older Individuals: A Systematic Review and Meta-Analysis.” Sports Medicine (2018): 1-15.
Bennett, Hunter, and Flynn Slattery. “Effects of Blood Flow Restriction Training on Aerobic Capacity and Performance: A Systematic Review.” The Journal of Strength & Conditioning Research (2018).
Törpel, Alexander, et al. “Strengthening the Brain—Is Resistance Training with Blood Flow Restriction an Effective Strategy for Cognitive Improvement?.” Journal of clinical medicine 7.10 (2018): 337.
Hughes, Luke, et al. “Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis.” Br J Sports Med 51.13 (2017): 1003-1011.
DePhillipo, Nicholas N., et al. “Blood Flow Restriction Therapy After Knee Surgery: Indications, Safety Considerations, and Postoperative Protocol.” Arthroscopy techniques 7.10 (2018): e1037-e1043.