An Update on Blood Flow Restriction Training
Once only in the domain of body building, blood flow resistance (BFR) training has made its way into the strength and conditioning of athletes and musculoskeletal rehabilitation. Improving strength without lifting heavy weights is why blood flow restriction training has gained popularity in recent years. So where are we at with the evidence, safety, and application of this emerging technique?
Blood flow restriction training (BFR) is a way of strengthening muscles at a low resistance. When training for strength in a traditional manner, resistance is typically set at 70% of 1 repetition maximum (1RM), whereas with BFR training it’s at 30%.
Some form of tourniquet in applied to the muscle or limb that is being exercised, either with a compression bandage, band, or pressure cuff (more on that later) reducing blood flow to the area. The mechanism of how BFR training works is still largely theoretical, however the most accepted theory is that the technique creates a hypoxic muscular environment causing high levels of metabolic stress in tandem with mechanic demand.
In turn, one or more of the following may occur to cause an increase in muscle strength and growth (1);
- Cell swelling
- Production of reactive oxygen species
- Intramuscular anabolic/anti-catabloic signalling
- Elevated systemic hormone production
- Increase in fast twitch muscle fibre recruitment
The usefulness of the technique is to be able to strengthen a muscle or an area with low loads when training with high loads is not feasible. In a clinical musculoskeletal rehabilitation setting this can have various applications such as during early stages of rehabilitation following ACL reconstruction or lower limb fracture, irritable patellofemoral pain, strengthening for tendinopathy, or those with osteoarthritis of the knee.
Image: Blood Flow Restriction Pressure Cuff
Let’s look at some key research on the topic.
Systematic Review and Meta Analysis
Two papers have combined the data of various research projects. Jeremy Loenneke and colleagues published a meta-analysis of low intensity BFR training in 2012 (2). At the time, 11 studies satisfied their criteria for inclusion in the review, and their conclusion was that BFR was effective in gaining muscle strength and hypertrophy when performed 2-3 days each week. At the time, the accepted ‘theory’ was that strength and hypertrophy could only be improved with resistances of 70% of 1RM or more, so this was a key paper that put BFR on the map.
A more recent systematic review and meta-analysis was performed by Luke Hughes and colleagues in London, with their paper being published in 2017. As there was more literature on the topic at this time, the authors included 20 papers in the systematic review and 13 papers in the meta-analysis. These analyses supported the work of Loenneke et al (2012), with the following conclusion and recommendations;
- Individualised BFR training may provide a comparable surrogate for heavy load training whilst minimising pain during training
- BFR training may facilitate early engagement in low-load strength training with limited joint stress in a broad range of clinical populations
Potential Safety Issues
I know when I’ve floated the concept of BFR training with some of my patients I’ve been met with a look of bemusement, occasionally horror. Maybe I need to work on my pitch.
All the names given to BFR training such as “vascular occlusion” and “hypoxic” training all sound like terms used on a ward round in the cardiology department. It’s not that bad – if you have surgery, a tourniquet is applied sometimes for hours, and no one thinks twice about it because it’s been done for decades. If you have your blood pressure taken it’s not that much different.
Maybe we can all dream up a better PC term. How about MOP “Metabolically Optimised Pressure” Training?
Jokes aside, what does the literature report on safety?
In another review paper by Jeremy Loenneke (3), they reported that BFR training appears to be safe in relation to (and compared with those observed with regular exercise);
- Cardiovascular system (central and peripheral),
- Muscle damage,
- Oxidative stress, and
- Nerve conduction velocity responses
Wong et al (2018) (4) narrowed the focus in on BFR training and people with hypertension. In a systemic review and meta-analysis which included 6 studies, they found that BFR exercise seems to be safe in patients with hypertension with no adverse events
If in doubt, get the opinion on you/your patient’s local doctor, although beware, as they’ve likely never heard of it (see paragraph 1 in this section).
Patellofemoral (knee cap) pain can be difficult to treat. The evidence is clear, get the quads stronger and patients generally get better. How you get the quads strong is the art in the science (you need to improve quads strength without irritating the joint), and BFR training may make things easier in the early stages.
Published in 2017 in the British Journal of Sports Medicine, Australian physiotherapist and researcher Lachlan Giles investigated BFR training in people with PFJ pain (5).
Seventy-nine people were allocated to one of two groups;
- Standardised quads strengthening (70% 1RM)
- Low load BFR (30% 1RM)
Both groups performed 8 weeks of leg press and leg extension under the conditions above.
The results – both groups improved. However, the BFR group experienced less daily living pain, and those with painful resisted knee extension had larger improvements in quadriceps strength from BFR.
Muscle atrophy occurs with injury and illness, however muscle mass and strength also decrease with age, by 3-8% per decade after the age of 30.
Resistance training has long been advocated for older adults, reducing the risk of osteoporosis and the signs and symptoms of numerous chronic diseases such as heart disease, arthritis, and type 2 diabetes, while also improving sleep and reducing depression.
So, is BFR training a viable option for older adults?
In another systematic review and meta-analysis (aren’t we lucky!?) Centner and colleagues from the University of Freiburg (6) investigated the effects of low load BFR training on muscle mass and strength in older individuals in comparison with a conventional resistance training program.
Eleven studies were included in this review, and the conclusions are as follows;
- During both low-load training and walking, the addition of BFR elicits significantly greater improvements in muscular strength
- Muscle mass was also increased when comparing walking with and without BFR
- In comparison with high-load training, LL-BFR promotes similar muscle hypertrophy but lower strength gains
As the emerging research demonstrates that BFR training appears to be safe and effective, focus is also shifting to the equipment that’s used.
Back in the day (2013-14) when I started messing around with BFR, I started with Theraband tubing and progressed after a while to compression bandages for my patients. The only advice I could offer was to keep the pressure “moderate”.
Things have kind of moved on, however with respect to the pressures that have been used in the studies, they vary between 60 to 270mmHg! The sweet spot seems to be 140 – 200mmHg, but don’t quote me on it.
Blood flow restriction training will no doubt remain an area of interest for researchers and clinicians, as it has such wide scope for so many populations. Being objective in the pressure applied, cuff type, cuff width, and limb circumference will become more important as the evidence develops further.
Image: B Strong Training System
I have no commercial interest here (including no commissions), however I have been using the B Strong Training System over the past few months and have been impressed.
The B Strong cuffs come in a number of sizes, and I’ve found the sizing to be correct, the materials sturdy, and comfortable when applied.
The method of inflating the cuffs is very straight forward via a bulb, and the connections work well - they’re easy to connect and detach. The industrial designers have done a good job as all the inflatable cuffs, tube and blub all package up nicely into a hardy case that can be transported easily.
There’s an app to assist with pressures, and a bunch of others things.
Blood flow restriction seems here to stay.
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- Hughes, 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.
- Loenneke, Jeremy P., et al. "Low intensity blood flow restriction training: a meta-analysis." European journal of applied physiology112.5 (2012): 1849-1859.
- Loenneke, J. P., et al. "Potential safety issues with blood flow restriction training." Scandinavian journal of medicine & science in sports21.4 (2011): 510-518.
- Wong, Marlon L., et al. "Safety of Blood Flow Restricted Exercise in Hypertension: A Meta-Analysis and Systematic Review With Potential Applications in Orthopedic Care." Techniques in Orthopaedics33.2 (2018): 80-88.
- Giles L, Webster KE, McClelland J, et al “Quadriceps strengthening with and without blood flow restriction in the treatment of patellofemoral pain: a double-blind randomised trial British Journal of Sports Medicine (2017) 51:1688-1694.
- 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.