Jeremy Loenneke is an assistant professor of Exercise Science in the Department of Health, Exercise Science and Recreation Management at the University of Mississippi and has a PhD in Exercise Physiology from the University of Oklahoma. He is based in Oxford, Mississippi.
Blood flow restricted training is exactly what it sounds like. It involves restricting blood flow into the muscle you are training, and occluding – or preventing – blood flow out of the muscle.
In lab settings this is typically applied with specialised equipment but can also be applied with knee wraps in the gym. This type of resistance training allows a person to exercise at low loads – around 20-30% of their maximum – and results in muscle growth similar to that observed with higher loads of around 70% of their maximum.
It is important to remember that moderate blood flow restriction – around 40-50% of what it takes to cut off blood flow completely – appears to be just as effective as very high percentages. As such, as in many things in life, more does not necessarily mean better.
Lighter loads, same result
It was thought for some time that a muscle had to be exposed to repeated bouts of high-load training to make a muscle bigger and stronger, but applying blood flow restriction (BFR) allows this to happen at lower loads.
Lifting weights in combination with BFR has been shown to result in similar muscular adaptations as traditional high-load training. The benefits of this stimulus have been observed in trained, untrained, older, injured, and even some clinical-type populations. The benefit in using this stimulus is that you get substantial muscle adaptation with minimal recovery time because it does not typically result in a measurable level of muscle damage.
The benefits of BFR have been observed with a variety of exercises, both compound and single-joint movements. Additionally, some evidence suggests that muscles not directly under BFR, such as the chest, may also be improved. Most of the research is done with a leg extension and arm curl model but some studies have also found improvements in bench press and squat following this type of training.
How it works
It appears that both mechanical and metabolic factors are at work behind the effects observed with low-load resistance training in combination with BFR. This is different from high-load training, which is thought to be mediated largely by mechanical factors. When BFR is applied to a limb during exercise it causes the metabolites produced by the muscle to accumulate. In addition, the acute muscle swelling that occurs from applying BFR may also be important for muscle adaptation on some level.
Maximising muscle strength
Maximal muscular strength in a lift is very dependent upon the training principle of specificity. Thus, if a person only ever trained with low loads for a particular lift their maximal strength in that lift would likely be a little less than a group who trained that lift repeatedly with high loads, despite having similar changes in muscle mass. If maximal strength is something you are interested in, it would make sense to use low-load training in combination with BFR as a supplement to your normal training and not a complete replacement.
Minimising the negatives
The application of BFR has been shown to be a relatively safe stimulus. It doesn’t result in measurable amounts of muscle damage, it doesn’t appear to activate coagulation factors, and it doesn’t produce change in blood pressure greater than that observed with traditional training. Indeed, it often produces less of an increase.
However, I would caution those who have had lymph nodes removed that perhaps BFR may be contraindicated on that limb. There is no data that I’m aware of showing that it would be harmful but physicians typically don’t even allow blood pressure to be taken on the arm where they’ve been removed. In addition, those with underlying vascular problems may also want to be cautious. There is no data here either way, but playing it safe is not a bad thing.
Why you should try it
Can you not lift heavy weights, perhaps due to some type of injury? Do you need a type of workout for your deload week that will produce positive adaptation without negatively affecting recovery? Do you need a psychological break from lifting heavy weights?
These are all situations where you may want to include BFR into your training programme. It is important to remember that you don’t have to do BFR, but it may be a useful tool. BFR is just another protocol which may help improve your overall training progress.
Putting it into practice
For those wishing to try it out in a gym setting, I recommend using cheap elastic knee wraps for the lower body and narrower wraps for the upper body. Those using a wide wrap in the upper body may inhibit much of the movement and may also inhibit some adaptation below the wrap. That’s not definitive, just a possibility.
For most who are healthy and capable of lifting heavy weights, I would probably recommend using BFR as a supplement to their normal training. To illustrate, one could add it to the accessory work at the end of their workout or they could have a day set aside specifically for BFR.
Monday: Heavy lower body
Tuesday: BFR upper body
Thursday: BFR lower body
Friday: Heavy upper body
The protocol I typically recommend for most lifts is 30 repetitions for the first set followed by three sets of 15 at 30% of the maximum weight you can lift, resting 30 seconds between sets. For more complex lifts, such as the squat, I may reduce the repetitions to 20 for the first set followed by three sets of 12-15.
The 30-15-15-15 protocol is commonly used but that doesn’t necessarily mean it is the ‘best’. It just means that routinely produces favorable changes in muscle mass and strength.
I prefer to use the workload completed as a gauge for how tight the wraps are, provided you are using practical BFR. For example, you may not make all of the target number of repetitions for every set, but if you aren’t even getting close then the load is too high or the wraps are too tight. If you are sure the load is approximately 30% of your max and you aren’t getting remotely close to finishing all the repetitions, then the wraps likely need to be loosened.