Blood Flow Restriction Training

A breakdown of BFR for health and performance

From Pignanelli et al

Blood flow restriction training (aka KAATSU) was first introduced to me over a decade ago, in the context of adding hypertrophy to an athlete who would struggle doing any sort of traditional resistance training. I have been fascinated by it ever since and to be honest, it seems the more I read into it the more use cases there are. Far from the latest fad, though, it has been around since the 1960s (making it likely to stay around according to the Lindy Effect).

In short, blood flow restriction training (BFR) involves using cuffs to occlude SOME of the vascular flow, creating increased metabolic and cardiovascular stress during. The cuffs are applied in two locations (not at the same time); in the upper body this is around the upper arms and similarly for the lower body it’s around the upper thigh. There is increasing research by the day on BFR, and new protocols and ways of using the methodology continue to proliferate as do companies in the space.

What Are The Benefits of BFR?

I mentioned above that with mounting research into the topic I found BFR to be increasingly useful for almost everything - this is usually a trigger for most people’s BS meter, but this looks to be legitimate (the last intervention I was this impressed by was heat). As an example see the below quote:

“long-term benefits of BFR exercise, including increased muscular size, strength, muscular endurance, muscular power, and enhanced aerobic capacity, have been extensively reported in the scientific literature”

The research suggests a significant advantage of using BFR, and perhaps a driver of some benefits we are seeing as a result, is the fact that compared to higher load training; frequency can be higher. Training frequency is only one lever we can pull when talking about training adaptation but it’s nice to have another option (which traditionally goes away with increasing training experience).

In my mind, the benefits really boil down to being able to in-part dissociate metabolic and mechanical stressors from each other. Of course, the aforementioned heat can do this when it comes to more endurance type activities but BFR allows this dissociation in the resistance training realm (but no it doesn’t mean you can skip your ‘cardio’ bro nor does it mean bicep curls count for cardio). In both cases we are really changing the internal load (what we experience and adapt to) as a function of the external load (the load we are applying eg speed, weight etc).

What Does BFR Training Look Like?

Many of the initial studies in the space used BFR in aging populations for low load aerobic exercise (read; old folks walked with BFR) to good effect. In this setting it effectively added metabolic stress to people who were somewhat limited mechanically, generally inducing benefits in strength, endurance and some muscle mass. It is worth remembering that these populations have a low capacity, so almost anything will be stressful enough to induce adaptations (and hence an activity like walking can improve strength - even with BFR in younger populations this would almost certainly not be the case).
More recently it has entered the sports performance and rehabilitation spaces, with slightly differing methodology and goals.

“Although BFR exercise is commonly performed at low loads (20–50% of maximal strength), most studies report a pronounced metabolic response as confirmed by the accumulation of metabolic by-products, such as lactate, di-protonated phosphate, deoxygenated hemoglobin, inorganic phosphate, and hydrogen ions and often at similar levels as those caused by traditional high-load resistance exercise in many studies”

So you can see, load is low, and metabolic stress it high - meaning adaptation with a different fatigue profile, which is exceedingly helpful in those with limited mechanical stress tolerance (injury) or where we want to limit mechanical stress (perhaps nearer to a competition) because metabolic stress has a different recovery timeline.

In short, BFR is generally using low loads, higher repetitions and with cuffs in place to partially occlude vascular flow in the limbs of interest (upper or lower limbs). There are only single points in the upper and lower limbs where these cuffs are applied; basically just distal (further out) from the armpit and groin, or said differently, high up the leg or arm. Interestingly, as discussed above, reports suggest that the effects are more systemic than specifically local (hence single point of occlusion for the whole limb regardless of targets or exercise).

A word of warning, BFR can be uncomfortable, either through the use of the cuffs or as a result of the higher volume training with the partial vascular occlusion.

How Does BFR Work?

The short answer is we have many theories and no solid answers. Clearly the effects are more systemic than local and no doubt their genesis is a mixture of lowered delivery of blood or excessive build up of metabolites (we aren’t calling these ‘waste products’ because we are better than that) with a subsequent milieu and associated cascade of factors.

All of the above said, there is not shortage of speculation on potential mechanisms in the literature. Some potential physiological responses to explain the mechanism of action of BFR:

• Fibre recruitment - stimulating faster twitch muscle fibres due to the lower oxygen environment.

• Metabolic response - increased metabolites driving a greater response.

• Cellular swelling - secondary to build up of metabolites.

• Anabolic hormone response - probably due to metabolite build up.

• mTOR pathway (activation of protein synthesis) - likely driven by a mixture of the above.

Some authors (see the main figure at the top of this article) suggest other mechanisms, including vascular sheer stress and some neural mechanisms. The latter due to significant increases in rate of force development following BFR in some studies. Changes in the body’s ability to tolerate low oxygen availability are also suggested to play a role, including ion channel changes, better buffering capacities and improved oxidative capacity.

Any time we occlude blood flow or indeed induce high metabolic stress there is a the likelihood for increased angiogenesis (formation of new blood vessels) as a result of increased demand for oxygen at the working muscle. This is a fairly classic response to high intensity endurance training and likely higher volume resistance training to failure too. Hence it is certainly on the table that this is part of the benefit of BFR (and authors report likewise).

An interesting thought to ponder in this realm is related to pain tolerance. One study showed an improvement in pain pressure tolerance. Without going nerdy, an alteration in pain tolerance is both unsurprising (desensitisation is how the nervous system works) but also a potential for subsequent improvements. Said differently, if we can change pain tolerance, you can push harder and improve more in certain realms (not all, but certainly maximal repetitions which drive hypertrophic adaptation).

When Could You Use BFR?

The basics are going to be left largely unexplored here; to increase muscle mass and/or strength in these cases.
*Remembering these are correlated and related but not 100%.

Currently, as the below figure suggests, the established methods of using BFR include lower load resistance training and low intensity aerobic exercise. That said, it also suggests there are many emerging methods and these continue to evolve.

Some more specific and special use cases for BFR include:

• Pre and/or post surgery to aid in maintenance of muscle mass or augment training stimulus.

• A recent paper talked about the potential for use use of BFR in rehabilitation from bone stress injuries to aid in maintenance of both bone and muscle.

• Similarly another paper talked about its potential in use for an ACL reconstruction, crucially finding more than just increased muscle mass and strength specifically also finding an increased passive range of motion. Although another found no difference in this patient group.

• Phases of training where there is a need for low mechanical stimulus, which could be numerous - for instance a back injury preventing heavy squatting (though there are certainly other options in this case.

• Periods of time where there’s a lack of access to significant loads to train with. Think; travelling and unsure about what’s in the hotel gym (or not having one).

• During rehabilitation given the research suggesting an increased hypoalgaesic effect compared to conventional low load resistance training. (That’s right; exercise reduces pain, and more so with BFR in some cases).

From Scott et al

Originally a single article, I subsequently decided to split this piece into two parts.
For more on details on BFR and its application, make sure you are subscribed so that you receive next week’s article, which goes through specifics of when, how and who with respect to BFR. It also touches on certain use cases in the health and performance realms.

References

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