Occlusion Training - The Theory of BFR Methods
Sep 18, 2020
More colloquially known as BFR, occlusion training refers to an implementation method that requires the trainee to use a tourniquet-like band to momentarily minimise the return of venous (superficial veins) blood from the working muscle back to the heart.
Sounds whacky
And to be fair, it kind of is!
But I love it and I think it has a pretty solid backing within the literature to date as well in regards to feeling confident in recommending it as a method of training to those who I think will benefit from it.
So let’s jump in and delve a little deeper…
FIRST LET’S UNDERSTAND MUSCLE GROWTH
First, let’s talk muscle growth and then we can discuss why cutting off blood flow may provide benefits in particular scenarios.
To grow muscle tissue, one must force it to adapt to a stimulus that it is otherwise not currently made to withstand. For a muscle to want to adapt and grow, it is recognised that the primary stimulus required to achieve this is a progression in mechanical tension over time.
We do this most simplistically by placing greater loads through the muscle both in an absolute manner (getting stronger) and by also increasing the total volume of load it can handle in a given session, week, month or year.
In short… we are talking about progressive overload!
We may refer to this type of growth as Myofibrillar Hypertrophy... The growth of actual muscle tissue.
Conversely, a secondary type of muscle growth known as Sarcoplasmic Hypertrophy is also commonly referred too, however, instead of the growth in this instance being actual tissue, it is thought to be more about an increase in intra-muscular ‘stuff’ rather than the actual tissues becoming thicker themselves.
Think carbohydrate retention (glycogen), water, sodium and things like creatine phosphate.
Now, muscle growth is by no means that simplistic, and despite the original school of thought being that one must get stronger to cause myofibrillar hypertrophy, there is more and more literature immerging that suggests metabolic fatigue may also play an integral role as well.
In the past, the simplistic view was this:
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Strength and hypertrophy = increase muscle tissue thickness
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Metabolic and high fatigue = increase in general muscle size (intramuscular stuff)
THIS IS WHERE BFR COMES IN
But BFR challenges this thought!
As a general rule, it is accepted that Type II muscle fibres are the ‘strength and power’ fibres, whereby they are recruited under heavy loads or in the back end of a set (the final few reps). Whereas Type I fibres are recruited from the beginning and were considered to be more responsible for endurance.
In case that’s not obvious, if you want to be bigger, you want more Type II hypertrophy.
Which is where BFR comes in and blows the roof off of the original theories of hypertrophy.
Originally used to minimise atrophy of an immobilised limb post-surgery (Takarada and Takazawa, 2000), BFR not only causes metabolic stress as expected, but it also appears to stimulate the activation of Type II muscle fibres at loads that would otherwise never achieve such activation.
Quite convincingly too, with only a 9% reduction in muscle size being seen in post knee operation patients using static BFR versus 20% in those doing nothing.
But how?
THE MECHANISMS OF BFR’S SUCCESS
Pearson and Hassain (2015) looked at the mechanisms of BFR and found that despite being primarily metabolic in its application of stress, BFR not only stimulated Type II fibres at loads lower than generally required, but similarly it also impacted mechanotransduction, muscle damage, hormone production, cell swelling and the production of reactive oxygen species.
These are all factors usually attributed to heavier loads
It is, however, important to note that these mechanisms of action are primarily theorised explanations as opposed to concrete evidence of scientific causation and may require further investigation.
Mechanisms aside… how does BFR actually stack up in the hypertrophy literature?
Some of the most recent research by Loenneke et al (2016) found a significant increase in muscle thickness as a result of BFR training using 20% of 1RM, with further moderate increases at 30% of 1RM and even up to 70% of 1RM when compared to the control group training without BFR.
The differences between 20-70%, however, were not considered to be statistically significant. For this reason, I would suggest maintaining a lower load when training with BFR as a heavier load doesn't appear to yield significantly greater results, yet contraindications such as increased blood pressure and heart rate may otherwise be at a higher risk.
SO… IS IT SAFE?
There is limited research on elderly populations suggesting that it may be a non-issue, however, at this stage, I think it is safer to err on the side of caution.
To reference one study, Yasuda et al (2016) found an increase in thigh cross-sectional area and strength on low-intensity BFR training with no greater benefit in higher intensity protocols. And despite the higher loads, no change in vasculature or blood pressure were seen in the elderly women tested as well
Which is a great indicator of safety in higher risk populations. Furthermore, Neto et al (2016) also concluded in their systemic review of low-intensity BFR training, that loads of 20-30% are safe for both blood pressure and heart rate.
Pretty cool shit if you ask me!
MY FINAL THOUGHTS
But as with anything, the important take-home message with BFR and its potential for implementation is to understand the context in which it is best suited too. For me, BFR is never and likely will never be a primary method used to achieve hypertrophy.
Rather, I have found great success with BFR when it was used to compliment a heavier block of training or to maintain muscle mass in periods of lower volume or load due to injury.
My advice is to do your own research into BFR and should you wish to use it, choose it as a means to supplement your current programming or to fill the void of a missing variable like load or volume in times of injury.
In the next article, I will delve a little deeper into the application of BFR so tune in again next time.
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REFERENCES
Yasuda, Tomohiro et al. "Thigh Muscle Size And Vascular Function After Blood Flow-Restricted Elastic Band Training In Older Women". Oncotarget (2014): n. pag. Web.
Neto, Gabriel R. et al. "Effects Of Resistance Training With Blood Flow Restriction On Haemodynamics: A Systematic Review". Clinical Physiology and Functional Imaging (2016): n. pag. Web.
Loenneke, Jeremy P. et al. "The Influence Of Exercise Load With And Without Different Levels Of Blood Flow Restriction On Acute Changes In Muscle Thickness And Lactate". Clinical Physiology and Functional Imaging (2016): n. pag. Web.
Pearson, Stephen John and Syed Robiul Hussain. "A Review On The Mechanisms Of Blood-Flow Restriction Resistance Training-Induced Muscle Hypertrophy". Sports Med 45.2 (2014): 187-200. Web.
TAKARADA, YUDAI, HARUO TAKAZAWA, and NAOKATA ISHII. "Applications Of Vascular Occlusion Diminish Disuse Atrophy Of Knee Extensor Muscles". Medicine and Science in Sports and Exercise32.12 (2000): 2035-2039. Web.
