Blood flow restriction (BFR) involves the restriction of arterial blood flow into the muscle, while occluding or stopping the venous blood flow out of the muscle, which then creates pooling of the venous blood. With this pooling effect, blood flow restriction also causes oxygen deprivation in the muscles, enhancing metabolic stress, and encouraging muscle adaptation (strengthening) without the requirement of significant loading of the joints.
To put it more simply, you will be able to achieve targeted results with much lower loads and mechanical stress.
For instance, with traditional resistance training, the gold standard for achieving noticeable increases in muscle size lies around 70% of your one repetition max (1 RM). However, for some populations, high load exercises may not be appropriate or safe (think post-surgical achilles repair, or elderly patient recovering from a 2 week stent of pneumonia).
But isn’t that dangerous?
This technique appears to offer no greater health risk than training with high loads, while greatly reducing the mechanical stress to the joints. (Loenneke et al, 2011).
In fact, pooling of venous blood actually stimulates natural tissue plasminogen activator (TPA) to be released, which is the same derivative used for clot busting in hospitals for ischemic strokes. In this way, when applied correctly, BFR is safe and does not increase risk of clotting.
What is the mechanism or how does BFR accomplish the noted improvements?
That part is still largely theoretical. There are a few predominant theories at this time:
Cell Swelling (becoming less prominent)
It could be due to cell swelling (which trips a volume receptor of sorts, that then increases production of mTOR, which has been shown to be high following resistance training as well).
Oxygen deprivation (hypoxia) during BFR training leads to increased levels of lactate and free hydrogen in the muscle. The result is a decrease in pH, which encourages the production of growth hormone. Increased GH then stimulates increased levels of IGF-1 (insulin like growth factor), which supports muscle synthesis (increased production of HGH up to 290 fold- Takarada 2000).
Another theory proposes that improvement is elicited largely due to downstream affects of norepinephrine release (which prevents the decrease of protein synthesis usually seen with lack of activity).
Time Under Tension
There are yet other arguments for the fact that it’s still mainly about how much time the tendons/muscle units are under tension with BFR training as well.
The reality is that research is demonstrating positive responses to BFR that are not only beneficial, but safe. It likely involves multiple mechanisms working together.
Here are a few more notes to work through as we get prepare to discuss applications of BFR:
-BFR increases muscle protein synthesis in the elderly by up to 56% (Gundermann, 2012)
-Level of growth hormone was found to be elevated 10 minutes after activity, and remained elevated up to 40 minutes (Fujita, 2007)
-BFR has been found to increase collagen synthesis after as early as 2 weeks
-BFR decreases myostatin (which contributes to muscle protein breakdown) by up to 45%, which is comparable to high intensity training.
Summing it Up
In my clinical experience thus far with BFR, I’ve also noted decreased post-session or delayed onset muscle soreness despite a high RPE in the clinic (rate of perceived exertion) with all age groups, as well as significant reversal of functional decline in the aging adult population.
I don’t believe that any one specific training or rehab style fits into every case or with every client; however, this has been extremely beneficial in the clinic and with improving performance!
Stay tuned for more in this series in the coming days! If you’d like to find out more, or think you could potentially benefit from one-on-one physical therapy in the Daphne area, please feel free to contact us.
PT, DPT, OCS, CSCS, CF-L1
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