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The Basics of Blood Flow Restriction

by Adelle Smener, DPT

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Have you ever been to physical therapy or the doctor and they tell you that the key to your rehab is STRENGTH? But what does that really mean and how can you successfully achieve this strength or hypertrophy? Unfortunately, doing 75 bodyweight squats just isn’t going to cut it... unless you’re doing them with Blood Flow Restriction, otherwise known as BFR.

Traditional strength training involves high load resistance training at > 60-70% 1RM, aka REALLY HEAVY. In the rehab world, however, that isn’t always possible, as individuals coming to PT are often load-compromised, meaning they just can’t lift that heavy quite yet. Why? Maybe it's painful. Or maybe they just had surgery. Or maybe they've never trained at high loads. Either way, being load-compromised doesn't mean you can’t get STRONG. While the science behind Blood Flow Restriction training is nowhere near new, its growth and functional application in the rehab setting is relatively new-ish.

BFR uses a specialized tourniquet system to decrease blood flow to your limbs. The tourniquet, or cuff, is placed at the base of the arm(s) or leg(s) and occlusion can range anywhere from 40-80%. Sounds kind of scary, right? But hear me out. The tourniquet system, if standardized in the clinic and FDA-approved, should be calibrated to your specific needs and can be objectively measured to ensure 100% safety throughout your exercises. There are various brands of bands, straps and cuffs. However, only 3 have been FDA-approved, meaning these are the most accurate, research-based and most importantly, SAFE when implemented by someone who is trained in BFR. Once the cuff is placed on the desired limb, that respective limb’s limb occlusion pressure (LOP) is measured. This tells you at what pressure 100% of the venous and arterial blood flow is occluded. Then you simply do a little math, or maybe use a calculator to be safe, and occlude to the desired arterial blood flow percentage. Most research has shown 40-50% occlusion and 70-80% occlusion in the arms and legs respectively is needed for maximal benefit.

But how does it work? Well that’s the coolest part! To simplify it, there are 2 types of energy systems our body uses to exercise: aerobic and anaerobic. Typically, when we are running, cycling and walking, we're predominantly tapping into our aerobic energy system. This means we can exercise for longer periods of time without getting tired because the body does not need to recruit as many muscles to perform the task! On the other hand, strength training and heavy lifting use predominantly anaerobic metabolism, which occurs without oxygen but forces the body to recruit A LOT more muscles to lift the heavy weight. We can’t do this forever though, as we would get really tired! Interestingly, we can get STRENGTH and HYPERTROPHY gains lifting very light loads all the way to failure, but this could take a long time! It would be like picking up a 3lb dumbbell and curling it for 10 minutes straight! Not only would it take forever, but it would result in significantly increased muscle damage as well.

However, by applying the BFR cuff at a standardized pressure, we can restrict a certain percentage of blood flow to the arm/leg and force the muscles to work a lot harder, even with that same light 3lb dumbbell! When we decrease the amount of oxygen available to muscle, it forces the muscles to call upon more motor units and switch from aerobic to anaerobic metabolism, comparable to lifting heavy weights! And TA-DA - we have STRENGTH AND HYPERTROPHY gains without heavy load!

If I don’t already sound like a used car salesman... WAIT THERE’S MORE. Not only has BFR been shown to improve strength and hypertrophy, but newer research shows added benefits such as:

  • Improving exercise tolerance

  • Decreasing pain

  • Augmenting tissue/bone healing

But there is a catch. As previously stated, BFR should only be used by trained individuals, as there are some relative contraindications. So if you think you would benefit from some BFR in your life, or just want to learn more, keep your eye out for more fun BFR facts throughout this blog series, on our Instagram @evolutionptfit, or give us a call to schedule an appointment!

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