What is blood flow restriction (BFR)?

See our blog post on what blood flow restriction is, and how it works.

The following tables are extensions of a review paper by Patterson et al., 2019.

Set - up of BFR?

Table 1 describes the set-up of BFR, regarding where to place the cuffs, how to determine the appropriate pressure, and how long to keep them on for.

One thing to know note: cuff pressure must be set to % of arterial occlusion pressure (AOP), not % systolic blood pressure. What’s the difference? Essentially it comes down to measurement error between the devices. The best way to do this is using the BFR cuff to determine AOP and then setting it to 40%-80% of that.

AOP is the absolute pressure of the cuff that results in cessation of pulse. Once found, adjust cuff pressure to 40%-80% AOP for training.

Exercise Prescription with BFR

Table 2 describes how to go about determining exercise prescription in terms of sets, reps, load, rest periods, and training frequency to get the best result.

For the most part, training regimen needs to be similar to that of high-load training (3x/week for at least 6 weeks). In rare cases, high-frequency training (2x/day) has been applied as well, but only for short periods (1 week).

Other Effects (AKA Side-Effects), Risks, and Other Considerations of BFR

Table 3 describes the other effects of blood flow restriction. Everything from common (muscle soreness) to exceedingly rare (syncope and clotting).

Who should not use BFR?

Be cautious with using BFR with patients who have diagnoses of:

• Sick Cell Trait or Disease

• Recent Vascular Surgery

• Chronic Venous Disease

• Reynaud’s Phenomenon

• Bleeding Disorders (or who are taking blood thinners)

• Peripheral Vascular Disease

• POTS Syndrome

This is not a comprehensive list, and it may change over time.  Patients should not apply BFR without first consulting a physician or physical therapist about the risks and benefits.

How does BFR Work?

Mechanisms of BFR.

Blow flow restriction works through two main mechanisms:

1. Mechanical tension of muscle fibers - By applying a partial tourniquet to the limb, venous pooling and intramuscular tension allows patients to achieve high levels of mechanical tension during low-load exercise (20-40% 1 rep max [1RM]). This means the muscle feels like it is lifting heavy weight.

2. Metabolic stress - In parallel, increased levels of metabolic stress drive systemic hormone production and fast-twitch (anaerobic) muscle fiber recruitment.

Together, these stimuli promote gains in muscle hypertrophy and strength despite training with low-loads. (Pearson and Hussain, Sports Med, 2015)

Does BFR address muscle inhibition?

Not directly. Neural inhibition persists, but BFR does encourage selective activation of high-threshold fast-twitch muscle fibers. This means effects similar to high-training loads despite low-resistance in rehabilitation -- albeit inhibited muscle fibers theoretically remain unrecruited. That being said, it absolutely combats the metabolic atrophy cascade that occurs in the presence of muscle inhibition. See our other blog post on BFR for more on this topic.

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