I've always wanted to experiment with BFR (Blood Flow Restriction) training but I didn't want to fork out the dough for one of those pneumatic cuffs that would surely make the cute girl who works behind the desk run off to see if the gym's defibrillator is charged.
"Oh look, that poor man has to check his blood pressure between sets. I better be ready to whip out the paddles!"
I've always had the option of trying BFR training using cheapo, low-tech stretch bands instead, but the instructions on how to incorporate them in my training and how tight to wrap them for best effect was vague:
"They should be tight, tight enough to impede venous blood flow, but not arterial blood flow."
If you were instructing someone on how to practice auto-erotic asphyxiation and you gave them that kind of vague advice, I'm pretty sure you'd find that person dead in the closet, a noose around their neck, pants down around their ankles, and eternally draped by a shroud of shame and humiliation.
Clearly, there just wasn't enough good info on the subject. That's changed, though, as occasional T Nation contributor Brad Schoenfeld, PhD, and his colleague, Nicholas Rolnick, MS, just published a research-based guide to BFR training. In it, they discuss how they think it works, including how and when to best incorporate it in your training.
Following are some of the highlights from the paper.
In general terms, BFR uses bands or straps to partially reduce arterial blood flow while completely shutting off venous blood flow. This causes the blood in the limb that's wrapped to pool, which of course limits oxygen delivery and subsequently reduces the time it takes to reach muscular failure.
You can use lighter loads and they'll presumably work just as well as heavier loads. The usual rules determining hypertrophy still apply, though. Growth is still mediated by mTOR, but mTOR and its effects kick in earlier and to a greater degree when BFR is employed. Beyond that, BFR seems to employ two distinct underlying mechanisms to facilitate growth:
1 Metabolite-Induced Fatigue
BFR training, like conventional training, causes metabolites like lactate hydrogen ions, ATP, and inorganic phosphates to be formed, but the band(s) trap all that metabolic gunk in the limb. These lingering metabolites cause type 2 muscle fibers to be recruited earlier than they might with free-form exercise.
As these metabolites and fatigue increase, muscle activation increases and anabolic processes kick into gear.
2 Cellular Swelling
This process, like it sounds, involves the accumulation of fluid in the blood-flow restricted limb, thereby stressing the cellular matrix and activating "intracellular signaling pathways," which leads to growth.
Aside from those mechanisms, there's also evidence that BFR training enhances the satellite cell response to training. Satellite cells are little baby muscle cells that hang around the basal lamina of muscle cells, waiting to be called in after a muscle-damaging bout of training. At that point, they fuse with mature muscle cells and donate their nuclei and help with repair and growth.
Clearly, those pneumatic cuffs I mentioned in the opening paragraph are the best way to go when using BFR training. You either fill them up with air using a little palm pump, or you can have it done automatically by an attached or wireless computer.
However, not everyone has a spare $300 to spend on a glorified blood pressure cuff. That leaves elastic knee straps or specially designed BFR elastic straps, the latter of which are becoming increasingly available and increasingly sophisticated (I'll link to a couple of sources later on in the article).
The trouble with using conventional knee straps (either on your legs or arms) is two fold. For one, they're too thick. BFR bands should ideally be about 2 inches wide. Another problem concerns precision. It's commonly recommended that you wrap the legs or arms to a "perceived tightness" of 6 or 7, where 10 is "holy-shit-that's-tight."
As might be expected, studies have found that lifters using knee straps either under or overestimate the pressure by as much as 25%. Too loose and it's like wearing baggy underwear that keep slipping down around your ankles, i.e., it serves no purpose. Too tight and you risk gangrene, resulting in one or more limbs being sawed off and then having to staple up one of your shirtsleeves or pant legs for the rest of your life.
However, several visionaries have designed inexpensive straps for BFR training and studies have confirmed their effectiveness. Abe, et al. determined that pulling elastic cuffs to 10 to 20% of their initial length successfully mimicked a pressurized nylon cuff that's inflated to 40 and 80%, respectively.
Another group, led by Thiebaud, found that elastic knee wraps, stretched by 2 inches, or to a length corresponding to about 85% of thigh circumference, was a viable alternative to pneumatic cuffs.
But again, these findings applied to specially designed elastic cuffs and not the dirty, 4-foot long, 4-inch thick, Tom-Platz style stretch bands you carry in your gym bag.
Maybe the most valuable thing in Rolnick and Schoenfeld's paper was a full-page table that synopsized all the best available info on exactly how to incorporate BFR training into your workouts. Following is a synopsis of some of the most pertinent parts of that table:
- Frequency: 2 to 3 times a week during a heavy lifting phase for an extended period (over 3 weeks), or alternately, 1 to 2 times a week (for less than 3 weeks) during a de-load phase to shock the musculoskeletal system.
- Limb Occlusion Pressure (LOP): This term refers to the minimum pressure needed to completely restrict both arterial and venous flow, but gangrene isn't what you're shooting for. Instead, you're shooting for a percentage of LOP. Arms should be wrapped to 40-50% of LOP and legs should be wrapped to 60 to 80% of LOP.
- Number of exercises per session: It's variable, but most studies use either one exercise per muscle group, like leg extensions, while some other studies employed two exercises per muscle group, using one multi-joint exercise and one single-joint exercise.
- Rep scheme: The studies support higher reps, such as sets of 30, 15, 15, 15. Alternately, you can do multiple sets to failure, although that will, of course, increase recovery time.
- Maximum wear time: No more than 10 to 20 minutes, total. In general, though, deflate (or remove) after two exercises and wait a minute before re-inflating.
- Loads: 20 to 50% of 1RM.
- Tempo: 1-second concentric, 2-second eccentric.
- Interset rest: 30 to 60 seconds.
- Before or after heavy lifting: After.
- Multi-joint or single-joint exercises: Both.
The initial impulse might be to use BFR training for single-joint exercises like biceps curls, triceps extensions, leg curls, and leg extensions. That's all good, but they'll presumably work just as well with multi-joint exercises like squats and dips.
In fact, there's no reason you can't experiment with them on practically any exercise you do, including seemingly unrelated stuff like kettlebell swings.
BFR also has enormous untapped potential in helping injured physique athletes. Since it uses lower loads, injured athletes could still train and still make gains. Additionally, BFR seems to have a "hypoalgesic" effect, which simply means that it diminishes the pain normally associated with a particular activity.
Here's Dr. John Rusin with some related info:
As explained, buying a pneumatic air pressure cuff can be pricey, but there are low-tech versions available that were designed with BFR training in mind. You can buy easy on, easy off bands with buckles designed exclusively for the arms, like these.
While they still leave you guessing exactly how tight you need to pull them to approximate a 7 out of 10 comfort level, the model I linked to is at least has number markings so you can easily tighten them to the same degree on repeated sets or exercise sessions. You can also buy sets that work for both the arms and legs, like these.
Either way, BFR training seems to be a scientifically validated way to increase muscle growth and given the advent of various inexpensive alternatives to pneumatic or computerized cuffs, it's something that every lifter should, at some point, experiment with.
- Rolnick N et al. Blood Flow Restriction Training and the Physique Athlete: A Practical Research-Based Guide to Maximizing Muscle Size. Strength and Conditioning Journal. 2020 Oct;2(5):22-36.
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