Blood Flow Restriction (Occlusion Training)

Contrary to my typical monologues, let’s get straight to the point today because we have a lot to cover…

Blood flow restriction, occlusion training, Kaatsu method — all of these labels refer to the same technique; one that’s forced us to reassess our understanding of how hypertrophy works at a fundamental level.

For decades, we’ve approached training with the assumption that the shortest path to getting hyooge is through force-feeding our muscles more volume-load over time. This assumption (aka progressive overload) proved to be directionally correct and has become the backbone of modern periodization. Progressive overload is predicated on the model of myofibrillar hypertrophy — adding contractile units to muscle cells which make them capable of handling/producing more force.

But more recently, exercise physiologists began theorizing the existence of what’s called sarcoplasmic hypertrophy — increasing the volume within a muscle cell.

Every person who has knocked out a set of 20 biceps curls understands that something special happens when tons of blood gets trapped in a finite space…

Skin-splitting, shirt-tearing, head-turning, ego-inflating PUMPS!!!

Whereas, MH adds contractile proteins like myosin and actin, SH expands the workable space with more fluid and “non-contractile” units. By forcing tons of blood into a working muscle, it’s thought that we can induce SH independently of mechanical tension and traditional PO. Additionally, certain metabolites/byproducts of muscular contractions, as well as local hypoxia, stimulate receptors in and on the muscle cell that “turn on” anabolic pathways.

This all sounds pretty abstract and complex and hard-to-measure — and there’s actually quite a bit of debate around whether SH is a distinct model or an interesting side-effect of MH and PO (which I won’t get into here).

Suffice to say, abandoning tried-and-tested methods to pursue some physiological cheat-code is never a good idea (write that down). However, anecdotal practices (i.e. bro-science) often beat research labs to the punch; and weirder things than “the pump causes muscle growth” have retroactively been proven true.

IMO the main problem with shifting focus away from PO and towards metabolic stress is that doing so requires skill with program design. Creating the effect isn’t hard — increase rep ranges, slow tempos, shorten rest times, use supersets/trisets/dropsets, etc etc. Harnessing the effect so it’s supplemental to PO without causing runaway fatigue generation is the real challenge.

It’s in solving for this dilemma — finding a way to integrate SH theory into programming built to maximize MH — where we find utility in techniques like BFR.

So what is it?

BFR is the act of restricting venous return of blood from a working muscle. By allowing flow in but not out, we essentially trap all of those metabolites in the muscle, along with the blood volume. This creates a honeypot of paracrine signaling and cell swelling that propagates for as long as the trainee can tolerate the pain.

The result is a massive anabolic stimulus.

How to do it?

This is typically done with an elastic wrap or some sort of tourniquet. The wrap should be applied to the most proximal aspect of the appendage and with a ~7/10 tightness to allow continued arterial flow. The muscle should be able to contract normally and without obstruction.

Prescription can vary, but the goal should be to maximize volume density with lighter-than-normal loads (~20-30% of 1RM).

4 sets of 30/15/15/15 reps separated by 30 sec rest is often the clinical standard.

However, I’ve found it more practical at times to just aim for as many reps as possible in a given time limit (e.g. 5 min)

*Note: Only use BFR for muscles that can be proximally occluded like the biceps, triceps, hamstrings, quads, etc.

How often to implement it?

This is where things get complicated and it’s dependent on what BFR is being used for. When attempting to work around injuries or stave off atrophy, down-regulation isn’t the primary concern — BFR can be leaned into as needed until more load-bearing activities can resume.

But with healthy trainees, we should be cautious to not overuse BFR. Much like metabolic work in general, our bodies will find homeostasis much faster than when PO is the intent. Cycling BFR every 4-6 months in 3-5 week spurts is a great way to ensure that it remains a novel stimulus and continues to provide the hypertrophic effects we’re after.

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For years, BFR has been one of my favorite techniques to use for myself and with clients. However, there are risks as well. Make sure you understand these contraindications thoroughly before trying to implement BFR!

See here for a follow-up post detailing these risks.