Here’s a funny thing about fitness:

We don’t know how muscle grows.

Sure, we have some good ideas as to what conditions create muscle growth, or hypertrophy, and bodybuilders have been using these method for centuries at a minimum to build bigger muscles.

But no one actually understands the full depth and breadth of the interactions on a cellular level to the point where they can say definitively: this is how muscle growth occurs.

The closest thing that we really have to a map of the territory is Brad Schoenfeld’s seminal paper, “The Mechanisms of Muscle Hypertrophy.” Read the paper if you like, but the conditions can be summarized and memorized very easily:

1. Mechanical Tension: The muscles lengthened under load.
2. Muscle Damage: Micro-traumas to the muscle tissue.
3. Metabolic Stress: Byproducts of muscle energy utilization build up in the muscle.

When you have one or more of these conditions the result is that the muscle grows. Really, it’s as simple as that.

Therefore, it stands to reason that if you can increase one of those factors, you might get more hypertrophy. Might.

In the 1970s a young Japanese man started experimenting with restricting blood flow return in the hopes of increasing the build-up of metabolites and stimulating greater muscle growth. As the story goes he applied his techniques very successfully when he underwent knee surgery for torn ligaments and after six months in a plaster cast his muscles hadn’t atrophied at all thanks to his protocol. He later went on to study the method at the University of Tokyo where it was dubbed “Kaatsu training.”

The broad strokes are simple: Restrict return blood flow around the muscle group, and then perform a lot of relatively light reps to build up metabolites.

For reasons that should be fairly obvious this works best on discrete muscle groups that are easy to occlude, like the arms or legs. It would be hard to do on your lats.

Now this is where I have to tell you I have always been extremely hesitant and critical of BFR training. The weight of evidence is clear that it is effective. In short, it works. But the reality of occluding blood flow is always going to increase risk, and the limited nature of the body of research may not fully amortize the risks in a wider population. I would suggest you pursue this method with extreme care. I would argue that it’s abnormal to occlude blood flow beyond what is caused by the swelling of muscle under normal training circumstances, and there may be second-order effects that haven’t been picked up. Personally, I would never use this with clients. Additionally the risk of injury or damage under improper execution is extreme, and as with any complex procedure there is always risk that someone will screw it up.

Now that you know where I stand on it, and you are taking your own personal responsibility and making an informed decision, here’s how to do it:

The Method

You’ll need a way to occlude blood flow. What prompted this little experiment was a Dutch company launching a Kickstarter for inexpensive and very functional BFR straps sending me a pair to try out. I have no financial ties or incentive with the company, but I can tell you they work and the price is fair for a tool that makes it easier. You could use any old gym band, but it can be extremely uncomfortable to get the tension right.

Speaking of tension, the goal is a 7 out of 10, where 10 would be extremely painful and completely constricting bloodflow. If your limbs get tingly or numb it is too tight.

One way to approach it is to superset opposing muscle groups and then do three sets of 30-15-15 reps. So like in the video you might start with curls, do tricep extensions, and then go back to curls.

You do this in one continuous set, paying attention to keeping a slow-ish methodical tempo throughout. Obviously if you’re starting with a set of 30 you’re going to want to go pretty light. The goal here is not to create a ton of mechanical tension, it’s simply to build up those metabolic byproducts.

When you’ve completed all 60 reps, release the cuff. Don’t release it in between.

Here’s a short video of an arm session with the Marshall Roy the other day:

Recently I was talking with my wife, Jen, and I had mentioned that my friend Robb Wolf was sending over an early copy of his next book about food and the brain, and Jen asked “Is Robb still pretty big on low carb/ketogenic diet?”For those of you who may not be familiar the basic idea between very low carb and/or ketogenic diets is that the body absolutely needs fats and protein to sustain function, but can actually function quite well without really any carbohydrates. In the literature low carb diet can mean an amount that is actually relatively high, so when we talk about low carb in this context we’re talking under 50 grams per day. Going under that floor will put the body in a state called ketosis where the body will generate fuel for the brain from fat. Suffice to say you also eat a ton of fat to make up for the calories you’re not getting from carbs.

I’m not going to get into all the pros and cons of ketogenic diets because that’s not the point at all. Suffice to say low carb made a big splash a few years ago and has since faded in popularity, as diets often do.

The rub is this: The preponderance of scientific evidence that we currently have says that ketogenic diets may be interesting for some very specific indications (such as epilepsy) but that it is absolutely crap for high performance athletics or sport.

This is important to understand. As of what we know right now there isn’t a credible sports physiologist or nutritionist in the world who would recommend that any athlete who wants to be able to perform at the highest possible output go on a low carb diet.

However. And this is the big BUT. It seems like there might be some people out there who actually CAN perform extremely well on low carb diet. Even at high demands and intensities of exercise where normally carbs are essential to generating and maintaining output.

But the data hasn’t caught this, and what I think is most important for you to understand is that it may never.

The scientific approach is not intended to and can not give us “answers” or end points. It doesn’t work that way. Science works in averages, probabilities, and standard deviations. In fact, in a sense it doesn’t even tell us anything about YOU. It tells you about what was or wasn’t true about some other group of people, and the likelyhood that it applies to you.

What is supported by the bulk of current evidence should be thought of as a best practice or a starting point.

So if you’re going to figure out how to eat to win at your athletics, you’d be best served by starting with a moderate to high carbohydrate diet.

However, if in doing your own n=1 (the number of participants in the study equals one, you) experiments you do an experiment to try a low carb diet and you find that you are able to maintain or even improve performance then you would be an absolute fool to go back to your high carb diet because “science says this is correct.”

The ultimate science experiment is that one you run on yourself to get your own ever-changing answers.

Which brings us back to my friend Robb. Yeah, he’s a pretty big advocate of Paleo and low carb diets, but he recognizes that individuality and context is king and acknowledges that it might not be ideal for everyone. He knows he actually performs better on low carb diets, and that some people will perform poorly on low carb diets so they shouldn’t use them.

Bottom line is this: Use the scientific literature to figure out where to start when you don’t otherwise know, but don’t get hung up on it, because you may be the outlier they tossed out of the data.

I love analogies. I think they’re super useful in helping us understand the world. Jen sometimes makes fun of me because I’ll try to build an analogy and it will fall flat, but in general I think I’m pretty good at creating analogies to explain concepts.

For example, a car’s check engine light is a pretty good analogy for pain in the body. Depending on how much you know about cars you know that the check engine light can mean anything from low oil pressure which means impending doom and your engine could literally grind itself into metal shavings in the next few minutes, or it could mean your gas cap is loose and needs to be tightened. The only way to know for sure is to take it in (or get a reader) and read the codes to see what is going on. Pain is similar. Sometimes it just means you need to change your positioning a little bit, and sometimes it means you have cancer.

The problem with analogies is that they fall apart when you try to explain complex non-linear systems with them.

So let’s take the old “bucket” analogy for stress.

You have a bucket and in goes all of your stress and the bucket can fill up but it can only take so much and then when it overflows ostensibly you’re fucked.

The problem with this is that it’s totally linear and totally negates the complexity of stress.

I call it the version 1.0 understanding of stress. Basically stress is bad and when you get too much of it then it’s really bad.

So you try to extend the analogy a little bit and you poke some holes in the bucket, and you add a tap that is constantly trickling into the bucket and you say “OK now you have all of this stress coming into the bucket, some of it is good and some of it is bad. Stress is constantly leaving the bucket through the holes in the side but if you overflow the bucket you’re still fucked.”

This is better. You’re starting to move into the version 2.0 understanding of stress in that everything is a form of stress and there is good stress and bad stress (eustress and distress.)

But what if I told you that some of the water coming into the bucket could mix with elements in the bucket causing some of the holes in the bucket to either shrink or enlarge changing the rate of outflow, and then that one stream into the bucket isn’t sufficient to explain it so you’d have multiple streams, and then that the actual shape and size of the bucket could change based on the streams in and out and…

You can see where this is going. The analogy falls apart because you can’t explain a complex system using a simple one.

But it’s been useful to understand the progression in understanding stress. Now let’s ditch the metaphor.

Think of stress as nothing more than a signal or input to the body. When you do a bicep curl there is a cascade of signals, but the main message is “this area of the body is going to be stressed” and the healthy body says “ok, let me lay down some more tissue there to make it more resilient to stress in the future.”

When you eat food you’re providing building blocks but you’re also signaling that building and restorative processes can commence – protein specifically kicks off muscle protein synthesis. When you sleep it’s a signal that a whole host of restorative, autophagy, and cleanup processes can begin. When you are scared or in fear it’s a signal for the body’s defensive processes to kick in – the pulse quickens, hormones are released, the eyes dilate to take on whatever caused the stress.

One of the keys to really, truly understanding stress is knowing that the effects are associated to the stress signal, not caused by it.

As an example, the first time you jump out of a plane you are going to experience the fear response I referred to above: your pulse quickens, adrenaline is released, your focus narrows, you may experience time dilation in which everything seems to happen slowly. Most skydivers can’t tell you anything about the first skydive other than that they successfully pulled their parachute and landed.

On your 500^th skydive you can tell each of your five partners what they specifically could have done better with their body position, ask them if they noticed the other plane pass pretty close by, and remember that you had to reach down to pull your shoe back on when it came loose. If your heart rate and hormones had been monitored there would have been no change.

Same stress, same person, completely different effect. So what’s different? The context.

Stress + Context = Response

This is why what is distressful for one person, say running 3 miles, is totally eustressful and restorative for another person. Or for the same person at different times in their life!

Understanding this you can begin to comprehend why the prescription for a restorative or eustressful intervention may not be the same for two different people under intense “life” distress. Again, an example is helpful:

Two middle-aged men who are otherwise identical are having an exceptionally stressful week at work and at home. The only difference between the two is that one has lifted heavy his whole life and the other hasn’t lifted much at all and has only recently started strength training. Psychologically our middle-aged-meathead loves training and finds it a release and escape from his worldly concerns, while our new trainee is enjoying his new routine but finds it somewhat exhausting.

How do you plan their training sessions?

If you’re an average coach or trainer you will back off their session to make it easier because you understand that an overload of stressors can turn almost anything into distress and you’ll send them off with an admonishment to get more sleep.

But the great coach will go further. They’d back off the training intensity for the new trainee because they understand that in context the mere act of doing any strength training at all is stressful enough for this guy and it doesn’t need to be a hard week on top of what he’s already got going. But our meathead thrives on training and the stress response he gets from hard training is more like what you’d see from something that actually promotes recovery rather than something that is destructive or distressful.

The great coach will take advantage of knowing this, they’ll also know that volume more than intensity tends to wear down the experienced lifter, and they’ll take advantage of the high sympathetic nervous system tone during this stressful week to have the lifter set some new maxes – doing essentially the opposite of what might sound intuitively best. But in context it’s actually better, because our meathead friend’s body is physiologically primed to respond best to exactly that.

Only in knowing, or predicting, what the response is can you judge the stressor. This is version 3.0 understanding of stress.

One reason biofeedback through ROM or HRV can be useful is that you can use the past to inform your predictions about the future. I know several folks who use their HRV religiously and they know what types of training stimuli will push their HRV up or down based on where they are at the moment. I’ve seen ROM biofeedback used successfully for years to predict what stimuli are going to be responded to positively or negatively. You can of course only know – via measurement – after the fact of the stimulus, but you can make pretty good predictions if you look at the patterns of history.

If you take one thing away from this article it should be that stressors aren’t defined by physical therapists, marketers, doctors, meditation teachers, strength coaches, or anyone else. The only thing that qualitatively defines a stressor is the response.

Once you understand that you can stop jamming round pegs in square holes and start making better decisions for yourself and those you coach.