Strength Hacking with HRV

Jim Laird

Training has changed dramatically over the years. In the 6th-century BC, Milo of Croton would carry a calf on his shoulders every day until it became a full-sized bull. Unknowingly, Milo was in the process of discovering the principle of progressive overload. Simply put, the calf got bigger over time and Milo had to respond. As a result of his labor, Milo’s muscles adapted to the workload by getting bigger and stronger.

Thankfully we don’t have to resort to carrying around animals to get stronger in today’s world, but our bodies adapt to modern training in essentially the same way. What Milo discovered by carrying around a growing calf is still the most important underlying element of training programs, even today: progressive overload

Sadly, even though this concept was discovered hundreds of years ago, a lot of training programs are still in the dark ages when it comes to applying it effectively…

In Milo’s world, progressive overload was simple – the calf was getting heavier and heavier so it forced his body to adapt to heavier and heavier loads. He didn’t have to choose from a variety of animals of different weights; he didn’t have an endless variety of ways to lift the calf, etc.

To Milo, getting stronger was as simple as carrying a calf that got heavier and heavier. Today, figuring out exactly how much weight to lift, how often to lift it and how to put together an effective program to build the highest levels of strength is much more complicated.Milo of Croton

Now we have terms like volume, intensity, frequency, training load and periodization that make up the variables we use to design modern strength programs. The problem is that most people struggle with how exactly to put them all together and, as a result, many strength programs simply fail to deliver.

Fortunately, improving strength doesn’t have to be that hard once you understand how the process works and how modern technology can solve an age-old problem…

What is Strength?

In simplest terms, strength is the production of force by our working muscles. Open any physiology textbook today and you’ll find a detailed description of how our central nervous system delivers tiny electrical impulses that cause the millions of muscle fibers of our musculoskeletal system to contract and shorten.

This contraction creates muscular force which produces acceleration of our limbs and thus, we’re able to walk, run, jump throw, lift weights, etc.

While this simple way of looking at how muscles and strength work is correct, it’s also largely incomplete. What’s missing from this picture, and from countless books and articles, is that it completely ignores the other branch of our nervous system.

This branch is easily as important as the central nervous system that causes our muscles to fire…

Strength and the autonomic nervous system

Although it doesn’t get nearly as much attention as the central nervous system when it comes to training, the autonomic nervous system is really one of the keys to getting stronger. Even more, the simple reason most people ultimately fail to keep getting stronger lies not within the central nervous system, but rather within the inner workings of the autonomic system…

While the role of the central nervous system is primarily to drive our neuromuscular system and move us around, the autonomic nervous system handles just about everything else that’s required to keep us alive. It’s what governs things like energy production, protein synthesis, hormone production, blood pressure, digestion and absorption of nutrients, heart rate, etc.

Without a properly functioning central nervous system, we wouldn’t be able to move…but without the autonomic nervous system, we wouldn’t be able to live.

The autonomic nervous system performs the difficult task of keeping us alive through two distinct branches: the sympathetic and parasympathetic. Both branches are hugely important when it comes to developing strength – or any other area of fitness for that matter.

First, we can look at the sympathetic side of the equation. Most people have heard this described as the “fight-or-flight” system. Just as this catchphrase implies, the sympathetic system is responsible for preparing our body for fight or flight…or training…or performance…

To the body, fight, flight, training and performance are all one and the same: events that require massive increases in energy and force production. In order to make sure the body can produce the force it needs, the sympathetic nervous system causes a host of stress hormones like adrenaline, noradrenaline, cortisol and even testosterone to be released.

Together, the many different stress response hormones drive up heart rate, ramp up energy production and bind to the heart and muscle cells directly to dramatically crank up how much force the muscles can produce. Almost everyone has heard of amazing feats of strength like people lifting cars off of babies during emergencies thanks to the massive release of such hormones.

What most people don’t realize, however, is that it doesn’t take such an intense emergency to get adrenaline and other hormones cranked up to nearly the max. In fact, it happens each and every time we train.

Axle Deadlift

Without the sympathetic nervous system, we’d find ourselves crushed by the same weights we’re able to lift easily with the help of stress hormones.

In fact, this is exactly why so many people feel compelled to pound pre-workout drinks and stimulants. The whole reason they work is because they drive the sympathetic nervous system to cause the release of higher and higher levels of stress hormones.

While this may seem like a good thing on the surface, the problem comes in when we look at what happens when we stimulate the sympathetic nervous system too much for too long…

In order to see what I’m talking about, we have to look at the other side of the equation: the parasympathetic system. In contrast to the sympathetic system, the parasympathetic system’s job is not to increase energy and force production but rather to stimulate energy storage and tissue repair and growth.

After a workout, or any other stressor for that matter, your body has to start rebuilding glycogen levels, storing nutrients and working to increase protein synthesis. This is where the parasympathetic system steps in to minimize sympathetic activity so that the body can stay in an anabolic state (storing energy) rather than a catabolic one.

Together, these two branches are responsible for dramatically increasing how much force (strength) your muscles can produce, as well as how quickly they can recover so that they can do it again. Over time, this relationship and the process that results is what’s responsible for building bigger, stronger and more powerful muscles… at least when there’s a healthy autonomic balance…

Autonomic Overload

By now, it should be clear that the autonomic nervous system is just as essential to building strength as the central nervous system. The sympathetic branch is crucial to making sure your muscles can produce high levels of force and power, thus providing a strong enough stimulus to cause them to adapt. The parasympathetic system is what fosters that adaptation by creating the anabolic environment necessary for growth.

The problem, and the single biggest reason strength gains so often plateau, comes from when these two systems are not in the balance they need to be…

While almost everyone has heard the term “adrenal fatigue,” most people are unaware that it’s really just the end state of an autonomic imbalance. This imbalance ultimately results from the sympathetic system becoming overloaded to the point that the adrenal glands (where stress hormones are produced via sympathetic activation) start shutting down.

Even though most people simply stop training as hard and rest long before they develop true adrenal fatigue, the reality is that it doesn’t take full-blown adrenal fatigue to sabotage your training and strength gains.

In fact, sympathetic overload – where the body is under chronic stress to the point that the sympathetic system starts to lose its ability to increase force production – is incredibly common and the single biggest reason most people fail to achieve their strength goals…

Strength and Intensity

In order to see exactly what happens with sympathetic overload, we can look at a study where it was purposefully induced in a group of people performing 10 x 1RM on a squat machine every single day for two weeks…

Not surprisingly, this resulted in a 5% decrease in maximum strength and, even more, a whopping 36.3% decrease in power!

The most interesting fact is not that strength and power decreased, however, but rather the cause of that decrease. To examine this, the researchers measured changes in the number of receptors within muscles that bind stress hormones like adrenaline (known as Muscle β2-adrenergic receptors) and found that in just two weeks, the density of those receptors had decreased by a massive 37%!

In other words, a decrease in receptors led to fewer stress hormones binding to the muscles, severely reducing their ability to produce maximum strength and power.

Of course the receptor density did not decrease at all in the control group who only lifted heavy 2 times per week instead of every day…

Although you likely don’t do 10 x 1RM of squats every single day, chances are high that if you’re training hard to improve strength, you’re likely lifting heavy, with high intensity, at least 3-4 times per week.

When added on top of all the sympathetic stress that we encounter in our daily lives (think traffic, work, finances, family, etc.), the result is that a huge percentage of people end up failing to reach their strength goals simply because they’re in a state of chronic, low-grade sympathetic overload that prevents their muscles from producing as much force as they need to in order to keep getting bigger and stronger.

Even more, the stronger you get, the more likely this scenario actually becomes. This is because the more size strength you gain, the more stress it takes to continue to increase it. A beginner can seemingly double their strength in a few weeks or months, while someone that’s been lifting for years can spend months increasing a single lift by just 5- or 10 lbs, for example.

So getting stronger means you need higher levels of intensity, more volume and greater frequency in order to keep progressing. At the same time, however, the incredibly high levels of sympathetic activity that are a part of such training are inherently making you more likely to get into a state of sympathetic overload.

It’s almost as if your body is working against you to keep you from getting too strong; in fact, in many ways this is the case.

If you’ve ever been forced to take a break from heavy lifting for a week or two only to get back in the gym and find yourself noticeably stronger rather than weaker, it’s a surefire sign that you had been training in a constant state of overload.

Fortunately, we’re not in the dark ages of lifting calves to get stronger,and we have more technology in our phones than ancient strongmen like Milo could have ever imaged. Using this modern technology, specifically heart rate variability, we’re able to see this process happening in real-time and stop it before gets to the point that we start to get into sympathetic overload.

HRV Decrease

HRV and Strength

Although the use of HRV in training has increased dramatically in recent years, many people still seem to think of it as something for athletes interested more in conditioning than strength.

(If you’re unfamiliar with what HRV is or the basics of how it works, I’ve put together a 5 day video course that you can take for free by clicking here).

However, I’ve used my own BioForce HRV system with countless strength and power athletes ranging from Weightlifters to Powerlifters to Strongman athletes, along with just about everyone in between, with great success.

The reason HRV is such a powerful tool when it comes to increasing strength is because it actually shows you if your body is start to become sympathetically, or even parasympathetically, overloaded.

You don’t have to wait until you hit a strength plateau, or even worse, an injury, in order to figure out that your autonomic balance is off; you can see it in real-time and make the necessary changes to fix it.

The key to making HRV is in truly understanding exactly how to use it the right way to develop strength without letting yourself getting into sympathetic overload.

Free Strength Webinar

In order to give you the specifics of exactly how to use HRV to avoid sympathetic overload and see consistent and long-term gains in strength, I’ve put together a special free webinar. The live webinar session has already passed, but you can access the replay here.

Whether you’re already using BioForce HRV or not, this webinar replay will help you understand how to build more effective strength programs that deliver long-term results rather than plateaus…

In the webinar replay, I’ll walk you through the details of building strength while maintaining autonomic balance so that you don’t have to take a week or more off of the gym in order to get stronger. I’ll even give you a special HRV Weekly Strength Training Template that you can download and use in your own program.

Using the basic concept of progressive overload combined with the leverage and real-time feedback that HRV gives you, gaining strength can move past the days of hauling livestock uphill.

Click here to watch the replay or learn more about building strength using HRV in Part II of this article. I’ll give you case studies of real-world strength athletes and how they were able to get stronger by taking advantage of how the autonomic nervous system works rather than trying to fight against it


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