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Falsehoods of Fitness

Falsehoods of Fitness: CNS Fatigue Limits Training Frequency (Episode 10)

Dr. John Jaquish discusses research on CNS fatigue as a result of exercise, and whether or not one needs to take extra time recovering because of nervous system fatigue.

Full Transcript

Welcome to another episode of Falsehoods of Fitness.

Today we're gonna be talking about central nervous system fatigue, or commonly referred to as CNS fatigue.

So, this was made popular, the term was made popular, boy, I think in like the late 80s, early 90s by Arthur Jones. And Arthur Jones is the founder of Nautilis, and then it was kinda kept popular by a body builder named Mike Mentzer. And so what they were talking about was how there's recovery of muscular tissue. You know I can train my biceps and how long does the actual tissue take to recover.

But, then there's the neurology associated with activating that muscle and there is such a thing as the fatigue of the central nervous system in respect to when it wants to recruit as much tissue as, let's say, before an exercise session.

The central nervous system does fatigue after a certain amount of time

So, because effort is very dependent but maximum effort, the idea was that there was a certain amount of time the central nervous system doesn't want to engage a certain amount of muscle, and it turns out that's true.

But in 2016, a lot of research came out that shows that actually cardiovascular exercise has a longer window of time that it takes to reactivate to the same degree some of these tissues called excitability. And it turns out that it wasn't what people thought it was at all. It wasn't days or weeks that it takes.

It's really, from a cardiovascular perspective, it's like thirty minutes.

So, and if you think logically, that makes sense. Like, if somebody does heavy resistance exercise, let's say they do heavy squats or even to a more exhausting degree, like X3 squats, then they couldn't activate musculature if they had to run up a flight of stairs or something like that, they couldn't. Or maybe they would lose their balance because they can't fire enough musculature.

So we know soreness and the inability to engage muscle are two very different things. So, do not confuse those two – different.

So, when we look at this and Thomas in 2015, 2016, two different studies, really did a lot to determine that this cardiovascular exercise was more so the acute changes in the inability to engage, or the excitability of musculature.

But, probably more to the point, specifically when looking at resistance training – single-session, heavy-strength training is what it was described by Latella in 2016. It looks at what it takes to go to central nervous system fatigue, and then how long it takes to recover from it.

So, this is just something I pulled out of the study. And you can see here's baseline and this is after somebody exercises. You can see the excitability goes down, so baseline is like right where central nervous system fatigue is. So, right after the exercise, you get about a 10 minute window where you're not able to really engage as much; 20 minute window, you're right back to baseline; 30 minutes, you can activate, you know, just as much.

Above, or at least you're above the baseline and then it shows an individual right about 48 hours later, there's another exercise session, and they can engage to a much higher degree. So, central nervous system fatigue is a thing but, it's not a thing that anybody really needs to worry about because the actual tissue, muscle protein synthesis, is really the bigger issue. And we have a very good understanding of that now, with muscle biopsy studies. Which is why we know 36 hours is really the window. And after 36 hours, you can train again now.

With the X3 protocol, we'd wait 48 hours and that's about it.

Now, when it comes to muscle damage, which I'll do another Falsehoods of Fitness on muscle damage, and the idea that you create micro tears, and micro tears have to do with growth. That is not true, either. There's more micro tears in musculature when you run a marathon versus your weight training session. And guys who run marathons, they're not growing any muscle. So, it's got nothing to do with it, and that will probably be the next Falsehoods of Fitness.

Hope that was helpful and you can find me or people who can answer your questions on the X3 Bar Users Group on Facebook. Over 10,000 users there, who a lot of which can answer some great questions. There's also the X3 Bar Facebook page and the Dr. John Jaquish page on Facebook. And then on Instagram, I'm @drjaquish. Hope that helps. See you soon.