Understanding CNS Fatigue

30 Jun

Intense training places a tremendous amount of stress on our central nervous system. To give you an idea, it takes the CNS up to 5-6 times longer than muscles to recover from an intense training session. This means that while your legs might feel fresh 3-4 days after a max-effort squat, it could take your CNS up to a month to fully recover!

(Notice I said “intense” training. Not everything you do in the gym takes the same toll on your nervous system. Fast, explosive movements such as Olympic lifts, dynamic training, and plyometrics place the highest stress on the CNS. Heavy free weight lifts like squats and presses also place a high level of stress on the CNS. Isolated movements and anything done on a machine are not CNS intensive.)

So why should this be important to us? Your CNS is responsible for recruiting motor units in muscles, controlling their firing rate, and coordinating any muscle activity. If your nervous system is fried, performance is going to suffer severely.

Think of your body as a car and your CNS as the battery. As the battery starts losing power, all those flashing lights and computer systems that allow the car to run start functioning more and more poorly until one day the car just won’t start. If you push your body in the same manner without ever giving your battery (or CNS) a chance to recharge you will eventually hit the same wall.

You aren't the Energizer Bunny. Take the time to recharge your batteries!

The key to keeping your nervous system up to speed and avoiding overtraining lies in autoregulation. Autoregulation simply means understanding what physiological state your body is in on a given day, and actually LISTENING to this message. It took me years to finally understand that pushing through multiple shitty workouts in a row does not make you any tougher or more of a bad ass. All you are doing is setting yourself back mentally and physically. In training, it is crucially important to know when your body needs to cut a set short, or even cut out the entire training session for the day.

As it stands today, we really know very little about how our nervous system works and how we can maximize its efficiency. However, there are several biomarkers that we are aware of that can serve as indicators of how fatigued our CNS is at a given time:

1)      Dan John wrote about using a dot test in which he would take a pencil and make as many dots on a piece of paper as possible in a period of time. Thanks to people who develop online games for websites with names like http://www.i’mboredasshitanddon’tdoanythingatwork.com we have tools like “the space bar game” http://www.zimm-co.com/PressTheSpaceBar/pressthespacebar2000.html which records our results for us. Thanks, nerds. Test it out for a few days after your body has been fully rested to find your average score. Then, retest yourself upon waking up in the morning every so often. If your score drops anywhere from 10-15% your CNS may be getting fatigued.

2)      Recording your heart rate upon first waking up in the morning is another great way to gauge the state of your CNS. Count how many times your heart beats in 1 minute, and always test yourself in the same position. A jump in your resting heart rate is a sign of overtraining.

3)      Jump tests like the vertical or broad jump also work as indicators. Not everyone has the equipment needed to test their vertical on a regular basis, so the broad jump may be a better option. As with any of the other methods, test yourself for several days to establish a baseline average. Repeat this test every day before you train and keep an eye out for any glaring drops in your numbers. (This method may not be as reliable due to the fact that a drop in jump distance could be attributed to muscular fatigue as well as CNS fatigue)

4)      Lastly, something I picked up at the Amped seminar this past weekend is that if the palms of your hands are extremely red or if the temperature of the weights always feels cold, it might be time to cut your training short that day. (I have no idea what the mechanism for this is, but Smitty said it is dead on accurate almost all the time)

Train hard, train smart.


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