Wrong but Useful: Central/Peripheral Models

RCO_7051 Wrong but Useful: Central/Peripheral Models By Mike Tuchscherer, August 1, 2017 Go back and read articles from the early to mid 2000’s about powerlifting training.  Especially if the author is attempting to explain his thinking at a physiological level, you’re likely to come across the term “CNS” – or “Central Nervous System”.  And often it was in the context of “CNS Fatigue” or “CNS burnout”. Fast forward to the 2010-2013 timeframe and “CNS” more or less left the lexicon of popular programming articles.  And that’s not without it’s reasons.  As the idea of “CNS fatigue” proliferated, too many people took it to be an absolute or factual description of what was going on.  That left many of us, me included, speaking against the abuse of the concept.  Every bad training day is not because “your CNS is fried, bro”. But then the term seems to have left our lexicon entirely and with it, the useful concept it presents.  So, I want to re-introduce the concept here, along with a few quick points about how to make it useful. Your “CNS” is your Central Nervous System.  It is composed of your brain and spinal cord.  Everything outside of that is peripheral.  There are nerves, muscles, tendons, hormones, etc, etc… All of that is peripheral.  The nervous system component would be the Peripheral Nervous System (PNS).  All voluntary movement (such as lifting weights) starts with the CNS, passes through the PNS, and ends with a muscular action on the skeleton.JQE_3136 We’ve all done sessions with very heavy loads and small volumes.  The next day, we feel groggy, tired, unfocused, unmotivated, maybe even a bit sick.  This is what lifters are referring to when they say “CNS fatigue”.  Is there actual measurable fatigue in the brain/spinal cord?  I don’t know.  A cursory look shows me that there have been studies looking into central vs peripheral fatigue, but I’m not the guy to try to digest all of that.  But even if the term is wrong, it is still useful.  The point is that the term “CNS fatigue” (or perhaps more accurately “central fatigue”) is a useful collective term to describe those fatigue factors which are more central in nature.  Other fatigue indicators such as soreness and stiffness would be described as peripheral fatigue. We perceive differences in central fatigue vs peripheral fatigue.  Further, we can purposely induce these different phenomena separately.  Do you want high peripheral fatigue with low central fatigue?  Do high volumes of isolation work, possibly with slower eccentrics.  Do you want high central fatigue with low peripheral fatigue?  Do a session of heavy singles on the deadlift with a lot of psyching up.  And of course we can all think of workouts that can induce both. So if they are separate phenomena that come from different training parameters, what does it mean to us in a training/coaching environment?  It means to me that I can expect some workouts to cause more central fatigue effects and others to be more peripherally focused.  And since the workouts tend to drain the resources that they need to be successful, balancing the fatigue over time is important.  That’s to say, you don’t want to go into a session of heavy singles while experiencing high central fatigue.  You wouldn’t want high peripheral fatigue either, but in this case central fatigue will be more consequential than peripheral. Finally, I’d like to make the case for the cautious return of terms like “central fatigue”, “peripheral fatigue”, “CNS”, and so on to our training language.  It may not be 100% correct, but it does describe some of our experiences.  And we can become more accurate with the language as it develops.  But in the meantime, we should use the models we have with an awareness that they aren’t perfect. Making the “central/peripheral” concept useful…
    • High intensity, high skill movements, especially with psychological arousal are likely to result in more “central fatigue”.
    • Novel movements with high volume and eccentric load are more likely to result in “peripheral fatigue”.
    • No program, exercise, or protocol will be all central or all peripheral.
    • Your CNS is involved in every voluntary movement whether squats, bench press, running, jumping, etc.
    • Movements that have a higher CNS demand will likely result in more “central fatigue”.
    • Lifting heavy weights with technical proficiency requires greater CNS involvement than lifting lighter weights or lifting with less technical demand
    • Your body will recover from both central and peripheral fatigue on its own. There are things you can do to help, but for the most part it’s an automatic process.
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About the Author Mike Tuchscherer is the owner and head coach at RTS. He has been powerlifting since 2001 and since has traveled all over the world for competitions. In 2009, he was the first man from USA powerlifting to win a gold medal at the World Games – the highest possible achievement in powerlifting. He has coached over a dozen competitors at the world championships, a score of national champions, and multiple world record holders.