The Neuroendocrine Response


The Neuroendocrine Response

by Matt Lloyd

In training as in life, there are many buzzwords that are frequently overused and often misunderstood.  One such popular buzzword is the neuroendocrine system, or NE for short.  It’s used and misunderstood for good reason.  Not only is it a powerful natural system that influences everything from your mood when you wake up in the morning to how fast you metabolize your dinner, but it is also, and perhaps more importantly, a system that can be optimized for more effective physical training and performance.  Since this system plays such a foundational role in one’s ability to improve as an athlete, a bit of education on the topic may get you further than an extra hour at the gym.  So, for those who are interested (which if you’re reading this blog you probably already are), here is the quick and dirty on what the NE system is and how to use it to your advantage. 

The neuroendocrine response as it pertains to physical activity is the relationship between the nervous system (from your brain to your peripheral nerves) and the endocrine system (hormones).  Hormones are what govern our body’s ability to grow and change, and can be conceptualized as the messengers between are brain/nervous system and tissues (e.g. muscles).  They regulate how the body responds and changes in response to any given stimulus like lifting a weight or climbing a route.  A few key hormones account for the majority of our body’s response to physical activity including testosterone, human growth hormone (HGH), insulin-like growth hormone (IGHF-1), insulin, glucagon, cortisol, and the catecholamines (i.e. adrenaline).  I’m willing to be you’ve heard of some of these before.

Greg Gassman, inventor and founder of CrossFit, is well aware of the vital role the NE response has in training.  He described it’s importance succinctly in a 2002 article published in The CrossFit Journal:

“‘Neuroendocrine adaptation’ is a change in the body that affects you either neurologically or hormonally.  Most important adaptations to exercise are in part or completely a result of a hormonal or neurological shift.  Current research, much of it done by Dr. William Kraemer, Penn State University, has shown which exercise protocols maximize neuroendocrine responses.  Earlier we faulted isolation movements as being ineffectual.  Now we can tell you that one of the critical elements missing from these movements is that they invoke essentially no neuroendocrine response. 

Among the hormonal responses vital to athletic development are substantial increases in testosterone, insulin-like growth factor, and human growth hormone.  Exercising with protocols known to elevate these hormones eerily mimics the hormonal changes sought in exogenous hormonal therapy (steroid use) with none of the deleterious effect.  Exercise regimens that induce a high neuroendocrine response produce champions!  Increased muscle mass and bone density are just two of many adaptive responses to exercises capable of producing a significant neuroendocrine response. 

It is impossible to overstate the importance of the neuroendocrine response to exercise protocols.  This is why it is one of the four defining themes of the CrossFit Program.  Heavy load weight training, short rest between sets, high heart rates, high intensity training, and short rest intervals, though not entirely distinct components, are all associated with a high neuroendocrine response.”   

— Greg Glassman 

So lets take a step back and quickly go over the basics of the neuroendocrine system.  It all starts in the pituitary and adrenal glands where hormones are manufactured.  When you train, you stimulate your nervous systems to tell your muscles to fire and lift the weight off the floor.  If the weight and reps are optimized, the resulting muscle damage triggers a cascade of signals which ultimately result in muscular hypertrophy (a.k.a. bigger muscles).  While the process begins during the workout, it continues afterward as your pituitary and adrenal glands release hormones that circulate throughout the body.  These hormones stimulate the necessary biochemical processes for muscle repair and growth, ultimately leading to the synthesis of new proteins, such as actin and myosin.  The synthesis of these proteins results in greater power at a cellular level.  Activating this process should be the goal each time we train, but given the delicate balance required to activate this system this goal is often not achieved.   

If you’re interested in building muscle the key then becomes to understand how the type of training we do does or does not trigger the body to activate this ideal neuroendocrine process.  The best training causes your muscle to become more responsive to the growth-stimulating hormones known as the anabolic hormones.  Less than ideal training may actually overly stress the body and muscles so that they become more responsive to the catabolic hormones, which stimulate muscle break down without the hypertrophic reaction.  Of course if the training is not intense enough you may not even activate any neuroendocrine response at all.  If you think of strict endurance athletes you will realize that they often have smaller builds.  This largely has to do with how the type of training they do (long and low intensity) does not elicit the ideal neuroendocrine response for muscle growth.  For climbers, CrossFitters, and nearly every athlete, it’s critical that we strike a balance between being light and efficient (your standard endurance build) and powerful.  As Tony Yoneiro once said:

If you’re not strong enough to do the move, there is nothing to endure.

heavy deadlift day at the gym

To elicit the most change in the body climbers must combine the large muscle group engagement (hams, glutes, quads) with the training of small but sport specific muscle groups (forearms).  If you don’t activate the larger muscle groups, you are unlikely to fully activate the neuroendocrine response.

A few take-home points to keep in mind when planning training for increased muscle and power are:

  • The magnitude of the hormonal response depends on the amount of tissue stimulated.   Use of more tissue (such as bigger muscle groups) leads to a greater hormonal response. 
  • The release of testosterone, one of the key anabolic-type hormones, is best stimulated by activation of large muscle group with heavy load resistance (85-95% 1RM) and short rest periods (30-60 seconds). 
  • Deadlifting, even in unskilled participants, is amongst the most effective moves at stimulating the synthesis and release of testosterone. 


For those of you who are climbers looking to maximize this ideal neuroendocrine response, focus on working large muscle groups before smaller ones.  This can easily be done by deadlifting before hangboarding or campusing.  The reasoning is that since there is not enough tissue in the smaller muscle groups of the forearms to elicit the desired hormonal response, you can fire up the anabolic hormones with pre-climbing deadlifts.  Before your next fingerboard session try completing a set of ten heavy deadlift singles, starting light and working to a near one-rep max (about 90% of your maximum effort) keeping rests between sets to less than a minute.  By the time you start your climbing exercises the anabolic hormones will already be circulating throughout your body priming whatever muscles you next engage to activate their repair and growth processes.  A second key to optimizing the NE response is timing.  High volume exercises of moderate to high intensity with shorter rest intervals have been shown to optimize the NE response.  For climbers I recommend accomplishing this by using high-intensity climbing activity (e.g. hard boulder problems) with limited rest intervals.  One of my favorite ways of accomplishing this is 4×4 training.  To do this pick four different boulder problems near your personal climbing limit (you should be able to complete the climbs on command but barely).  Climb all four problems in a row with no rest in-between (if you fall, just move on).  Once you’ve completed all four, rest for exactly one minute.  Repeat this cycle four times.

Lastly, in reading some comments and questions written in response to some of my other articles, I feel it’s important to say that this is not the only way to train.  Nor am I saying you should always train with the sole intention of activating the NE response.  I am merely sharing a well-researched tool so that you can add it to your arsenal when training for whatever your goals may be.  You may find this tool specifically helpful if those goals involve improvement in power and strength. 

For further reading and resources check out the following links:



Matt Lloyd is an owner of a climbing training and CrossFit gym, Mountain Strong Denver.  He has been climbing nearly two decades, has climbed 5.14, and prides himself on always being ready to rock and doing whatever it takes to succeed.

photos: Joshua Edric Photography (@joshuaedric) (

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