I’m going to be a bit ambitious here and try and break down the process that is training.  If you read my last post on stress, hopefully you realized the myriad of factors that might affect training and adaptation. What I want to try and potentially accomplish is to break that process down and look at each segment.  I’ve been giving up on these post for a few weeks.  It’s frustrated me because it’s something that’s hard to wrap your head around, but here’s my best go of it.

When I was in grad school, my advising professor, Jason Winchester,  had us write a paper where we took a certain type of training applied to a person and then take it down to what that would do down to the genetic level, and then back up to what kind of functional change would occur.  You can get incredibly complex doing this method, but the point of the exercise was to know that we don’t just go from lift weights to increase in muscle size.  There’s a process that the body goes through.

The basic gist of the process is summarized by the nifty chart below:


 The point is that it isn’t as simple as simply going to do a workout and then getting better.  Your body follows a process of adaptation.  So the stimulus is applied, homeostasis is disturbed.  When homeostasis is disturbed messengers get sent that trigger a signaling pathway.  If the pathway is activated enough or repeatedly, it will eventually translate into a genetic response that if that gets triggered enough results in a functional adaptation.

In this model what we need to know boils down to:

  1. The training adaptation we are looking for.
  2. What stimulus leads to that adaptation.
  3. What does the training stimulus trigger?
  4. What pathway is activated?
  5. What translate that pathway activation to actual response?
  6. How much “activation” is needed until we translate that to a functional adaptation?
  7. That’s a heck of a lot to know.  What’s the point right?  It’s overly complex…Well, let’s address that shortly.

So if we look at altitude training as an example: Stimulus- Training in a hypoxic environment Messenger- Reduced O2 levels in blood and muscle Signaling pathway: Hypoxia inducible factor (HIF-1) is activated.

(From my lit review) HIF-1 is a main oxygen homeostasis regulator in the body. Two subunits, HIF-1α and HIF-1β, make up the HIF-1 complex.  Under normal conditions, HIF-1β is present, but HIF-1α is constantly being degraded by the proteasome (Dery 2005).  When oxygen levels are lowered, the degradation of HIF-1α is inhibited, this stabilizes HIF-1α.  The stabilization allows for HIF-1α to bind to transcriptional co activators and enter the nucleus of the cell.  Here, HIF-1α binds to HIF-1β, forming an HIF-1 transcriptional complex (Marzo et al. 2008).  This HIF-1 complex then binds to the Hypoxia Response Element (HRE) on the EPO gene.  This in turn leads to EPO expression (Stockmann et al. 2006).

Genetic Response- EPO expression occurs. Eventually results in EPO production

EPO then needs to be transported to and bind with EPO receptors.  EPO receptors can be found on erythroid stem cells in bone marrow (Marzo et al. 2008). The binding to the receptor on the cell membrane results in a signaling cascade that results in the activation of the transcription factor STAT-5 and two enzymes, PI3K and MAPK.  These enter the nucleus and induce transcription of specific genes that result in the inhibition of apoptosis, programmed cell destruction (Marzo et al. 2008, Jelkmann 2004).  The end result is that this prevention of destruction of developing RBC results in an increase in RBC.

Functional Adaptation- Increase in Red Blood Cell mass which results in increased endurance

Now before you jump on the “too complicated” bandwagon, let’s step back for a second.  I’m going to make the notion that the above chart, and understanding its implications is paramount for success.  BUT, I also think you need to be able to simplify it to be useable. So let’s step back and go through the process of dissecting the above chart.

Starting simple:

When I was talking to my college team at Houston the other day I basically summarized training as a process of stimulus and adaptation.  That’s it.  Training can essentially be broken down into those two parts.  You apply a stimulus and your body adapts.  How your body adapts depends on the stimulus applied.  So we can take that chart above, take out the middle three and you get:

Stimulus-> Adaptation

What you’ve essentially done is take out the mess, and makesome assumptions.

  1. We assume that the person follows a normal route
    of adaptation.
  2. We assume that the recovery is correct and long
    term adaptation takes place

What we need to know:

  1. The training adaptation we are looking for.
  2. What stimulus leads to that adaptation.
  3. How much is enough?

Essentially our goal is to figure out what we are trying to accomplish and then what it takes to accomplish that goal at this specific time with that person.  So it’s rather simple.

As an example, let’s say my goal is to increase aerobic support for a 5k runner.  So I might want to increase his lactate threshold.  That’s the goal.  So let’s take Tommy Schmitz as an example and say his last tempo run was 4miles averaging just below 5:00.  Now, I might give him 5miles going 5:10,5:05,5:00,4:55,4:50.

Why?  I’ve increased the distance a bit, made it progressive so he starts just slower than threshold and ends maybe just faster.  It’s a new stimulus.  If everything goes well, he’ll increase his endurance in that specific fashion.

Simple enough.  Know what you are trying to do and what it takes to accomplish that goal.  This is the basis of coaching.  Apply a progressive stimulus to get a desired adaptation.  A heck of a lot easier than knowing what signaling pathway results in some gene activation that might do something nice.

Assumptions and external factors:

So far we’ve stuck with dealing with the idea that all that matters is the training stimulus.  You apply that correctly and this cascade of events occurs. You make the assumption that X translates to Y. We’ll call this the set it and forget it model.  But…what really happens is that along that way from stimulus to adaptation a crap load of stuff needs to take place.  So now what we look at now is “interference and synergist” for the stimulus and adaptation.

Basically, what things help or hurt the process.  They can help or hurt at any level along the way.  And this is why the complex model is needed.  The complex model gives the basis for understanding why external factors impact adaptation.  When we use the simple model we are saying do X workout, get Y result.  When we look at the complex model, we say oh crap, lots of stuff can go wrong.  If you know the basic underlying process for the complex model it allows for better creation of training and less risk of error.

Let’s first look at some of the factors that can influence the process and (a few) examples.

  1. Arousal and emotional state- Since my last post was about stress we will start here. First stress affects adaptation.  I’ve covered it.  Secondly, arousal state before and during a workout can affect the adaptation.  How?  Get our adrenaline going and it changes the degree of stimulus a workout is giving.  Get lots of adrenaline and the lactate response changes, the CNS activation of muscle changes, and so on.
  2.      Nutrition- Nutrition impacts everything.
    1. If we take in carbs before a run, it changes the fuel utilization of that run.
    2. Take carbs in the middle of a long run we’ve just switched the stimulus from the goal of running the body low on fuel so it adapts, to now running long at a quicker pace while maintaining fuel levels.
    3. Take protein and/or carbs after a workout and we’ve just changed the recovery process and protein synthesis within the workout.  Don’t take it and recovery differs.
    4. Building blocks for adaptation- If you don’t have the iron or protein or whatever necessary ingredient is needed, full adaptation won’t take place.
  3. Environmental factors
    1. Working out in a hot environment? Muscle recruitment from the very start is changed.  The limiter changes now too.
    2. Doing hills? Muscle recruitment changes.  A strength component is added and a decrease in reliance on elasticity happens.
    3. Working out on soft grass?  Bye bye elastic component of your stride and
      hello reliance on more “work” instead of “free energy”. Muscle tension is changed as well.  Thus now biomechanics change and your neural adaptation to running on grass changes.
  4. Recovery
    1. Nutrition recovery changes adaptations.
    2. If you take some NSAIDS
    3. How much you sleep effects the cementing of the learning process (i.e. reinforce any biomechanical/skill changes), the hormonal state (testosterone, HGH, etc.), and protein synthesis.

This is just a smattering of examples and there are countless others.  It’s not meant to overwhelm but rather to give you a scope of the issue.

Now, where can these things impact the process?

  1. Stimulus application- Stress, anxiety, arousal state, CNS activation, nutrition- All these things can impact the stimulus of the workout.  They can either increase or dampen it down.
  2. Conflicting pathways- There’s an interplay between many signaling pathways.  So the classic one is between AMPK and mTOR. If one is activated, it impacts the other.  Thus why if you are trying to get muscle hypertrophy and you go for an aerobic run right after lifting heavy weights, you just dampened down the training effect of the heavy weights. Why? Pathways interact.
  3. Not enough adaptation reserve- stress, recovery, sleep- We only have so much room for adaptation.  If outside stress decreases your adaptation reserve, guess what, less adaptation to your workout.
  4. Translating to functional adaptation- nutrition, protein, building blocks-  You have to have the building blocks to translate to permanent adaptation.  If protein synthesis isn’t there, you aren’t going to rebuild muscle.  If iron is too low, you aren’t going to make new Red Blood Cells.

So how much does the little stuff matter? Some examples:

  1. Caffeine- Central Nervous System stimulant- changes motor recruitment a little.  Manipulates central governor/pain perception.  So now you are “amped” for every workout.  Now you are going above and beyond in every workout.  What happens?
    There’s a mismatch between the feedback your body is giving and the actual stress.  You’re able to go to another level and your body doesn’t think it’s that hard because of the artificial enhancement.  Do this repeatedly enough and it might hurt you a bit or you become habituated to the artificial levels.  That’s why I say save the caffeine for when you need it.
  2. Antioxidants/NSAIDS/etc.- Impacts training stimulus/messenger and adaptation.  If the messenger is increase in free radicals, then would taking something that eliminates that stimulus for adaptation be good?  You’ve dampened down the stimulus.
  3. Mouthwash- This is one of my favorite examples of why little stuff matters.  Beet Root juice is the new in vogue performance supplement of choice.  It increases performance/endurance and since all you have to do is drink a lot juice and the only side effect is your pee might be get a little.  Well, take some mouthwash before/after that beetroot juice and what happens?  The beet root juice doesn’t work because the mouthwash gets rid of key bacteria needed for the process to work

How do you know what helps or hurts the adaptation process?

  1. Research- read journals or my blog
  2. Reason it out- Use the chart above and if you know the process you can take an educated guess if something might dampen down a stimulus or retard adaptation.

So what?


Now that I’ve overcomplicated everything, what’s the point?  The goal of the coach, athlete, scientist, whomever, is to know when to go complex and when to go simple.  The human body is incredibly complex.  I spend waaaayy too much time looking into all this science junk because it intrigues me and I still get lost. So my point in trying to dissect the training/adaptation process in two contrasting models was to reinforce the idea that you have to know when to go complex and when to go simple.  You have to have the ability to do both and more importantly know when.

In the world of coaching, I try and figure out the complex.  I use that signaling pathway junk whenever I’m asking what I think a new type of workout will do.  Once I figure that out, and I think I have a good handle on the workout, then it shifts to the simple model.  I’m always trying to simplify, but you have to understand the big complex junk before you can get to that step.

Use the models, come up with your own, be creative.  The point is to understand what happens along the route of workout to improved fitness.

In simple terms this should guide your program.  You need to know what you’re trying to accomplish and how to get there.  That is the key to coaching.

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Stimulus and Adaptation- A complex and simple look at the training process
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10 thoughts on “Stimulus and Adaptation- A complex and simple look at the training process

  • November 22, 2012 at 4:31 pm

    I'm curious, what have you found are the best ways of gauging the the adaptive response?

    DOMS are clearly a sign of response by the body but does this always indicate positive adaptations?

    Does absence of DOMS indicate a lack of adaptations?

    • December 11, 2015 at 5:33 am

      absence of DOMS does not indicate a lack of adaptation. Metabolic adaptations can certainly take place without DOMS and increase lactate threshold, oxygen utilization, etc.

  • November 22, 2012 at 9:45 pm

    Thanks for the post, a great read as always.

    When we talk about stimulus and adaption one thing I would like to know is; how to know where the athlete is on the adaptation curve? Would this be a case of testing throughout the stimulus input and plotting the adaption curve or could you simply take times from a session and plot a adaption curve? Introducing new stimulus when session times improvement levels off? Would there be a danger of doing this and looking for consistent improvement or could this actually be a good thing as it would indicate when to change stimulus/session?

  • November 23, 2012 at 6:22 pm

    I have been drinking coffee before every exercise for some months now. I have considered many factors for my constantly overtraining and hurting legs, but not the coffee. Won't drink coffee for a while now. Thanks for mentioning! ;D

  • November 26, 2012 at 8:41 pm

    I've regularly checked in with this blog ever since I found it on a lets run thread, and dearly appreciate it. Things that I would think would be useful, and enhance understanding of this subject are generalized examples of what kind of stimulus triggers what kind of adaptations, and what sort of diagnostic tests can we perform to know what adaptations we need to work on. I know you are not a big fan of the physiological model (i.e. Jack Daniels), so what do you propose as an alternative? The most useful training manual I have found in terms of diagnosis is HADD (although the part about providing different stimuli is severely lacking in his little hand out. After 10+ years of running and reading as much as I can, I still feel like I'm flying blind when trying to improve my own shortfalls, because I'm still not sure what stimuli provides what responses, and what my real weaknesses are. From what I've read, you have a longer run (20-35% of your weekly mileage), you make another 20% of your weekly mileage some form of intensity (AT or Intervals), and the rest fills in the spaces. The 20% intensity is the hard one for me. When do I run HR quarters, when do I run Mile Repeats, When do I run 1000s, 800s, etc… And how intense should I make them? That's kind of the beauty of Jack Daniels (although I also don't buy his quality junk concept), you know where you are, and you know what you need to do next.

  • November 27, 2012 at 5:13 am

    Hey Steve,

    How long would you say the "average" runner adapts to a stimulus? I've read books and articles that state it takes four to six weeks. Would you agree?

  • December 1, 2012 at 8:31 am

    Here are my thoughts:

    If you accept the functional path then to improve your 5k performance the most functional training is at 5k pace, with the paces either side been next 3k pace and 10k pace (however in practice you need to consider the training cycle).

    So lets take an example of measuring performance. An athlete starts a block of 5k pace sessions, such as:

    week 1: 6x1000m off 2mins. average time 3 minutes per rep. average max heart rate 165, average min heart rate for the recovery 125. Focus is on improving 5k performance.

    First testing method) Benchmark this session once every 3 weeks, take these readings and plot a response in terms of heart rate (min/max) and rep time. When the performances starts leveling off change the session focus.

    Second testing method) Run this style of session weekly and once every 4 weeks perform a 6 minute time trial on the track and again plot responses such as vVO2MAX = distance / time and heart rate (min/max). Moving on when results level off.

    Third testing method) Race once every 4 weeks.

    Forth testing method) Take times and feedback from each session and plot the responses trying to normalise for session differences (comparing 6x1k to 4×1500 can be difficult, what’s better 6x1k /2min (3:01avg rep) vs 4×1500 /3min (4:35avg rep))

    This type of testing should work although if you are self coached this can make for quite mentally taxing training as you know you are measuring.Or if you have a good coach he/she will use all of the above, without the athlete having to even consider it.

    Anyone else have any thoughts to progress this?

  • December 4, 2012 at 9:15 am

    I like this methodology and your approach to the stimulus / adaptation cycle. It helps that you have experience and this acts as a "filter" to all the information that is out there.
    I think that younger, less experienced coaches can get lost in the amount of information that is available. That is why reading what other coaches have done may be a good start.

  • September 29, 2013 at 2:48 am

    Great blog post. I really enjoy reading your blog and your interpretations of the currently available science.

  • October 10, 2013 at 8:17 pm

    Thanks for the post, a great read as always.
    When we talk about inducement and adaption one thing I would like to distinguish is; how to know where the athlete is on the adaptation curve? Would this be a case of testing throughout the inducement input and plotting the adaption curve or could you simply take times from a session and plot a adaption curve? Presenting new stimulus when session time’s improvement levels off? Would there be a danger of doing this and looking for consistent development or could this really be a good thing as it would designate when to change stimulus/session?24 hour turnaround


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