Neuromuscular Fatigue in Ultrarunning with Roger Enoka, PhD | Koopcast Episode 62

trail and ultra runners what is going on what's happening welcome to another episode of the KoopCast as always i'm your host coach Jason Koop and on this episode of the podcast we have a real treat for you on the podcast today we have one of my old undergraduate professors i'm just realizing that that phrasing makes us seem far too old than we actually are we have one of my former undergraduate professors and more importantly one of the foremost thought leaders in neuromechanics today it's roger anoka PhD at the university of colorado boulder roger's academic career spans five decades as a professor and a researcher and during his tenure he has served as the president of the american society of biomechanics he's been part of the research advisory panel for the american physical therapy association and has received numerous and prestigious awards such as the mui bridge and boreali awards from the international society of biomechanics as well as the basmagean award from the international society of electrophysics and kinesiology and wow that's a mouthful and if those awards and accolades are not enough roger is also a fantastic professor a keen communicator and always looking at better ways of explaining neurophysiology and neuromechanics to students and lay audiences alike and this is no easy task as those areas are complicated subjects which blends the worlds of

neurology biomechanics physiology and at times electrical engineering to explain human movement his area of expertise is practical for ultra runners as we are beginning to appreciate more and more that endurance performance is not just about oxygen consumption bioenergetics and running economy there's a complicated set of sensors and feedback mechanisms that are also at play in fact one position we explore on the podcast is that fatigue per se is not the cause of decreases in performance rather it's how we sense and perceive that fatigue that is ultimately what causes us to slow down roger literally wrote the book and the textbook on neuromechanics in his book the neuromechanics of human movement which is about to be released in its sixth edition this is a book that i have revered so much that i've held on to for the last 15 years as a reference for my coaching practice and we pick up the conversation right there here we go without any further ado here's my conversation with roger anoka before we get into this proper i do have a present for you and that's this yes i've kept this this book neuromechanics of human movement it's the third edition right for 15 years i don't remember what the original publication date of it is i take it you still use this in your course correct uh yeah we

there's a couple editions after that so i'm actually thinking about writing a sixth edition oh my gosh sixth edition how hard is it to revise when you go through that because i think i remember when this came out it was like it was like the newest edition you had just you just revised it and you kind of took the class through what was actually revised so it is a big job to revise a textbook work the way i do it it's a big job but and the reason i do it is that you as new knowledge is accumulated and especially as students ask me questions when i'm teaching that i it's i'm it's clear i'm not understanding explaining it clearly enough then i i you know i get ideas about how to present it more clearly yeah but you even after all these years uh it's changes are still necessary right right it's that whole learn one do one teach one right and until you teach it it forces you to become a better master at it because you have to explain things to whatever level you're teaching that that's why i like teaching so much is that uh because if if you can't teach it well then you probably don't understand it yeah 100 we find that with our coaches too when we take them through the training process is we take that learn one do one teach one approach to eventually once they've been coaching for five or seven years they're the ones training the new coaches and it gives them a completely different perspective on the whole process

we're going to do some teaching during this during this podcast a little bit because not everybody has not everybody has taken one of your courses nor is a uh nor is a professor nor has any sort of neuromechanics type of background and so we're initially going to have to like level set things and the the way that i want to do this is to just basically describe what happens during a really simple task and this is kind of harking back to my days in your class where we used a very similar analogy we're going to use a bicep curl and walk through what is going on neuromechanically as somebody performs a bicep curl as they add weight as they start to do it eccentrically and use that as a little bit of a platform for understanding first and then get into the the the meat and potatoes what everybody cares about is how to actually train for these things because in the trail and ultra running world we're really concerned about neuromuscular fatigue because everybody has experienced running down a big you know mountain or something like that or doing a really hilly course and just having less and less motor control as that event kind of goes on they start to stumble over rocks their stride becomes super inefficient and on and on and on and on and i think that that it's becoming more and more clear that there are some big neuromuscular consequences

to that type of long duration lots of eccentric load type of uh type of activity but we're going to start super simple with the bicep curl so the the way i want to do this is let's just describe what is happening from a neuromuscular point of view as i perform this exercise so i'm staring at a 20 pound dumbbell on the floor and i want to pick it up and that's all i want to do i just want to grab the weight and pick it up what is going on neuromuscularly as i decide to do that task okay so if you've already made a decision that you want to pick this weight up then what the brain has to do is translate that into some uh plan of action so it develops what we call a motor command which is just an activation signal that it sends down to the spinal cord and uh despite and this uh command signal will go to the nerve cells that are going to perform the action or control the action and these nerve cells are called motor neurons and they live in the spinal cord and each one of these motor neurons connects to a few hundred muscle fibers um so the connection between one nerve cell which is called a neuron and the muscle fibers that is the motor unit so everything we do ranging from picking up a dumbbell to running is all controlled by manipulating the amount of motor unit activity so if you're picking

up this weight then the signal coming from the brain to the spinal cord has to activate enough of these motor units that the force is sufficient for you to lift the weight up okay so there's our simple task i'm gonna lift the weight up we're gonna gradually increase the complexity i guess and the effort of this task and eventually bring it into reality of actually running so let's change the scenario and say instead of 20 pounds that i want to lift up let's say i'm gonna i want to lift up 40 pounds what is different from a neuromuscular perspective between this 20 pound effort and then this 40 pound effort okay so if i can just go back to the idea of the motor unit for a minute and say that uh when one motor unit is activated um it produces a force i mean it activates the muscle fibers and they generate a force how much force that motor unit produces depends on how many muscle fibers it connects to and also the the intensity of the activation signal so the intensity of the activation signal means the frequency at which these electrical impulses are sent to the muscle so there are two components that influence um the force that are the muscle generates that is the number of motor units that are activated and how much each of

them is activated so if you want to pick up a heavier load then you have to generate more motor unit activity which will mean activating more motor units and increasing the frequency of this these electrical impulses perfect so now we have this pathway to where okay i want to do i'm going to do this simple easy task to i'm going to do something a little bit harder let's now talk about what starts to change if i want to take that 40 pound weight and i want to continue to lift it i'm going to do it 10 times 20 times and eventually to the point where i can't lift it anymore what's going on at that stage of the game so uh before we before we get to that question i think there's one other thing i need to explain sure and so when you're doing this uh biceps curl type of exercise uh as you as you realize for sure there are two parts to it one is the lifting of the weight and the other is the lowering of the weight and what the nervous system is doing during those two parts is quite different so the lifting is pretty easy it just means you have to the brain has to activate enough motor units to get forced to lift it but to lower it now what the brain has to do is carefully reduce the amount of motor unit activity so that it's less than the force of

the weight you're lifting so we call this a lengthening contraction many people call it an eccentric contraction but i make a distinction between eccentric contractions and lengthening contractions lengthening contractions uh imply a very precise control by the nervous system whereas eccentric contractions all you're doing is resisting some force that's acting against your muscle if you do multiple repetition repetitions of this biceps curl uh you can do a certain number before you reach what we might call task failure in other words you can't lift it anymore so then the issue becomes well what's caused task failure so fundamentally um this is the domain of i've quote fatigue and so physiologists have been thinking about this for 125 years and saying that when you reach task failure is it because of problems that have occurred in the muscle or is it because of problems that have occurred in the nervous system and the relative influence of the muscle versus the nervous system depends on the activity that you're performing so if you do something a very prolonged activity like run a marathon and you feel like your performance is declining most likely the major culprit is changes that are taking place in the nervous system and not in the muscle i mean there's very clear

scientific evidence that um the adjustments in the nervous system are much more critical during long duration activities so let let's kind of get back to this concept you mentioned of an eccentric contraction and i agree with you this term kind of gets thrown around really haphazardly in the in in the coaching the training the running world weightlifting world and i'm sure you've seen it in fact um i remember in your in your class we had this long discussion of what we should call that should we call it an eccentric contraction should we call it an eccentric which always seemed like an oxymoron right eccentric contraction or an eccentric lengthening or an eccentric activation of the motor unit so anyway that's just more vocabulary but one of the um one of the critical points with this type of active lengthening of the muscle fiber is that it can produce more force in that direction versus versus how it can concentrically why don't we go over that phenomenon a little bit and then i think there are implications for how how that produces fatigue in a running situation it's true that when you perform an experiment on a muscle that's been removed from some experimental model so an isolated muscle preparation and you connect the muscle to a motor that can either shorten the muscle or lengthen the muscle

that the force that you get the maximum force is greater during a lengthening contraction than a shortening contraction it's very clear but uh that experiment model doesn't easily translate to performance in humans because it assumes that the nervous system can maximally activate the muscle during both shortening and lengthening and it's difficult it's very difficult for the nervous system to do that during lengthening contractions what's more relevant is that the same force can be achieved with fewer motor units during a lengthening contraction versus a shortening contractions so for human performance that's the critical issue not that the peak force is different but that the number of motor units engaged in the activity are fewer during lengthening contractions let's so let's talk about adaptation a little bit because as endurance athletes we tend to almost pigeonhole ourselves into this cardiovascular silo of adaptation we look at you know things like mitochondrial biogenesis and we want to increase red cell mass and all of these things that are inherently linked to the cardiovascular system we have to we have to look at that because they're cardiovascular sports but it turns out that there are also neuromuscular adaptations to exercise that we're always trying to to to tease out when a runner first starts to undertake an exercise program

just take somebody off the couch they go out and they go out and run one of the first things that they're going to experience is is it feels awkward the motion feels awkward and they start to develop a little bit of soreness right out of right out of the gate what is going on in the in that situation from a neuromuscular perspective and how does that eventually become more and more trainable in other words how does the human ultimately adapt to that form of locomotion so that's that's not a simple question and to to give you a reasonable answer i need to backtrack a bit and talk a little bit about the activation signals that go toward and from muscles so if we take a nerve that's going to a muscle and we cut the nerve and we look inside the nerve we can see a whole bunch of nerve fibers these are the fibers that send the signals out to the muscle and send the signals from the muscle back to the nervous system we have typically assumed that in the nerve that 50 percent of the large fibers are sending that activation signal to the muscle and 50 percent are sending information from the muscle back into the nervous system so this is information about sensations so in a study in 2011 we found out that that's not a correct assumption that actually 90 percent of the nerve fibers in the nerve are providing information

about sensations and not uh their muscle contraction so why is that important that's important because it tells us about about how much the nervous system relies on sensory information so we go back to this all right this issue about adaptation that you raised so when a person begins a new activity such as running and things uh feel a little bit weird and there's some soreness and so on um quite the fundamental question from a physiology point of view is is this due to change again is this due to changes that are taking place in the muscle or does it have something to do within the nervous system so the answer is not clear so is the soreness due to damage that's occurring in the muscle you can clearly demonstrate that you take a muscle and you isolate it and you impose these loads on it you can easily damage the muscle but we don't do that when we are performing activities uh without you know some external mode of driving things instead uh our activities are controlled by sensory information so there's very clear evidence that uh this muscle soreness has a very strong component based on sensations that a person is is feeling that are not necessarily related to muscle damage per se

so it's difficult to tease this out um so what you're saying is from a soreness component yes it's not necessarily coupled with the amount of muscular damage which you'll hear that time and time again from coaches and athletes and physiologists oh i have a lot of muscle damage and i feel sore from it right so that's exactly the point i'm trying to make there's there's no direct association by how between how much damage has occurred in the tissues involved in the action versus the sensations associated with that so i i can give you another example if you if you want me to do that so let's think about stretching for a moment okay so this is something that runners do um and uh we know that if we do stretching exercises one of the goals of a stretching exercise is to improve flexibility and what that means anatomically is to increase the range of motion about a joint so a person does stretching exercises either a single session or several weeks of sessions and their flexibility increases so again the basic question is this due to changes in the mechanical properties of the tissues muscle and connective tissue or is it due to change that take place in the nervous system so scientists who study these kinds of questions uh most of us agree that when a person's

flexibility increases it's because they have learned to tolerate greater levels of discomfort as opposed to being any changes in the mechanical properties so again it's adaptations within the nervous system and what's going on inside a person's brain in their capacity to interpret those signals so i mean it's and and i suspect that this muscle soreness issue there's a lot there's a big component that's related to sensation and not necessarily structural damage in the tissues so in a perfect world if we could kind of like wave our magic wand and create better performance what you would be doing is focusing on interventions that block that sensation from coming back up the chain of events so that you actually recognize it i mean is that a plausible a plausible a plausible fictitious scenario yeah so it's not necessarily blocking it but learning how to deal with it is probably a more important analogy i would say so this whole concept of like feet like being able to feel out and actually like recognize these sensations and tolerate them is actually a really practical point from a neuromuscular point of view absolutely i think that's absolutely important point so let's take let's take this classic trail running scenario that we see that i see a lot as a coach and as an as an athlete and i want to get your opinion on it

i kind of mentioned from the onset that one of the things that trail runners have to contend with is this this this the long duration of exercise and the long duration of descending which is which has a big eccentric component to it what we think or what we thought before everybody just listened to this is that that had a lot of muscular breakdown and we had to like combat that muscular breakdown somehow but what that has produced are all of these different training interventions in order to combat this type of fatigue and the two that rise to the to the top in terms of the way that i observe them that i want to get your opinion on are strength training and running hard downhill so just literally running all the downhills as hard as you can to produce some type of adaptation or in order to tolerate that in a race situation based on what you know that that we're combating a lot of neuro muscular fatigue in that situation are those plausible are those plausible training interventions and how might they actually work for an athlete that is trying to get better at tolerating downhills so i i think as far as i know the principle of specificity is probably most appropriate i i think running downhill in which especially the thigh muscles and to some extent the calf muscles are doing length and contractions

would be the most appropriate approach to try to reduce the the amount of soreness that a person experiences i wouldn't call this fatigue so this is another issue that has been a big deal in the physiology literature about you know what what is fatigue and you can pick up many different papers and get all kinds of definitions but in recent years there's been a bit of a change in the approach in the physiology world as to what we mean by fatigue so when you were just asking me the question about fatigue i think what you what you are sharing with me is a classic physiologist point of view of fatigue and and that's been changing in recent years and it's largely being driven by clinicians who work with patients who report fatigue and so clinical people like neurologists for example uh they use fatigue as uh as a symptom so it's just like pain so if a person has pain you can't measure it the only way you can measure it is you ask a person are you in pain and you give them a scale and they say yes i'm in pain so now we're beginning to do the same thing with fatigue so you say to a runner you know during a race or at the end of the race are you fatigued and you give them a scale and they give you a score now we're thinking that's the best way to measure fatigue but that's distinct from the functional consequences of fatigue and the word there is

fatigability i think that's what you were talking about so fatigability is how much work can a muscle do before it can't do before it reaches its limit so the functional term is fatigability a person who's more fatigable can is only capable of doing less work than one who is is not so we i think it's very important conceptually to make the distinction between fatigue as a symptom and its functional consequences with measures of fatigability somehow i knew that you would correct some aspect of my vocabulary throughout the course of this throughout the course of this conversation and you're not the first nor the last it seems like every time i bring on uh some high level physiologist or researcher PhD there's some ask there's some aspect of this is how we would prefer to describe it to have more accurate vocabulary right which i think is which i think is super important but let's kind of go back to the the the the important points for an athlete that's actually like looking at these propositions right because they're going to be able to they they might or might not care about the difference between fatigue and fatigability but they know that they're going to have to go out into the field go run 50 miles with 10 000 feet of climbing and things like that and they want to know how to they want to know what's going on and then how to better train for them and as i mentioned earlier the point of view that most endurance athletes come out this with is from

a cardiovascular perspective like it takes months and sometimes years to produce some of these cardiovascular adaptations in order to get the aerobic system better but it's not entirely true or at least the dose response is entirely analogous from a neuromuscular point of view and part part of part of the reason that we know this an example that i use a lot is just with the repeated bout effect where you can take one single bout of eccentric exercise and it provides a protective effect for subsequent bouts of exercise and we don't see that normally on the cardiovascular side it's not like i can go out and run if nobody if i hadn't run before it's not like i can go out and run two miles and all of a sudden i'm better you know one or two days later so let's kind of go through this concept and where i'm going with this roger is i want to try to figure out if we know or if we have some guidelines on what the doses it what the dose would be to improve the neuromuscular system but let's start out with just the repeated bout effect is like a like a baseline for this so the repeated bout effect again the fundamental question to a physiologist is it changes in the muscle or is it changes in the nervous system um i don't think we know the answer but i can give you an example so suppose that i perform some lengthening contractions a protocol of lengthening contractions with the right leg and i do

it on multiple occasions and i demonstrate a repeated bout effect on the right leg okay the left leg's doing nothing and then i measure the left leg and i see a repeated bout effect in the left leg it's crazy nothing it's done nothing i know so clearly the nervous system plays a role in the repeated bout effect i'm not saying muscle doesn't but there is there are probably both there are adaptations at both levels so becoming familiar with the sensations i think is a very important part of this now the field doesn't have enough knowledge to answer your other question is what kinds of adaptations i mean i understand practically why this is important but i couldn't give you an answer with any confidence at all we can't even agree on what causes the repeat about effects let alone how to how to control it yeah it's tough and it's something that i've always struggled with as a coach because once again we can look at classic um in like endurance or literature that's more focused on like the traditional endurance sports so the 10k and the marathon things like that and through that we've developed what i would call like guidelines for adaptation so we know that a certain amount of time exposure at a particular intensity can produce a certain level of adaptation i go out and run at an aerobic pace for two hours and it produces x amount of adaptation that i'm looking for and what i've been trying what

i've been struggling with over the past several years just with coaching a lot of trail and ultra runners is how do we look at that type of dose response from a neuromuscular point of view because i kind of view it as a different problem right i don't view it as an aerobic problem and i don't view the solutions as aerobic solutions so i'm always trying to figure i'm always trying to figure out like where are the guideposts that we can look at to say okay we need this amount of exposure that amount of exposure you know i understand the question and but i just don't think that we have the science to answer it uh and i do agree with you that it is a different kind of an issue so uh we know from several studies that if you do prolonged contractions low intensity prolonged contractions uh most of the reduction in the force produced by a muscle is due to decreases in the activation signal from the brain that's very clear so i mean to rephrase your question a little bit i think it has to be a key element for prolonged running has to be learning how to sustain that level of brain activation now how much training is necessary to do that i mean i i have no idea it's a important question but i don't think we can answer that yeah i i know so here's my theory and you can feel free to bat this away or let me know which what you think about it i mean my theory is is if i have an athlete that is

training for an aerobic event trail ultramarathon and we also need to tune their neuromuscular system in order to combat that type of fatigue the amount of work that i need to do specifically in that area is markedly less than the amount of work that we need to spend doing or just general aerobic endurance training so let me just give you a practical example right i'm going to have a runner that runs six days per week they're going to go out and they're going to train at an aerobic intensity six out of the seven days per week once out of every two or three weeks only once out of every two or three weeks i'm going to have them do a really hard downhill session and it's because i know proportionally i need more chronic work on the cardiovascular side than i do on the neuromuscular side and then you fold into the then you fold into the equation all the risk taking propositions and injury and kind of things like that but i guess my point is is it's certainly not a twice a week activity that i'm having that i'm having them do i'm having them do it sparingly and knowing that in conjunction to that they're also training out on the trails and they're getting some sort of neuromuscular adaptation that way maybe in a much lighter setting but anyway that's kind of what i've come down to is that it's a less frequent dose to get an adequate response for and that seems perfectly

reasonable to me i mean i yeah yeah and i don't know the answer to it either it's just what i've kind of formulated over the years and seeing athletes adapt right is there anything that we know and i've been once again i've been using this compare and contrast between typical cardiovascular endurance types of exercises and then more neuromuscular types of adaptations is there anything we else that we know when we compare and contrast those two that could help give us some guidance on this type of prescription um so i i guess one thing i'm curious about so the the your neuromuscular workouts is primarily focused on downhill running is that correct so what what are you trying to do to activate like the thigh muscles and the calf muscles are you trying to stress them or yeah it's just the run themselves so so certainly we know when we see this in observation but we also see this in in in research that if you're just running a down if you're just running the same downhill at a higher speed it's going to stress that system out more the athlete's going to be the athlete is going to have a higher degree of fatigue ability i'm trying to use your vocabulary now that you've enlightened beyond um uh in that session as opposed to if they're just normally running but that's the focus and the the issue that the athletes are trying to combat is late in a race after they've been running for multiple hours being able to maintain their rate

of descent speed and the way that they maintain it is they have to keep their coordination up they have to be able to produce force you know or as as you know as they're having these lengthening contractions on on their quads and things like that and i don't think anybody to my knowledge has the right prescription in terms of how to actually train for that so that's exactly what i was thinking when you were talking i would imagine that as a person is approaching the end of a prolonged activity that coordination can become an issue especially if you the activity involves repetitive lengthening contractions and there are different sensations that can influence how the timing of the muscle activity a person probably needs to train to be familiar with the different scenarios that can enable them to accommodate changes in the terrain for example or you know the competitive atmosphere of a race uh so i think it's that coordination is probably quite an important aspect of the training program well and you see this play out in real time because more people fall later in races versus earlier in the races right but so what is going maybe you can you're going to be able to describe this much better than i i can obviously what is going on that causes athletes to say that they're more clumsy later in a race versus the beginning of the race what's the physiological neuro neuromuscular phenomenons that are going on at that point i'm sorry to be repetitive but it's got to

deal with sensations in my opinion so if i can just go back to a little bit of basic neuroscience again just to put this in some context so what we know is that the automatic behaviors that our nervous system produce and running is an example of an automatic behavior so an animal can run with its head chopped off it's very clear okay so these automatic behaviors are controlled by small networks of neurons in the nervous system called central pattern generators you may remember that term so that we in our bodies we have a bunch of central pattern generators they control things like swallowing chewing breathing and running so these central pattern generators produce this rhythm so it means turn on the flexors turn off the extensors and do that all in an alternating way for each leg so we have this basic rhythm but this basic basic rhythm is modulated by the sensory feedback that we get so the rhythm can be changed so the rhythm controlling what the leg muscles will do is is modulated by sensory feedback which depends on what's happening in the person surrounding so you're running on uneven terrain you have to perform lengthening contractions in which you are carefully controlling uh the increase in the length of the muscles and you're relying on sensory feedback so if you

have disruptions in sensory feedback then this is going to cause difficulty in having that translated into appropriately timed muscle activation sequences and so to a lay person this would see this would appear like oh i'm being clumsy i'm not controlling things carefully i don't know how long my stride should be my strides are becoming more variable my wits and and so i'm afraid of falling over so that the burden on interpreting these sensory signals is immense and could probably have significant consequences and i think with your training program and having your athletes do this you know once uh such a training session is probably a key and they're learning how to reach their peak performance in these types of events yeah and from a as a practical consequence we always see the most amount of performance discrepancy over the last third of races versus the first two-thirds of races which isn't that indifferent from a marathon or a lot of other races but it's very market in an ultra marathon situation that the athletes that do really well they're creating that performance separation over the last third of the race and not over the first two-thirds of it so how do you see that when you're watching an athlete what do you see is happening during that in terms of what their legs are doing okay so this is this is going to lead into another question that i have so literally and i've been in the situation where i've gotten the opportunity to pace athletes for the last half of a race or i go out and i crew for them uh during during an ultra

marathon and it's it's um apparent to me because i've looked at a lot of athletes in a biomechanical setting essentially the the biggest thing that sticks out is their ground contact time is longer at the later part at the latter parts of a race versus the earlier parts of the race and that's not just because they're running slower it's not proportional to their decrease in speed later which you would always expect you run slower there's long ground ground uh ground contact time and things like that and what i interpret that as to your point is a disruption in the nervous system for sending the feedback in order to take the next movement right exactly that part of fatigue ability and it's actually this brings up my next point runners intuitively have figured this out and one of the other strategies that they've used to kind of like circumvent this is intentionally changing their gate and this got a lot of attention several years ago where they hooked a lot of runners up to these biomechanical sensors that just looked at their gate patterns from the beginning of a race to the end of the to the middle of the race and they found out that they used slightly different gait patterns as the race went on whether they were doing consciously or subconsciously but it's it's led to this notion that

a way that you could combat some of the fatigability that's going on is to intentionally change this gait pattern to save something and i don't know how much water that holds or not maybe you can give us a perspective on that so i think the the key issue in in the question that you asked is this something that a runner can do intentionally or is it a consequence of changes in the output from the central pattern generator i would tend to think it's the latter i don't i would be very surprised if a person can while running decide deliberately decide to change my gait pattern from a rear foot striker to a four foot striker i think that would be difficult on a step-by-step basis and so if you are having these kinds of adaptations i think i would guess in the absence of data of course that um what the person is doing is that the sensory input is changing the pattern that it's that the central pattern generators are producing so this could be for example pain that's developing in a foot muscle or in parts of the foot or discomfort that a person is experiencing or accumulation of metabolites within the muscle these all generate

sensory signals that have the possibility of changing the rhythm that's being generated by the central pattern generator so i would be more inclined that it's a consequence of these sensory signals these sensations rather than some well planned out strategy to change the uh what muscles are being activated i'm getting a little bit of a chuckle out of this because we see this in the marathon a lot right where athletes that succeed they tend to they tend to look the same at the end of a marathon as opposed to the beginning and athletes that are you know falling back through the pack they just tend to look worse i mean everybody has this observation whenever they've looked at a race that they can tell hey they looked like this earlier and they look like this now whether it's a marathon or ultra marathon or whatever and what you're saying is is that is a direct result of how the athlete is sensing the environment around them and changing their pattern or changing their gait pattern accordingly you know it's also the environment within them within themselves i mean in addition to this around them i want to go back to this concept of the central pattern generator and i apologize that i didn't send you uh notes on this uh earlier but i do remember that part uh from your course and i remember a lot of the animal models that uh that we had discussed about were done in cats um this is i think this is going to be just interesting i don't know if there's an uh uh a take-home point for athletes on this but this concept that animals can run without

super spinal input is absolutely fascinating but everybody should know this because of the phrase running around like a chicken with their head cut off exactly exactly but nobody connects the two nobody actually connects this phrase that has been passed down for years and years and years to this concept that animals don't need super spinal input or their brain to locomote so let's go ahead and explain why chickens can run around with their heads cut off but this is not a trivial uh issue because it has practical i mean clinical significance for humans because when a human has a spinal cord injury the fact that you can produce locomotion without a connection to the brain is very important so what we know from the studies that you just mentioned is that if you cut the connection from the brain down to the brain stem and the spinal cord so there's no connection and you stimulate a part of the brain stem you can induce locomotion so a cat can walk for example so we know now in research that's looking at humans with spinal cord injuries if you take a human who has who cannot walk has lost the connection and you provide electrical stimulation to the back of the spinal cord now that's where the sensory information is coming into the nervous system in the nervous system in a human you activate the sensory fibers very carefully you can produce

locomotion so i mean we we just have not we don't appreciate enough the very important role of sensations and the things that we do on a daily basis and i'm i'm sure it's critical uh for events like ultra marathons yeah it's it's i i think that that that just knowing that is absolutely fascinating but like i said earlier it's something that's entirely lost on a lot of people but it really shouldn't be because we have this really common we have this really common phrase that we know yeah um okay i want to ask you one other point about um an ergogenic aid that has popped up uh kind of more recently uh that i wanted to get your input on so we we've seen across the sports performance landscape and it hasn't really made its way into the endurance landscape as much as as it has like strength and conditioning with uh direct transcranial direct transcranial stimulation so the concept is and nobody can see this because i'm i'm because this is a podcast but the concept is is you have a set of you have this thing that looks like a set of headphones and what it's doing is it's passing uh electricity through your motor motor cortex at a very light rate it's the amount of electricity that it takes to send a text message is how people uh analogize it too and the theory is is that it reduces the the action potential that's necessary

to produce a voluntary contraction and the use case for an athlete is is they put these headphones in they zap their brain they go out and train and then that training is either done at a higher level because of this effect or it has bigger adaptations because of something else that is going on is this a plausible mechanism of adaptation your opinion and what and what's going on so the research findings on the use of this kind of direct uh current stimulation of the brain is very mixed some studies have found positive outcomes and some have found no influence at all but let me just phrase the the question in a slightly different way so you're passing um electrical current from one side of the brain to the other side of the brain now our brains contain many different things and only one very small part of the brain is involved in generating this activation signal so it seems to me that we're stretching our imagination if we imagine stimulating all parts of the brain is going to have a functional consequence on this one part that is really critical um some of these studies have had that uh have not been able to distinguish between a placebo effect and a real effect so if an athlete thinks this is going to work uh there's a good possibility it will work even though there's no physiological basis for it so i i don't think there's sufficient evidence to

suggest that this is a is a worthwhile ergogenic aid yet maybe it is but the evidence is not there yeah it's a tough deal and it's hard to it's hard to placebo control it because i've i've experienced it before i've had a unit to to to test out and um the way that i describe the sensation it's like if you were to lick a nine volt battery you know that sensation when you look at nine everybody did that when i was a kid at least i did it when i was a kid but if you put it on top of your head that's the sensation you have and it's hard to placebo control something like that well you can change the intensity or change the frequency i mean you could manipulate the electrical current in some ways to do that yeah anyway so it's just something that that pot that has been popping up more recently in in sports science and it's i mean it there's no doubt that it's gotten hot i mean especially professional sports teams they tend to be um they tend to want like first mover positions on those and early adopters to that type type of technology even in advance of the research coming out that demonstrates that it's efficacious or not yeah i mean i certainly don't under appreciate the importance of practical observations i think often a an experienced clinician or an experienced coach has more reasonable ideas about what's going on than does a scientist so i think you know both both perspectives are very important um and but scientists are usually a bit slower to on the uptake

and necessarily so right slower and much more deliberate i always think of how many things that have how many things that have been jumped on too soon that we've that we have later on down the road had to retract and say yeah that was a really bad idea i mean i could go through a hundred of them and this might be one at the end of the day it wouldn't surprise me yeah okay roger we're gonna let you go i really appreciate your time uh with us this morning um i'm gonna include in the show notes some links to your research but where can they where can listeners find out a little bit more about what you guys do at the university of colorado um so you can go to the website for our department which is the department of integrative physiology and if you just go to the research you can scroll down and find my name and just click on that and i'll take you to my lab web page and you can see what we're up to what's coming up next what do you guys have in the pipeline right now uh so we have uh one of the things we're very interested in is manipulating sensory feedback in people with multiple sclerosis we find that early on in the disease progression if we apply electrical stimulation that activates just sensory nerves it improves the mobility of people with ms immensely so much so that when they participate in the study they go out and buy their own electrical stimulation device so you don't need statistics to tell you that they think it's effective you know i mean i always i've there's been a very robust history

of research that starts in a diseased population whether it's multiple sclerosis or diabetes is one that's coming to the top of my mind right now that eventually makes its way into sports performance yeah um so maybe we might see that a few years down the line i think that's super interesting research yeah yeah we may yeah well it's good to see you again jason yeah to talk with you yeah good to see you as well i really appreciate the time all right and there you have it there you go thanks to roger for coming on the podcast today really appreciate your time and your expertise and i promise i'm going to hold on to this book for as long as it will hold up it is getting a little bit ragged the spine in particular has definitely seen better days but as long as the pages are legible i'm going to hold on to it appreciate the heck out of all the listeners today and hey 2021 is here races are coming back on the calendar and if you think that one of our coaches is right for you to get you ready for any of the big or audacious goals that you have for 2021 hit me up on social media or go check out train right.com for all of our coaching package options we would love to work with you and we are always taking on new athletes that have big goals that's it for today folks as always we will see you out on the trails you