Muscle Fiber Typology

Research is being performed on how training effects athletes differently depending on muscle fiber typology.

How do we as self coached athletes start to think about these issues?

Do world class endurance athletes have a larger percentage of type 1 fibers than us average joes and janes?

Does this change how we reflect on the 80/20 research? Research suggests that athletes with a greater distribution of type 1 fibers can tolerate higher training volumes better.

Interested to hear some of the coaches thoughts!

Thanks for posting those articles!

I think as self-coached athletes, we probably have a sense for how we recover best and can use some of these suggestions to apply that to training. As a personal example to support that, I actually don’t handle high-volume training very well. In that last study where they show the TID% for the high volume training, that rings true to a similar TID% when I build volume and many of the same responses to suggest FOR (functional overreaching) are there. So I think we can take many of those outcomes (increased HR recovery, reduced peak HR response, reduced time to exhaustion, for example) and tie them to our experiences to inform how we structure our sessions.

I wonder how that can help to inform thinking about CTL because it’s so easy for some athletes to get attached to a specific “fitness” number, that they are always chasing it even at the expense of poor recovery or performance.

@ThermalDoc had a good video on this:

I personally have found that I need to go really easy to handle any kind of volume… And I have a VLAmax of 0.59, so I have more fast twitch than most road cyclists. Additionally I have to be pretty careful about my intensity or I just feel wrecked for days.

Is there anything out there (papers or coaching experience) that suggests whether or not there is a difference in muscle fiber recruitment patterns when comparing long low intensity exercise (like hours) and short high intense exercise (either 30/30s or longer 3-4 min intervals)?

One comment Dr. Seiler (@stephen.seiler) made on one of the podcasts with Trevor Connor (@trevor) was that for that long ride, toward the end–with increasing fatigue in Type I fibers–we may see an increase recruitment of Type IIa (Type IIx also?) such that these begin to get an aerobic stimulus.

When doing high-intensity intervals, Type IIa & Type IIx are very much recruited. Question is are they recruited in the same way? And if so, are they recruited in the same way but within a different metabolic environment/demand?

“different metabolic environment/demand” is vague and wishy-washy (and makes me almost not want to ask the question LOL). I don’t know how else to express it. If the recruitment pattern is the same, then what is different about the two scenarios for non Type I fibers?

+1 @ryan .

Self coached or coached, adapting to your own body is the key to success. The principles of training (extend / intensify / recover) apply to all of us. It’s the numbers that should be adjusted for each individual.

Without knowing your own type I / type II distribution, your legs will tell you whether the volume/intensity was ‘just fine’ or ‘too much’. Just wait for two days :slight_smile:

Thanks @kjeldbontenbal. I think that’s a good coaching answer.

I’m looking for a physiology answer.

@tshortt Thanks for the gentle feedback :slight_smile:
The physiology: recruitment pattern is always the same: type I → type IIA → type IIX.

That is, every time you need more torque you recruit more motor units (=fibers). As soon as 'type I’s cannot provide the requested torque, you move on to the next type.
So: 1) more fibers, if not sufficient, 2) additional types.

When cycling, this means that if you are going steady at ‘type I’ pace, as soon as you press down a bit stronger, you have recruited the other types too. So even in low-intensity training you will often recruit the other types. At every traffic light, when you reach for your bottle, etc.
However, since the recruitment is very short in time, the type II’s will not fatigue to the level you will feel it the next day.
If you go on for long, the type I’s fatigue and your body has no other choice than to use the type II’s instead. That is not because you run out of fat, but simply because of muscle fiber fatigue.

As for the difference in scenario’s: there is no difference in type I recruitment. They are ‘on’ all of the time. For type II’s the difference is that they are ‘on’ al lot of the time and ‘a lot of them’ and ‘to a high percentage of their force capability’, while in low-intensity they are ‘on’ a short amount of the time, only a few fibers, and for a low percentage of there maximum force.

1 Like

But it really was good coaching feedback. Seriously. :-). And that is what most of us are here for so, all good.

This is the way I understand it as well (size principle). My issue is that if I take this to its logical (but perhaps ridiculous) conclusion: the benefits I get out of the end of that long ride I can also get by high intensity exercise. I think that is either not true or a gross over-simplification. See what I mean? It might just mean that those long ride benefits do not simply come down to muscle fiber recruitment.

I see what you mean.
Building endurance in the oxidative fibers requires overload in training duration, as that will trigger the development of mitochondria, fatigue resistance etc. So you can’t shortcut that with high-intensity training.
In order to work your type IIA’s right from the start, you should set your intensity to the appropriate level. As far as i know there is no method to define that point, but i suspect it to be somewhere between LT1 and LT2.

How I understand it (and please correct me). The long slow rides helps to improve your ability to recruit those IIA fibres to work as type I fibbers, were the short hi intensity only trains the IIA fibbers to be better at the job they are all ready good at. @kjeldbontenbal does that get at what you were asking?

Is this intensity the one that @steveneal finds with his Balance Point Test?

1 Like

How I understand it (and please correct me). The long slow rides helps to improve your ability to recruit those IIA fibres to work as type I fibbers, were the short hi intensity only trains the IIA fibbers to be better at the job they are all ready good at. @kjeldbontenbal does that get at what you were asking?

I wasn’t asking :slight_smile:
Your type IIA’s are recruited when needed and will work as type IIA fibers. They might be used instead of type I’s if those are fatigued. But the principle remains the same: recruit more fibers if those already recruited don’t deliver the force you need.

Is this intensity the one that @steveneal finds with his Balance Point Test?

No, that is, we have no proof of that. (@steveneal said something like that in a different post)
But it makes sense that there is a relationship between fatmax and the utilization of type I and IIA fibers.


I really have not proof of these but would love to understand more about muscle fibre typing and the intensities I use.

The Lactate Balance Point that I do find is between LT1 and LT2, and can vary widely with individuals. It can also be trained to improve while keeping LT1 and LT2 the same.

So an athlete could have LT1 at 200w, LBP at 220w and LT2 285w. This athlete could be trained to have numbers such as LT1 200w (same) LBP at 245w and LT2 285w, so it is possible to improve wattage at LBP. IF the above example would happen, the athlete would have better race results with the same LT2.

You can also bring down the LBP wattage by training at appropriate levels below it, so if an athlete is peaking too early the LBP is likely getting close to LT2 and can help me identify what type of training to give the athlete at different times of the seasons.

As mentioned already I have no proof of muscle fibre typing at this intensity but I do know how raising LBP affects an athletes performance.