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Which Muscle Fiber Type Atrophies Faster?


Which muscle fiber type (fast twitch, slow twitch) atrophies faster? If two athletes (lets say one bodybuilder and one powerlifter) discontinued their training, diet, etc which lifter would noticeably atrophy faster? I would guess the bodybuilder. What do you guys think? Also any supporting evidence would be helpful, thanks.


See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II's? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.


That explains why I suddenly found the strength to overhead press that bear despite not lifting for a year, didnt feel it in my delts cuz the bear wouldnt stop squirming.




Dear god...they would have kicked me out of my major if I wrote something like this in college.


Interesting. I was under the impression the Type II fibers atrophy more quickly.


I must admit. I am confused. I just thought 2 muscle groups same size same density would diminish at the same rate. All things being equal.

I'm really curious to see a answer to this. I thought it was just all about how fast persons body would burn its energy sources.


The better question is why do you want to know? Are you planning on training a while, then slacking off for a long time?


I say the bodybuilder based on the fact that type I muscle fibers hold more glycogen, water (and a bunch of other crap that I dont remember names for), the visual effect I think would be rapid due to the body no longer needing to store such large quantities of these nutrients (or whatever they are) to fuel intense contractions I believe type II muscle fibers are denser and contain less of these thingymajjigers and more of the muscle size is actual muscle... I think the bodybuilder could also recover from a layoff much easier due to the evidence above.



I did train using the strength program for 2.5 months and havent lifted in a year since, Im not sure what my lifts would look like now, but I do some bw exercises every now and then and there has been almost no change in my push up and pull up count... This confuses me


I pissed off a lot of my professors when I was getting my masters. haha.


Thanks for this. It's been a while since we've had a real thought provoking intellectual on here.

Now if you could explain the 'survival mechanism' that causes sedentary people to have the 'highest fibre area of type II's', it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.


That would be true but type I and type II fibers are not the same size or density.


So we are saying that its a training and not size that determines the 2 types?


I'm trying to determine how this could ever possibly help me in the gym tonight.


Think about this. Take a bodybuilder. He trains with high volumes to get all those sick pumps, brah. These sweet pumps improve vascularity, capillarry density (for more pumps), and the oxidative capacity of muscle. These are all Type I characteristics. People just automatically assume that weights=Type II fibers. This is just not true. When the majority of the earth were small hunter gatherer communities, there were no weights but humans still had the capabilities to sprint after and kill their food. Dyanamic and Maximal efforts. These are characteristics of Type II fibers. Humans that lacked these traits fucking died in terrible ways. Like, eaten by something they couldnt outrun or they starved to death. This is where the evolution of fiber typing comes in.

The body reacts to the stress placed on it. Tons of volume and muscular work results in adaptations in fiber size, intermuscular coordination (although limited), and neurological adaptations that all attribute to the gains you get in the weightroom. Your body recognizes the need to handle more volume, thus, Type I fibers grow and Type II fibers take on Type I characteristics.

Now, take some asshole who has never lifted a weight in his life. Due to the human races hunter/gatherer roots, that guy is going to have a higher distribution of Type II fiber area than a bodybuilder. Just in case a fucking t-rex breaks into his living room and he has to get out in a hurry.

He has had no stress to adapt to.

There are tons of studies on this stuff. They just don't ever get published anywhere that anyone except nerds like me ever reads.

When you really start critical thinking about all this shit, it paints a perfect picture of why no one can explain exactly what causes delayed onset muscle soreness... because if you got sore while you were running from a lion, you would die.


Absolutely. Train slow with tons of volume=Type I, Train fast with heavy weights and low volumes=Type II. It's not as cut an dry as that but it is pretty close.


Done properly High rep training should result in more type I muscle fiber growth, whereas low rep training should result in type II muscle fiber growth, so yes it is determined by training, but size is also a factor but does not determine the type. Bodybuilders generally have larger muscles, due to type I muscle fibers having more potential for growth as well as holding more necessary fluids ie: glycogen, water etc. Type II muscle fibers are denser and are actually comprised of more actual muscle tissue but have less of a visual effect which I explained.

Still confused as to which atrophies faster.


What he wrote isn't exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution...as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.


What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.