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How to Figure Out Fast Twitch?

I would like to know the easiest way to figure out if I am fast twitch or slow twitch biased. If you know any quick little tests or tricks to answer that let me know thanks.

1.) Take 80% of your max bench or squat.
2.) Do as many reps as you can (no caffine, creatine or anything like that before the test, pre-workout nutrition is fine though)

If you get 0-5 Reps you are dominated by Fast-twitch muscle fibers. Doing 5x5 programs, 3x5, singles, doubles, triples would benefit you the most in your training. You were made for quick reaction and explosion. Also pretty good at maxing out.

If you get 6-9 reps you are equally dominated by both. You can make equal gains during a hypertrophy phase, power phase, etc…

If you get 10 or more reps you are dominated by Slow-twitch muscle fibers. Doing 3x10, 2x15 wil benefit you the most. You were made for endurance activities. You are also good at cranking out those extra reps.


Sounds about right, it will give you the general idea.

Though I don’t think you’d have any muscle if you can do 0 reps @ 80%.

Good post from texass. Just one extra point: your fast twitch ratio will not be the same for all muscles. Thus you might need to vary your rep range depending on what you are exercising.

[quote]sharetrader wrote:
Good post from texass. Just one extra point: your fast twitch ratio will not be the same for all muscles. Thus you might need to vary your rep range depending on what you are exercising.[/quote]

^ True. Usually MUCH more slow twitch in the legs, hence 20 rep sets.

Thanks for the help guys. I will try that and see what happens.

I disagree with the 80% test, because I think it is more a reflection of your training background. Somebody doing nothing but sets of 8-10 for two months is going to be able to do way more reps with 80% than somebody who’s been doing max singles. Does that mean they are more fast-twitch? Not neccessarily.

As far as practical application goes, I see no real point to the 80% test, to me it is a gimmicky thing thrown out there by a lot of theorists, without real regard to how it would apply to training.

Just train for you goals and your nervous system and muscles will adapt to that goal. The only possible exception I see here might be bodybuilding, as some individuals might respond better to higher reps and some individuals might respond better to lower reps. But as far as sport application goes, 90% of training should focus on the HTMU’s anyway.

Another way is to get your 5rm 3rm and 1rm… If they are about 20 lbs or more in gap, that means you are fast twitch

[quote]Konstantine wrote:
Another way is to get your 5rm 3rm and 1rm… If they are about 20 lbs or more in gap, that means you are fast twitch[/quote]

Perhaps, or perhaps that individual has just been training using a lot of singles and has lost some strength-endurance? Perhaps that individual doesn’t have the mental toughness to grind out higher reps? Also, I don’t think there’s many 800# squatters who can pump out 760 for 5 reps.

What I’m saying is, if you are a powerlifter, and you do some test and it shows you are “slow-twitch”, should you do 3 x 10 bench and hope to increase your 1RM? I hope not!

I wonder how many people who espouse these tests have actually done them and applied them to training. I know that personally I have done as few as 2 or 3 reps with ~80% and as many as 7 or 8 depending on the training cycle I was in.

Also, the movement you use will skew this test. Do the 80% test with deadlifts and just about everybody’s going to come up as “fast-twitch.” Do it with dumbell bench and it’ll be the opposite.

Friggin nitpickers trying to make yourselves look smart. Listen, the only way to know fiber type is a biopsy. That’s not practical for most people. Thus, the 80% @ 1RM test.

Who said it was perfect? No one. It’s a proxy, a guideline. That’s all.

Skinfold calibers are not the most accurate things, either. But people use them because DEXA is usually unavailable and autopsy is undesirable.

Again, I know some think that picking about a test makes them look smart and knowledgeable. But it really doesn’t. If anything, it exposes ignorance. After all, if you don’t know why the 80% @ 1RM test has value (because other tests are less practical), then you really don’t know that much.

How is your vertical jump? That can give you a quick idea. Or better yet, how was your vert before training?

I’m fast twitch in my arms, which is good for maximal effort stop sign pulls and breaking punching machines.

Apparently I’m slow twitch in my penis, I can get 10-15 reps with low weight. If I have lots of weight on the end of my penis, I can only get 1 or two reps before I realize what i’m doing, unless I take my alcohol supplement before my workout.

I agree with jtrinsey here. Not to pick a fight with CaliforniaLaw, but jtrinsey didn’t just nitpick for the sake of looking smart, he actually gave good reasons why the test, however convenient it may be compared to a muscle biopsy, isn’t that great at determining fast-twitch ratio.


Do you realize that no matter how many times you call somebody dumb or ignorant, it doesn’t make you look any smarter?

I gave plenty of reasons why the 80% test is inaccuarate and why fiber-typing is pretty much pointless anyway. I also backed this up with personal experience. You gave exactly zero useful input about the test and I’d wager to guess you’ve never performed it yourself.

It is already generally known that when training for size, certain muscle groups (hamstrings for instance) respond well to lower reps on average and certain muscle groups (calves for instance) respond well to higher reps on average. Does one need to perform a test to confirm this?

When training for athletic performance, how does fiber typing benefit? Again I will use the example of powerlifting. A powerlifter performs the 80% test and gets 3 reps. So he trains with low reps to develop strength. Another powerlifter does the 80% test and gets 9 reps. So… he trains with low reps because that’s how strength is developed. Sweet test.

Please contribute something useful to the discussion or go back to making fun of people who weigh less than 200 pounds. At least that’s kind of funny.

[quote]bigdaddy082 wrote:
I would like to know the easiest way to figure out if I am fast twitch or slow twitch biased. If you know any quick little tests or tricks to answer that let me know thanks.[/quote]

The best way to determine it is your vertical or look at running. If you were a trrack athlete what race would you perform best in? The Sprints (Fast Twitch)…Middle Distance (in between)…Long distance (Slow Twitch).

That test 80% x 1 is very inaccurate. If you can perform 80% for more than 5 reps then your are not working at 80%!!! Better yet. If you perform 80% x 1. Guess what, that is your max.

It’s true that even fiber typing by biopsy really isn’t worth a shit. It’s highly dependent on where they stick you and how and on the expertise/talent of the researcher.

Look at cyclists. Most have very slim legs. A very few have large, muscular thighs. I think they represent a reasonable cross section of the general population. I don’t know exactly what this show but it does demonstrate something.

My vert jump is horrible but i believe that is b/c I am 5’8" and 270 pounds. I have always been a good sprinter and horrible at distance running but I dont know if that is b/c I always did sprints and never ran distance.

The first question you should answer before even worrying about your fiber make up, is why are you training?

If you are training for general purposes, i.e. not to become a professional in whatever sport you wish to pursue, then fiber makeup shouldn’t matter to you much. You simply train the way others in your sport train and push it as hard as you want to achieve.

If you train for strength purposes and decide that you are slow twitch dominant, how do you think that’s going to affect you psychologically with your training? It is psychological suicide, basically.

However, if I were a Russian scientist trying to win some gold medals, I’d find out your fiber dominance to decide which sport would best suit you. That way you would be placed in a position meeting your highest potential.

This isn’t all that important for most of us weekend warriors/part time bodybuilders/part time powerlifters/whatever. Your choice of sport will depend on whatever gives you the most pleasure.

Getting back to the original question, if you still think finding out your true muscular fiber make up is important, read on-

First of all, I agree with jtrinsey who stated that the 80% test is not very accurate. Your body adapts to whatever stress you are putting it through.

If you are normally training high reps, you’ll be better at high reps and vice versa. Personally, when I was at my strongest, I could not handle 80% for as many reps as I can now that I have lost some of my maximal strength. Does this mean that my muscular fiber make up changed? I think we all know the answer.

I also must say that I agree with calilaw who said it’s not accurate but may be a useful tool.

A more appropriate measure might be to look at your athletic background and find out what athletic skills you were strong at during your youth. Kids naturally are given positions that best suit their athletic abilities in the sports they pursue.

For example, a small, fast kid would be more likely to play corner or safety while a bigger, stronger kid would play linebacker. No need to consult Soviet scientists on that one, it’s a natural occurrence on any youth sport team or playground.

Another example is track and field. If you ran track, it might be easier. Were you a sprinter or distance runner?

If you didn’t play sports as a youth, then first of all your parents should be kicked in the head. This is an instance where the 80% test would be helpful.

Running short on time, hope this was semi-coherent.


I think this of this shit as being sort of like an IQ test. If you prove yourself to be superior at so and such test, then you have have a pointless metric to brag about (like those MENSA twerps). If you test poorly, you have an excuse to suck- which no one really needs. Just lift, chase your goals and your capabilities will follow.