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Body Fiber Compostion

I’ve been wondering this for a while now, how can you find out your body’s fiber type? Fast Twitch, Slow Twitch, or a combination.

How do you find out which kind do you have more of?

poliquin lists a technique that you can use in his poliquin principles book. although not completley scientific, it seems to give a decent answer.


look at your strength and weakness are you better at weightlifting or are you better running long distance… Thats really the only way you can tell what type of muscle fiber you are more dominate in… I wouldn’t get myself all wrapped up in this though…

You could have a muscle biopsy done on all the muscle groups in the body but that would be painful and not practical.

All the other tests (reps w/% of 1rm) give some picture but are really not very accurate because there are too many variables to account for. Don’t worry about it, it is not that important.

You should realize that different muscle groups have different fiber make-ups. But you are right that individuals can have different make-ups.

A good way to test legs is sprints. Or you could do % of squat/deadlift max.

Arms you could use curls/tricep ext.

Back use pull-ups.

Ultimately, a muscle biopsy test would be your best bet.

fitone-That is the single most short-sighted answer that I’ve heard in a long time.

Vaines-The only true way to determine your fiber type is muscle biopsy, but no one wants to get stuck with a bunch of needles. That said, as I recall, Poliquin advocates finding your 1 repetition maximum (1RM) on a given exercise. Then, rest ten minutes and perform as many reps as possible at 85% of your 1RM of that same exercise. For most, this will amount to 5 reps. If you perform fewer than 5 reps, you are likely fast-twitch (FT) dominant for the involved muscle(s). For 5 reps, you are mixed fiber type. For more than 5 reps, you are slow twitch dominant. Note that exercise patterns can affect one’s fiber type.

Additionally, one can determine fiber type with electronic muscle stimulation (EMS). EMS first activates FT fibers-the opposite of what takes place when a muscle voluntarily contracts (ST fibers fire first, and FT fibers are only recruited as the contraction’s intensity is increased).

Finally, Alessi and others have noted that vertical jump is highly correlated with fiber type (higher jump=fast twitch), although I’m not totally sold in the idea.

Hope this helps.

I guess im a mix of both then.
I can jump high, and run fairly long.

Wow, Vaines; you didn’t listen to much of what I said. Basically, the “long running” crap is just that; I thought that I had refuted fitone’s idiocy with my first post. Lots of fast-twitchers can run for a long time…

Read this article:


Gee Merry Christmas! Listen to E-C!

Man, am I the only one around here who sees that E-C is consistently getting more and more knowledgeable?

E, you continue to drop quality bombs of knowledge with great confidence. I truly respect and appreciate your dedication to the sport, lifestyle and your peers. Keep up the outstanding work, bro.

Now, back to Vaines. There are several ways to attempt to determine this. Of course, the muscle biopsy would be the most accurate, yet invasive, option. Other than that, the 85% 1RM test is your next best option. That example, actually, was purported by Arthur Jones, although it appeared in Poliquin’s book. A mixed fiber individual will get between 5 and 7, while anything less than that would be predominantly fast-twitch and anything greater would be more slow-twitch.

Like 'Chine mentioned, this is not homogenous between muscle groups necessarily. So you’d ideally test all muscle groups.

Another indicator of having more fast-twitch fibers would be when doing higher rep sets (i.e. 10-12). After a rest of 90-120 seconds, if your reps fall off substantially (>2), you might be more fast-twitch. However, that could also be due to lack of training in that rep range or just the fact that you have no focus or will-power:-)

You’re not the only one, Timbonator…

My contribution to the discussion is going to be to note that while CP’s (or AJ’s :wink: ) protocol has some value, there are too many other factors to consider to really make it reliable. IMHO, the single most important one is going to be training age. Personally, everything in my life indicates slow-twitch dominant, but as I’ve gotten older I’ve become more and more responsive to fast-twitch training (i.e., higher weight with fewer reps). So I think that you need to really take a good look at all the factors before deciding…and then realize that even if you find a decent answer for yourself it’ll probably change in the next few years anyway.

Sorry, but that’s just the way it is… :slight_smile:

The 1 rep/5 rep max test would only work at the absolute beginning of one’s training career…a.fther that one could assume that any training could improve neural effeciency considerably, thus skewing the data/results…

Once again, one of those things that I ask what does it matter??? OK lets say you figure out you have a mix of 56 fast twitch fibers and 44 slow twitch in your legs…what the hell will you do with this info??

I had asked this very question to my old Physio prof, and he asked me to come by the lab after class. To my horror, he had what seemed to be a very fancy leg extension machine hooked up to a computer. He had me do 50 reps as hard as I could. Each rep was measured up to 50. The computer measured the force difference between the 1st and 50th rep. Then with some equation, it came up with my %FT and %ST. You could go this route, but you better have a wheelchair ready, cuz you wont be walkin for awhile.

Any tests involving weight training can be biased by training age, training emphasis, and the efficiency of your nervous system. If person A and B both have the exact amount of muscle fibers and the same % of FT muscle fibers yet person A has, through training, learned to better use his FT muscle fibers than he will appear to be more fast twitch than person B. FT fiber contribution is most important in tasks involving loads of less than 40% so tasks such as pure ballistic activity (speed) are the best indicators. ST fiber contribution rises as the load goes beyond 40%. Tasks such as vertical jump, tapping the feet in place as many times as possible for a predetermined amount of time or tasks involving handspeed are good indicators. Eric Cressey brings up an interesting point regarding EMS machines and the recruitment of FT fibers coming before ST in that instance. I’m probably more fast twitch then most and EMS machines absolutely kill me even at a very low intensity. I’ve noticed others are able to tolerate a much higher output by the machine whereas with me even a little bit hurts like hell. Could this be because I’m more fast twitch?? I don’t know but it’s interesting.

Eric My “idiocy” if you read this article printed up in t-mag that theMage pointed out where am I wrong?

fitone- You typed:

“look at your strength and weakness are you better at weightlifting or are you better running long distance… Thats really the only way you can tell what type of muscle fiber you are more dominate in… I wouldn’t get myself all wrapped up in this though…”

Your post was idiotic and short-sighted in that you stated that your method was “the only way you can tell what type of muscle fiber you are dominate [sic] in.” Then, you posted a link to an article in which Ian King specifically refuted your assertion by listing SEVERAL ways to determine estimate fiber composition. That, in essence, is idiocy times two. It’s like pissing on your own campfire.

Secondly, by saying that your method is the “only way,” you also imply that it is the best way. While it may provide a rough estimate of fiber makeup, other methods are more appropriate and accurate (see above). As I said before, I know lots of athletes who can train heavy AND run long distances. Who is to say that you have to be deficient in one regard in order to excel in another?

Finally, you recommended that Vaines not “all wrapped up in this.” Knowing your fiber type is, in the opinion of many prominent strength coaches (including Poliquin and King) of paramount importance in designing effective programs. Christian T. even uses them in his block training protocols. I happen to agree with all of them, and I think that Vaines, as a newbie, would be well-served to “get wrapped up in this.” In fact, I think that all newbies need to make an effort to go out of their ways to “get wrapped up” in things; isn’t that why we’re always directing individuals to the search engine?

I wouldn’t have called you on it unless I could support my reasoning with logical arguments. Likewise, I probably wouldn’t have called you on it PERIOD if you hadn’t said something that would deter an enthusiastic, inquisitive mind from exposure to valuable information.

Char-Dawg, our boy wonder E-C does it again:-)

And, Char, the point you bring up about training age and responsiveness to lower reps is one of the primary principles that Coach King always advocates, which I’m sure you’re aware.

Kelly, you illustrate the point rather nicely. However, I feel that it’s important to recognize that although maximal power is achieved at approximately 30% of Vmax (i.e. maximal velocity of contraction), Vmax is only achievable in laboratory settings and not within the human musculoskeletal system. There are too many constraints within to allow for Vmax to be achieved. What am I getting at? Hell, I don’t even know!

I don’t think I need to get into power development, though, because this is beyond the scope of this thread.

LOL. Nice job, Eric…

And just to add a little more fuel to the fire, anyone out there remember Johnny Fuller? He was one of the top 10 or 15 bodybuilders back in the early 80’s, who also happened to be a pretty decent marathoner. Fast-twitch? Slow-twitch? Or could it be that someone’s just, ahhhhhhhh, wrong?

IMHO…and of what i have read and learned and experineced!

Before begining, a questions to answer is what do you want to get out of weight training?

Are you interested in getting stronger to better your 1RM in a given compound movement such as deadlift or bench press? To do this just keep adding poundage to the bar! a pound or 2 a week is 50-100p a year! No real need for fibre testing.

BUT, if you want to get BIGGER, more muscle (and therefore stronger) then knowing your Fibre type will help you - as you can find out whether you are overtraining or undertraining a particular muscle.

The first point is to do fibre test you must use isolation movements, obviously you want to test that specific individual muscle, rather than using multiple muscles, ie compound movements, eg Peck Deck V Bench Press.

BUT before you do testing with isolation movements you need to have spent a month or two with these in your routine, otherwise, the body has not “learned” how to do the movement. You may fail sooner rather than later as your body is not familar with the movement. Remember the first time you did something like shoulder press with dumbells? I bet the weights where all over the place (if heavy enough) but after a few weeks you probably where able to get many more reps out and control the movement - what happened? did you get HUGE, nope, your body just learned how to lift the weights.

So do a month or two of isolation movement so you are really testing your rate of fatigue when you test and don’t fail because you are not familiar with the movement.

Then have 2 weeks off.

Testing: one of the most popular ways developed (and much safer than using 1RM) is to pick a weight in an isolation exercise where you would fail at around 60s - you will have a rough idea of this weight from the last few months of using these movements.

Perform at a rep cadence of 5/5.

At failure, and i mean giving everything you’ve got - with excellent form and concentrating on trying to lift with that muscle alone - rest for exactly 60s.

And then repeat the movement until failure, again giving everything you’ve got - with excellent form and concentrating on tryng to lift with that muscle alone.

You are recording time under tension here, not reps!

Best to do testing on separate parts of body, ie on day1 do triceps, calfs and back.

Now if you compare the 2 sets results this is the story:

If the 2nd set is:
<=50% time of 1st set, then its PREDOMINATELY Fast twitch

50% < 75% of time of 1st set, then its PREDOMINATELY mixed fibre

75% of time of 1st set, then its PREDOMINATELY slow fibre

After adjusting your routine to your sprecific , individual fibre type , you should conduct another fibre test in 3-6 months.

Fibre test will point you in the right direction, a good idea of what your PREDOMINATE fibre type is for a specific muscle, there are so many variable but you will at least have a good indication.

Best Regards