T Nation

Fast vs. Slow Muscle Fiber

Read an article on how to tell if a certain
muscle or muscle group is Fast twitch or slow twitch and how to tailor you training to the muscle types.

To test, you determine your 1RM and then load to 80% of your 1 RM and then see how many reps you can do. The lower the number of reps you can do at 80% 1 RM the more Fast twitch dominant that muscle is.

So, I decided to give it a try and was only able to do 4-5 reps at 80% of 1RM. Has anybody else tried this and is there anything to it or is it BS?

I think it could give you a general idea but there are a few problems with trying to judge it this way.

One is that different muscle groups on your body have different ratios of fast to slow twitch muscles, so doing this method with complex movements seems kind of fruitless. The bench, for instance, involves many different muscle groups.

Another problem is that this doesn’t take into account training age. As you continue to lift, your body gets more efficient/effective at lifting; with more experience you can use closer to 100% of your muscle fibers on a max effort lift.

So a powerlifter might be able to utilize 99% of his muscle fibers while a beginner may only be able to use 60%. Point being that this test would most likely result in overly slow twitch for a beginner and overly fast twitch for an expert.

No it’s true. A muscle with more fast twitch fibers will be able to handle heavy loads, but only for a short amount of time. The opposite holds true with slow twitch fiber.

Slow twitch are for endurance and a muscle with many slow twitch fibers will be able to lift close to maximal weight for a lot more reps then a fast twitch dominant muscle.

Very true

I think sometimes people get too hung up on it. It’s not important for bodybuilding, at any rate.

Agree. It’s not that important at all.
It is important if you are o-lifter and are trying to find wheter your quads are fast twitched so you perform let’s say a set of front squats with 80-85% of your max.

Athletes become more neurally efficient so this metod can be utilized only for begginer lifter/athlete.

And for testing like this, strict isolations via machines should be used to target the muscle and find out fiber ratio.

I don’t think you can say its not important at all. Maybe not very important in the grand scheme of things. But someone with mostly fast twitch fibers should train with lower reps for hypertrophy relative to someone with mostly slow twitch fibers.

I’d say you’re mostly fast twitch based on your 80% 1 RM. I can’t remember but CT mentioned the rep ranges somewhere…was it here or one of his book…can’t remember.

Anyway, generally train 4-8 Reps.
Versus somebody who has mixed fibers (8-12 reps). Versus a somebody with mostly slow twitch fibers (over 15 reps with 80% 1 RM) who would train more in the 12-15 rep range.

As mentioned before fiber type is muscle specific so you might want to do it for each major muscle group. Either that or use different rep ranges until you find one that work particularly good for you.

Poliquin mentions that soleus is primarily slow in most people (no surprise). Gastroc fast. Hamstrings fast. Quads slow. Can’t remember what his upper body recommendation are a the moment but you get the idea.

I haven’t bothered tested myself with for my 80% 1RM rep number, but found that lower rep ranges worked much better for me.

Theoretically it might sound good

But people tend to forget the closer to your 1RM the more muscle fibers will be recruited.

So while your calf for example might be 60 percent slow twitch (just an arbitrary number) if you just try to do high reps with lower weight (say 60% of max) the other 40% fast twitch wont be needed as the weight is light enough where just the slow twitch can handle it.

Now say you bump it up to 80-90% of max then you will need to start recruiting more of that other 40% fast twitch just to move the weight. And your slow twitch will be helping with moving this as well.

Not saying you shouldn’t ever do high reps necessarily but I think its well over emphasized by many with rep ranges. It’s simple… more weight = greater need for muscle adaptation.

I don’t think training 15+ reps even with a mainly slow twitch muscle will get much growth although it will get much more efficient at its utilization of oxygen and the manufacturing of ATP.

As you train a muscle the type IIB fibers start taking on IIA characteristics making them slightly more like type I fibers. That would mean the hypertrophy range would still be just as effective for bodybuilding. Right?

It’s mostly BS

[quote]Airtruth wrote:
It’s mostly BS[/quote]

I kind of agree. Recruiting as many motor units as possible is more important than training for specific fiber type make-up.

Exactly, IMHO CNS is heavily butchered so optimal would be to rotate te set-rep scheme with the same movement, and that is one way of recruiting as many motor units.

The only true way to tell is through a muscle biopsy. Short of that, there are too many vaiables for the lift test: training age, specific lift, technique (or lack thereof), and effort level of the individual, to name a few.

People read too much into the scientific studies and the training practices/ testimonials of elite strength coaches. Those are usually laboratory settings with untrained/ moderately trained individuals or (in the examples of the strength coaches) ELITE level athletes.

The easiest test is the “visual test.” Want to see a TRUE fast twitch animal? Tune in to the 100m sprint in the Olympics and then take a look in the mirror. Unless you look like those guys, chances are you fall into the average category. Not that you truly have average, below average, or above average genetics- it’s all ONE BIG CATEGORY.

Will working in lower rep ranges work for you? Of course- EVERYTHING WORKS (just some of the time). People tend to forget that the simple rules are more important: Lift with proper technique, get stronger on the main lifts, get enough rest, make sure your nutrition is in check, and BUST YOUR ASS when you train. Often times one (or more) of those elements is lacking and a lot of people go searching for “THE THING” thats going to push them to the next level- whether it be a special diet program, the HOTTEST new training program, new supplement, chemical enhancement, whatever.

I wouldn’t pay the fast vs slow twitch thing any more attention than is necessary- and that isn’t much. Screw what the rep test tells you- lift heavy for a while. Do low (3-6 reps) and high sets and see how your body reacts. Assuming you’re doing all the other stuff right, you should see some results. Worst case scenario: you learn a little more about how your body reacts to specific types of training and you become a better coach for the one athlete you really need to worry about- yourself.