Explanation of Slow-Twitch/Fast-Twitch muscles?

[jww13]

Are they completely DIFFERENT muscles, or is it the same muscle and how it's trained?
What's the advantage of slow-twitch and fast-twitch? How do you train for either?

Any help appreciated, thanks.

[PowerManDL]

These are two different types of fibers that are present in every muscle.

The difference is the ability to produce force, the speed of contraction, and ability to resist fatigue.

The FT fibers have high force output, high contraction speed, but also fatigue quickly.

The ST fibers are the exact opposite.

These are only general outlines, as there are several sub-categories of each type.

In general, the FT fibers are the ones that you want to target, as they have a greater ability to hypertrophy (due to their fatiguability).

[Hot Shot]

If you want maximum hypertrophy than you should train with both low reps and high reps to target both kind of fibers.Right?

[PowerManDL]

Reps high enough to target most of the ST fibers aren't practical.

For max hypertrophy, you want to train in a way that keeps the ratio of FT:ST high and that maximizes the size of the FT fibers.

[jww13]

Thanks Powerman.

Is it safe to say that each has its own purpose depending on what you do? (basketball, football, etc)

So FT would increase your vertical leap, increase running speed (?), etc?

ST would increase your endurance/stamina (ability to produce force for a longer time)?

Please correct these assumptions

[PowerManDL]

That's correct in a rough sense.

Though regarding how to train for sport, you're getting into more complicated matters--

The FT and ST fiber classifications are also largely independent of metabolic capacity. So you could potentially have an FT fiber that was highly oxidative, or an ST fiber that was glycolytic (rare).

Regarding training, its best to consider fiber composition to be a "black box"-- worry about the effect, not the mechanism providing it.

[mattcanning99]

both types of fibers are what all skeletal muscles are composed of (you can break down muscle fibers even further, into myofibrils; each myofibril is composed of smaller elements of contractile protein...)

slow - twitch muscle fibers are the red muscle fibers that contract slowly, weakly, and continually for long periods of time. generally speaking, slow - twitch fibers are developed by light, high(er) rep workouts.

fast - twitch muscle fibers are the white muscle fibers which contract quickly and powerfully, but not with great endurance. generally speaking, fast - twitch fibers are developed by heavy, low rep, explosive training.

recreational bodybuilding is usually in the 6 - 12 rep range to accomodate the ratios of slow twitch / fast twitch fibers in muscles...some stubborn muscles like the calves are said to have different ratios, and are trained very differently for some people (higher reps, sets etc).

are you looking to increase your vertical leap, etc, or were those just examples?

i suspect you are trying to find the best way to bodybuild, and if this is the case, post up your stats and goals (and body type), and i'll try to offer more specific info for you.

matt

[MonStar1023]

mattcanning99-
Good to see that you made it over here bro..

[syntekz]

Have lifetime runners been found to have more ST fibers in general than someone who wasn't a runner all their life? And the same for powerlifters?

[mattcanning99]

Originally posted by syntekz
Have lifetime runners been found to have more ST fibers in general than someone who wasn't a runner all their life? And the same for powerlifters?

thanks for the welcome monstar...this site will grow fast, im sure.

[Adam]

Syntekz, in supertraining i think there was a study done that showeed that elite distance runners had a higher % of st fibres then average people

[jww13]

Matt,

thanks for the explanation. My stats are:

17
5'-9
135 lbs.
don't know my bf, but I'm not fat at all, I'm just average

My goals are to pack on some muscle and just get bigger all around, cause I hate skinny arms and everything else. Anything you could recommend?

thanks again

[Alex.V]

Originally posted by getin bigger
Syntekz, in supertraining i think there was a study done that showeed that elite distance runners had a higher % of st fibres then average people

Yes... but does that show causality? Chicken and egg discussion, again.

[PowerManDL]

Not in that case.

But I've got sources showing it happen over the short term, like 12 weeks.

[the_hall]

If FT fibers contract "fast" and "explosive", then why is it better to train slow for maximum hypertrophy? Just wondering.

[PowerManDL]

Fast and explosive is relative.

However, a fast(er) concentric will recruit more of the high-end fibers than a slower movement will.

Doing an all-out ballistic set, like the speed work at Westside or an Olympic pull, will stress fibers that slower work can't.

Also, you have to consider that the different types of FT fibers have different contractile properties. The IIb/IIx fibers are the fastest of all, and may in fact be so fast that they *aren't* recruited by weight training of any type. The type IIa fibers, which generally speaking are more oxidative, are closer to the center of the spectrum.

Long, slower sets will stimulate them, and make them grow. But will also slow you down. This can translate into more mass, but a greater strength deficit.

[jww13]

Powerman, I probably didn't read your post correctly, but are you saying that weight training will slow you down?

As in, lower your quickness/dexterity or what?

[PowerManDL]

No, what I'm saying is that slow, longer-duration weight training will slow you down.

Explosive training or maximal (sets of 5 or less) training won't, but doing sets of 8+ with a slow cadence certainly can slow you down over time; granted, if you aren't in a performance sport you won't even notice it, but it can affect athletic capability if done long enough.

That's why (good) programs change during the course of the off-season and during the season itself.

[mattcanning99]

Originally posted by jww13
Matt,

thanks for the explanation. My stats are:

17
5'-9
135 lbs.
don't know my bf, but I'm not fat at all, I'm just average

My goals are to pack on some muscle and just get bigger all around, cause I hate skinny arms and everything else. Anything you could recommend?

thanks again

this works really well...ive been training for a little over a year now, and started out with exactly those stats, except i was a year older. i was 5'9, 135, at around 12% bf. this makes it especially easy for me to relate here. send me a PM with your email address, and i'll tell you what worked for me via email (it may be a bit long) - for the record i gained around 40 - 50 lbs in that time (since november 00). i have a feeling you could be making some awesome gains, and quickly.

[chris mason]

Originally posted by syntekz
Have lifetime runners been found to have more ST fibers in general than someone who wasn't a runner all their life? And the same for powerlifters?

Interesting question. Elite runners have been shown to have much higher (than non-trained people) percentages of ST fibers. Now, as Belial pointed out, does this mean they started out that way, or their training influenced their fiber type? From what I have read, there is evidence that training does effect fiber type. In other words, fibers can actually change type (well, sort of--read on). This becomes a bit more plausible when we look further into the situation. There is a fiber type which falls between pure FT and ST fibers. These fibers contract as quickly as FT fibers, but they have greater oxidative capacity (read endurance) than their pure FT counterparts. Untrained individuals have a mix of all 3 fiber types, interestingly enough they normally have a high percentage of FT fibers, nearly as high as sprinters. What is proposed to happen is that pure (type IIb) fibers can actually transition to the middle fibers mentioned above (IIa), assuming chronic endurance training is practiced. Of course, the problem with switching from a type II (fast twitch) fiber to a type I fiber is that the fiber type is determined by the nerve which controls it.

So, having said all of that, I personally think that it will be proven (eventually) that training can influence fiber type over a period of years, and that hyperplasia (an increase in the number of fibers) is possible. Does this mean that I think that genetics play no part in athletic endeavors, no, merely that I think training influences the body in more ways than most scientists currently think possible.

[syntekz]

Ya, I agree with you. But it's so hard, if not impossible, to be certain since every person is so much different than the other.

For scientists to figure out the number of ST/FT fibers a person has they have to do an autopsy, correct?

[chris mason]

That would be a biopsy .

[Avatar]

Originally posted by syntekz
For scientists to figure out the number of ST/FT fibers a person has they have to do an autopsy, correct?

eek
Lets kill that marathon runner just to check his ratio of FT:ST.

[syntekz]

LOL. Naw, I thought they had to wait until a person died to figure that sort of stuff out. Like when they die than they do all their tests or whatever.

Can they do a biopsy of a muscle when someone is still alive?

[chris mason]

Yes, although most athletes aren't keen on getting a chunk of their muscle tissue removed for study. That is one of the reasons you don't see as much research done in this particular area.