How fast could someone (maximum velocity) be with almost exclusively slow-twitch fibers?

Jeff Galloway had 96% ST. The only downside is that it leaves you with a predisposition to sell out later in life.

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Believe it or not the fibers doing the bulk of the work in any running are fast twitch.

Slow twitch fibers don't even have the capacity to contract fast enough to run. Its thought that what slow twitch fibers do in Distance and Middle Distance runs is store glycogen for working TypeIIA fibers, OR remove lactate from working Type IIA fibers.

So Type IIA fibers are distance fibers, and Type IIB fibers are sprinting fibers. Type IIA fibers do convert into Type IIB fibers with training, and Type IIB fibers can convert to IIA fibers with training.

If you were composed of entirely slow twitch fibers you would be completely nonathletic. You might be able to walk for extended periods but you would probably have some sort of muscular dystrophy or an extremely weak and feeble body. It would be hard to survive, you would almost certainly be disabled.

Type IIA fibers may be more inclined to offer greater potential at 200m-800m, simply because Type IIB fibers can only contract a few times, or a few strides. Obviously mid-d and distance athletes would have greater and greater mixes of non-active slow twitch that services working Type IIA fibers.

So Jumpers and short 60m specialists would be more endowed with Type IIB fibers.

100m specialists would have a mix of Type IIB (jump/start/acceleration) and Type IIA (everything else). This probably explains the trend of fast starters and poor finishers, and poor starters and great finishers dynamic in the 100m.

If someone was purely Type IIA they would still be very fast, but a slow starter. Michael Johnson comes to mind, and he ran 10.09 but when he was already moving at top velocity in his 200m record he split under 9 seconds on a tight curve, which is comparable to record 100m specialists.

So super fast twitch Type IIB fibers only improve starting and acceleration, and don't do much for a sprint when already moving.

Scientistic wrote:

Believe it or not the fibers doing the bulk of the work in any running are fast twitch.

Slow twitch fibers don't even have the capacity to contract fast enough to run. Its thought that what slow twitch fibers do in Distance and Middle Distance runs is store glycogen for working TypeIIA fibers, OR remove lactate from working Type IIA fibers.

link or meaningless.

Yup. The difference between fast and slow running is only that faster running recruits more fast fibers at once.

Elite distance runners are not predominantly slow-twitch. Look at Mo Farah with his 50 second final 400m at the end of a race—most people can't even sprint fast enough to keep pace with that for 50m. And Farah is slow twitch?

As for Galloway, well that test only measured one local area of fiber in one muscle. That result doesn't mean he has 90+% ft fiber all throughout his body.

Could you provide some references/links/further suggested readings? I have never heard that ST fibers were virtually not used at all other than as "complements" to glycolytic fibers. If so, I suppose support would have to be added, because it know for a fact that type I fibers are responsible for most instances of standing or sitting erect in mammals.

The only reason I am hesitant to believe what you are saying is that I remember a RW article citing Tom Schwartz ("Tinman") where he said that type ii fibers were not even recruited below a certain vo2 max threshold, up to which point type I fibers solely and completely powered the running.

SMJO wrote:

Jeff Galloway had 96% ST. The only downside is that it leaves you with a predisposition to sell out later in life.

This is hilarious.

SMJO wrote:

Jeff Galloway had 96% ST. The only downside is that it leaves you with a predisposition to sell out later in life.

This is hilarious.

First of all, the 3 main groupings of muscle fibers are generally thought of as more of a spectrum. Some fibers will be in between even these 3 categories complicating standard definitions. Nothing is set in stone when it comes to biology. Fibers can change type, display multi-fiber behavior, etc.

Slow twitch contract as much as 3 times slower than fast twitch so lets think about this logically. Marathoners (slow twitch dominant) have a cadence of around 140-200 steps per minute, while top end sprinters have a cadence of around 220-280 steps per minute, some of the fastest sprinters have a cadence above 300.

Obviously even a high slow twitch endowed marathoner is not sprinting (giving maximal effort) the entire way in a marathon so 140 steps per minute is far below maximal effort. Even the best marathoners are going to have a cadence rate around 180-200 steps per minute while sprinting at their maximal level.

Sprinters are not sprinting at twice the cadence rate of marathoners even though highly fast twitch dominant fibers contract 2-3 times faster than slow twitch fibers. The only plausible theory would be that slow twitch fibers do little of the actual propulsion in running (sprinting obviously, but also distance running).

The best marathoners are likely using another mechanism than slow twitch fibers to run so fast, they're just adapting their fast twitch fibers to twitch slower, while pure slow twitch fibers are providing circulation and nutrition duties supplying the working fibers with energy and removing or diluting waste products.

Purely slow twitch dominant athletes wouldn't be able to keep up with the best marathoners. Some of the stronger ones may be able to do ultras, but most high dominant slow twitch individuals would be non-athletic and would likely have health problems.

In muscle biopsy testing fiber % is determined by color- not twitch rate. Twitch rate is the real determination of fiber type, as true slow twitch fibers will likely never be able to take on fast twitch characteristics. Slow twitch fibers have different innervation potentials, on top of differing energy streams (fat/low glycolytic), and differing capillary density (color differences).

The problem with our definitions is that we're not thinking about how fibers transform and the simple tests that determined fiber type aren't accurate. Color alone does not determine fiber type.

When some endurance athlete says they're 'slow twitch' what likely happened is their fast Type IIA fibers took on slow twitch characteristics (turned red) and the simple biopsy test assumed the fiber was slow twitch, when in reality it was originally a fast twitch fiber, and could turn back into a fast twitch fiber after time off or strength/speed training.

Interesting to note is that 1/3 of endurance athletes are 'coded' for fast twitch the same as sprinters, while nearly 3/4 of all endurance Olympians are coded the same as Sprinters for the ACTN3 gene.

What this means is that likely Elite Sprinter or Elite Distance runner share the same ACTN3 Fast twitch genes, while those without are limited to purely endurance activities and even then they are probably not champions.

So how could so many endurance athletes be coded the same as sprinters, yet perform so well at endurance races? The answer is that their muscle fibers transformed and previous testing simply missed this transformation because it was looking at fiber color and not twitch rate.

Possible conclusion: Fast twitch fibers do the heavy lifting, even for distance runners. True slow twitch fibers are simply there to support the working fast twitch fibers. Someone with pure slow twitch wouldn't even be able to run, and would probably be too weak to even stand.

Contractions are much faster in all types than what you are talking about. One contraction is not equal to one stride. That is not how it works. It's a coordinated effort of multiple movements between multiple muscles.

Scientistic wrote:

http://kohlmanngen677s13.weebly.com/

that's the best you've got?

Name: Kristin Lee Kohlmann

Age:22

Major: Genetics with a certificate in Global Health

"I will be graduating from the UW in a few weeks"

again, links or quack. Which is it?

so 90% of all athletes of any event have the RR or RX profile for the ACTN3 (fast twitch) gene.

Getting Gene tested then is almost a waste of money, as nearly every random person walking on the street is encoded the same elite athletes. This shows how truly important training and dedication to training really is.

There is no 'sports gene'. There is no elite genetic profile if 90% of the population has it. Thats scientific garbage the same as muscle biopsies that counted two colors in fibers under a microscope Its in nearly everyone. Most people are fast twitch dominant, and fast twitch fibers do most of the work in running.

Tortoisethehare wrote:

Contractions are much faster in all types than what you are talking about. One contraction is not equal to one stride. That is not how it works. It's a coordinated effort of multiple movements between multiple muscles.

Obviously, but if you had a study of two identically proportioned individuals, with the exact same muscle sizes, with the exact same output ratios, (all of this would be nearly impossible btw) and the only difference was fast twitch/slow twitch you would have even greater differences due to the nature of locomotion.

That is a pure fast twitched runner would actually be going at an even greater rate than the twitch rate difference due to the effect of the running gait. A slow twitched runner would be even slower than the observed. Thus due to the running gait the twitch rate would be magnified not lessened as you say.

Fast twitch does nearly all the work hypothesis + observed:

SPRINTER- 300 SPM

MARATHONER- 200 SPM

Slow twitch actually does the distance work or slows the Sprinter down:

SPRINTER- 600 SPM (limbs sheered off or every muscle tears)

MARATHONER- 140-200 SPM (observed)

or breaking all the observations of all the running ever in human history:

SPRINTER- 300 SPM (observed)

MARATHONER- 80-100 SPM

The only people observed to move that slowly are the very slow, almost sickly people we've seen on our teams or in hospitals, or the elderly, etc. They're predominantly slow twitch and can hardly move, aren't athletic at all. Leg turnover actually does indicate to some degree twitch rate, and gene tests, observations, and more modern techniques of determining fiber type all support this general theory.

Pure slow twitch fibers do almost nothing for running. The fewer you have, likely the better you'd be as an athlete in any event except an ultramarathon or maybe a race walk.

Bad Wiggy, what agenda do you have? Because you surely have one.

What this girl did is research, on the ratios ACTN3 in populations.

You're giving a very simplistic view based on her, when the design of the Gene test was done by thousands of people over many years, and nearly all of those people have PHD's in the field and are older than 22.

So give a complete picture in your 'rebuttal' and stop counting the red fibers after you butchered someone's leg for a couple bucks.

And there's 7 links in her references. I'm sure you can find hundreds of sources in those links as well.

Tortoisethehare wrote:

... It seems reasonable to think that most people could be almost as fast purely on oxidative metabolism as on phosphagenic and lactate ...

Almost as fast = 2nd place.