Exercise Phys.- Muscle Fiber Types

[YellowJacket]

For those of you wishing to study an undergrad exercise physiology this will come in handy, as it will more than likely be the first thing you learn. This is characteristice of each of the 3 muscle fiber types....

Type 2A

*Anaerobic (Doesnt need oxygen, only nutrients)
*A powerful contraction
*Quick Fatigue
*Can last up to 4 minutes
*Produces lactic acid

Type 2B

*Very powerful contraction, more powerful than 2A
*Generates most force of any muscle fiber
*Very fast fatigue, faster than 2A
*Tires out in about 10 seconds
*Needs at least 3 full minutes to recover after being maxed out
* Uses phosphocreatine in muscles to work

Type 1

*Not very powerful
*Slow fatiguing
*Can last 4 or 5 hous or even longer
*Slow twitch fibers

I hope you guys can see the trend here.....the harder the contraction the quicker the fatigue, some people genetically have more of one muscle fiber type than another, theres no way to change this....work with what you have. Most pro bodybuilders (and b-boy and petefox ) Are blessed with Type 2B fibers which in weight training are the most desireable for mass.

*If you need anything clarified or want anything added let me know, I could include the process of how the muscle contracts if I have to .... or ask Whale, he knows as well if you're truly interested.

[snakeman458]

great info yj.
leave it to you for this stuff. after we get done in your class teach can i get a masters in ah ahahahah muscles. lol

[Blindfaith]

man its like taking KPE 163 all over again...i took that **** in my first year

[Kay]

Now if YJ can tell us which nerve afferents and nerve efferent innervate these fibres, i wouldn't have to go to school.

[Inzah Dude]

Which ones are fast twitch and which ones are slow twitch?

[YellowJacket]

Originally posted by Inzah Dude
Which ones are fast twitch and which ones are slow twitch?

Well for example.....fast twitch or white fibers is the soleus and slow twitch is the gastrocnemus (calf)...

So all you who have lagging calves.....try training the soleus....which lies underneath your calf.

[Matt T]

Isn't there a test (albeit rather innacurrate) to determine the balance of fast twitch (type II) to slow twitch (type I), that involves performing a set with 100% 1rm, then performing 80% 1rm to failure? If a person can only complete 3 or fewer reps, they would have a predominance of fast twitch and if they get higher than 3 they have a predominance of slow twitch muscle fibers.

[YellowJacket]

Originally posted by Matt T
Isn't there a test (albeit rather innacurrate) to determine the balance of fast twitch (type II) to slow twitch (type I), that involves performing a set with 100% 1rm, then performing 80% 1rm to failure? If a person can only complete 3 or fewer reps, they would have a predominance of fast twitch and if they get higher than 3 they have a predominance of slow twitch muscle fibers.

Yes, thats pretty much a myth these days however, theres no REAL way of determining how much of which you have other than a M.F.S Eval. Which is taking samples of muscle fiber from various muscles throughout the body and unless you're totally fascinated with this concept, its not worth the pain or the money.

[crazypete]

hard to get exact fibre typing as they can actually interchange somewhat. also there are actually 42 different isoforms not 3 in a continuum.

a better test is throwing medicine balls over your head, form charles poliquin's site:

Q. Could you please explain how to perform the Caber Toss test? I have read that it is a great test to determine the athletic potential of an athlete. How exactly is the test scored?

Thank you for your assistance!

Justin K

A. In order to do the 'Caber Toss' test you actually use three different weight shot putts. It is called the caber toss test due to the overhead delivery used by the athlete. The test should be done with the athlete standing with his/her back towards the landing area, preferably an outdoor grass area. The athlete should be standing on a solid surface such as concrete. He/she then cradles the shot with both hands, raises it overhead and then lowers the shot between the legs by bending at the waist and knees. From this position, the athlete forcefully extends ankles, knees, hips and finally flings the shot backwards, over head out into the landing area. It is acceptable to use the edge of a long jump board or a shot putt toe board as long as each throw is executed in exactly the same way.

To conduct actual testing, start with the heaviest shot and work towards the lighter one. After an appropriate warm-up, give the athlete 5 attempts with the heavy shot and then move to the middle weight shot, take 5 more attempts and then move to the lightest shot and repeat. Measure all throws from the point of take off. Because it is possible to really "hit a big one" with any of the shots, especially when dealing with a beginner, I would take an average of the 5 distances. If the athlete is like the majority of the population and is roughly a 50% mix of fast and slow twitch fibers, the difference between each of the shot distances with be roughly the same. For example, there may be a 4-5 foot difference between the heavy shot and the middle shot and a similar difference between the middle shot and the light one.

If you see a disproportional increase in the distances as the shot gets lighter, this is a good indicator for a fast-twitch fiber athlete. Those with slower fibers will not be able to generate much more speed over the same line of force no matter what the weight. The superior athletes, with the fastest fiber make-up will be able to generate considerably more force against the lighter loads. In general, the more skewed the distances are at the lighter end of the scale, the faster the athlete and hence, the more potential.

For a high school level athlete, I recommend using 8 pound, 12 pound and 16 pound shots, for more advanced populations, such as collegiate football players, 12 pound, 16 pound and 20 pound shots would be more appropriate. For females, drop all the weights 4 pound.

-- Art McDermott, CSCS

studies have been done on this and it is very accurate (and fun with all the stares we got in the gym). now it is true that some muscles may be slow and others fast (and this will vary from person to person), in general this test may be a good indicator.

afferent nerves are like sensory nerves carrying impulses to brain, efferent nerves are like motor nerves carrying impulses away from brain. this is a gross oversimplification. go to school kay, skipping anatomy class is not a good idea. i learned this the hard way last week as i had to memorize all the muscles, bones and nerves in 30 hours before my exam. somehow i got away with it, but i'm not going to push my luck again.

cheers, pete
yea exams are done

[khafra]

Good brief there, YJ--but by

Type 1

*Not very powerful
*Slow fatiguing
*Can last 4 or 5 hous or even longer
*Fast twitch fibers

You really meant *Slow twitch fibers, right?  Just don't want any of the easily impressionable types getting confuzzled.  And the type II fibers are, of course, the easiest to hypertrophy; but that alone indicates that the ratio, by volume, can be changed, if not the ratio by fiber count. This has been your weekly heckling, feel free to go about your business now.