muscle fiber proportions question

Darkmind · 12-01-2008, 03:16 PM

Would someone with say proportionally more fast twitch fibers have a higher rep max of a bench, squat, or deadlift than a person with proportionally more slow-twitch fibers even if their 3RM or 5RM on said exercises are the same?

Darkmind · 12-01-2008, 06:39 PM

I was doing my own research and I found this site. Muscle Fiber Types and Training

Basically a gym test is to find your 1RM of an exercise, and then bring it down to 80% of it, and do as many repititions you can. If less than 7 you have more than 50% fast-twitch, between 7 and 12 reps you're almost balanced on slow and fast. More than 12 and you have mostly slow-twitch.

EricLikesLifting · 12-01-2008, 07:02 PM

to your first post, yes they would.

for your second post, technique and form plays such a huge role in the number of reps that the 80% method would not really hold any water.

Frank.S · 12-02-2008, 02:09 AM

for your first post - not really.

the more trained someone is at a certain lift, typically the bigger leaps from 3/5rm to a 1rm.

All the tests to determine this are pretty worthless. Also the lift has to take into account, something like the deadlift for most is actually easier to rep out 80% of 1rm compared to a squat.

StuWard · 12-02-2008, 01:48 PM

Dr. Squat wrote an article that supports what you'r saying:
Finding The Ideal Training Split | Dr. Squat - Dr. Fred Hatfield

He uses White/red fibres instead of fast/slow in this article, and he's mainly looking at fast gainers vs slow gainers but the theory is the same. People with more fast twitch fibres have a relatively higher 1RM and fatique faster at the same % of 1RM. This doesn't make Frank and Eric wrong. With proper training, the ratio of fast twitch should increase over time and technique would still be a factor.

Frank.S · 12-03-2008, 01:04 AM

i dont think you can create fast twitch fibers? could be wrong.. although you can covert the fast to slow from what i understand.

EricLikesLifting · 12-03-2008, 07:25 AM

i'll give a quick muscle fiber physiology lesson because i love this stuff.

there are actually more than just type I/type II or slow/fast twitch fibers. it is more like this:

fast twitch:L IIX-->IIAX-->IIA
slow twich: IC-->I

Type IIX is what is considered to be the type of type II fiber for an individual who does not activate this fiber (a sedentary individual). With training, these fibers an change to a high quality fast twitch fiber, which is type IIA. You cannot change between type II and type I (aka fast and slow) or vice verse. Whatever distribution you genetically have of slow and fast twich fibers is what you are stuck with

The reason why a person with proportionally more fast twitch fibers have a higher rep max even if the 3-5RM is the same is complicated but come down to a simple principle. High force/power exercises (such as a 1RM) require the recruitement of high motor units (fast twitch fibers). Exercises that aren't as demanded don't require their recruitment. In this example, a 1RM is more demanding than a 5RM, so it will recruite more fast twitch fibers to perform than the latter. A person who has more fast twitch fibers to recruit will therefor be able to have a high 1RM than somebody who doesn't.

DanceDiva · 12-03-2008, 08:14 AM

Eric, just wanted to let you know I appreciated your layman's lesson in muscle fiber physiology.

Luna Sea · 12-03-2008, 08:43 AM

Interesting. I'm new to lifting, but I've never been able to crank out high reps. My first set is always my best when I go heavy. Then it's all downhill from there. Same thing with running. I can sprint like hell for 100 yards, but can't maintain steady state for 30 minutes before I get tired. No wonder I always hated cardio.

StuWard · 12-03-2008, 02:16 PM

Here's what Dr. Squat said:

"It was once believed that there was only 2 types of fast twitch fibers (IIA and IIB), recently however a more complete continuum has been established and it looks like this:
IIC -- IIAC -- IIA -- IIAb -- IIAB -- IIaB -- IIB
The more on the right of the spectrum a fiber is the higher is it's speed of contraction and contractile power and the lower it it's endurance.
The fibers on the left of the spectrum are less powerful but more enduring. Now, with strength training all the fibers have a tendency to "move to the right" (except the IIB, which are destroyed with prolonged training), that is they increase their speed and strength of contraction but become less enduring. With endurance training the opposite happens.
Of course these changes happen after prolonged systematic training, it is not an overnight thing.
There is a possibility that with a lot of aerobic training that IIC fibers can be converted into IC fibers (ST fibers spectrum IA -- IC), however IIC and IC fibers do seem to be very similar in their properties so it is not sure if that convertion happen.
POINT: In the weight room, go with the type II fibers! Always!"

I misspoke when I said "With proper training, the ratio of fast twitch should increase over time" but the effect is the same.

Darkmind · 12-03-2008, 02:34 PM

So from what I've read, for all muscle fibers, you never gain anymore but you can cause more hypertrophy in the certain slow and fast-twitch based on your training.

Whatever you're genetically determined for fast and slow-twitch fibers remain the same. However with certain training, let's say if you train doing heavy anaerobic training with fast-twitch fibers, the fast-twitch fibers will be trained more and cause more hypertrophy in those fast-twitch fibers. You'll have the same amount of fast and slow-twitch fibers, but the fast ones will have more hypertrophy.

BTW, from what I've read humans only have type I slow-twitch and type IIa and IIx fast-twitch. IIx is white anaerobic. Type IIb is in other animals like rodents for their jaw muscles which are the strongest type of muscle fibers.

EricLikesLifting · 12-03-2008, 04:21 PM

Darkmind, you are right that humans do not have the type IIb like animals do, but Type IIb and type IIx are very similar for the purpose of our discussion.

Be careful not to overemphasize the role genetics play. Think of genetics as a limitation at the elite level. If you have a high amount of type I fibers, you are not going to be able to be a elite level sprinter, powerlifter, or running back. Vice versa, if you have a high number of type II fibers (lucky you) you aren't going to be an elite marathon runner. By elite I mean competing on a professional level or in the Olympics or something. Because of the change that the fibers are able to make, and because of the role of technique and training, you can still enjoy any sport you want and be good at these sports. In my opinion, genetics become a factor when seperating the 'good' level athletes from the 'awesome' level athletes of a particular sport.

Darkmind · 12-03-2008, 05:57 PM

Quote:

Originally Posted by EricLikesLifting

Darkmind, you are right that humans do not have the type IIb like animals do, but Type IIb and type IIx are very similar for the purpose of our discussion.

Be careful not to overemphasize the role genetics play. Think of genetics as a limitation at the elite level. If you have a high amount of type I fibers, you are not going to be able to be a elite level sprinter, powerlifter, or running back. Vice versa, if you have a high number of type II fibers (lucky you) you aren't going to be an elite marathon runner. By elite I mean competing on a professional level or in the Olympics or something. Because of the change that the fibers are able to make, and because of the role of technique and training, you can still enjoy any sport you want and be good at these sports. In my opinion, genetics become a factor when seperating the 'good' level athletes from the 'awesome' level athletes of a particular sport.

This I know, but it's always good to clear it up for our readers

. I know I don't plan on being an elite level anything, lol. I just enjoy being strong. I don't plan on coming close to beating any world records

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