Fast and slow twitch muscle fibres

[nrage04]

interesting topic...

from what ive read (from future fit training booklets which are probably wrong lol) if there is any possibility changing one type to another it would only be in pre-teen years, in adults it wouldnt happen, or if it did not enough to make a difference.

[allthegoodnamesaregone]

thought I might as well put this in the mix, this is not my writing I'm just reposting

Might as well get these *****ers over here.

It was written around 2 years ago...

Muscle Fiber Displacement

While trying to figure out why some people thrive on very little exercise, while others don't seem to be able to gain muscle no matter how little or how much they go to the gym, I became obsessed with muscle fiber displacement. From previous education and experience, I knew that individuals varied in their number of red and white muscle fibers. For example, individuals that excelled at endurance sports (such as marathons) seemed to have a higher displacement of slow twitch (red/Type I-have great endurance, small, repair easily, used more for repetitious actions) muscle fibers, while individuals that had success in strength activities seemed to have fast twitch (or white/Type IIa or IIb-larger, tire quickly, take longer to repair, for explosive strength) muscle fibers. (Yes, I do believe that Type IIc exist, but for the sake of this article, I'm not going to discuss them). During my search for answers, I read a lot of information on this subject. I read medical journals, magazine articles, and the expert writings of Dr. Sal Arria, International Sports Sciences Association Founder. I started within-based on an experiment that Dr. Arria conducted, I decided to use myself for an experiment, and see what I could learn.

I believe that I am predominantly white fibered. Studies have shown that these individuals seem to be Type A---short tempered, high strung, etc (ME). Also, I seem to achieve great strength and size gains rather easily in the gym, another property of fast twitch muscles. During the peak of my strength building mesocycles, I squat around 80% of my 1RM for about 4-6. I have read on several occassions how individuals vary at 80% of their max-some can only do minimal reps (like me), while others can do 80% of their max up to 15 times! What does this say? Why do some people have a low tolerance to exercise but make incredible gains, while others can go all day, and still never see results?

The answer lies within muscle fiber displacement. The individuals that are able to do high reps with 80% of their one rep maximum seem to be predominantly slow twitch, or red fibered. These individuals have a great tolerance to exercise, can perform many reps, recover faster, and generally don't see huge muscular gains like their white fibered counterparts. On the other hand, white fibered individuals respond favorably to minimal exercise (preferably with heavy weight and low reps), need more time to recover, and don't have as much endurance as individuals with more red fibers.

Most of the information I found in medical journals and other references seem to state that most people have a 50/50 displacement of red and white fibers, while 55/45 either way could be considered a huge difference, and there are some very unique cases of up to 60/40. Based on the information supporting my theories, I believe that I am somewhere between 55/45 and 60/40 white fibered.

How can this information benefit you? Obviously, different types of fibers respond favorably to different types of exercise.

Below is a description of different tolerance levels, abilities to make gains, and what may work best for them. Hopefully, this will help you in developing your next training cycle, and assist you in achieving maximum gains!

Remember, these sets and reps are damn near all out work sets. Warmups aren't included, and you should be coming extremely close (if not reaching) failure here.

Slow Gainers (pre-dominantly red fiber) - Recover quickly. Can be ready to do lower body in 3 days after a light workout, 4 days after a medium, 5 days after a heavy workout. Upper body tends to be ready for another session in 2-4 days, based on the intensity of the session. Midsection, calves, and forearm work can be done every 1-3 days, based on intensity. Low capacity for serious growth. Red muscle fibers often benefit from 10 or more sets per muscle group, with rep counts of up to 12-16 (maybe as high as 15-20 in extreme cases).

Average Gainers (close to even red and white fiber count) - Upper Legs/Lower back usually need 4-6 days based on intensity, while the upper body needs 3-5 days before seeing more work. Midsection, forearms, and abs recover in 2-4 days.
Muscles that are even red and white (Type IIa) often benefit from 5-8 sets per muscle group, with rep counts of 8-12.

Fast Gainers (pre-dominantly white fiber) - Need more recovery time. Need 5-7 days between upper leg routines, and 4-6 days before working the same upper body part twice (of course, low end is after a light workout, and the high number is after a heavy workout). Midsection, calves, and forearms generally need about 3-5 days of recovery.
Type IIb fiber muscles often grow best from 4-6 sets per muscle group, with rep counts of 4-8.

Below are the 3 main types of muscle fibers, and a little about each.

Type I (Slow-Twitch Oxidative, SO)

Slow twitch, high oxidative metabolism capacity, highly fatigue resistant, with little capacity for exercise induced hypertrophy, high resistance to exercise induced structural damage. Training periods respond best to high repetition training (12-15 rep) with lighter weights and slow continuous tension movements. High density of mitochondria, which increases with aerobic endurance training. Small diameter, high capillary density, low glycogen content.

Type IIa (Fast-Twitch Oxidative-Glycolytic, FOG)

Fast twitch, oxidative-glycolytic metabolism, highly fatigue resistant, high capacity for exercise induced hypertrophy, moderate resistance to exercise induced structural damage. Important for sustained power endurance. During high intensity training, responds best to medium repetition training (8-12 reps) with moderate weight and fast concentric movements, but slow deliberate eccentric movements. During low intensity training sessions and during season, delete eccentric phase. Medium diameter, intermediate capillary density, intermediate glycogen content.

Type IIb (Fast-Twitch Glycolytic, FG)

Fast twitch, high capacity for glycolytic metabolism, low oxidative capacity, highly susceptible to fatigue, great capacity for exercise induced hypertrophy, great susceptibility to exercise induced damage. Generates explosive strength and power. During high intensity training responds best to explosive exercises (under 6 reps) with heavier weights, deliberate eccentric phase. During low intensity training and during season delete eccentric phase. Larger diameter, high glycogen content, low capillary density. These highly specialized cells appear to vanish during the first two weeks of high intensity weight training. They appear during periods of relative inactivity. It has been hypothesized that careful periodization and supplementation of one's training regimen may spare these cells, allowing them to fuse with surrounding satellite cells to create a much bigger cell. The new cell is often referred to as a Type IIc cell.


Using the above information and incorporating this, along with my Principles of Training Article, I hope that you are able to modify your training load, rest periods, and volume to help you achieve the greatest amount of gains in the least possible times. No two people are the same, and this is just a guideline (based on quite a bit of research.)


Here are some important points to consider after you read this.

1) I really didn't intend on this to be anything more than for muscular training. I used a marathon runner as an example as a person that has a higher red fiber count. Generally, that group of individuals are slow gainers, and a lot of it is caused by the type of training they do, and the rest is just their bodies (which came first, the chicken or the egg?)
With that being said, training for a marathon is a whole different animal, and this article isn't about that.

2) As far as bodybuilders that may be red fiber dominant-how many bodybuilders are there that are majority red fiber? Don't take that as me being a smart @$$, but they're rare. Probably about the same number of marathon runners that are white fiber. Even the lightweights are usually Type IIa, but are usually a little shorter. I know there are some Type I guys that compete, but again, it's not common. As far as the training styles go, I stated that the different classes of gainers "often benefit" from a particular rep/weight/set scheme.

Please let me express this point now: EVERYONE should employ EVERY different range of sets/reps/weight%/rep tempo throughout their training cycle to train every fiber to it's fullest potential.

Remember this-different muscle groups can have different displacements of muscle fibers! For example, someone's lats may be majority white fibered, but their calves may be majority red fibered. Also, every individual is different. Person A may have calves made up of mostly red fibers, while Person B's calves could be majority white fibered. THIS is GENETICS at play. You can't control that.

Don't take this to mean that fast gainers should ignore their red fibers, and vice versa. Quite the contrary. I use every different range, and so do my clients. BUT, I do stand by that fast gainers will experience a majority of their gains with the aforementioned scheme, as will average and slow gainers. Also, I didn't mean to make it sound like it was advantageous to be one fiber or the other. But the fact of the matter is that white fibered individuals tend to experience muscle gain at a more rapid pace than their red counterparts.

Oh yeah, if you re-post this, All Rights Reserved, and give me credit.

[hailtotheking]

I was told that there wasnt much evidence of fibre types actualy 'turning' into another type with training, and it is more likely that they simply begin to take on some of the characteristics required to the type of workload imposed on them, such as when fast twitch fibres are subjected to lower intensity endurance training, they begin to show more oxidative enzyme activity and greater mitochondria size. This change in characteristics takes quite some time of consistent exposure to a specific type of training, and is reversable.

[hailtotheking]

Purely from a hypetrophy perspective, i found the idea of training specific muscle groups according to their natural inclination to certain types of muscle fibres interesting.

For example, the leg muscles are used pretty much all the time in a low intensity, high endurance capacity when we are walking around, sitting down, standing up, etc. and thus naturally have a high number of Type 1 (slow twitch) fibres to suit them to this type of work. Therefore, instead of trying to get the type 1 fibres in the legs to 'convert' to larger type 2 fibres through heavy, low rep training to make them grow, we should train with low load high rep work (e.g. volume training) to stimulate the large number of type 1 fibres already present in the legs. Making all of these type 1 fibres grow would trigger a larger overall amount of hypetrophy, than if we try and make the smaller number of type 2 fibres grow, or try and make the type 1 convert to type 2 (which could take a long time, if at all possible)

[MartinM]

Hail - very good point. Its the same with the difference between the gastrocnemius and soleus. The soleus is predominantly slow twitch and is most active in seated calf raises so doing these with high reps is best and then using high load, low reps on standing calf riases to train the gastroc as it is mostly fast twitch

(that wasnt for your benefit Hail, just as an addage for others reading, wouldnt want to teach you to suck eggs )