Becoming A Fast Twitch Machine

Having warned you ahead of time that muscle typing is often overrated and less important then other factors, I still believe it is of significance. For more information about changing to a fast twitch muscle machine read on below.

Having warned you ahead of time that muscle typing is often overrated and less important then other factors, I still believe it is of significance for those who have everything dialed in.

What I mean is, with all things being equal it is usually advantageous to have a greater preponderance of fast twitch muscle fibers, particularly IIB, because they do produce greater peak power and more force at higher velocities.

The advantages of a certain fiber composition on performance in various sports is both obvious and well established—for example, marathon runners have 75% slow twitch fibers while sprinters have 75% fast twitch fiber (both IIA & B combined).

The ratio of your fiber type is a result of:

  1. What you were born with
  2. Transformation of slow to fast or fast to slow through training influence.

Transformable Fibers

If you were to look at a muscle biopsy you’d see both red and white along with various shades of each. The white being pure fast twitch and the red being pure slow twitch. Think of eating chicken, the white meat (breast) is fast twitch. The dark meat (legs and thigh) is slow twitch.

Chickens don't fly around very often yet when they do those muscles have to fire quicker, thus, their breast meat is fast twitch. Chickens walk around on their feet all day long thus their legs are slow twitch and better suited for endurance.

As mentioned before you can't take a completely red (pure endurance fiber) and turn it into a completely white (fast twitch) fiber but the intermediate fibers (IIA), which would be the various shades you see in a muscle biopsy are plastic and you can transform them into more of a red (slow twitch) version or more of a white (fast twitch) version.

You can also take a pure white fiber and make it a little redder, or take a pure red fiber and make it a little whiter.

Canadian scientists, Drs. J. Simoneau and C. Bouchard, have estimated that 40% of the variance of fiber type is due to environmental influences (i.e. exercise) while 45% is associated with genetic factors.

So that means you have about 40% control of your muscle fiber type, the other 45% you can do nothing about.

Real World Application

So how can you use this information and apply it in the real world? Well take someone who is say 50/50 fast vs slow-twitch. Over time and with proper training if he trains his nervous system to utilize 90% of all those available FT fibers and also increases the size of them he well then be able to outperform someone who has say an 80:20 fast to slow-twitch ratio.

In training you can accomplish this by focusing your training on strength, power, and speed dominant activities. By doing so you train your nervous system and all your muscle fibers to behave in more of a fast twitch manner. The reverse can also occur. For example, if one is blessed with a high % of FT fibers and starts marathon training the opposite will occur.

I haven't talked much about endurance training but let me mention that it causes a rapid fast to slow transformation (IIb to IIa and IIa to I) without any increases in strength or power, and thus should be minimized by those wishing to maximize speed and power.

Now, for those who really want to zero in on ultra fast twitch muscle conversion there is plenty of ammo out there to use.

First a little background.

Proficiency Vs Efficiency

There is a big difference between increased proficiency and increased efficiency. As mentioned in the previous article, a IIB to IIA conversion is more efficient when it comes to meeting metabolic demands. So if the body can get the job done with IIA then it will. Therefore, if you want your body to increase IIB content you need to make sure that the adaptive signals you're sending deem it necessary.

As an athlete you stress your fast twitch fibers a lot. Therefore, your body already perceives that it's a funny car and you're trying to run it on the highway. If your body needs more efficiency what do you think it's gonna do?

It's gonna try to find away to make the funny car either run at a low RPM or quit burning up so much gas! It's gonna make your engine more efficient if it can. How does it do that? One way it does that is by making your fast twitch IIB muscle fibers more endurance oriented.

Signal An Increase In IIB

So how do you get around this and what exactly does send a signal for an increase in IIB? Well, as mentioned in the earlier article, detraining or "sitting on your butt" is one. With detraining the muscular expression reverts back to its default "fight or flight" readiness. Yet another is hyperthyroidism or overeating.

Complete detraining is not much of an option because you lose more neural efficiency and muscle cross sectional size then can be made up for by any enhanced muscular sub type. Partial detraining and tapering may be an option and I'll get into that one in just a minute.

But what about training? Well, if one were to analyze the IIB fiber and MHC IIX expression he could easily come to the conclusion that this fiber type is made for dealing with simultaneous high forces and high speeds.

Some studies show IIa fibers to produce equal force at low velocities compared with IIb, so a rep done under typical strength training conditions (loads only as high as the concentric 1 RM and low velocities) can be adequately handled by IIa.

Maybe if the velocity component was increased, and force was maintained or increased, and performed at a volume low enough not to signal the need for more efficiency, we'd see an increase in IIB.

From here one could logically conclude that a training program incorporating movements with a premium on creating a lot of force at high velocities would preferentially induce more expression of these fibers.

Thus far, there are a few studies that have looked at this and found this hypothesis to be true. Training methods that duplicate a lot of the tasks seen in gymnasts do exactly this.

Exercises That Increase IIB Expression

These include:

Plyometrics utilizing loads, plyometrics, "drop and catch movements", jump squats, olympic lifts, drop jumps, depth jumps, speed squats, speed benches, reactive squats, as well as most ballistic type activities in which either high speeds, and or supramaximal forces are employed.

The force from a "drop and catch" type movement utilizing loads, or a plyometric type movement, exceeds that which is created with weight training. More importantly, the velocity component and the speed that force must be created is much greater.

Put into practice one could start from the top and perform a quick "drop and explode" in a chin-up, dip, squat, or olympic lifting movement.

The force created at the reversal from eccentric to concentric is great and must be applied extremely quickly or progress will not occur.

Another option would be to simply perform the drop and attempt to stabilize the load towards the bottom as quickly as possible. Yet another option would be to simply de-emphasize the lowering phase of a movement by letting the load come down fairly quickly yet still under control.

From here you'd then concentrate on an explosive positive phase. Fred Hatfield stated he used to train like this when he set his world record squat of 1014 lbs. and said it made him 15% stronger.

Short duration heavy isometrics (<10 seconds) in the weakest joint angle of a movement may also be useful to create strength gains without causing negative fast to slow conversions but the jury is still out here.

The one thing that should be avoided at all costs is any eccentric movement incorporating loads below 100% of 1RM done at low speeds such as done under typical bodybuilding protocols and/or normal regular paced repetitions.

This type of training induces the type of damage that signals the exact adaptations we're trying to avoid. With the aforementioned "high force" methods if the body wants to increase the true "proficiency" of the movement it has no choice but to create a more effective and faster muscle to do it with. TADA!

Here are a couple of studies providing evidence for the potential effectiveness of this training:

The percentage of type I slow twitch fibres in the FAST eccentric group decreased from 53.8 to 39.1%, while type IIb fibre percentage increased from 5.8 to 12.9%.

Although the increase may seem small what's more important is that you would normally see a ~15% decrease in IIB expression, therefore, the fast eccentric training could be deemed as 20% more effective for inducing fast muscle characteristics.

Sprint training would also seem like a viable option and would be when used at low enough volume as some studies demonstrate.

However, the volumes of training used by sprinters are often enough to signal the need for increased efficiency. For instance, sprinters run maximally about 3 days per week, they run endurance runs in between their speed days to stay lean and maintain conditioning, and they also lift weights at least 2 days per week in addition to plyos. Is it any wonder?

Stimulate Don't Annihilate

There is one caveat with this training and that is it must be prescribed in a dose so as to induce better proficiency without inducing efficiency. In other words, you don't want to be sending any signals to the body that would cause it to think it has to create adaptations just to better deal with the "volume" of training you're throwing at it.

You also wouldn't want to send a signal that the body is under a lot of stress or food shortage, thus dieting is a no no. The message you're sending needs to be loud and clear but "stimulating" not "annihilating". Whether you're creating the proper adaptations should be manifested in your results.

To illustrate, if you do highly intense plyometrics everyday you'll soon get to the point where you can do them practically all day without getting tired as your legs will "adapt" to handle the volume.

You'll probably see an immediate VJ increase as you become accustomed yet over time the magnitude of performance that you can demonstrate, or the maximum height you jump, will either stagnate or be negatively effected as the body adapts to the excessive volume. Therefore, performance should take precedence over junk volume.

To better describe this think of a movement like the jump rope. Say the goal is to perform 6 consecutive 3 minute rounds. Initially there is a learning period as one learns how to swing the rope and how to coordinate the feet and arms etc. After this, the main limiting factor is the ability of the feet and lower legs to tolerate the lactic acid induced from the repetitive jumps.

In someone who jump ropes chronically, (eg. 30 minutes 4-5 days per week), all things such as bodyweight and strength being equal, you will tend to see a decrease in maximal vertical jump as this adaptation sets in. The opposite is also true. Lower the volume down to 1 day of jump rope per week and you'll see an improvement in VJ as muscular efficiency lowers.

A Sample Cycle

If one wanted to put together a short mini-cycle strictly to focus on this one could set up something like this.


  • Fairly low volume—2x per week per body part
  • Progress at every session (If you're not improving then take an extra day of rest)
  • No lactic acid
  • No cardio (dynamic warm-ups, easy GPP, walking, and very easy intervals are OK)
  • Eat at least enough to maintain bodyweight **(some fat loss will be OK but once you have to substantially restrict food intake as opposed to simply engaging in better eating habits you're gonna reach a point where you start to shoot yourself in the foot)
  • Get plenty of sleep
  • Rest Intervals should be fairly long (2-5 minutes)
  • All movements should be performed at relatively high velocities

**If one wanted to go Balco and gain a lot of muscular bodyweight then "supplementation" and eating would be superior to performing extra bodybuilding training to induce exercise induced muscle damage (seriously). Drug users could also add in 12.5-25 mcg cytomel (thyroid) per day for enhanced effectiveness.

**Note: I am not advocating drug use but I feel it would be foolish not to mention it, especially considering the studies that demonstrate testosterone stimulates exercise independent muscle growth.

Users sitting on their butt doing absolutely nothing still gain nearly twice as much muscle as natural trainees who train their butt off. Now you know why there aren't many innocent olympians.

Some of the systematics previously written about by Mel Siff, DB Hammer/Jay Schroeder, Westside barbell, and others are ideal for this task, particularly if implemented along with the other guidelines. If you want you can easily make up your own, but here is a sample.

Lower Body I

  • Box Squat: 50-60% x 3-5
    (drop quickly to parallel with your butt off the box, sit back and explode up—use bands for increased effectiveness)
  • Jump Squat: (full) 30-40% x 3-5
    (drop into the bottom and immediately rebound out and jump)
  • Speed glute ham: or Dimel Deadlift: x 5-15
    (drop into the bottom of a glute ham and rebound up)

Dimel Deadlift
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Upper Body I

  • Drop and Catch Dip: x 5
    (Add enough additional load to make the movement challenging)

Drop And Catch Dip
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  • Speed Bench: 50-60% x 5
  • Drop and Catch Row: x 5 (70-80%)

Drop And Catch Row
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  • Explosive Row: x 5

Explosive Row
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Lower Body II

  • Depth Drop: into squat x 3
  • Depth Jump: x 3
  • 40 Yard Dash: x 3
  • Hang Snatch: (or underhand medicine ball toss) 80-85% x 3-5

Hang Snatch
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Underhand Medicine Ball Toss
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Upper Body II

  • Med Ball Chest Pass: x 5

Windows Media - 97kb
Real Player - 97kb
  • Upper Body Push-up Depth Drop: x 5

Upper Body Pushup Depth Drop
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  • Push Jerk (80-85%): x 3

Barbell Push Jerk
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  • Explosive Pull-up: x 5
  • Bicep Curl Barbell Throws: x 8-10

Bicep Curl Barbell Throws
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Volume would be based on feel and performance with generally 4-8 sets per exercise. One could train on a one day on / one day off format cycling through the 4 workouts or train on a Mon, Tues, Thurs, Fri format hitting each workout once per week.

The workout would last 4-6 weeks. At the conclusion of the phase most will find they are more explosive, faster, as well as stronger.

Note: Not to be rude but if you can't figure out a simple workout utilizing the above principles you probably aren't advanced enough to be worrying about this stuff anyway.

Clear Message

The above routine sends a clear and consistent message. It says "you need to adapt to creating force quickly both neurally and metabolically". It's also worth noting that high intensity EmS may have a positive effect in this regard but the jury is still out on that one.

One problem with the above plan is it obviously neglects other components of fitness needed for ongoing performance such as general conditioning, work capacity, and size.

Therefore, a plan that encompasses development of all the necessary motor qualities over a longer period of time would obviously be superior even if we can't always have everything perfect. In other words, with the long term plan it's necessary to take a step back and build up qualities that will enhance long term results.

The Long Term Plan

Before getting into the long term plan it's first necessary to talk about the muscular changes that occur with detraining. The paradox of IIB expression and training is that the overall volume and type of training needed by an athlete would and do deter it's display, yet paradoxically it's display would seem to be a huge benefit.

It turns out that the practice of tapering, unloading, and taking time off, also likely work by increasing IIB expression.

Type IIB Overshoot And Detraining

As stated before, with training, IIB fibers convert into the slower contracting IIA. What is really interesting is that with detraining or tapering there is a IIA to IIB overshoot conversion that occurs. That is, IIA fibers "reconvert" into IIB and that reconversion occurs at a greater than expected rate.

For instance, a group of athletes started out with 9.3% FTIIB muscle which decreased to 2.0% during a 3 month resistance training period. During this time there was a corresponding increase in IIA from 42.4% to 49.6%.

After a detraining period of 3 months, the amount of IIB reached values of 26%, which was nearly 3 times higher then before training was initiated. After this 3 month break training was reintroduced and there was less of a tendency to sacrifice IIB fibers.

Tapering And Unloading

This seems to explain the numerous performance records that are set when an individual comes back from a layoff. This also seems to suggest that if an athlete wishes to increase the relative amounts of fast muscle fibers a logical method would be to decrease the training load and allow the fastest fibres to express themselves a few weeks later.

This finding appears to lend some support to the practice of "tapering" that has been implemented for many years among strength and sprint athletes. Athletes in many sports will dramatically lower volume 7-14 days prior to a competition and find they get huge performance benefits from this. It is important to note that the above detraining study was carried out on sedentary subjects.

An athlete can most likely benefit from a much shorter or less dramatic detraining or tapering period as they already have the ability to adapt to demanding stimuli and for them a reduction in loading would mimic complete unloading in sedentary people. As is, some studies indicate a tendency towards more IIb expression after only 7-10 days of unloading.

On a personal note, in the past 13 years I have always trained a minimum of 5 days per week. I only had one period of time 6 years ago where I was forced to layoff from training for 6 months due to medical reasons. when I came back I had completely obliterated all previous performance bests within 3 months and those bests were maintained.

I always thought there was something to that and as long as the deconditioning isn't too extreme (a 50 lb gain in lard) I have observed the same in others providing they were chronically trained to begin with. I've also used the above training methods with regularity on a wide variety of athletes and the consistent results seem to confirm the validity of what I'm talking about here.

If one were to combine the above knowledge it would be fairly easy to design a longer training cycle to take advantage of this phenomenon.

  • Block I 4-6 weeks—GPP: Get In Shape (increase basic fitness, lower body fat if necessary)
  • Block II 7-12 weeks—Strength: 3 weeks high volume/1 week low—repeat 2-3 times
  • Block III 2 weeks—GPP—Recovery: Strength maintenance (Train with 1/2 the normal volume and engage in some sports like basketball, tennis, flag football for fun)
  • *Block IV 3-4 weeks—Shock loading: force drops, depth drops, strength maintenance (basically a repeat of the mini-cycle I outlined above)
  • *Block V 3-4 weeks—Shock loading: depth jumps (similar to the mini-cycle above but with more bodyweight movements, sprints and less barbell movements—A general guideline would be 120 ground contacts per week of lower body depth jump variations, 120 reps of upper body plyometric and medicine ball variations and 900 meters of speed work per week)
  • Block VI Unload—10 days: (Volume lowered 50%)

*= During blocks IV and V one would still perform enough basic strength training to maintain strength. One day per week per body part would suffice.


  1. Anything that improves "neural factors" will also generally improve the characteristics of FT expression, particularly in a beginner. These include any general strength and power/speed training methods.
  2. Beginners and intermediates should train generally and avoid overcomplicating things.
  3. An upper intermediate or advanced athlete can gain substantial short term results with a program as outlined earlier.
  4. You can't have everything all the time. In a long term setup one will have to take steps back in order to build up the necessary levels of conditioning, strength, and size. These attributes will then serve as a foundation when it does come time to really get into the focused speed/power training.

So there you have it. If your progress has stalled consider implementing a few of these ideas to your current plan. Let me know how your results unfold.

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