I asked my Olympic weight lifting coach ,at least he will be my coach starting on Monday, if I could bike to burn some extra calories. His response was fascinating. He told me that since I am just starting out at Olympic weightlifting I could do any kind of exercise I wanted to help me loose weight. But once I get closer to my genetic max of lifting I'll need to stop doing any workouts that build slow twitch muscle tissue so that my body can build the most fast twitch muscles possible, particularly IIB, because they produce greater peak power and more force at higher velocities. Once to that point I'll still be able to bike, but will only be able to do short explosive interval training. (I highlighted the pertinent points in red below).
I wanted to find out more about the subject of the different types of muscle fibers and I found a great article on http://www.higher-faster-sports.com/fasttwitchmachine.html . I fact checked this by reading 3 or 4 articles on other web sites and they all seem to agree. This is the info I pulled off of the web page Higher-faster-sports.com:
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.
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.
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 subtype. 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 (IIB). 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
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 chinup, 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.
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 bodypart
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