Types of muscle fiber
There are three major types of muscle fiber. These are classified by how fast they contract or twitch. These are called
Slow twitch (ST) which are characterized by having a good deal of myoglobin and mitochondria. They are weaker than the other types, but are made to work without tiring for a very long time. Your heart is the absolute winner for slow twitch fiber, since it never stops working. (It does rest between beats, which is why cardiovascualr training is good for it — your resting heart rate will drop, thereby giving your heart more of a break.) Other place you find slow twitch fibers are in the calf, neck and the quadriceps (thigh) muscle.
Fast twitch A (FTA) which has fairly short endurance lasting about 2 – 3 minutes and is designed to give great speed. This has larger nerves so it can fire faster and supplies about 5 times the amount of power that ST fibers do. This is dominant in the abs, triceps and hamstrings.
Fast twitch B (FTB) This is designed for bursts of power. It fatigues very quickly — within a few seconds. These have typically 10 times the strength of slow twitch fiber.
Both types of fast twitch fiber have much in common and things that apply to both will use the abbreviation of FT.
You were born with whatever mixture you were born with, and you cannot grow different fibers, just thicken the ones you’ve got. Normally, young athletes should be evaluated for various events to see exactly what mix they have. Very serious coaches will actually order a biopsie for their athlete’s muscle, though unless you’ve got lots of backing for that Olympic gold this is overkill. In any case, one person might have e.g., a bit more fast twitch fiber in his or her quadriceps than another and therefore have an edge as a sprinter. While you cannot change the composition, you can alter some of the properties, such as making fast twitch fiber grow more mitochondria and therefore increase its endurance.
Culinary aside: Chicken thighs are ST fiber and that is darker because of the myoglobin. Chicken breast meat is white becase it is fast twitch fiber. Chickens can’t fly, but when in danger can jump and get a short burst of height and speed from their wings. Ducks and other migratory foul have dark breast meat to help them fly tremendous distances.
The technical name for making something larger is hypertrophy which medically implies increasing the size of something without increasing the number of cells there. Muscles undergo hypertrophy but cancerous tumors do not (although they grow very large because the cells reproduce). This is in contrast to atrophy which refers to the whithering away of something (although you can certainly lose cells when something atrophies).
To increase muscle size most people concentrate on increasing their cross-sectional area. FT fibers have the greatest cross-section, so it makes sense that to get bigger, you want to use FT fibers (see below on how to gain strength and size). The actual mechanism runs as follows. You must increase the amount of contractile proteins, which are actin and myosin or you must increase the number and size of the myofibrils per fiber. This is normally done by overloading the muscles which breaks down the muscles. The body rebuilds the muscles stronger (just like breaking a bone, it gets stronger at the point of damage). The chief ways to overload are by having more resistance, increasing the number of repetitions per set or increasing the number of sets themselves.
You can also get increases in muscle size from non-muscle tissue, such as vascularization which is just growing more blood vessels (such as runner’s legs), increasing the amount of connective tissue or increasing stored nutrients and enzymes. This last one is why people take creatine supplements, since the muscles store this and swell nicely. This is a trick of body builders who pop these (they are one of the few supplements that are supposedly harmless and no I don’t take them nor ever have) for a few days before a competition so they look really pumped.
Gaining strength and size
So what is strength and how do I get it? Strength is determined by how strongly the muscles contract and how many fibers are contracted. A common misconception has it that muscles partially contract. This is untrue, A muscle fiber is either completely contracted or at rest. It is the number of fibers that can be varied. That’s pretty cool when you consider how much control that gives you, from being able to lightly touch something to blasting concrete (hey, I’m a martial artist, remember?)
What are the ways that one can build strength and size? Through resistance training. To do this you talk about your x-rep max written as xRM which simply means that you can lift a given load x times before being unable to continue. A 1RM is the absolute most you can lift exactly once. So the schemes are
- Strength lift 2 – 3 reps at 90% – 95% of your 1RM
- Size lift 5 – 8 reps of at 80% of your 1RM
- Both, but more size than strength lift 8 – 12 reps at 60% of your 1 RM
There are various schemes to vary repetitions aimed at maximizing gains, such as supersetting and pyramiding. A lot of ink is spilled over these in various magazines. Go read up on these. Bottom line from years of playing with them: They all work, just switch them once your body starts to adapt. Avoid anything that strikes you as just plain stupid though, since there are a lot of those. Any program that requires you to pop some sort of supplement should be avoided completely. Most supplements work if you follow their instructions, because their instructions consists of an entire training program. If you follow their instructions and just eat pop tarts (mind your calories!) you’ll see similar gains. This goes for the supplements that don’t kill you, that is.
A good set of references are the ‘Hard Gainer’ books by Stuart McRobert. He’s an older powerlifter and has an actual maintainable scheme for lifting long term. He is wonderfully no-nonsense. His book on form has been a big help for a lot of these exercises.
What a muscle runs on chiefly is ATP, which stands for adenosine triphosphate. The different types of muscle have different ways of making it an using it. There is enough ATP in your muscles at the start of activity to last for a couple of ST contractions or one FT contraction. After that, the body has to make more from whatever it has stored in the muscle, the method of which varies by fiber type.
- ST generates this from any of fat, protein or carbohydrate by a process of aerobic glycolysis, although the preferred way is to use the stored form of fat, triglycerides. The main factor here is that the body can keep this up for hours as long as it can get sufficient oxygen.
- FTA generates this via anaerobic glycolysis. This can be sustained for up to a few minutes. The basis of this is stored glycogen.
- FTB The final method uses creatine phosphate and can last only a few seconds. the basis for this too is stored glycogen.
Depending on the load, the body swaps off which it uses. So as an example,if you decide to sprint, the first few steps, using FTB fibers, are very powerful indeed, then these are exhausted and FTA fibers take over. After a couple of minutes this system is overtaxed and you slow down further using your ST fibers.
One other factor here is recovery time. While you cannot sustain many of these reactions, you can train to recover from the effort quicker, allowing you to continue. This is actually one thing trained in taiso.
Sequence of firing
Under a heavy load, the order that muscle fibers are conscripted is ST, FTA and finally, only if there is a high load, FTB. This is why strength training traditionally requires very high weights, almost at the limit of your ability to lift. However, more recent research has shown that if the motion is sufficiently speedy, all the fibers will get conscripted immediately. We use this fact in taiso to help rewire our central nervous system (evil laughter).