exercise ideas

[chhotii]

Spent some time reading up on the different types of motor units in muscles: slow-twitch, which are type I fibers innervated by type S neurons, and fast-twitch, which are type IIa or IIb fibers innervated by type FR or FF neurons. Realized that the exercise habits I've fallen into, for the most part, are just exercising the slow-twitch. Running, or more accurately, "jogging", around the pond at 5 mph, or walking when we're too hurt to jog; biking as transportation, but not at high intensity because the bike paths are infested with walkers; or, pooping out almost completely, and just doing the rowing machine at a plodding, thoughtful pace... yup, these are all slow-twitch. Not that these activities are bad. Plodding along does burn fat, because at that pace, the metabolism of fat can keep up with the rate at which energy is needed. (I think. The source for that bit of info is a web site, not one of the science books, so grain of salt.) Regardless of how burning fat might work, I'm sure I need to do these types of exercise, because if I don't exercise every day, my body will be too quick to conclude that I don't need the muscle any more and lose it, but if I crank up the intensity every day I'll over-train and hurt myself or just wear out.

But. Exercising the fast-twitch would be a good thing. Type II muscle fibers store a lot more glycogen. Thus, developing the fast-twitch muscles should increase the amount of glycogen my muscles store, which should have two nifty effects:

1) Insulin gives the message "hey everyone, soup's up, suck in the sugar!" when blood sugar is high. Fat tissue responds by sucking in the sugar and turning it into, well, fat. Tissues that store glycogen (liver and muscle) suck in the sugar and turn it into glycogen. So these are sort of competing. The more sugar the muscles want to suck in, the less the fat will get right away.

2) Even though I don't need a lot of calories, I can't go for very long without low blood sugar hitting and getting terribly, horribly hungry and weak, especially if I'm active. In contrast, I've noticed a funny thing: big strong guys who can down 3000 calories at a sitting can also sometimes go many hours without getting hungry (although when they do get hungry, get out of the way). I theorize that this difference is because I have less glycogen on hand, so I run out, and then boom! low-blood-sugar ickies. If I store more glycogen, then that's less likely to happen; and indeed, I've been feeling a lot better in this way since growing some muscle due to the "exercise every day" policy. The fewer the low-blood-sugar ickies incidents, the fewer workouts will be ruined by running out of energy, the fewer emergency muffins and french fries consumed, and the better my life overall.

I wish I could tell my body "I need the energy now not later, there is no famine in the future, really!" but it's been shaped by evolution to not believe me. Trying to up glycogen storage is all I can think of to change the now/later balance.

How to work, and thus hopefully hypertrophy, the fast-twitch:

The more force a muscle has to exert, the more motor units are engaged. Motor units are engaged in order of increasing neuronal size, so the S units, which tend to have small neurons, tend to be engaged if you just need a little force. Engaging the big-neuron FR and FF units only happens when you push a muscle to give its all. Thus, high-intensity. The fast-twitch units poop out really fast, so there is no point in sustaining the high intensity for very long. High-intensity, brief things that work the fast twitch would be

1) weight training, using a challenging amount of weight; and

2) interspersing some sprint intervals into running or other cardiovascular exercise. Sprint the end of a run, or if on a cardio machine, periodically crank up the resistance and push really hard.

The other suggestion I saw on-line is isometric exercise-- the theory being, if you hold a weight for a long time, the slow-twitch fibers that were doing the work fatigue, leaving the fast-twitch to do the work. But I don't believe it. Slow-twitch doesn't fatigue! The graphs in Fundamental Neuroscience show them just going on and on contracting at the same intensity. I think that the isometric proponents were trying to sell something.

Must do more weight training. Weights at home are too light. Going to gym is such a drag. Must ask Patrick how he likes his Bow-Flex knock-off.