Constant comments on How I Lost 100 Pounds Using TDT - Less Wrong
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The answer from Body by Science is yes, very much so. I can drown you with quotes from the book if you like. Sadly, Amazon seems not to have fully implemented page numbers into the Kindle highlighting feature.
The overall argument as I understand it (my understanding may be faulty) is this:
1) Low intensity exercise does not do any part of you including your heart much good because it fails to significantly stimulate the kind of adaptation you want. You need to get your heart pumping hard if you want to trigger an adaptation, and low-intensity aerobics does not do that. High intensity aerobics does, but that is (3).
2) Long-duration furthermore potentially does your body much bad through wear and tear and accidents (don't forget probability of accident per second is multiplied by time to get total probability). As you'll see in the quotes, they claim (and have evidence for the claim, but you need to consult the actual book for full details) that exercising for long periods does not give you additional body-adapting benefits over and above exercising for short periods. So the long duration is (a) mostly wasted (except I suppose for direct calorie burning, but they emphasize that exercise is overrated as a calorie burner) and (b) potentially harmful.
3) High intensity (this can be high intensity aerobics such as the stationary cycle and it can also be high intensity resistance) does your body good (including your cardiovascular system, because your heart is working hard) by stimulating adaptation (for example, muscle building, but not only that). You can get much more information on the benefits of high intensity exercise (for all parts of you including your heart) if you google "high intensity interval training".
As a consequence of (1), (2), and (3), they recommend high intensity short duration exercise with a long rest period in between (for your body to recover and build).
They make the interesting additional point that steady-state activity (which is necessarily low-intensity long-duration exercise), while not benefiting you physiologically, creates the illusion of physiological adaptation when in fact what is adapting is essentially your nervous system. You learn to move your body more efficiently. So for example, if you walk for long periods, then as a result you will learn to walk for long periods (through economy of motion) but your learning will be limited to that one activity (because each activity has a different set of efficient motions which has to be learned anew).
Keep in mind that here I am only relaying the claims of the book's authors. Much of what they say makes sense to me but I have suspicions about some bits of it and I do not vouch for it.
Quotes (with some bit boldfaced by me):
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This claim seems almost absurd to me. What evidence is used in support of this? Are any studies cited?
No, that would give you the expected number of occurences (assuming independence, which is likely a bad assumption in this case). If the probability of injury in a second is P (given no previous accidents) and you exercise for T seconds, or until an accident occurs, then the probability of an accident occuring during the session is (1 - (1-P)^T), which is the probability of not having the conjunction of T accident free seconds.
I accept the technical correction. But for P close enough to zero, the probability remains nearly linear up to large T. So while you are technically correct I do not think you have refuted my statement as a very close approximation for a typical session lasting an hour or several. Given that, and given the relative difficulty of thinking about an exponential function, I prefer my formula for conveying the essential point in a comprehensible way.
It would be better to make the use of approximation explicit, and to specify the domain in which the approximation is a good one, like "don't forget probability of accident per second is multiplied by time to get approximate total probability, given small total probability".
No no, I am saying I erred outright. I simply used a heuristic and forgot it was a heuristic. You corrected me. That's why I had not identified it as an approximation initially. But that said, I find the correction to make the reader's task difficult, and my heuristic retains approximate validity, so I pointed that out in my reply.
Maybe that's why I gasp and feel like I'm dying every time I try to run, despite being in supposedly good shape. On the other hand, conditioning my body to run efficiently would be very useful in terms of transportation (using your own body to walk or run places is free!)
Can your muscles tell? I'm often sore the day after doing weights in the gym, but also the day after biking, or running, or playing tag with children (if I haven't done any of these things in a while.) I swam with one of my friends who doesn't swim regularly, and pushed her hard, and she was pretty sore the next day.
I presume they would say that your muscles can tell whether the exercise is low-intensity or high-intensity. However, the quote that you are replying to is specifically comparing high-intensity leg press to high-intensity stationary bike, i.e., two forms of high-intensity exercise which involve comparable amounts of work. I don't recall that they specifically addressed that comparison. My overall sense of it, based on all I've read (including online discussions), is that high-intensity is good either way - either stationary bike or resistance.