The Fugue

I’m still swimming. This may be the longest I’ve stuck with any exercise program (excluding things thrust upon me like basketball practice or getting out of bed). Naturally, being the technical sort that I am, I want to make sure I’m using this exercise time efficiently, so I picked up Total Heart Rate Training by Joe Friel at the bookstore (and put it down before I left—reading it over several visits while my son played with the Thomas trains). This is an informative book with lots of information, but it’s not for the weak of heart—literally or figuratively. The book is written by and for obsessive-compulsive athletes (the most common variety is known as triathlete). You have to be absolutely bonkers to follow this book religiously. But it can be useful to the thinking fitness swimmer, with a grain of salt.

The first problem with this book is precision. Not a lack thereof but an overabundance and misunderstanding of it. In physics, or any practical math, you can get in trouble by giving more significant digits than your measurements warrant. You can fool yourself and others into thinking you have more precision than you do, which leads people to jump to incorrect conclusions and make silly and/or dangerous decisions. Heart rate monitors will give you absurdly accurate heart rate measurements. But I posit that you can’t measure how that maps to your body’s metabolism (the zones) with anywhere near that accuracy, at least not while exercising. What’s more, as a swimmer anyway, you can only check the monitor during rests at the end of the pool, where it’s just as convenient to take your pulse with the pace clock (it takes 6 seconds to get ±5 bpm). The heart rate charts in the appencides are what really give it away, though. Running, Biking, Swimming, etc. each have their own 2-page chart with some 60-odd entries on where the zones begin and end, to the nearest bpm. If that doesn’t sound absurd by itself, take a look at this graph I made from the swimming chart:

They say a picture is worth a thousand words. Notice how the relationship is almost completely linear. I’m no exercise scientist, but how much do you want to bet the body is not so perfectly conformant? I bet it varies depending on the day, conditions, what you ate, etc. There might even be some nonlinearities. So we have a chart with a bunch of numbers and no graph, that is overly precise.

That wouldn’t be so bad on its own, but the author actively disparages traditional measures and formulas for being too inaccurate, when of course the reason they are too inaccurate is that they are too precise. The most obvious example is that your maximum heart rate is 220 minus your age. This gives you a bpm, but really it’s only good to within 10 or 20 bpm. He rightly says that this is not accurate. But he says it’s as likely to be way wrong as not, because it’s a statistical measurement. i.e. it’s a bell curve. Hello, 95% confidence of being within 2 standard deviations hardly qualifies as “as likely as not” to be outside. If he really wanted to convince me he would have stated the confidence intervals and said just how far off from that number you are likely to be. Then he would have compared that error with the error in pinpointing the zones in exercise. I think we’d find that maximum heart rate, while not perfect, isn’t as bad as all that.

While being absurdly precise and complicated (to the delight of obsessive compulsive triathletes everywhere), this book is also somewhat lacking in rigor and logic. Besides the examples above, there’s an issue I blogged about previously: the so-called fat-burning zone. As you may recall, the fact is that your body burns more fat per calorie when in an aerobic metabolism. This leads people to call the aerobic zone the fat-burning zone. People get lazy and forget to put in the disclaimer that you have to work longer to burn as many calories, which leads to confusion. Trainers and self-righteous OC athletes retaliate by pointing out that you burn more calories per time unit by working out harder—up into anaerobic, and so “the fat-burning zone is a myth”. Well it’s not a myth, it’s perfectly valid if you’re willing to work out longer. Instead of elucidating the topic with clarity and stating both sides of the issue without bias, the author falls squarely, if not extremely, on the myth side.

Still, there is a lot of good information in here on how the body works, what’s going on in the various zones, in which zones you can best spend your exercise time in order to achieve your goals (the information for a fitness swimmer is in there, if a bit hidden behind the triathlete-like goals). Numbers that are useful if you take into account that they are too precise, etc.

I’ll give you an oversimplified summary of what I learned in the book. Referring to that graph above (by the way, I had no control on which colors were used—they’re just GNUPlot’s default colors), notice that the x axis is the lactate threshold. He claims that LT is a better base point than maximum heart rate, because you can directly observe it without killing yourself. Sounds good to me.

At the border of zones 1 and 2, aerobic respiration accounts for almost all of the energy produced. Aerobic respiration primarily uses fat and is much more efficient, but less powerful, than anaerobic respiration. If you’re fit you can stay in zone 2 all day long.

At the border of zones 4 and 5, enough anaerobic respiration is happening that various easily-observable changes occur, and the exercise benefits change too (especially those related to heart). Oversimply put, training above LT will train for speed in shorter (non-endurance) races, and also do various good things for your heart.

At the border of zones 5b and 5c, almost no aerobic respiration is occuring—it’s all anaerobic. This is because you’re demanding more power than aerobic respiration can keep up with. Anaerobic respiration is done not from fat stores but from stuff stored in the muscles themselves (for immediate access and powerful energy). There’s only so much of this fuel, so you run out of steam quickly above LT, but especially up here. This is sprinting stuff, and you can rarely keep it up long enough to even measure heart rates much into zone 5c.

For me, I am going to aim at increasing my LT and staying mostly in zones 2 and 4, (apparently zone 3 is a waste—little more benefit than zone 2 but requiring a lot more recovery) but doing interval training shooting up into the above-LT zones, mostly for the heart benefits. I figure that will meet my goals best, i.e. I will enjoy the exercise more and not leave the pool exhausted, I will burn more fat per calorie, and the interval training will give me enough edge to keep things interesting and improve my cardiovascular health (not to mention increase LT—doing intervals with sufficient rest to “cycle” the heart rate from low to high and back to low is one good way to do that). And I’m going to do it by taking my pulse with the pace clock periodically, and paying attention to how my body feels and how hard I’m breathing.

Of course, the most important thing is to keep on just doing it, and that’s going well because I’m enjoying learning the Total Immersion swimming method, and I’m finaly getting into the more interesting drills. It won’t be too long until I graduate to swimming again, at which point I’ll review that book. I’m looking forward to seeing if I can swim a 500m in under 10 minutes with ease. That’s something I had to do regularly as a lifeguard and even though I was more fit then (or at least less fat) I always struggled with swimming 500m non-stop, and my times were usually 10-12 minutes. If I can swim a 500m with ease in under 10 minutes in my current shape, it will be a testament to the TI method. Stay tuned!

My Swimming Book makes the following claim: if you work out at lower (but still aerobic) intensity you burn more fat per calorie than if you work out at higher intensities. Note that it says per calorie, which means you have to work out longer. A rough guideline is to go the same distance as you would at the higher intensity.

Unfortunately he doesn't give any references and no numbers or graphs. One is left wanting more information. But if you try to google that topic you will find two camps yelling at each other from across a great chasm.

Group 1 says keep your heart rate down in the fat-burning zone. Group 2 says group 1 is a bunch of fools and that although the ratio may be higher you burn more fat by working at a higher intensity because you burn more calories. The amusing thing is that neither side ever cites any references whatsoever, nor gives any concrete numbers. Neither side gives due diligence to pointing out that you can burn the same amount of fat either by working easy-but-long or hard-but-fast. Calorie burn rate (time) and intensity are a tradeoff, but to the two groups there is no compromise.

Finally I found a white paper with solid logic and numbers and graphs. (Still not enough references, but at least there are some.) Check out the graph on page 8 which confirms what I suspected: there is a point of diminishing returns. Choosing Zone 2 over Zone 1 is a no brainer. Choosing Zone 3 over Zone 2 looks marginally smart. Choosing Zone 4 over Zone 3 (when fat loss is the only consideration) is silly—you use more calories to burn the same amount of fat. Of course there are lots of reasons to go into Zones 3 and 4, like training for races, cardiovascular health, building more muscle, and burning off the extra helping you had at breakfast. But if you're looking to burn fat efficiently, It looks like roughly 70% of maximum heart rate (220 minus your age, as an estimate) is the point of diminishing returns, and a good aim.

Now, that said, there is a lot of variance in the fat burning range. In fact, the whole point of that white paper is to teach you how to increase that anaerobic threshhold so that you can burn a higher fat percentage at higher intensities, effectively raising that point of diminishing returns and allowing you to burn more fat per minute. This is another thing the TI book said you could do but didn't give enough details for my taste.

Of course, let it not be forgotten that the thing that makes the most difference is actually getting up off your duff and into the pool.