Monday, November 22, 2010

A power meter for Christmas?

If you are like most people, you probably look for new gadgets and when you see one that you like, you go out and buy it regardless of whether you need it or not. You also probably do not worry about whether it is helpful or practical. I suspect many people who end up with heart rate monitors and power meters fall into this category. I can certainly plead guilty in this matter. Perhaps my only redeeming value here is a vaguely scientifically motivated interest in human performance.

I certainly claimed such interest when I bought my first heart rate monitor 20 years ago. I was curious to see what it would reveal about my rides and my conditioning. To wit, I never really thought of it as a training device and hence I never bought any books entitled Racing with a Heart Rate Monitor or  Racing and Training with a Heart Rate Monitor. I simply set out to record my heart rate under various conditions and to interpret the results. I stayed away from Zones, remembering a previous bad experience in photography.

Pretty soon I discovered two things: 1. That I could accurately predict my heart rate in most conditions; and 2. That my heart rate did not contain much new information beyond what I already knew. These may sound similar but are in fact different. The first means I quickly learned to associate a number with a certain feeling of stress or perceived exertion. The second is no different from the statement I heard at the power clinic in San Diego, "Heart rate is always at a max for the entire duration of this workout." I found out that when I worked really hard, my heart rate was at maximum aerobic. When I went above I immediately felt like I wasn't going to be able to hold it, and sure enough, my heart rate went up and up and I had to stop.

More or less the same thing happened when I bought my first power meter. Only this time I was smart enough to wait for a sponsored team discount. I had learned my lesson: gadgets like these are fun, but they aren't much use so get them cheap.

While the gadgets do not have much information, there is a reason why coaches like them: they provide hard data as evidence that you followed the prescriptions. The data shows you worked out and that you worked out as prescribed. Most cyclists don't have enough computer skills to fake a power output file. But most cyclists can easily deceive a coach who relies on perceived exertion and coaches know that.

It is a steep price to pay for a device that does nothing more than provide evidence of acting in good faith, but that is not the coaches' problem. It is not even unique to coaching. The very same problem occurs in medicine and doctors too make you spend a lot of money to prove that you did as prescribed. Many tests have just the same value: they tell the doctor you followed orders.
A plot like this is often shown to demonstrate the superiority of a power meter. It is deceptive.

In that sense the heart rate monitor is no different.  You may ask, why do cycling coaches ignore it? They do, because they can measure power, a more objective data stream. A heart rate monitor tells you how hard you worked, but if you have a power meter and you know how hard a person can work, you don't need the heart rate monitor because you already know how hard they worked by looking at the power file. If you are a running coach however, then heart rate is your only option.

How about power profiles, quadrant analysis, etc? The short answer is, these things are interesting from a research perspective. Furthermore they can show you things that you may not have thought about or that are not immediately obvious -but not things you can't find out otherwise!

However, just like any diagnostic, knowing more does not mean you can do more. You may have heard this joke about doctors: Internists know everything but they can do nothing, surgeons don't know anything but they can do everything, psychiatrists don't known anything and they can't do anything, and finally pathologists know everything and can do everything but they are always 24 hrs late. Although the joke pokes fun at how little medicine can do for you, one thing is a key part: knowing about something does not mean you can fix it.

You may know your power profile, or look at your quadrant analysis and see issues. But there is little evidence you can correct them even with "special exercises." There is not even enough evidence to say you should correct what you perceive as deficits or that doing so is even beneficial. But like medicine, that has not stopped practitioners from trying hard.

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