walkitout (walkitout) wrote,
walkitout
walkitout

How Not to Design a Fitness Test

There's a "One-Mile Fitness Calculator" over at:

http://www.americanheart.org/presenter.jhtml?identifier=3046243

I guess the first thing I want to say is, wow. I'm so happy that the American Heart Association perpetrated this, because I don't have any moral objection to picking on them. I have problems with them anyway.

If you exercise, and are in your, say, 30s, 40s or perhaps 50s, and you time yourself on a flat one mile course occasionally with a heart rate monitor, and you look at this chart's assessment of your performance, you may or may not agree with what the chart thinks of your performance. That's not, however, my problem with this chart (just so you don't think I'm complaining because it dissed me, I landed in the high fitness column -- altho that all by itself did make me a little suspicious).

Let's say someone did this fitness test, and it took them exactly 20 minutes to complete the course, and at the end, their heart rate was 125. If they were male, they are not even on the chart -- they are below the lowest fitness cutoff. If they were female, however, and under age 30, they were moderately fit. That doesn't make you scratch your head and go, hunh?

If they were female and _over_ age 30, any time worse than 19:46 drops them off the bottom of the chart. If they were female and over age 60, any time worse than _18 minutes_ drops them off the bottom of the chart. And if that doesn't make you go, holy wtf, maybe this will.

A woman who completes the course in 18 minutes flat in her 20s has a decent shot of qualifying for high fitness, based on heart rate at the end of the course. A woman who is 60 and takes so much as one second longer than 18 minutes to walk a mile falls off the bottom of the chart -- worse than the lowest fitness category for her age range.

What's going on here? I think they must have a formula that assumes that HR max descends with age -- a common assumption. In practice, measured HR max tends to decrease with age -- but blood pressure and weight tend to both increase with age, and the medical community has concluded that _that_ is just a bad sign all around. It's odd that HR max is not being treated similarly, as a bad sign. In this particular case, however, the assumption was made that percentage of HR max used to accomplish an objective physical goal was comparable across age categories. Thus, a 60 year old operating at HR Max (which a 60 year old completing this thing with a heart rate of 170 may well be doing) should be able to do as much objective physical work (traversing a flat mile on foot) as a 20 year old operating at HR Max (altho to be fair the 20 yo's HR Max isn't on the charts, which top out at 170, another bad sign). They really were aiming for 50-85% of HR Max. The problem arose when they collided an objective accomplishment (a flat mile) with a subjective accomplishment (effort exerted, through the proxy objective measurement of heart rate considered as a percentage of an imputed HR Max).

That didn't make sense? Here's another way to say it. On your 50th birthday, if you went out and ran your flat mile at exactly the same pace with exactly the same amount of exertion as you had on your 40th, 41st, etc. birthdays, you would be considered in _worse_ shape. Every year of your life, you have to get in _better_ shape, to be considered level. Anyone else in the world who could do at 50 what they had done at 40 would have regarded that as worthy of celebration.

The only way that isn't true is if HR Max decreases with age because we become more efficient (able to move that flat mile at a lower heart rate). Do _you_ believe that? Because I sure don't. And I don't know anyone else who thinks that either.

If you are going to age/gender correct a fitness test, let this be a lesson in how not to do it.

Someone is going to be tempted to say, but the test says "as quickly as you can". Well, if a 20 year old woman walking as quickly as she can only gets up to a heart rate of 110 and takes 20 minutes to finish the test, do you really want to say she is moderately fit, if you aren't prepared to say the same thing about a 60 year old?
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