Occassional thoughts about orienteering

Sunday, February 22, 2009

A bit of laziness in yesterday's race


Here is a heart rate track from a bit of yesterday's race.

I cut off the control numbers. The course goes from left to right.

The heart rate curve shows that I was taking it fairly easy into and out of the control. I've drawn red marks that indicate the area where my heart rate was a bit low. My heart rate in this section was between about 162-165. That's an honest effort, but it is just a bit low for this race.

Taking it a bit slow into and out of a control isn't especially unusual. You might need to slow down to take a careful look at the map. You might ease off a bit as you look around for the features in the circle and the flag. You might leave a control a bit easy as you make some decisions about the next leg.

In this case, I was just lazy. The first red line on the heart rate track is at the edge of the field. I could see the control feature - a spur - from that point. I shouldn't have eased off. I just got lazy. Instead of keeping a steady effort, I rested a bit.

The problem with resting is that I have a tendency to then push a bit too hard. On the next leg, I pushed a bit too hard on the hill, got my heart rate over 170. I can't maintain that effort for long and I tend to struggle with my navigation when I push above 170 for long. I start having trouble keeping ahead with my map reading. Instead of reading the map and looking for features, I begin looking for features and then reading the map to see where I am. In tricky terrain, that won't work consistently.

With my current condition and on yesterday's course, I did best when I kept my heart rate between 165 and 170.

So, how did I do yesterday?

The graph below shows the portion of my race at different heart rates. I excluded the first leg (where my heart rate was a bit low after standing for a minute or two before starting). I excluded the last few hundred meters where running at a heart rate that I couldn't maintain doesn't matter - you don't need to navigate after you've crossed the finish line.

I spent about 20 percent of the time in the "lazy" zone; about 20 percent in the "too hard" zone; and the rest was about right. I don't really know if that's good or bad. I need to do this sort of analysis on some more races to get a good idea of what to expect. It seems ok. I'd hope to have a bit less in the "too hard" zone.

I suspect there's a relationship between the "lazy" and the "too hard" zones. As in the control I wrote about above. If I get "lazy" I tend to try to make it up by going "too hard."

It seems like there are a few things to do to make that histogram look a little better. If I'm doing more racing, I'll have a better sense of the right effort. If I do more training right around that sweet spot, maybe run a minute just above 170, then a minute just below.

Keep in mind that the sweet spot (at 170 bpm in yesterday's race) can shift around a bit day-to-day. It would, I think, vary with the weather and current fitness, and the demands of the terrain. With QuickRoute, you can figure out that sweet spot for the day by looking carefully at the relationship between pace and heart rate at different parts of the course.

If you're a complete QuickRoute geek, you can download the .qrt file for this race and play around with the data yourself. I put several .qrt files here.

Back to okansas.blogspot.com.

posted by Michael | 4:16 PM


I guess your HR depends a lot on the terrain. In technical terrain the histogram should shift to the left. In easy terrain it should get similar to running a 10K on the track - staying mostly around 170 (I would guess). By comparing to the pulse for a 10K on the track (or similar), you should be able to know more about how it should look?
I think that is generally true. There is some day-to-day variation (like when the weather is especially hot) and some terrain variation. My non-scientific feeling is that by looking at the QR track you can get a sense of the "too hard" zone and then back into the "lazy zone."

I took a quick look at my QR track from the first sprint race in Vancouver. In that race, the "too hard" heart rate looks to be quite high - around 177. The "lazy" h.r. looks to be under 170.

When I look at the histogram for that race, I spent about 2+ minutes "too hard" and nothing in the "lazy" zone. The "too hard" cost me a little time as I slowed to recover. A very rough guess is that I lots something like 20-30 seconds.

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