Tuesday, May 17, 2011

A half marathon

I've been having a serious bit of trouble sleeping recently. I go to sleep at a decent hour but I wake up too early. And have trouble getting back to sleep. Maybe there are other factors involved, but being fairly desperate about the sleep issue, I decided to exhaust myself completely.

Being fit enough to run a marathon at any time was one of my baseline goals I've mentioned in a recent entry (see here). The training program for that was basically to run a couple of 10Ks a week, and occasionally substitute in a half marathon.

So I put my money where my mouth is. I went and tapped out a half marathon on the treadmill in the gym.

An hour before the run, I went and bought a new pair of Newton running shoes to replace the tired and worn existing pair that I have. Even on the treadmill, there is a lot of pounding to 13.2 miles (21.1 km). So I figured I could do with fresh shoes. They didn't have my size in stock, so I bought a lower end shoe in the right size. It's the Sir Isaac neutral guidance trainer. There is a psychologically significant difference in weight (247g vs. 316g for each shoe) between this and their race shoe.

(See picture of me checking my download in the changing room after the run towards the end of this entry to see the shoe.)

I usually run using my iPod 6g Nano with music and the Nike+ attachment to record the mileage. (See details in a previous blog entry here.) It has a special half marathon mode. Bit like the marathon mode, it counts up the miles completed until halfway, and then counts down the miles remaining in the second half.

The special mode gives a small psychological boost and provides a little extra motivation to complete the workout. Stopping the workout would mean aborting the electronic countdown. And that's not cool. Hang in there baby!

Here are the stats from the screen.

Yes, that an hour forty-five on the treadmill for nearly 1500 kcal burned. I also use the special Polar Wearlink HR strap to enable the 6g Nano to record my heart rate (HR).

For graphing, I used the basic technique described here (enable disk mode and drill down) to extract the raw data and plot it in Excel.

Step 1: Access raw XML data
  <extendedData dataType="distance" intervalType="time" intervalUnit="s" intervalValue="10">
    ..comma-delimited list of distance values in km..
  <extendedData dataType="speed" intervalType="time" intervalUnit="s" intervalValue="10">
    ..comma-delimited list of speed values in km/hr..
  <extendedData dataType="heartRate" intervalType="time" intervalUnit="s" intervalValue="10">
    ..comma-delimited list of HR values in bpm..

With the Polar Wearlink+ HR monitor active, HR is also recorded simultaneously with footpod data: in fact, the current values for three pieces of data - distance, speed and heart rate - are recorded by the 6g Nano every 10 seconds and stored in the xml file.

Step 2: Import data into Excel

Step 3: Scatter plot

Only real difference from the results shown in that earlier post is that I've used a scatter plot with HR and speed on different vertical axes (primary and secondary).

As you can see my HR steadily increased the whole way, despite sipping water every five minutes. I ended up downing two bottles of water (1 liter) and one gatorade (20 oz).

For those of you who are familiar with my blog, you can probably tell I err a bit towards the analytical side. I love instrumentation.

There is a discrepancy between the treadmill and the sensor I feel compelled to point out. In particular, speed-wise, I believe the Nike+ sensor gave me more credit than I deserved. I only set the treadmill speed to a rather wimpy 7.0 mph. But it gave me 12 km/hr credit. So either the treadmill is pessimistic or the Nike+ sensor is optimistic. As I said, I believe it's the latter case.

Well, I'm happy I managed to stay on the treadmill that long to complete the half marathon workout. But, as they say, the sixty-four thousand dollar question is: did I sleep well that night? Unfortunately, the answer was no.

Oh well, I guess I should trusted the treadmill not the sensor and run that extra kilometer more...

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