What I Learned Today

My hotel presented me with the opportunity to collect some data about myself. On Monday, I went down to try out their exercise room and spent a while running on a treadmill (the first time I’ve ever used a hotel’s exercise room!). After a while I noticed that the shiny metal bars on the hand-rail actually were designed to measure and report your heartrate. After playing with this a little, of course I started to wonder how my body’s heartrate responded to the speed at which I was jogging.

So today when I went down for some exercise, I also took paper and pen with me. Of course what I wanted was for the machine to continuously record timestamps, speed, and heartrate and to deliver a printout to me at the end (or better, just email me the results). But no such luck, so I had to resort to recording it myself. This turned out to be more awkward than I anticipated; I wanted to record heartrate every 30 seconds, but the machine took 15 seconds just to calculate it, and then I had to fumble and write while jogging. Plus, especially at higher heartrates (or jogging speeds, not sure which was the problem), the machine would report garbage that masqueraded as a real heartrate (like suddenly dropping from 120 to 77 bpm). So in the end I had to do some data cleaning, which always makes me uneasy. But I only removed the obvious outliers and left the rest of the noise in.

The result is surprisingly sensible:

The heartrate values at about 8-15 minutes are not reliable; the machine kept reading low, and an independent test with my jugular and the wall clock suggested I was closer to 150 bpm at that point. (The 150 bpm point at 20 minutes was also from a hand-measurement.) But still, pretty cool! A bit of hysteresis, as you might expect. According to the machine, I burned 196 calories (but it didn’t ask for my weight or mass, so…) and traveled 1.9 miles. And I got to make a graph!