Wednesday, June 19, 2013

Wondering About Watts On A Wednesday

Many of my friends and teammates train with devices that measure the wattage they generate while riding. I don’t have a way to measure my power output and usually I don’t feel like I’m missing anything, but today would have provided a textbook example of why wattage is such an effective way to gauge effort.

My ride was an out-and-back Eisenbahn State Trail time trial, of sorts, on my cyclocross bike. It was my first ride on the ’cross bike since May 28. On that occasion I did the same workout, reaching my turnaround point at Campbellsport in about 57 minutes and making the return trip in about 56 minutes. Today I used the Lap function of my Garmin to get more detailed splits: 53:53 out, 56:32 back. So, overall I was a little faster today and there’s nothing wrong with faster, but that’s not the interesting part of the story.

The interesting part of the story is that I worked far harder to average 16.5 mph on the return trip than I did to average 17.4 mph on the way out. How can that be, especially when you consider that the return trip is slightly downhill? The answer is wind: at a fairly constant 10 mph it pushed me to Campbellsport and then fought me every inch of the way home. I know I worked harder on the return trip but I can’t prove it to you. Speed, in this case, is not a reliable indicator of effort. Even heart rate, if I had bothered to record it, might not have fully explained the apparent drop-off in my performance after the turnaround.

But wattage never lies. It knows the difference between a guy who’s riding his guts out to go 30 mph on his own and a guy who’s soft-pedaling at 30 mph in the draft of the peloton. Without real power numbers from today’s ride I turned to a couple of online calculators. Using the stats that I do know, I estimated that the return trip, while slower, required about 22 percent more effort. That feels right. For what it’s worth, I spent a lot of time in the drops on the way home today, trying to reduce my aerodynamic profile.

Devices that measure power are becoming more affordable but I’m still not seriously tempted. Given the types of races for which I have been training over the last three seasons, the biggest bang for my buck continues to be weight loss. For me, power is less of a concern than power-to-weight. And in that equation, weight should be the easier factor to influence.

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