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Power to the People

Posted by Bruce Hildenbrand on Apr 14, 2009 11:46:44 PM

I have been using my Saris Power Tap on my bike for the past several months and have learned a few things about training with a power meter which seemed good to share with my fellow cyclists.


As I said in my first posting when I had completed just a few rides with the Power Tap, I am not a rider who does a lot of structured workouts.  Yes, I do average over 300 miles a week, but all of my riding is what most would call long tempo rides.  I don't do intervals, but I will kick it a bit on the climbs.


So, I wasn't looking for a power meter to help me with my intervals. What I was looking for was something which could help me gage how to read what my body was telling me. By that, I mean it is reassuring to see that when my body is screaming pain, I am pushing 350+ watts up a climb. That says to me that my pain meter is pretty accurate.  If my body was screaming pain while I was generating 200 watts then something would be wrong.


Another thing that was really interesting to discover is how my body can mask a drop in effort after a hard effort.  By that I mean that when I am cranking up a hill at 350 watts, when the hill drops from say 8% to 4%, the number of watts I am generating in the same gear can drop as much as 100 watts.  However, there is a definite lag in how my body feels.  It takes me 30 seconds to a minute to re-adjust to the lower effort.  For those first 30 seconds to a minute, it feels like I am going just as hard at 4% as I was at 8%.


Sometimes my bulb doesn't shine too brightly. It took me a bit of cognitive activity to realize that, environmental conditions aside, it takes the same amount of energy to climb a hill whether you go fast or slow. It is just the law of physics. It takes a known amount of energy to raise a known weight a known height.Thank you Mr. Gravity. So, if you go harder, it just means that you will get to the top faster.


One thing that I really like about the Power Tap is that it has a setting for total energy expended during a ride. This is given in units of kilojoules, but in talking with noted power expert Dr. Allen Lim, you can convert kilojoules directly to calories because the human body is such an inefficient engine.


I live in a somewhat hilly area, Silicon Valley, so most of my rides have between 75 and 100 feet of climbing for every mile ridden. What I am finding is that I burn about 500-550 calories per hour of riding so in a typical seven hour ride in the Santa Cruz Mountains I burn about 4000 calories.


Granted, power meters are a bit on the expensive side and some of them require a new crank or bottom bracket, but I think there are some definite, tangible benefits.  I get a bit depressed when I am going hard at the end of a long ride and I can't seem to keep the power over 300 watts on that last long climb. But a couple of weeks ago, I had a big tailwind on one of my hillier rides.  I was going well up the climbs and would have attributed it to the tailwind, but my Power Tap told me that I was still generating good wattage meaning that I was still working hard and not just getting a push from behind.



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