The Power of Power

If the image above means absolutely nothing to you, you are not alone. The modern bike racer would, however, say that you are behind the times, and are cutting yourself short on your training by not sitting at a computer analyzing your rides for about as much time as you spend actually riding. I would say I envy you, and that you should feel lucky for not being held accountable for every second of every ride you have ever done.

The above graph represents a bike ride I did this week, in terms of power, torque and all that other stuff vs. time. It was produced by a wonderful little device called a PowerTap, which I have recently begun using for all my training rides. This little computer consists of a special hub in the rear wheel of my bike that measures the force I am applying to the drivetrain, as well as my speed and pedaling rate. This data is then relayed wirelessly to a small unit on my handlebar which crunches all the numbers, and displays all sorts of important measurements while I ride. Then at the end of the day I download all the data to my laptop via a handy dandy USB cord and email it off to the trainer so he can check out what I've been up to (and crack the whip when I've been cutting those 10 min. intervals down to 9 minutes)

Now you may be wondering why anyone besides some sort of physicist would want to know how much power they are producing on a bike. You would then, of course, be placed in the category of people who are very far out of the know. Fear not, for I will fill you in enough to allow you to fit in just fine with any bike-geek friends you may have.

See, Power is defined as a rate of work over time. Work is defined as a force applied over a distance (force x distance). Thus, Power = (force x dist.) / time. The standard unit for power measurement is the Watt, which is equal to one Joule of work per second (a Joule equals one Newton of force applied over a Meter). So now when you hear someone say they put out 1000 watts yesterday, you will know that they did 1000 joules of work in just one second (for whatever the heck that is worth). So, for practical purposes, knowing how much wattage you are producing is very useful, because it is a direct measurement of how hard you are working. It is basically the best way to gauge one's effort on the bike for any kind of workout. For instance, coach may say "do six four-minute intervals at 420 watts". I would then go out and do my intervals, splitting time between staring down at the display to make sure I was keeping up this insane amount of wattage, and wishing I was doing anything else in the world but riding at 420 watts. Then when I am done, I could look at my data from the ride, with the purpose of quantifying the misery I put myself through, and seeing whether or not I actually kept up the wattage when I blacked out near the end of the interval.

In all seriousness, I love my PowerTap power meter, and I wouldn't train without it. It allows me to be very precise with my training, and gives me a sort of virtual training buddy to egg me on when I need it (or make me feel pathetic when I'm on a bad day). All I need to do is a periodical lab test to set where my wattage 'zones' fall (what wattages correspond to what levels of effort and how different wattages affect my body). I try not to get too into all the technicalities of training, but this is one device I wouldn't want to do without. Lucky for me, I will never have to be without a power measurement device this season, as all of team Trek - Livestrong's race wheels, including TT disk wheels, will have the PowerTap hub in them.

Now when I post graphs of training rides that I have done, or start talking about how awesome my wattage was yesterday, I will expect you all to be on board.