Last December I bought a used Saris "CycleOps "PowerTap" power meter kit that I saw on Craigslist.org. Basically it's a bicycle-wheel hub that has an internal Watts meter. That is, it measures how much power I'm sending to the rear wheel, in Watts. Neat device that is helpful in training, and also allows you to save each ride's data to your PC for detailed analysis and record-keeping.
Car engines are measured in horsepower, but we mere humans put out only between 0.1 to 1.6 horespower, so we measure it in the more impressive-sounding Watts equivalent: 75W to 1200W. (That is my typical power output range, by the way, from easy cruising to full sprint.) The PowerTap includes a cyclometer (bicycle computer; the kit's CPU) with an LCD display that mounts on the handlebars, so you can constantly check your power output, plus the usual speed, time, etc., and also heart-rate. This picture shows a newer wireless unit; mine is the older wired type.
Actually, I have two older PowerTaps now: The first PowerTap I bought (black CPU with serial dock) had a semi-faulty CPU that dropped the data from the hub about 30-40% of the time, and also never worked with the older serial dock connecting it to my PC (it didn't work with a newer USB dock either). I ended up buying a second used full PowerTap kit (newer yellow CPU with USB dock). I tried to save money, oh well, but the good news is that I now have two PowerTap wheels and wiring harnesses so I can keep one on my 10-speed training bike and the other on my 9-speed commuter bike. Still, I may sell the extra wheel, HR chest-strap and wiring harness (the semi-faulty CPU and the serial dock are included free!), so if you want a slightly used PowerTap hub on a Bontrager Aero wheel, drop me a line using the "comments" link below.
Without a power meter you have to rely on carefully-staged, timed rides to measure your training progress. You might, say, use Old La Honda Road in Woodside to measure your speed during 20-minute intervals (well, for me, as that's about how long it takes me to climb that hill). Ride that several times a year, using the same bike and other equipment, and keep records, and then see if you are getting faster or slower. Trouble is, things like wind, temperature, road conditions, barometric pressure, tires, chain lubrication etc. all add up to create substantial variables that can overwhelm your actual training results. I know this from personal experience! The PowerTap, on the other hand, reads accurately no matter what. Power is power. And you don't have to test on one specific section of road to measure your progress. Just ride as hard as you can for whatever interval you want to compare, on whatever road suits you at the time. 20 minutes at full power is always the same regardless of the conditions... well, sort of: Your body still reacts to your diet, your form, etc., so power still varies accordingly. But at least you eliminate the outside variables so you can compare how your body is progressing.
So, how has this PowerTap changed my life? Well, in several ways:
It has helped me refine my pacing during intervals:
That is, I can use the PowerTap CPU's display to read my current power, and I just ride at the correct power I am capable of for a given interval length. I now know what my power output should be for various interval lengths between 5 seconds to 20 minutes and even longer. This is a huge help in training because I have discovered that I was riding too hard in my longer intervals, but not hard enough in my shorter intervals. Also, I have discovered that I was riding too fast at the beginnings of my intervals, then fading toward the ends. Using my heart-rate monitor for pacing was partly to blame, because HR is slow to respond to workout intensities, but it's also human nature to go too fast instead of pacing ourselves smoothly.
It has helped me further define my relative strengths and weaknesses:
This is the "love/hate" part: You can't hide the results when you use a power meter! It's cool to see your strengths, and to see confirmation that your training is making you faster. But it sucks to see high-tech confirmation of your shortcomings. Some of the experts have come up with a "power profile" chart you can use to gauge your power compared to other cyclists that ranks you within a range from "world-class" to "untrained novice." According to this chart I'm still very much a sprinter! A pretty good sprinter actually. Not world-class, but not bad at all. And I'm not much of a climber, though I'm still fast enough to keep up with the fast guys some of the time. It's kind of reassuring to know this stuff. I haven't finished my complete power profile, but will try to do that soon. I'm really curious what my maximum 1-minute power is, but figuring that out is a demanding test that's hard to fit into my routine.
In the future:
The PowerTap, combined with better software, will allow me to better assess if I'm training too much or too little (you'd think our bodies would tell us, but they often lie!). I just need to spend more money to buy the more sophisticated "TrainingPeaks WKO+" software. I'm still using Saris's "PowerAgent" software which is pretty good, but lacks some of the cooler features of WKO+. Specifically, the "Normalized Power," "Intensity Factor," and "Training Stress Score" that WKO+ tracks really indicate the long-term training load we are under, and can predict very accurately whether we need to back off or go harder during the season.
And soon, once I have enough ride records with power data, I will know better whether the rigorous year-round training Coach Mark got me started on is helping or not. But for now I just have to hope that is is!