Watts and Training
Please tell me my stationary bike watts meter isn't working right! I have been training VERY, VERY hard for my first races (20 mile and 50 mile) and have been looking on the web for the best measurements to use to check training progress. I found a lot about watts but am very concerned because the watts levels that they are showing are well above what I am producing on my bike.
I'm 45, 145 pounds. I've been building my training up for 7 months riding, running (infrequently due to a bad knee) and lifting weights (focusing on upper body). The past few months I've been stuck trainig inside due to the snow. I have my stationary bike set to its highest level (16) on crosstraining. So, there are extended times at the highest level, intervals between mid-level and highest level, as well as other variations but none going below the mid-level. Over 30 minutes I am averaging 10 miles and only 130 watts which is low even for a casual rider from what I've read! My average heart rate is 140-145 which, according to what I saw on Wikipedia, is on the lower end of hardcore training.
So, am I doing something wrong or does it seem like my watts reading is just off?
First reaction: yeah, something's wrong with your setup. Find a significant road hill climb that takes you a while, e.g. 10 minutes. Use Google Earth to determine altitude at the bottom and top. On a day with neutral winds, go warm up, then climb the hill and time it. Plug the numbers into this wattage approximater and get some real-world wattage. It's not perfect but I bet you'll find you're capable of a lot more than 130 watts :)
Those numbers are a bit low, but remember you're only 145 pounds so your power to weight ratio is different from someone who is 165 pounds. Also, I wouldn't trust wattage or HRM from your stationary bike - you need a real test.
With a lot of these things, don't concentrate on absolute numbers. Instead, concentrate on deltas (the change of your reading over time).
The problem with absolute numbers not being consistant device to device is not limited to bicycle power meters. Read up on car dynometers and how inertia dynos (like Dynojet) compare with eddy current or water dynos. You can put down one number on a Dynojet, then drive across the street to a Mustang and get a completely different number.
Calibration differences, differences in how the power value is determined... all these things can change the value the meter reads.
BUT, in most cases the meter is internally consistent, meaning that although it may under or over read, it always does the same "error" the same way. That means the deltas are correct. If power is increasing, you are putting out more power, and the amount of increase on the meter is proportional to the amount of power being increased.
My suggestion is to forget that your meter reads in "watts". Pretend that it is an arbitrary unit of power, and all that matters is that a bigger number means more power.