Is looking at watts a good barometer of workout?
 

Some sites have a "watt calculator". Is this type of resource a good tool for evaluating a ride/workout?

Forget if the formula is correct or not. If you're always using the same formula, won't it balance out?

If use watts, then what is the normal variance between workout? The problem with using average speed is it doesn't take into account the differences in wind speed and I thought a watt tool might help keep up the enthusiasm when the speed drops but the intensity is higher.

Here is the site I've been using: http://www.kreuzotter.de/english/espeed.htm

I'm seeing swings of 120 watts, and that seems a bit too much variation to me.

That watts calculator is fun but some of those variables are just too hard to pinpoint with consistent accuracy. Watts is a superb workout indicator and is the future of training as more power meters hit the market and prices drop. Go to www.cyclingforums.com and click on power training.

I just used the site you provided. I checked one section of the ride I did yesterday against it. According to the site I was putting out 320 watts. According to my powertap I was putting out 170 watts. A pretty big difference.

I'd like to quote a bike forums poster, not sure who it was....

"I was comutting to work yesterday and passing through Prospect Park. There was a guy who looked like Lance fully decked out with a Trek and Team Discovery outfit. Even his helmet straps were yellow..... I have my power output set to 400w. roughly 19 mph. I glanced back at him and to initiate the challenge. He took the bait. He was slowly closing in to my wheel. I stood up and dropped down to my 13th gear and just blasted it up at 19 mph. Unless he has been racing, there is no way he could match my speed."

400 watts sounds like a good starting benchmark? :D

Well, some of the cyclo-computers calculate watts. It's an estimate based upon various assumptions of speed, wind-resistance, rolling-resistance, weight, grade, etc. and you'll end up with a +/-25% variation from actual measured watts of a Powertap.

Even worse are the online calculators because they're even further away from your bike; they don't even measure anything! That requires you provide it with proper information and that's hard to datalog accurately. You'll have no measurement of wind-speed/direction or grades of hill or percentage of time spent on that grade, etc.

The only accurate way to measure watts is with a hub or crank-based force-measurement instrument. Only if you've got a Powertap would looking at watts be a useful indicator.

That person may want to plug their numbers into the calculator at analyticcycling.com. Unless you're huge or going up a hill, 19mph isn't anywhere near 400 watts. More like 280 watts.

Wow, that's both good and bad to know. Good because it shows the accuracy is more than +/- 25% and bad because it means I am even in worst shape than I realized. Ugh....

For others,
this is a commute route so:

grade is always +/- 1% depending on condition
weight of bike and ride are almost always the same
temperature for the am and pm is known
wind speeds and gusts for am and pm is known
distance is always the same
Only big dialy variable not turning off timing during red lights, but there are only 2 lights and over 20 rides the wait times average out.

So only meaningful variable seems to be time and energy generated, right?


I can't afford a couple hundred right now for a power tap, and here we have more wind in the winter than in the summer. So I was looking for some encouraging numbers to say I was making progress on improving my performance.

I've completed 92 sessions of commute riding. Every 25 sessions I complete a new spreadsheet, and was thinking of adding a "formula" to convert data to watts. If there is a better measure, or you all have some suggestions for more meaningful training records, please advise. I have to start the new quarter in less than 2 weeks.

I'm looking at the upcoming test results for the ibike pro (ibikesports.com). there's a lot of doubt surrounding this product because it measures power from resisting forces (wind, grade, speed etc) versus the force applied which is done via the crank of the SRM or the hub of the powertap.

The good news is that the pricepoint is "just" $350 and if it proves to be consistent and fairly accurate then it would be a great tool to have.

I don't know how much it would help but you could always go by average heart rate. If you are constantly doing the same ride then over time you should notice your average heart rate going down. That would be an indicator of your fitness improving.

If you know of a place to get a powertap for a couple of hundred please let me know. I would love to get one for my back up roadie and one for each of my mountain bikes. :o

The best benchmark is a standard course that you can do regularly without interruption from traffic. Like a 10-mile time-trial course with a blend of flats and rollers and maybe a hillclimb. Do it once a month and record your time. No need to compute watts or calories or anything, the stopwatch tells all. :)

Except for wind. Above 15 mph, wind is 80% of the battle. A difference of wind speed of just 5mph would make a huge difference in time.

No mention of warranty, but potentially an interesting product.