You also get a useful tool for analysing the data, setting barometric pressure and adjusting your 'coast-down' values post-ride. So you can load old rides and update the ibike values, for example, if you have adjusted 'em. It gives you more control over the results. The blue area is the crit last week. The rest is pre-race warmup and post-race cool-down. Top-most graph is power in Watts. Next is speed, then elevation and last of all slope. You can see from elevation that there's a hill each lap... and you can move the cursor to any point and get power, speed and elevation data at that point.
And this is the power peak in close up. Along the bottom of the display you see the data on the cursor: 752W, 35.9kmh, 3.8% slope. If you run those numbers through your calculator (plus weight, temp, barometer, elevation, headwind, all available from the ibike) you'll verify that's pretty darn close. The only real problem is when you hit the 'go' button too hard on a climb and lift the front wheel. You can easily turn 3.8 degrees into 4.5, or more, and get a huge - and inaccurate - power reading. But you can fix that any number of ways, too. Especially if you ride the same hill a few times and know the slope doesn't exceed 4.5%, for example.
Last for today - this is a closeup on the velocity peak. Speed maxed out in the sprint at a lowly 49.1km/h, best so far being over 55kmh, but it was into a headwind this time, and I managed to pick the wrong wheel to follow, too. So I ended up in front too early. Still, you can see the power peak on the hill just prior to the downhill sprint - basically where the last attack went. We continued at good speed until the 90 degree left turn but power is down because I'm on a wheel and we are dropping elevation. Someone starts the sprint, I chase, catch and get marooned. Ooops. You can see the sprint power is 529W and the wind has increased markedly after the left-turn.True, it doesn't tell you anything that you couldn't have worked out anyway, but it puts it right in your face -up in lights. 3 races documented so far and I know how critical that hill is - it's where most attacks start, especially on the last lap. I can see exactly what power I need to generate to match those attacks, and I can see how important it is to stay calm, hang onto a wheel and don't go too early in the sprint, especially if it's windy! And I can take this data away, find a similar hill and practice putting out 700W+ intervals. I could tailor a 'crit simulation' session around this data and see what works. I may find that those steep, medium-power intervals don't help me in crits and that I need to do more snappy, higher power efforts over shorter distances. And so on.
You can do it by feel, or you can buy a power meter and 'prove' your theories. It's up to you.
