Sunday, December 18, 2005

Bike cadence vs. power tesing

Next I began a very interesting phase of testing on the bike. Tony said he'd been heavily resarching the relationship between cadence and sustainable power output. Most cycling fans have heard about the crazy cadences that Lance uses -- something in the 120 range during time trials.

I started with a 90 rpm test. The testing protocol goes something like this:
1. Find a computrainer (you must use a trainer that is capable of holding a constant wattage regardless of cadence).
2. Warm up for about 30 minutes, gradually increasing wattage until you reach a heartrate that is 5 bpm above your lactate threshold (that's 150 for me).
3. Carefully adjust the wattage on the computrainer for the next 30 minutes to keep your heartrate constant at 5 bpm above LT.
4. You'll probably equilibrate at a certain wattage for at least the last 20 minutes or so.
5. Average the wattage for the last 20 minutes of the test -- that's your power output at that heartrate.
My 90 rpm power at 150 bpm was 175 watts.

I ran the same test at 70 rpm and got 172.5 watts, so I assumed that I'm a 'flat' guy - my power must not be cadence-dependent. My coach said that was a little unusual, but not unheard-of.

I ran the test at 100 rpm. I expected that power at least to be the same as 90 rpm, if not a little higher, because it 'felt good' when I rode at high cadences. Guess what? My power was 140 watts, 35 watts lower than my 90 rpm measurement.

Now I was intrigued, so I ran the test at 60 rpm, which was hard to do because I'm used to riding at 90 rpm. My wattage was 190! That's 15 watts higher than the 70 or 90 rpm tests. I was surprised. I need to do more work to see how long that power could be maintained. I think muscular fatigue might kick in at some point and render the low cadence unsuitable for long rides an maybe for group rides where acceleration is needed. But for 10-mi time trials and sprint triathlons, maybe I'd found and advantage!

I'm going to run all the tests again to confirm the results, but it's opened my eyes to a possible advantage that I hadn't considered.