A power analysis for Cyclocross
I spent spent some time this week looking at power files from races over this season. I've had a couple athletes ask me how to read the data from a cyclocross race. This is not the easiest endeavor for a couple of reasons.
1. power output in cross is big spikes over very very short periods of time. Dependent upon the power meter and the actual head unit, some of this data may not be recorded and maybe lost.
2.Power data does not take into account the run or barrier sections.
3. Heart rate data is also misleading because of the limited nature of recovery and therefore little or no drop in HR occurs during a race.
I intend to go through several of these over the course of the next couple of months and see if I can shed some light and enhance the uses for power data in cross.
The nature of cyclocross is that we will have sections in every course where we are at 0 for a power number. Whether that be in turns, at the start, on down hills and on run sections, we find our power and cadence at 0. a key to racing is how quickly and how efficiently we can get the power back up and be accelerating out of these 0 power sections.
There are a couple keys here.
1. Gear selection. Be sure to enter the corner in the appropriate gear to be able to accelerate out of it. Smaller gears with high cadence allow for more torque and subsequently a quicker acceleration to top speed.
2. How long a rider pedals entering into a corner or technical sections and how soon they are on the pedals coming out of it.
3. How aggressively a rider attacks the exit of a feature to get up to speed quickly.
On this first go through I have decided to focus on how to use the data to show riders where there is room for improvement. Below are two power files from the Feedback Cup here in Colorado a few weeks ago. A little background on Feedback Cup. The course is very twisty, turny and features short drops followed by intense short hill efforts. In many ways it resembles a Short track MTB course in its technical nature and punchy style. It was a 65 degree day and it had been very very dry in Colorado.
Below are two power files from athletes I coach. The first is from a rider in the male pro field. A very good technical rider with a background in MTB. The second file is from a female rider in the pro field. She is a strong power rider without a strong technical background. He finished 3rd on the day and she won the race.
While the power numbers themselves are interesting and a good deal can be derived from the files in terms of fitness and overall strength, we are going to focus on a more specific feature of 'cross. Acceleration.
Taking a look at the two files a couple things jump out. Take a look at the power spikes in the top file. These spikes are out of the ordinary when it comes to the rest of the race. The rider is jumping hard on the pedals out of features in order to get up to speed very quickly and the power spikes are representative of that. In the second file, there are spikes in power out of features but they are less pronounced and more in line with the rest of the race.
Another interesting thing is at the bottom of the power range. In the top file the 0 power periods are short with a sharp rise in power out of them. This creates a V shape at the 0 power places. The rider is quickly on the gas out of features and their power is rising abruptly. Looking at the bottom file, the 0 power sections form a U shape instead of a V shape. This rider is spending more time at 0 power and is taking longer to raise the power out of these features.
Take a look at your own power files from races and focus in on the 0 power sections. Is the file showing that V shape or the U shape. If you see lots of U's, focus on gear selection entering the corners so that you can accelerate with high cadence out of the features and leave your competition in the dust.