The chart above is the Critical Power (CP) chart as calculated for me by rowsandall.com. In this post, I will go through the science and non-science behind it. I hope that my explanation will help improve your understanding and help you use it to measure training results and prepare a race plan.

The CP chart tells you how hard you can pull (in Watts) for how long. Rowing is about maximum speed over a given distance, but speed depends on external factors (wind and current mainly), it is impossible to use speed as a measure for training progress. The relationship between speed (the result) and power (how hard you are working) also depends on weight and on your rowing technique, but for a given athlete, the power in has a very high correlation with speed out, so the goal of training should be to manage a power as high as possible over a given time which represents a typical duration of your race.

In the chart above, for example, I might want to improve my power over 4 minutes, as that is the rough duration of a 1k race in a single.

But first, how does the graph get its shape, and can you really move it?

Many of you may be familiar with the different energy pathways, but even if you aren’t, you know that you can hold a much higher power over short durations than over longer durations. Almost as if you have some energy stored in your body, and you have to chose between expending it all at once, or spread it out over a long duration. We also know that the power drop between a 1 hour maximum effort and a 2 hour maximum effort is much smaller than the power drop between 2 minutes and ten minutes. It is almost as if there is a power level that you can sustain forever.

This is exactly how initial Critical Power theories began [Scherrer and Monod]. The authors of the cited paper postulated a critical power CP that can be sustained forever, and a finite energy W that can be used until it is depleted. Thus the total power that you can hold is

*P = CP + W/t*,

Or solving for t, the time (in seconds):

*t = W / (P – CP )* – for power above CP

with:

*t *– time (seconds)

*W *– Power (Watt)

*CP *– Critical Power (Watt)

I will explain later why I stopped liking this equation, but the beauty is in its simplicity, and all other equations used refer back to this one and are basically improved versions trying to match real observations. It is tempting to relate W to your anaerobic capacity and CP to your aerobic fitness, and I am not against that, but be aware that there is not only one anaerobic energy pathway, and also that there is a complex interaction between the energy pathways. You cannot switch them on independently. Even worse, the balance between the different pathways depends not only on the power level P, but also on the history. Without a proper warming up, you will end up relying much more on your anaerobic pathways.

So what is wrong with the simple equation?

- At very short durations, the equation predicts very high power. We all know that everybody has a limit to your sprint work rate, so a realistic equations should flatten off at shorter times
- We also know that there is no energy pathway that can work forever. Your two hour power will be higher than your 4 hour power, which will be higher than your 10 hour power.

*P = CP1/(1+t/tau1) + CP2/(1+t/tau2)*