When running by power, your Critical Power (CP) is a valuable number to know. You can use it to determine your different training zones.

Your Critical Power is the power that you can maintain for a certain duration. Because of this definition, it can sometimes be confusing. In sports literature, this could be the power that you can sustain for 20 minutes (CP20), 45 minutes (CP45), or 60 minutes (CP60). CP60 is lower in wattage than CP45. And CP45 is lower than CP20. After all, you can last for a shorter time with a higher power.

Stryd uses one Critical Power, calculated based on your power curve. Without knowing your Critical Power you can’t properly use your power for training and competitions. A power of, for example, 260 watts says nothing, just like a heart rate of, for example, 173 doesn’t say anything. For the information you gather to be useful, you need to know what capacity you can maintain for a certain period of time.

Until recently, you had to do an exercise test with a sports doctor to accurately determine your heart rate zones. On a bicycle or a treadmill you would go through increasing levels of cycling harder and faster. A sports doctor would take a small sample of your blood at each level to measure your lactic acid values, or you would have to wear a mask for a breath analysis.

A major disadvantage of these expensive tests was that athletes regularly got anxious from wearing the mask or doing the blood test, and that the measurements were therefore not completely true to reality in comparison with outdoor sports. For example, it was possible that (due to rapid breathing) the anaerobic threshold was set too low and athletes started exercising with heart rate levels that were lower than they should be.

Result: frustration due to slow pace and little progression because of overly cautious training.

A power meter has the great advantage that you can determine your Critical Power outside on the street or in nature.

What’s the benefit of the power curve?

1. You can go full throttle on your favorite part of your run and you will always get valuable information from it. So even if it’s a hill of 272 meters or a lap with a distance that you don’t normally run in a competition, like (for example) 5752 meters.
2. You can see at what level of power you have to run for a PR at your favorite distance, and you can quickly see whether that’s already feasible or if you still need more training.

We dare to say that your power curve alone is already enough to make meaningful use of a power meter and to train for your PR in a targeted way. Achievements older than 90 days are not included in the curve. It’s about what you can do now, not what you were able to do in the past. If you performed well today, the corresponding point in the curve (duration and average power) will improve immediately. If a 90-day performance falls outside the curve, that affects the curve. The best performance of the past 90 days will take its place.

You can also use the curve the other way around. For example, if you think that 45 minutes on a 10K is feasible, you can check the curve to see which power is associated with that time. Whether or not a certain time is achievable with your current level, can easily be determined using the Race Power Calculator. More on this later.

The Race Power Calculator will give you a good indication of the minimum power level that you must maintain for optimal performance.

свернуть