Strava · Wellness App Reviews

What is a Good Stryd Critical Power?

There are dozens of ways to measure how your performance is progressing through training. Each of the top devices and trackers have their own, and Stryd is no different with their Stryd Critical Power score.

Stryd critcal power

Critical Power, or CP, helps determine what “type of fatigue your body experiences” (source). This is similar to a lactic threshold, when defines where your body is building up lactic at a rate higher than it can clear it. Time spent above these levels will greatly reduce the amount of time you can continue. Below these levels are endurance zones, where it becomes more important to handle nutrition and form to keep going.

Critical Power and lactic threshold also somewhat correlate to a VO2 max. VO2 max is about a maximum though, a level of complete exhaustion where the body is tapped out, this is very different from Critical Power which is measuring sub threshold endurance levels. VO2 max can stay the same while you become more efficient and CP continues to rise, so although they have some similarities you should not anticipate them changing at similar rates. The other metric that CP is related to is a FTP or Functional Threshold Power. Although FTP and CP are not the same, they are usually pretty close to each other. Assuming CP and FTP are identical generally will results in similar training zones, which is the main reason people track either. For differences in CP and FTP you can see more on other site. 

Critical Power Levels

CP is measured in Watts. To compare it across individuals and account for different body and muscle sizes it can also be expressed as a Watts per Kilogram or W/kg. For the most part though a simplified single watt power is the key measure.

So what can you expect from a critical power score? Do elites have 3x the scores of beginners? In one study that looked at trained cyclists the measure for CP averaged to 256W. There is large variability to this number though as the rating was +/- 50w. Still this number was slightly higher than the measured FTP in the same test. 

So it is safe to say that a CP between 200-300W is “good”. On the flip side a new cyclist can very well have a CP of 50-100W. The early learning curve will allow somehow who tests at the very beginning to increase quickly. This is especially true if you are new to endurance athletics and simply do not know how to pace.

Even advanced athletes have stories of going out too strong, whether on a full ride with a power meter or on a 20min FTP test on a trainer. Over doing it early will kill a CP or FTP test. CP less so since it is the combination of rides or runs over different time intervals, but bad pacing will still kill a power curve. 

Stryd CP Compared to FTP and others

Stryd critical power is just one measure of how to set training zones. Other similar metrics include FTP, or functional threshold power, which is used by both Strava and Peloton. Other measures like VO2 max might be correlated to a critical power reading, but it is not great at predicting training zones. The exception is if you take a lab based VO2 max test, which should also define a heart rate for lactate threshold which gives you a similar idea of when the body switches over to an unsustainable level of muscle output. 

Even more fitness measures will correlate to CP. These include VO2 max proxies like the Health Mate fitness level and other random fitness trackers have their own measure. Many of these are designed to see how good your fitness is, and while they all have their place, none of them are entirely comprehensive. 

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