I have a power meter. What do I need to know?

Posted on Posted in blog, Coaches

This article is written for the athlete using a power meter for training and racing. This is NOT for the coach or athlete who is looking to analyze their power data; we will cover that in later posts.

As a coach I love it when a client has a power meter because it gives me a ton of information about what the athlete is doing and how they are doing it but as an athlete I totally understand how scary and foreign it seems.  What in the world do all of these numbers and abbreviations mean? I get it, it is like me sitting down at a restaurant in Paris looking at the menu and trying to figure out what to order. I feel like I can figure it out but I can’t and the next thing I know I am eating a part of an animal I don’t want to be eating.

Power meters are expensive and in my opinion, are probably the best investment in training/racing you can buy (except for a coach of course).  You have to look at how a power meter can help you as an athlete first and get a good working relationship with it.  Only after you learn to train/race with it can you begin to look at it as a tool for cycling analysis.

So what do you need to know to get the most out of using your power meter to start? The main thing you want to understand is Functional Threshold Power (FTP) and how your training zones are based on that number.  Your Functional Threshold Power is basically your Lactate Threshold (LT); yes there is more to it but remember we are keeping this simple! Your lactate threshold marks your ability to match the muscles aerobic energy demand with energy availability. Your FTP represents the wattage you can produce for 45-60 minutes while maintaining that balance of energy demand with energy availability; once the demand becomes greater than the availability fatigue will begin to set in and performance will decline.

Once you have an FTP you can then create your training zones based on percentages of that number. Different coaches use different zones and I am not going to get into a discussion about that in this article. If you have a coach you can speak with them about the zones they choose to use, if you don’t have a coach then feel free to reach out to me.

So now that you have your FTP and proper training zones how do you even use the power meter? One of the first questions I get from my athletes is what should I display on my cycling computer and what do they mean? A few of the fields may change based on the individual athlete but there are a few that everyone of my athletes will use which are discussed below.

Watts

You will see that you have the option of showing current watts, 3 second average or 5 second average. I have all of my clients use the 3 second average because that keeps the number from bouncing around like crazy. It takes the average watts produced in the last 3 seconds, if you pedal at a cadence of 90 you are getting the average power output of about 4 pedal strokes. As you can imagine the power you produce per stroke varies widely depending on where your foot is in the revolution, if your foot is at 3 o’clock you produce much more power than when it is at 6 o’clock; 3 seconds allows for that number to smooth out so it is easily readable.

Average Power

This is exactly what it sounds like; it is the average power for that session. If you ride for 1 hour and you ride 10 minutes at 200 watts and 10 minutes at 100 watts for the full ride you would have an average power of 150 watts for the session.  If you rode for 300 watts for 2 minutes and coasted for 2 minutes at 0 watts then you would also have an average of 150 watts for that ride.

Normalized Power (NP)

This is a tough one for athletes to get so I am going to keep this as simple as possible and try to avoid the nuts and bolts of how we get this number and just keep to what it means.  If you are interested in how we get this number I will address it in a future post or you can look up the explanation provided by Dr. Andrew Coggan.  So for our purposes, I am going to use the definition provided by Dr. Coggan from his post on TrainingPeaks.com Normalized Power, Intensity Factor and Training Stress Score where he states “normailzed power provides a better measure of the true physiological demands of a given training session. In essence, it is an estimate of the power that you could have maintained for the same physiological ‘cost’ if your power output had been perfectly constant, rather than variable.”  Ok, so what the heck does that mean? Think of it as a better version of your average power. Remember above we talked about if you averaged 200 watts for 10 minutes and then 100 watts for 10 minutes your average power for the workout would be 150 watts, but if you rode 300 watts for 2 minutes and 0 watts for 2 minutes you would still average 150 watts for the workouts.  Do you think those two workouts would have the same physiological demand on your body? As far as the average power suggests it should but we know that physiologically the demand between them was different and that is what the NP provides you.

Variability Index (VI)

Variability Index is the relationship between the average power and the normalized power.  It helps us understand how we are riding. We understand that the average power is just simply the average power and that normalized power is the actual physiological cost of the ride. The VI is the percent difference between them and for triathletes we want that number to be within 10% (1.10 or lower).  As an example, if we are targeting a 200 NP for a race then we want to see our average power to be between 200-182 and hopefully closer to the 200.  Why? As a triathlete you need to run off the bike and it has been shown in studies that you will perform better after a consistent effort rather than a highly variable effort. What we are trying to avoid in racing is an interval style of riding where you go hard for a period of time then recover, what we want to see is a nice and consistent power output for the ride. I understand that certain courses, especially hilly courses, may make it hard to stay consistent with power but that is where a coach can be extremely helpful with a race strategy as well as helping with gear selection to help avoid working too hard on the hills and to easy on the descents.

Along with the fields above I like to have a few more fields on my computer that are pretty self explanatory so I will not go into great detail here for the sake of saving space but will list them to give you some suggestions:

  • Cadence: The rate at which you are pedaling. I keep this displayed as most people are generally more comfortable/efficient riding in a certain personal range.
  • Power Zone: If you log your FTP into your computer it will generate a list of your training zones and can be displayed as a number (Zone 3 or Zone 4) which is generally easier to see at a quick glance at the computer while riding outside.
  • Speed: I have this on my computer but generally hide it on a second screen because I want to use it as a check-in every once in awhile when racing. I don’t want to race based on my speed; I want to use power to control my effort. I do want to be aware of my speed to help with nutrition needs by understanding how much longer I will be out on the course. As well as I  can assess if I am getting free speed from a legal draft or tailwind. If I am going 25mph at below my power goal because I am legally behind another rider and my goal is to go 25 or less then why not hang out there for a while at an easier effort.

Having a power meter is a great tool to become a stronger cyclist and a smarter racer. I say it all of the time to my athletes that I would rather have a cheap bike with a power meter than the best bike without one. Can you become a better cyclist without a power meter, sure, but it is a whole lot easier to do it with one.

Work, Live, Tri

Coach Hammond

Learn More at our “I have a Power Meter and Have No Idea how to Use It” Event on January 25th

Side Note:

On a side note for those of you who have used training zones based on Heart Rate you now have to understand that you need to choose which value is going to drive your workouts; Heart Rate or Power.  What I am saying here is if you are in the middle of an interval that is asking you to be in Power Zone 4 (91-105% of your FTP) and you see your heart rate is not is your old HR Zone 4 but rather in Zone 3 (lower) or Zone 5 (higher); What should you do? Should you increase or decrease your effort to get your heart rate into Zone 4? NO !!! The workout is being driven by the power zone NOT the heart rate zone. You can not try to control both values; you need to decide which one you are going to focus on and use that value to control the workout and then you can go back (after the workout) and see how the other value responded.  I highly recommend using the power value to drive the workout and use your heart rate numbers to help assess the workout after.  The reason power should be the driver is that it is representative of the work you are actually doing whereas heart rate is a result (or predictor) of the work you are doing. We will go more into detail on this in a future post as well in the workshop that supports this article.

 

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