Finding your W' starts with your best efforts
There are many ways to find your W’. GoldenCheetah software is complex but powerful and free. Just import your last 90-days and go to the CP chart and it will tell you your W’. You can use XERT and their free trial. XERT does a good job of determining your “High Energy” i.e. W’ automatically just by connecting to Strava.
A more manual approach. You need to find your best effort. This effort should be between 2-minute and 4-minutes. You can use software like Strava Summit or TrainingPeaks premium to give you your best efforts and many other options. It will show you your best average power for X minutes. If you are not sure you can always hop on your trainer, do a solid warm-up and go as hard as you can for 2-minutes, try to pace yourself so it is even power and see what your average power is. You can repeat this a few times over a couple weeks to get your maximum value. With practice, your pacing will be better and your W’ will get more accurate.
Obviously you must have a power meter for this activity.
Calculating W' from Best Efforts
Once you have your a best effort, you can plug them into many calculators.
XERT calls W’ (High intensity energy). The XERT page is nice and simple. We don’t know the exact math they are using, but they do high quality work. If you click on this link, I put some example values in to make it more clear. See the XERT Calculator.
Below is a link to a calculator that uses Excel. This requires 5 values but you can just do a 1-minute best effort, 3-minute and your FTP for example and repeat FTP 3 times. (see screenshot)
I am sure you can use Google and find many other “Critical Power Calculators” to tell you your W’ and my guess is someone will post some comments with some better ones below 🙂 I am ignoring Critical Power (CP) because it is close enough to FTP for our purposes. If you are a perfectionist, you can find and use your CP in combination with W’. We called it CP on our UI because of this reason.
Above is a screenshot of the values filled in on that EM Sports Science Excel spreadsheet. The screenshot shows 480-seconds (8-minutes) but you can use your FTP and 24000 seconds (40-minutes).
Once you know your FTP and your W’ you can use the features on our workout creator and to find or create the perfect interval workouts for your fitness profile. View the next article to learn more.