Wednesday, February 3, 2016

Fatigue Curve Calculator

by Alan Couzens

I've created a simple calculator to help you calculate your own fatigue curve (along with an estimate of your FTP).

To use, enter two or more best power numbers (from true max effort tests) for any of the durations listed: 5 minutes, 20 minutes, 60 minutes, 2.5 hours, 5 hours, or an Ironman in which you ran well. Enter these in the white cells and clear the sample data from any cells for which you don't have current data. Ideally, these will be normalized power numbers (especially for the longer durations).

The curve produced will give you an estimate of FTP (the first number in the regression equation at the top of the chart -- y=....) and it will give you an index representative of your current "fatigue curve." For a key on what this number means, scroll to the table in the middle of the article linked above. As a general rule of thumb, your percentage drop off each time the duration doubles will be about two-thirds of this index, that is, if that superscript number is -0.10, your fatigue rate is approximately 6.7% (0.10 x 2/3).

By tracking this two factor model over the course of a season, you'll not only gain a good sense of how your general aerobic fitness is improving (via the estimated FTP) but also how your strengths and weaknesses as an athlete are developing (via the fatigue index).

Happy data mining!

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