How to Calculate Your Critical Power

To use the model based on Monod’s Model you need to know your weight (in kg), the test duration in seconds (longer than 3 min shorter than 30 min) and average watts (which is converted into joules of work per kilogram) for each of the tests completed. The model is simply a regression of work against time, with the slope of the line equaling Critical Power in watts/kilogram and the intercept equaling anaerobic work capacity:

Work in Joules/kg = AWC + CP x Duration

 

Example: 

Weight 63.63 (140 pounds)

Test 1 - 20 min (1200 seconds) - 260 watts average

Test 2 - 3 min (180 seconds) - 310 watts average

Weight  (kg)     Test (Seconds)    Average Watts     W/kg      Work (joules/kg)

      A                           B                        C                D (C/A)       E (D*B)

    63.63                    1200                    260                   4.08             4896     

    63.63                      180                    310                   4.87               876

Now you need to perform a regression of Work (column E) against time in seconds (column B). The slope of the resulting line will be Critical Power in watts/kg and the intercept will be Anaerobic Work Capacity (AWC)

i.e. For the example above will be CP 4.04 and AWC 69.

To make your life easier just download the attached excel sheet

** For those using a Kurt Kinetic or ClycleOps Fluid trainer who don't have a power meter, yet are using the power/speed curve to estimate it, download this. Don McKinnon, member from Beginnertriathlete.com was nice enough to put this together and share it with us. The info is based on Kurt Kinetic Power Curve***