Critical power profiling

CP_profilingAim of Session

This session allows measurement of your 'power-time' relationship, and estimation of your Critical Power.


Session description

WU: Have a 15 minute warm-up before the trials. Even consider a full race warm-up if doing this session out on the road

MS: Three trials, each one of a different duration: one short ~3 minutes; one medium ~7 minutes; and one long ~12 minutes. In each one, you will go as far as you can in that time frame. There are two ways we can do this:

  • In the lab (usually with at least 2 hours of rest in between each trial)
  • Out on the road (see picture above) - allowing at least 15 minutes of easy pedalling in between efforts


Critical Power is an important indicator of performance in cycling. It represents a power that can be maintained for between 15-60 minutes (depending on the athlete). On an exercise intensity continuum, Critical Power sits above a steady-state exercise intensity and represents the boundary  between zones 4 and 5. Cycling continuously at this intensity will lead to exhaustion within a period of about 60 minutes. This is thought to occur because of an increase in the waste products associated with fatigue. Maintaining Critical Power intensity becomes gradually more demanding until the body is performing at its maximum. This maximum output can only be maintained for a very short time (less than 5 minutes) meaning exercise will need to be stopped or the intensity drastically reduced at this point.

Application for the Rider

This session incorporates three fixed duration rides (3mins, 7mins and 12mins). From these rides we can record the average power output and plot this on a graph against exercise time. The pattern this data produces (a hyperbolic curve) can be extended to predict Critical Power. This will represent a power that will be somewhat similar to your 10-mile race power. In fact, this Critical Power might even be prescribed as a target power for a race over this distance.

Practicalities and tips!

  • How you run this session will depend on whether it is a session you have been directed to do independent; or if performing the trials under the supervision of the coach / sport scientist. If under your own direction, consider if you are more likely to get everything out on the turbo, or out on the road. Whichever you choose, ensure you set up conditions that can be repeated on subsequent testing occasions.
  • You will find you get better at CP testing with experience. Performing in fixed time periods is like performing in a race - its all about doing the most work in a given time; like a race is doing as much work in a given distance. Use your race experience to help you pace
    • The 3 minute trial is almost 'all-out'
    • The 7 minute trial is about your VO2max interval pace
    • The 12 minute trial is a bit like a 5 mile race effort
  • One approach is to set off with a power you know you can hold for that duration, and ramp the effort up within the final half of the trial period
  • Some athletes prefer not to see the power output, but will focus better on having time alone on their display

Evaluation of the session

After completion of this session, you can plot a graph of power against time to predict your sustainable intensity, or the Critical Power (similar to 10 mile race power). You might like to try this yourself using our interactive calculator