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What is a critical power curve?

Power curves seem to be on most online platforms now, ranging from in-depth ones on TrainingPeaks WKO5 to a simple setup on Zwift and Strava premium accounts. These curves can be really useful in plotting changes in fitness and working out your strengths and weaknesses.

A simple way of breaking down the power to curve is to know about ‘training levels’ which can be broken down into four different groups. These groups are determined by the dominant metabolism, which supplies energy to the muscles during the exercise.

  1. Neuromuscular power: 5-10seconds. The phosphagen system.

  2. Anaerobic capacity power: 30secs – 2minutes. Anaerobic glycolysis.

  3. Vo2Max: 3-8minutes. Anaerobic and aerobic glycolysis.

  4. Steady state/endurance power: 10mins to several hours. Oxidative system.

These can be further broken down into types of riders.

  1. Sprinter

  2. Pursuiter

  3. All rounder

  4. TT’er/Rouleur

Power curves can help understand the overall relationship between time and power exhaustion, but they can also help prescribe training workouts within plans to create maximal adaptations and (ultimately) results.

The example athlete above clearly has a good sprint, but not exceptional, then they fade away around the 5 minute to 60 minute mark. Depending on the athletes chosen discipline, this would depend on where to focus their training plan. The standards are sometimes set to watts per kilogram (W/KG) so that riders of different weights can be compared across the power duration curve. For this athlete, if they were competing in cyclocross, I would build an FTP phase going into Vo2Max work to try and bring those areas up to the middle of the ‘good’ category across the curve.

The Strava and Zwift power curve do not give an outline of how your numbers compare to others, so have a look at the table below for a better idea of where your numbers lie.

One factor which must be taken into account when creating a training plan is how much fatigue a session can have on an individual athlete. Even though each individual athlete will be training to their own zones, the same session will have a different impact and adaptation on them. If someone is working on an area of highlighted weakness, it is more likely to have a more fatiguing effect on them, session to session and day to day.

After each session, you will be able to compare that ride’s numbers to your date range set on the curve. This can be set to compare against your all-time peak powers, or it can be set for a smaller range of monitoring where you are compared to 4-6weeks ago (depending on your training goals and aims at present). You must remember these are peak power numbers… if you have performed an all-out effort, you are unlikely to get near that in ‘every day training sessions’ when performing repeatable intervals.

Different athletes will respond differently to training. Even though you have worked on a weakness, it doesn’t automatically mean you will see great leaps in performance. Genetics can determine your own individual limitations and, no matter how hard you work on them, you will never be great in every area.

Take some time in the off-season to work on different areas of the power curve and determine where you see the most gain. As well as this, it’s always important to focus on your strengths - these are the things which win you races.

An example: a TT specialist who always gets beaten at the end of a road race in the sprint. The athlete has been blessed with a naturally-high FTP but a low number of fast-twitch muscles fibres. No matter how much sprint training they do, they will never be a great sprinter… they should concentrate on adding 30watts to their FTP and riding to a solo victory, rather than trying to up their sprint by 50watts... and still getting beaten.

Finally, do not get drawn into completing everyday as a test against this curve. Ultimately, to improve the numbers on this curve, you must complete weeks of training at specific training zones to then perform an all-out test where you finally see the fruits of your labour.

Remember, monitor your weight as well and keep that up-to-date in your software of choice so that the graph isn’t thrown by dodgy data.

Any questions, don’t hesitate to get in contact via me email.



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