How to calculate your Functional Threshold Power?

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How to calculate your Functional Threshold Power?

How to calculate your Functional Threshold Power?

Racing weight is a very popular discussion topic at the moment, and it's extremely important for both triathletes and cyclists.

The reason is this: if you ride a bike and you are lighter, it generally means that you go faster.

Over the next few weeks I’ll try to explain about cycling power and body weight, how they are linked, and what you can do to improve both.

Today, let me try to explain about Functional Threshold Power (FTP).

FTP is the average power generated by a cyclist for a duration of 60 mins.

However, a regular 60 minute all-out TimeTrial in a non-race environment is physically and mentally demanding, so as an alternative we use a 20 minute TT instead.

To calculate the TT, just take the average power at the end of the test and then multiply by 0.93.

This is because it's assumed that average power output will be around 7% lower over 60 minutes than 20 minutes (93% or 0.93).

FTP equates to roughly 85-90% of maximal heart rate; the point at which many of you may also find your anaerobic or lactate threshold.

FTP is important for cyclists because it is a benchmark figure, and can provide the basis for using power in cycle training.

For example, if a rider can hold 323 watts for 20 minutes then 323 × 0.93 = 300 watts.

So, FTP is 300 watts.

To do this test you will need some way of measuring power accurately - so, either a bike mounted power meter (SRM, PowerTap, Quark), or an indoor trainer with power (CompuTrainer, Tacx, Cycleops).

Warm up progressively for 20 minutes, then switch to an all-out effort for 20 mins, and remember to record your average power for the test. If you are measuring heart rate as well, then take average and max heart rates.

You should now be able to calculate your Functional Threshold Power.


Simon Ward