I’ve been using the CycleOps Powertap wheels for about 2 weeks now – it’s shot by and I’ve been busily downloading the data from every ride and busily analysing it at every opportunity. Very sad, I know.

Arguably the most important number for training with power is your ‘Functional Threshold Power’ (FTP). This is roughly the absolute maximum wattage that you can hold for 1 hour, for example, over a 25mile TT.

The FTP number is really important because you then use it to set training zones for yourself, for ‘recovery’ (walking the bike), ‘endurance’ (chilling or going for ages), ‘tempo’ (riding at that awesome level we all quite enjoy), ‘threshold’ (riding so it’s a bit hard to speak in sentences), ‘Vo2 max’ (riding so hard you don’t know what you would say if you could speak), ‘anaerobic capacity’ (riding so hard you meaning the forget of words) and ‘neuromuscular’ (riding so hard you can’t see the power meter anymore) intervals. You can use these zones if you don’t have a power meter, either going my heart rate or perceived rate of exertion – using wattage just means you can be more accurate.

There are loads of ways of establishing your functional threshold power.

The simplest method is probably using your average wattage over a one hour TT. It’s still February and my first TT is in April, so I can’t do that yet.

An alternative is carrying out a formal test which takes 90mins on the turbo and is kind of boring.  Basically you wear yourself out a bit with a long warm up and a 5 minute hard effort, then pedal all out for 20mins, using your average wattage over the 20mins -5% to find your threshold power (the minus 5% is because you’ll need to keep that up for an hour!).

It later transpired that my turbo set up isn't exciting enough..


Alternatively, you can use a number the software generates for you called ‘Normalised Power’. Ideally you use the Normalised Power number from a one hour mass start race. CycleOps software then figures out what your wattage would be if totally unaffected by changes in direction, sudden ramps in power or drops – basically it averages your power.

The Results?

I came to my first issue with power data when I did both of the above. Over a one hour (and 15min) race, my Normalised Power was 204.

I wanted a more formal test – so I did the turbo version too. The answer? Average wattage over 20mins was 183 (just 2 watts over my average over 20mins of an ‘easy’ endurance ride) – minus 5% of that and you get … 174. There is a possible technical explanation for this, in that I only discovered afterwards that I needed to reset, or ‘zero’ the power computer before riding on the turbo – so this could put me a few watts out. And in addition, such is life.. I did wake up with a cold the next day. So maybe I wasn’t at my best. But regardless, the two numbers are still very different. 

I was perplexed. So I emailed British Cycling level 3 coach and Cycling Weekly journo Huw Williams (@huw_williams1) with my data files attached and asked : “Which number do I use?”

He came back to me with an answer: “It’s very easy to overcomplicate this. Bear in mind that threshold is the maximum amount of watts you can sustain for 1 hour – then normalised power for a 1 hour race is pretty bang on the money. So your peak power for 1 hour at Cyclopark normalised at 204w and that will be very close to your FTP because that’s what you did.”

He then gave me a simple test to check this – which is next on my ‘to do’ list. (just as soon as I get over the nasty cold!!) However, he reassured me too, that the difference in effort was pretty normal, explaining: “This will be down to thermoregulation – you don’t have a nice cool breeze blowing in your face like you do on the road and motivation,  the fact that you are far less motivated than you are on a track surrounded by other riders trying to beat you. So ideally you might want to do this re-test on the road on a suitable TT course.”

Taking Huw’s advice, I’ve set my ranges using the race normalized power as a start. The next step is easy – zones are set as a percentage of my new FTP. The step after that  – trying to train at a % of them – remains to be seen!

How do I compare?

Our social media man Balint keeps telling me he’d like to know exactly how the numbers compare with the pro’s (some sort of morbid cruelty? On my google searches I found this was actually a common question people asked – so maybe it’s just me who would rather not know!). I did try googling to find the FTP of Marianne Vos, but alas google will not yield. So instead, I pulled out ‘the chart’ (by Hunter Allen and Andrew Coggan) I used in the last blog.

Firstly – it all depends on weight. A cyclist putting out 300 watts who weighs 55kg will be faster than one putting out 330 watts and weighing 65kg. But if we use the chart I pulled out last time – then the FTP for a female world class cyclinst my weight would be 337watts, a domestic pro would be looking at 295watts and a cat 1 racer might be looking at around 253watts. Then bear in mind this is just the FTP – using the chart, that top end pro would be pulling out 1,145 watts over a 5 second max. That’s 630 watts more than I’m can sustain as my max (so far)…

Did I learn anything else? 

The turbo wattage reading still puzzles me a bit and makes me wonder if the discrepancy might tell me something about how hard I’m working when I’m sweating it out in the garage.  Clearly, I need to buy myself a better fan, and maybe I need some sort of massive posters of Marianne Vos and Beryl Burton. That’s another plus for the power meter – it doesn’t matter how hot and sweaty you might be, or how hard you think you worked- numbers don’t lie – and using the power meter you know exactly what your best is, and what you did in your last session.

For the other blogs in the series – check out:

1/3) A beginners journey: http://bit.ly/1eJuoYi

3/3) Using the data for the season and beyond: http://bit.ly/15vorpI

(Michelle works in Marketing and also blogs at www.trainbynumbers.blogspot.com )