Power Struggles

Possibly not the blog you thought it was from reading the title, but really some down to earth answers to questions on a piece of kit you may be considering as a tool to help your training. Before you read on, please be aware that purchasing a power-meter & sticking to a power based training programme will put a huge dent in any ‘social cycling’ you currently do. It may also turn you into a number crazed power nerd, if you read on & decide to purchase one, make sure you decide on a suitable power/life balance beforehand, otherwise you’ll end up with as much social ability as a ’50’ TT specialist.

What is a Power-Meter

It’s a device that is attached to your bike which directly measures your how hard you are working. We’ve gone through era’s of coaching ‘perceived exertion’, moving onto heart rate monitoring, now we have another better way to monitor your cycling, power, measured in Watts. The benefit power has over heart rate as a measurement is that power is a direct measurement of what you are doing right now. Heart rate is a historic measurement of your exertion levels & is also affected by lots of other factors & will rise (cardio-drift) during a sustained effort. Power measures what you are doing right now, heart rate measures what you were doing a minute ago, including the accumulated stress of what you did before that time. As a simile, you know that annoying delay you get on an internet stream of a race, where you see the result on Twitter a minute before you see it in pictures? That poor quality delayed coverage is heart rate, the up to date HD Eurosport coverage is power.

Power-meters come in two major types, hub & crank.

  • Hub based power-meters are generally the cheapest power measuring option. The cheaper versions are less accurate on the power reading & weigh quite a bit. Powertap hubs can be bought separately & built on a rim yourself, or by a local shop. So you can ride them on different bikes, but if you’re buying one, get one that you’ll be riding in your training & can race to gather data if need be. A race only Powertap wheel (i.e. with a tub on it) isn’t going to get you the desired benefits unless it’s a 2nd wheel, you need to be using it for most of your training.
  • Crank based power-meters are currently much more expensive, accuracy is very good, but you’ll have to do a bit more fiddling with calibration. SRM’s are the standard for crank based power-meters, but lots more coming out slowly over time, at what looks like much cheaper pricing. You’ll be using this on the bike you use for training & racing, but possibly not put it on a winter bike, which could be useful.

Do I Need One?

Nobody ‘needs’ one, but if you’re struggling for time, it may help you go faster. It’s a great tool for removing ‘junk miles’ from your bike riding & helps you monitor progress, you can squeeze your training into a much smaller time-space. Power-meters are yet another expensive bike part, so I’d suggest that it’s going to make a much bigger difference to your performance than a frame upgrade or a set of ‘fast’ wheels, for a much smaller outlay. The only thing is that new frames & wheels look ‘bling’, power-meters look a bit drab & clumsy sometimes, so if your thing is posing & not going fast, a power-meter is not for you. You can probably buy a professional bike-fit, a power-meter for racing, a power-meter for training & individual coaching for the same money you’d spend on a new carbon race frame or a pair of top branded carbon wheels. It kind of makes sense, a new frame might not make you any faster, a properly used power-meter certainly will.

I’ll emphasise again, that a power-meter without analysis is just a toy, with the occasional, “I did the (insert local climb) at (insert respectable number) Watts last week”, which means nothing to you or anybody else. There are a large number of ‘power users’ doing this kind of thing, so just having one is going to make zero difference to your performance, but spending the time to work out what it’s for is required.

You need this book, “Training & Racing With a Power Meter” by Andrew Coggan & Hunter Allen, it has all the information you need to make use of a power meter. It might be wise to buy it first if you’re really serious & you are coaching yourself, then if it’s too much for you, sell the book on & you’ll only lose £3 or £4 on it, people want this book, it’s well used. If you’re using a coach, check they know about power, can analyse your files & tell you what you want to know, many can’t, but they’ll tell you.

There’s an argument too that riders who have incredible amounts of available time won’t benefit as much from a power-meter, if you have all the time in the world, to ride your bike during the day, ride chaingangs, race a bit during the week & weekends. It’s probably likely you’re getting all the training you need, plus it would ruin your enjoyment of the bike over long periods sticking to a set power output. I’d advice those people to stick at what you’re doing, how you’ve managed to get kind of lifestyle I don’t know, but you are living the dream, don’t ruin it with a power-meter.

What will it tell me?

The first thing you do is build a ‘power profile’, this is basically how well you perform over various times. These are 5 seconds, 1 minute, 5 minutes & Functional Threshold (FT). So an average power over the first three, then the functional threshold is what you can produce for an hour, but an hours testing is a bit of a drag, so it’s often taken as 95% of your 20 minute output, which is enough of a drag in itself. I tend to extrapolate it from a ramp test, but you’ll need the technology to do that, which many don’t have at home, so the 20 minute test should work for most. You also have to look at your events & see what timeframes are important. Simplistically, if you’re a road racer, then 5 minute & FT are very important, you can read a chart (in the book) which will show you where you stand on an international scale in each timeframe, be prepared to be humbled.

Once you have a profile, you can see if your abilities match in any way the events you’re trying to perform at, maybe you decided you were a kilo riders, but your 1 minute power turns out to be naturally rubbish, but you FT is great, could be you’re doing the wrong events for your natural talent.

One of the best tests is to actually run a power meter in a race, especially useful to look at data where you were struggling, or even better where you were dropped. This will tell you, in no uncertain terms, exactly what was going on, especially as your heart rate is likely shown too, so you can see how well you recover between efforts & which a particular efforts cause you big problems. We call these demanding efforts ‘matches’, you only have so many ‘matches’ you can burn in a race before you are totally spent, so identifying what your own matches are (different for everybody), then training that area specifically will help you perform. Then after some training, you can theoretically increase the number of matches you take into a race, the efforts of others will have less of an effect on you, then you can survive & perform to a higher level. This kind of thing is impossible to identify with just a heart rate monitor.

So imagine a rider who trains by heart rate, he does lots of 5 minute intervals, but keeps getting dropped in races when it goes ballistic for short periods of time. The initial power profiling would likely show a poorly developed 1 minute output, resulting in tha rider starting to do shorter intervals & performing better. So you can help pinpoint things like the length of interval sessions you could be doing. This is assuming you’ve not digested the entire book, it gets quite technical, so I’m demonstrating what you can do before you’ve really grasped the mechanics of it, which you will be capable of if you’ve read this far & not given up.


Power measurement is going to become almost standard, prices will drop massively for measuring devices & knowledge will grow regarding how exactly to use them, but that’ll all take some time. If your club has a ‘power-nerd’, see if they’d be willing to help you find out about it, maybe borrow theirs, or get your club to think about purchasing a Powertap wheel (you’ll get problems with Shimano & Campagnolo cassette wars though, so be aware, but it’s easy to change if you buy both freewheels, which just ‘push-in’). A club power-meter could be a valuable device, I can see that becoming more normal, something that will actually make a difference to riders, but you need somebody who knows how to use the data to tell you something useful.

That’s the jist of it, power is useless without knowledge, the same as has been displayed for centuries by many, many people.

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