Am I buying a power meter for my bike this Christmas?

This season I noticed a number of triathletes training with and then using power meters during races. When I see power meters I can’t help myself thinking: ‘more expensive equipment – where do people get the money?’ (power meters are expensive, but not as expensive as they were some years ago, and there are many types – each with their own pros and cons), so are people mad to buy and use them? Or, are they a solid investment? 

Before going on, I must declare my allegiance to the non-pioneer approach to gear. I tend to let others buy expensive new gadgets and gear and wait to see if they work, are durable and, most of all, are worth it. I was a late comer to early heart rate monitors, Garmin GPS devices, to Strava, to disc wheels and to myriad other now standard biking technologies. I now use all of these and would enjoy cycling less without them all. But will this be the case with power meters? Are they here to stay? Will everyone who cycles a bike and cares about the data which can be collected on every ride soon have one as standard as every bike tends to have a bike computer these days?

I have discussed this with friends who have used them for triathlon and for cycling – for training and racing. Common themes emerge from these conversations. Some now view training without a power meter or a heart rate monitor as “old school”. The days of following a training plan or race plan and relying on experience is seen as almost naïve. They want to avoid blowing up during a race by knowing what they are capable of before a race even starts. 

For anyone who watched Chris Froome during this year’s Tour de France will know he did not always follow the bunch up the climbs, but kept his eyes firmly fixed on his power meter and stayed within what he knew was achievable across the entire climb. Nearing the end of the climbs, he was almost always back up at the front. He was using power meter technology to determine when attacks from his competitors, where the speed ramped up, could or could not be maintained and therefore whether he should or should not react. Treating each hill as a personal time trail may not be as exciting to watch as seeing the main contenders taking lumps out of each other, but it is effective.

More experienced cyclists and triathletes reading this article will note how they have been using heart rate targeting to effectively plan their training and racing for years, so why move to power targeting instead? I have used heart rate monitoring with decent results in running races, cycling and triathlons – so even I needed convincing. Some I spoke to say their power meter has dramatically improved their training, but why?

Much of the reason lies in growing expectations of our bike computers. Like the evolution of our mobile phones to pocket computers which perform an endless range of tasks, our bike computers no longer just tell us how fast we are going, the distance travelled and other basic data. We are now connected to satellites for our entire ride and we fit ourselves and our bikes with a heart rate monitors, cadence sensors, speed sensors and more – the result is masses of data we can upload to sites like Garmin Connect and Strava where detailed training diaries are kept and analysis of our training fully anoracked. We now want not only data though; we want the all the data we can get.

For many, this increasingly means recording power output data. Heart rate is not a great measure for training and racing as our heart rate differs – and sometimes quite dramatically – between when we are tired or rested, so it can be hard to judge, on any given day, what a very hard session is in heart rate terms. Power is less subjective than heart rate.

What you get with a power meter, I am told, is an absolute measure of output, say averaging 200W, 225W or 250W for a given training interval. Different power outputs provide targets to aim your training at. But more than this, you can target the right power for your race.

Those who have trained with a power meter say you quickly get to know the highest sustained power you can maintain for one hour or estimated functional threshold power - FTP. This sounds a bit like Jason Bourne in the Bourne Identity and apparently isn’t all you can use to determine your pacing plan. You can also, like Froomey, take into account your previous efforts. Those using Strava have a record of what they have done on many routes before. This data provides an idea what you can do on certain routes. If you know you’ve previously completed a climb at your maximum intensity then you will have power data for that effort. During your race, you will know you can hold the levels of power you previously achieved on the same climb.  If you can’t do it in training, you can’t do it in a race. If your fastest 50km time trail was undertaken at 70 percent of your FTP, then riding an Ironman race at 80 percent FTP is going to cause you to blow up.

When racing triathlons or bike races (especially time trials), you need to have a pacing strategy which is not just going 100% for the entire race. A power meter can give you an accurate percentage of FTP which you should be racing at for various length of race. The shorter the race, the higher should be the FTP. This might mean 100% of FTP for a 10 mile time trial or for a sprint distance triathlon, while an Ironman might be raced at as little as 65% of FTP. These can be worked out for you and you can then go out and race to your pre-race percentage of FTP strategy. No longer do you need to spend the entire bike race or triathlon bike leg worrying that you are going too hard or too easy – you are simply sticking to the plan and the plan should get you through in your target time. If you go above your FTP, you ease off; if you go below you go harder.

But remember, you need to build up your power data. If you have only just purchased a power meter, have no data, or have been using it for little more than telling you your speed, you should train and race using you established pacing strategy, whether by experience, heart rate or other, and not even looking at your power. Use the training or racing to collect the data needed to develop your FTP.

I also asked friends whether the meters are accurate. Those I spoke to used PowerTap which measures at the rear hub); or Quarq/SRAM, SRM, Stages and Power2Max which measure at the left or right crank; or Look/Polar and Garmin Vector which measure at the pedal spindle; and there are others which measure at the shoe cleat. All felt their power meter of choice was accurate enough.

The thing which struck me about the different power meter options was not how each one measures power, but how you transfer the device from bike to bike – say from racing bike to winter bike. For example, the power meter can be on a wheel hub, a crankset, a crank arm and so on. Either buy multiple power meters or get used to swapping parts across bikes. Although I haven’t used any of the systems, the one most riders were using was the Stages Power meter (which requires you to install  a left crank arm with a ready fitted Stages device fitted), though, without ever having used one, I like the idea of a pedal or cleat system as these can be changed easily across bikes. As ever, the decision for most people will come down to cost and Stages is currently the least expensive. There is a bit of a price war on at the moment and you can get a power meter at a lower cost than ever before.

But, will I be buying a power meter for Christmas? No. There are still items in my equipment shopping basket which will be purchased before I splash out on a power meter. I think prices will come down and down (they are half the price now that they were a little over 5 years ago), until eventually power metering forms part of bundles like those offered by Garmin (bike computer, heart rate strap, sensors, ANT dongle, etc.). It is still the pioneers buying power meters, not every day cyclists.  If you already have your fully kitted out time trail bike, race bike, winter bike and every bit of gear you need, then a power meter is for you – sure, what else would you be spending your money on. For the rest of us peasants, there will most likely be gear you need more than a power meter (better bike(s), better bike frame(s), better groupset, better wheels, a disc wheel, a Garmin bike computer – you name it).