Power Meters

Power Meters

If you’re serious about improving your cycling – and you have a chunk of cash you don’t mind spending – a power meter is just about the best investment you can buy. Once the preserve of the professional athlete, competition in the market has reduced prices so that they’re now affordable for us mere mortals. Not only can you use it to make sure you train to your full potential, but you can also use it to pace the bike leg of a triathlon perfectly. That way, you’ll know you have enough energy left to put together a storming run and finish your race strongly.

What is a Power Meter?

It might sound obvious, but a power meter measures the power output of a rider. This is a combination of force and angular velocity. Don’t worry about those technical terms. A simplified way to think about it is that a power meter measures how much force you’re putting into the bike to make it go forwards. The power is measured in watts, just like the power generated by electricity.

What are the Advantages of a Power Meter?

  • The data a power meter produces is accurate and objective. If a training session asks you to go at 8/10 effort, you can fool yourself into thinking you really did go hard, even if you slacked off. However, if a session asks that you hit 250 watts, there’s no fooling the power meter.
  • You can judge effort no matter what the circumstances. You might hit 25mph on a straight road with the wind at your back. On a slight incline, facing a headwind, 15mph might seem barely achievable. A power meter can show you whether that’s the case. It might take 200 watts to hit those speeds in each situation – they really are comparable efforts!
  • You can measure an input, rather than an output. Perhaps you’re currently using a heart rate strap and basing your training sessions on that data. Whilst helpful, this data isn’t ideal. Heart rate is an output of exercise – you work hard, and this causes your heart rate to increase. Power, on the other hand, is an input. The power you create with your legs causes everything else: that rising heart rate, your speed on the bike, your temperature increasing… Power is the foundation of everything else.
  • No time-lags. There’s a delay in your heart rate rising when you put in a big effort. If you’re asked to perform a thirty second all out sprint, your heart rate probably won’t get going for fifteen seconds. How do you know you’re going all out? There’s no lag with a power meter – you’ll know exactly how hard you’re working right from the off.
  • Use it on race day. After months of training, you’ll know exactly how long you can hold certain power levels. Perhaps you can hold 180 watts for an hour. You can take that information and use it to plan a race. An Ironman bike leg might be raced at 70% of that hour-long power output. On the day of the race, you’ll know to keep your average power around 126 watts, and still be fresh off the bike. A power meter can stop you going out too fast on your big day. After all, and Ironman doesn’t really start until mile twenty of the run!

Types of Power Meter

There are myriad options for those looking for a power meter. The best place to read reviews is DC Rainmaker. Every year he publishes a complete guide, and this year’s is fantastic. In short, there are a few options about where the power meter can be placed. The most popular seem to be: 1) the crank arm; 2) the pedals; 3) the chain ring. Personally, I’ve gone for a pedal-based system (the Faviro Assiomo Duo) so I can swap the power meter quickly between bikes. However, there are well-rated systems at every position.

Some of the most popular brands to look out for are: PowerTap, Garmin, Quarq, Stages, and 4iiii. That’s not to say other brands aren’t creating great products as well. Seriously, check out the guide linked above!

What Next?

If you’ve decided to shell out (and they are still quite expensive), you’ll want to conduct an FTP test. This is warm up followed by an all-out twenty-minute effort. You should be utterly broken afterwards. Take the average watts from interval and find 95% of it. That’ll give you your functional threshold power. You can think of this as what you’d be able to hold for an hour when you’re at your freshest. From this number, you can plan accurate, structured training that will make you a better rider so long as you’re consistent.

For more information on training with power, check out my previous guide to the topic.


Conor McGloin


  1. Mark

    Interesting. Does the same hold for running?
    What do you think of Stryd?

    • Raymond McGloin

      Drills, 10% rule, 80 – 20 rule polized training,recovery, tapering, nutrition and a plan hold for all – cycling, swimming and running. I haven’t used stryd yet but if it is faithful to these elements I have written about and helps it promote good form while improving speed then I am for it.


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