Posted in Cycle
Image of PowerTap rear hub

Imagine that cycling is an equation: with input factors like your heart rate, weight, technique and riding conditions, you produce one output factor: POWER. It is power that pushes you forward, power that turns the pedals, power that is the ultimate measure of work done.

Power meters are one of the most exciting and useful tools that an enthusiast cyclists can add to their training arsenal. Whether you are looking to race at a top level or just complete a long distance sportive, a power meter could significantly improve the quality and effectiveness of your training.

The Wiggle Guides are not just for beginner cyclists; in this “Training with Power” series, in association with PowerTap, we take a look firstly at why power is such a good measure to use, then we will look at what sessions you can do with your power meter, both indoors and out on the road.

To accompany this series of guides, there will also be a series of blog posts on Power Training Sessions; these will be short posts detailing how one of our Wiggle staff riders Tim Wiggins is currently using his PowerTap; from winter training to race preparation.

What is Power?

Switching on a computer requires power, moving a car requires power, therefore moving a bike requires power (albeit a fraction of the amount!). Combine power measurements with weight and heart rate, and you’ve got a very good gauge of how good a rider will be. For example, to be in contention, a General Classification rider in the Tour de France will need to be able to do 6W/KG at their threshold heart rate (the point just before you start to produce an unsustainable lactic acid output).

PowerTap G3 Rear Hub

Why is Power good?

For a long time riders rode on heart rate statistics; if they could hold a certain heart rate level then they would consider that to be a good gauge of the effort that they were putting out. Wrong. Heart rate is a good gauge of the effort you are putting in not out; it shows how hard your body is working, however it has some significant limitations in terms of accuracy...

Firstly, heart rate will be lower if your body is fatigued after several days training. Second, heart rate will rise as your exercise progresses in duration, even if the intensity is the same. Third, if you suddenly start riding at a very fast pace, your heart rate won’t instantly rise to reflect this change.

Power on the other hand eliminates many of these limitations. Power will rise instantly as you put more effort into your pedal stroke. Power will not vary with outside factors like temperature, fatigue and duration. Assuming that the intensity of the workout remains the same, so will the power output. The result is that power provides a very good metric to measure the effort that you are putting out, and therefore the pace or intensity that you are riding at.

Combining power with heart rate and weight makes for a superb data set, which allows you to measure not only the work you are putting in (your heart rate), but also the force you are putting out (your power). Increasing your power for the same threshold heart rate, or a reduced weight, will be the ultimate objective of your training.

How do we measure it?

The first power meters that came into production used crank-based measurements, these were effective and reliable, but had a major downside in terms of their lack of transferability between bikes. Recent developments have seen the advent of pedal based power measurement; improving transferability, but increasing the chance of damage in a crash. PowerTap is a wheel based system; the mechanics of the power measurement are housed in the rear hub and transmitted wirelessly to an ANT+ head unit. This has a number of advantages; you can transfer it easily between bikes (assuming your bikes have the same rear cassette), it is a lot cheaper than crank based or pedal based systems, and the hub is kept safe from damage in all but the worst crash incidents (you can always build a new rim or spokes onto a PowerTap hub).

PowerTap ANT+ head unit

The next step

Now that you know what power is, the advantages of it over other performance measures and how you can measure it, we can move onto the next step - how you can use it. In our Part 2 Guide we look at "Outdoor Power Training Sessions"; considering different sessions that will build on your fitness and performance when you are training out on the road with a power meter.

About the author

Tim Wiggins
Published on: 21 May 2015

Tim Wiggins is an avid cyclist, who is involved in all aspects of the sport. Whether it is mountain biking, road racing or riding non-stop for 480km; it is all about life on two wheels.