What's The Best Metric To Train To?

Your power meter spits out numbers, but there’s a science to making best use of them

- Stu Bowers

Any rider who’s taken even a passing interest in training methods knows that power is the metric that matters.

It’s what the pros use, it’s what coaches recommend and it’s the true measure of your strength and fitness on a bike.

So what do you do? You go out and buy a power meter (at least they’re not as expensive as they used to be) and now every ride comes with a mountain of data that makes about as much sense as a Stephen Hawking lecture on quantum mechanics. And once you’ve downloaded the data, what do all these numbers really mean? It’s time for a crash course in power metrics.

Number crunching

Consider this scenario: you’ve just completed a two-hour ride and while waiting for the kettle to boil you check the power data on your bike computer to see that you’ve recorded an average power output of 200 watts. What does that actually tell you about how hard you’ve just worked?

‘Did you ride at a steady 200W for the entire duration, or did you ride at 100W for large chunks of the ride, interspersed with several intervals of over 300W?’ asks Hunter Allen, director of Peaks Coaching Group and co-developer of renowned online training tool Training Peaks. ‘As far as the average power is concerned the two rides appear equal. But as far as the physiological cost and the likely training effects are concerned, they’re definitely not. Sustaining higher power outputs requires exponentially more effort. That’s to say it’s not twice as hard to maintain 300W as it would be to maintain 150W. It’s considerably harder to maintain the higher number.’