Riding with a power meter gives you a load of new data metrics that you can analyze to improve your training. But what do they all mean?
Let’s be honest: A power meter only makes sense if you are willing to look at the information it provides. Analysing your workouts will give you valuable insight, but first, you need to know what the power training metrics actually mean.
Average power is simply the average power of your entire ride. This seems like a fair measurement, but it doesn’t account for the highs and lows of the ride and the physiological cost. Many cycling computers have non-zero averaging turned on, meaning that it doesn’t account for coasting. We recommend that you turn non-zero averaging off, as it leaves a false impression of your effort.
Normalized power (NP) is an advanced metric that accounts for changes in the effort during the workout, which gives you a more realistic representation of the physiological cost of the ride. NP gives you an estimate of the power you could’ve sustained for the same physiological cost for a given workout if your power output had been absolutely smooth rather than jumpy.
Weight to power ratio is a key metric in cycling. Two riders of different sizes can have the same power output but would go at different speeds because one rider is heavier than the other. The more power you produce and the less you weigh, the faster you go! If you want to win the yellow jersey in Tour de France, you should probably shoot for an FTP of 6.5 w/kg or more!
How steady is your power output? The more spikes of power you have during your ride the harder and more fatiguing it will feel. VI is simply NP divided by AP. A Variability Index of 1.0 is a very smooth ride. This is a very important metric for time trialists and triathletes where pacing is key.
Intensity factor (IF) is simply a measure of how hard a particular ride or interval is, relative to your threshold power. Normalized power divided by your current functional threshold power. IF is especially useful to check if your last ride was within the desired spirit of the workout. An IF of 0.75 or below is a recovery ride. 1.0 or above is very hard.
TSS measures the workload of a ride based on duration and intensity (IF). It’s about how much training stress you accumulate and how much rest you will need to fully recover. Coaches use TSS to quantify fitness and fatigue over time. A TSS of less than 150 doesn’t require much rest, whereas +400 TSS indicates several days of rest before you’re fully recovered.
Left / right balance measurement is fairly new in power meters. How much power do you generate from your left leg compared to your right leg? This is a pretty cool feature, especially if you can figure out how to use this data to improve your efficiency as a cyclist. But it’s not as simple as just looking at your average L/R balance after a ride. Your left right power distribution changes throughout your ride based on various circumstances like standing efforts, high & low cadence. It’s about finding any weaknesses so that you can work on them.
Pedal smoothness is a measurement of how evenly power was applied throughout your entire pedal stroke. A value of 100%, however unlikely, equals to a perfectly smooth pedal stroke. The pedal smoothness of 20-50% is common. Try to focus on improving your smoothness by doing isolated pedaling drills. Improving your pedaling technique will lead to a better and smoother power output.