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What you should look for in your running power data

It was only a matter of time before power data spilled over from cycling and into the running world. It’s no surprise – there is significant overlap between the two sports, especially in maximizing efficiency and endurance.

But, for those of us still running with a stopwatch and nothing else, what is running power?

It’s measured in a variety of ways from a handful of companies, but essentially running power is the measurement of how much work you’re putting in while you run. Running power is defined as a watt, and the more watts you produce, the more power you’re generating.

To put this relatively new running metric into context, we caught up with Hans van Dijk and Ron van Megen, authors of The Secret of Running. They’re experts in analyzing training data and researching ways to use power metering effectively. Here, they explain how to do a post-training analysis on running power — basically what you should look for in the data to help you improve.

Hans and Ron cite that Functional Threshold Power (FTP) and Energy Cost of Running (ECOR) are the two most important metrics that determine your running power and performance. The combination of the two can help optimize training in real time and on a daily basis.

First, what is Functional Threshold Power (FTP)?

In its most basic form, FTP is the most amount of power (in Watt/kg body weight) you can hold during the span of an hour. Once you know your FTP, you can determine how much power you can sustain for different timeframes, like 10-minute tempo runs or 120-minute long runs.

“As an example, I have a net FTP of 4.31 Watt/kg (as measured by Stryd) and a gross FTP (as measured by Polar) of 5.6 Watt/kg, so I can maintain a speed of 15.2 km/h during one hour,” says Hans.

Know that your FTP will change depending on how fit you are and where you’re at in your training regimen. This power-time relationship should be monitored to see if all your training efforts are positively affecting your fitness.

“If all goes well, your FTP should increase and so should your speed,” says Hans. “If not, you should change and optimize your training program.”

Now, what is the Energy Cost of Running (ECOR)?

The Energy Cost of Running is all about efficiency. The lower the ECOR value, the faster speed you can maintain at the same power. You can check this on a daily basis with a simple formula — divide power (in watt/kg) by your speed (in m/s).

Note this value will be different between different tools, and if you’re using a Polar Vantage V, this number will be slightly higher than with a Stryd power meter. Also, this number is highly variable between athletes.

Ron van Megen mentions that ECOR depends on many factors, including body posture, fuel mix and running form.

“Generally, it is believed that the net ECOR of highly efficient elite runners could be as low as 0.90 kJ/kg/km, whereas the ECOR of inefficient joggers could be as high as 1.10 kJ/kg/km,” says Ron with numerical examples based on Stryd power data (numerical examples based on Polar data will be higher). “Obviously, a lower ECOR means that you’re running more economically and consequently you can run faster.”

So what can we do to lower our ECOR? Let’s take a closer look at Hans’ and Ron’s three factors:

  • When it comes to body posture, losing excess body fat can help lower your ECOR.
  • Next, fuel mix can be influenced by a proper diet or carbo-loading — but this has limited effects.
  • The most impactful way to hit lower ECOR numbers is by optimizing running form.

“Many factors are thought to influence the running form, including cadence, GCT, stride length, vertical oscillation, arm drive, foot strike, hip angle, knee lift, leg stretching, calves lift and ankle angle,” says Ron. “However, opinions differ on exactly what constitutes the best running form — we found that the ECOR could be reduced by increasing the cadence.”

Analyzing your power numbers on a regular basis can help you become a faster, more efficient runner.

These numbers can help you quantify your running economy, systematically improve your running form, help you optimize efforts and help you plan long term for fitness peaks.

The key is to record power data over a long period of time to give yourself a large enough sample size to notice trends or performance changes.

To learn more about running with power, check out The Secret of Running, or try training with running power for yourself with the Polar Vantage V.

*Note: Polar does not claim that running power can be used to determine running economy. This is because running economy is, by definition, measured as oxygen consumption per travelled distance and running power is not a substitute for rate of oxygen consumption.

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Please note that the information provided in the Polar Blog articles cannot replace individual advice from health professionals. Please consult your physician before starting a new fitness program.

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