What is ‘running to power’ and how can it help your pacing problems?

what is running to power

If you’ve ever blown up at mile 20 of a marathon, you’ll want to read this. Running power – new way to assess how hard you’re working when you run – is about to go mainstream and it may just be the answer to all your pacing problems.

That’s a bold claim but bear with us and we’ll explain why. From what it is and the main benefits, to some of the best gear for tracking this new stat, here’s your essential guide to the running power.

What is running power?

Running power, measured in Watts, is a way to measure the output of the work you’re doing when you run. The higher the Watts, the more power you’re generating with every step. The more power your can generate at a lower heart rate or faster pace, the more efficient you are. And efficiency is the secret weapon of fast runners.

Power can be used with a certain degree of accuracy to the reflect the metabolic cost of your efforst and also offers a new way to measure the load on your muscles.

Cyclists have been using power for a long time as a great way to produce consistent performance in both training and racing. But power has taken a while to make its way to running because unlike cycling where you’re working in a fixed position, there are far more biomechanical and situational variables that make it much harder to generate accurate and useful data.

However with smaller and increasingly powerful sensor technology – accelermoters – products are coming onto the market that bring power to runners too.

As with any biomechanical measurement there’s still a healthy scientific debate about how best to measure running power, what’s actually being measured and how to apply it. We’re not going to dive into all that detail here, but let’s just say this emerging technology has some excellent benefits when used in conjunction with existing information such as pace, heart rate and how we feel.

The big benefits of running with power

To understand some of the biggest benefits of running power it’s useful to start by looking at some of the shortcomings of our existing running metrics: pace, heart rate and feel (or Rate of Perceived Exertion RPE).

Despite the fact that as runners we all obsess about pace, it’s actually quite a blunt instrument for training and racing. It doesn’t reveal how hard your body is working, only the results of the work. It can’t cope with hills either. For example, if your coach sets you a tempo run at a certain pace, and you live in a part of the world where you’re surrounded by hills, the chances are you’re either not going to maintain that pace, or you’re going to be working a lot harder than someone who runs the same drill but lives surrounded by flat lands.

On race day, unless you’re running a pancake flat course, adjusting your pace to reflect the elevation is incredibly complicated. And let’s face it none of us is great at doing difficult sums at mile 22 of a marathon.

Then there’s heart rate – a measure of the work your cardiovascular system is doing. This also struggles with hills or rapid increases in running intensity. For example, for track sessions where you’re doing 400m repeats you’ll often see a lag as your heart rate plays catch up with what’s actually happening.

Related: Running, heart rate and what is a 'normal' resting rate 

Similarly if you’re doing hill repeats, it’s quite common to see your BPM readings fall behind. It doesn’t respond in real time and that means you can be working well above your desired rate long before your watch alerts you to it.

Your BPM is also affected by other external factors such as whether you’re stressed, tired, ill or you’ve just had an enormous coffee. As a result, useful as it is in some cases, heart rate isn’t a reliable measurement of your work rate either.

Finally there’s RPE or running on feel. The biggest drawback with this is that we’re all brilliant at lying to ourselves in the first few miles of a race where the adrenaline is pumping and we feel invincible. At this point it’s all too easy to misjudge what’s a comfortable, maintainable intensity for the whole race. Often you only realise you’ve got this wrong when the Struggle Bus comes for you deep into the race.

So how does power help?

Power brings something new to the table, plugging gaps in our data. For a start it responds instantly in real-time with every step.

And because power tracks the actual output rather than your heart’s response to the work needed to produce the output, or the result of that output in speed or pace, it’s possible to get a consistent reading that reflects your work rate whether you’re running on the flat or uphill.

If you run a stretch of flat at 230 Watts and your pace equivalent is 8 minute miles, when that flat turns into a decent hill, in order to maintain a steady 230 Watts, the chances are you’re going to have to slow down. But the work you’re doing to maintain the even wattage will be the same.  

There are some caveats to this. Wind and heat are two external factors that a power metre can’t read, another is softer ground underfoot. Running downhill presents some problems too but on the whole the stats you get are a reliable guide to what’s actually going on.  

Perfect pacing?

One of the most promising practical applications for power is helping to pace races evenly.

The best power-tracking devices offer calculators that let you quickly assess what power you’ll be able to maintain for any distance, certainly up to a marathon.

The Stryd partner app, for example, takes a recent 5k, 10k, half or marathon time, lets you select your target race distance (from the same distances listed here) and then provides you with a target in Watts. This power target – one single number – represents the output you can sustain without busting your threshold and heading for the wall.

what does running power mean?

What that means in practice, is that by sticking to this one number, you can control your race from start to finish without the risk of blowing up. You might even find you have a little more to give in the final miles but you’ll at least be in a position to make that call.

There is an important twist here though. You don’t get to decide your target time. Instead you have to trust that the power target you calculated will give you the race outcome your training deserves. You’re no longer shooting for a time you’ve decided you think is possible and that’s quite a hard concept to grasp.

It shifts the emphasis from what you think you might be able to do to what your current objective fitness will allow you to do.

If you’ve trained well and your race power target calculations are done correctly, you’ll be in with as much of a chance of a PB with a run that’s not wrecked by poor pacing strategy.

Spot improvements in performance

Used in conjunction with heart rate, power is a great tool for identifying improvements in performance. For example, if you repeat the same session two weeks apart and you find you’re running at same power but with a lower heart rate, that’s a sure sign of better efficiency, aka an improvement in your running form. The sames goes for producing equivalent pace to power.

what does running to power mean?

Manage your training load

When you run you’re placing stress on two systems, the cardiovascular system and the muscular system. While heart rate can track cardio load, before power metres we didn’t really have a way to measure the strain on the muscles.

By monitoring power during training runs devices like the Polar Vantage V and Stryd deliver a more holistic assessment of the true training load. That can then be used to prescribe training and rest more effectively.

Zone training

Just as you can with heart rate, it’s possible to generate power-based target zones for the different running states including recovery, steady, threshold and tempo, VO2 Max and speed work interval sessions and repetitions.

And because there’s no time lag with power, you can hit these zone more quickly and more accurately than you would using heart rate. For example you can ensure you’re training in the 80-85 percent threshold zone from the very first 100 metres.

Which products track running power?

Stryd

A pod that clips onto your shoelaces, the Stryd sensor uses motion-sensing accelerometers to measure power from the foot. It works with an app, or hooks up to most running watches, to let you see your power in real time.

RunVI

A set of 100g smart soles with accelerometers and 30 pressure sensors, these inserts slip into your running shoes to capture power readings from each step. These are sent in real-time to a partner smartphone app.  

Polar Vantage V

The first running watch to track running power from the wrist, the new Vantage V estimates power using GPS-based speed and data on elevation captured by its built in barometric sensors. This cuts out the need for additional sensors but the downside to this is that it doesn’t work for indoor runs.

Related: 5 ways the Polar Vantage V could change the way you train

Garmin Running Dynamics Pods or HRM-Run/Tri

Three running accessories from Garmin track power. The dynamics pod is a belt-clipped pod and the HRM-Run and Tri are standard chest straps. Both work with select Garmin watches such as the Fenix 5 and Forerunner 935 via a downloadable a Garmin Connect app.

Related: Where to buy a cheap Garmin GPS running watch