Measuring your Power during running is not something that belongs to a distant future. It's happening now.
In this article I will try to explain all the benefits of using a Power Meter when running. And I do this based on the market's best and most valid Power Meter for running – Stryd Power Meter.
Power meters have the potential to revolutionize the running world in the same way they have done in cycling. There is hardly a serious cyclist who today does not ride with a Power Meter on the bike, right?
Although there basically is a big difference in how Power (Watt) is measured in the cyclist versus the runner, the effect or benefit of training with Power is exactly the same.
And now it is, in my opinion, only a matter of time before all the serious runners also open their eyes to running with power and take the next step in their training.
OVERVIEW
This article consists of the following sections:
- 5 advantages of running with a Power Meter
- Watt pr. Kg - the best indicator of running form and performance
- Why Power is better than Pace and Heart Rate
- Perform at your best with Stryd Power Meter
- Critical power and training zones
- Does Stryd work for trail running?
5 advantages of running with a Power Meter
1. Measure the exact effort / intensity of your training
A Power Meter gives you accurate real-time measurements of how many watts you provide during your run. In this way it gives you a much better and more accurate picture of how hard you actually work. Far better than Pace and Heart Rate, which most people use today.
2. Achieve "perfect pacing" under all conditions and perform optimally
It is well known that the best performance is achieved if you can maintain a steady, even load throughout your run. If you start out too hard, you will struggle big time towards the end. If you start out too slowly, you will not be able to make up for the time you’ve lost.
External factors such as hills and wind naturally play a role in how fast you can run. But with a Power Meter you can keep a "constant effort" and thus run at the most optimal pace, no matter how much the wind blows, or how much it goes uphill or downhill. The Power Meter indirectly tells you how much you need to slow down and how much you need to speed up, to keep a constant / even effort when conditions change. In this way, the Power Meter can help you perform optimally.
3. Optimize your running running economy
A Power Meter can tell you exactly how much Power you use on each of your runs and thus also how "economical" you are, when you run. When you change factors that have to do with your running style (eg. cadence, stride length, bounce, lateral movements, etc.), you can use the Power Meter to determine if your changes have a beneficial effect on your running economy or not.
4. Measure your running form and ability
With a Power Meter you can measure your FTP (Critical Power / Anaerobic Threshold) and estimate your V02 Max on your own - without performing advanced laboratory tests. Therefore it’s possible to follow how your form develops.
5.More accurate than the GPS in the running watch or mobile
The built-in accelerometer in the Power Meter of Stryd measures exactly how your foot moves, and you can therefore expect distance, speed and altitude measurements that are not affected by bad weather, dense forest, rapid changes of direction and sharp turns, as is the case with GPS. It also allows you to rely even more on the real-time measurements you see on your running watch (if you use one).
What is Power (Watt)?
Power is measured in Watts and is an expression of the Work per. unit of time that you perform, when you run. The higher the wattage, the more power you generate in each step. And the more Watts you can generate at lower heart rate, the more efficient you are.
Power (Watt) is in other words a measure of how hard your body works. And it is far more accurate than HEART RATE (BPM) and PACE (min / km), which for many years have been our best parameters in terms of assessing the effort / load of each run.
Later in this article I will come up with a few examples that show why it is better to train after POWER compared to training after PACE or HEART RATE.
Although it may sound very complicated, it is actually much simpler to train using "Power Zones" than to train using Pace zones or Pulse zones, so there are all sorts of good reasons to start running with power.
What is Stryd Power Meter?
Stryd is a small foot-pod (weighing only 8 g.), that is clicked onto your running shoe. It gives you accurate Power measurements, which you can use to control the intensity of your running.
When you run, Stryd can take into account your running speed, your shape, the slope of the road and the wind, and thus provide "PERFECT PACING" on all your runs. It allows you to train at the most optimal intensity and thereby achieve the greatest possible performance improvement.
Perfect pacing with Stryd Power Meter. Maintain an even load regardless of terrain and wind conditions.
The Stryd Power Meter contains an accelerometer (which measures acceleration in all directions) as well as a pressure sensor used to measure wind resistance. In addition, the Stryd pod also includes a temperature and humidity sensor.
There is a small hole in the front of the Stryd unit. Through this, the wind resistance is measured.
There is nothing revolutionary in the technology in the Stryd unit itself. The real breakthrough on the technological front lies in the software that in a complex algorithm processes all data to provide accurate Power measurements in real-time.
Stryd is connected to a running watch and / or smartphone
To get the most out of the Stryd Power Meter, it requires a compatible running watch so you can see your Power numbers in real-time while running. Stryd works with all the major sports watch manufacturers: Garmin, Coros, Polar, Suunto and Apple. Here you can see the full list of watches that are Stryd-compatible: WATCHES THAT ARE COMPATIBLE WITH STRYD
Coros is currently the watch manufacturer on the market that is best integrated with Stryd and that allows you to view all data directly on the watch. The setup on Coros is super simple and very intuitive.
Garmin Fenix 6 Pro Solar with Stryd Workout App.
Garmin is the second best integrated watch manufacturer with Stryd. Here, however, the setup is a bit of a hassle, as you, among other things. need to download an additional app for the Garmin watch to make it work together. But once the setup is in place, it runs smoothly.
Stryd is also compatible with the most popular training platforms such as TrainingPeaks, FinalSurge and Zwift.
If you do not have a running watch, you can also use Stryd together with your smartphone and register the run directly on it. The actual measurement of the run works impeccably in this way, but since it is hugely impractical to run with a smartphone in your hand, you miss the most ingenious feature of Stryd - namely that you can get Pacing in real time while running.
What does Stryd measure?
In addition to measuring Power (Watt), which is the most important parameter, Stryd can also measure: Form Power, Ground Contact Time, Vertical Oscillation, Cadence, Leg Spring Stiffness, Wind resistance, Pace and Distance.
Stryd is more accurate than GPS
On your Garmin or Coros watch you can choose to use the watch's GPS or Stryd to measure distance and speed. I would highly recommend having Stryd measure both as it is more accurate than the watch's built-in GPS.
Watt pr. kg - The best indicator of form and performance
If you divide a runner's power output by the runner's body weight, the unit Watt / Kg is obtained.
According to Claus Hechmann (who is a very recognized Danish running coach and guru within Power training), and several other wise people in the field, Watt / kg is an expression of Running Economy, which we all need to get used to using.
There is a linear relationship between running speed and Watt / kg, as you can see in the graph below.
Note that the graph is valid for running on a treadmill – ie. without wind resistance. The wind resistance increases the faster you run, and therefore the relationship is not completely linear when the wind resistance is taken into account. Credit: Claus Hechmann.
The more Watts / kg you as a runner are able to produce, the faster you can run.
So if through your training you become able to produce more Watts (at the same heart rate) or you reduce your body weight by losing weight, then you can run faster. Simple as that.
Watt / kg is thus probably the best indicator of form or performance that we have. Far better than eg. VO2max, which many may know from their Garmin watch or similar. There is an important endurance aspect in running that the VO2max value does not take into account. Watt / kg does, on the other hand.
Based on a lot of tests and a lot of calculations, the authors of the book, The Secret of Running, have developed a table that illustrates Watt / kg for different categories from the untrained runner to the elite runner. You can see it below.
Table from The Secret of Running p. 121, 2017, by Hans Van Dijk and Ron Van Megen.
The “Watt / kg”-values given in the table are the number of Watt / kg that a given runner can sustain for a maximum of 1 hour. So if you as a male runner in one hour can run with an average W / kg of 2.6, then you are untrained. On the other hand you belong to the international elite if you can run with 6.1 W / kg in one hour. The value in the table is called FTP (or in Stryds universe: Critical Power). This parameter is explained in more detail in the next section.
Critical Power / FTP / AT
Functional Threshold Power, better known as FTP, is another parameter that is of great importance in Power training. It is a measure of the maximum power output (measured in: Watt / kg) that one can sustain for one hour. This means that you run 1 hour All-out (as fast as you can) and note the average Watt / kg. That value is your FTP.
This also corresponds to a person's AT (Anaerobic Threshold), and it is a super important parameter to know if you want to optimize your training, as most training zones are calculated based on FTP / AT.
STRYD calls the same parameter CRITICAL POWER or CP, but all these parameter-names do in fact cover the same thing - namely the maximum effort you as a runner can sustain for 1 hour (measured in either Power (Watt) or Pace (min / km) or Heart Rate (beats / min)).
At the end of the article, you can read more about how to find your Critical Power / FTP / AT, and why it is extremely important to know, if you want to get the most out of your training.
Why Power is better than Pace and Heart Rate
Power (Watt) is, as mentioned, a direct measure of how hard you work. There is, contrary to heart rate measurement, no delay in the measurement of Watt. Your power output changes as soon as a change occurs on your run. So when you start running uphill or you turn a corner and suddenly run in headwind, the Power Meter can instantly tell you how much extra work you are doing now, and thus also how much you have to slow down the pace to avoid hitting the wall.
If you run on pancake-flat roads on windless days, then it is just as good to use PACE as to use POWER. But when it is windy, or when the route is hilly, then it is impossible to use PACE or for that matter Heart Rate, as a guideline in your training. In the following sections, I will give you some examples of this.
Running in hilly terrain
When you run in hilly terrain (ie where it goes a lot uphill and downhill), and you want to keep a steady intensity throughout the run, it will be better to run using POWER than to run using PACE as a guide.
If I try to keep the same running pace uphill as I have done on flat roads, then it almost goes without saying that it will get a lot harder, when I run uphill.
The table below shows how much harder you have to work when running uphill. On a hill with a gradient of 6%, for example, an extra 50% effort must be done compared to running on a flat road.
So if, for example, I run at a pace of 4:00 min/km on a flat road (corresponding to an output of approx. 300 watts at my feet), and I hit a hill with a 6% incline, then I now suddenly have to increase my power output with 50% to a full 450 Watts (!!) to be able to keep the same speed up the hill. It's a massive increase - and it's not so strange that you have to slow down to avoid rapid fatigue.
Below I show an example where I ran up and down a long hill where my focus was on keeping the same intensity all the way. I therefore kept an eye on the Power measurement on my watch and tried to keep a fairly constant value all the way.
I have taken the graphs from Trainingpeaks as it is easier to view all data at once here. But I could have basically seen the same thing in Stryd Powercenter, which is Stryd's answer to Garmin Connect.
Running up and down a long hill
The pink curve is POWER (in Watt), the green is PACE (in min/km) and the red is Heart Rate. The dark gray area shows the hill that I ran across.
On flat road I provide 258 W which gives a pace of 4:42 min / km.
As I move up the hill I naturally need to slow down my running pace to continue with the same intensity. Here you can see that due to the steepness of the hill I am actually slowing down a lot to keep the same intensity. At 259 W I now run 5:47 min/km!! In other words, a sharp decrease in speed.
On the flat hilltop I again run roughly the same pace as at the bottom of the hill, namely 4:35 min/kg at 254 W.
Downhill of course I have to run faster to keep the same relative intensity or load. And it can be seen from the graph that I run down the hill with 258 W (ie the same intensity as on a flat road and up the hill) with a pace of 3:49 min/km.
So I used the Power Meter to keep an almost completely constant effort on my run across the hill. The Power Meter has indirectly told me EXACTLY how much I need to slow down or speed up to keep the same load / intensity. Pretty ingenious if you ask me.
When you look at the graph, you can see that the Heart Rate is kept very constant, which of course also emphasizes that the load has actually been completely even.
But can I not just use my heart rate as a guide when I run in hilly terrain? - one might be tempted to ask. And yes, you can do that in principle well. As long as you make sure to use a heart rate belt around your chest - in many cases the heart rate will be a sensible guideline ... As long hills or climbs are long and with pretty constant steepness. The Heart Rate needs a relatively long time before it adapts. There is, as previously mentioned, a delay in the heart rate measurement, as the body cannot adapt in a split second to the increased load, which you expose it to by starting to run uphill.
You can see this illustrated in the next example.
Fast running on a steep hill
In this example I ran up a relatively short but rather steep hill. This time, I did not look at the Power numbers, but instead tried to keep my pace from flat road all the way up the hill.
On flat road I ran 4:07 min/km at 269 W and a heart rate of 142.
Approx. midway up the hill I had already slowed down a bit to 4:17 min/km, but the Power number has rocketed all the way up to 394 W.
It was extremely hard to run up the hill at that pace, and I was completely exhausted before I reached the very top - which can be seen by the Pace dropping and the Power number also dropping before I reach the top.
My Heart Rate increased from 142 beats/min on a flat road to 152 beats/min, when I approx. 45 seconds later reached the top. But the small increase in heart rate does in no way reflect how hard it was. I usually have a max heart rate of over 190 beats/min. And if I had to describe how it felt to run up that hill, then I was very close to the maximum intensity that I can sustain. The Stryd Power Meter clearly shows that with a peak of 394 W, while the heart rate measurement (or my pace measurement for that matter) in no way reflects how hard it was.
The Power number is actually the only parameter indicating that I have worked significantly harder up the hill than I did on flat road.
These two examples illustrate that you need a Power Meter if you want to be able to control your training intensity in real time, or you just want reliable measurements of your training load when running in hilly terrain.
Stryd measures wind resistance
It is not only hills (hilly terrain) that affect your training load. THE WIND also plays a big role. And the Stryd Power Meter can also take that into account.
As mentioned earlier, there is a pressure sensor in the Stryd unit, which can detect the wind resistance.
Everyone knows, that it's harder to run in headwinds. In order to maintain an even and uniform load, you must therefore reduce your running speed, if you want to avoid overloading when turning into the headwind. Stryd is the tool that can help with this.
In the real-time power measurement, which I can see on my watch while I run, both the slope of the road and the wind resistance are included. So there is nothing to worry about while running. Subsequently, in Stryd Power center you can see how much the wind has contributed to the total Power output.
Below you can see data from a run where I started running in headwind for the first 4 km, after which I turned into crosswind / tailwind.
The contribution of the wind to the total load is indicated in the column "Air Power" on the far right. Here you can see that the first 4 km of the run, I had to provide 4-6% more watts (to overcome the headwind) as compared to calm weather.
Perform your best with Stryd Power Meter
Regardless of wind, weather and terrain, the Stryd Power Meter tells me EXACTLY how much I have to slow down when I hit a hill - and conversely, it also tells me exactly how much faster I have to run when it goes downhill.
I actually do not have to worry at all about what pace I should run at. In my training I just have to concentrate on running in the "power zone" that I have decided on in the given training session.
So where I used to run a session called 3x10 min at 3:50 min/km, I now run 3x10 min at 305 Watt instead. And then I do not care if it goes uphill or downhill or if it is windy or not. I know I am loading my body in the same way as if I was running 3x10 min for 3:50 on a pancake flat road in windless conditions.
After some time, Stryd can estimate how many Watts you will be able to perform over different distances from 1500 m and all the way up to 50 km. It also calculates your expected finish time on the various distances. So on the day of the race itself, you just have to try to stick to the specific Power value - then you will run at the most optimal speed on all parts of the route, and thus you will perform optimally!
Here you see how Stryd assesses my current performance in marathons. According to Stryd's calculations, I have to run at 277 W during the entire race to perform optimally.
Critical Power and Training Zones
Most runners who are serious about their running train according to Pace (min/km or min/mile), as it is the most tangible, and the absolute easiest to relate to.
Most runners can relate to whether 4:00 min/km is fast or slow, but what if I say 300 Watts? Is it hard or easy?
The answer is, that it is very individual, as it is in fact the unit “Watt/kg” that decides whether it is hard or easy.
Therefore, it is important that you know your Critical Power and your Power training zones before you really start running with a Power meter. You need a "reference frame" to make the Watt numbers make sense.
As long as you do not know your Critical Power, it is quite limited what you can use a Power meter for. Without a set (and accurate) Critical Power, the wattage numbers that the Power meter spits out are just some diffuse numbers that you can’t really use. Of course you can see how many Watts you perform on the run. But without a reference frame in the form of some updated training zones, it is not very useful.
Later in this article you can learn how to find this Critical Power and determine your training zones.
Training zone examples
Whether you run according to Power, Pace or Heart Rate, there is a broad consensus that you need to stimulate the body in different training zones, based on your current form level, in order to become a better runner. STRYD works with 5 training zones, which you can see below. CP stands for "Critical Power" (FTP / AT).
And here you see my current Power zones:
However, there are many, many other ways to do these training zones. Claus Hechmann, who is a recognized running coach and a guru within running and cycling based on Power (Watt), uses, for example, 9 training zones.
The 9 zones are structured as follows:
4 aerobic zones, 4 anaerobic zones and the AT zone.
The zones are defined as follows:
Jog - recovery
Ae1 - light aerobic intensity
Ae2 - moderate aerobic intensity
Ae3 - high aerobic intensity
AT - the maximum pace you can keep for an hour (threshold training)
An1 - long intervals corresponding to one's 10 km pace
An2 - medium intervals corresponding to 5 km pace
An3 - short intervals corresponding to 3 km pace
An4 - sprint / maximum intensity
In order to determine these training zones (whether you use STRYD's or Hechmann's or somebody else’s zones), it is absolutely essential that you perform a "self test". The idea with these training zones is that they should reflect your current fitness level, and therefore you need to perform a test.
The purpose of such a "self-test" is to get an estimate of your Anaerobic Threshold also called "AT", FTP, or as in STRYD's case, CRITICAL POWER. The most accurate method of organizing your training zones is based on the individual runner's AT.
AT / FTP / Critical Power is an expression of the maximum intensity that the runner can maintain for approx. one hour. It is an expression of the speed / intensity at which the muscles no longer burn fat, but only carbohydrate. At this level, the body can no longer transport oxygen fast enough to the muscles, and thereby the body transitions from primarily receiving energy from aerobic processes (with oxygen) to now to a large extent using anaerobic processes (without oxygen). When this happens, there will be an accumulation of lactic acid (lactate) and fatigue will happen rapidly.
How to perform a self-test
After a few runs Stryd will come up with a guess on your current Critical Power. Stryd has a so-called "Auto-Calculation" function, which based on your runs estimates your Critical Power automatically.
Unfortunately, my experience is that Stryd takes a very long time to arrive at a reasonable value if you just start using Stryd on your normal runs.
Stryd needs to know your maximum performance over a wide range of distances to come up with a qualified estimate of your Critical Power. With the latest software update, a number of suggested tests are now available in the Stryd Powercenter App, which you can perform during the first weeks of running with Stryd. Or if you want to update your zones. This will improve the calculation of Critical Power a lot!
However, these tests are covering fairly short distances, and therefore there is also a need to do runs that are significantly longer. If you are a relatively trained runner who can keep running long and fast, then it makes very good sense to run a 1 hour all-out test. That is, where you run as far as you can in 60 minutes.
It is also an option to turn off auto-calculation, and instead use Claus Hechmann's highly validated self-test, which you will find here.
There is a "10-60 minute test", which is the most accurate, but which is aimed at the trained runner.
There is also a "3-9 minute test", which everyone can perform, and which also gives really good estimates.
Apart from the fact that these tests are some of the most accurate self-tests that exist, the advantage is that after performing the test, you can enter your results in the running calculator and have your personal training zones calculated. And then you are ready to start training!
You even get your zones in both PACE (min/km), Heart Rate (beats/min) and POWER (Watt).
After performing these self-tests, you will receive an AT Power value, which you can enter as your Critical Power in STRYD's universe, and then you will generate the 5 Stryd training zones from here.
Training planning
Optimal training planning is a whole chapter in itself, and I can not go more into detail in this article. But what you need to get to, are basically these 5 "power zones":
My 5 training zones in Stryd.
Or the 9 training zones that Hechmann uses:
My 9 training zones according to Hechmann.
To improve as a runner, make sure you stimulate your body in all these zones from time to time. However, the majority of your training should take place in the slowest zones. Variation is the key to improvement.
Does Stryd work for trail running?
Stryd basically works really well for trail running, and you can use Stryd to pace yourself in exactly the same way as when you run on the road. However, there are a few exceptions where Stryd does not work optimally.
If you run in terrain that is so steep or challenging that you have to walk, you will see different Power values than you are used to. The mechanism behind running and fast walking is very different, as during walking you do not have a flight phase, where both feet are in the air at the same time. As a result, the Watt numbers will be significantly lower when you walk (even if you move at the same speed as during running). However, by using Stryd for trail running over a certain period of time, you will soon get a good sense of how many Watts you can perform over a given period of time – whether you are walking are running. So Stryd is certainly also valuable when you walk, you just can not use your Critical Power and the training zones that follow since they are based in your running performance.
Another challenge with Stryd arises if you run where the surface is very soft. It goes without saying that it requires a greater effort if you want to run at the same speed on soft surfaces (such as sand) compared to hard surfaces. However, due to the soft surface and the resulting longer ground contact time, Stryd will (at least from my experience) give you a lower Power measurement. It will therefore assess that it is less hard, even though in reality it is harder.
If you run most of your runs on soft and varied surfaces, it may therefore be a good idea for you to perform your Critical Power tests in exactly this terrain. That way, your Critical Power and your training zones will fit the terrain you are running in.
STRYD Membership
When you buy a STRYD Power meter, you get 6 months free access to the STRYD Membership.
Here you get access to the Workout Library, which contains a wealth of power-based training programs and running workouts that you can follow. You also get access to Workout Builder, where you can build your own workouts.
After the 6 months, you can choose to continue the membership. But you can also easily continue without the subscription and get lots of enjoyment from your Stryd device. Here you can see the difference between Membership and Data Only (free).
