In the summer of 2019, the new Stryd was launched. This new Stryd has been improved on many points. The most striking improvement is the "wind port". This is a small hole in the bottom - between the charging contacts - so that the Stryd can also include air-resistance in the running power calculation. This is revolutionary!
We were asked about our experiences with the new Stryd after six months. With pleasure, but not without explaining the operating principles and capabilities of this accurate running power meter.
Compared to the new Stryd, we find the previous generation Stryd very useful if it is not too windy. In this case the air-resistance is not negligible, but has a limited impact.
The technical evolution is in the new high-quality sensors for movement and air pressure. Sensors for temperature and air humidity have also been added. For future applications the new Stryd is already equipped with a magnetometer. The objective of this magnetometer is to improve the accuracy with future releases of firmware. Furthermore, the storage capacity has been considerably increased and the battery charging system has been changed. If you want to know more about these improvements, we refer you to product information on the internet.
Stryd is the first running power meter to measure the air-resistance in real time and for use in the power calculation. Garmin Power also has an option to take wind into account in the calculation, but gives a global indication only. The Garmin option requires that your watch has been connected to your mobile phone for at least 10 minutes. This is to get the current weather information. The Garmin determines the air-resistance from wind direction, running direction (GPS) and barometric changes. That’s all.
The Stryd is different. In the clip with which you attach the Stryd to your shoelaces, there is an opening with an air channel to a hole, the "wind port", in the bottom of the Stryd. The operation of the wind port is comparable to the pitot tube used in the aviation industry for measuring the wind speed. As a result, the Stryd measures the current wind situation very precisely and notices immediately when you run in the lee of a group, or behind a row of houses or a grove.
Even without wind there is air-resistance. The running wind or own wind (air-resistance) equals to the running speed in this case. This differs from a treadmill. In this case your body won't move. The air-resistance is zero. Therefore it is much to run on the treadmill than outside. Simply put, you can use the full power of your human motor (heart, lungs, muscles) to run fast. For this reason, a Sports Medical Advice Center will place the treadmill on a 1% to 2% inclination during a test. This is to simulate the air-resistance. The inclination depends on your maximum running speed. If you run faster, the incline of the treadmill is steeper.
The picture shows the warm-up part of Ron 's training last weekend. The pace went around at 6:00/km (10 km/h), the blue line in the graph. The wind was blowing with gusts, according to the weather reports 26 km/h, wind force 4. In the picture from about 3 minutes, Ron encountered full head wind. The air-resistance increased to a maximum of 20% of the running power. In the picture, the air-resistance is recognizable as the gray part between the two yellow power lines. In the picture at 5.5 minutes, Ron turned left (crosswind) and ran into the lee of many trees. The air-resistance dropped there to 4% of the running power.
Theoretically at a pace of 6:00/km we calculated with our running model that the percentages for Ron are 18% (26 km/h, full head wind) and 2% (no wind). Thus the practice measured by the Stryd foot pod corresponds very well with the theory. We saw this earlier during the tests we did with the Stryd in the wind tunnel of the Netherlands Air and Space Center (NLR) in Marknesse.
Wind rarely blows constantly. In the picture you see that the Stryd nicely follows the variation in wind (and therefore in air-resistance) from moment to moment. If you join a group of runners in front of you, the Stryd immediately shows a more favorable wattage due to the lower air resistance in the group.
The resistance factor cdA (in m2) is required for the calculation of the air resistance. This is a term for the resistance surface of an object. This value says something about the aerodynamic shape of a runner. Stryd estimates this from the length and weight you entered in the app.
The Running Model in practice
In cycling, power meters are common for cyclists who are interested in performance. This is where the concept of Functional Threshold Power (FTP) comes from. FTP is the power you can maintain for exactly one hour.
Ron's FTP (80 kg) is currently 292 Watts, so 3.6 Watts/kg. If a race is less than an hour he could run with a higher power (wattage). If the race lasts longer than an hour, such as a half or full marathon, Ron will have to run at a lower wattage. Otherwise he will met the famous “man with the hammer” prematurely.
What percentage of your FTP applies can be determined with our book ‘The Secret of Running’. The Stryd app provides the same for a limited number of distances.
Based on his FTP of 292 Watts Ron is capable to run next wattages for the example distances given.
- 10 K 297 Watts
- 15 K 288 Watts
- 21.1 K 281 Watts
- 42.2 K 267 Watts
Of course we also bring theory into practice ourselves. In past Seven Hills Run (15 K), Ron ran an average of 287 Watts. His time was 1:13:19.
The picture clarifies that these powers cover the running resistance (your pace), the air-resistance (wind), and climbing resistance (uphill or downhill). On flat terrain without wind you get the maximum return from your power. In this case you need a small part to overcome the running wind only. The majority of the power is available for the running resistance, in other words to run fast. Everyone will recognize this. At a flat course with no wind you run your fastest races.
If you run parts in the race faster than the guide value for the wattage at that distance, you use too much energy. Your "fuel tank" is not empty at the finish (which is the intention for the best achievable time), but much earlier. You meet the “man with the hammer” and you are roughly a minute per kilometer slower from that moment. If you run slower than the guide wattage, you have energy left at the finish. And you did not finish in your best time. Furthermore, you have to know that if you have to vary wattage as little as possible to run economically.
So the lesson is: uphill or with a headwind you have to reduce your pace to stay at the guide power (wattage) for that distance. You have to accelerate downhill or back wind to stay on this guide power number. And with headwind, look for a group to take advantage of their shelter.
With the introduction of the Stryd a few years ago, some knowledge of physics and physiology was useful. That is not easy for everyone. Stryd is increasingly responding to this and makes this running power meter accessible to a wide audience. They have, for example smart training plans in PowerCenter. From day to day in the calendar of PowerCenter you can see what's on your program. Simply do what the plan tells you to do.
Based on your performance in the past 3 months, the Stryd app calculates your Critical Power (CP). In the literature, the CP is defined as the ability that you can sustain a certain time. The FTP corresponds to the CP60, the power that you can keep for 60 minutes. Stryd consistently uses your personal determined CP in its applications. Making it easy for you.
Stryd has many more useful parameters and tools for runners at different levels and ambitions. There is much to discover and try. And this continues. The Stryd app has already been improved on several points in the last 6 months. We heard that Stryd PowerCenter will be replaced soon for a more user-friendly release with even more options.
NN Egmond on Sea Half Marathon
The NN Egmond Half Marathon will take place on January 12, 2020. This race is notorious for the wind on the beach. In the dunes it goes up and down hill. It is one of the toughest half marathons in the Netherlands. The race start depending on your starting section at around 12:30 pm.
On January 12, the tide is low and the beach is wide at that time. Provided that you run on the hard and wet part of the beach, the Stryd is a fantastic tool to prevent you from running over.
The Stryd is suitable for hard surfaces. The Stryd cannot handle the extra running resistance due to loose beach sand.
Stryd provides an extra dimension for runners who are interested in improving their performance. The Stryd running power meter is definitely an asset for this target group.
If you would like to purchase The Secret of Running (or the German version, Das Geheimnis des Laufens), you can do so at the bottom of store.stryd.com.
You can check the impact of all factors on your performance in our book: The Secret of Running
The book explains the impact of all factors determining your performance in running step by step: training, nutrition, body weight, running form, wind, hills, temperature, altitude, running gear, power meters and much more. Written in a crystal-clear and lively style, the book is a wealth of information for every ambitious runner. It details how much power you need to surmount the running resistance the air-resistance and the climbing resistance, It shows how power meters can be used to optimize your training and race result.
Both The Secret of Running and The Secret of Cycling are available in print as well as eBook in multiple languages.