How can you optimize your times with STRYD? In this blog you will learn how I used STRYD to test which is the fastest shoe. Inside on the treadmill, and outside on the road. I obviously used the STRYD, in addition to heart rate and lactate measurement. Spoiler alert: Unfortunately, you cannot use the STRYD to compare different shoes. In the conclusion, you will read what you can use the STRYD for.

Introduction: I am not sponsored by STRYD. I paid for all shoes, materials and testing equipment. This blog is the result of my research into the applicability of STRYD and other measuring equipment in optimizing training and competitions.

What is STRYD?

STRYD is a power meter designed for runners. It measures your running effort in wattage, similar to how cyclists measure their power while cycling. Here are some ways it can help with running:

1. Objective performance measurement: Instead of relying solely on speed or heart rate, STRYD provides an objective measure of the effort you put in. This can help you dose your efforts during training and races.
2. Improve efficiency: By measuring power, you gain insight into the efficiency of your running technique. This can lead to adjustments to improve your running style and prevent injuries.
3. Elevation adjustment: STRYD also takes elevation differences into account, making it a useful tool for adjusting your effort for different terrain and altitudes.
4. Pacing: It allows you to better control your pace during races by providing real-time information about the effort you are putting in. That is often more accurate than your heart rate or speed.

Shoes tested

In my preparation for the Two Rivers marathon 2023 I wanted to know which shoe would bring me to the finish fastest. Four candidate pairs of shoes were selected from my shoe closet. First, the Nike VaporFly Next %2. The second pair was the Under Armour Charged Engaged, a cheap, basic shoe I use for Berts bootcamp. This shoe feels the slowest of all my shoes: this is the antagonist of the Nike. The Hoka Rincon is my previous racing shoe and number three in the order of this test. My favorite training shoe, the Hoka Clifton 8, is fourth and last shoe I have tested.

Test 1: 5x4km on the treadmill

How can you optimize your times with STRYD? I did two tests to find out. The first test was on February 3, 2023, on the treadmill, a calibrated Technogym 700 Excite. During the test, the treadmill was at 0.5% (simulation of headwind). The protocol: run 3km at 12km/h. Then 5 blocks of 4km at 15km/h. During the effort I measured my wattage and heart rate. Between each block I took lactate and changed shoes. That meant a break of 90-120 seconds. Afterwards I did a 2 kilometers cooldown for a total distance of 25km.

To test the effect of fatigue, I wore the Nikes for both the first and last block. In between I tested the Under Armours, the Hoka Rincons, and the Hoka Cliftons.

The table below shows the results.

*spm: strides per minute

**ECOR: Energy Cost of Running, calculated as Watt/kg divided by speed (meters per second)

The results surprised me. I expected that I would need fewer watts for the same speed on the Nikes. Or that I would at least see differences in wattages. What this data mainly told me was that I was starting to get in good shape for the marathon, but not what shoe was fastest.

Test 2: 5x5km outdoors

To test whether there is a difference between data on the treadmill and data on the road, I tested again on February 13, 2023. Now on the road, with blocks of 5km. After all, the marathon was getting closer;) The protocol: warmup for 3km at 12km/h, followed by 5 blocks of 5km at 15km/h. The shoe order was identical to the first test. Between each block I changed shoes and took lactate. Afterwards, walk another 2km for a total of 32km. With great regret, I must admit I have lost the lactate data. Fortunately, the other data has been saved. You can read them in the table below.

Now I was even more surprised. Instead of lower wattages on the Nikes, the STRYD actually indicated higher wattages. The heart rates did vary somewhat, but those differences are within the range of what I normally see during similar training sessions. In fact, I hardly have any ‘heart rate drift’, not even in the last block which I ran after 20km at 15km/h. 

Conclusion: how can you optimize your times with Stryd?

You can certainly optimize your times with the Stryd. However, not by using the STRYD to determine whether one shoe runs faster than the other. I just emailed Hans van Megen, who wrote ‘the secret of running’ together with Ron van Dijk. His answer:

“Your research question cannot be answered with the Stryd. Stryd calculates the power and does not measure it. That calculation in itself is very good. The algorithm does not take into account the influence of the surface and, therefore, also not of difference between shoes. Stryd therefore consistently determines the power as if you were running on a hard surface. Speed, height differences, air resistance (and air humidity and temperature) are properly measured and translated into running power. In your research, speed is therefore the determining factor for the power calculation, but the shoes are not distinctive in the algorithms.”

I am not the first who has made this conceptual mistake. In cycling, you can use a wattage meter to determine efficiency differences between various set-ups, because you objectively measure the power you put on the pedals. The Stryd does not do that: the algorithm calculates the power based on a number of assumptions. If you want to objectively measure whether one shoe is faster than the other, you need to measure oxygen consumption, carbon dioxide production, ventilation and the respiratory exchange ratio (RER), like in this article.

As I wrote in my series of three blogs (1) (2) (3) on the Two Rivers marathon, I appreciate the STRYD for the predictive value of the algorithm do predict times for races. It is essential to feed the algoritme with representative data. This Grand Shoe Test taught me you should run the trainings sessions and races you want to use for a high quality race time prognosis on the same shoes and surface on which you want to run your target event. That is the precondition to use the STRYD for making a realistic raceplan.

PS What shoes did I choose based on both tests? The Nike Vaporflys. Not based on the data in this blog, but based on how they felt;)