Testing Methodology

Find out how we test shoes and how our testing methodology has evolved over time (and we keep improving it).

How we test shoes

1. We always test in men's US 9
2. Conditions are always 20°C/68°F ± 1°C and 55% ± 5% humidity, in both our lab and storage
3. We follow ISO, SATRA, and ASTM standards where applicable. We modify these standards to account for recent developments in footwear science and we also develop our own standards. 
4. We wear test all shoes
5. You can see shoes that we’re currently testing in the lab on our shoe pipeline page.

Here, you will learn how we decide which shoes we buy next, where we store them, why we cut them in half, why we freeze shoes, why it is important to stick to World Athletics’ guidelines, and much, much more. 

Why we perform both wear tests and lab tests

To ensure the highest level of objectivity, we personally test shoes in the appropriate surroundings - whether it’s a street road, gym, hiking trails, basketball courts, track, etc., and we also cut the shoes in half and put them through numerous tests in the lab.

This way, we can discuss how the shoe actually feels and performs and back that up with 30+ lab data points. A caliper in the lab can tell us how thick a tongue is or how stiff a heel counter is, but it can’t tell us whether those materials itch. That’s where our personal experience comes in. 

Why we cut shoes in half

Shoes come in pairs. One shoe we keep whole. The other one we tear apart by first cutting its upper so that it's completely detached from the bottom and then using a band saw to cut the midsole in half lengthwise. We do this because some tests need a shoe to be cut in half for them to be properly done. And because we are meticulous. 

When the upper is detached from the midsole, we perform the energy return and shock absorption tests. Once the midsole is cut in half, we measure the heel and forefoot stack heights (which allow us to calculate the heel drop) and the softness of the midsole. Measuring the stack heights on whole shoes would go against the World Athletics standards and common sense.

The black lines visible on the midsole mark 12% and 75% of the shoe's internal length, which is exactly where we measure the heel and forefoot stack height and where we test the energy return and shock absorption.

Tests that we perform on a shoe after its upper has been cut out or its midsole cut in half: 

• Energy return
• Shock absorption
• Forefoot and heel stack height. Using these 2 numbers, we calculate the heel drop
• Softness of the midsole at room temperature and in cold weather. We even wrote a comprehensive guide about this called Why cutting running shoes in half is key to measuring midsole softness
• Insole and tongue thickness. 

How we measure stack height and heel drop in the lab

To get accurate measurements of the forefoot and stack height, we honor the official guidelines from World Athletics. These guidelines are clear:

1. The stack height must be determined at the exact center of the shoe rather than the sides.
2. Heel stack height is measured at 12% of the shoe’s internal length. 
3. Forefoot stack height is measured at 75% of the shoe’s internal length. 

To achieve this, the shoe must be cut in half. After measuring the internal length, we mark both places on the foam itself at 12% and 75% of the length. You can see the straight lines in our images, it’s where we pressed our caliper to measure the heel stack height and forefoot stack height. 

The heel drop is simply calculated: (heel stack height) - (forefoot stack height) = heel drop. And for us, it is that simple, thanks to our accurate measurements of the forefoot and heel stack height explained above. 

We went down the rabbit hole, of course, and wrote a very in-depth guide: How brands' heel-to-toe drop measurements differ from reality. Spoiler alert: no brand provides accurate heel-to-toe drop measurements! This gives even more value to our test because you can always rely on it. 

Why we put shoes in the freezer

Because we want to know what happens at winter temperatures. All of our other lab tests are done at room temperature. Putting the shoe in the freezer for 20 minutes allows us to simulate cold weather. Thanks to this setup, we’re able to tell how the shoe behaves in cold weather - how flexible and soft it is. 

After the shoe has spent 20 minutes in the freezer, we use a durometer to check the softness of the midsole. We then compare this result to the one done at room temperature. 

If you’d like to learn more about how shoes behave in different temperatures, head over to our guide Effects of temperature on running shoes.

What we destroy with our Dremel and why

We use our Dremel to assess the durability of different parts of the shoe. We press it against the toebox, outsole, and heel padding.

Given that all of our tests are standardized, we always apply the same force and speed. 

The durability of the outsole is correlated with the depth of the dent the Dremel has made. We measure the depth using a tire tread depth gauge. 

When checking the durability of the toebox and heel padding, we visually assess the damage and assign it a 1-5 rating, where 5 is the most durable. 

In this example, we pushed the Dremel against the upper. On the left: Nike Lebron NXXT GEN got the 3/5 rating for the toebox durability. On the right: Nike Lebron Witness 7 with a 1/5 rating (the least durable).

Above, we can see how PUMA Magnify Nitro 2’s heel counter is destroyed within 5 seconds with threads flying around. It scored 1 out of 5 on this durability test. At the same time, on the right, we see how indestructible the Altra Rivera 3’s heel padding is, which is why it scored the perfect 5/5. 

We’ve written more about the durability of the outsole (and grip and many other things) in our guide In-depth insights into running shoe outsoles (road and trail). 

Why we torch the leather uppers

Torching the leather and scratching the burnt area allows us to check whether the leather is genuine or not. 

When it bursts into flames and melts, usually discovering different layers, we know it’s a fake one.  When it chars and merely gets scorched, and scratching it with our awl reveals only low-level damage, we notice it’s a dense, full-grain leather. It also smells like burnt hair.

Why we turn the lights off in the lab

Nothing to do with romance. We do it to find out whether the shoes are noticeable in the dark or not. Look how shiny HOKA Trail Code GTX is in the dark!

How we decide which shoes to buy

When buying shoes, we consider the importance of the shoe and its availability. The importance is reflected in the shoe’s value and popularity. While popularity is obvious, the value is what also pushes the shoe to the top of the pipeline - it can be a shoe that’s a part of a collection or an important niche shoe (like mud or track spike).

We buy the shoes in men’s US 9. If not available in that size, we wait until it is. You can always check out our Pipeline to see the list of shoes we purchased or just started testing. 

Shoe pipeline: which shoe is next?

Once the shoes arrive, we decide on the next batch. Within 1 week, we always test shoes that belong to 1 category only. We don’t do the same tests for, e.g., running and gym shoes. There are variations in the type and number of tests we do for each category, so we don’t mix them up. This also means that sometimes, less popular shoes are tested together with highly popular shoes because they belong to the same category. For a clear overview of shoes we just bought, took to the lab and started testing, or finished reviewing, see our Shoe Pipeline page.

We also take the weather into account: when it’s really bad, we might do a batch of shoes that can be tested indoors, like gym shoes. 

Shoes we do not test 

We only test shoes that belong to these categories: running (both road and trail), track spikes, cross country, basketball, training, tennis, walking, hiking (shoes, boots, sandals), and sneakers. We don’t test shoes that belong to other categories. 

We also do not test shoes that are released as a variation or a collaboration. We usually focus on the OG model. If there’s a new release that comes with an updated, more sustainable upper, recycled materials, or a collaboration, we stick to the OG shoe.

Wear-testing the shoes 

We always test shoes in proper surroundings to truly understand how they feel and perform. 

Category	Wear test location
Road running	Mostly roads, we might give light trails a try as well.
Trail running	Trails, different surfaces. If lugs are smaller, we include roads as well.
Hiking	Trails, different surfaces.
Walking	Different surfaces, depending on the shoe.
Basketball	Basketball courts (indoor/outdoor).
Track spikes	Track
Cross country shoes	Different surfaces, depending on the spikes.
Training	Gym
Tennis	Tennis court, different surfaces
Sneakers	All-around, mostly casual walks around the town.

These tests help us understand shoes better so that we can deliver more in-depth and objective reviews. 

Just knowing that, in the lab, the heel counter scored 4 out of 5 for stiffness does not always tell us everything. It can mean that the counter is harsh on the runner’s heel or that it is exceptionally stable. Or that it allows for heel slipping. Because we’re aware of all the nuances, we never skip the wear test.

Methodology updates

Methodology 2.5 - Breathability and drying potential

Updated June 2026.

Breathability

Most people think of breathability as air permeability, when in fact it is about water permeability. In the context of physical activity and shoes, breathability is the shoes’ ability to allow moisture vapor from sweat to be transmitted through them. 

Breathability is not just about having big holes in the upper, although such shoes generally perform well in our breathability test. It’s also about the material's ability to transmit sweat. And keep in mind that breathability is not just about the upper, as sweat can also get stuck in the insole or even the midsole. 

Breathable shoes are more comfortable because there’s no sweat accumulation that would lead to blisters, discomfort, sliding, and most importantly, the body not cooling down properly. The comfort zone for feet sits between 28 and 34°C inside the shoe (according to this study), and shoes can increase the temperature by 4°C during walking, before you've broken a sweat in any meaningful sense (study). After 30 minutes of running, the temperature increases by 8.2°C at the heel and 4.8°C at the big toe (source). And as shown in this study, hiking in wet socks doubles the blister risk. 

With the new machine, we’re testing breathability following the SATRA TM376 methodology. We measure breathability in BR, and we focus specifically on how good the shoe is at moving sweat away from the skin; the drier the skin, the better the breathability. Technically speaking, the setup uses a footform held at body temperature inside an environmental chamber. We put a layer that simulates skin on it, then a performance sock, and finally the shoe. The test is performed for 3 hours, during which water is slowly released through the skin layer to simulate sweating during physical activity. 

Drying potential

Drying potential, measured in %, tells us how much moisture has evaporated from the shoe overall during our 3-hour test. Drying potential is important for long efforts, such as marathons and ultras, long and multi-day hikes, and similar activities where sweat or water (puddles, rain, snow) can accumulate in the shoes. High drying potential suggests the footwear will dry sooner rather than later, so you don’t have to deal with soaked socks and shoes.

Per this study, 76% of participants developed blisters over a 4-day race (182 km). It’s important to take into account both breathability and drying potential, because even when breathability is high, sweat will leave the skin and maybe even the socks, but it can recondense on the inner lining (as shown in this study). This subsequently impacts insulation, too.

Ideally, you want both numbers to be high. 

Methodology 2.4 - Insulation

Updated April 2026.

We’re now testing thermal insulation and cold rating following the SATRA TM436 methodology, but with our own adjustments that better mimic the behavior of modern-day footwear.

This test runs for hours per shoe, measuring the energy required to maintain an artificial foot at a constant temperature under controlled conditions. This objectiveness allows you to compare how warm different shoes are in cold conditions.

The measurement unit for R is m² K/W. Technically explained, it quantifies the temperature difference (K) when one unit of heat energy (W) flows through a surface (m²).

While this is the gold standard in footwear testing and the machine used is worth $100,000, it’s not perfect. This study and this study found that sweat, exercise type, wind, and compression may all contribute to the degradation of the shoe’s insulation. In our testing, these factors are not considered.

We’ll also soon launch Methodology 2.5, covering breathability, which is NOT the opposite of insulation. Ideally, the level of insulation should be adequate for the activity you're doing, and breathability should be high, so your skin can get rid of the sweat. The insulation test is about heat, not sweat.

Methodology 2.3 - Torsional rigidity

Updated March 2026.

We custom made a machine to improve our torsional rigidity testing. We lock the heel and forefoot vertically and horizontally with a pre-defined force. We then apply torsion to 10° towards the medial side and towards the lateral side of the shoe.

We perform five conditioning repetitions in each direction, which lowers the within-shoe standard deviation from 0.34 to 0.12 with an average CV going down from 4.0% to 1.6%.

We report the 6th reading for both directions and sum it to a single torsional rigidity metric.

Methodology 2.2 - Midsole softness is now Asker C

Updated February 2026.

All tests related to midsole softness are now measured with an Asker C durometer (AC) instead of the Shore A durometer (HA) to improve sensitivity in softer foam compounds:

• Midsole softness
• Secondary foam softness
• Midsole softness in cold (%)

We have back-tested about 200 running shoes and 300 athletic shoes in total, allowing comparisons from the start. 

While there is a meaningful correlation between the new Asker C measurements (AC) and the previous Shore A measurements (HA), we advise against comparing the two methods because the variation in individual results can be substantial. On average, Asker C measurements (AC) are ~2x bigger (1.96x to be exact).

 

 

Methodology 2.1 - upgraded air conditioning and humidity

Updated January 2026.

We have implemented a new air conditioning system that maintains constant conditions, measures temperature and humidity, and notifies us of potential variations. In both our testing facility and storage, we now operate at a constant 20°C/68°F ± 1°C and 55% ± 5%.

We have already seen significant variations in midsole softness and stiffness, and internal testing has also confirmed significant changes to shock absorption, energy return and traction with changes in temperature. This is another layer that builds toward reliable and repeatable results.

Methodology 2.0 - Energy return, shock absorption, traction, new flex test, new rocker media

Energy return and shock absorption

When testing energy return and shock absorption, we decided to follow ASTM F1976-13, which is the gold standard. 

This is our testing process: 

1. Remove the upper so that the machine can reach the heel and the forefoot freely.
2. Fix the shoe in place. 
3. Drop an 8.5 kg mass from a height of 50 mm, resulting in a total energy input of 5 J.
4. Perform the test at the heel, at exactly 12% of the inner shoe length, and/or at the heel, at 75% of the inner shoe length.
5. Perform 30 repetitions per location, out of which repetitions 1-25 mimic a natural break-in, while repetitions 26-30 are used to calculate the average energy return and shock absorption values. There is a 2-second pause after each drop. 
6. Export and publish the results. 

Marking the 12% and 75% of the inner shoe length spots, exactly where we test energy return and shock absorption

Traction test: Dynamic coefficient of friction

We bought a machine that allows us to test the dynamic coefficient of friction (CoF) following the SATRA TM144 methodology. Depending on the activity, we test the traction at the forefoot or at the heel. To replicate the real-life activity, we press the shoe with a force of 500N against the surface at a 7-degree angle.

The surface for road running, trail running, hiking, walking, sneakers, and training is wet concrete. It’s dry when we test the traction of tennis shoes. This concrete surface is continually replaced with a new one to avoid inaccurate results due to wear and tear. 

When measuring the CoF for basketball shoes, we smash them against the actual basketball surface. The surface we use is Junckers' Pro Complete 44 sports floor system, which is used for FIBA EuroBasket, FIBA World Cup, and Olympic Basketball Tournaments, among many other events.

The result of this test is a dynamic coefficient of friction. The higher it is, the better the traction.

New machine test: Stiffness

We bought a machine to test the stiffness of the shoes. This is a significant improvement when compared to how we used to perform the stiffness test, using a force gauge and bending the shoes to 90 degrees. 

This is a standardized test in which: 

1. The shoe is fixed to the ground at the forefoot. 
2. This results in the heel being lifted from the surface due to the toe rocker. The more aggressive the toe rocker, the higher the starting angle will be. 
3. The plate is then lifted until it touches the heel, which is the starting point for the test.
4. We then run the stiffness test by bending the shoe 30 degrees and measuring the force needed to do so in Newtons. 

Stiffness test in cold is discontinued 

When assessing the shoe’s performance in cold weather, which we replicate by putting the shoes in the freezer for 20 minutes, we decided to focus on the softness of the midsole. We test the stiffness of the shoe at room temperature only. 

Improved rocker assessment 

Previously, we focused on the toe rocker, and we took photos of the forefoot against a horizontal and a vertical ruler. Given the importance of the rocker technology as a whole, we now look at both the forefoot and the heel. 

Methodology 1.8 - Gel test, durability updates, rocker test, improved breathability test, microscope.  

Updated January 2025.

Measuring shoe dimensions with the help of gel molds.

After several months of development, we achieved a more accurate approach to measuring shoe dimensions. We now pour a proprietary liquid into each shoe and put it in the fridge for 2 hours to retrieve a gel mold of the interiors.

Instead of applying our caliper to the outside of the upper, we now get to measure its inner width and height. These measurements are more accurate because they no longer include the thickness of upper materials and overlays and take into account the stretchiness of the shoe’s upper material.

Here are the three caliper measurements we take using the gel mold:

• The shoe width

A custom-made shoe holder allows us to locate the widest points of the mold. This corresponds to the area between the first and fifth metatarsophalangeal joints.

• The toebox width

For consistency, this measurement is always taken at the same distance from the tip of the mold. The line on our shoe holder is drawn precisely at 28.3 mm from the tip of the shoe. This measurement shows how wide the shoe’s toebox is in the area where the big toe normally ends. It also indicates how mild or aggressive the taper angle is (how rounded or pointy the toebox gets towards the toes).

• The toebox height

This represents the vertical space available in the shoe’s toebox. It is measured at the same distance as the big toe - 28.3 mm from the tip of the shoe.

Updated Dremel test conditions

Because our new and improved version of the Dremel is more abrasive, we had to apply less force in our durability tests.

• The pressure went from 3.2N to 2N in all of our durability tests.
• The drilling time was shortened from 22 seconds to 18 seconds for the outsole durability test.
• For the toebox and the heel padding test, we reduced the RPM from 10K to 5K. 

The changes are minor because we still want our new and old results to be comparable.

Additional durability test for tennis shoes

Each tennis shoe in our lab now undergoes an additional Dremel test where we check the durability of its toe drag guard.

Because it is often made of tough rubber and sustains abrasion similar to the shoe’s outsole, we test the toe guard in the same conditions as the outsole. The Dremel speed is set to 10K RPM, the pressure is at 2N, and the exposure lasts 18 seconds.

We apply the sandpaper tip of the Dremel to the same spot on the inner side of the shoe’s forefoot. This is the area where most abrasion occurs during the on-court toe drags.

Based on the severity of the damage, we rate the shoe’s toe drag guard durability on a 1-5 scale, where 5 stands for most durable.

Microscope shots of premium foams

We take special interest in the newest and most innovative types of running shoe foams.

That's why we now cuut out sample of these foams and use a microscope to study them at cellular level. This allows us to understand how the foam’s cell structure is connected to its energy return and other cushioning properties.

Toe rocker demonstration

Running shoes with pronounced toe rockers are put against our XY-axis ruler. While we do not take any numerical measurements of the rocker angle yet, these photos act as a visual demonstration of each shoe’s curvature and how it compares to similarly designed shoes.

Improved breathability test (This test has since been replaced with our new breathability method and is only present on shoes tested a long time ago).

We made our smoke-pumping machine test more accurate with the help of a 3D printed shoe last with an open toebox.

It creates a controlled outlet for the smoke by isolating the toebox from the rest of the upper. The problem with filling the shoe’s entire upper with smoke was that it escaped through the gaps on the sides of the the tongue. This gave us inconsistent results due to varied tongue designs and the fact that it tends to slide around, leaking smoke in the instep area.

Methodology 1.7 - durability test, leather and suede quality test

Updated June 2023.

Our lab reviews are now presented in a standardized, clear-cut layout where each section is dedicated to a particular aspect of a shoe such as breathability, durability, cushioning, etc.

Each section includes multiple lab and field tests that give an in-depth look into what the shoe feels like and how it performs. We interpret every lab test result to make it clear to a beginner athlete or someone who is not geeky about shoes.

We measure and assess over 20 parameters for each shoe in our lab. These measurements are then compared to the average in a given shoe category.

In the example below, we measure the heel stack height of a road running shoe and present it in a table and a graph in comparison to the average heel stack of road running shoes.

New durability tests with a Dremel

Following the success of our toebox durability test, we now apply the Dremel to the shoe’s heel padding and outsole.

We chose heel padding because it is another area on the upper that is most prone to abrasion due to constant chafing against the ankle. We make sure that the Dremel always touches the padding with consistent force (3.2N) and speed (10K RPM). Due to the material’s fragility, we only hold the tool for 4 seconds. The damage is then assessed on a scale from 1 to 5.

When it comes to the rubber outsole, we hold the Dremel for 22 seconds with the same force (3.2N) and speed (10K RPM).

We then measure the depth of the dent with the help of a tire tread depth gauge.

New test to check leather and suede quality

Whenever a brand claims to use real leather or suede in its shoe, we equip ourselves with a butane torch to test that statement. We hold the fire against the corresponding parts of the upper for a few seconds.

What we look for in genuine material is for it to char and emit a smell akin to burnt hair. That is an indication of real leather and suede whereas melting or catching fire is a sign of fake (synthetic) material.

Methodology 1.6, dremel durability test, microscope, shoe rocker test, weight adjustment, improved toebox test

Updated April 2023.

Durability tests with a Dremel

To check the upper’s resistance to abrasion, we now perform a Dremel test on one of the most sensitive parts of the upper - the toebox fabric and the heel collar lining.

The shoe remains in a fixed position as we apply the Dremel to it. The following conditions are applied to all shoes for consistency:

• 3.2N of force
• 4 seconds
• 10 000 RPM 

To prevent the shoe’s color from creating bias, we put a piece of contrasting white plastic underneath the textile.

Close-up photos with a microscope

Having added a microscope to our lab, we are now able to take a much closer look at each shoe’s upper fabric and other parts.

Close-up shots of the upper, for example, help us support statements about the shoe’s breathability, waterproofing capacity, and durability.

Sample of a waterproof textile

Sample of a breathable mesh

Shoe rocker visualization

We added a visual demonstration of how much of a rocker is present in each shoe’s design. Initiating movement in the heel, we aim to replicate the heel-to-toe transition of the foot for heel strikers.

All shoe weights are presented in men’s US size 9

To make our data consistent, we measure every shoe’s weight in a men’s US 9. That’s because it is the most common shoe size and brands often provide shoe weight in this particular size.

However, in the rare cases where we cannot get US 9, we buy US 8 or 8½ and use a proprietary formula to calculate for US 9.

Nike ZoomX Invincible Run Flyknit 3 was measured at 9.4 oz (267g) in a US 8. It corresponds to 10 oz (284g) in a US 9.

The formula we use is based on the weight measurement of 4 different shoes from different brands measured in 10 different sizes.

The measurements were kindly provided to us by Running Warehouse.

Improved toebox measurements (UPDATE: this test is no longer present and was updated with methodology 1.8)

Previously, we only measured the toebox in its widest part (around the metatarsal joints).

But now we also measure the width near the toes (at the top of the shoe).

This allows us to check how much narrower the toebox gets toward the toes. It is possible that two shoes will have the same width in the metatarsal area but one of them would get much tighter around the toes.

Methodology 1.5, 1.4, 1.3, 1.2, 1.1 

Last updated in August 2022. All of these methodologies have since been replaced by newer, improved testing methods. As none of the shoes currently featured on our site were tested using these outdated methodologies, we have removed the related content.