Adidas Ultraboost Light review

We recommend the Ultraboost Light to:

• Casual runners who want a stable neutral road shoe
• Heel strikers looking for added rearfoot protection
• Runner who enjoy long distance efforts 
• Those looking for a daily runner that doubles as a comfy sneaker
• Runners with mildly pronating strides

While heel-strikers have plenty of plush foam to land on, the midsole provides much less cushioning at the forefoot, so mid/forefoot striking runners will find the shoe to feel much more firm underfoot. We recommend the ASICS Gel Nimbus 25 as an alternative that's well cushioned throughout.  

Contrary to what the name suggests, the Ultraboost Light is relatively heavy. While this isn’t an issue for short to mid-distance runs, the shoe did prove quite burdensome  during the latter half of our longer test runs. 

The sock-like fit of the Ultraboost Light lends the shoe a comfy lockdown that’s secure enough for most purposes. It’s only when we picked up the pace that we began to notice some foot movement within the shoe that brought on some uncomfortable hot spots. For a daily trainer that sports a more snug, racer-like fit, we recommend the Brooks Levitate 6.

We measured the prominent heel stack of the Ultraboost Light to be 30.1 mm which is almost exactly as advertised by Adidas. While this makes the shoe’s stack ever-so slightly shorter than our lab average, heel strikers will have more than enough cushioning underfoot for a protective and comfortable ride. 

With a forefoot stack measuring 21.7 mm according to our calliper, the Ultraboost Light is only 1.7 mm taller than officially stated by Adidas, and also falls just shy of our current lab average. While this stack height gives forefoot strikers a good amount of ground-feel, it does come at the expense of impact protection, which feels inadequate for longer runs. 

As the video below demonstrates, forefoot strikers won’t savour the cushioning of the shoe’s midsole as much as their heel striking counterparts. For a shoe that boasts more foam at the forefoot, we suggest checking out the ASICS Gel Nimbus 25 instead.

The difference in our two stack measurements leave us with a drop height of 11.9 mm, which classifies the Ultraboost Light as a high-drop shoe. This steep drop definitely favours runners with a heel striking stride as it promotes good heel-to-toe transitions. 

It must be said that high drop shoes put more strain on our knees and hips which can increase the likelihood of injury, especially for forefoot strikers. Check out this helpful guide for more information that will help in choosing the right drop height.

The midsole of the Ultraboost light is decidedly plush. With a reading of 15.5 HA according to our durometer, the shoe’s midsole is much softer than our current lab average. 

While this may be the case, the midsole has a lot of bounce to it and doesn’t bottom out when weight is applied to it, rather quickly springing back to shape. This means that the Ultraboost Light boasts a ride that is not only cushy and comfortable, but energy-efficient enough to support our long distance runs as well. 

On the other hand, while it is possible to pick up the pace in this shoe; the sheer lack of foam at the forefoot meant that our toe-offs weren’t poppy enough to support tempo runs. For a daily shoe that’s more capable of high pace running, we recommend the Adidas Adizero SL which provides performance on a budget .

We popped the Ultraboost Light in our freezer for twenty minutes to simulate exposure to cold weather and re-tested the shoe’s midsole with our durometer. With a reading of 19.8 HA, the Ultraboost light remains remarkably soft in the cold compared to the average shoe. 

This, in conjunction with the shoe’s toasty upper, makes the Ultraboost Light a great choice for winter running of those living in colder climates as it remains cushy and plush no matter the weather. 

While these results make the Ultraboost Light about as consistent as the average shoe under the same conditions, stiffening up by 27.4% in the cold; we must bear in mind that the shoe’s post-freezer midsole is still softer than the average midsole at room temperature!

We measured the insole of the Ultraboost Light at a meager 2.8 mm which is a fair bit thinner than our current lab average. 

We measured the toebox at its widest point to be 102.9 mm. This makes the shoe quite a bit roomier than average and means that runners with wide feet will have no issues with fit in the Ultraboost Light. 

Moving down to the big toe area, we measured the toebox to be 81.6 mm. This is also wider than the average for shoes we’ve tested in the lab, which means that our toes have more than enough room to splay naturally without being constricted by the shoe. 

The knit upper is nice and stretchy, which combined with the wide base, meant that the upper comfortably wrapped itself around our foot with enough elasticity to lock the foot down with minimal movement. 

Runners with very narrow feet, however, might find the Ultraboost Light to be a little too roomy. We therefore recommend that those runners look into sizing down as the shoe does run a little long as well.

The heel cup on the Ultraboost Light is well padded and shaped in a way that snugly squeezes the heel while avoiding putting too much pressure on the Achilles.

The Ultraboost Light feels incredibly stable underfoot. Shifting our weight from side to side, our feet felt well planted into the ground despite the shoe’s high heel stack. 

The Ultraboost Light put up a fair amount of resistance as we torqued and twisted it in our hands, giving the shoe a score of 3 out of 5 for torsional rigidity. This helps to offset any instability brought on by the high heel stack while still being flexible enough to adapt to the shape of our foot rather than forcing it in place. 

The heel counter felt moderately stiff as we squeezed and manipulated it, giving it a score of 3 out of 5 on our subjective scale. This level of stiffness means that the shoe does a good job holding our heel in place and helps to prevent too much rolling from side to side. 

We measured the midsole with our caliper to be 117 mm wide at the forefoot. This is significantly wider than our current lab average, and gives us an extremely steady, if somewhat firm, platform to land on for forefoot strikers. 

The midsole is also wider than average at the heel, measuring 93.7 mm according to our calliper. This gives heel striking runners more than enough surface to ensure stable landings 

The overall wide midsole of the Ultraboost light gives us an added sense of stability that is often lacking in high stacked shoes. This means that the shoe will also benefit runners with a slightly pronating stride.

We test the flexibility of a shoe by securing it to our workbench and measuring how much force is required to torque the shoe to 90-degrees. With a reading of only 18.6N the Ultraboost Light is much less stiff than our current lab average. This definitely contributes to the ease and comfort we felt when testing the Ultraboost Light; with the shoe moving with the natural motion of our foot instead of fighting it.

We repeated the stiffness test after leaving the Ultraboost Light in the freezer for twenty minutes and got a reading of 24.4N. This makes the Ultraboost much more flexible than our lab average under the same conditions, and means that the shoe will remain extremely pliable even during the frostiest winter runs. 

These results mean that the Ultraboost Light only stiffens up by 31.3%, making it much more consistent than the average shoe between warm and cold conditions. To further contextualise just how remarkably flexible the Ultraboost Light is in the cold, it rivals the reading of a great bulk of shoes we’ve tested at room temperature! 

While this may be its lightest iteration so far, tipping the scale at 10.75 Oz (305g), the Ultraboost Light simply isn’t as light as the name implies. The shoe is about as chunky as it looks and quite a bit heavier than our current lab average. 

To test how breathable the Ultraboost Light is we pump the shoe full of smoke and observe how it dissipates through its upper material. As you can see the smoke does manage to escape the shoe, though mostly through the sides and toebox while the tongue seems to trap it in. This leads us to give the shoe a breathability score of 3 out of 5. 

Compare that to how the Saucony Triumph fared in the same test. With a perfect score, it virtually disappears in a fog of smoke that emerges almost as soon as it is pumped in. 

Inspecting a backlit section of the upper gives us a better impression of how insulated the shoe is, with almost no light shining through any section of the shoe. 

Our closeup shots of the Ultraboost Light also explain the shoe’s lacklustre breathability. We can clearly see that the material that makes up the upper knit layer is thick and tightly braided, while the mesh that lies below is dense and not porous enough to allow heat to escape efficiently.

We tested the durability of the Ultraboost Light’s toebox by applying our dremel to it with a force of 3.2N at 10K RPM for four seconds. While we were able to tear clean through the shoe’s knit upper, the mesh below remained relatively intact, which leads us to give the toebox a durability score of 4 out of 5. 

The Ultraboost Light’s heel counter proved to be an even more worthy contender against our dremel. After four seconds at the same parameters as the previous test, the dremel barely left an imprint on the shoe’s heel collar, leaving it looking about as it did before the test! We therefore score the shoe’s heel padding a perfect 5 out of 5. We can safely predict that the Ultraboost Light will still have most of its padding intact well beyond 500 miles of use. 

We pressed our durometer against the outsole of the Ultraboost light to test how hard it is and got a reading of 76.8 HC. 

This is slightly softer than our current lab average, but still in that sweet spot between hard and durable versus soft and grippy.

To simulate extreme wear and tear over time, we once again fire up the dremel to 10K RPM and apply it to the shoe’s outsole with a force of 3.2N but for twenty seconds this time. The result of the visually anticlimactic test was a loss of only 0.71 mm of rubber. This makes the Ultraboost Light much more durable than average, and further supports our prediction regarding the longevity of this shoe. 

The shoe’s outsole is only 2.4 mm according to our calliper measurements, but, as the previous test demonstrates, the durability of the rubber means that this isn’t an issue as there was more than enough rubber left to run our dremel against it three more times. 

By skimping on rubber in this instance, Adidas is able to keep some much needed weight off this already hefty shoe. 

The outsole provided us with sufficient traction across most surfaces we came across with the exception of a patch of cobblestone, soaked by a nearby sprinkler, that proved to be a challenge for the shoe’s grippiness. 

With no reflective element whatsoever, the Ultraboost Light completely disappears in the dark. We therefore advise keeping to well-lit areas or taking the appropriate precautions when running at night. 

The padding in the tongue area of the shoe’s upper is only 1.3 mm thick based on our calliper measurements. While this is quite meagre compared to our lab average, the plastic overlays adorned with the Adidas logo that hold the laces keep them from cinching down too tightly around the instep; so lace bite was never an issue during our test runs. 

The Ultraboost Light is sock-like, which means that the tongue is an integral part of the upper with no separation from it. While this contributes to the shoe’s comfort, it’s not tight enough to provide adequate midfoot lockdown for tempo training. 

The Ultraboost Light doesn’t have any traditional heel loop to speak of; but the heel counter does extend slightly to form an elf ear tab that helps pull the shoe on, as well as providing some added support around in the rearfoot area. 

The insole of the Ultraboost Light is removable, making the shoe suitable for custom orthotics if needed.