Review-adidas Ultra Boost: An Experiment on the Soft and "Natural" Side. A Shoe for LSD: Long Slow Distance. Comparison to Energy Boost.

The adidas Ultra Boost is a 11.4 oz (323gram) , 27mm heel 17mm forefoot 10mm drop shoe (according to Running Warehouse's description). Available now.  $180!  I am calling it a 2nd generation Boost "training" shoe for slower miles and for those seeking great cushioning, a very comfortable stretchy upper and a sort of "natural" ride on the road.  It is packed with innovative features, some that work for me, others not so much, particularly the overall softness of the ride. The Ultra Boost was a personal purchase. It fit true to size.
I first read about Ultra Boost through my friend Frederic Brossard, a mighty fine blogger over at  runners.fr. I attempted to translate his impressions from the original French here.

The Ultra Boost features:

• adidas Boost material, 30% more of it in the midsole and no firmer EVA layer at the toe and as stabilizing ring around the outer perimeter just above the insole as in other Boost runners such as the Adios Boost and Energy Boost,  
• an innovative incredible comfortable single piece and stretchy PrimeKnit upper, some will be able to run without laces,
• instead of a full heel cup, two plastic heel wings leaving the achilles supported but not pressured, 
• a new outsole, the Stretch Web a soft conforming layer on the road,
• The Boost stabilizing Torsion plastic is embedded in the midsole instead of placed just under the outsole under the midfoot and there is none in front to support the forefoot as in other Boost shoes such as Adios Boost, Boston Boost, and Energy Boost.

This adidas promotional video illustrates the construction of the Ultra Boost and calls it "The Greatest Running Shoe Ever". I am not so sure it is the Greatest for me but in terms of innovations it is packed with them, more a platform to show off several new technologies.

All of "it", the technology innovations, add up to one relatively heavy shoe at 11 oz plus (1.4 oz heavier than the Energy Boost). Ultra Boost is soft under foot on the run particularly the forefoot:

• considerably more flexible than the Energy Boost without the distinctive snap flex.  
• less responsive than Energy Boost, my go to marathon race shoe (review here)  or Adios Boost my 2014 Shoe of the Year (review here), or the well cushioned and smooth New Balance Fresh Foam Boracay (review here).

The details and what I thought about running in the Ultra Boost click on Read More



I found that due to the soft forefoot it was mostly suitable for slower, long runs. An interesting feeling ride, one can really feel the forefoot and toes sinking and splaying into the Boost and when combined with the soft and conforming Stretch Web outsole almost a sensation of running on nice soft ground and grass... on the road. Thus, sort of a "natural" very comfortable ride, but not a particularly fast or efficient one as where the rubber hits the road at push off there is not much firmer rebound(ironic with Boost) or snap. Some may find the Ultra useful for... Ultras on smoother terrain or roads.

Boost
Boost is unlike any other midsole material used for running shoes as instead of the ubiquitous EVA it made up of heat expanded TPU beads which provide a distinct and soft cushion, and then a noticeable rebound sensation. I love my Adios Boost and Energy Boost shoes, my go to shoes for  racing and much of my training. Boost is also claimed to be far less sensitive to outside temperatures, more consistent and my outdoor runs in temperatures well below freezing and on an indoor treadmill confirm that the cushion feels about the same regardless of temperature. Very different than EVA based midsoles which harden noticeably in cold.

Upper and Fit

The PrimeKnit upper is dense and very stretchy. I have not tried Nike's FlyKnit shoes but did stick my hand in one this week and PrimeKnit appears far stretchier. The upper is entirely one piece including the tongue so essentially you slip your foot into a bootie. True to size for me. Incredibly comfortable.

 

I lightly laced. Far more lightly than usual as the 3 support bands are thick, maybe a bit to thick, and there is no need to cinch down laces as in most shoes. 

The PrimeKnit adapted to my bunion on the right. I do fine with most uppers with this bunion unless the last lace hole and related overlays are far down the shoe and the shoe is narrow in this area. Note how far back the laces start on the Ultra Boost given the PrimeKnit doing most of the work of supporting the mid foot.  Those with bunion issues might consider the Ultra Boost. The front is a bit pointy but given the soft Boost and no Torsion or EVA upfront I believe any wider might make the shoes even softer and less stable and responsive. 

The heel counter is split with 2 plastic wings. The only seam in the upper is centered at the back. Heel counter is supportive and comfortable. Those with achilles tendon pressure issues might try on the Ultra Boost to see if it works to relieve pressure there.

Midsole and Outsole

The midsole is all Boost, 30% more Boost. What is eliminated is the firmer EVA  (orange) of the Energy Boost, a stabilizing ring that surrounds the insole around the outer perimeter as well as the solid piece of EVA upfront at the toe. This firmer layer provided a bit more stability and response in the Energy Boost and also when combined with the Torsion strips make the Energy stiffer snappier in the forefoot.  I find the Energy Boost a touch too stiff, the Ultra Boost quite mushy and soft upfront. The happy medium between the two would be ideal. Thankfully the Ultra Boost keeps the stabilizing gray TPU piece on the medial side to tame the foot a bit and move it forward on landing. The Boston Boost (review here) eliminated this piece to my regret, to soft a heel for me. For those familiar with Hoka One One Clifton (review here) I find the heel a touch firmer and certainly better supported in the Ultra Boost and the forefoot yet softer than Clifton and less responsive.

The Torsion system (the gray TPU strips below) is completely different and less of it. In the Ultra Boost the Torion is far more minimal and embedded in the midsole. There are no Torsion strips in the mid and forefoot as the Energy Boost had with the strips extending all the way forward on the medial and lateral sides. Under the midfoot one can clearly see the Torsion centered in the Ultra Boost and not spanning the mid foot. Despite this, the midfoot felt fine in the UltraBoost but I had a sense of a slower motion transition to toe off.

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The outsole of the Ultra Boost is the new Stretch Web. It has raised nubs which are already wearing faster than the Energy Boost Adiwear rubber which wears like iron.  Traction on snow is not great but snow and I except any mud clears easily. Traction is fine on wet and dry roads.  I would have kept the more continuous contact and segmented rubber heel and forefoot outsole of the Energy Boost. Not sure Stretch Web does it for me...as it contributes to the overall softness and lack of snap of the shoe.

Testing Notes
Given the very cold conditions in New England this winter I tested the Ultra Boost and all shoes I have reviewed this winter as follows: runs outside and on a treadmill. I also ran at least a mile with a comparative shoe, here the Energy Boost, on one foot with the review shoe on the other.  In the case of the Ultra Boost, unlike all EVA based midsoles,  I could feel no difference in ride between temperatures in the teens Fahrenheit and when indoors in the 60's

Ride and Recommendations

The adidas Ultra Boost is a shoe for what we used to call "LSD:  long, slow distance. Soft in the forefoot with a very comfortable stretchy PrimeKnit upper it is on the heavy side of current road trainers at over 11oz. The softness and flexibility of the forefoot gives it a sort of "natural" ride, somewhat like running on soft ground as the stretch upper, Boost midsole and StretchWeb outsole without Torsion plastic upfront conform and move with the foot as it sinks into the Boost and toes splay.
The Ultra Boost, given its very stretchy PrimeKnit upper, may fit those with bunion issues and a relatively narrow foot. The upper, when stretched by the foot should adapt to different width feet and swelling, with the very front of the shoe  a bit pointy. The PrimeKnit bootie allows a variety of adjustments for different types of feet with the laces largely relegated to holding the plastic 3 bands in place. The overall cushioning is outstanding, if soft.
The heel and mid foot ride is soft but well supported by the upper as well as the plastic 3 bands and some Torsion system embedded in the midsole. While I find them very comfortable they will not be a daily trainer for me, not enough pop. A recovery, slow easy days, and LSD shoe for when pace is not on the agenda for the day's run. Some may find the Ultra a good shoe for...ultras on smoother terrain. An overall pleasant comfortable feeling but not a fast responsive one, not nearly the pop of the adidas Energy Boost. While highly innovative it is not "The Greatest Running Shoe Ever." but more a platform which will hopefully evolve over time.

If you would like to try the adidas Ultra Boost they are available from Running Warehouse: Men's here, Women's here. 

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