This tempo trainer has a firm, responsive EVA midsole and a snug, race-ready fit.
The RW Takeaway: The midsole feels firm and less bouncy than a Boost shoe, but the SL20 is still light enough for long tempo runs and short races.
- Built on the Adizero last, it has a snug, secure fit.
- An EVA midsole provides firm, protective cushioning.
- Continental rubber under the forefoot keeps you planted at speed.
Price: $160
Weight: 229g (M); 187g (W)
Drop: 12mm
Type: Road
What do you get if you take an Adidas Boston, swap out the Boost foam, and knock $20 off the price tag? The SL20. Longtime wearers of the Boston line will feel at home from the second they slip their foot in and experience the traditional fit from Adidas’s fastest shoes. Anybody accustomed to a cushier, beefier daily trainer will like the lightweight pop the SL20 delivers for uptempo sessions. And all will appreciate the dependable Continental rubber covering the entire forefoot, which held firm even on rain-slicked sidewalks.
- Built for speed
- Lightweight
CONS:
- Lightstrike isn’t as responsive as Boost
- Heel can rub and cause blisters
Where Has All the Boost Gone?
There was a time that almost all of Adidas’s performance running shoes had Boost midsole material. But that premium ingredient is slowly disappearing. Boost was introduced in 2012 as a bouncy, high energy return alternative to the same old EVA foam that had been used for decades. It was great, because it offered a ton of cushioning and a trampoline-like effect on rebound. The downside is that it’s a heavy material, and in today’s foam wars, there are lighter options that deliver similar properties. So we see less Boost now. For shoes like the SL20, that means a return to EVA.
Adidas calls the SL20’s midsole “Lightstrike,” but simply put, it’s compression-moulded EVA. The benefit is that you get dependable lightweight cushioning and excellent durability, though it doesn’t have the same snap on toe-off that you get with a thin layer of Boost, like in the Boston or Adios.
“Overall the shoe was comfortable enough,” says one female tester who regularly logs 7:00 miles and is a past winner of the Runner’s World Half-Marathon. “I used it more for shorter-length runs because I was craving a little more cushion by the end of 5 miles or so.”
An Upper Built For Speed
The Adizero line is essentially Adidas’s stable of race-ready shoes. And, as you’d expect from go-fast kicks, the fit has to be dialed so there’s no wasted energy from your foot moving around inside the shoe. That’s the case here with the SL20, too, which shares the last that other Adizero shoes are built around. We found it has an excellent fit—snug through the midfoot and over the instep, without being uncomfortable. The forefoot opens to be wide but not overly roomy. Beneath that, the sole flares out a little to each side, giving you a stable platform for toe-off when you’re running at quicker speeds.
Testers found its racy construction a little uncomfortable for longer efforts. The shoe is lightly padded and has a relatively rigid heel counter in the back. The top edges of that counter fall just below the collar padding, so any movement in the back half of the foot can put you up against that hard plastic and cause some irritation. “The collar was too hard and stiff, and continually gave me blisters,” reported one tester. “It bothered me despite Band-Aids and trying different socks.”
If, however, you’re better accustomed to lightly built shoes and don’t experience a lot of heel movement, you’ll like the breathable mesh covering the forefoot and the thin, airy tongue. A couple of testers reported that the tongue was too tall, but that’s likely just because the pull tab is overly stiff and sticks up. My recommendation: Cut it off.
What One Tester Said
Eileen C. | Tester since 2019
Arch: Medium | Gait: Neutral | Footstrike: Midfoot
“It’s very lightweight, which is something that I enjoy in a shoe. I would say that it feels like a cross between a Brooks Launch and a Saucony Kinvara. It would be a good option on long tempo days if it had a little more cushioning underfoot—it does not have the responsiveness I want. The lacing doesn’t feel overly secure. I even did heel lacing but didn’t feel secure after a few km’s.”
