A new addition to the Altra family of zero-drop neutral trainers, the Altra Duo defies the rule maximum cushioning and ultra lightweight performance can’t go hand-in-hand. At 7.0 ounces for men and 5.3 ounces for women the Duo packs an astonishing 31mm full-length stack. This massive stack height even bests heavier Atra classics such as the Torin 3.0 (28mm) and Instinct 4.5 (25mm). All of our testers noted the cushioning-to-weight ratio was off the charts.  

Not only was the Duo one of the lightest shoes in the cushioned category, it boosted more midsole then nearly any shoe tested, the exception being the Hoka Bondi. The downside, as multiple testers noted, the midsole flared out and would regularly scuff the inside of the calf.  Runners with low foot lift could easily clip any terrain changes; including sidewalk cracks, driveway slopes, and crested crossroads if not careful.

The contrasting stats of low weight and high stack height firmly pins the Duo up against Hoka’s Mach and Cavu neutral trainers this season, which are consequently also brand new additions this season for Hoka. All shoes have similar weight (8ish ounce range for men’s and 5.5ish ounce range for women), offer high stack heights and are designed to be performance-oriented. While the Duo doesn’t quite offer the same level of performance as the Mach and Cavu, it’s the only shoe with a zero drop.

While Altra’s zero-drop profile and wide toe box are most popular with the ultrarunning community, it’s becoming ever more common among runners who prefer shorter distances. Zero drop shoes remove assistance lifting the heel as seen in pretty much all running shoes on the market. This removal of a built-in “heel lift” allows you to maintain a natural foot position, placing the heel and forefoot the same distance from the ground, thus, according to Altra’s marketing, “naturally aligning the feet, back and body posture and encouraging a low-impact landing.”

Comfort

In an effort to keep the Duo as light at as possible the upper is made with reinforced mesh and kept razor thin.  Fully transparent when held up in the light, the Duo’s upper was by far the most breathable upper we’ve tested. Near perfect ventilation allowed excellent airflow when running in hot and humid conditions.  No heavy materials were used, only a few TPU overlays to help tighten the waist of the shoe. This well designed minimal upper offered near perfect ventilation for hot days and excellent drainage for those super wet runs.  

Despite the razor thin upper all of our testers agreed the Duo offered out-of the box comfort.  Light padding and a soft liner are placed along the ankle collar. The tongue is flexible and made with a suede-like fabric while added padding down the center helped prevent uncomfortable tension when laced up tight.

Fit

Altra approaches shoe design and fit very differently than most mainstream running brands. Instead of tapering the toe box down to a point upfront, Altra flares the toe box out. This design, which Altra coins “Foot Shape” allows the toes to relax and spread out naturally, thus enhancing stability and creating a powerful toe off. Initially, the extra space in the toe box can feel too roomy as if the shoes are too big. Multiple testers agreed, the excess space gave the shoe a loose fit, making the shoe difficult to control. However, for those who struggle finding wide enough shoes, Altra will be a Godsend.

After getting adjusted to the extra space the Duo fit perfectly. One tester did find the length to be on the shorter side, but the overall consensus was the Duo fit in-line with others tested.  The back end is outfitted with a somewhat flexible but deep heel collar pronounced with high Achilles collar. Functionally, this combo really locked down the heel.

Responsiveness

Generally speaking we’re finding cushioned shoes are moving more towards a medium firm midsole verse an ultra soft underfoot feeling to help maintain a responsive feel. The Duo balances a cushioned feeling with responsive ride perfectly.  The midsole maintains a hint of firmness without sacrificing cushioning. As one tester so uniquely put it, “They have a lot of cushion and are quite responsive. They feel like I’m wearing a thick yoga mat under my feet.”

The Duo did lack a snappy pop as found in the Hoka Mach or Cavu. Testers discovered it just wasn’t a shoe that’s quick to get off the ground. Those who tend to lean towards more of a fore or midfoot strike pattern will find the Duo more responsive then heel strikers.

Speed

The majority of our testers agreed, the Duo holds it’s own when it came to faster running. “This is a shoe that is lightweight and quick,” noted one tester. Despite the massive amount of cushioning underfoot, Altra somehow was able to maintain a weight that more closely resembles a racing flat then a cushioned trainer. As one tester so perfectly put it, “It is hard to believe that Altra can get a shoe with over 30 mm of cushioning to be this light.”

While the Duo was one of the fastest shoes in the cushioned category and could easily compete in the lightweight class. But our testers wouldn’t quite pull it out for races. The high stack height prevented a ready to rip, close to ground ride like most racing flats.

Ride Quality

One might think a wide-platformed, high stack height, zero drop shoe may run flat, but that was not the case with the Duo. It was smooth, cushioned and a pleasure to run in.  An aggressive rocker upfront coupled with a flexible midsole offered a natural and smooth transition as the foot left the ground. A slight rocker under the heel will help assist heel strikers through the midfoot, but in general, due to the zero drop the Duo’s sweet spot is certainly for midfoot or forefoot strikers.  

Deep grooves, which are highlighted in the midsole, continue throughout the outsole allowing a surprising amount of flex in the shoe. This flexing of the midsole allowed the shoe to move more naturally during the toe off phase compared to most maximum cushioned trainers.

Each summer and winter when shoe companies release their latest models Gear Institute receives the top shoes and puts each through an extensive testing process.  A team of five male and female testers put each shoe through the test of miles over terrain such as concrete, asphalt, grass, dirt and track. Each shoe is judged on five categories: Comfort, Fit, Responsiveness, Speed and Ride Quality and given a score of 1 to 10, with 10 being perfect.

Testing protocol for road running shoes involves an extensive hands-on process across multiple testers over a period of at least two months. Each tester is avid runner, running over 30 miles per week over varying terrain including but not limited to concrete, asphalt, grass, track and dirt. The testing team is structured with a team lead and several wear testers.