Verdict from 2 experts and +100 user reviews

7 reasons to buy

  • The Altra Instinct 4.5 effectively stopped recurring toe pain, according to a user.
  • The cushioning was perfect for long-distance runs, a runner stated.
  • One reviewer claimed the shoe had a soft and plush midsole.
  • Various wearers agreed that the Instinct 4.5 had a roomy toe box.
  • The tongue was adequately padded, which provided ample comfort, said a tester.
  • Some runners appreciated the extra eyelet that allowed for a more secure fit.
  • A customer wrote that the Altra Instinct 4.5 gave a smooth and stable ride.

3 reasons not to buy

  • The shoe rubbed uncomfortably on the inside of the foot, a buyer observed.
  • The heel was too large and loose, and it had a challenging time stopping the foot from slipping, a number of wearers complained.
  • One commenter wrote the padding wore down very quickly.

Bottom line

Based on the comments of many wearers, the Altra Instinct 4.5 is a running shoe highly recommendable for people with high-volume foot. The roomy toe box, spacious in-shoe environment, and comfortable platform were all positives that were highlighted by users. Overall, it was a satisfactory shoe that many found to have done the job as a daily runner.

Tip: see the best running shoes.

Good to know

  • The weight of this version of the Instinct has been made lighter. The Altra Instinct 4.5 has a reduced weight of 278g or 9.8oz. It’s 6g lighter than its predecessor, the Instinct 4.0, which weighed 284g.
  • The stack height has also been slightly reduced. Instinct version 4.5 possesses a 24mm stack height which is 1mm lower than its former version. Despite this slight decrease, the midsole still maintains its zero heel-to-toe offset to maintain the runner’s feel of the ground.
  • A few design updates have also been incorporated. The most noticeable is on the upper which now has a more modern look. The midsole has been redesigned as well to look updated and faster.

The Altra Instinct 4.5 is only available in men’s sizes. Male runners who wish to have their own pair can make use of their usual size preference. The width also comes in the standard measurement of D – medium.

The Altra Instinct 4.5 sports a full-length rubber outsole. Because the entire bottom part of the shoe is covered with rubber, it ensures that enough protection from wear and tear is delivered.

The tread pattern is unique because it maps out the bones and tendons underfoot with different colors of rubber, as well as several flex lines and grooves. The Altra logo has been incorporated into the tread, but other than that, the design underneath looks anatomically accurate. This is called the FootPod Outsole. With this design, the runner’s foot is not hindered from moving naturally.

The midsole of this Altra shoe features a zero heel-to-toe drop. The heel and forefoot on the platform have the same distance from the ground. Because of this measurement, runners will get a better ground feel. It also promotes natural alignment of the body and a landing which has a lower impact on the joints.

EVA, which is short for Ethylene-Vinyl Acetate, makes up the midsole of the Altra Instinct 4.5. The material attenuates shock accordingly while delivering the right amount of response and energy return.

A top layer was added on the EVA platform to provide extra protection from hard surfaces. Altra calls this layer A-Bound cushioning. It is made of recycled materials. Not only does it offer better defense underfoot, but it slightly enhances energy return from landing.

On the sides of the midsole, grid-like grooves were added. These grids and lines are called Innerflex. The design slightly lightens the weight of the shoe and enables the platform to have more flexibility. With this in place, the midsole performs better allowing runners to reach faster speeds.

The upper is made of Engineered Mesh. The material is structured without compromising breathability. These characteristics afford the runner lesser hot spots and a better fit, which results in a better feeling of security.

The same as the Paradigm 4.0, the Altra Instinct 4.5 was designed with Altra’s FootShape Toe Box. The toes have enough room to relax and spread out naturally because the design of tip of the upper is similar to how the toes aligned. The big toe remains in a straight position for more power during toe-off, and better balance during landing.

There is a 6mm contoured insole. The extra layer adds a bit more cushioning and protection underfoot. Because it is contoured, it follows the natural curves of the underfoot, delivering a more comfortable feel plus a snugger fit.

Jens Jakob Andersen
Jens Jakob Andersen

Jens Jakob is a fan of short distances with a 5K PR at 15:58 minutes. Based on 35 million race results, he's among the fastest 0.2% runners. Jens Jakob previously owned a running store, when he was also a competitive runner. His work is regularly featured in The New York Times, Washington Post, BBC and the likes as well as peer-reviewed journals. Finally, he has been a guest on +30 podcasts on running.