The North Face Ultra Cardiac is one of those shoes that quietly and unassumingly just gets the job done, with no unnecessary fanfare. There is nothing about the Cardiac that stands out as particularly great, but there is nothing about it that is particularly bad either. Overall it is a comfortable, well-fitting shoe that sits nicely in the middle between soft and flexible on the one hand, and stiff and responsive on the other. In fact, the overall balance of the shoe might be its standout characteristic. This balance also makes for a very versatile shoe that can handle a wide range of speeds and terrain. 

The main drawback with the Cardiac is that it is not really an appropriate shoe for highly technical and demanding trail. The outsole lugs are fairly low profile, which aids runnability but also reduces traction, particularly on loose surfaces like scree. The other issue is that the Cardiac does not have a lot of protection – certainly more than a trail flat, but definitely less than the more rugged shoes in the mid- to heavier weight category. The lack of a significant toe bumper makes the Cardiac a risky shoe to wear on rocky trails. 

The Cardiac will appeal to recreational and mid-pack runners looking for a “do-it- all” daily trainer. It also is a viable long run shoe for more performance oriented runners. However, the short outsole lugs and limited protection make it unsuitable for highly technical terrain. 

Comfort 
The Cardiac is a comfortable shoe from heel to toe and top to bottom. It is not a plush shoe, but the cushioning feels good underfoot. For some runners, the narrow toe box may be an issue.  

Speed & Agility
The Cardiac does not have the most responsive midsole, but it is slightly better than the flat cushioning that is often found on shoes in this category. The Cardiac’s turnover is somewhat enhanced by the larger heel-to-toe drop. Agility is average and in testing there were no foot placement issues. 

Security of Fit
The Cardiac has an excellent fit through the midfoot area due to the more contoured, hourglass-like shape of the shoe. This helps keep the foot in place, particularly in the lateral direction. Lock down was also excellent in the heel and in the forefoot, with what would be considered a normal amount of lace pressure. 

Responsiveness
Heeluxe, our shoe testing laboratory partner, tests the responsiveness of a shoe by measuring how thick a running shoe is and multiplying it by how much pressure the forefoot foot feels while running. The softer or thicker the midsole, the less responsive a shoe will feel, but the more comfortable the shoe will generally feel. The thinner or firmer a midsole is, the more power you’ll feel at toe-off.

Stability
Because of the fit, the Cardiac has a fair amount of natural stability. The full-length vibram outsole mitigates the lack of a rockplate and stiffens the overall platform. The upper is fairly structured which stiffens the overall platform and helps eliminate unnecessary foot rotation. 

Over the course of a few weeks, our wear-test team does multiple runs in each pair of shoes they test.  They aim for a variety of runs (easy recovery runs, long training runs, harder race-pace efforts) across as many different types of trails as they can manage.  The team is spread across the country, so we are able to test under a variety of different conditions, terrains, and types of trail, from gently-rolling fire roads to highly technical mountain singletrack.