Matryx uppers are making trail running shoes lighter than ever – here’s everything you need to know about this revolutionary fabric

As an outdoors journalist, I get to test a lot of the best trail running shoes , and in doing so, I have developed a whole new vocabulary. Where I once thought there was just a sole I've learned there is in fact a grippy outsole and a midsole – that wedge of cushion usually made with EVA foam which can ensure you don’t end up with sore feet after a long day on the trail. Tongues can be gussetted which helps keep debris out when you’re on loose terrain like desert trails or scree and it turns out those extra lace holes ensure a good lockdown fit. Oh and don’t even get me started on the virtues of a wide toe box .

In addition to all that, as I’ve learned, if you want a good run, you also have to pay attention to the upper, which is basically everything above the midsole. This needs to be breathable , otherwise you’ll be checking that your feet aren’t smoking after a few miles, and flexible enough that your foot isn’t restricted while you’re running. However, it also needs to give your feet really good protection against trail hazards like sharp rocks which can cause some serious damage to your toes. That’s a lot to live up to.

Lately, I’ve been seeing more and more shoes using Matryx fabric for the upper, and when I received a pair of the Merrell Long Sky 2 Matryx to test this year, I started to think that running shoe brands might really be onto something. After all, the Long Sky 2s are impossibly light and airy but have protected my toes on trails from Gran Canaria to Verbier . It’s also popped up in the Salomon Genesis , which were highly rated by my colleague Pat Kinsella, so I decided to dig in and find out a little more about this fabric technology, and why it’s so great for trail runners.

What is Matryx fabric?

Matryx is a patented performance fabric made in France from recycled yarns by a textile company called Chamatex. According to a 2018 video launching the fabric, Matryx begins by first twisting threads of polyamide and ultra-tenacious Kevlar together. These threads are then coated in polyurethane, which reportedly enhances both abrasion resistance and breathability.

Once the threads have been created, they are woven together to create the material for the upper, sometimes with the addition of yarns of carbon fiber, monofilament, silicone, leather and other materials to fulfill the specifications of the product. So, it turns out that a Matryx upper can actually vary in terms of both composition and weave.

It looks and feels like a very thin and light mesh fabric – when I pull on the uppers of my Long Skys, there’s little give but it feels extremely flexible and when I hold it up to the light I can see that it’s also very porous.

Why is Matryx so great for trail running shoes?

Matryx uppers appear in shoes built for hiking, tennis, rugby, cycling and athletics, but we think it offers some distinct appeal for trail running, where you’re usually going for long distances and therefore seeking to shed weight, but also need something that can hold up to the demands of rock and roots.

These are some of the advantages of Matrux upper for trail running shoes according to Chamatex:

• Extremely light (my Merrell Long Sky 2 Matryx are just seven ounces per shoe)
• Flexible, which allows your feet to move naturally
• Offers lateral support when you’re crossing uneven ground
• Breathable in warm weather
• Tough and durable against rough trails

In addition to their contribution to performance, Matryx uppers have some good sustainability credentials, which is hugely important to the average trail runner. The fabric is made with recycled yarns which are dope dyed , which as I’ve previously written uses far fewer resources than traditional dying methods and is more energy efficient.

Furthermore, Salomon reports that the Matryx yarn production, weaving and finishing facilities, and research and design lab are all located within a 50-mile radius of each other which reduces the environmental impact of shipping and transport.

Are there any disadvantages to Matryx uppers?

Matryx fabric was developed in 2017 so it’s still early days and as of yet, the only disadvantage I can find from personal experience is that shoes that use it tend to be higher-end and therefore pricey.

Remember, however, that just as a waterproof jacket using a Gore-Tex membrane can still let in water if it doesn’t have features like fully taped seams and a storm flap, a shoe using Matryx is only as good as its construction, so always look at the full picture, and check that it has good grip and fits your foot well. Oh and be sure it has a wide toe box.

• How should trail running shoes fit for the best comfort?