We spent 8.6 hours reading reviews from experts and users. In summary, this is what runners think:

5 reasons to buy

  • Most reviewers commended the grip the outsole provided. They expressed that they did not experience slipping and sliding as much as other Tough Mudder competitors. Another runner said that the grip was also sufficient on uneven terrain.
  • One user said that the laces did not unravel throughout the competition.
  • A good number of testers observed that the shoe was draining well.
  • The weight was light but the midsole still had enough cushioning for long runs on moderate terrain, said one runner.
  • The shoe is reasonably-priced.

2 reasons not to buy

  • Debris easily got into the shoe through the ankle area, based on a good number of reviews. This caused one runner to feel pain while running downhill.
  • One runner said that the collar rubbed on his ankles causing tender spots.

Bottom line

The Merrell All Out Crush Tough Mudder 2 was specifically designed for the Tough Mudder Competition. Users who used it for that purpose said that the shoe performed well, and took on the demands of the trail. Water was even draining well from the shoe. However, one major drawback some reviewers found was that pebbles and debris easily got into the shoe which caused some discomfort.


Terrain: Trail
Arch support: Neutral
Weight: Men: 8oz | Women: 6.7oz
Heel to toe drop: Men: 6mm | Women: 6mm
Pronation: Neutral Pronation
Arch type: High arch
Material: Vegan
Strike Pattern: Midfoot strike
Distance: Competition
Heel height: Men: 22mm | Women: 22mm
Forefoot height: Men: 16mm | Women: 16mm
Brand: Merrell
Type: Low drop
Width: Men: Normal | Women: Normal
Price: $100
Colorways: Orange
Small True to size Large
See more facts


A top 6% best Trail running shoe
A popular pick
Better rated than the previous version Merrell All Out Crush Tough Mudder

Expert Reviews

Experts are runners, who post reviews at youtube, directly at RunRepeat or at their own websites. Each expert is categorized from level 1 to level 5 based on expertise. See stats on expert reviews and how we calculate scores here.

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80 / 100 based on 1 expert reviews

  • 80 / 100 | Rocket Runner | Level 2 expert

    Four stars for Tough Mudders only.

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  • Merrell’s All Out Crush Tough Mudder 2 is vegan-friendly. It uses 0% animal products while still delivering sturdiness, comfort and style.
  • On the heel area, a Lycra Neoprene lining was added to supply the runner with additional comfort during trail runs.
  • An extra layer between the midsole and the outsole was added for extra protection. The layer is called Trail Protect Pad, and its main purpose is to shield the bottom of the foot rocks and other debris a runner can step on during trail runs.
  • The outsole is made of a material called M Select Grip. It supplies enough grip to conquer different terrains. Runners don’t have to worry about slipping even when running on wet trail. The design is also self-cleaning, with strategically placed lugs.

The Merrell All Out Crush Tough Mudder 2 is available in regular sizes. Runners will be able to purchase the shoe in their usual size preference. In terms of width, the shoes come in the standard B-medium and D-medium measurements.

On the outsole is Merrell’s M Select Grip which is a durable rubber that’s wear and tear resistant. Aside from its durability, it grips on both wet and dry ground and adapts to terrain that’s uneven. This is made possible by the strategically-placed lugs which can grasp unto the ground easily. This Merrell technology is also placed in the outsole of the popular Merrell shoes for running.

How the semi-aggressive lugs are placed, plus the additional rectangular ones on the side complement the M Grip when it comes to producing in enough traction needed for different terrain conditions, including ones that are more technical. Because the lugs are spaced properly, particles won’t easily get stuck underneath the shoe. The design is also self-cleaning, so runners don’t have to worry about debris getting stuck at the bottom.

Several Flex Grooves have been incorporated into the forefoot area of the outsole to promote flexibility. This design feature allows the forefoot to bend and prepare for the propulsion phase of the running gait cycle. Because the forefoot can move naturally, runners can move forward optimally.

The midsole is made of Ethylene-Vinyl Acetate or EVA. It runs the shoe’s full length and its main purpose is to provide cushioning and shock attenuation throughout the run. It delivers sufficient responsiveness, allowing the runner to feel energized with every stride.

To protect the foot from debris and other objects that a runner can step on while trail running, a pad called Trail Protect was added. It sits between the outsole and midsole. Its thickness complements the cushioning of the midsole and robustness of the outsole to lessen the impact of debris on the trail.

An EVA footbed was integrated onto the platform. It is mainly for additional cushioning and enhanced comfort underfoot.

The upper is made up of a material called mesh. It’s stretchable, molding to the shape of the foot and delivering a custom feel. It’s also breathable, easily permitting air to pass through to keep the foot cool and dry at all times during the run.

To strengthen the mesh material on the upper of the Merrell All Out Crush Tough Mudder 2, it was reinforced by a material called Thermoplastic Polyurethane or TPU.  It is a material that’s resistant to oil, grease and abrasion. As it protects and reinforces the mesh material, it’s flexible enough to allow natural movement.

On the heel is a Lycra Neoprene Heel Lining which was added to improve the comfort delivered on the heel. Generally, Neoprene is a material used in wetsuits. However, in this shoe, it acts as an impact protector on the heel that’s resistant to tearing or cracking.

The All Out Crush Tough Mudder 2 has a traditional lace up closure. Tightening up the laces will secure the fit on the midfoot and prevent the shoe from accidentally sliding off during a run.


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.