In part one of this topic, we looked at the main factors beginner trail runners should consider when deciding whether to opt for trail-specific shoes. This post, also intended to help beginners navigate the world of trail running footwear, outlines from the ground up the main design differences between road and trail running shoes.
(Although beginner trail runners should be aware of the ongoing debate regarding barefoot running, a discussion of that topic is beyond the scope of this post.)
Context
Let’s first briefly revisit the obvious but important point that wilderness trail surfaces aren’t like typical paved or concrete running surfaces. Road running is done on surfaces that provide a consistent, predictable landing pad, while high-leverage trails do not. High-leverage trails are often covered in moisture or loose dirt, or littered with stationary obstacles like roots and rocks. The vertical slope and horizontal tilt typical of high-leverage trails pose additional challenges.
What does this mean for shoe design?
For starters, it means the organizing design principle for trail shoes is fundamentally different from that of road shoes. The “problem” road shoes are designed to solve is at the intersection of repeated hard-surface impact and the individual runner’s biomechanics. Given the nearly identical impact of each foot strike, the primary risk of injury to a road runner is obviously that of repetitive stress.
The approach taken by road shoe designers is to provide considerable cushioning, which is often supplemented with features intended to manage the idiosyncratic running action of different types of runners. Over time, road shoes have evolved into the categories motion-control, stability, and neutral, which are fairly well-defined and understood by most experienced runners.
By contrast, trail running shoes are designed primarily to respond to the trail itself and only secondarily to the runner’s profile and running style.This makes sense for a few reasons.
First, wilderness trails are almost always softer than pavement or concrete, which reduces the impact force of each footstrike. There’s simply less call for cushion.
Second, the biomechanics of the runner’s stride are largely thrown out of their normal repetitive consistency by the trail’s constantly changing nature (unless it’s a really boring trail). Running on some trails looks a lot less like what you see at the Boston Marathon and a lot more like what you see during a punt return at a football game.
Finally, traversing unpredictable wilderness trails at speed considerably increases the risk of injury from a single violent trauma like a sharp poke to your sole, a twisted knee or ankle, a stubbed toe, or a fall.
With this background established, we are now ready to explore the technical differences between road and trail running shoes.
Outsole
Having good traction makes all the difference when you come to a slippery, treacherous section of trail: good trail shoes allow you to confidently attack terrain you otherwise would have to tip-toe gingerly across. Since trail shoes need much better traction than road shoes, their outsoles typically are made from much stickier rubber compounds.
Most also have fairly substantial lugs designed to hook up in loose dirt conditions. However, a deep-lugged tread is not a universally desirable characteristic. Larger lugs sometimes translate into a higher, less stable ride. Also, for exceptionally smooth trails and those featuring a heavy dose of rock, a relatively bald outsole will provide more shoe/trail contact and, therefore, better traction. Beware, also, of lugs that are spaced close together, since mud will tend to get packed in the spaces between them, whereas wide-spaced lugs will be more likely to shed mud. For these reasons, I generally recommend selecting a tread design that provides as deep a lug as the terrain demands and no more.
The rubber compounds used in the outsoles of trail shoes are, as a rule, much denser than those of road shoes. This greatly improves durability and provides a protective barrier between your foot and sharp objects.
Midsole
The midsole of trail running shoes tends to be more protective yet less cushioned than road running shoes. This is primarily a function of the density of the materials used, but the midsoles of many trail shoes also incorporate a rock plate.
Many trail running shoes have a relatively thin midsole, which reflects the preference, nearly universal among trail runners, for a lower, more tactile feel of the trail surface. A thicker midsole adds height and reduces stability, which dampens trail-feel and makes twisted leg joints more likely. In addition to riding lower than comparable road shoes, trail shoes tend to be a bit wider than their road cousins for the same reason.
The combination of a low, confident ride and dense midsole materials means that a trail shoe will generally feel considerably stiffer and more stable than a comparable road shoe. For this reason, it is common for a trail running shoe that feels “in tune” on a technical trail to feel a bit stiff on pavement. It’s a bit like driving a Jeep.
Upper
The uppers of trail shoes also feature a variety of distinguishing elements. One of the most important is the stout toe bumper built into trail shoes. The violence of a stubbed toe mid-trail run is impressive. When it happens — and it will happen — you will be glad to have just a bit more protection where it counts. Most trail shoes also feature a gusseted tongue or “scree guard” to prevent debris from infiltrating the shoe.
Since water is a common element on many trails, the use of Gore Tex or other waterproof membrane is more prevalent in trail shoes than road shoes. However, most trail runners prefer to manage water not by trying to keep it out of the shoe, since that is often futile, but by opting for an airy, well-draining, quick-drying upper.
If you aren’t sure whether your trail conditions call for Gore Tex, consider the rule of thumb that a waterproof upper is better at managing snow and general slop than repeated crossings through shin-deep water.
Bottom Line
All the individual choices that go into the design of road and trail running shoes add up to a pretty significant difference in the way they each perform. In general terms, trail shoes tend to offer a ride that is noticeably lower, firmer, and more stable than road shoes. They also offer improved traction and protection…but not cushion.
Although trail shoes tend to be heavier than comparable road shoes, due primarily to the density of the materials used in their mid- and outsoles, there are plenty of models of hardcore trail shoes that are not particularly heavy or “hiker-y.” Although it is hard to generalize, the typical weight difference between a trail running shoe and a comparable road shoe is in the range of 1-2oz.
That said, when it comes to choosing a trail shoe, I would suggest that trying to link a given road shoe to its trail counterpart is a nearly pointless exercise, since the categories distinguishing trail shoes are considerably less clear-cut than for road shoes and relate to terrain as much as to the biomechanics of running. Like learning any new language, your fluency in trail will really improve as you are able to skip the step of translating in and out of road.
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