Mysteries of the Running Shoe Revealed
Delve into the depths of your running shoe to better understand how to find and purchase your ideal pair.
Posted Saturday, 25 April, 1998
So you walk into the running store. You look here, you look there. There's so much variety that the shoes pile up like some perverse Cinderella story. They all look spiffy enough. They all seem to have enough of that cushioning-gel-air stuff. How different could they be?
If you put that question to a salesperson, depending on the store, you'll get either a shrug or a lecture on medial posts and curved lasts and ethylene vinyl acetate. And you might get some questions, too -- about the altitude of your arch, the heft of your heel strike, and your proclivity for pronation.
Whew. Shoes are a lot more complicated than they used to be. But since there's nothing that gives the folks at Cool Running a warm-all-over feeling more than seeing educated consumers in action, we've put together a few pointers.
What are the choices?
For most recreational runners, a basic training shoe is all you'll need. Others, however, have specialized interests and thus need specialized shoes. Here's a look at the different flavors.
The vast majority of running shoes out there are basic training shoes. More than anything else, trainers are built simply for protection -- protection from constant pounding on hard surfaces and from your foot's own instabilities. Compared to light trainers and certainly to racing flats, these shoes are tanks. Heavy and loaded for bear, they're built to last through the miles.
Most runners don't need any other type of shoe. While lighter shoes will let you run slightly faster (about a second per mile faster for every ounce), the injury prevention of trainers should be the big draw for most runners. And with the greater variety among training shoes, you stand a better chance of getting the right match for your foot.
Lightweight training shoes are a good middleground between trainers and racing flats. For those who want to slice a little time off their race speed, light trainers are a good way to go without sacrificing too much protective cushioning. It's really only worth the sacrifice, however, if you are a competitive runner racing with at least a seven-minute-per-mile pace. If your races are longer than 10K, stick with regular trainers; cushioning is likely to be more important than light shoes as the miles stretch on.
Be aware that because light trainers have less cushioning than trainers, their cushioning wears out faster. If you are going to buy these shoes, try to use them almost exclusively for racing, and stick with the trainers for the rest of your running. Do be sure, though, to break in your light trainers with some short runs and speedwork before taking them to the races.
Racing shoes are built strictly for speed. To increase flexibility and reduce weight, they have about 15 percent less cushioning than trainers and reduced support and durability. Often they have less heel lift, too, which makes for added strain on the Achilles tendon. The reduced protection of racing flats increases the risk of injury and makes them really suitable only for the hard-core competitive racer. For these runners, though, the benefits can be substantial since these shoes are typically three or four ounces lighter than trainers. Theoretically, the weight difference could take twenty to thirty seconds off of a 40-minute 10K time.
Racing flats should be used only during races. During your training runs, pamper your feet with the extra protection of a good pair of trainers. As with light trainers, though, you should break in your racing flats with some short runs and speedwork before wearing them to the starting line.
As more and more runners fall sway to the call of the wild, interest in trail shoes has increased dramatically in recent years. Once upon a time, trail shoes were just slightly modified hiking boots. No longer. Heavy, water-absorbent leather has given way to light, breathable nylon mesh. The high-top boot has been transformed into a trail shoe that looks like, well, a running shoe.
Trail shoes are designed primarily for extra durability, traction and stability to handle the rough, uneven terrain of trails. While many basic training shoes cut weight by eliminating the durable outsole around the midfoot, trail shoes have a hard rubber outsole along the entire length of the shoe. Their treads have deep, toothy lugs to carry you safely through the mud of the great outdoors.
Unless you do almost all of your miles on trails, however, you may be better off using regular trainers. Trail shoes are not essential to trail running, and because there are far fewer models available than for training shoes, it may be more difficult to find a shoe that fits your biomechanical needs. If, however, you find yourself logging most of your running time out in the woods, you may be well served by picking up a pair of trail shoes.
What makes these things tick?
Every model of running shoe is designed for a specific type of foot. There are engineers who likely toil through the night doing God-knows-what just to build a shoe that will neutralize the flaws and imbalances in your specific foot type. The difficulty, of course, is figuring out which shoe is the one for you. The more you understand about how running shoes are constructed, the better you will know what to look for at the store. Herewith a quick primer on the anatomy of the running shoe. We'll start from the bottom up, literally.
The very bottom of the shoe. This is the shoe's first defense against the pounding you put it through -- literally where the rubber meets the road. The important features here are durability and traction. While the outer sole should be durable, be aware that harder soles tend to be heavier and have less cushion than softer ones. Ultimately the exact design of the treads are not terribly important. For all the variety in sole designs, from simple to outrageously complex, most have an equally good grip.
The midsole is where the important stuff happens: the cushioning. Stuffed between the outersole and the foot bed, it is constructed of different kinds of foam, sometimes sharing space with capsules of air or gel to increase the cushioning. Obviously, the softer the midsole material, the more cushioning and the softer your ride. You can compare midsole softness among different shoes simply by squeezing the midsole with your thumb at both the heel and forefoot -- the greater the indentation, the softer the midsole. Keep in mind, however, that a soft midsole will compress and grow flat faster than a more rigid material.
Along with good cushioning, the midsole should also provide good stability and adequate flexibility in the forefoot, around the balls of your feet. These last two features, though, tend to fight each other. A soft midsole allows flexibility at the expense of stability. The key, of course, is to find the right balance for you.
The last is the inside shape of the shoe, which is designed around a three-dimensional model. There are three basic shapes that the last might take: straight, curved, or semi-curved. When looking at a shoe from the bottom, a straight last is one that is symmetrical relative to a line drawn from the middle of the heel to the middle of the toe. A curved last curves markedly inward at the insole. The semi-curved last, as you might guess, splits the difference with a slight curve at the insole.
A curved last makes for a more comfortable ride for runners with rigid, high arches who need more shock absorption and foot movement. A straight last, on the other hand, has more material at the midsole, offering added support for runners with low, flexible arches or those who tend to over-pronate. The semi-curved last is good for those with a normal arch and neutral foot motion.
The way that the rest of the shoe is attached to the last is also important. The three techniques that are used are called slip lasting, board lasting and partial or combination lasting. In slip lasting, the upper materials of the shoe (the part that fits over the top of your foot) are pulled over the last and glued or stitched directly to the midsole. In board lasting, however,the upper is attached to the bottom of a flexible board atop the midsole. Partial or combination lasting uses the board method in the heel and the slip method in the forefoot. The way to tell what construction a shoe uses is to remove the shoe liner: if you see stitching, the shoe is slip-lasted; if you see a board and no stitching, the shoe is board-lasted.
The difference is that the board-lasted shoe makes for a more rigid and stable shoe for runners who over- or under-pronate, or who wear orthotics. Slip-lasted shoes are good for those who have rigid feet and need more freedom of motion; it also makes for a lighter shoe. The combination last, of course, provides the benefits of both worlds by providing stability in the heel and flexibility in the forefoot.
The stiff material at the back of the shoe is built to resist too much motion in the ankle. If you overpronate, you should look for a rigid heel counter. Give it a squeeze to see how firm it is. At the top of the heel counter is usually a chunk of padding called an ankle collar which is intended to protect cushion the ankle and the achilles tendon.
This is the portion of the shoe that covers the top of your foot. The uppers of almost every running shoe are made of nylon or nylon mesh, which is lightweight and breathable and, unlike leather, doesn't stretch when wet.
Know your foot
In order to pick the right shoe, you have to know a bit about your foot. Not to fetishize, it's a rare thing to lay eyes on a perfect pair of feet. There are very few runners lucky enough to have feet so biomechanically efficient that they distribute weight perfectly from heel strike to toe off. The rest of us depend on our running shoes to neutralize the flaws in our sadly imperfect feet. Understanding the structure of your foot will help you understand the type of running shoe you need.
You can easily determine your foot's general type with two simple tests. This first diagram should help you decipher the wear patterns of your running shoes:
To double-check, give yourself the tried-and-true "bathroom test." When you get out of the shower with wet bare feet, take a look at your footprint:
You over-pronate when your feet roll in when you run, and you supinate when your feet roll out. It's natural to pronate somewhat when you run, but many runners have feet that simply overdo it. Take a look at the bottom of your running shoes. If you are an over-pronator your shoes will be more worn on the inside edge of your shoes than the outside edge. In severe cases, the shoe will actually slope dramatically inward. You may have trouble with shin splints or runner's knee. Over-pronation is a symptom of highly flexible feet that need a little help from their running shoes to maintain stability. For added motion control in your shoe, you will generally have to sacrifice a certain amount of cushioning. Rest assured, it's worth it.
Specifically, you should look for a shoe with a firm midsole, especially on the inner side of the shoe. The shoe should have a straight board last and a rigid, durable heel counter. A good arch support might be helpful.
Supination is the opposite problem. Your foot rolls outward when you run, and you can tell by the fact that the soles of your running shoes are worn and compressed along the outside edge. Supination tends to put too much stress on the bones, tendons and ligaments on the outside of the foot. Because you don't pronate enough, your foot is doing a lousy job as a shock absorber. You may have trouble with ankle sprains, plantar fasciitis, iliotibial band syndrome and knee pain. Supination happens pretty much exclusively to runners with rigid feet, often with high arches. You need a flexible shoe that will give and bend where your rigid foot will not.
Look for a shoe with a very soft midsole -- it should compress fairly easily with your thumb. There should be very good cushioning in both the heel and forefoot. The heel counter should be flexible and essentially useless -- not rigid. Finally, the shoe should have a curved (or semi-curved) slip last.
The neutral foot.
Here, you don't need to worry much about stability or motion control. Your foot handles the job just fine on its own, thank you very much. In fact, too much motion control may actually screw up your foot's naturally smooth action. Look for a nice, cushioned ride with a shoe that has a semi-curved slip or combination last.
The moment of truth
Now that you're well versed in shoe construction, not to mention the construction of your own foot, you're ready for the shoe store. Wondering what to do when you get there? Check out our tips on closing the deal and on caring for your new purchase