Which running shoes should I buy?

© Tim Lloyd

Extract taken from Smart Running by Jen and Sim Benson.

With running, our shoes are perhaps the most important item of kit to get right. They create the interface between our feet and the ground, giving us feel, grip and protection. Most runners are on a constant mission to find the right shoe, but with a little patience and experimentation it is possible.

All running shoes have a grippy outsole, usually made from a mixture of natural and synthetic rubber. The exact rubber compound gives a level of grip and durability appropriate for the shoe’s specific use. The tread pattern is then created to work with the terrain the shoe is designed for: a shallow, even tread for use on roads, through to deep studs with wide gaps for the best grip in mud.

The midsole of the shoe offers cushioning and protection from the ground. It is normally made from ethylene-vinyl acetate (EVA) foam or similar and sometimes incorporates a rock plate to protect the foot from sharper ground or a sprung plate designed to improve energy return. The midsole creates the stack height of a shoe which is the distance between the ground and the base of the foot. A larger stack height can provide more cushioning and protection from hardground, but this comes at the expense of stability and ground feel. The stack height can differ across the shoe – it is often listed in millimetres at the forefoot and under the heel. The difference between these heights is known as the drop.

The insole is the removable foam layer that sits inside the shoe under your foot. This provides underfoot comfort and can allow fine tuning of fit by using a slightly thicker or thinner insole. Some runners use custom insoles or orthotics; if this applies to you, make sure that the insole can be removed and that the shoe fits with your preferred insole.

The upper of a running shoe protects the foot and holds it securely to the sole. It’s normally made from a lightweight nylon mesh or fabric and more structural nylon webbing joining the lacing to the sole. A plastic heel counter provides the shape and structure of the heel. The rear of the shoe is normally lined with a polyester or nylon fabric with some thin foam padding to increase comfort. The rubber used on the outsole is sometimes curled around the front of the shoe to create a durable and protective toe bumper. Thermoplastic polyurethane (TPU) is often used to overlay the mesh or fabric to provide more structure and increase durability, protection and water resistance. The tongue is padded to protect the foot from the lacing.

Running shoes are normally fastened with laces that allow a variety of lacing patterns (see page 178) and good fit adjustment. Sometimes quick-lacing systems are used which fasten with the pull of a toggle or the turn of a dial.

How to choose the perfect running shoes

Here are the most important factors when choosing running shoes.

Fit

A perfect fit is essential for comfort and safety when you’re running. Shoes come in a vast range of sizes and shapes, so it’s a good idea to visit a specialist running shop where you can try on a variety of brands and models in a range of sizes to find the one that works for you. Try shoes on with your favourite running socks and take them for a short jog to test them out; most good shops will have a treadmill or an outdoor space where you can do this. If you use a specific insole or orthotic, make sure you take these along when you’re trying out shoes.

Sizes

Running shoe sizes may not match your usual shoe size – it’s quite normal to need go up a half size or so. Check there’s a good thumb-width of space in the front so your toes don’t hit the ends when you’re running downhill. Your heel should fit comfortably and securely without lifting inside the shoe as you run. The shoe should feel like it flexes in the right place for your feet, and once laced up your foot shouldn’t move about or feel painful or restrictive. If anything feels uncomfortable when you’re trying a pair of running shoes on in a shop, it probably won’t get better a few miles down the road. If you can, always try shoes on in the afternoon, ideally after a run, as this is when your feet will be at their largest. Sounds odd, but it’s amazing how much difference it can make. Also, high-mileage training, pregnancy, weight gain and aging can all increase your shoe size, especially if you have higher arches.

Function

Alongside the perfect fit, your shoes should match the kind of running you’re planning to do. For this reason, many runners have a fleet of shoes that they can switch between depending on the terrain and conditions. Particularly if you’ll be heading off-road, the combination of the tread pattern and rubber compound will dictate the amount of grip and the terrain a shoe is best suited to. In general, a harder rubber compound with a shallower tread will be more durable on hard-packed trails; a harder rubber compound with a deeper tread will offer better grip on mud and grass; and a softer rubber compound will grip better on rock, but won’t be as durable. Getting the grip right will make your run safer and more enjoyable.

Shoes for ultras

If you’re planning to run a long way, like in an ultramarathon, you may need to size up more than you would do for your normal running shoes. This is because your feet swell with the prolonged weightbearing and inflammation associated with hours of impact and friction. Jen says:

‘Finding the perfect shoe and sock combination for a mountainous, potentially wet and boggy ultra was an interesting process of trial and error. In the end, Injinji toe-sock liners, Sealskinz waterproof oversocks, La Sportiva Mutant trail shoes and Kahtoola debris gaiters provided the perfect solution, alongside copious amounts of Squirrel’s Nut Butter to lubricate my feet.’

Different types of shoes

Road shoes

These have a shallow tread with lots of rubber-to-ground contact to give good grip on road and hard surfaces. The midsole needs to offer enough cushioning to cope with the repetitive impact of a regular stride on a consistent hard surface. The upper doesn’t need to offer much protection but needs to hold the foot securely.

Trail shoes

These have a deeper tread than road shoes but still offer plenty of rubber-to-ground contact to provide good grip on gravel, rock and surfaced trails. They will also work well on dry grass and dirt but will normally start to struggle in mud. The midsole needs to offer enough cushioning to cope with hard trails. A stiffened rock plate is sometimes used to protect the foot from sharp rocky ground. The upper must protect the foot from kicking stones so will often have a toe bumper of some type.

Fell shoes

These are designed for off-road and off-trail running. They have deep, well-spaced tread to provide good grip in mud and on wet, grassy surfaces. The softer compound rubber that they use will also grip well on rock but will wear out quickly if worn on harder trails or the road. The midsole doesn’t need much cushioning because these shoes are designed to be worn on soft ground. A low stack height and low drop is often used to prioritise stability and lower weight – the drop of a shoe doesn’t make as much difference to running gait when running on soft ground. The upper of a fell shoe needs to protect the foot from the uneven, rocky and pathless terrain it is designed for so they will often feature a toe bumper and some increased foot protection around the sides.

All weather, all-terrain shoes

Some running shoes have a waterproof lining, often Gore-Tex, which is usually a full sock membrane that is fixed between the inner and outer layers of the upper and under the insole. A waterproof shoe will be warmer, heavier and more expensive than a non-waterproof shoe. It will often have a slightly snugger fit than the non-waterproof version of the same shoe due to the extra layer of material. A waterproof shoe can be good in the winter when running on roads, trails and through short grass, but it’s not so good if water is likely to go over the top and into the shoe. A waterproof shoe can’t drain so once you have wet feet you will continue to run with your feet in a puddle which is heavy and uncomfortable. For this reason, fell shoes are very rarely waterproof. Waterproof shoes will take longer to dry after your run.

Snow and ice shoes

Shoes designed for use on snow and ice have small metal studs incorporated into the tread to add grip on icy surfaces. They work very well if you do regularly find yourself running on icy roads or trails, but you can’t really use them in any other conditions so microspikes or nanospikes (detachable spikes, a bit like a lighter-weight version of crampons) may be more versatile for most runners. The uppers of these shoes tend to be waterproof and have slightly more insulation than normal trail shoes to help keep your feet warm. You will probably wear thicker normal or waterproof socks with this style of shoe so you may need to size up – it’s best to try them with your preferred socks.

Super shoes

Running shoe design is evolving all the time, as brands in a highly competitive industry strive to get the edge over all the others. In 2017, Nike brought its ‘supershoe’, the Vaporfly 4%, to market, leaving other brands– and any runners not wearing the shoes – trailing in its wake. All three male medallists in the 2016 Olympic marathon wore a prototype of the Vaporfly 4%.

Nike’s claim that the shoe’s design improves the running economy of highly trained runners by four percent – equating to an improvement in performance of between two per cent and three per cent – seems to have been borne out by results over subsequent years. Since 2016, top 50 male marathon runners’ times have improved by about two per cent on average, while for the women it’s closer to 2.6 per cent.

In 2019, Kenyan legend Eliud Kipchoge broke the two-hour marathon barrier, albeit under highly controlled non-race circumstances. The following day, compatriot Brigid Kosgei smashed the women’s marathon record, which had been held by Paula Radcliffe since 2003. Both athletes were wearing the shoes. Calls for the shoes to be banned for their potentially unfair performance advantages echoed around the industry, but few would argue against sports technology being allowed to develop with the aim of improving performance.

At the time of writing, most of the major footwear brands have brought out their own version of the super shoe and Nike is no longer dominating the medal tables. Even some trail running shoes now come with an integrated carbon plate. Love them or hate them, there’s no doubt the recent innovation in shoe design has changed running, but how do they work?

There’s still research to be done on both the potential performance benefits and injury risks involved in wearing super shoes. It’s thought their performance enhancement is generated by enhancing athletes’ running economy, i.e. reducing the energetic cost of running at a given speed, as an integrated carbon plate acts like a springboard, deforming and then springing back to propel the foot forwards. Instead of the main flex point being at the ball of the foot, it shifts backwards – like rolling the wheel of a diving board backwards in order to increase its bounce – therefore increasing the lever-arm through which force is applied. Super shoes are also extremely lightweight, and use a soft, bouncy foam which returns more energy to the runner than traditional foam, and may reduce fatiguing impact forces through the lower limbs.

As with any similarly dramatic innovation, it’s likely the performance advantages of super shoes aren’t completely risk-free for all runners. There is some concern that moving the flex point backwards could be putting more stress on parts of the foot that are less able to flex and absorb impact, including the tightly packed joints around the navicular bone. If you’re trying out super shoes for the first time, build up wear time gradually to allow your body to adapt to the altered stresses. If you experience unusual pain or recurrent injuries when you’re wearing the shoes, it may be that they’re not right for you.