Spring is right around the corner in some parts of the country, and the change of seasons gets many folks thinking about reviving or revving up their running program. This often coincides with shopping for a new pair of running shoes. The title of this week’s article has the potential to be an immense topic, but I’m going to a provide just a bit of information that I think you may find useful.
The human foot is an amazing piece of machinery. Its architecture and function are a fantastic example of brilliant human design. With 28 bones, an intricate network of ligaments, multiple layers of muscle, and a plethora of nerves, blood vessels, tendons, joints, and other tissues, the foot is a true work of art.
What makes the foot so unique is that not only does it form the foundation upon which we stand, it is our critical interface with the ground. The foot enables us to locomote (walk and run) through its role as a force transference device. With every stride, the foot transitions from a flexible platform that adapts to the support surface, to a rigid lever that allows us to push powerfully off the ground.
Let’s visit briefly about stride mechanics. Each lower extremity goes through a swing phase and a stance phase in every gait cycle. The swing phase occurs when the limb is in the air and the stance phase encompasses the time the foot is on the ground. Depending upon the speed of locomotion, there are some variations in how the foot functions. Walking and all-out sprinting utilize different patterns from each other, and each of these differ from the jogging and running mechanics we’ll emphasize here.
The foot makes initial contact with the ground, often called footstrike, and then proceeds to midstance. Ideally, the initial contact should, by design, occur on the lateral midfoot or forefoot (depending upon individual anatomy and speed of running). From initial contact to midstance, the foot progresses to a conformation stage as the heel and medial longitudinal arch roll inward and downward, the forefoot splays as the transverse metatarsal arch slightly flattens, and the toes spread outward and forward. This sequence is called pronation and, while its degree varies from person to person, it’s a natural and desired movement to accomodate to the ground. Just after midstance, pronation maxes out and then the arches begin to elevate and re-stiffen as the foot supinates to achieve heel-off and eventually toe-off. Prior to push-off, as the toes are bending (extending…especially the 1st toe), tension increases in the plantar fascia and it functions as a windlass mechanism to help the foot maintain biomechanical rigidity. All of these components occur with every stride and without our ever having to think about it at all.
When the foot is functioning properly, the strike occurs on the midfoot or forefoot, under the hip of the forward leg, and with a flexed knee. Forces are distributed appropriately through the kinetic chain of each leg, and efficient locomotion is accomplished. In most cases, running barefoot on a natural surface such as a grass field or a sandy beach will automatically string together all the things we just discussed. However, many of us don’t always have those surfaces available, and consequently barefoot running (in appropriately small doses) isn’t utilized as a mode of locomotion or as a corrective training tool. Another issue is that most modern humans have weak, atrophied feet from a lifetime of shoe use, and additionally they may have less-than-ideal gait patterns or injury. Safely restoring optimal foot function and gait, and then intelligently progressing training volume and intensity, are the obvious keys in these circumstances. And ultimately, for most runners, utilizing shoes that mimic the barefoot condition (to some degree) may be very appropriate.
Before we can get to some basic shoe recommendations, we need to take a quick look at some of the arguments and obstacles which exist around barefoot running and minimalist shoes. Instead of exhausting each point, I’m going to bullet them out and just provide food for thought.
- Overpronation: Excessive amounts of pronation in a runner’s feet are often an indication of an individual who has a moderately high degree of joint and connective tissue laxity throughout the body, as well as a potential combination of stiffness and weakness problems in their lower extremity. Some barefoot proponents will argue that this is due to the constrained foot condition of modern shoes, and simply freeing the foot will fix the problem. This isn’t always the case. Severe overpronators can in many cases strengthen their feet and legs, and improve running form, but sometimes this isn’t enough and they don’t do too well with barefoot running and minimal shoes. Expert assistance and case-by-case management is very important here.
- High Body Weight: Notice I didn’t use the term “overweight.” Any large person, regardless of body composition, has the potential for increased ground reaction forces travelling up through the body every time the foot hits the ground. If muscular stability and shock absorption are not optimal, this runner can experience acceleration of pronatory forces as well as impact loading. Ideally, this condition would be best managed by very progressive training, and not via the use of overbuilt shoewear.
- Stability and Motion Control Shoes: These shoes are designed and marketed around the premise that their features can limit pronation in runners who appear to do so excessively. A number of studies indicate that the foot continues to pronate inside the shoe to nearly the same degree as the unshod condition. Occasionally these shoes create what I call “sleepy foot syndrome.” This is when the foot basically shuts off in function due to its proprioceptive and neuromuscular efficiency being blocked, and it just slaps down like a dead hunk of flesh and bone (not an artistic and active machine). However, shoe selection and proper fit can factor in here and some folks report feeling “better” when wearing such shoes. I’m still not a huge proponent of these shoes for a number of reasons. First, they sometimes allow a person to run more miles than they actually should due to altered mechanical forces. Second, force and motion are constants, and they have to go somewhere. This means if the shoe is altering foot function — even if it feels “good” — unnatural stresses are accumulating at the ankle, knee, hip, and back. A double-edged sword for sure.
- Maximally Cushioned Shoes: Six-inch-thick midsoles (OK…I’m exaggerating) are all the rage these days. The studies are somewhat conflicting on their efficacy. “It depends” is a valid answer to the question of “should I consider these?” Research strongly supports that the body is naturally equipped to absorb shock, particularly through pronation and knee flexion with the appropriate lengthening contractions of the quadriceps muscles. Having a huge wad of foam underfoot can subtly “numb” our natural reactions to ground contact and even cause instability problems due to elevating the sole of the foot off the ground. I never win popularity contests for suggesting this, but keep cushioning minimal, or moderate at most.
- Orthotics: The elephant in the room has been discovered! An orthotic is a device, essentially a replacement insole (but orthotic sounds more official and sometimes insurance will pay for it — don’t get me started). The true objective of any orthotic should be to increase total contact of the foot to the shoe (and thus the foot-to-ground interface), possibly control the rate and magnitude of pronation (not eliminate it) and maybe aid in comfort or shock attenuation to a small degree. An orthotic is not supposed to “lock” the foot into an arbitrary neutral position. We know from the preceding discussion that foot function needs to be dynamic to be optimal. All that stated, I’m not going down the “always or never” rabbit hole. In very limited circumstances, the temporary use of an orthotic can help a runner who is recovering from injury and returning to training appropriately…but its use should be very temporary. Proper barefoot and minimalist shoe training can restore that natural foot function better than the orthotic anyway, and without risks.
- Mileage: This relates to all the other bullet points. Runners don’t want to run less. And when a person like me (whether you see me as a geek or a guru) says “Hey, let’s get you running less for a while as we teach you how to run right,” most runners just take a pass, keep on pounding the pavement with bad form, crappy shoes, and unnecessary pain. But temporarily reducing mileage and relaxing on the metabolics of training, while emphasizing the mechanics of proper movement, will create a more pain-free, efficient and faster runner every time. And that becomes a runner who can then absorb higher mileage and harder workouts more effectively if that is the goal. Few people choose this route because they run for many reasons and are reluctant to even temporarily give up a single stride. Oh well.
So what should you look for in your next running shoe? I will provide a number of potential considerations.
- Last: This is the shape of the shoe and it is the template around which shoe manufacturers build each model. There are often specific lasts for each gender, as men and women typically differ slightly in foot volume and structure. However, the most important thing to seek, and for which many manufacturers deserve much credit these days, is a foot-shaped last. Turn the shoe upside down, and at first glance it should look like your footprint when you step out of the shower. The human foot is naturally wider in the toes than in the heel and a shoe that closely matches your foot’s profile will be more comfortable and allow for proper mechanics.
- Traction: Generally speaking, you should try to match the outsole of your shoe to the terrain upon which you plan on running most frequently. Shoes designed for trail use usually have full carbon rubber outsoles with aggressive lugs for both grip and protection. Those intended for running on roads will often have partially exposed midsoles, blown rubber (for its lighter weight) and carbon rubber inserts at high wear points. In dry conditions you can usually get away with less pronounced traction features. For training on tracks, select a smooth profile outsole and avoid trail shoes which will feel wonky. On grass, just ditch the shoes whenever possible.
- Cushioning: The shoe industry has mostly consolidated to use ethylene vinyl acetate (EVA) foam and seems to be going away from other additives and gimmicks. The less cushioning any shoe has, the greater the “feel” it offers for the foot to the support surface. I actually like to recommend that runners look at cushioning more as relatively thin protective layer in the shoe, more so than a marshmallow of squishiness. You need very little cushioning to run on a track or dirt path. Slightly more is indicated for roads and rocky trails. Never run on concrete. Just don’t do it (it’s an excessively hard unnatural surface that guarantees injury sooner or later). If concrete is your only option, go for a walk instead.
- Heel-to-Forefoot Differential: This is also called “drop” and is another area in which shoe makers have been improving. The old school shoes had a 10-15mm drop in height from the heel to forefoot, and this actually increased heel striking, impact forces, and achilles tendon issues. Newer shoes tend to be offered in “zero drop” configurations which are level from heel to toe, or in moderate differentials of 4-6mm. Most runners can adjust to the zero drop shoes over time if they accommodate gradually (again…that mileage reduction issue) but many prefer the moderate drop shoes for longer runs.
- Neutral vs. Stability: In most cases, the stability in your foot is blended with its natural mobility as part of ideal function. That stated, a neutral shoe is one that does not have any significant anti-pronation or motion-limiting features built into it. In most circumstances this is probably the best choice, especially when combined with the other features we are discussing. The message here is that we want to work on building intrinsic stability in the foot as opposed to relying on external devices.
- Stiffness vs. Flexibility: While most running shoes do not have rigid shanks like many boots, there is some variance in materials and construction methods with respect to mobility. You’ll see this in several areas. The point where the shoe flexes underneath the metatarsophalangeal (MTP) joints is called the toe break and some shoes use fiberboard lasting to limit this feature. Others use a stitching method called slip lasting for maximum mobility, as well as flex grooves cut into the midsole and outsole. Also, the torsional rigidity of a shoe, which you see when you twist it lengthwise, can vary. Obviously, letting more of the natural foot motion shine through is the goal, but different bodies, speeds, and running surfaces can affect your preference.
- Toe Box Volume: Not only do we want the toe box of the shoe to be wide enough to allow for toe expansion and forefoot splay, we also want it to be high enough so as not to press or rub uncomfortably on the toes. This is another area of improvement in shoe design, and in fitting recommendations. Make sure you have a thumbnail’s distance in front of your big toe and the ability to slightly spread and wiggle your toes in the shoe when laced properly.
- Upper Materials and Laces: Mesh is increasingly making up more of the upper on most running shoes today. This may come at a slight sacrifice of durability for enhanced breathability. Manufacturers are also drifting away from rigid heel counters in many models. This results in a lighter shoe that is more comfortable and conforming to the foot. Laces can be flat or round, and stretchy or not. I don’t prefer the cable lacing systems as I find they apply excessive pressure on the dorsum of the foot. Some shoes feature lacing configurations that are slightly off-center as well.This can be beneficial for those with very high insteps.The goal with uppers and laces is to find the fit which feels like a glove but not an overly tight one.
- Overall Weight: Lighter is generally better, as it allows the foot to feel more free at the same time it reduces oxygen consumption (according to much research). Some trail running shoes will need to be slightly heavier for their protective qualities. Less is more, even if they will wear out faster, in most cases.
This was not an exhaustive diatribe, but hopefully you received some information that you can put to use, or at least some points to consider. In summary, most runners can benefit from progressing toward the least amount of shoe they can tolerate…and natural function, freedom, and performance will be enhanced. The secret is experimentation and open-mindedness. Try on lots of brands and models before you commit to the one that feels best for you. And progress very gradually as you restore mechanical efficiency in your feet and gait. Happy running!