By Dr. Mercola
Although humans have been running for thousands of years, the modern running shoe was not invented until the mid-1970s. The range of available footwear today is significant, from built-up heels and fully cushioned shoes, to minimalist coverings that only protect your feet from the road.
In 2012 nearly 30 million Americans ran 50 times, an increase of nearly 3 percent from 2011.1 The sport continues to grow in popularity for fitness, competition and simply as an enjoyable pastime. However, the repetitive nature of running, with the force of impact on your knees and hips, increases your risk for injury.
While some would like to blame their shoes for the injuries, others point to the repetition of movement, and still others link lack of flexibility, strength or poor biomechanics to their rate of injury.
The reality is that running is a complex movement in a complex organism and most of those factors play some part in the development of injuries.
Shoe manufacturers claim their shoes can correct your biomechanics, provide cushioning and reduce impact to your foot, knees, hips and lower back. Some shoes have as much as a 0.6 inch (16 mm) rise in the heel over the toe, which encourages a heel strike over a midfoot or forefoot strike.
Now research has demonstrated that all this cushioning and changes to your natural biomechanics may not be what your body needs to run without injury.
Running on Less Cushion Offers More Protection
Your loading rate is the speed at which you apply force to your body. One way to reduce injury is to reduce your loading rate. This is the theory behind using shoes that are well-cushioned.
The hope is that by landing on a highly cushioned shoe you’ll reduce the force or impact on your joints, tendons and ligaments, and thus reduce your loading rate.
However, recently researchers have discovered the opposite is likely true. Runners who wear shoes with little to no cushioning often run on the balls of their feet and experience lower loading rates.
In this study of 29 runners, researchers compared normal running shoes against minimal trainers. Lead author Dr. Hannah Rice from the University of Exeter, said:2
“So many people use running as a means of reducing the risk of chronic diseases, but about three-quarters of runners typically get injured in a year. Footwear is easily modifiable, but many runners are misguided when it comes to buying new trainers.
This research shows that running in minimal shoes and landing on the balls of your feet reduces loading rates and may therefore reduce the risk of injury.”
Despite popularity of the sport and decades of training and research, the prevalence of injury has not fallen among runners. These researchers theorize that the rear foot strike, heel striking the ground first in cushioned shoes with built up heels, causes an abrupt vertical impact force on the lower extremities.
Minimalist shoes have little to no cushioning, a heel-to-toe drop of less than 0.16 inches (4 mm) and a stack height of less than or equal to 0.64 inches (16 mm). Running or shoe stores should be able to help you find this type of running shoe.
Shoes Likely Not the Entire Problem
Prior to completion of the research, the total force the legs absorbed, or loading rate, appeared to be similar whether the runners were wearing minimalist shoes or cushioned trainers. Rice commented:3
“This seems to suggest that, for runners in traditional, cushioned running shoes, foot strike pattern may not matter for injury risk. However, we suspected that the same may not be true of runners who regularly use minimal shoes, which don’t have the cushioning provided by traditional running shoes.
Our research tells us that becoming accustomed to running with a forefoot strike in shoes that lack cushioning promotes a landing with the lowest loading rates, and this may be beneficial in reducing the risk of injury.”
Despite new gels, air pockets and foams, more than 50 percent of runners continue to be injured each year. Brian Metzler, editor-in-chief of the running magazine Competitor believes that blaming injury on the type of running shoe you use ignores other contributors to the high injury rate in the sport.4
He points out two factors that may impact injury rate, including people who begin running from a non-running background and others who suffer from training errors.
Research in 2010 by Daniel E. Lieberman, Ph.D., a Harvard professor who studies the biomechanics of endurance running, partly fueled the barefoot running movement.5 He commented on shoe choices, saying:6
“How one runs probably is more important than what is on one’s feet, but what is on one’s feet may affect how one runs.”
The Heel of It All
You may have been born to run, but you may not run efficiently. Just as it takes years to perfect playing basketball or tennis, running may not be as intuitive as you may have been led to believe. In fact, for many people poor biomechanics during walking is the primary source of low back and hip pain.7
When those same poor biomechanics are taking place at a faster pace, it only increases the loading rate and potential for greater injury to the knees, hips and lower back.
There are skills that make a runner more physically efficient and may reduce the number of injuries experienced, but very few spend the time to acquire them before increasing the distances they run.
The intention behind technological advancements in the shoe industry is to artificially change your stride to reduce your injury rate. Manufacturers achieve this through stiffer shoes, built-up heels and other structural changes to the shoe that force your feet and legs into a different position.
However, artificially changing the position of your foot, and the way in which it strikes the ground, may actually increase your risk of injury. One of the ways a running shoe encourages you to strike the ground with your heel first is to increase the heel-to-toe drop to greater than 0.16 inches.
When you’re comfortable running with your heel striking first, you’re at greater risk of over striding, i.e., lengthening your stride so your knee extends past your center mass. You can’t strike the ground first with your forefoot or midfoot as your stride lengthens past center.
Does Foot Strike Influence Your Performance?
Several studies have evaluated athletes’ foot strike in both competitive and recreational races. The results are not as uniform as you might think. In a study comparing barefoot and minimally shod racers in the 2011 New York City Barefoot run, the results demonstrated forefoot strike patterns were more common in barefoot runners and not the minimally shod racers.8
In a study published in Nature,9 comparing barefoot endurance runners against those who customarily wore shoes, the researchers found the habitual barefoot runners landed more frequently on their forefoot and the shod runners used mostly a heel-strike pattern, “facilitated by the elevated and cushioned heel of the modern running shoe.”
A study of runners in an ultramarathon race of 100 miles (161 kilometers) found most of the runners wore shoes and used a heel strike.10 In this study the researchers also drew blood during the race and found those using a forefoot strike had higher levels of creatinine kinase, an enzyme released in the blood when muscle breaks down. These researchers concluded that the heel strike reduced muscle damage.
In a meta-analysis of research published between 1980 and 2011, researchers found there was not enough data to definitively support barefoot running, but there was data to use a forefoot strike pattern to reduce forces, ground contact time and step length.11
Although researchers have focused their energy on foot strike, the real question may be stride length and position of the foot in relationship to the body when it hits the ground. It’s almost impossible to have a forefoot strike when your knee is past the center of gravity and your stride length has increased. This position is called over striding, which you may unconsciously do to increase speed as it requires less leg turnover but increases the amount of ground covered.
Over Striding Reduces Efficiency and Increases Loading Rate
If, as Lieberman suggests, how you run is more important than the shoes you wear, but the shoes you wear may affect how you run, then it’s important to look at more than how the foot hits the ground. The biomechanics of over striding affect loading rate, as Sage Canaday, collegiate Division I and professional runner, demonstrates in this video.
There are three primary ways you can change the loading rate your body experiences as you run. These are contact pattern with the ground, postural alignment and lack of flexibility.12 In a previous study led by Lieberman, the team concluded that even on hard surfaces, a forefoot strike generated smaller forces on the body than a rear foot strike wearing shoes.13
The difference in forces may result from a difference in the plantar flexion position of the foot as the ball of the foot hits the ground first, with more compliance at the ankle during impact that effectively absorbs more force. However, once again, it must be pointed out that it is difficult to strike the ground with your forefoot if your foot is past the center of gravity.
In evaluating the runner’s strides using a force plate to measure impact it was demonstrated that it may not be where on the ground your foot strikes, but rather where in relationship to your body’s center mass it lands.14 Most runners who adopt a forefoot strike will naturally find their foot lands near center mass and those who adopt a heel strike will have a greater potential for overreaching or over striding as the leg moves farther in front of the body’s center mass.
Landing closer to your center mass may effectively reduce your loading rate and thus potentially reduce your risk of injury. Running in minimalist shoes and increasing your cadence, or leg turnover to increase speed instead of increasing stride length, will help accomplish this end goal. Unless you’re accelerating, your foot will normally contact the ground slightly forward of center mass during a steady pace.
This is only one of the three ways you may significantly reduce your loading rate. When you combine all three strategies of contact pattern with the ground, postural alignment and flexibility, you may find running more enjoyable and be less injury prone. However, these changes require time, effort and patience to incorporate into your routine.
Posture Matters in Walking and Running
USA Triathlon certified coach Stephanie Coburn shows you from top to bottom the posture and movements that reduce injury and improve your performance. As posture affects your body function during walking, it also has a significant effect on your potential for injury when going at a faster pace. You can utilize your posture to help alter your center mass in relationship to your foot placement.
Many walk in a slightly forward position, shoulders hunched and weight placed up on your toes. When you attempt to stand up straighter you may have a tendency to arch your lower back. An arch in the lower back changes the lumbar position of your spine and moves your center mass back, which in turn causes your foot to land further in front, effectively increasing your loading rate.15
It’s important to learn to walk, and then run, with your lumbar spine in neutral position so your feet fall closer to your center of mass. Do this by tucking your gluteal muscles, engaging your abdominal muscles and strengthening your pelvic floor muscles, all of which help stabilize your core and keep your spine neutral.
The last factor in loading rate is how heavily you hit the ground. In other words, running more softly.16 The combination of striking the ground near to center mass, running with greater postural control and striking the ground “softly” will help minimize loading rate and reduce potential injuries.
However, it is important to note that making these biomechanical changes increases mechanical stress on tissue you may not have used frequently. When done suddenly and consistently, it can also lead to injury.
Canadian injury prevention expert and sports physiotherapist Blaise Dubois, suggests a one-minute rule. Start using your new running form for one minute of your overall run. Then, each subsequent run, use your new form for one minute longer than your last. This slow adaptation allows your muscles and ligaments to strengthen slowly and your body to become more accustomed, making the new running form second nature within weeks.