Running is distinguished from walking in that at some point in the running cycle both feet are in the air at the same time. This “flight” phase of the running gait occurs no matter how fast or how slow we are moving. Landing on one foot from an unsupported position is part of what makes running physically demanding.
Running with a forefoot/midfoot strike is considered the natural way to run because this is the way people land when they run barefoot. This makes sense given that running is very similar to taking a small hop from one foot to the other. Every time your foot hits the ground a force of about 2.5 times your body weight is transmitted through your body. Landing on the forefoot allows the foot and ankle to act like springs to absorb the impact of hitting the ground.
We don’t land on our heels from a jump for a reason. It would hurt. Yet studies consistently show that somewhere between 75-90% of runners heel strike!1 What’s happening?
Generally speaking, there are three ways that your foot can hit the ground:
A heel strike is suitable for walking (in most situations) because our full weight is not loaded on the leg until the entire foot makes contact with the ground. As we walk forward with each step our body weight is gradually shifted from one leg to the other. The back foot provides support and doesn’t leave the ground until the forefoot of the front leg touches down. By the time our entire weight is on one leg the whole foot is down and providing support.
For running, we also want to have the forefoot on the ground as weight is being loaded on the leg. Because a runner is landing from an unsupported position (the other foot has already left the ground), weight is loaded on the leg much sooner following contact. The forefoot needs to be on the ground early in the loading phase to take advantage of the shock absorption provided by the anatomy of the foot and the dynamic control coming from the muscles of the lower leg.
A pronounced heel strike doesn’t allow the foot and the lower leg muscles to assist with absorbing forces during the initial loading of the leg. Instead, those forces are transferred higher up, to the knees and hips.2 The difference in the way the body handles forces of the different foot strike patterns has given rise to the idea that heel striking is less efficient and increases the risk of running injuries.
A performance comparison between different foot strikes really only becomes a question for long distance running. For covering distances up to 10 km a fore/midfoot strike is the clear winner. All sprinters and most elite middle-distance runners land on their forefoot.
At distances over 10 km is when we start to see the percentage of heel striking runners go way up, even at the elite level.3 This shows that it is indeed possible to perform well over long distances as a rear foot striker. There is still a good percentage of midfoot strikers among the fastest runners however, and the number of heel strikers goes up the farther back in the pack you go.4
Also, the elite distance racers that do heel strike have what’s called a proprioceptive heel strike. The heel makes a glancing contact with the ground, but loading doesn’t happen until the entire foot has touched down. This is different from the overstriding, heel striking pattern often seen in recreational runners, where the foot lands in front of the body with the toes pointed up at a 45 degree angle.
Regardless of what part of the foot they land on, good and efficient runners don’t overstride. Overstriding imparts a braking force on the leg, decreasing efficiency and increasing joint torque at the knees and hips.
Overstriding can happen with either footstrike pattern, but is much more common among heel strikers. You can test this for yourself by running in place without shoes on. When the foot lands underneath the body’s center of mass you automatically use a forefoot/midfoot strike, just as you would if you were hopping on one leg.
The improved shock absorption forefoot striking provides is theorized to reduce the potential for injury in runners, but very few studies have looked at the difference in injury rates between the different patterns. A study of Division I cross country runners published in 2012 showed heel strikers had twice the rate of injuries of mid/forefoot strikers.5
Another recent study found switching from heel striking to forefoot landing was successful in treating chronic exertional compartment syndrome–an injury seen almost exclusively in runners.6 The researchers involved with that study cited the higher ground reaction forces, ground contact time, and step length seen with heel striking as the main factors behind the difference in injury rates.
As mentioned earlier, a heel strike shifts stress from the ankle and calf and places it on the knees and hips. This has raised suspicion that forefoot striking may reduce the number of knee and hip injures, only to increase injures at the foot and ankle.7 I think the opposite is true. The foot and calf muscles seem better suited to withstand, and adapt, to the forces of running than the knee, and may actually become stronger and more resistant to injury the more they get used.
Additionally, landing on the fore/midfoot offers more versatility than a heel strike, giving us the ability to react to the ground on contact and vary the pressure under the foot accordingly. This provides variety to the way stresses are applied to the body which adds another degree of protection against injury.
The high percentage of rear foot strikers reported in studies is about the same as what I’ve observed working with recreational athletes. Not only with runners, but with athletes in sports where you wouldn’t expect to see heel striking like basketball.
The biggest factor influencing foot strike patterns is footwear. Cushioned shoes alter the way the foot interacts with the ground and promote a heel striking running pattern. With a big wedge of foam under the foot striking the ground on the heel becomes an option because it no longer causes immediate discomfort. Shoe cushioning also reduces sensory feedback, and slamming the heel into the ground may be one way our body’s try to compensate for this.
Another likely factor is that many recreational runners learn to run at a slow pace, often focusing on distance rather than speed. This can lead to the development of a running style that resembles a sped up version walking. Walking and running are distinct forms of locomotion. Adding a “flight” phase to a walking gait results in the running overstride pattern most often associated with injuries.
Landing from an unsupported position is the main difference between running and walking. A forefoot strike is how the body naturally handles the impact of landing, but cushioned shoes make it possible for runners to land on their heels, leading to a disproportionate number of heel strikers among recreational runners. Some evidence exists that heel striking increases a runner’s risk of injury, and this may be partly due to an increase in ground reaction forces, ground contact time, and step length when compared to forefoot striking.