Foot strike is basically how your foot impacts the ground with each step you take when running. Remember that running and walking are both ways of moving under human power, but running is just fast walking. With walking, one foot is always in contact with the ground. (This is why racewalkers look kind of weird, because they are walking really fast but they aren’t running; they’re walking.) With running, a person is at various times in the air, landing, pushing off into the air, and landing on the other foot. Thus, while walking isn’t non-impact, its impact forces are much less than those involved when running.
The argument against heel striking is that when you land on the heel, the entire force of impact starts with the heel and the travels straight up the leg to the knee; there’s nothing flexible in between to absorb the shock. A forefoot or midfoot strike, on the other hand, uses more of the foot to dissipate some of the shock before it goes up the lower leg to the knee.
That’s certainly true. You can test it on a treadmill and listen for how much softer your impact is if you land on the balls of your feet, where the arch of the foot will flex before your heel touches down lightly at the end of the foot-ground contact.
However, it turns out that forefoot striking may just shift the stress points away from the knees and hips to the ankles and feet. As Gretchen Reynolds of the NY Times‘ health/wellness blog explains,
In essence, the findings [of a 2013 study] show that you can’t escape the cumulative impact of running, however you stride, said Juha-Pekka Kulmala, a Ph.D. student, now at the University of Jyvaskyla, who led the study. Hit with your heels and you stress your knee, possibly leading to conditions such as patellofemoral stress syndrome. Strike near the ball of your foot and you’ll jolt your ankle and Achilles’ tendon, potentially increasing the risk of such injuries as Achilles’ tendinopathy, plantar fasciitis, and stress fractures of the foot.
There is, in other words, no one invariably right and painless way to run.
However, Mr. Kulmala said, the results also indicate that strategically altering how you land could be advisable for some runners. “People suffering from knee problems can benefit from forefoot striking,” Mr. Kulmala said. “Those who have Achilles’ tendon complaints can benefit from rearfoot striking.”
(emphasis added). This, it turns out, is definitely consistent with my own injury experience. I’ve been fortunate not to have had any major running-related injuries since I got off the couch in January 2011, but I have dealt at various times with a pulled calf (lost a week), metatarsalgia (lost a week or so), mild plantar fasciitis (lost a week), a sprained extensor digitorum brevis muscle (lost 10 days), and Achilles tendonitis (lost two weeks), but no knee or hip problems. And I run with a midfoot strike, which is, I guess, more like a forefoot strike than a heel strike.
(In fact, it’s because of the Achilles tendonitis that I know I run with a midfoot strike. When I finally felt okay enough to resume running — though in retrospect, probably still too early — that first run felt really weird at first because until my tendons warmed up, I was heel striking not by choice, and it was definitely not my usual way of running. It took about half a mile before I felt somewhat normal.)
I wanted to learn more about foot strike, so I got in touch with Dr. William Martindale, who’s one of the sports docs at Accelerated Sports Medicine. (They’re the guys who staff the medical tent at Uberthons and other selected events.)
Dr. Martindale concurred that footstrike is, at least based on current research, inconclusive in terms of being a clear cause of injury. More relevant than footstrike is form, particularly stride length:
The research shows that overstriding (which also causes significant breaking during the gait I might add), whether the runner is a forefoot, mid foot, or heel striker, will direct the forces more into the knee and lower leg leading to increased injuries than those persons who can bring their foot/lower leg more under their hips/center of mass, directing the forces up into the hip and body; in a sense using the entire body as the shock absorber. In other words, if runner A puts (X) amount of force into the lower leg due to overstride, and runner B puts the same amount of force into the same region due to overstride (both runners are about the same size), it isn’t going to matter if the foot strikes, the same energy gets dispersed into the same region; maybe runner A gets shin splits because he/she runs more on their heels, and runner B gets calf strains because he/she always runs forefoot…same problem: an overuse injury due to a break in their kinetic chain and not using their entire body as a shock absorber.
His personal view is that “how [runners] strike on the foot is not as important as where they strike with their foot during gait.”
One key to controlling stride length lies in cadence, or the number of steps per minute, with 180 being a generally suggested minimum number. (An easy way to tell if you’re around 180 steps/minute is to start counting “one thousand one” as you land on one foot, and see if you’re landing on the other foot when you finish; if so, that’s three steps in one second, or 180 per minute.)
A high cadence makes you take shorter strides (though of course, as you increase speed, the stride will lengthen). A shorter stride should lead to a softer impact, and likely leads to landing with your foot under your body instead of in front.
To recap, then, foot strike gets a lot of attention, but probably more than is deserved.