Q: Foot strike: What's good, bad and when should I worry?
"Salt is good for you."
"Salt is bad for you."
"Sitting at work is bad for you."
"Standing at work is bad for you."
As with studies on salt intake or sitting at work, you have to take the research on foot strike with a "grain of salt." (Sorry, I couldn't help myself there.) To oversimplify things, foot strike is how the foot lands while running.
There is no right or wrong in terms of foot strike (heel, midfoot or forefoot strike). It is more about what works for you in terms of foot mechanics. Studies are very conflicted out there whether or not one type of striking potentially results in more injuries than another.
A study of Harvard cross-country runners (Daoud - 2012) found that runners who consistently heel strike had almost twice the occurrence of stress fractures than those who forefoot strike. Yet, other studies haven't made a connection between heel striking and higher injury rates.
One thing that appears to be consistent with the research I have reviewed: There appears to be higher incidence of injury to heel strikers who are running barefoot or with minimalist shoes. One reason for this is perhaps because people run too much too soon in such shoes.
To answer your question: There is no good or bad, but you might want to be more mindful if you are heel striking in barefoot / minimalist shoes. Also, you might want to be mindful of how your body is positioned at "midstance," but I'll come back to that later.
Getting back to barefoot running: With the "minimalist" or "barefoot" running movement, the philosophy has also arisen that landing on the midfoot or forefoot is more natural and is better for performance.
However, in a study of runners in the 2004 Sapporro International Half Marathon in Japan, it was found that 75% of the elite runners landed on their heels. This runs counter to an often-held belief that elite runners are forefoot strikers.
Foot strike is just one component of running form. Some runners will demonstrate higher impact with a forefoot strike, while others will demonstrate lower impact with a heel strike. So, there are always exceptions to every rule. Other form factors are stride length, cadence, impact duration, body type, position at midstance, etc.
To simplify things: if you're a heel striker, you might benefit from more cushioning in the heel for shock absorption. If you're a midfoot or forefoot striker, you might be able to explore a more minimalist / streamlined type of shoe; however, if that is something you are considering, you would want to ease into such a shoe because your body has adapted to the more traditional running shoes. To start, I'd suggest using such shoes on lower mileage days.
Another thing you'll want to be mindful of is other factors of shoe design.
Speaking of shoe design, one goal should be to design shoes to reduce injury risk, but that means designing a shoe that not only takes into account "impact" but also a shoe that manages the strain or force the body is put under at "midstance."
What is Midstance?
Midstance is the point of gait (walking or running) when the "centre of mass" (or the concentration of your weight) of the body is above the foot. Studies have focused so much on "strike" yet not enough has been researched on the position of our bodies at midstance.
At the same time, let's not overthink our stride or the way we strike the ground either. There is a natural component to running. Again, it is about what is beneficial or what works for individual runners. We are all different.
Stay tuned and pass the salt.