The heel-to-toe differential is one of the most commonly discussed differences between running shoes. While the barefoot movement popularized the idea of zero-drop—a flat platform from heel to forefoot—most traditional running footwear touts around a 12-millimeter difference with an elevated heel. The most recent studies demonstrate that one approach isn't necessarily better than the other. While running barefoot or in zero-drop shoes has been shown to put less stress on the knee, it often increases the loading on the ankle, Achilles tendon and calf.
"I think the minimalist trend took off dramatically in 2012 when runners found that switching to a minimalist shoe made their knee pain disappear," says Alice Holland, director of Stride Strong Physical Therapy in Portland, Oregon. "This can simply be attributed to the fact that the impact load has shifted to another joint, thereby relieving the much-worked knee."
What all this amounts to is the fact that there's no one-size-fits-all prescription when it comes to running footwear. Whether you have two different models that you rotate or pairs designated for trail running, road runs and track workouts, the slight variations in heel-to-toe angle and midsole cushioning and support can offer your feet and legs some much needed variety. Since many running injuries are the result of repetitive stress put on the same muscles, joints, tendons, ligaments and bones, variation in everything from footwear to pace to terrain is encouraged in most cases.
"Though the general neuromotor patterns are similar, the timing of the firing of certain muscles may differ based on speed, terrain, footwear, fatigue state, strength, and flexibility, to name a few of the variables to consider," Hamilton says.
It's important to keep in mind that while experienced runners may benefit from the practice of training in multiple pairs of shoes, beginners should tread carefully.
"Veteran runners have had a longer amount of time to strengthen pretibial muscles and foot intrinsics during their run training, so they are at less risk for injury when switching between different shoe types than their lesser trained counterparts," Holland says.
Even for the most experienced runners, Hamilton emphasizes that runners should add in new types of running footwear with caution.
"Making a sudden switch from your usual shoes to something novel, you run the risk of placing excessive loads on a tissue that isn't quite ready for it and this may result in injury," says Hamilton.
As with most elements of training, use prudence in introducing anything new and always listen to your body's feedback.Sign up for your next race.