The researchers said adolescent runners quickly adapt their foot strike when barefoot running, but a significant proportion of older, experienced runners keep the same heel-first foot strike as when using shoes.
The study, from the University of Kansas Department of Orthopedics and Sports Medicine, is being presented at the 2015 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS) this week.
The researchers found that a significant proportion of experienced older runners use a heel-first foot strike when running barefoot and suggest this may lead to more frequent injuries.
Lead author and orthopedic surgeon Scott Mullen says:
"Previous studies have demonstrated that an adolescent runner's foot strike is heavily influenced by their running shoe. Young runners quickly adapt to a forefoot strike pattern when running barefoot, whereas a heel strike is normally associated with wearing large-heeled training shoes."
For their study, the team enrolled 24 runners aged 30 and over who had at least 10 years of running experience.
They measured the heel and forefoot thickness of the running shoes (conventional and minimalist) as the participants ran at different speeds. For women, the speeds were 6, 7 and 8 miles per hour, and for men, the speeds were 7, 8 and 9 miles per hour.
Older runners 'should be cautious' when swapping to a more minimalist running shoe
The researchers invited a blinded examiner skilled in the use of motion capture systems and running mechanics to analyze the foot strikes of the runners.
The results showed that the heel-to-toe thickness of the running shoe (conventional and barefoot minimalist shoe) did not correlate with a change in heel strike, and neither did differences in speed.
While the runners showed a significant drop in use of heel-first strike when running barefoot compared with conventional shoes at all speeds, 40% of the men and 20% of the women persisted with the same strike patterns at all speeds with and without conventional shoes.
The researchers say that while a forefoot strike may have some advantages in barefoot running, recent reports show a high injury rate as athletes adopt a barefoot or minimalist running shoe condition.
Dr. Mullen says their study suggests perhaps older runners may find it harder to adapt quickly to running barefoot, and notes:
"The inability to adapt the foot strike to the change in shoe type may put these runners at increased risk of injury. Older runners should be cautious when transitioning to a more minimalist type of shoe."
Many protagonists of the barefoot running movement maintain there is only one way to run barefoot - strike with the forefoot first because this is how habitual barefoot people run.
But it seems this idea may have been prompted by one study done in one running population. Now, an increasing amount of research shows that habitually barefoot people do not necessarily employ one pattern of foot strike.
For instance, in January 2013, Medical News Today learned of a study from George Washington University that found variations in foot strike patterns among predominantly barefoot runners in Kenya.
The researchers behind that study said their findings contradict the idea that in order to avoid the high impact forces typically associated with heel-first foot strikes, habitually barefoot people run by landing on their forefoot first.
It appears that as more studies are done, the "correct way" to land when running barefoot is not as clear-cut as we might assume.