Proponents of barefoot running say that humans evolved for barefoot running and that we have been running this way for millions of years. The human foot is designed to run this way and barefoot runners have lower rates of injuries than those who wear running shoes and may even run faster.
Opponents of barefoot running on the other hand say precisely the opposite. They say that running shoes support the feet reducing injuries and cushion the body against impact thus preserving the joints. This is particularly important, they say, on hard modern running surfaces such as concrete which humans have not evolved to run on.
But is there any firm evidence one way or the other? Well, a new summary of all the available evidence just published in the journal Exercise and Sport Sciences Reviews sheds some new light on the issue.
First of all it is important to point out that the author of this review admits that there are no conclusive studies proving the issue one way or the other. However it is interesting to note that recorded rates of running injuries have not declined in the last 30 years with the advent of the modern cushioned running shoe. As the review states -
"Everyone including athletes ran barefoot or in minimal shoes until the 1970s when the modern running shoe with a cushioned heel, arch support, and stiffened sole was invented..... The lack of any apparent decline in running-related injuries over the last 30 years, despite much attention, considerable research, and sophisticated shoe designs, suggests that current approaches are not working effectively. The major hypothesis I propose is that the human body was adapted to running in a barefoot style whose kinematic characteristics generate less forceful impact peaks, which uses more proprioception, and which may strengthen the feet. I hypothesize that these factors may help runners avoid injury, regardless of whether they are wearing shoes."
So what are these characteristics of a barefoot running style which may protect against injury and which could be applied by any runner barefoot or not? The review identifies 3 main points:
When running on hard surfaces the majority of shod runners hit the ground with the heel of their foot first or rear foot strike (RFS) but barefoot runners are more likely to hit with the ball of the foot, front foot strike (FFS) or mid foot strike (MFS).
Experiments show that a RFS generates significant impact peaks of force which travel up the leg and can be measured in the tibia. A FFS or MFS however generates little or no impact peak since the flexion of the foot at the ankle dampens the force generated like a shock absorber.
Barefoot runners tend to adopt a shorter stride length than shod runners. This seems to be because a shorter stride helps to avoid RFS. Also maintaining a FFS with a long stride requires the tip of the foot to be pointing down more. This puts more strain on the Achilles tendon and muscles of the lower leg as they dampen the impact force generated.
FFS running places greater eccentric loads on the ankle plantarflexor muscles than RFS running. It is a logical conclusion then that muscle hypertrophy in these muscles is greater in barefoot runners than shod runners. Greater muscle strength improves foot stability and reduces injuries.
In summary, a FFS or MFS which reduce impact forces up the leg, a shorter stride which help maintains FFS and reduces Achilles ankle strain and the resultant increased muscularity of the ankle plantarflexor muscles may all contribute to a safer running style and can be applied regardless of whether we run with shoes or not.
In the words of the author - "what matters more for preventing injury is running form rather than footwear."
Lieberman, Daniel E. What We Can Learn About Running From Barefoot Running: An Evolutionary Medical Perspective. Exerc Sport Sci Rev. 2012 Apr;40(2):63-72. Click here to read study