Barefoot running should theoretically reduce runner injuries, but experimental evidence suggests the injury rate of barefoot runners is not any higher or lower than shod runners.
Barefoot running was once confined to a rare breed of runners, but after Christopher MacDougall’s book Born to Run was published, barefoot running has become more mainstream. The book is a good read and comes out forcibly in favor of barefoot running. Initial findings by a Harvard research group supported barefoot running, but the last several years of research provide no clear consensus on whether or not barefoot running is “better” at preventing injuries than running with modern running shoes. A review published recently in Sports Medicine nicely summarizes the sports medicine community's consensus, or lack thereof, on barefoot running (Barefoot Running: Does it Prevent Injuries? 2013. Murphy, et al.).
Early support for barefoot running came from an evolutionary perspective. Born to Run found inspiration in the Tarahumara tribe. MacDougall wrote about the Tarahumara's rubber sandals, which allowed them to run with a natural form that predated modern running shoes. The Tarahumaras’ ability to beat elite American long-distance runners in some of the toughest ultramarathons in the country demonstrated the efficiency of their running style. The Harvard research group, meanwhile, consisted primarily of evolutionary biologists who approached modern running shoes as a hindrance to human’s natural running form.
The Harvard research group, formally known as the Skeletal Biology Lab, supported barefoot running using a theoretical foundation. Most runners adopt a rear-foot or mid-foot strike with running shoes, but a forefoot strike when running barefoot (see the figure below). This shift in running form is a result of the extra cushion in the heel of modern running shoes, which affords the heel to land with high impact without sustaining direct damage. In addition, the length of the stride is extended with a rear foot strike. Analyzing the kinematics of different foot strike patterns reveals that a rear foot strike causes a greater impact force when the foot strikes the ground. Worse yet, a rear foot strike causes two different impacts. One impact occurs when the heel strikes the ground and a second impact occurs when the mid and forefoot strike the ground. Thus, rotational energy in the foot is lost in that second impact rather than being used for a forward push-off. From this research, the Skeletal Biology Lab suggested that barefoot running may be a way to successfully mitigate leg injury. However, they acknowledged that further experimental studies were needed to substantiate this conclusion.
Indeed, further research studies would analyze barefoot running as it became evermore popular with runners. The research was both positive and negative. A study published earlier this year and reported in Runner’s World found that runners in Vibram FiveFingers (a minimalist shoe that mimics barefoot running, see figure (a) above) were more prone to injury despite running less peak mileage than their shoe-wearing counterparts. These injuries primarily consisted of stress fractures. The increase in injuries observed in barefoot runners is likely explained by the increase in force on the metatarsals in the toes. It should be noted that most study participants were newly introduced to barefoot running; it is possible that a long term study would be more beneficial in explaining the differences in injury rates.
The extra cushioning in running shoes causes increased leg stiffness. However, there is no evidence that suggests that lower leg fractures occur at a higher rate in runners with shoes. Another common injury in runners is plantar fasciitis, which is caused by excessive pressure on the heel (the plantar fascia). Although the first impact in rear-foot running is the heel, there is no evidence to suggest that barefoot running is an effective remedy for plantar fasciitis.
In terms of treating and preventing injury, is one method of running superior? The answer appears to be no. However, the switch itself to barefoot running appears to cause injury. Thus, it appears that any switch to barefoot running should be gradual in nature: longer than two weeks. If injured, the best approach may be to change your running form, rather than lose your shoes. Perhaps, the most sound advice is to choose the running style you feel most comfortable with.