Since the latter half of the 20th century, there has been much scientific and medical interest in the benefits and harm involved in barefoot running. The 1970s, in particular, saw a resurgent interest in jogging in western countries and modern running shoes were developed and marketed. Since then, running shoes have often been blamed for the increased incidence of running injuries and many[quantify] runners have switched to barefoot running for relief from chronic injuries. However, the American Podiatric Medical Association cautions would-be barefoot runners, stating that there is still not enough research on the immediate and long term benefits of the practice, and that individuals should consult a podiatrist with a strong background in sports medicine to make an informed decision on all aspects of their running and training programs. Additionally, individuals with diabetes or other conditions which affect sensation within the feet are at greater risk of injury and are advised not to run barefoot.
The structure of the human foot and lower leg is very efficient at absorbing the shock of landing and turning the energy of the fall into forward motion, through the springing action of the foot’s natural arch. Scientists studying runners’ foot motions have observed striking differences between habitually shod runners and barefoot runners. The foot of habitually shod runners typically lands with an initial heel strike, while the foot of a barefoot runner lands with a more springy step on the middle, or on the ball of the foot. In addition, the strike is shorter in duration and the step rate is higher. When looking at the muscle activity (electromyography), studies have shown a higher pre-activation of the plantar flexor muscles when running barefoot. Indeed, since muscles’ role is to prepare the locomotor system for the contact with the ground, muscle activity before the strike depends on the expected impact. Forefoot strike, shorter step duration, higher rate and higher muscle pre-activation are techniques to reduce stress of repetitive high chocks. This avoids a very painful and heavy impact, equivalent to two to three times the body weight. “People who don’t wear shoes when they run have an astonishingly different strike,” said Daniel E. Lieberman, professor of human evolutionary biology at Harvard University and co-author of a paper appearing in the journal Nature. “By landing on the middle or front of the foot, barefoot runners have almost no impact collision, much less than most shod runners generate when they heel-strike.”
The longitudinal (medial) arch of the foot also may undergo physiological changes upon habitually training barefoot. The longitudinal arch has been observed to decrease in length by an average of 4.7 mm, suggesting activation of foot musculature when barefoot that is usually inactive when shod. These muscles allow the foot to dampen impact and may remove stress from the plantar fascia. In addition to muscle changes, barefoot running also reduces energy use – oxygen consumption was found to be approximately 4% higher in shod versus barefoot runners. Better running economy observed when running barefoot compared to running with shoes can be explained by a better use of the muscle elasticity. In fact, reduction of contact time and higher pre-stretch level can enhance the stretch shortening cycle behavior of the plantar flexor muscles and thus possibly allow a better storage and restitution of elastic energy compared to shod running.
Running in shoes also appears to increase the risk of ankle sprains, plantar fascitis, as well as other chronic injuries of the lower limb. However, running shoes also provide several advantages, including protection of the runner from puncture wounds, bruising, thermal injuries from extreme weather conditions, and overuse injuries. Transitioning to a barefoot running style also takes time to develop, due to the use of different muscles involved. Doctors in the United States have reported an increase in such injuries as pulled calf muscles, Achilles tendinitis, and metatarsal stress fractures, which they attribute to barefoot runners attempting to transition too fast.
The running shoe itself has also been examined as a possible cause of many injuries associated with shod running. One 1991 study found that wearers of expensive running shoes that are promoted as having special features, such as added cushioning or pronation correction, were injured significantly more frequently than runners wearing inexpensive shoes. It has also been found that running in conventional running shoes increases stress on the knee joints up to 38%, although it is still unclear if this leads to a higher rate of heel injuries or not. One study suggests that there is no evidence that cushioning or pronation control in shoes reduces injury rates or reduces performance. It was also found that the belief that your shoes have increased cushioning had no effect on increasing or decreasing ground reaction forces during walking. Modern running shoes can also increase joint torque at the hip, knee, and ankle, and the authors of the study even suggest that running in high heels might be better than modern running shoes. Improperly fit shoes may also result in injuries such as a subungual hematoma – a collection of blood underneath the toenail. This may also be known as “Runner’s toe” or “Tennis toe”.