Man has gone barefoot for millennia. All of a sudden, we decided to wear heeled shoes and sneakers for every daily activity. If you think that this has no implications on your body, then it is better that you read this!
Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with small heels and little cushioning, if not present at all like the shoe in Figure 1.
Modern running shoes now have a significant amount of cushioning and stabilization incorporated, marketed for comfort, injury protection, and correcting movement patterns. This brings us to an important question: in all this comfort and protection, why do we often get injured running?
Shoes do make a difference in our body and the consequences are much bigger than what the general public thinks. First of all, putting soles under our feet affects how we land on the ground and thus how the force is distributed. As Figure 2 highlights, it has been proved that habitually barefoot runners have a fore-foot strike before bringing down the heel. In contrast, habitually shod runners have a rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe [1,2,3].
The different landing also brings different impact forces: as Figure 3 shows, barefoot runners have a fore-foot strike that implies no impact transients, that are instead present in shod running (notice the first peak on the right graph). Also, notice the steeper slope of the curve for shod running, meaning a higher shock to absorb for the body.
Furthermore, barefoot running is associated with a shorter stride length and higher cadence than in typical shod running with a rear-foot strikers pattern [4,5]. This reduced stride length results in lower loads experienced by the body and protect the runner from impact-related injuries [6,7,8].
There is also another important aspect that is affected with a sole between the foot and the ground: as Figure 4 suggests, our feet are full of nerve terminations that are sensory input to the neuromuscular system. When loading becomes unexpectedly high, the plantar surface of the foot provides sensory input that elicits an avoidance response, indicated by rapid hip flexion and resulting in a quick unloading .
So far so good, but we are still missing the most important thing: the bigger picture! In a holistic approach, the feet cannot be seen in isolation from the rest of the body: if whatever happens to the head affects the feet (in a descending way), the opposite is also true (in an ascending way, from the feet to the head).
First of all, an increased joint torque is observed at the ankle wearing shoes . Then, it has been widely proved that heeled-shoes induce an increase in compressive forces at the knee [11,12,13]. So, it comes with no surprises that:
- The knee is the most common site of injuries for shod runners .
- Although in barefoot conditions there is no gender differences in joint knee torque , osteoarthritis of the knee is twice as common in women as in men. Indeed, women wear shoes with higher heels that causes increased joint torque at the knee [16,17].
Going up, wearing shoes affects the hips as well [11,17]. And, if you think that it ends here, you are wrong: spinal posture changes as well. While in the short term it looks like heeled shoes decreases the lordotic curve [18,19], in the long term, they cause a forward rotation of the pelvis, with the body forced to compensate with an increased lordotic curve [18,20,21,22], with then all the consequences that spread to the head.
So, being barefoot is the way nature intended for us. Its increased sensory input results in greater static and dynamic stability [23,24,25], with reduced impact on certain zones of the body, preventing many modern injuries.
Also foot shape is completely changed with modern shoes: as Figure 6 highlights, considering the effect of bone remodeling, frequent shoes wearing causes the feet to develop differently from what nature intended for us. Barefoot walkers have wider feet and more equally distributed peak pressures. Habitually shod subjects have relatively short and slender feet, with non-homogeneous pressure distribution . So, it is not surprising that many foot disorders are typical only of shod populations [27,28], such as flatfoot and fallen arches, bunions and hallux valgus, hammer toe, blisters, corns and calluses.
Nature gave us the best possible tool for standing, walking and running: the foot! We evolved going barefoot for millennia, so why changing now? The impact on our body integrity is huge, so go barefoot as much as possible and when buying a new pair of shoes remember: the less, the better!
 Hasegawa, Hiroshi, Takeshi Yamauchi, and William J. Kraemer. “Foot strike patterns of runners at the 15-km point during an elite-level half marathon.” Journal of Strength and Conditioning Research 21.3 (2007): 888.
 Kerrigan, D. Casey, et al. “Moderate-heeled shoes and knee joint torques relevant to the development and progression of knee osteoarthritis.” Archives of physical medicine and rehabilitation 86.5 (2005): 871-875.
 de Oliveira Pezzan, Patrícia Angélica, et al. “Postural assessment of lumbar lordosis and pelvic alignment angles in adolescent users and nonusers of high-heeled shoes.” Journal of Manipulative & Physiological Therapeutics 34.9 (2011): 614-621.
 Shinohara, Junji, and Phillip Gribble. “Five-toed socks decrease static postural control among healthy individuals as measured with time-to-boundary analysis.” State College, PA: American Society of Biomechanics (2009).
 Squadrone, R., and C. Gallozzi. “Effect of a five-toed minimal protection shoe on static and dynamic ankle position sense.” The Journal of sports medicine and physical fitness 51.3 (2011): 401-408.