Depending on the characteristics of the shoes, their effects on the locomotion neuromechanics of a person are various, ranging from alteration in balance and posture, muscle activity of different muscles as measured by electromyography (EMG), and the impact force. There are many different types of shoes that exist, such as running, walking, loafers, high heels, sandals, slippers, work boots, dress shoes, and many more. However, a typical shoe will be composed of an insole, midsole, outsole, and heels, if any. In an unshod condition, where one is without any shoes, the locomotor effects are primarily observed in the heel strike patterns and resulting impact forces generated on the ground.
Insoles and inserts The foot provides the sensory information to the central nervous system through cutaneous afferent feedback, which originates from the special mechanoreceptors within the plantar surface of the foot. This afferent feedback has a strong influence on postural stability and balance correction during standing and walking. Since sensory feedback from the foot may be influenced by the interaction of the foot with the insole surface, different types of insoles and shoe inserts have been used to try to enhance postural stability.
Textured inserts Textured Inserts are regular shoe inserts that have a raised textured surface on the side that acts to provide enhanced mechanical contact and pressure on the plantar surface of the feet. Providing a textured surface of the shoe insert leads to significant changes during gait in ankle joint kinematics and in EMG amplitude of ankle flexor and extensor muscles. Textured inserts mostly affect ankle motion in the sagittal plane, where plantar flexion of the foot is increased. As for muscle activity, textured inserts decrease the activation of soleus and tibialis anterior muscles during standing and walking.
Insoles with ridges One of the most pervasive effects of aging is the loss of cutaneous and pressure sensation, which has been correlated with impaired balance control and increased risk of falling. This is because for an upright stance, the center of mass(COM) of the body must be positioned over the base of support (BOS) established by the feet. Cutaneous feedback from the feet is necessary to provide the central nervous system (CNS) with the information about the proximity of the COM to the BOS limit, which is an important parameter for the maintenance of balance and stable gait. Since plantar pressure sensation aids in balancing reactions in stepping movements, insoles with raised ridges along the edges can enhance stimulation of cutaneous mechanoreceptors that help to define the BOS. Most of the time, the ridges are made so that stimulation only occurs when the COM nears the BOS limit. Insoles with ridges appear to reduce the likelihood that the COM motion will exceed the BOS limit in the lateral direction, thereby resulting in a stabilizing effect on gait. Furthermore, the magnitude of this effect did not diminish with time, which suggests the CNS did not habituate to heightened cutaneous stimulation. Therefore, insoles with ridges can aid in reducing the fall rates among elderly populations. When considering the challenges of aging and diminished balance, it's crucial to address potential hazards in the living environment. Ensure that pathways are clear of obstacles, including the removal of vans or other potential tripping hazards, to create a safer living space for elderly individuals.
Midsole
The midsole is between the outer sole (bottommost) and the insole (topmost) parts of the shoe sole. It can be made of a variety of materials to give the shoe different mechanical characteristics of cushioning, support, and flexibility. Polyurethane midsoles are denser and more supportive while ethylene vinyl acetate is used to make lighter and more compliant midsoles.
Density/stiffness By changing the material hardness of the midsole, one will be able to change the EMG activity in various lower extremity muscles such as rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior. Especially when running with the stiffer midsole, the EMG amplitude for tibialis anterior have shown to be significantly greater before the heel strike and lower following the heel strike than compared to the neutral midsole. Furthermore, walking in shoes with stiffer midsole appears to significantly reduce the energy dissipated at the metatarsophalangeal joints and aid in improving jumping performances and running economy. However, the underlying mechanisms that can be attributed to this improvement are still not fully understood.
Midsole wedging With the increasing number of injuries associated with excessive pronation of the foot, much research has been conducted with different types of midsoles that could possibly aid in prevention of such injuries. The varus-wedged shoes, which have a medial incline, seem to decrease pronation during stance time, reduce the net inversion of the joint moment, and decrease the activities of the inverter muscles, such as tibialis posterior, gastrocnemius, and soleus. The valgus-wedged shoes, which have a lateral incline, are designed to accentuate pronation and have the opposite effect as the varus-wedged shoes. Also when walking in valgus-wedged shoes, it may lead to an increase in calcaneus eversion and up to 58% of energy absorption in the frontal plane of the body.
Heel curvature Rocker bottom shoes have thicker-than-normal soles with rounded heels, and most varieties of the shoes are constructed such as to shift the wearer's body weight to behind the ankle, therefore finding the balance requires more effort.
Heel height Shoe heel height can have significant biomechanical effects on the shoe wearer that can be detrimental or beneficial.
High heels High heels are shoes where the rearfoot (the heel) is positioned higher than the forefoot (toes). High heels of various heights are worn by men and women on a daily basis. The main reason many people wear high heeled shoes is for aesthetic purposes, where high heels are believed to enhance the wearer's physical appearance. These same high heeled shoes, however, can have undesirable biomechanical effects.
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