Stiffness Effects in Rocker-Soled Shoes: Biomechanical Implications

Abstract

Rocker-soled shoes provide a way to reduce the possible concentration of stress, as well as change movement patterns, during gait. This study attempts to examine how plantar force and spatio-temporal variables are affected by two rocker designs, one with softer and one with denser sole materials, by comparing them with the barefoot condition and with flat-soled shoes. Eleven subjects’ gait parameters during walking and jogging were recorded. Our results showed that compared with barefoot walking, plantar forces were higher for flat shoes while lower for both types of rocker shoes, the softer-material rocker being the lowest. The plantar force of flat shoes is greater than the vertical ground reaction force, while that of both rocker shoes is much less, 13.87–30.55% body weight. However, as locomotion speed increased to jogging, for all shoe types, except at the second peak plantar force of the denser sole material rocker shoes, plantar forces were greater than for bare feet. More interestingly, because the transmission of force was faster while jogging, greater plantar force was seen in the rocker-soled shoes with softer material than with denser material; results for higher-speed shock absorption in rocker-soled shoes with softer material were thus not as good. In general, the rolling phenomena along the bottom surface of the rocker shoes, as well as an increase in the duration of simultaneous curve rolling and ankle rotation, could contribute to the reduction of plantar force for both rocker designs. The possible mechanism is the conversion of vertical kinetic energy into rotational kinetic energy. To conclude, since plantar force is related to foot-ground interface and deceleration methods, rocker-design shoes could achieve desired plantar force reduction through certain rolling phenomena, shoe-sole stiffness levels, and locomotion speeds.

Importance of Footwear Outsole Rigidity in Improving Spatiotemporal Parameters in Patients with Diabetes and Previous Forefoot Ulcerations

“…Lin et al have demonstrated that harder rocker soles decrease the duration of plantar forces during the totality of the stance phase in non-diabetics [14], which was associated with plantar pressure reduction. However, they did not investigate the timing during the step cycle subphases, which were most reduced with the use of harder outsoles.…”

“…Previous studies have shown that a rigid rocker sole decreases plantar pressure in the forefoot [13] and changes spatiotemporal parameters in comparison with a flattened sole. Moreover, it has been shown that rigid materials result in kinematic parameter changes when compared to semirigid materials in healthy patients without an altered gait [14]. Patients with DPN have shown longer midstance phases in the gait cycle [15,16].…”

Biomechanical effects of rocker shoes on plantar aponeurosis strain in patients with plantar fasciitis and healthy controls

“…Considering that a proximal apex position of 56.1 ± 2.6% did not lead to a significant reduction in PA strain, more aggressive rocker profiles (<56%) should be considered in clinical practice and especially in severe cases of plantar fasciitis. However, it is important to note that lowering the internal plantarflexion moment during gait with a more proximal apex position might lead to higher joint loads at the knee and hip, affect spatio-temporal parameters such as gait speed and step length and the smaller support surface might impair balance [21,37–40]. In addition to orthotic treatment, patients with plantar fasciitis might benefit from gait training aiming to reduce peak Achilles tendon forces during push-off.…”

“…In addition, minimizing bending of the shoe with a stiff insole prevents excessive dorsiflexion of the toes during pre-swing [17]. However, until now it remains to be established whether these biomechanical effects associated with a proximal apex position and stiff insole lead to smaller PA strain and hence mechanical load during gait in patients and healthy controls [21].…”

Pedographic assessment of the impact of off-the-shelf orthopedic shoes on the load distribution under the feet in patients with a high risk of developing diabetic foot syndrome

“…Показано, что перекат позволяет значительно снизить нагрузку на передний отдел и пальцы за счет уменьшения нагрузки при фазах опоры и заднем толчке [5]. Кроме того, предполагается, что часть нагрузки, которая действует вертикально, при наличии жесткого переката трансформируется во вращение относительно линии переката, что и позволяет снизить нагрузку [6]. Есть данные и о стимуляции проприорецепции при длительном применении так называемой «перекатной» обуви [7,8].…”