Neuromechanical adaptations to slippery sport shoes

Friction Blisters of the Feet: A New Paradigm to Explain Causation

Friction blisters on the feet commonly occur when individuals engage in active pursuits such as running, hiking, and military training. The high prevalence of blisters in active individuals underscores the fact that the pathomechanics of this condition are not fully understood. The traditional blister causation paradigm revolves around heat, moisture, and friction. In reality, foot friction blisters are caused by repetitive shear deformation. The 3 fundamental elements of blister-inducing shear deformation are (1) motion of bone, (2) high friction force, and (3) repetition of the resulting shear events. Rubbing at the skin surface is not a mechanism for friction blister formation. To that end, prevention of the friction blister continues to be an elusive quest for both the patient and the treating clinician. In this article, we aimed to highlight the limitations of the long-held blister-causation paradigm and offer a new explanation.

Futsal playing surface characteristics significantly affect perceived traction and change of direction performance among experienced futsal players

We aimed to clarify the effect of different futsal playing surface structural properties on the resultant change of direction (COD) performance, perceived traction and frictional properties. Twenty experienced male university soccer players performed a COD slalom-course test and perceived traction evaluation on three different types of playing surfaces (area-elastic: AE, point-elastic no.1: PE1 and point-elastic no.2: PE2). Frictional properties of these surfaces were mechanically evaluated against a futsal shoe, using a hydraulic moving force platform, and expressed as available friction coefficient (AFC). In the COD performance test, the participants performed significantly better on the point-elastic surfaces (PE1 and PE2) when compared to the area-elastic surface (AE) (p < 0.05). Also, the PE2 surface was found to have the highest perceived traction (p < 0.001). The findings suggest that the relatively higher (4%) AFC explains the improvement in performance and traction perception on the PE2 surface. In this study, we successfully demonstrated that the structural difference (AE or PE) of futsal playing surface has a significant impact on the COD performance of experienced futsal players and their perceived level of traction (PE2) and the frictional properties.

Grip socks improve slalom course performance and reduce in-shoe foot displacement of the forefoot in male and female sports players

This study assessed whether grip socks reduce in-shoe foot motion and improve change of direction performance in team sports players and compared the effects between males and females. A sledge and pulley system confirmed the static coefficient of friction was increased in the grip socks (1.17) compared to the regular socks (0.60). Performance during a slalom course was faster in the grip socks compared to regular socks (p = .001). Yet, there was no difference in the utilised coefficient of friction between the shoe-floor interface during a side-cut and turn change of direction manoeuvre. Three-dimensional motion capture revealed the grip socks reduced in-shoe foot displacement during the braking phase, with greater effect during the sharper turn manoeuvre. The magnitude of natural foot spreading within the shoe was greater in the calcaneus region than the metatarsals which suggests in-shoe sliding may only occur at the forefoot. Males tended to have increased in-shoe displacement, which is associated with larger foot spreading due to their increased mass. Findings provide guidance for product developers to enhance the support inside the shoe at the forefoot, and change of direction performance.

Footwear insoles with higher frictional properties enhance performance by reducing in-shoe sliding during rapid changes of direction

A novel 3D motion capture analysis assessed the efficacy of insoles in maintaining the foot position on the midsole platform inside the shoe during rapid change of direction manoeuvres used in team sports. An insole (TI) with increased static (35%) and dynamic (49%) coefficient of friction compared to a regular insole (SI) was tested. Change of direction performance was faster (p < .001) and perceived to be faster (p < .001) in TI compared to SI. Participants utilised greater coefficient of friction in TI compared to SI during a complete turn, but not during a 20 degree side-cut. In-shoe foot sliding reduced across the forefoot and midfoot during the braking phase of the turn and in the rearfoot during the side-cut in TI. Greater in-shoe foot sliding occurred in the turn than the side-cut across all foot regions. Results provide guidance for athletic footwear design to help limit in-shoe foot sliding and improve change of direction performance.