Measurement of studded shoe–surface interaction metrics during in situ performance analysis

Interaction between studded footwear and performance surfaces plays an important role in sport. Discretising this interaction into quantifiable measurements can help optimise design of outsoles and identify parameters for performance testing in situ. Here, we describe the development and validity of an image-based three-dimensional (3D) measurement system to investigate shoe–surface interactions during locomotion performance in situ by eight skilled footballers. By calculating individual stud positions, results revealed that the 3D kinematic data could be distilled to a number of shoe–surface interaction metrics such as orientation, velocity, translation distance and location of the centre of rotation. Findings show how the measurement system and simple analysis methods can be used to provide informative shoe–surface interaction metrics from in situ performance capture for the footwear communit

Influence of outsole design on centre of rotation during turning movements

A bespoke 3D measurement system was used to investigate the influence of the outsole configuration on the centre of rotation during a movement used by football players to change direction. Five outsole configurations were selected for analysis ranging from rounded studs to bladed designs. High-speed video information and force-plate data were collected and analysed to obtain the shoe kinematic and kinetic results. The centre of rotation was calculated during shoe-surface contact using the location of the stud positions on the outsole. Results indicated that significant differences occurred between outsoledesigns for the kinetic data, but all shoes impacted the ground at a similar orientation. The resulting centre of rotation varied between designs, but on average was located towards the toe of the shoe. This differs from the centre of rotation often used in traction testing and as a result, may influence the veracity of current assessment techniques

Tracking of foot movement during sprinting in studded footwear

Mechanical tests and finite element simulations are often used to assess the traction between a studded outsole and the surface. Appropriate boundary conditions are required in these experiments in order to replicate realistic loading scenarios. The result of using different boundary conditions has been well researched (Nigg 1990, Kuhlman et al. 2009. Kirk et al. (2007) used a high-speed video camera to investigate kinematic boundary conditions in 2D during the acceleration phase in sprinting. The study was limited as the angle of the shoe could only be calculated in one plane. Analysis of high-speed footage in 3D is possible using a two camera system, as per Choppin et al. (2007) who determined the orientation of a tennis racquet during play in three planes

The use of photoelasticity to identify surface shear stresses during running

Shear stresses arising between the surface and a studded outsole during running were identified but the use of photoelasticity. A bespoke experiment set-up was designed to capture the dynamic maximum shear stress fringes occurring when a studded outsole came into contact with the photoelastic surface. Image processing methods were used to clearly identify the fringes. Examples of analysis techniques were outlined; focusing on the use of the greyscale intensity of the photoelastic fringes to calculate the subsequent shear stresses