No abstract

Long-distance running is known to induce joint overloading and elevate cytokine levels, which are the hallmarks for a variety of running-related injuries. To address this, footwear systems incorporate cushioning midsoles to mitigate injurious mechanical loading. The aim of this study was to evaluate the effect of athlete body mass on the cushioning capacity of technical footwear. An artificial heel was prototyped to fit the impact pattern of a heel-strike runner and used to measure shock attenuation by an automated drop test. Impact mass and velocity were modulated to simulate runners of various body mass and speeds. The investigation provided refined insight on running-induced impact transmission to the human body. The examined midsole system was optimized around anthropometric data corresponding to an average (normal) body mass. The results suggest that although modern footwear is capable of attenuating the shock waves occurring during foot strike, improper shoe selection could expose an athlete to high levels of peak stress that could provoke an abnormal cartilage response. The selection of a weight-specific cushioning system could provide optimum protection and could thus prolong the duration of physical exercise beneficial to maintaining a simulated immune system.

Abstract. Several studies sought to determine impact attenuation of shoes through the evaluation of force platform or accelerometer measurements. Recent literature however points out methodological flaws of "subject inclusive" experimentation, as this approach is unable to evaluate neither the foot/ground interface nor the absorbed energy allocation. This study provides a holistic evaluation of the biomechanical response of athletic footwear to individual runner characteristics through advanced mechanical testing.

The use of additive manufacturing for the fabrication of sacrificial cladding is becoming increasingly popular as it facilitates the production of complex yet space-saving protective structures. Despite this, the effect of several structural parameters on their capacity to mitigate high-velocity impacts remains elusive. Toward this end, the shock-mitigating capacity of various short fiber-reinforced polymer samples was evaluated regarding impact velocity and mass (raging from 1 to 8.3 m/s and 5.5 to 7.5 Kg, respectively). Among the assessed parameters were peak force (measured to vary by up to 46.6%), max. and mean deceleration values (with max. differences documented at 29.5% and 48.2%, respectively) and cushion factor. As expected, the progressive crushing modes differed significantly across the spectrum of the tested samples. Structural failure involved the growth of inter- and intra-laminar cracks, fiber-matrix de-bonding and de-lamination, which was dependent on equivalent pore volume fraction and compressive strength. Increasing infill density led in most cases to higher peak forces during impact, as did the deposition of more solid peripheral layers, with the latter producing a superior deceleration plateau. Evaluated collectively, the results indicate that an infill density of 37% with 4 solid external (protective) layers exhibited the superior impact response among the tested samples.

Abstract. A number of low-cycle fatigue tests were conducted on reinforced-concrete steel bars of various diameters to study their behaviour under axial loading according to EN 10080 and EN 1421-3. Scanning electron microscopy was used to study the specimen fracture surfaces. The problems faced during testing are presented and a specimen preparation method is described that will aid researchers on fatigue testing to obtain accurate test results and save on material and time.