Stefan Schwanitz

Long-term Cushioning Properties of Running Shoes (P152)

In this report a test setup is presented that has been developed to generate a life cycle stress to the heel part of running shoes. The force-time-relationship has been derived from biomechanical investigations on ground reaction forces during running. By having investigated a range of 13 shoes it could be demonstrated that mechanical degradation leads to significant changes in the ability of sole materials to absorb energy. Furthermore an increased stiffness can be shown.

Relationship between plantar pressure and perceived comfort in military boots

Although comfort is an important feature in military boots, especially during long marches, there is a lack of information about the relationship between plantar pressure and perceived comfort of military boots in marching conditions. The influence of plantar pressure on perception of comfort has been shown for athletic and casual footwear (Chen et al. 1994, Jordan et al. 1997). The authors showed that peak pressures are coherent with perceived comfort in most plantar foot regions. They pointed out that insole characteristics are an important factor for the distribution and magnitudes of plantar pressure as well for the perceived shoe comfort. Therefore, it is necessary to understand the way boot comfort is perceived and how it can be increased to develop military boots. Furthermore, the risk of sustaining a stress fracture is increased in military recruit populations (Milgrom et al. 1985), but relationship between the bending stiffness of military boots, increased peak pressures and resulting metatarsal strain has only been partially assessed up to date (Arndt et al. 2003). Hence the aim of the study was to determine the relationship of perceived comfort and plantar pressures in military boots during realistic marching conditions. Furthermore, boots were also tested mechanically in order to clarify any relationship between boot’s bending stiffness and plantar pressure as well as between boot’s bending stiffness and perceived comfort.

The Effect of a Vibration Absorber on the Damping Properties of Alpine Skis

Coupled bending-torsion vibrations at the shovel are a severe problem when running an alpine ski at high velocities on hard or icy slopes. Thus, a major goal for ski manufacturers is to dampen vibrations through a proper multi-material design and/or additional absorbers. The aim of this study was to examine the effectiveness of a particular vibration absorber on a commercial slalom ski through a series of laboratory tests as well as a subjective field evaluation. Therefore, two identical pairs of ski were used and the absorber was deactivated on one pair. Laboratory tests revealed reductions of 5% to 49% of bending vibrations on skis with activated absorber. Subjective evaluation by 6 subjects suggested minor differences in the mean of the evaluated criteria turnablity, edge grip, steering behavior and stability towards a better performance of the skis with activated absorber. Subjects were able to identify the absorber mode with a success rate of 61.1%.

Material selection for climbing hardware using the example of a belay device

The aim of the research project was to design a novel climbing belay device. The present article describes the details of the therefor performed material selection. Literature research on the materials used in commercially available belay devices revealed a lack of definite information. Thus, a pilot x-ray fluorescence (XRF) test was performed on a small sample of common aluminium belay devices. It revealed the use of a variety of different alloy systems. The selection process continued by compiling a thorough list of constraints and objectives for this safety related piece of sports equipment. Different material options including non-aluminium-materials were discussed. The final material choice was a high strength aluminium alloy with a T6 thermal treatment. The device was designed and calculated by use of CAD and FEM software respectively, aiming to reduce weight. After manufacturing the strength, usability and friction properties of the device have been successfully tested.

The development of a soccer shoe outsole for artificial turf

The maximum pronation angle has no difference among the sample shoes but the difference of moment is obvious. Referring to the earlier study (Nigg 1999), LH and MS shoes of large pronation moments, are expected to have large pronation angles. By the above fact the pronation moment would be effective to assess the pronation. Focusing on the pronation moment, the trend of the moment and the moment arm are very similar to the cause of foot flat phase. It is suggested that the principal factor of intershoes differences is the moment arm. The moment arm is determined by the geometry of the center of pressure, the direction of GRF and the position of joint center. When foot is bent medially by the pronation moment, the joint center can be also moved medially. This is a catastrophic scenario of the over-pronation and then it is important to control the moment arm. The maximum moment arm length is observed at 16% of the stance phase. At that time, the position of the center of pressure is located about 26% of the length from the heel to the toe. In the past, only landing geometry has been thought to be important for controlling the pronation, and the trade-off between cushioning and motion control had come up for debate. The results of this research suggest that pronation would be modified by controlling the moment arm at the specific time from landing and the position of a little forward from the heel.