# Correlations Between the Mechanical Properties of Running Shoes by forrests

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```									Correlations Between the Mechanical Properties of Running Shoes/ Artificial Tracks and the Sensory Evaluations by Distance Runners
Sadayuki Ujihashi, Mitsuhiro Iwasaki, Katsumasa Tanaka and Norio Inou Graduate School of Information Science and Engineering, Tokyo Institute of Technology 2-12-1, Oh-okayama, Meguro-ku, Tokyo 152-8552 Japan

Introduction
In case of running on artificial tracks, the optimum cushioning characteristics of running shoes would depend on the hardness of track materials. In this paper it is investigated by conducting of mechanical tests and runners' sensory evaluations on shoes with artificial tracks how the optimum sole cushioning of running shoes is affected by the hardness of artificial tracks and how the mechanical properties are correlated with the sensory evaluations by distance runners.

Mechnical tests on shoe soles and artificial tracks
Drop weight impact tests (1)(Drop weight:18 kg, Impact velocity:1m/s) are carried out on 4type of running shoes which have 4 different materials and different constructions. Figure 1 shows the force and deformation relationship obtained by eliminating time from force and deformation responses, which are measured T4 by the drop weight tests onto 4 different shoe soles and 4 different artificial tracks. 2 T3 Typical parameters extracted from Figure 1 are listed in Tables 1 and 2 in order to T2 prescribe the obvious characteristics. Energy absorption rates do not have big deviation and the values of shoe soles are almost 1 T1 S4 double of artificial tracks. Average Young's S3 S2 moduli are roughly proportional to the rubber hardness and the values of artificial S1 tracks are much higher than those of shoe soles. Then, the cushionings of shoe soles 0 will have stronger effects on runners' 0 5 10 Deformation[mm] sensory evaluations as running gears than those of artificial tracks. Figure 1: Force and deformation relationship on shoes and artificial tracks Table 1: Shoe soles tested and their mechanical properties Rubber Maximum Maximum Energy Average Shoe Sole Hardness Force Deformation Absorption Young's [kN] [mm] [%] Modulus [Asker(C) Hardness] [kN/m] S1 49.7 0.700 13.6 55.5 51.6 S2 54.8 0.748 12.0 55.2 63.0 S3 61.7 0.762 10.8 56.1 71.7 S4 66.4 0.859 10.0 55.8 87.4 Impact Force[kN]

Table 2: Artificial tracks tested and their mechanical properties Energy Artificial Maximum Force Maximum Absorption Track [kN] Deformation [%] [mm] T1 1.22 4.78 29.3 T2 1.74 5.00 19.8 T3 1.85 4.57 26.4 T4 2.26 3.94 24.4 Whole evaluations on running by wearing 4 different shoes on 4 different artificial tracks, that is, 4 different stadiums, are carried out by 4 distance runners. Data acquisition of sensory evaluations and after processings are conducted based on the Scheffe's method (2). Figure 2 shows the results of the sensory evaluations by Runner A on whole evaluation, cushioning and stability against the mechanical hardness of shoe soles, that is, average Young's modulus, regarding 4 different artificial tracks. Favourite hardness of Runner A is about 70kN/m in case of running on an undeformable surface, that is, extremely hard surface(As). However, on deformable surfaces, the favour of Runner A likely tends to change depending the material and the construction of artificial tracks. The results on Runner B, C and D are similar to Runner A.

Average Young's Modulus [kN/m] 257 348 408 582

Sensory evaluations and their correlations with mechanical properties
Whole Evaluation

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T1 T2 T3 T4 As

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T1 T2 T3 T4 As

Evaluation on Cushioning

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Conclusions
Runners' sensory evaluations are sensitive on shoe sole hardness, that is, average Young's modulus. The runners' favourite shoe-sole hardness locates around 70kN/m of average Young's modulus in case of running on an undeformable surface. However, in case of deformable surfaces, sensory evaluations for the shoes with softer or harder sole hardness become higher by depending on the materials and the constructions of artificial tracks. References

Evaluation on Stability

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(1)Ujihashi S., et. al., Method of measurement and evaluation Average Young's Modulus [kN/m] for the mechanical characteristics of running shoes, the Engineering of Sport, ed., Haake, S., Blackwell Figure 2: Effects of artificial track on sensory Science(1998), pp.171-179. (2)Scheffe, H., An analysis of variance for paired evaluation versus average Young's modulus of comparisons, Jour. Am. Stat. Ass., Vol.47(1952), pp.381-400.

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