Impact absorption of tennis shoe-surface combinations

The aim of this study was to investigate, for typical shoes and surfaces used in tennis, the relative role of the shoe and surface in providing cushioning during running. Five test surfaces ranging from concrete to artificial turf were selected, together with two shoe models. Impact absorbing ability was assessed mechanically using drop test procedures and biomechanically using peak magnitude and rate of loading of impact force and peak in-shoe pressure data at the lateral heel. Differences in biomechanical variables between shoe-surface combinations were identified using a two-way ANOVA (p < 0.05). Mechanical test results were found to rank the surfaces in the same order regardless of the shoe model, suggesting that the surface is influential in providing cushioning. However, for all mechanical and biomechanical (p < 0.05) variables representing impact absorbing ability, it was found that the difference between shoes was markedly greater than the differences between surfaces. The peak heel pressure data were found to rank the surfaces in the same order as the mechanical tests, while impact force data were not as sensitive to the changes in surface. Correlations between mechanical and biomechanical impact absorption highlighted the importance of testing the shoe-surface combination in mechanical tests, rather than the surface alone. In conclusion, mechanical testing of the shoe-surface combination was found to provide a strong predictor of the impact absorbing ability during running if pressure data were used. In addition, for typical shoe-surface combinations in tennis, the shoe was found to have more potential than the surface to influence impact loading during running. Finally, in-shoe pressure data were found to be more sensitive than force plate data to changes in material cushioning.     

A mathematical model for power output in rowing on an ergometer

A mathematical model relating power output of rower to stroke rate on an ergometer (the Concept II Indoor Rower TM, Model C) is studied. The model is used to analyse the ergometer performance of a particular rower. It is determined that he can be more efficient (i.e. decrease power output while maintaining fixed velocity) by decreasing stroke rate, but at the expense of increasing force during the drive. It is also shown that he can be more efficient by increasing the drag factor (using higher vent setting) without increasing force. Dependence of power output on rowing style (the shape of the force curve) is also examined. It is shown that variation of force during the drive has little effect on efficiency, but efficiency is reduced by asymmetry of the force curve that favours the legs.     

The Value of Education: A Reply to Andrew Reid

Andrew Reid's essay on the value of education in this journal distinguished the intrinsic features of education from what education is for, the latter being ultimately located in the promotion of personal well-being. At a meta-ethical level, this response accepts Reid's claim about ultimate location, but challenges his view that prudential goods are desire-independent, arguing for a desire-dependent conception based on supra-individual, but not always universal-human, preferences. It also questions his claim that the source of educational value lies in the intrinsic features of education, rejecting the suggestion that epistemological rather ethical considerations should be the starting-point.     

人之悟感发展与教育的生本化改革

悟感是一种前意识现象,其主要功能在于提供产生感悟的基础和激活思想。悟感在人的精神生活中起着普遍的基础性作用,具有可求同性、能动性、对于符号世界的蕴涵性以及使认识回归本体的还原性。儿童的悟感与生俱来,又在他们的自主活动中发展,因而儿童是最重要的教育资源。教育要取得成效,就要高度尊重和全面依靠学生,即实施生本教育。