离心收缩下大腿前后肌群肌力距屈伸比的实验探究

本文利用瑞士CON-TREX反馈式生物力学测试系统,对受试者在3个角速度(60°/s、120°/s、180°/s)进行膝关节的离心收缩测试,研究不同角速度条件下膝关节屈肌和伸肌的变化特征以及主动腿、非主动腿屈伸比的变化特征。研究表明:在等速离心运动时,主动腿与非主动腿大腿前后肌群肌力距屈伸比存在差异;主动腿伸肌峰力矩的值大于非主动腿的伸肌峰力矩,而主动腿的屈肌峰力矩小于非主动腿的峰力矩的值。

上交叉综合征身体成分与肩关节肌力特征研究——以女大学生为例

研究了上交叉综合征女大学生身体成分和肩关节等速肌力特征,为诊断上交叉综合征的病理特征提供理论依据。通过仪器对 12 名上交叉综合征(UCS)大学生和 12 名正常人在 60°/S 的角速度下,两侧肩关节向心收缩仰卧位前屈、后伸、内收和外展肌肉力量进行测试。结果发现,UCS 组体重、BMI、基础代谢、骨骼肌含量、左右上肢肌肉含量均明显低于正常组;组间 UCS 女大学生和正常人在 60°/S 角速度下相比,两侧肩关节伸,内收,外展肌群峰力距均有显著性差异,其双肩伸和右肩外展具有非常显著性差异,两侧肩关节伸和外展下平均功率均具有显著差异,其右肩伸和外展具有非常显著性,UCS 组屈伸比值和内收外展比值均大于正常组。研究得出结论:UCS 女大学生身体素质水平较低,上肢肩关节外展,伸肌群肌肉力量薄弱,这可能是 UCS 患病率原因之一。

Numerical assessment of spacing–burden ratio to effective utilization of explosive energy

The spacing–burden(S/B) ratio plays significant role on rock fragmentation and proper utilization of explosive energy to minimize the undesirable damage.Low S/B ratio generates fine fragments due to pressure rings coalescence of two blast holes,whereas boulder generations were observed above optimum S/B ratio.Both conditions are not acceptable because of wastage of explosive energy.Therefore,to resolve this issue,a numerical model study was conducted to optimize the S/B ratio and to envisage its effect on rock fragmentation based on utilization of explosive energy.Finite element simulation tool was used to see the extent of two blast hole influence area variation with varying S/B ratio.The better results were obtained at S/B ratio of 1:2 with optimum utilization of peak explosive energy.The performance was observed based on peak kinetic energy,peak pressure,radial and hoop stresses on centre of the two blast holes,where pressure rings coalescence.