Downhill walking training with and without exercise-induced muscle damage similarly increase knee extensor strength

This study examined whether avoiding or experiencing exercise-induced muscle damage (EIMD) influences strength gain after downhill walking training. Healthy young males performed treadmill downhill walking (gradient: ?28%, velocity: 5 km · h^?1 and load: 10% of body mass) 1 session per week for four weeks using either a ramp-up protocol (n = 16), where exercise duration was gradually increased from 10 to 30, 50 and 70 min over four sessions, or a constant protocol (n = 14), where exercise duration was 40 min for all four sessions. Indirect markers of EIMD were measured throughout the training period. Maximal knee extension torque in eccentric (?1.05 rad·s^?1), isometric and concentric (1.05 rad·s^?1) conditions were measured at pre- and post-training. The ramp-up group showed no indications of EIMD throughout the training period (e.g., plasma creatine kinase (CK) activity: always <185 U · L^?1) while EIMD was evident after the first session in the constant group (CK: peak 485 U · L^?1). Both groups significantly increased maximal knee extension torque in all conditions with greater gains in eccentric (ramp-up: +19%, constant: +21%) than isometric (+16%, +15%) and concentric (+12%, +10%) strength without any significant group-difference. The current results suggest that EIMD can be avoided by the ramp-up protocol and is not a major determinant of training-induced strength gain.     

毛泽东文艺观的话语空间

作为毛泽东文艺思想的重要来源,毛泽东的文艺观对共和国的文学和文艺理论产生和正产生着巨大影响。文章从话语理论的维度审视毛泽东的文艺观,描述其独特的话语方式和对该话语生成语境作还原回溯,从话语格局、话语矛盾和话语蕴藉等三方面对毛泽东文艺观的话语空间作深层透视,展示了其文艺思想广阔的话语空间和丰富的话语蕴藉,有利于纠正人们对毛泽东的文艺思想作封闭的教条式理解的倾向,从而在另一新的平台上恢复毛泽东的文艺思想体系的开放性。     

青少年男子短跑运动员膝关节等速肌力特征研究

目的：通过对36名二级青少年男子短跑运动员双侧膝关节进行等速测试，探析青少年短跑运动员膝关节向心屈伸肌群的生物力学特性．为运动训练、科学选材及临床康复等提供理论依据。方法：利用Kinitech等速康复肌力测试系统对青少年男子短跑运动员膝关节屈伸肌群进行等速测试。结果：青少年男子短跑运动员双侧膝关节屈伸峰力矩随测试速度的增加呈递减趋势，且膝伸肌大于膝屈肌（P〈0．05），峰力矩屈伸比（V／E）随给定测试速度的增加呈递增趋势；最大功率随测试速度的增大而增加，同一测试速度下屈、伸肌群最大功率无明显差异，左、右侧相比也无显著性差异（600／s伸肌除外）；屈伸肌群达峰力矩的角度（APT）表现为伸肌角度明显低于屈肌角度，随速度增加左右两侧膝关节达峰力矩的角度无显著差异：双侧膝关节屈伸肌群达峰力矩的时间（TPT）随测试速度的增加而减小，同一测试速度下伸肌达峰力矩的时间大于屈肌；右侧膝关节屈肌相对峰力矩（PT／BM）与下肢形态学指标表现出不同程度的正相关。结论：青少年男子短跑运动员膝关节峰力矩变化规律与成年人相一致，但左右侧膝关节屈伸肌群做功能力发展不平衡，屈伸肌群运动达峰力矩角度、达峰力矩的时间存在显著差异。     

引力场的时空特性研究

引力场是一种矢量场,广义相对论对引力问题的描述是非常有效的。分析了广义相对论中的等效原理和广义协变原理,讨论了爱因斯坦引力场方程,研究了相对性原理、引力场中的时间膨胀、长度收缩。     

压缩映射原理及其应用

介绍了压缩映射原理,并论述了压缩映射原理在求方程解的存在性、求一些数列限和求方程近似解中的应用.     

Characteristics of the Achilles Tendon Reflex Following Isometric and Isotonic Exercise

Abstract

An investigation was conducted to determine the effects of fatiguing exercise upon the Achilles tendon reflex. Eleven subjects performed one of four exercise tasks on each of four separate days. The exercise conditions involved low-intensity isometric, high-intensity isometric, low-intensity isotonic or high-intensity isotonic exercise. The low-intensity tasks required a 25% MVC load, while the high-intensity conditions required a 50% MVC load. Results showed that low-intensity isometric exercise reduced reflex force, as well as the time needed to reach peak force, while high-intensity exercise produced an enhancement of reflex force. Half-relaxation time was faster after subjects executed low-intensity isometric exercise, but generally somewhat prolonged following high-intensity isometric exercise. Thus, the Achilles tendon reflex may be either enhanced or depressed depending upon the type and intensity of exercise performed.     

The isolated and combined effects of selected physical activity and ibuprofen on delayed-onset muscle soreness

Delayed-onset muscle soreness refers to the skeletal muscle pain that is experienced following eccentric exercise. The aim of the present study was to examine the physiological effects of physical activity with or without ibuprofen on delayed onset muscle soreness. Forty-four non-athletic male volunteers (age 24.3?±?2.4 years) were randomly assigned to one of four groups: physical activity (n = 11), ibuprofen (n = 11), physical activity and ibuprofen (combination, n = 11), or control (n = 11). The physical activity programme comprised 5?min of walking and jogging, 10?min of static stretching of the hands and shoulder girdle, and 5?min of concentric movements with sub-maximal contractions. The total amount of ibuprofen consumed by a single individual was 2800?mg; this was taken from 1?h before the eccentric actions up to 48?h after it. Delayed onset muscle soreness was induced by performing 70 eccentric contractions of the biceps muscle of the non-dominant side on a modified arm curl machine. Perceived muscle soreness, maximal eccentric contraction, creatine kinase enzyme activity and elbow range of motion were assessed 1?h before and 1, 24 and 48?h after the eccentric actions. The results indicated that, after the eccentric actions, soreness increased (P?<?0.001) across time in all groups, with the highest values being recorded at 24?h. At 24 and 48?h, greater soreness (P <?0.001) was observed in the control group than in the physical activity and combination groups. After the eccentric actions, creatine kinase increased and was elevated (P?<?0.001) compared with baseline in all groups, with values returning to baseline in the physical activity and combination groups by 48?h. However, creatine kinase in the control and ibuprofen groups was still significantly higher than at baseline after 48?h. Creatine kinase was higher (P?<?0.001) in the control group than in physical activity and combination groups at 24 and 48?h. There was also a reduction (P?<?0.001) in elbow range of motion across time. This reduction in elbow range of motion was greater (P?<?0.001) in the control and ibuprofen groups than in the physical activity and combination groups at 1, 24 and 48?h. The reduction in maximum eccentric contraction was greater (P?<?0.001) in the control and ibuprofen groups than in the physical activity group at 24 and 48?h and the combination group at 48?h. In conclusion, the results add to our understanding of the effects of physical activity and the combination of physical activity and ibuprofen in reducing the severity of muscle soreness induced by eccentric exercise. Physical activity conducted before eccentric exercise alleviates muscle soreness. Our results indicate that physical activity with or without ibuprofen helps to prevent delayed-onset muscle soreness.     

蒸压加气混凝土砌块填充墙体裂缝分析及防裂措施

通过对蒸压加气混凝土砌块基本性能的分析，以及对砌块填充墙裂缝的调查，对其开裂原因进行了分析讨论，并就材料的选择、墙体构造、施工等方面提出了相应的防裂措施。     

高速运动物体形象解析

在狭义相对论意义下,运动的物体的测量形象和视觉形象是不同的.根据狭义相对论关于空间的测量理论,对高速运动的点、线以及几种特殊的二维或三维图形进行分析;研究高速运动的物体在某些特殊情况下,其测量形象与视觉形象所发生的畸变程度及其异同点.     

压缩映射原理在求数列极限中的应用

压缩映射原理给出了求不动点的迭代法（或逐次逼近法）．在求数列的极限时,由压缩映射得到的数列必收敛于一个不动点．本文利用压缩映射原理得到了有关数列极限的几个结论,并将此结论应用于高等数学中求数列的极限问题中．