文章目录
1.3 SCOPE OF THE TEXTBOOK
The best way to outline the scope of any scientific text is to describe the topics covered. In this text, the biomechanics of human movement has been defined as the mechanics and biophysics of the musculoskeletal system as it pertains to the performance of any movement skill. The neural system is also involved, but it is limited to electromyography and its relationship to the mechanics of the muscle. The variables that are used in the description and analysis of any movement can be categorized as follows: kinematics, kinetics, anthropometry, muscle mechanics, and electromyography. A summary of these variables and how they interrelate now follows.
在任何科学文本中，描述所涵盖的主题是勾勒范围的最佳方法。在这个文本中，人类运动的生物力学被定义为与任何运动技能的执行相关的肌肉骨骼系统的力学和生物物理学。神经系统也参与其中，但限于肌肉力学和肌肉力学与肌肉力学之间的关系。用于描述和分析任何运动的变量可以归类如下：运动学、动力学、人体测量学、肌肉力学和肌电图。下面是这些变量及其相互关系的概要。
1.3.1 Signal Processing
A major addition to this fourth edition is a chapter on signal processing. Some aspects of signal processing were contained in previous additions; it was decided that all aspects should be combined in one chapter and be given a more rigorous presentation. Why signal processing? Virtually all the variables we measure or analyze come to us in the time domain: EMG, forces, displacements, accelerations, energies, powers, moments, and so on. Thus, they are signals and must be treated like any other signal. We can analyze their frequency content, digitize them, analog or digitally filter them, and correlate or average their waveforms. Based on their signal characteristics, we can make decisions as to sampling rate, minimum length of data files, and filter cutoff frequencies. Also, there are correlation and covariance techniques that allow us to explore more complex total limb and total body motor patterns.
第四版的一个重要补充是关于信号处理的章节。以前的版本中包含了一些信号处理的内容，但决定将所有方面合并到一个章节中，并进行更严格的介绍。为什么需要信号处理呢？几乎我们测量或分析的所有变量都以时间域的形式呈现：肌电图、力、位移、加速度、能量、功率、力矩等等。因此，它们都是信号，必须像处理其他信号一样对待。我们可以分析它们的频域内容，将它们进行数字化，模拟或数字滤波处理，以及相关性和平均化它们的波形。根据信号特性，我们可以决定采样率、数据文件的最小长度和滤波截止频率。此外，还有相关性和协方差技术，可以帮助我们探索更复杂的整体肢体和整体身体运动模式。
1.3.2 Kinematics
Kinematic variables are involved in the description of the movement, independent of forces that cause that movement. They include linear and angular displacements, velocities, and accelerations. The displacement data are taken from any anatomical landmark: center of gravity of body segments, centers of rotation of joints, extremes of limb segments, or key anatomical prominances. The spatial reference system can be either relative or absolute. The former requires that all coordinates be reported relative to an anatomical coordinate system that changes from segment to segment. An absolute system means that the coordinates are referred to an external spatial reference system. The same applies to angular data. Relative angles mean joint angles; absolute angles are referred to the external spatial reference. For example, in a two-dimensional (2D) system, horizontal to the right is 0◦, and counterclockwise is a positive angular displacement.
在描述运动时，运动学变量涉及独立于引起该运动的力的内容。它们包括线性和角度位移、速度和加速度。位移数据可以从任何解剖标志点获取：身体各部分的重心、关节的旋转中心、肢体段的极端点或关键的解剖突起点。空间参考系统可以是相对的或绝对的。相对系统要求所有坐标相对于从部分到部分变化的解剖坐标系进行报告。绝对系统意味着坐标参考了外部的空间参考系统。角度数据也是如此。相对角度指关节角度；绝对角度是指相对于外部空间参考的角度。例如，在二维系统中，水平向右为0°，逆时针为正的角度位移。
The basic kinematic concepts are taught on a 2D basis in one plane. All kinematic displacement and rotational variables are vectors. However, in any given direction or rotation, they are considered scalar signals and can be processed and analyzed as such. In three-dimensional (3D) analysis, we add an additional vector direction, but we now have three planes to analyze. Each segment in 3D analyses has its own axis system; thus, the 3D orientation of the planes for one segment is not necessarily the same as those for the adjacent segments.
基本的运动学概念在二维平面上进行教学。所有的运动学位移和旋转变量都是矢量。然而，在任何给定的方向或旋转中，它们被视为标量信号，并可以按照标量进行处理和分析。在三维分析中，我们增加了一个额外的矢量方向，但现在我们有三个平面来进行分析。在三维分析中，每个段都有自己的坐标系；因此，一个段的三维平面方向不一定与相邻段的方向相同。
1.3.3 Kinetics
The general term given to the forces that cause the movement is kinetics. Both internal and external forces are included. Internal forces come from muscle activity, ligaments, or the friction in the muscles and joints. External forces come from the ground or from external loads, from active bodies (e.g., those forces exerted by a tackler in football), or from passive sources (e.g., wind resistance). A wide variety of kinetic analyses can be done. The moments of force produced by muscles crossing a joint, the mechanical power flowing to or from those same muscles, and the energy changes of the body that result from this power flow are all considered part of kinetics. It is here that a major focus of the book is made, because it is in the kinetics that we can really get at the cause of the movement and, therefore, get some insight into the mechanisms involved and into movement strategies and compensations of the neural system. A large part of the future of biomechanics lies in kinetic analyses, because the information present permits us to make very definitive assessments and interpretations.
运动的原因所产生的力量的总称为动力学。它包括内力和外力。内力来自肌肉活动、韧带或肌肉和关节的摩擦力。外力来自地面或外部载荷，来自主动体（例如橄榄球中的扑倒者所施加的力量）或被动来源（例如风阻力）。可以进行各种各样的动力学分析。肌肉跨越关节产生的力矩、流向或从同样肌肉流出的机械功率以及由此功率流引起的身体能量变化都被视为动力学的一部分。正是在动力学中，我们真正可以揭示运动的原因，从而对涉及的机制、运动策略和神经系统的补偿有一些洞察力。生物力学的未来在很大程度上取决于动力学分析，因为所提供的信息使我们能够做出非常明确的评估和解释。
As with the kinematics, all basic kinetic concepts will be covered in detail in 2D analyses. Three-dimensional analysis adds an additional force vector in the global reference system (GRS), but, because of the two additional planes, there are two additional moment vectors. The 3D analysis techniques are considerably more complex; however, within any of these three planes, the interpretation is the same as in 2D analyses.
与运动学类似，所有基本的动力学概念将在二维分析中详细介绍。三维分析在全局参考系统中增加了额外的力矢量，但由于增加了两个平面，因此还有两个额外的力矩矢量。三维分析技术相对复杂，但在这三个平面中的任何一个平面上，解释与二维分析中的解释是相同的。
1.3.4 Anthropometry
Many of the earlier anatomical studies involving body and limb measurements were not considered to be of interest of biomechanics. However, it is impossible to evolve a biomechanical model without data regarding masses of limb segments, location of mass centers, segment lengths, centers of rotation, angles of pull of muscles, mass and cross-sectional area of muscles, moments of inertia, and so on. The accuracy of any analysis depends as much on the quality and completeness of the anthropometric measures as on the kinematics and kinetics.
许多早期的解剖学研究涉及身体和肢体测量，并没有被认为是生物力学的兴趣所在。然而，如果没有肢体分段的质量数据、质心位置、分段长度、旋转中心、肌肉的拉力角度、肌肉的质量和横截面积、惯性矩等数据，就无法建立生物力学模型。任何分析的准确性与人体测量的质量和完整性一样重要，也与运动学和动力学一样重要。
1.3.5 Muscle and Joint Biomechanics
One body of knowledge that is not included in any of the preceding categories is the mechanical characteristics of the muscle itself. How does its tension vary with length and with velocity? What are the passive characteristics of the muscle—mass, elasticity, and viscosity? What are the various characteristics of the joints? What are the advantages of double-joint muscles? What are the differences in muscle activity during lengthening versus shortening? How does the neural recruitment affect the muscle tension? What kind of mathematical models best fit a muscle? How can we calculate the center of rotation of a joint? The final assessment of the many movements cannot ignore the influence of active and passive characteristics of the muscle, nor can it disregard the passive role of the articulating surfaces in stabilizing joints and limiting ranges of movement.
在之前的分类中没有包含的一项知识是肌肉本身的力学特性。肌肉的张力如何随长度和速度变化？肌肉的被动特性是什么——质量、弹性和黏性？关节有哪些不同的特性？双关节肌肉有什么优势？在拉长和缩短过程中肌肉活动有什么不同？神经招募如何影响肌肉张力？什么样的数学模型最适合描述肌肉？我们如何计算关节的旋转中心？对于许多运动的最终评估不能忽视肌肉的主动和被动特性的影响，也不能忽视关节表面的被动作用在稳定关节和限制运动范围方面的作用。
1.3.6 Electromyography
The neural control of movement cannot be separated from the movement itself, and in the electromyogram (EMG) we have information regarding the final control signal of each muscle. The EMG is the primary signal to describe the input to the muscular system. It gives information regarding which muscle or muscles are responsible for a muscle moment or whether antagonistic activity is taking place. Because of the relationship between a muscle’s EMG and its tension, a number of biomechanical models have evolved. The EMG also has information regarding the recruitment of different types of muscle fibers and the fatigue state of the muscle.
运动的神经控制与运动本身是密不可分的，在肌电图（EMG）中我们可以获得有关每个肌肉的最终控制信号的信息。 EMG是描述肌肉系统输入的主要信号。它提供了有关哪个肌肉或哪些肌肉负责产生肌肉力矩，或者是否存在拮抗活动的信息。由于肌肉的EMG与其张力之间的关系，出现了许多生物力学模型。EMG还提供了有关不同类型肌纤维的招募和肌肉的疲劳状态的信息。
1.3.7 Synthesis of Human Movement
Most biomechanical modeling involves the use of inverse solutions to predict variables such as reaction forces, moments of force, mechanical energy, and power, none of which is directly measurable in humans. The reverse of this analysis is called synthesis, which assumes a similar biomechanical model, and using assumed moments of force (or muscle forces) as forcing functions, the kinematics are predicted. The ultimate goal, once a valid model has been developed, is to ask the question, “What would happen if?” Only through such modeling are we able to make predictions that are impossible to create in vivo in a human experiment. The influence of abnormal motor patterns can be predicted, and the door is now open to determine optimal motor patterns. Although synthesis has a great potential payoff, the usefulness of such models to date has been very poor and has been limited to very simple movements. The major problem is that the models that have been proposed are not very valid; they lack the correct anthropometrics and degrees of freedom to make their predictions very useful. However, because of its potential payoff, it is important that students have an introduction to the process, in the hope that useful models will evolve as a result of what we learn from our minor successes and major mistakes.
大多数生物力学建模都涉及使用逆解法来预测诸如反作用力、力矩、机械能和功率等无法直接测量的变量。该分析的反向过程称为合成，它假设了一个类似的生物力学模型，并使用假设的力矩（或肌肉力量）作为强迫函数来预测运动学。一旦建立了有效的模型，最终目标就是提出问题：“如果…会发生什么？”只有通过这种建模方法，我们才能进行不可能在人体实验中创建的预测。可以预测异常运动模式的影响，并开始确定最佳运动模式。尽管合成具有巨大的潜在回报，但迄今为止，这种模型的实用性非常差，仅限于非常简单的运动。主要问题在于已提出的模型缺乏有效性，缺乏正确的人体测量数据和自由度，使得它们的预测没有多大用处。然而，由于其潜在回报的重要性，让学生对这个过程有所了解是很重要的，希望我们从小小的成功和重大的错误中学到的东西能够促进有用的模型的发展。
1.3.8 Biomechanical Motor Synergies
With the increased technology, biomechanics has made great strides in analyzing more complex total body movements and, because of the considerable interactions between adjacent muscle groups, it is becoming necessary to identify motor synergies. In a new chapter, we use several techniques to identify two or more muscle groups acting synergistically toward a common goal.
随着技术的进步，生物力学在分析复杂的全身运动方面取得了重大进展。由于相邻肌肉群之间存在复杂的相互作用，因此有必要识别运动协同。在新的章节中，我们使用多种技术来识别两个或更多肌肉群共同努力实现共同目标的情况。该章节的重点是理解和描述多个肌肉群在复杂运动中的协调行动。