van den Bogert A J
Faculty of Physical Education, University of Calgary, Alberta, Canada.
Exerc Sport Sci Rev. 1994;22:23-51.
Load in the human body can be quantified as force, stress, or strain, depending on the anatomical structure and the measuring technique. Direct measurements of these variables are invasive and only possible in animals or in small-scale in vivo studies in humans. Miniaturization of transducers and electronics may open new possibilities for direct measurements of load in the human body. Studies with a large number of human subjects, and routine analysis of patients, are done using noninvasive techniques: EMG analysis for muscle forces, kinematic analysis for ligament forces, and inverse dynamics for resultant joint loads. Inverse dynamics is the most general method and is applicable to all joints in the human body. Important limitations of inverse dynamics are due to the "distribution problem": the separation of resultant loads into the individual forces in muscles and other structures. Dynamic optimization is the most promising solution method for this problem. Inverse dynamics also relies heavily on the assumption that body segments are rigid. The errors caused by this simplification are most severe in impact and vibration studies. Computer simulation is a well-established method for load analysis in mechanical engineering but is relatively rare in biomechanics. Replacing the human test subject by a mathematical model has many advantages, mainly for reproducibility and understanding of the results. Models for mechanical properties and control of muscles are an important and difficult part of computer simulation. For this reason, computer simulation has only been applied for load analysis in impact simulations, where the muscles can be regarded as passive, or for certain special problems where similarly simple muscle models can be used. In the future, we may see more applications of computer simulation for analysis of more complex activities, such as gait and sports.
根据解剖结构和测量技术的不同，人体负荷可以用力、应力或应变来量化。对这些变量进行直接测量具有侵入性，并且仅在动物或人体小规模体内研究中可行。传感器和电子设备的小型化可能为人体负荷的直接测量开辟新的可能性。针对大量人类受试者的研究以及对患者的常规分析，是使用非侵入性技术进行的：通过肌电图分析来测量肌肉力量，通过运动学分析来测量韧带力量，通过逆动力学来测量关节合力。逆动力学是最通用的方法，适用于人体的所有关节。逆动力学的重要局限性源于“分布问题”：将合力分解为肌肉和其他结构中的各个力。动态优化是解决这个问题最有前景的方法。逆动力学还严重依赖于身体各部分是刚性的这一假设。在冲击和振动研究中，这种简化所导致的误差最为严重。计算机模拟在机械工程中是一种成熟的负荷分析方法，但在生物力学中相对较少使用。用数学模型取代人体测试对象有很多优点，主要体现在结果的可重复性和可理解性方面。肌肉力学特性和控制模型是计算机模拟的一个重要且困难的部分。因此，计算机模拟仅应用于冲击模拟中的负荷分析（在这种情况下肌肉可被视为被动的），或者用于某些可以使用类似简单肌肉模型的特殊问题。未来，我们可能会看到计算机模拟在分析更复杂的活动（如步态和运动）方面有更多应用。
