Impact of control mechanisms and tissue morphology on upper extremity loading

与工作相关的疾病每年花费加拿大人数十亿美元。有必要充分了解上肢组织（肩、臂和手）在工作中过载的机制。这些机制的有趣和复杂之处在于，它们是在很长一段时间内发展起来的，因此很难确定是什么导致了损害。这些疾病涉及肌肉、结缔组织（如网球肘、肌腱炎）和周围神经（如腕管综合征）。在了解这些疾病并使工人的工作更安全之前，有必要描述健康组织如何对一系列负荷条件作出反应的机制。我的研究项目是评估健康组织对各种姿势、负荷、干扰任务、疲劳（局部和中枢）以及衰老的反应。我们还必须了解解剖学和运动控制之间复杂的相互作用。研究表明，负荷、姿势和运动与组织超载密切相关，这可能导致组织损伤。然而，大多数研究都是相关的，并没有解决这些组织超载的原因和方式。我们有一个基本的需求，那就是了解组织是如何对工作和其他各种各样的条件做出反应的。如果不了解这些，我们可能会给身体带来不必要的压力。我的研究项目系统地调查了肌肉负荷的影响，通过监测手臂运动，肌肉活动和他们的相互作用，使用计算机为基础的建模。我们使用磁共振成像（MRI）和超声检查不同姿势的手腕组织在捏动作中的结构变化。这些研究确定了腕部神经压迫的机制。我们还检查了肩膀、手臂和手的肌肉激活模式（时间和大小），以确定肌肉如何在特定任务中产生运动。增加任务的复杂性可以改变某人执行任务的方式。特别是，增加一个与主要任务竞争的任务，比如握力或脑力消耗任务，可能会对结果有害。控制手部、手臂和肩部肌肉的代偿策略可能表明哪些个体容易受到更大的个体肌肉负荷、疲劳和损伤。此外，通过对新鲜肌肉和疲劳肌肉进行比较研究，我们可以确定人们在装配线上等疲惫的刻板动作时的处理方式。这项研究计划的一个主要部分是开发和改进我们的计算机模型，以预测手臂和手内部的力。通过在计算机模型中结合肌肉活动和解剖学信息，我们可以测试有关疾病如何发展和如何预防的理论，并提出“如果……会发生什么？”这些问题，否则在生物中无法得到道德上的回答。*****

Work-related disorders cost Canadians billions of dollars every year. There is a great need to fully understand the mechanisms by which tissues of the upper extremity (shoulder, arm, and hand) become overloaded at work. What makes these mechanisms interesting and complex is that they develop over a long period of time, making it difficult to pinpoint what caused the damage. These disorders involve muscle, connective tissue (e.g. tennis elbow, tendinitis), and peripheral nerves (e.g. carpal tunnel syndrome). Before understanding these disorders and making jobs safer for workers, it is essential to characterize the mechanisms underlying how healthy tissues respond to a range of loading conditions. My research program that evaluates the response of healthy tissues to a variety of postures, loads, interfering tasks, and fatigue (localized and central), as well as aging. We must also understand the complex interactions between anatomy and the control of movement. ***Studies indicate that loads, postures and motion are highly linked to overloading tissues which may lead to tissue damage. However, the majority of studies are correlative and do not address why and how these tissues are overloaded. We have a fundamental need to understand how tissues react to the plethora of conditions, at work and otherwise. Without this knowledge, we may cause the unwanted effect of over stressing the body. My research program methodically investigates the effects of muscular loading by monitoring arm movement, muscle activity and their interactions using computer-based modeling. We use magnetic resonance imaging (MRI) and ultrasound to examine structural changes in the tissues of the wrist in different postures during pinching actions. These studies determine mechanics of nerve compression at the wrist. We also examine muscle activation patterns (timing and magnitude) of the shoulder, arm and hand to determine how muscles work to create movement in specific tasks. Adding complexity to tasks can alter how someone performs the task. In particular, adding a task that competes with the main task, such as a grip or a mentally taxing task, may be detrimental to the outcome. Compensatory strategies to control the hand, arm and shoulder muscles may indicate which individuals are susceptible to greater individual muscle loading, fatigue and injury. Further, by performing studies comparing muscles fresh versus fatigued, we can determine the way people deal with tiring stereotypical movements like on an assembly line. A major part of this research program is to develop and improve our computer models to predict forces inside the arm and hand. By combining muscle activity and anatomical information in a computer model, we can test theories on how disorders develop and how to prevent them as well as ask "what would happen if ...?" questions that otherwise could not be answered ethically in living beings.*****