Biomechanical Modeling of Posture and Movement Coordination: Fatigue, Gender and Aging effects

在日常生活活动中，重复性的动作常常会导致疲劳。疲劳对单个肌肉和关节的影响已经有了充分的记录；我们是第一批描述重复性运动引起的疲劳的全身后果的人之一，揭示了利用肌肉骨骼系统冗余的策略。我们发现，健康的疲劳适应与高运动变异性和额外关节和肌肉的招募有关，以促进疲劳发展的任务。这些适应与跨越感觉、本体感受和运动系统的变化有关。然而，性别和年龄等个人因素对工作疲劳适应能力的影响尚不清楚，这限制了机械模型在准确传达正常健康疲劳适应模式范围方面的有效性。最近的统计数据显示，女性报告与工作有关的颈部/肩部MSD的比例更高。我之前发表了一个基于感觉运动控制基础知识的理论模型来解释这一观察；然而，这个模型的许多元素还没有被确定。此外，加拿大人口的预期寿命持续增加，加拿大劳动力的老龄化和退休年龄的提高，使得我们有必要了解衰老如何影响一个人适应疲劳的能力，无论是男性还是女性。本研究计划的总体、长期目标是更好地了解健康人类上肢重复运动的生物力学和控制方面。现在将使用以下具体目标来解决这个问题：1)测量性别/性别对肌肉、全身和重复性上肢运动引起的疲劳反应的感觉运动方面的影响；2)测量健康衰老对重复性上肢运动疲劳反应的肌肉、全身和感觉运动方面的影响；3)确定性别/性别和年龄对重复性上肢运动诱发疲劳反应的任务特异性影响。健康受试者（两组性别平衡：一组为年轻人（20-29岁），一组为老年人（54-65岁））将被招募来执行低精度上肢任务和或高精度上肢任务，直到疲劳。当受试者执行任务至疲劳时，我们将记录颈部/肩部感官以及全身运动学、动力学和肌肉活动特征。最近发展的变异性和肌肉间分析技术将用于描述疲劳相关的运动策略。结果将有助于更好地理解和建模性别/性别和年龄对疲劳反应的影响。这些知识可以整合到机械模型和工作场所伤害预防方法中。

Repetitive motions are often accomplished during activities of daily living and can lead to fatigue. The effects of fatigue on individual muscles and joints have been well documented; we were among the firsts to describe the whole-body consequences of repetitive motion-induced fatigue, uncovering strategies that take advantage of the musculoskeletal system's redundancy. We showed that healthy fatigue adaptations were associated with high movement variability and the recruitment of additional joints and muscles to contribute to the task as fatigue develops. These adaptations have been related to changes spanning the sensory, proprioceptive and motor systems. However, the effects of personal factors such as gender and aging on the ability to adapt to work-related fatigue is not well known, limiting the validity of mechanical models in accurately conveying the range of normal healthy fatigue adaptations patterns. Recent statistics show that women display a higher rate of reporting work-related neck/shoulder MSD. I have previously published a theoretical model based on fundamental knowledge of sensorimotor control to explain this observation; however, many elements of this model have not been identified yet. Moreover, the consistently increasing life expectancy of the Canadian population, the aging of the Canadian workforce and the increasing retirement age make it important for us to understand how aging affects one's ability to adapt to fatigue, in both men and women. The general, long-term objective of this research program is to gain a better understanding of the biomechanics and control aspects of upper limb repetitive movements in healthy humans. This will now be addressed using the following specific objectives: 1) Measure the effects of sex/gender on muscle, whole body and sensorimotor aspects of the repetitive upper limb motion-induced fatigue response; 2) Measure the effects of healthy aging on muscle, whole body and sensorimotor aspects of the repetitive upper limb motion-induced fatigue response; 3) determine the task-specificity of sex/gender and aging influences on the repetitive upper limb motion-induced fatigue response. Healthy subjects (two gender-balanced groups: one of young adults (20-29 years old), one of older adults (54-65 years old)) will be recruited to perform a low precision upper limb task and-or a high precision upper limb task until fatigue. We will record the neck/shoulder sensory, as well as the whole-body kinematic, kinetic and muscle activity characteristics as subjects perform the task to fatigue. Recently developed variability and between-muscle analysis techniques will be used to profile the fatigue-associated motor strategies. Results will help better understand and model the the effects of sex/gender and aging on the fatigue response. This knowledge could be integrated into mechanical models and into workplace injury prevention approaches.