Shoulder control and influence of physiological perturbations

上肢的主要作用是定位手来执行各种活动，从高强度的爆炸动作到复杂的抓握任务。为了适应这些角色，肩部需要高水平的机动性。因此，肩部控制在很大程度上依赖于本体感觉信息，以及在选择运动命令时对这些信息的处理和整合。因此，肩膀的控制可能会受到已知的影响关节控制的因素的影响，如疼痛和疲劳（特别是在手臂抬高的位置），而这些变化所涉及的机制尚不清楚。相反，训练通过加强内部表征和加强运动的前馈控制来改善运动控制。训练是否有潜力使运动表征对诸如疼痛和疲劳等扰动的不利影响更强大，例如通过产生更多依赖前馈机制的运动命令，仍然相对未被探索。在接下来的5年里，我的研究计划将调查疼痛和疲劳后肩部控制变化的潜在机制（obj1），并研究中枢神经系统是否有能力利用运动学习来保护自己免受这些生理扰动的影响（obj2）。***首先，将研究疼痛和肌肉疲劳对肩部控制的影响，以及这些扰动的注意需求（Obj.1）。在不同的项目中，不同组的健康受试者将在手臂位置升高（使用机器人外骨骼）的过程中暴露于生理扰动（疼痛或疲劳），或疼痛或疲劳和注意力需求的组合（使用双重任务），并与对照组进行比较。肩部控制将以运动模式和中央运动控制为特征。Obj.1将提高我们对肩控在面对日常生活中常见的扰动时的适应性的理解。***为了评估运动学习是否会产生更前馈的控制，从而减少扰动的负面影响（obj2），实验对象组将连续几天参加训练课程（无扰动的到达执行）。在训练前和训练后，将对有生理扰动的肩部控制进行评估。Obj.2将引导我们更好地理解感觉运动系统如何保护自己免受这些扰动，以尽量减少它们的影响。总之，考虑到上肢在许多运动和与工作相关的活动中被用于抬高手臂的位置，这个项目将使人们更深入地了解必须在这些位置上进行重复运动的人如何根据疼痛或疲劳的存在来调整他们的肩膀控制，以尽量减少他们的影响并继续保持高水平的表现。**

The primary role of the upper limb is to position the hand to perform various activities ranging from high-powered explosive actions to complex prehensile tasks. To accommodate these roles, high level of mobility is required at the shoulder. Shoulder control therefore relies heavily on proprioceptive information and on the processing and integration of this information in the selection of motor commands. As a result, shoulder control can be affected by factors known to affect joint control such as pain and fatigue (especially in arm elevation positions), and the mechanisms involved in such changes are not well understood. Conversely, training improves motor control by strengthening the internal representation and by reinforcing feedforward control of movements. Whether training has the potential to make motor representations more robust against the adverse effects of perturbations such as pain and fatigue, for example by producing motor commands that rely more on feedforward mechanisms, is still relatively unexplored. Over the next 5 years my research program will investigate the mechanisms underlying changes in shoulder control following pain and fatigue (Obj.1), and study if the central nervous system has the capacity to protect itself from the influence of these physiological perturbations using motor learning (Obj.2). ***First, the effects of pain and muscle fatigue on shoulder control will be investigated, as well as the attentional demand of these perturbations (Obj.1). In different projects, different groups of healthy subjects will be exposed during reaching tasks in elevated arm positions (using a robotic exoskeleton) to either a physiological perturbation (pain or fatigue), or a combination of pain or fatigue and attentional demand (using dual task), and compared to a control group. Shoulder control will be characterized by movement patterns and central motor control. Obj.1 will improve our understanding into the adaptation of shoulder control when confronted with perturbations commonly found during daily life.***To assess if motor learning results in a more feedforward control that decreases the negative influence of perturbations (Obj.2), groups of subjects will take part in training sessions (execution of reaching without perturbation) during consecutive days. Shoulder control with a physiological perturbation will be evaluated before and after the training period. Obj.2 will lead to a better comprehension of how the sensorimotor system protects itself from these perturbations to minimize their effects. In conclusion, given that the upper limb is used in elevated arm positions in many sports and work-related activities, this program will lead to greater insight on how people that have to perform repetitive movements in these positions adapt their shoulder control with the presence of pain or fatigue in order to minimize their effects and to continue performing at a high level. **