Shoulder control and influence of physiological perturbations

点击翻译按钮获取中文摘要

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. **