Changes in Control of Movement Timing and Stability With Muscle Fatigue

描述（由申请人提供）：与工作相关的肌肉骨骼损伤与重复运动、不正确的姿势和肌肉疲劳有关。肌肉疲劳和/或由疲劳引起的肌肉失衡可能作为损伤发展的直接原因和/或中间因素很重要。为了制定适当的预防损伤处方和有效的康复策略，了解疲劳肌肉和肌肉不平衡如何影响目标导向运动的控制至关重要。 30 名健康的年轻人将使用节拍器及时执行 5 分钟类似于锯切的上肢低负荷连续工作任务。然后，他们将执行两种疲劳方案中的任一种，以引起广泛疲劳（更多锯切，阻力增加）或局部肌肉疲劳（重复肩部弯曲）。然后他们将进行另外 5 分钟的低负载锯切。在协议的每个部分之间，将记录感知用力率和最大自主收缩 (MVC)。在所有锯切试验期间，将连续记录运动学、手柄力和肌肉活动 (EMG)。正确的运动时机对于许多重复性任务至关重要。 PI 将应用新颖的方法将主要时空任务变量的变异性分解为直接影响任务目标实现和不影响任务目标实现的新变量。他们将量化每个结果时间序列的变异性和周期到周期的时间相关结构，以确定人类如何在冗余的目标导向运动中控制运动时间，以及这种控制如何随着广泛或局部的肌肉疲劳而改变。 在重复性任务中控制运动稳定性对于最大限度地降低受伤风险也至关重要。然而，肌肉疲劳和/或肌肉不平衡如何影响运动稳定性的控制尚不清楚。 PI 将应用其实验室开发的创新分析方法，直接量化每个受试者在连续锯切任务试验期间对小扰动的固有敏感性。这些分析将使他们能够确定广泛与局部肌肉疲劳如何影响运动稳定性的控制。 这个 R03 项目将产生重要的新见解，包括肌肉疲劳如何影响任务表现、人类用于实现这种表现的神经肌肉和生物力学策略，以及受试者采用的基本控制策略。回答这些基本问题对于了解肌肉骨骼损伤发展的机制以及制定治疗这些损伤患者的有效康复策略至关重要。上肢肌肉骨骼损伤（不包括腰痛）是一个严重且昂贵的医疗保健问题，每年影响超过 375,000 名工作场所人员。肌肉疲劳和肌肉失衡是造成这些伤害的重要原因。因此，更好地了解局部肌肉疲劳引起的肌肉疲劳和肌肉失衡如何影响人类控制重复运动的时机和动态稳定性非常重要。

DESCRIPTION (provided by applicant): Work-related musculoskeletal injuries have been linked to movement repetition, improper postures, and muscle fatigue. Muscle fatigue and/or the muscle imbalances that result from fatigue may be important as direct causes and/or intermediary factors in injury development. To develop appropriate prescriptions for preventing injuries and effective strategies for rehabilitation, it is critical to understand how fatigue muscle and muscle imbalances affect the control of goal-directed movements. Thirty healthy young adults will perform an upper extremity low-load continuous work task similar to sawing for 5 minutes in time with a metronome. They will then perform either of two fatigue protocols to induce either widespread fatigue (more sawing with increased resistance) or localized muscle fatigue (repetitive shoulder flexion). They will then perform another 5 minutes of low-load sawing. Between each segment of the protocol, rates of perceived exertion and maximum voluntary contractions (MVCs) will be recorded. Kinematics, handle forces, and muscle activity (EMG) will be recorded continuously during all sawing trials. Proper movement timing is critical to many repetitive tasks. The PIs will apply novel methods to decompose the variability in the primary spatial-temporal task variables into new variables that directly affect achieving the task goal and those that do not. They will quantify both the variability and cycle-to-cycle temporal correlation structure of each resulting time series to determine how humans control movement timing during redundant goal-directed movements and how this control is altered with either widespread or localized muscle fatigue. Controlling movement stability during repetitive tasks is also critical for minimizing risk of injury. However, how muscle fatigue and/or muscle imbalances affect the control of movement stability is not well understood. The PIs will apply innovative analysis methods, developed by their lab, to directly quantify each subject's innate sensitivity to small perturbations during the continuous sawing task trials. These analyses will allow them to determine how both widespread vs. localized muscle fatigue affect the control of movement stability. This R03 project will yield vital new insights into how muscle fatigue affects task performance, about the neuromuscular and biomechanical strategies humans use to achieve this performance, and about the underlying control policies subjects adopt. Answering these fundamental questions is critical for understanding the mechanisms of musculoskeletal injury development and for developing effective rehabilitation strategies for treating patients with these injuries. Upper extremity musculoskeletal injuries (not including low back pain) are a significant and costly health care problem affecting over 375,000 people in the work-place each year. Muscle fatigue and muscle imbalances are significant contributors to these injuries. Therefore, it is important to better understand how muscle fatigue and muscle imbalances caused by localized muscle fatigue affect how humans control the timing and dynamic stability of repetitive movements.