Contributions of Neural and Mechanical Input to Spinal Motoneuron Output in Human Force Control

功能性动作的产生是可塑性的；它可以被训练来提高输出，随着时间的推移，它会随着年龄的增长而恶化。这种与年龄相关的运动控制功能退化在女性中比男性更明显。在接下来的5年里，将进行研究，以确定脊髓运动神经元输出在产生稳定运动中的贡献，以了解与年龄相关的女性力量控制能力比男性更大的下降。调节二头肌运动神经元输出的脊髓输入将在评估等长收缩和动态收缩的力量控制以及年轻(18-30岁)和老年(75岁)男性和女性肘屈肌的功能运动时进行量化。通过短头和长头不同的解剖和生理间隔，二头肌是研究运动神经元输出的微小变化如何影响力量产生的理想选择，特别是对功能性运动至关重要的前臂控制。最初的项目将集中在反射反馈在调节头部之间不同的运动神经元输出方面的贡献，以及对力量产生的影响。功能性运动将通过举起和放下杯子以量化运动神经元输出的任务来建模，其中动态收缩的控制任务与功能任务的位置和加速度相匹配。实验将使用体表和留置肌电(EMG)来测量特定肌肉和运动单位的活动，这些肌肉和运动单位调节稳定收缩的产生。超声检查用于量化肌肉和肌腱的力学作用。除了神经输出，通过肌肉和肌腱的力传递是稳定的力控制不可或缺的一部分。通过一系列的研究，我们将首次量化功能性运动中的单个运动单位的活动，并确定反射反馈是如何整合在协同肌室之间改变脊髓运动神经元输出的，从而随着男性和女性年龄的增长而产生稳定收缩的进化。这项研究将产生关于人类脊髓网络的基础知识，这些知识共同有助于理解运动神经元在调节产生功能性上肢运动的力传递中的输出。这项研究意义重大，因为神经和力学之间的整合对于理解神经肌肉系统的可塑性是不可或缺的，神经肌肉系统的可塑性是导致特定性别、年龄相关的功能运动下降的原因。与之前的调查一致，这项研究计划将为大约20名高素质人员提供高级培训，使其能够发展适用于基础人体运动科学科学发现的神经生理学的技术技能。

Production of functional movement is malleable; it can be trained to improve output and over time it deteriorates with age. This age-related functional deterioration in movement control is more pronounced in women than in men. Over the next 5 years, studies will be conducted to ascertain the contributions of spinal motoneuron output in the production of steady movement to understand greater age-related decline in force control in women compared to men. Spinal inputs that modulate motoneuron output in the biceps brachii will be quantified in the evaluation of force control in isometric and dynamic contractions as well as functional movement in the elbow flexors of young (18-30 years) and old (>75 years) men and women. The biceps brachii muscle, through distinct anatomical and physiological compartments of the short and long heads are ideal for studying how small changes in motoneuron output impacts force production, especially forearm control that is central to functional movement. Initial projects will focus on the contribution of reflex feedback in modulating motoneuron output differentially between heads, and the impact on force production. Functional movement will be modeled through the task of lifting and lowering a cup for drinking to quantify motoneuron output with control tasks of dynamic contractions that are matched for position and acceleration with the functional task. Experiments will use surface and indwelling electromyography (EMG) to measure the activity of specific muscles and motor units that regulate the production of steady contractions. Ultrasonography is included to quantify the mechanical contributions of muscle and tendon. Additional to neural output, force transfer through muscle and tendon is integral to steady force control. Through a series of investigations we will be the first to quantify single motor unit activity during functional movement and ascertain how reflex feedback is integrated to alter spinal motoneuron output between synergist muscle compartments in the evolution of producing steady contractions as men and women age. This research will generate fundamental knowledge about spinal networks in humans that collectively contribute to understanding motoneuron output in the regulation of force transfer that creates functional upper limb movement. This research is significant as integration between neural and mechanics is integral to understanding the plasticity of the neuromuscular system that contributes to sex-specific age-related decline of functional movement. Consistent with prior investigations, this research program will result in advanced training for approximately 20 highly qualified personnel enabling technical skill development in neurophysiology applicable to scientific discovery in basic human movement science.