AGING AND STEADINESS TRAINING

老年人肌肉质量和力量的丧失与健康危险因素的出现和日常生活活动能力的下降有关。这种退化的一个例子是稳定性下降，记录在手和手臂肌肉，但没有在腿部大肌肉。因此，我们假设膝关节伸肌收缩稳定性也随着年龄的增长而下降。力量训练是一种有效的干预，可以最大限度地减少这些变化，包括稳定性的下降。由于力量下降和稳定性之间的联系，我们假设当老年人进行稳定性训练时，这将伴随着肌肉力量的增加。本研究的具体目的是：(1)评估年轻人和老年人的膝关节伸肌力量和收缩稳定性；(2)比较高负荷和轻负荷稳定收缩训练所获得的力量增加；(3)确定力量训练对功能的影响(4)确定有助于力量增加的特定适应。年轻受试者（18-30岁）将接受力量和稳定性评估，与老年受试者（65-80岁）进行比较，老年受试者将被招募参加为期16周的力量训练计划。老年受试者将被随机分配到四个实验组：轻负荷-稳定收缩、轻负荷（无反馈）、重负荷（无反馈）和对照组。结果变量将是肌肉力量和稳定性，通过MRI测量的肌肉横截面积和体积，肌肉激活的时间（EMG）和空间（基于MRI的T2松弛时间）评估，拮抗剂肌肉的协同激活以及腿部肌肉的物理功能表现。年龄较大的受试者将在培训计划之前和之后接受测试。这项研究将提供与年龄相关的重要功能肌肉稳定性下降的信息，非典型肌肉训练计划导致的特定适应，并可能提出替代干预措施来抵消老年人肌肉力量的损失。

The loss of muscle mass and strength in older adults is associated with the appearance of health-risk factors and a reduction in the ability to perform the activities of daily living. An example of this deterioration is a decline in steadiness, documented in hand and arm muscles, but not in large leg muscles. Accordingly, we hypothesize that knee extensor contraction steadiness also declines with age. Strength training is an effective intervention that minimizes these changes, including the decrease in steadiness. Because of the association between declining strength and steadiness, we hypothesize that when older adults train for steadiness, this will be accompanied by an increase in muscle strength. The specific aims of this study are: (1) to assess knee extensor strength and contraction steadiness in young and older adults (2) to compare the strength increases achieved with high-load vs. light-load, steady- contraction training; (3) to determine the effects of strength training on function (4) to identify specific adaptations that contribute to the increase in strength. Young subjects (18-30) will undergo strength and steadiness assessment for comparison with older subjects (65-80), who will be recruited to participate in a 16-week strength-training program. The older subjects will be randomly assigned to one of four experimental groups: Light load-steady contraction, light load (no feedback), heavy load (no feedback), and a control group. The outcome variables will be muscle strength and steadiness, muscle cross-sectional area and volume measured by MRI, temporal (EMG) and spatial (MR-based T2 relaxation time) assessment of muscle activation, coactivation of antagonist muscles, and physical functional performance of the leg muscles. Older subjects will be tested before, and after the training program. This study will provide information on the age-related decline in steadiness of important functional muscles, specific adaptations resulting from an atypical muscle training program, and will likely suggest an alternative intervention to offset the loss of muscle strength in older adults.