A Non-Invasive Approach for Studying Muscle-Tendon In-vivo

0201829霍金斯肌肉-肌腱单元是复杂的生物致动器，能够向骨骼施加相当大的力，以稳定和/或移动身体的部分，并吸收传递给身体的能量。由于肌肉-肌腱（muscle-tendon，MT）单位在人体功能和生活质量中起着不可或缺的作用，因此人们对理解MT单位的基本结构特性，MT特性在整个生命过程中以及对改变的环境刺激的响应中如何变化有着相当大的兴趣（例如废用、运动），3）与MT损伤相关的风险因素，4）如何在整个生命中最好地维持或恢复正常MT功能，以及5）如何补偿MT功能的损失。量化体内肌肉肌腱单元的结构特性的困难限制了对这些单元的正常和适应性行为的理解。本研究的两个目标是：1）开发一种方法来非侵入性地量化体内肌肉和肌腱力-变形特性，以及2）通过使用该方法来研究两个具体问题来证明该方法的实用性：（a）在由相似身体活动水平的人进行的最大等长肌肉收缩期间，肌腱中诱导的应变是否存在与年龄相关的差异，和（B）在相似的初始体力活动水平的人中，肌腱的结构特性适应率相对于肌肉力量适应率是否存在与年龄相关的差异？正在开发一种结合超声检查、力传感器和踝关节测试夹具的方法来研究腓肠肌-比目鱼肌-跟腱复合体，该复合体提供踝关节跖屈的主要力。 超声图像将用于量化跟腱的长度和横截面积、肌肉束方向以及肌肉收缩或关节运动期间解剖标志的运动。踝关节测试装置将用于量化踝关节位置和给定肌肉力量的扭矩。人体测量数据将用于将关节扭矩与跟腱力相关联。对预应力筋的受力变形和应力应变特性进行了定量分析。这些方法的有效性将使用内固定尸体标本进行测试。组织力和/或变形将被控制在尸体腿内，并与非侵入性超声和关节测试程序确定的类似量进行比较。通过研究衰老和运动对MT行为和关节力学的影响，将研究非侵入性技术在研究基本肌肉-肌腱性能和适应性方面的效用。三个年龄组的25名受试者将参加为期16周的力量训练计划和为期8周的停训计划。每两周，受试者将进行逐渐增加的等长跖屈努力，同时记录跟腱力和变形。这些数据将用于构建肌腱的力-变形曲线，并量化肌腱刚度、最大等长肌力和最大等长肌力期间的肌腱应变。此外，将记录比目鱼肌和腓肠肌的肌电图，以量化这些肌肉活动期间的肌肉募集策略。将在受试者、测试阶段和年龄组之间比较数据。

0201829HawkinsMuscle-tendon units are complex biological actuators able to impart considerable force to bones to stabilize and/or move segments of the body and to absorb energy imparted to the body. Due to the integral role muscle-tendon (MT) units play in human function and quality of life, considerable interest exists in understanding 1) the basic structural properties of MT units, 2) how MT properties change throughout life and in response to altered environmental stimuli (e.g. disuse, exercise), 3) risk factors associated with MT injury, 4) how best to maintain or restore normal MT function throughout life, and 5) how to compensate for a loss in MT function. Difficulty in quantifying the structural properties of muscle-tendon units in-vivo has limited understanding of the normal and adaptive behavior of these units. The two objectives of this study are: 1) to develop a methodology to non-invasively quantify muscle and tendon force-deformation properties in-vivo, and 2) to demonstrate the utility of this approach by using it to investigate two specific questions (a) are there age-related differences in the strain induced in a tendon during a maximum isometric muscle contraction performed by people of similar physical activity level, and (b) are there age-related differences in the rate of structural property adaptation of a tendon relative to the rate of muscle strength adaptation in people of similar initial physical activity level?A methodology that combines ultrasonography, a force transducer, and an ankle-testing fixture is being developed to study the Gastrocnemius-Soleus-Achilles Tendon Complex, which provide the primary forces to plantar flex the ankle. The ultrasound images will be used to quantify the length and cross-sectional area of the Achilles Tendon, muscle fascicle orientation, and movement of anatomical landmarks during muscle contractions or joint movements. The ankle-testing device will be used to quantify ankle position and torque for a given muscle effort. Anthropometric data will be used to relate joint torque to Achilles Tendon force. Force-deformation and stress-strain behaviors of the tendon are quantified. The validity of these methods will be tested using instrumented cadaver specimens. Tissue force and/or deformation will be controlled within the cadaver leg and compared to similar quantities determined from the non-invasive ultrasound and joint testing procedures.The utility of the non-invasive technique for studying basic muscle-tendon performance and adaptation will be investigated by studying the affects that aging and exercise have on MT behavior and joint mechanics. Twenty-five subjects within three age groups will participate in a 16-week strength-training program and an 8-week detraining program. Every two weeks the subjects will perform gradually increasing isometric plantar flexion efforts while Achilles tendon force and deformation are recorded. These data will be used to construct force-deformation curves for the tendon and to quantify tendon stiffness, maximum isometric muscle strength, and tendon strain during maximum isometric muscle force. Additionally, electromyography from the soleus and gastrocnemius muscles will be recorded to quantify muscle recruitment strategies during these muscular efforts. Data will be compared between subjects, test sessions, and age groups.