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

鹰肌-肌腱单元是一种复杂的生物致动器，能够向骨骼施加相当大的力，以稳定和/或移动身体的各个部分，并吸收赋予身体的能量。由于肌腱(MT)单位在人体功能和生活质量中扮演着不可或缺的角色，人们对了解1)MT单位的基本结构特性，2)MT特性在整个生命过程中如何变化以及对改变的环境刺激(例如，停用、运动)的反应，3)与MT损伤相关的危险因素，4)如何最好地在一生中维持或恢复正常的MT功能，以及5)如何补偿MT功能的损失，都有很大的兴趣。在活体内量化肌腱单位的结构特性的困难限制了对这些单位的正常和适应性行为的了解。这项研究的两个目标是：1)建立一种非侵入性地量化肌肉和肌腱在体内的力-变形特性的方法；2)通过使用该方法来验证这种方法的有效性，通过使用该方法来研究两个具体问题：(A)在类似体力活动水平的人进行最大等长肌肉收缩时，肌腱产生的应变是否与年龄有关；(B)在具有相似初始体力活动水平的人中，肌腱结构特性适应速度相对于肌肉力量适应速度是否存在与年龄相关的差异？一种结合超声、力传感器、为了研究腓肠肌-比目鱼肌-跟腱复合体，正在开发一种脚踝测试夹具，它提供了脚底屈曲脚踝的主要力量。超声图像将用于量化跟腱的长度和横截面积、肌束方向以及肌肉收缩或关节运动期间解剖标志的移动。脚踝测试设备将用于量化给定肌肉努力的脚踝位置和扭矩。人体测量数据将被用来将关节扭矩与跟腱力量联系起来。量化了预应力筋的力-变形和应力-应变行为。这些方法的有效性将使用仪器化的身体标本进行测试。组织力和/或变形将被控制在身体腿内，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应用。三个年龄段的25名受试者将参加为期16周的力量训练计划和为期8周的取消训练计划。每隔两周，受试者将进行逐渐增加的等长足底屈曲力，同时记录跟腱的力量和变形。这些数据将被用来构建肌腱的力-变形曲线，并量化肌腱硬度、最大等长肌力和最大等长肌力时的肌腱应变。此外，比目鱼肌和腓肠肌的肌电图将被记录下来，以量化这些肌肉努力期间的肌肉招募策略。数据将在受试者、测试时段和年龄组之间进行比较。

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.