Mechanics of the Aging Achilles tendon with implications for walking performance

描述（由申请人提供）：踝关节发电量普遍下降，即使在其他健康的老年人中，也是行走能力随年龄增长而恶化的主要原因。然而，单纯的肌肉强化通常不能显著提高老年人的行走能力，这表明除了肌肉减少症之外，还有其他因素导致了跖屈肌力量随着年龄的增长而下降。我建议研究年龄相关的跟腱力学变化及其对老年人行走能力的影响。本研究的前提是，老化的跟腱表现出体内行为的改变，极大地削弱了在步态推离阶段踝关节跖屈肌的最佳协调能力。初步数据表明，浅层和深层跟腱束表现出明显不同的位移，可能是由于腱束间滑动，这可能是最佳协调单个跖屈肌力量的关键。此外，这些数据表明，随着年龄的增长，跟腱组织运动更加均匀，这可能是由跟腱束间粘连引起的。本研究的总体假设是，老年人跟腱内更大的腱束粘连会导致更均匀的跟腱变形，从而降低单个跖屈肌的最佳协调能力，从而影响跖屈肌的力量，从而影响步态表现。该方法利用成像生物力学和计算建模的新进展来研究跟腱力学和功能的年龄相关变化，并预测老年人行走能力的影响。以下是具体目标。目的1将使用先进的超声弹性成像方法来确定年龄的增长是否伴随着更大的跟腱张力均匀性，这是一个潜在的重要因素，可以考虑作为与年龄相关的行走能力限制的机制。目的2将使用超声弹性成像和肌肉电刺激的创新组合来揭示老年人跟腱内的大筋束粘连是否在跟腱的深层和浅层部分之间带来更均匀的变形。最后，Aims 3将把Aims 1和Aims 2的研究结果纳入肌肉驱动的前向动态模拟中，以预测老年人行走时跖屈肌功能的变化。本研究将首次探讨与年龄相关的局部跟腱应变分布的变化（目的1），其潜在机制（目的2），以及对老年人行走能力的影响（目的3）。这些目标的成功完成将有助于加强对与年龄相关的行走能力下降的科学理解，并指出更合适的治疗方法可以延长老年人的独立性，从而提高老年人的生活质量。

DESCRIPTION (provided by applicant): The pervasive decline in ankle power generation, even in otherwise healthy older adults, plays a central role in the deterioration of walking abilit with age. However, muscle strengthening alone generally fails to significantly improve the walking ability of older adults, suggesting that factors other than sarcopenia contribute to the decline in plantarflexor power with age. I propose to investigate the relevance of age-related changes in Achilles tendon mechanics and their implications for walking ability in older adults. The premise of this study is that the aging Achilles tendon exhibits altered in vivo behavior that greatly diminishes the ability to optimally coordinate the ankle plantarflexor muscles during the push-off phase of gait. Preliminary data suggest that the superficial and deep Achilles tendon fascicles exhibit distinctly different displacements, likely due to inter- fascicle sliding, which ay be critical for optimally coordinating the forces from the individual plantarflexor muscles. Moreover, these data show evidence that advancing age brings much more uniform tendon tissue motion, which may arise from inter-fascicle adhesions within the Achilles tendon. The overall hypothesis of this research is that greater fascicle adhesions within the Achilles tendon of older adults bring more uniform tendon deformations that reduce the capacity for optimally coordinating the individual plantarflexor muscles, thereby compromising plantarflexor power and thus gait performance. The approach utilizes novel advances in imaging biomechanics and computational modeling to investigate age-related changes in Achilles tendon mechanics and function, and to predict the ramifications for walking ability in older adults. Following are the specific aims. Aim 1 will use an advanced ultrasound elastography approach to determine if advancing age is accompanied by greater Achilles tendon strain uniformity, a potentially important factor to consider as a mechanism for age- related walking ability limitations. Aim 2 will use an innovative combination of ultrasound elastography and electrical muscle stimulation to reveal if greater fascicle adhesions within the Achilles tendon of older adults bring more uniform deformations between the deep and superficial portions of the tendon. Finally, Aim 3 will incorporate the findings from Aims 1 and 2 into muscle-actuated forward dynamic simulations to predict changes in plantarflexor function during walking in older adults. This research will investigate for the first time the age-related changes in localized Achilles tendon strain distributions (Aim 1), their underlying mechanisms (Aim 2), and the ramifications for walking ability in older adults (Aim 3). Successful completion of these aims will contribute to an enhanced scientific understanding of age-related declines in walking ability and point to specific opportunities where more appropriate therapies could prolong independence and thus enhance quality of life in older adults.