Mechanics of the Aging Achilles tendon with implications for walking performance

描述（由申请人提供）：踝关节发电的普遍下降，即使在其他健康的老年人中，也在步行能力随年龄的恶化中起着核心作用。然而，单独的肌肉强化通常不能显著改善老年人的行走能力，这表明除肌肉减少症以外的因素导致跖屈肌力量随年龄下降。我建议调查的相关性与年龄有关的变化，跟腱力学和他们的影响，在老年人的行走能力。这项研究的前提是，老化的跟腱表现出改变的体内行为，大大降低了能力，以最佳的协调踝跖屈肌在推出阶段的步态。初步数据表明，浅跟腱和深跟腱束表现出明显不同的位移，可能是由于束间滑动，这对于最佳地协调来自个体跖屈肌的力可能是至关重要的。此外，这些数据表明，随着年龄的增长，肌腱组织的运动更加均匀，这可能是由于跟腱内的肌束间粘连引起的。本研究的总体假设是，老年人跟腱内更大的肌束粘连带来更均匀的肌腱变形，降低了最佳协调个体跖屈肌的能力，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。具体目标如下。目标1将使用先进的超声弹性成像方法来确定年龄增长是否伴随着更大的跟腱应变均匀性，这是一个潜在的重要因素，可作为与年龄相关的行走能力限制的机制。目标2将使用超声弹性成像和电肌肉刺激的创新组合，以揭示老年人跟腱内更大的肌束粘连是否会在肌腱的深部和浅表部分之间带来更均匀的变形。最后，目标3将把目标1和目标2的研究结果纳入肌肉驱动的向前动态模拟，以预测老年人步行过程中跖屈肌功能的变化。这项研究将首次调查局部跟腱应变分布（目标1）的年龄相关变化，其潜在机制（目标2）以及老年人行走能力的影响（目标3）。成功完成这些目标将有助于提高对与年龄相关的步行能力下降的科学理解，并指出更适当的治疗可以延长老年人的独立性，从而提高老年人的生活质量的具体机会。

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.