Muscle Fatigue, Gait Alterations and Increased Energy Cost of Walking in Aging

项目摘要 保持活动能力是延长我们健康寿命的基础。流动性降低可能是由于 疲劳性，一个新的衡量指标，量化性能恶化和随之而来的增加， 感知的努力。老年人的肌肉疲劳（最大功率随活动而降低）， 在那些行动不便的程度，可能有助于更大的疲劳老化通过变化， 肌肉协调，导致步态力学改变和行走的更高代谢成本。我们的科学 提出肌肉疲劳作用的前提是建立在强有力的证据基础上，即老年人有更大的 在低负荷、高速度最大向心性收缩期间，主要运动肌肉的肌肉疲劳; 和更大的膝伸肌疲劳的反应，跑步机步行比年轻的成年人。然而，在这方面， 缺乏证据表明肌肉疲劳是如何复合年龄或损伤相关的肌肉无力， 步态神经力学，以及与步行成本和疲劳的联系。我们的总体目标是 通过量化神经力学效应和能量效应来理解疲劳性的新框架 肌肉疲劳对步态的影响，因此可以采取有效的干预措施来预防或逆转疲劳。 追求。我们的中心假设是，肌肉疲劳通过加剧与年龄相关的 通过改变步态的控制和协调（目标1）来改变步态力学和可变性（目标1 2），因此，肌肉疲劳需要更大的能量在老年人中行走（目标3）。为了验证这一 假设，将收集4组15名男性和15名女性的数据：久坐的年轻人（30-40岁）和 老年人（70-80岁）健康成人、行动不便的老年人（70-80岁）和活跃的老年人（70-80岁）。这 结合这些群体，我们可以评估年龄、体力活动和活动能力的独立影响 损伤和性别效应测试。所有的群体，除了活跃的老年人，将是相对久坐不动，类似于 美国一般人口。我们将使用新的生理和临床相关的30分钟跑步机 步行导致下肢肌肉疲劳，并通过步态力学措施量化反应， 变异性、肌电图和步行的能量消耗。基于模型的步行计算机仿真 代表这4组将有助于提供对步态的肌肉基础的机械理解 适应和后果的整个身体能量。建模和实验方法是 紧密结合，以确定个体肌肉如何促进疲劳引起的步态力学改变， 随着年龄和损伤，行走的能量消耗增加（目标2和3）。要解决的问题- 疲劳性及其对衰老中活动性的影响-解决了NIH和NIA的既定目标。项目成功将 通过弥合现有的知识差距，从肌肉无力和疲劳， 疲劳，目前阻止许多老年人实现最佳健康寿命。

PROJECT SUMMARY Maintaining mobility is fundamental to extending our healthspan. Reduced mobility may be driven by fatigability, a new metric that quantifies deterioration in performance and the accompanying increase in perceived effort. Muscle fatigue (decrease in maximal power with activity) in older adults, and to a greater degree in those with mobility impairments, could contribute to greater fatigability in aging through changes in muscle coordination, leading to altered gait mechanics and a higher metabolic cost of walking. Ourscientific premise for the proposed role of muscle fatigue is built on robust evidence that older adults have greater muscle fatigue in major locomotor muscles during low-load, high-velocity maximal concentric contractions; and greater knee extensor muscle fatigue in response to a treadmill walk than younger adults. However, evidence is lacking for how muscle fatigue compounds age- or impairment-related muscle weakness to alter gait neuromechanics, and the connections to cost of walking and fatigability. Our overall goal is to generate a new framework for understanding fatigability by quantifying the neuromechanical effects and energetic consequences of muscle fatigue on gait, so that efficacious interventions to prevent or reverse fatigability can be pursued. Our central hypothesis is that muscle fatigue contributes to fatigability by exacerbating age-related changes in gait mechanics and variability (Aim 1) through changes in the control and coordination of gait (Aim 2), such that with muscle fatigue greater energy is required for walking in older adults (Aim 3). To test this hypothesis, data will be gathered for 4 groups of 15 men and 15 women each: sedentary young (30-40 yr) and older (70-80) healthy adults, mobility-impaired older adults (70-80), and active older adults (70-80 yr). This combination of groups will allow us to evaluate the independent effects of age, physical activity and mobility impairment, and test for sex effects. All groups, except the active older, will be relatively sedentary, similar to the general US population. We will use our new, physiologically- and clinically-relevant 30 minute treadmill walk to cause lower-extremity muscle fatigue and quantify the response with measures of gait mechanics and variability, electromyography, and energy cost of walking. Computer simulations of walking based on models representing the 4 groups will help provide a mechanistic understanding of the muscular basis for the gait adaptations and consequences for whole body energetics. The modeling and experimental approaches are tightly integrated to identify how individual muscles contribute to fatigue-induced altered gait mechanics and increased energy cost of walking with age and impairment (Aim 2 & 3). The problem to be addressed- fatigability and its impact on mobility in aging- tackles stated goals of the NIH and NIA. Project success will have a significant impact by bridging an existing knowledge gap from muscle weakness and fatigue to the fatigability that currently prevents many older adults from achieving an optimal healthspan.