Skeletal Muscle Fatigue in Older Adults

老年人骨骼肌疲劳

• 批准号: 6522185
• 负责人: JANE A KENT
• 金额: $ 29.09万
• 依托单位: UNIVERSITY OF MASSACHUSETTS AMHERST
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-30 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6522185
• 关键词: adenosine triphosphate; age difference; aging; clinical research; creatine kinase; electromyography; fatigue; functional magnetic resonance imaging; human old age (65+); human subject; interview; muscle contraction; muscle metabolism; muscle strength; nuclear magnetic resonance spectroscopy; oxidative phosphorylation; reactive hyperemia; striated muscles; young adult human (21-34)

DESCRIPTION (provided by applicant): The overall goal is to determine the magnitude and mechanisms of age-related changes in muscle fatigue (decrease in maximal force-generating capacity, MVC). Clarification of the influence of age on fatigue has important implications for health and the maintenance of independent living in aging. We will study the ankle dorsiflexor and knee extensor muscles of healthy young (20-35 yrs) and older (70-85 yrs) adults. Muscle Metabolism and Perfusion (Years 1-2). ATP for muscular work is synthesized by 3 pathways: the creatine kinase (CK) reaction, oxidative phosphorylation and anaerobic glycolysis. Inadequate ATP supply can result in fatigue. Specific Aim I, Metabolic Capacity: To determine whether older muscle exhibits a decreased capacity to produce ATP. we will use magnetic resonance spectroscopy (MRS) to measure the capacities of these pathways. Hypotheses IA-C: Dorsiflexors will show A) similar CK kinetics, B) similar oxidative capacities, C) lower peak glycolytic rates in older adults. Hypotheses ID-F: Knee extensors will show D) similar CK kinetics, E) lower oxidative capacity in older, F) lower peak glycolytic rates in older adults. Specific Aim 2, Muscle Perfusion: To examine the relationships between dorsiflexor muscle strength, contraction intensity and blood flow occlusion, we will measure the reactive hyperemia of young and older adults using functional MR imaging during a series of isometric contractions. Hypothesis 2A: There will be no difference by age in the force (N) at the intersection of the bilinear relationship between the hyperemic response and absolute force. Hypothesis 2B: The intersection of the relationship between the hyperemic response and relative force will occur at a higher percentage of MVC. Muscle Fatigue (Years 3-5). Both muscle group and type of contraction may alter the outcome in studies of muscle fatigue in aging. Specific Aim 3, Muscle Group Specificity in Fatigue: To determine the impact of muscle and contraction type on the extent and mechanisms of fatigue in aging, we will compare dorsiflexor and knee extensor fatigue during maximal intermittent and maximal sustained isometric contractions We will measure activation, contractile function, metabolism and hyperemia. Hypothesis 3A: During the intermittent protocols, older will fatigue less and show less decrease in muscle pH. Hypothesis 3B: During the sustained protocols, older and young will fatigue similarly and have the same metabolic response. Hypothesis 3C: The magnitude of the age-based increase in fatigue resistance during the intermittent protocol will be greater in the dorsiflexors compared to the knee extensors. Specific Aim 4, Task Spec Specificity in Fatigue (Exploratory): In Years 4 and 5, we will 1) measure fatigue, activation and contractile function in the 2 muscle groups using isovelocity contractions, 2) use the Hill Model to investigate the role of contractile and series elastic properties in fatigue, and 3) develop methods to perform dynamic fatigue studies in the MRS system.

描述（由申请人提供）：总体目标是确定与年龄相关的肌肉疲劳变化的幅度和机制（最大力量产生能力的降低，MVC）。澄清年龄对疲劳的影响对健康和维持衰老的独立生活具有重要意义。我们将研究健康的年轻（20 - 35年）和年龄较大（70 - 85年）的脚踝背屈和膝盖伸肌肌肉。肌肉代谢和灌注（1 - 2年）。肌肉工作的ATP由3种途径合成：肌酸激酶（CK）反应，氧化磷酸化和厌氧性糖酵解。 ATP供应不足会导致疲劳。特定目的I，代谢能力：确定较老的肌肉是否表现出产生ATP的能力降低。我们将使用磁共振光谱（MRS）来测量这些途径的能力。假设IA-C：背屈将显示a）类似的CK动力学，b）类似的氧化能力，c）老年人中较低的峰糖酵解速率。假设ID-F：膝关节伸肌将显示d）类似的CK动力学，e）老年人较老的氧化能力较低，f）较低的峰糖酵解速率。特定的目标2，肌肉灌注：为了检查背屈肌肉强度，收缩强度和血液流动闭塞之间的关系，我们将在一系列等轴测收缩期间使用功能性MR成像来测量年轻和老年人的反应性充血。假设2a：在高血分反应和绝对力之间双线性关系的交集中，力（n）的年龄将没有差异。假设2b：高血分反应与相对力之间关系的相交将发生在MVC的较高百分比下。肌肉疲劳（3-5年）。肌肉群和收缩类型都可能改变衰老肌肉疲劳的结果。特定目的3，疲劳的肌肉群特异性：确定肌肉和收缩类型对衰老疲劳的程度和机制的影响，我们将比较后反射器和膝关节伸肌疲劳期间的最大间歇性和最大等量计量计量计量计量的疲劳，我们将衡量激活，收缩功能，代理和超级症。假设3a：在间歇方案期间，较老的疲劳将减少，并且肌肉pH的降低较少。假设3b：在持续的方案期间，年龄较大和年轻人会类似地疲劳，并且具有相同的代谢反应。假设3c：与膝关节伸肌相比，在间歇性方案中基于年龄的疲劳耐药性增加的幅度将更大。特定目标4，疲劳的任务规格特异性（探索性）：在第4和5年内，我们将使用异伏特式收缩来测量2个肌肉组的疲劳，激活和收缩功能，2）使用山丘模型研究收缩和串联弹性在疲劳中的作用，以及3）在MRS System中进行动态疲劳的方法。