Lower Extremity Muscle Power and Function in the Elderly

描述(由申请人提供)：本提案是针对RO1 AG018844的竞争性更新，该项目已进入资助的第三个年头，并响应PAS-03-122“老年脆弱：病理生理学和干预措施”而提交。这项研究的重点是检验肌肉力量训练干预的生理和功能效果，并与传统的渐进式阻力训练进行比较，这些训练以社区为基础，对行动能力中等受限的老年男女进行干预。在目前的项目期间，我们已经成功地证明，在老年社区居住的男性和女性中，下肢功率峰值与功能限制和自我报告的残疾密切相关。我们建议通过检查导致年龄和性别相关的峰值肌肉力量下降的生理机制来扩展我们之前的发现。为了补充我们现有的关于骨骼肌纤维收缩特性的数据，我们将评估随着年龄的增长神经对肌肉力量产生的贡献。我们将检验这一假设，即骨骼肌单纤维收缩特性(即单纤维力量、缩短速度、比力)、神经因素(即肌肉间协调模式、中枢激活比率/和运动单位控制特性)和下肢力量将随着年龄的增长和行动不便的风险程度而降低，女性的这些差异将比男性减弱。中年健康(40-55岁)、老年健康(70-85岁)和老年(70-85岁)有行动障碍风险的男性和女性将在受控条件下进行研究(研究1)。此外，鉴于我们最近的观察发现，在相对较低的外力(例如：40%1 RM)，并与步态速度最密切相关的老年人的下肢最大速度的差异，我们建议在行动不便的风险个人进行高速低阻力运动训练的随机对照试验，以测试这样的假设：针对低外力和最大自愿速度进行的短期阻力训练干预将导致行动不便的显著减少，这从400米步行过程中步态速度的改善在行动不便的风险的老年个人中得到证明(SPPB Score&lt；_9，70-85岁)(研究2)。这些研究的结果将对了解虚弱老年人身体残疾的近端决定因素和设计旨在改善行动能力的干预策略具有重要意义。

DESCRIPTION (provided by applicant): This proposal is for the competitive renewal of RO1 AG018844, which is in its third year of funding and is submitted in response to PAS-03-122 "Frailty in Old Age: Pathophysiology and Interventions". The focus of this research has been to examine the physiologic and functional effects of a muscle power training intervention in comparison to traditional progressive resistance training in a community-based group of elderly men and women with moderate mobility limitations. During the current project period, we have successfully demonstrated that peak lower extremity power is closely associated with functional limitations and self-reported disability in older community dwelling men and women. We propose to extend our previous findings by examining the physiological mechanisms that contribute to the age and gender-related declines in peak muscle power. To compliment our existing data on skeletal muscle fiber contractile properties, we will assess the neural contributions to the generation of muscle power with advancing age. We will test the hypothesis that skeletal muscle single fiber contractile properties (i.e. single fiber power, shortening velocity, specific force), neural factors (i.e. intermuscular coordination patterns, central activation ratios/and motor unit control properties) and lower extremity power will be reduced with advancing age and degree of risk for mobility disability, and these differences will be attenuated in women compared to men. Middle-aged healthy (40-55 yrs.), older healthy (70-85 yrs), and older (70-85 yrs) men and women at risk for mobility disability will be studied under controlled conditions (Study 1). In addition, in light of our recent observations that differences in lower extremity maximal velocity occur at relatively low external forces (eg: 40% 1 RM) and are most closely associated with gait velocity in older individuals, we propose conducting a randomized controlled trial of high velocity low resistance exercise training in individuals at risk for mobility disability to test the hypothesis that a short-term resistance training intervention performed against a low external force and at maximum voluntary velocity will induce significant reductions in mobility disability as evidenced by improvements in gait velocity during performance of a 400 M walk in older individuals at risk for mobility disability (SPPB score <_9, 70 - 85 yrs) (Study 2). The results of these studies will have important implications in understanding the proximal determinants of physical disability in the frail elderly and in designing intervention strategies targeted at improving mobility.