Lower Extremity Muscle Power and Function in the Elderly

描述（由申请人提供）：该提案是针对RO1 AG018844的竞争性更新，该项目已进入资助的第三年，是根据PAS-03-122“老年虚弱：病理生理学和干预”提交的。本研究的重点是检查肌肉力量训练干预的生理和功能影响，并将其与传统渐进式阻力训练进行比较，以社区为基础的老年男性和女性中度活动受限。在目前的项目期间，我们已经成功地证明，在社区居住的老年男性和女性中，下肢功率峰值与功能限制和自我报告的残疾密切相关。我们建议通过研究与年龄和性别相关的肌肉力量峰值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。我们将检验骨骼肌单纤维收缩特性（即单纤维收缩力、缩短速度、比力）、神经因素（即肌间协调模式、中枢激活比和运动单元控制特性）和下肢收缩力会随着年龄的增长和行动障碍风险程度的降低而降低的假设，并且这些差异在女性中会比男性减弱。在控制条件下研究中年健康（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（研究1）。此外，根据我们最近的观察，下肢最大速度的差异发生在相对较低的外力下(例如：40% (1 RM)，并且与老年人的步态速度最密切相关，我们建议在有行动障碍风险的个体中进行一项高速低阻力运动训练的随机对照试验，以验证一个假设，即在低外力和最大自主速度下进行短期阻力训练干预会显著减少行动障碍，这一假设得到了有行动障碍风险的老年人400米步行时步态速度的改善（SPPB评分）的证明< 9, 70 - 85岁)（研究2）。这些研究的结果将对理解体弱老年人身体残疾的近端决定因素和设计针对改善活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.