SARCOPENIA AND ERT IN POSTMENOPAUSAL WOMEN

描述（改编自申请人摘要）：人体骨骼肌力量被定义为由自主收缩（MVC）产生的最大力量，主要取决于肌肉1)大小和2)激活。肌肉大小可以通过使用磁共振成像（MRI）获得的无脂横截面积（CSA）来量化。肌肉力量和大小之间的关系是线性的，用比强度（MVC/CSA）表示。激活（定义为收缩信号从中枢神经系统传递到肌肉收缩机制的过程）可以使用无创神经生理学技术进行量化。功能（例如，体力活动水平）可以调节骨骼肌的大小和激活。最近有人建议雌激素替代疗法（ERT）保留或增强绝经后妇女的肌肉力量。这种保持强度的可能机制尚不清楚。在临床上，了解长期使用ERT是否会影响老年妇女肌肉减少症的发展是有用的。了解ERT是否必须考虑在内，对于设计老年妇女肌肉功能的未来研究也很重要。这个探索性项目的具体目的是：具体目的#1：比较ERT和对照组女性的肌肉力量、CSA、比强度和激活。计划研究长期ERT对背屈肌功能的影响，通过比较25名接受（5+）年和25名未接受（前5年）ERT的女性的背屈肌等距力量（MVC，牛顿）、无脂肪横截面积（cm2）、特定力量和激活。所有女性的年龄都在65-85岁之间，绝经10年以上。由于运动水平对测量的潜在影响，研究人员将选择具有相似运动水平的女性。他们将测试以下初步假设：假设1：与对照组相比，ERT组的肌肉力量和CSA更高。假设2：与对照组相比，ERT组的肌肉激活是相似的。具体目标#2：比较ERT和对照组女性的肌肉组成和体力活动水平的影响。研究者将在相同的ERT和对照组中分别定量背屈肌的肌肉和脂肪组织区室的CSA。然后，他们将验证假设#3A：与对照组相比，ERT组肌肉内脂肪含量会更低；假设#3B：无论雌激素水平如何，肌肉内脂肪含量与身体活动水平有关。

DESCRIPTION (Adapted from the Applicant's Abstract): Human skeletal muscle strength is defined as the maximal force generated by a voluntary contraction (MVC), and is largely determined by muscle 1) size, and 2) activation. Muscle size may be quantitated by its fat-free cross-sectional area (CSA), obtained using magnetic resonance imaging (MRI). The relationship between muscle strength and size is linear and is expressed as specific strength (MVC/CSA). Activation (defined as the process by which the signal to contract is transmitted from the CNS to the muscle's contractile machinery) can be quantitated using noninvasive neurophysiologic techniques. Function (e.g., physical activity level) may modulate both the size and activation of skeletal muscle. It has recently been suggested that estrogen replacement therapy (ERT) preserves or enhances muscle strength in post-menopausal women. The possible mechanism(s) of this preservation of strength is not known. Clinically, it would be useful to know whether long-term use of ERT influences the development of sarcopenia in elderly women. It is also important for the design of future studies of muscle function in elderly women to know whether ERT must be accounted for. The Specific Aims of this exploratory project are: Specific Aim #1: To compare muscle strength, CSA, specific strength and activation between ERT and control women. Plans are to investigate the effects of long-term ERT on dorsiflexor muscle function by comparing dorsiflexor muscle isometric strength (MVC, Newtons), fat-free cross-sectional area (cm2), specific strength and activation in 25 women on (5+) years and 25 women not on (in previous 5 years) ERT. All women will be 65-85 yrs old, 10+ yrs post-menopause. Because of the potential influence of activity level on the measures, the investigators will select women with similar levels of physical activity. They will test the following preliminary hypotheses: Hypothesis#1: Muscle strength and CSA will be higher in ERT compared to control women. Hypothesis #2: Muscle activation will be similar in ERT compared to control women. Specific Aim #2: To compare muscle composition and the influence of physical activity level in ERT and control women. The investigators will separately quantitate the CSA of the muscle and adipose tissue compartments of the dorsiflexor muscles in the same ERT and control groups. They will then test Hypotheses #3A: Intramuscular fat content will be lower in ERT compared to control and #3B: Intramuscular fat content will be related to physical activity level, regardless of estrogen status.