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After 30, your muscle mass dwindles some 3-8 percent each decade. Once you hit 60, these losses accelerate even more quickly. The consequences are far more serious than a change in your appearance. Declining muscle mass doesn't simply mean your shoulders are less toned or that you can't achieve the same results in sports that you did as a teenager. These muscle changes have implications that are much bigger than your new pant size. The effects are serious and far-reaching. They determine how healthy and active you'll remain for the rest of your life.
Decreased muscle mass means you'll burn far fewer calories. If you take in the same amount that you did when you were younger, you'll start accumulating body fat. Your muscles require a lot of calories to maintain: Think of them as a bunch of high-strung, active family members visiting your home. They're always up, moving around. As a result, they're hungry and require a lot of food.
Imagine that these demanding visitors gradually leave, one by one, and the remaining folks start lying on the couch. This is like your muscles becoming smaller and weaker. These relaxed visitors don't need as much food, but you keep buying the same amount of groceries that you bought when you had a big group of active guests. This is like eating the same amount of calories you did when you had more muscle. Gradually, your cupboards and refrigerator overflow with unused food. This is like storing up fat from those unnecessary calories.
Even if your body weight stays the same, less of your weight is from muscle and more is from fat. That's because calories are stored (as fat) when there is less muscle to burn them. More fat equals less calorie-burning muscle. Internally, the extra fat increases your risk of diabetes, stroke and some cancers. Externally, your body shape changes as muscle morphs to fat. This means bigger jeans and fewer fitted tops.
Also, the strength of your muscles is related to the strength of your bones. Women are likely more focused on keeping their bones dense and strong than on maintaining their muscles, because the medical establishment, society and the media have put more focus on preventing osteoporosis. However, when your muscles are weak, your bones are more likely to be weak. Exercise that helps your muscles helps your bones, too.
Declining muscle mass and strength also mean you'll be less likely to get around in your later years. Being able to move freely is a crucial component of healthy aging. Whether it's continuing your workout schedule at the gym, carrying groceries, cleaning your home, getting in and out of a chair or stepping in and out of your shower, your ability to do these activities helps determine your independence.
Finally, shrinking muscles may grow less responsive to insulin. Your muscles are avid consumers of glucose, or blood sugar, but they need to use the hormone insulin so the blood sugar can enter their cells. When they become insulin resistant, the sugar can't enter. This puts you at greater risk for Type 2 diabetes, which in turn raises your risk of heart disease, stroke and, perhaps, Alzheimer's.
Maintaining Muscle
So, maintaining your muscles isn't just an exercise in vanity. It's about staying fit, vital, independent and free of disease. Best of all, you have a lot of control over your muscle mass and strength -- more than you realize. Experts have seen that declining muscle isn't just an unpreventable fact of aging. In large part it's due to lack of use. Still, even people in their 90s can show impressive strength gains with exercise. Most women -- whether young, boomers or seniors -- are in a prime position to prevent the serious consequences of muscle loss.
As you age, a number of changes occur in your skeletal muscles, which are the ones that move your arms, your legs and the rest of your body. You lose muscle mass -- you simply have less of the stuff. Your nervous system becomes less efficient at prompting your muscles to move. Fat and connective tissue start developing within your muscles, leaving less muscle tissue to contract to move your body.
However, it's worth repeating: Although hormonal processes cause some muscle changes over the course of your life, shrinking muscle mass and decreasing strength aren't caused by age alone. Here are some of the factors that contribute to declining muscles as you venture into your later years.
Lack of use.Your body is designed to move and lack of movement is a significant factor in muscle decline. Studies have shown that even young people's muscle mass and strength quickly deteriorate when they're confined to bed rest. And research has found that older men and women who are less active have less muscle mass and more disability. Conversely, training programs of just a few months in duration have been shown to significantly increase older people's strength. Even frail people who've already passed their 90th birthday can add muscle mass and strength. And if you can improve your muscles' capability deep into your 90s, there's no excuse for slacking off now whether you're 30-, 50- or 70-something!
Insufficient protein.The current RDA (Recommended Daily Allowance) for protein -- the amount that people are supposed to get each day -- is 0.8 grams per kilogram of body weight for adults. So if you weigh 130 pounds (59 kilograms), you need 47 grams of protein daily. I recommend that 30 percent of your daily calories come from lean protein (with 45 percent from complex carbs and 25 percent from good fats). This is a little higher than the RDA, but you will be exercising and building muscle as a part of the "Biggest Loser" plan.
Experts are discovering that many older people aren't getting enough protein in their diets and that the 0.8 grams per kilogram recommendation may not be enough in the first place. Whether or not your goal is weight loss, if you're trying to build muscle (and burn fat), it's crucial that your protein needs are being met. Individual protein recommendations vary per person, depending on weight and body composition. If you have any health conditions, such as kidney disease, that may affect your protein requirements, consult with your medical provider to determine your personal protein requirement.
Hormonal changes.Women -- if you're on hormone replacement therapy (HRT), you've probably learned firsthand that extra estrogen can cause a weight gain in fat, not muscle. Discuss the estrogen and progesterone balance of your HRT with your doctor and be sure to stay on top of your exercise routine, even if that means consulting a personal trainer to get you started.
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30岁以后，你的肌肉以每十年约3-8%的速度减少。而一旦你到了60岁，肌肉会减少的更快。其后果远比容貌上发生的变化要更严重。肌肉减少不仅仅表示你的肩膀变低，或你无法再取得少年时的运动成绩。这些肌肉变化所暗含的意义比你新买的裤子还要大的多，其影响可以说是深远的，他们决定了你余生的健康水平和活跃程度。
肌肉减少意味着你身体消耗卡路里的能力大大降低。如果你还像早年一样摄入等量的卡路里，那么你的身体将会出现脂肪堆积。肌肉锻炼需要大量的卡路里：就像有一大帮情绪高涨、热情活跃的亲戚来拜访你，他们总是上窜下跳，四处乱跑。最后，他们肚子饿了，需要很多食物。
想像这些需要食物的客人一个接一个地离开，剩下的人于是躺在沙发上。这就好比你的肌肉变少、变软。这些惬意的客人们并不需要那么多食物，但你仍然按照一大帮人的份，买了很多吃的。这就好比你像肌肉变少前一样摄入等量的卡路里。慢慢地，你家的碗厨和冰箱里都塞满了没用完的食物。这就好比这些多余的卡路里堆积成了脂肪。
尽管你的体重没变，但是你体重中肌肉所占比例变小，而脂肪所占比例变大。这是因为没有足够的肌肉，于是未消耗掉的卡路里堆积成了脂肪。
同时，肌力还关系到骨骼强度。相比锻炼肌肉，女性更在意保持正常的骨密度和强度，因为医疗机构、社会和媒体己经将更多的目光聚焦在预防骨质疏松症上。但是，当你的肌肉变软，骨骼更容易变弱。那些强化肌肉的练习，对增强骨骼也有帮助。
变少的肌肉和退化的肌力，还表示你在晚年会出现行动不便的情况。能够行动自如，是健康老年生活的关键之一。无论是能够继续执行健身房练习计划、搬运杂物、清洁房子、起立、坐下，还是能够灵活地进出浴室，这些都有助于你实现独立生活。
最后，变少的肌肉对胰岛素的反应会变得更迟钝。肌肉组织需要消耗大量的葡萄糖或血糖，但这一过程需要荷尔蒙胰岛素的参与，这样一来血糖就会进入细胞。当肌肉对胰岛素反应敏感时，糖份则不会进入细胞。在这种情况下，你患上2型糖尿病的风险较高，患心脏病、中风，又或者是阿尔茨海默病(老年痴呆症）的风险也会随之上升。
锻炼肌肉
因此，肌肉锻炼绝不仅仅是一项徒劳的练习。它能够让我们的身体保持健康、活力和独力性，并使我们远离疾病。最重要的是，你对自身肌肉和肌力的控制能力，将比你能想像到的更好。专家们己经意识到，肌肉减少不仅仅是老年化过程中无法抗拒的事实，还在很大程度上是由于缺乏锻炼引起的。通过练习，有些人，甚至到了90多岁，还能够表现出惊人的肌肉力量。而绝大多数的女性，无论年轻、成熟或年长，都比其它人群更需要预防肌肉减少所引起的严重后果。
当你上了年纪，那些手臂、腿部和身体其它部分动作所需的骨骼肌肉会发生一系列变化。肌肉变少；神经系统在刺激肌肉动作时，变的更迟钝；肌肉内开始出现脂肪和结缔组织；身体动作能用到的肌肉变少。
然而，值得重申的是：尽管激素水平会导致肌肉发生变化, 但是年纪变大并不是引起肌肉减少和肌力退化的惟一原因。以下是人体步入老年后，一些引发肌肉变少的因素。
缺乏锻炼我们的身体是需要运动的，而缺乏运动是导致肌肉变少的一个重要原因。研究工作己经表明，青年人长期卧床休息后，其肌肉量迅速减少，肌力水平急速下降。研究也发现，那些上了年纪、且运动较少的男性和女性人群，肌肉量更少，更易出现行动不便。相反地，短短几个月的训练活动，能显著增强老年人的身体强度。即使是刚刚度过90岁生日的老弱人群，也能有办法增加他们身体的肌肉数量和肌力水平。如果你在90多岁的时候还能锻炼身体，改进肌肉的力量，那么，无论你现在是30多，还是50多，甚至是70多，都没有理由懈怠！
缺乏蛋白质目前，蛋白质日摄入量-- 即人体每天所需量（RDA) -- 规定为0.8克每千克成人体重。因此，如果你的体重是130磅（59公斤），那么你每天所需的蛋白质为47克。我建议人体每天有30%的卡路里从无脂肪蛋白质中摄取（剩下45%自复合碳、25%自优质脂肪）。 这个量比日摄入值略高，但是你可以加入“超级减肥王”计划，锻炼并增强肌肉。
目前，专家们发现，在许多老年人的日常饮食中，蛋白质摄入量不足，且原先成人体重0.8克/千克的标准可能低了。无论如何，我们的目标是减肥。如果你正在努力练出肌肉（和燃烧脂肪），那么摄入足量的蛋白质就很关键。由于受到体重和身体成分的影响，个体蛋白质的建议摄入量因人而异。如果你有任何健康问题，如肾病，那么你所需的蛋白质摄入量会受此影响，具体的摄入量可以向医生进行咨询。
激素变化女性-- 如果你正在接受激素替代治疗（HRT），你可能首先己经知道的是，过量的雌激素会导致脂肪量增加，而不是肌肉。与你的医生共同检查激素替代治疗（HRT)中，雌激素和黄体酮的均衡情况，以确保可以开始实施练习计划，即使这意味着你需要向私人教练进行咨询。
