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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歲以后，你的肌肉以每十年約3-8%的速度減少。而一旦你到了60歲，肌肉會減少的更快。其后果遠比容貌上發生的變化要更嚴重。肌肉減少不僅僅表示你的肩膀變低，或你無法再取得少年時的運動成績。這些肌肉變化所暗含的意義比你新買的褲子還要大的多，其影響可以說是深遠的，他們決定了你余生的健康水平和活躍程度。
肌肉減少意味著你身體消耗卡路里的能力大大降低。如果你還像早年一樣攝入等量的卡路里，那么你的身體將會出現脂肪堆積。肌肉鍛煉需要大量的卡路里：就像有一大幫情緒高漲、熱情活躍的親戚來拜訪你，他們總是上竄下跳，四處亂跑。最后，他們肚子餓了，需要很多食物。
想像這些需要食物的客人一個接一個地離開，剩下的人于是躺在沙發上。這就好比你的肌肉變少、變軟。這些愜意的客人們并不需要那么多食物，但你仍然按照一大幫人的份，買了很多吃的。這就好比你像肌肉變少前一樣攝入等量的卡路里。慢慢地，你家的碗廚和冰箱里都塞滿了沒用完的食物。這就好比這些多余的卡路里堆積成了脂肪。
盡管你的體重沒變，但是你體重中肌肉所占比例變小，而脂肪所占比例變大。這是因為沒有足夠的肌肉，于是未消耗掉的卡路里堆積成了脂肪。
同時，肌力還關系到骨骼強度。相比鍛煉肌肉，女性更在意保持正常的骨密度和強度，因為醫療機構、社會和媒體己經將更多的目光聚焦在預防骨質疏松癥上。但是，當你的肌肉變軟，骨骼更容易變弱。那些強化肌肉的練習，對增強骨骼也有幫助。
變少的肌肉和退化的肌力，還表示你在晚年會出現行動不便的情況。能夠行動自如，是健康老年生活的關鍵之一。無論是能夠繼續執行健身房練習計劃、搬運雜物、清潔房子、起立、坐下，還是能夠靈活地進出浴室，這些都有助于你實現獨立生活。
最后，變少的肌肉對胰島素的反應會變得更遲鈍。肌肉組織需要消耗大量的葡萄糖或血糖，但這一過程需要荷爾蒙胰島素的參與，這樣一來血糖就會進入細胞。當肌肉對胰島素反應敏感時，糖份則不會進入細胞。在這種情況下，你患上2型糖尿病的風險較高，患心臟病、中風，又或者是阿爾茨海默病(老年癡呆癥）的風險也會隨之上升。
鍛煉肌肉
因此，肌肉鍛煉絕不僅僅是一項徒勞的練習。它能夠讓我們的身體保持健康、活力和獨力性，并使我們遠離疾病。最重要的是，你對自身肌肉和肌力的控制能力，將比你能想像到的更好。專家們己經意識到，肌肉減少不僅僅是老年化過程中無法抗拒的事實，還在很大程度上是由于缺乏鍛煉引起的。通過練習，有些人，甚至到了90多歲，還能夠表現出驚人的肌肉力量。而絕大多數的女性，無論年輕、成熟或年長，都比其它人群更需要預防肌肉減少所引起的嚴重后果。
當你上了年紀，那些手臂、腿部和身體其它部分動作所需的骨骼肌肉會發生一系列變化。肌肉變少；神經系統在刺激肌肉動作時，變的更遲鈍；肌肉內開始出現脂肪和結締組織；身體動作能用到的肌肉變少。
然而，值得重申的是：盡管激素水平會導致肌肉發生變化, 但是年紀變大并不是引起肌肉減少和肌力退化的惟一原因。以下是人體步入老年后，一些引發肌肉變少的因素。
缺乏鍛煉 我們的身體是需要運動的，而缺乏運動是導致肌肉變少的一個重要原因。研究工作己經表明，青年人長期臥床休息后，其肌肉量迅速減少，肌力水平急速下降。研究也發現，那些上了年紀、且運動較少的男性和女性人群，肌肉量更少，更易出現行動不便。相反地，短短幾個月的訓練活動，能顯著增強老年人的身體強度。即使是剛剛度過90歲生日的老弱人群，也能有辦法增加他們身體的肌肉數量和肌力水平。如果你在90多歲的時候還能鍛煉身體，改進肌肉的力量，那么，無論你現在是30多，還是50多，甚至是70多，都沒有理由懈��！
缺乏蛋白質 目前，蛋白質日攝入量-- 即人體每天所需量（RDA) -- 規定為0.8克每千克成人體重。因此，如果你的體重是130磅（59公斤），那么你每天所需的蛋白質為47克。我建議人體每天有30%的卡路里從無脂肪蛋白質中攝�。ㄊＯ�45%自復合碳、25%自優質脂肪）。 這個量比日攝入值略高，但是你可以加入“超級減肥王”計劃，鍛煉并增強肌肉。
目前，專家們發現，在許多老年人的日常飲食中，蛋白質攝入量不足，且原先成人體重0.8克/千克的標準可能低了。無論如何，我們的目標是減肥。如果你正在努力練出肌肉（和燃燒脂肪），那么攝入足量的蛋白質就很關鍵。由于受到體重和身體成分的影響，個體蛋白質的建議攝入量因人而異。如果你有任何健康問題，如腎病，那么你所需的蛋白質攝入量會受此影響，具體的攝入量可以向醫生進行咨詢。
激素變化 女性-- 如果你正在接受激素替代治療（HRT），你可能首先己經知道的是，過量的雌激素會導致脂肪量增加，而不是肌肉。與你的醫生共同檢查激素替代治療（HRT)中，雌激素和黃體酮的均衡情況，以確保可以開始實施練習計劃，即使這意味著你需要向私人教練進行咨詢。
