How Long Does It Take to Lose Muscle?

While not ideal, many of us have to pause our workout routines from time to time. Whether you’re stressed, sick, injured, going on vacation or just need a break, there are plenty of reasons to take time off from exercise.

But, no matter how badly you need the break, you may worry about losing all your hard-earned muscle before you’re ready to start training again.

If you don’t train at all, you may start losing muscle mass after 72 hours, says米歇尔·奥尔森, PhD, a professor of exercise science at Auburn University in Montgomery, Alabama. Even your heart, which is also a muscle, will show a decrease in the amount of blood it can pump per beat after 72 hours off from exercise.

You’ll notice the effects on your heart a lot sooner than your biceps or quads. “If you work out on Monday and miss three days, returning to a workout on Friday, you will feel a bit more breathless than typical, because less oxygenated blood is being sent out from the heart per beat,” Olson says. “It’s not training-breaking, but it can be noticeable.”

尽管您在72小时后开始失去肌肉质量，但直到3-4周未经训练就走了3-4周，您可能不会注意到任何损失。一small studyfound that trained men could take three weeks off from exercise without any noticeable muscle loss.

However, there are a few factors that determine how quickly you lose muscle mass, including:

The longer you’ve been lifting, and the more muscle you have, the better off you’ll be if you decide — or have — to pause your routine. “If you’re fit with developed muscles, you will still have a baseline of muscle that others will not have after a period of inactivity,” Olson says.

足够的蛋白质, in particular, is key for building and maintaining muscle mass. If you skimp on it, your body won’t have enough amino acids (the building blocks of protein) to keep up with the constant breakdown and rebuilding of cells (muscle, red blood, hormones, etc.) that goes on all day, every day. Eventually, your body pulls from your muscle stores to get the amino acids it needs to keep your other cells and tissues functioning. The result? Muscle loss.

例如，在一项研究，对中度活跃的老年妇女久坐不动，她们吃了低蛋白饮食（每天每公斤体重为1.47克蛋白质），大约在9周后损失了其肌肉质量的14％。（但是，值得一提recommended for older adults）

因此，即使您不训练，也需要确保获得足够的蛋白质以防止肌肉损失。

蛋白质需要从一个人到另一个人的不同，但是作为一般指南，International Society of Sports Nutritionsuggests active people aim for an overall daily protein intake between 1.4–2 grams per kilogram of body weight (older adults may need to aim for the higher end of the spectrum). To put that in numbers, a 150-pound active person needs roughly 95–136 grams of protein per day.

Many age-related changes can make it harder to build and hold onto muscle. One of those changes relates to the nervous system.

随着年龄的增长，我们开始失去运动神经元。研究表明60-70岁之间的急剧下降。运动神经元从脊髓传递脉冲，告诉我们的肌肉收缩。奥尔森说，当您失去运动神经元时，很难募集肌肉纤维。如果你不能recruit muscle fibers，纤维不会崩溃并重建以增强更大，更强。

Strength training可以帮助将这些变化转化为神经系统以及其他与年龄相关的变化 - 但是一旦您停止训练，好处就会逐渐消失。

在肌肉方面，雄性有轻微的优势。奥尔森说：“男性具有更多天然睾丸激素，这是肌肉组织发育和维持的代谢。”（合成代谢是指从较小分子中构建较大分子的过程，例如用氨基酸构建蛋白质。）

一旦停止训练取决于不同的因素，您会失去肌肉的速度，但是总的来说，您会在3-4周内注意到损失。

If you have to cut back on exercise for whatever reason, and you don’t want to lose any hard-earned muscle, you may be able to get away with doing only two strength workouts per week, according to Olson. Target every major muscle group (back, chest, shoulders, biceps, triceps, quads, hamstrings, glutes and calves), and do at least 1–2 sets of 8–12 reps per exercise.

但是，即使您无法（或不想）训练几个星期，一旦您重新启动例行，就不必回到Square One。只要您一直在训练直到休息直到休息，就应该能够重建肌肉和力量很快。

无论您是要运行第一英里还是设置PR，制定计划都可以使您更快地到达那里。转到MapMyrun应用程序，点击“Training Plans”- 您将获得计划和指导技巧，以帮助您压碎它。