eli5 What happens to muscles when you stop exercising and is it hard to get them back?

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What happens to your muscles when you stop exercising? Do they automatically start shrinking when after a week of not going to the gym? If muscles are formed when torn fibers heal, how is it possible that they shrink again? The tears still occurred so how can they just shrink? Also is it harder to get those muscles again after you quit going to the gym?

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Anonymous 0 Comments

In order of your questions:
– Your body essentially eats them. Muscle fibers require a ton of resources to maintain, and your body is evolved for efficient use of scarce resources. If you don’t use them, your body gets rid of them.

– While it happens pretty quickly, a week or so after working out, provided you’ve been eating and sleeping, you won’t be noticeably weaker. A good rule of thumb is after about 2 weeks of not doing a lift, drop the weight by 10%.

– See the first bullet for the next two questions.

– Barring unusual circumstances, it’s easier to regain muscle than it was to get it in the first place.

Edit: To elaborate a bit on that first bullet, one pound of muscle takes, conservatively, about 140-150 calories per day to maintain. while that may not sound like a lot, in the environment our species evolved in, even 10 pounds of muscles is a good half of what you could expect to scavenge. For comparison, a pound of fat takes about 40-50 calories per day. To give you a sense of what that entails, I’m 6’4 at about 205lb, in the 85th-95th percentile by most strength metrics, though nowhere close to anyone who does it professionally. My base metabolic rate – that is, the amount I’d need to maintain weight in a coma, is well over 2,000 calories. To gain weight at a reasonable pace, with a caloric surplus of ~200-300 calories/day, I need to eat around 3200 calories per day. That is an *insane* amount of food for a species that evolved in subsistence conditions (that many people still live under), and something that takes serious effort (and money) to maintain in a healthy way.

TLDR muscle is crazy expensive, energy-wise.

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