Last year I started to get in shape. I am 6 foot and started out at 148lb and got up to 169lb. I was SUPER skinny, so I decided to become an avid gym goer for the better part of six months. I was not big by any means, but definitely looked better. In January I went on vacation, came back took two months off to focus on career development. In February I broke my hand and completely after that I forgot about the gym during my healing process. I’m not longer lean. My muscles aren’t pronounced and I just look average.
Now Im at 160 pounds and haven’t been to the gym since the last week of December. I know I don’t eat no where near as much as I used to which plays a factor but what cases the muscle to shrink?
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If you don’t use it you lose it. Simple as that
Muscles use up a lot of energy just by existing. If your body doesn’t need the muscles it won’t hold on to them. If you don’t stress the muscles enough to where your body thinks it needs to hold onto it, you lose it. Simples.
Muscle is expensive for your body to maintain. If you’re not using it your body will get rid of it.
Good news is it’ll also come back quicker.
It’s super simple.
Muscles grow in accordance to how you train them.
You keep them by keeping active and eating at least at maintenance.
You lose them from inactivity, you lose them even faster with eating less.
If you want them back, eat a bit above maintenance, train at least 3x a week, keep your protein up and rest well and they’ll be back sooner than you imagine.
There’s two causes. One is the muscles being broken down by your body. Your body needs to spend more energy to maintain muscles than fat so it prefers to turn muscle into fat if you aren’t in need of it.
The second type is the loss of temporary swelling caused by regular activity. Regular exercise and an increase of food intake can cause muscles to store more glycogen, making them bigger. There’s also inflammation from muscle damage. Both of these cause muscles to swell quickly when you start exercising regularly and also go down quickly when you stop. These two are separate from the ‘pump’ you get immediately after exercising, which is from increased blood flow to the muscle.
The good news is the second part can be gained back almost right away, since it’s just swelling. And muscle loss will be minimal after only four months of inactivity, and the muscles you did lose should come back quickly if you get back into it. Keep in mind the loss in strength might be greater than the loss in muscle as your body ‘forgets’ how to perform the movements, and that also comes back quickly.
Muscle is costly for the body to keep. It will only build or keep additional muscle if it “thinks” it needs it. Training in the gym makes the body “think” it needs extra muscle. Without training, your body no longer thinks it needs the extra muscle. Your body only keeps the amount of muscle it “thinks” it needs. It makes this choice based upon our activity.
When you lift weights, you’re giving your muscles a reason to grow. You’re breaking them down a bit, and your body rebuilds them stronger. That also means your body uses more calories and keeps a higher energy demand.
But when you stop going to the gym and stop eating enough, your body goes, “Well, I guess we don’t need all this extra muscle,” and it starts breaking it down to conserve energy. This is called muscle atrophy.
It happens faster if you’re not eating enough protein or calories
It takes a ton of calories to maintain muscles, even when you’re not using them. A muscular person’s muscles will burn hundreds of calories just keeping themselves alive on a day where the person sits on the couch all day.
Of course “hundreds of calories a day maintaining something unnecessary” is a big red flag for evolutionnatural selection, so that’s where we got “use it or lose it”. Our bodies are very good at keeping absolutely the *smallest” amount of muscle needed to do what we need to do. Muscles that don’t get used are quickly lost to save energy.
Working out is the reverse – if your muscles are often inadequate for things you try and move, then it goes “ok we must need more” and it adds some. But as soon as they’re not needed in your life any more your body goes “ok we can stop burning so much precious food maintaining these then.”
I herniated a disc in my back and was out of regular routine for 6weeks. It’s taking a while to build up my strength again, it is so disheartening
Your body is very adaptive. It’s part of what makes us successful as a species.
When you went to the gym, your body adapted to the activity by building muscle. Then you loaded on more weight/reps, so it adapted again by building more muscle. Rinse and repeat.
When you stopped, it adapted yet again to your new lifestyle. You no longer needed those muscles, so your body let them go.
If you don’t use it, your body won’t waste the energy to maintain it.
Your body uses glucose as a source of energy, but sometimes you have a surplus of glucose. Your body senses and releases insulin. Insulin allows your body to store the excess glucose as glycogen for later use. When you have a decreased level of glucose, your body releases glucagon, which is the opposite of insulin. Instead of storing glucose, glucagon breaks down tissue and uses the products to create new glucose. It breaks down your muscle and fat to create new glucose. As long as you’re fueling your body, this wont happen.
Not a biologist so this could be totally wrong but a principle that always made sense to me is that your cells accumulate internal junk like broken organelles or faulty structures all the time just due to entropy. A large muscle cell that doesn’t get used would accumulate a lot of junk that affects its core function and cost a lot of energy to maintain – think of it like a large bedroom that never gets clesned. Your body shrinks muscle cells to prevent this mess from getting out of control if you’re not using the cell regularly. Exercise causes that junk to break down (like clearing everything in the room) and the healing/recovery period post-exercise is when your body fills all the new space with useful structures that make your muscles cells stronger. So if you keep exercising the cell doesn’t need to shrink, in fact it gets made bigger to facilitate the new useful structures.
Muscle produces myostatin. Myostatin reverses the muscle growth process.
The body is always growing or shrinking. It’s an attempt to maximize efficiency. Why have muscle you don’t need, it just uses up resources.
First thing to go and your body compiles on fat 😭
Better question is why do they get bigger with exercise? I’m sure there are some but I can’t think of any other animals that exhibit hypertrophy of muscles due to exercise.
People have covered the reasons why your body does, which are basically efficiency: if you don’t need to feed it, your body won’t keep it.
The good news for muscle is even though you lose muscle mass when you take a break from strength training, training induces changes to your muscles that ARE permanent.
(Dear ELI5 redditor, this is ELI5 so I’m not going to be going complicate things for the OP by going into specifics of skeletal/cardiac/striated/smooth muscle tissue, this question is about skeletal muscle so you can take “muscle cell” to mean “skeletal (striated) muscle cell”).
Muscle cells aren’t like other cells in that you ALWAYS have basically the same NUMBER of cells throughout your entire life, give or take a few cells here and there. You don’t grow NEW muscle cells when you train, the individual cells get bigger by adding more of two kinds of protein to the fibres: myosin, the motor protein which is what actual contracts when you flex, and actin, which is like a rope the myosin pulls on to contract the whole muscle. These proteins are what your body recycles when it doesn’t need them, or more specifically it doesn’t expend energy and nutrients to replace them as they degrade if doesn’t need to.
But your muscles cells are also different in another way: they don’t have a single nucleus. They have MULTIPLE nuclei, and they grow new nuclei to adapt to training. More nuclei is where your DNA is stored, and where all the enzymes go to get instructions to make more proteins, so the more nuclei you have, the more enzymes and the more protein you can produce. More nuclei in the muscle cell means the cell can keep up with maintaining a higher level of protein needed when you’re training. So as your muscles get bigger, they grow extra nuclei to keep up with the demand to keep that muscle functioning.
But unlike the protein, those extra nuclei DON’T go away when you stop training. They’re basically permanent. So when you get back to training, your muscles are already primed to produce protein at the peak rate you were training at before. You have those extra nuclei protein factories just ready to go. So it’s a lot easier and faster to get back to where you were before.
Where you do want to be careful is, of course, injury. Again, you don’t grow new muscle cells. So if you have an injury that kills or significantly damages a cell, that cell is gone for good, which is why major tears are a permanent injury that you’ll never fully recover from.
Which is also why training in cycles (I.e. 12 weeks training 4 weeks break as an example) is the most effective way to train. The impulse when you hit a plateau might be to push harder to get through, but you plateau because the rate at which your muscle cells can make protein is at or just below the rate needed just to compensate for the training and they need some time to produce more nuclei, but they don’t have enough nutrients or time to do that. So you either need to try and eat more or train a bit less and let them catch up. Training harder just means the cells will fail first and you’ll start losing protein and risking injury.
So the idea is to train until you hit a plateau, then keep then intensity the same for a week or two while increasing eating more. Then take a break from training for a couple of weeks to let your body recover and grow those new nuclei (because your body will keep adapting for a week or two after your stop), then come back at a lower intensity and you can usually push through that plateau.
Up until you reach the limits of what you can achieve with the available time, genetics and your food budget. Especially that last because it gets really expensive once you’re eating a couple of kgs of meat a day to keep your weight up.