How does lifting something heavy build muscle?
In: Biology
There are three major parts:
1. When you lift heavy stuff, you have to work hard. Your body doesn’t like working hard. So over time it grows muscle so you don’t have to work as hard when lifting things. Once you stop lifting things your body will get rid of the muscle since it’s just dead weight. (train this part by lifting heavy)
2. Same thing basically happens when lactic acid builds up in your muscles, it hurts. Your body doesn’t like pain so it makes bigger muscles to have more lactic acid capacity and less effort. Again, once you stop using those muscles it’s just dead weight and your body will get rid of them. (train this part by exercising for metabolic stress. So lighter weight but repetitions untill you really feel that burn)
3. As said by other, your muscles tear when lifting or exercising. When those muscles are repaired, the repairs make the muscle (fibers) slightly bigger every time. (train this part by stretching the muscles under load and doing good controlled ‘negative’ parts of the exercise.)
Muscles tear a little bit. Body then fixes muscle by repairing the tear but this time a little bit stronger.
ELI5:
Your body picks up a heavy thing repeatedly and muscles tear under the stress.
Your body recognizes that you now pick up that heavy thing repeatedly to stay alive, it dedicates resources to regrowing those muscles that were torn and build enough new ones to handle picking up that weight so you don’t die.
Repeat.
There are a few processes that make your strenght, one is the thickness of you motor units (your muscles) which respond to mechanical stress by growing thicker (classic hypertrophy training with 8-12 reps tries to maximise this).
The next is intermuscular coordination. That is essentially how well your body is able to coordinate your muscles during the exercise. That is something your brain just learns when lifting heavy things. Your brain is quite good at this, that also happens for running (experienced runners run more efficiently).
The last is intramuscular coordination. That is the ability of your muscle too recruit his muscle fibers in the most effective way to do the task. It is something your nervous system has to learn. That best works in lower rep ranges as you are forced to adapt to the high stress.
To put it simply, when you exhaust your muscles by doing anaerobic exercise (i.e lifting heavy objects at the gym), you cause damage to the muscle tissue and cause tears.
If you provide the body with good quality protein and enough calories, the body repairs this damage and applies some more proteins to the structure for good measure, which makes the muscle bigger.
This process is called Hypertrophy.
Makes lots of little tears in your muscles that then get repaired better than before. That’s why high reps with less weight works well too.
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