Our body is phenomenal. To improve at something, all we need to do is prepare for it by practicing and increasing the load.
If you give enough rest to your body, it will adapt and improve so that you will be better next time!
When it comes to muscle activity, your body gets better at two things:
A muscle is made of fibers which you can contract. There are lots of fibers in a muscle like a bicep. If you don’t usually use them much, your brain did not bother creating strong pathways to
An exercise is a movement you will have to repeat to be better and better at it. The most famous exercise might be push-ups. If I say I did 4x12 push-ups, that means I did 4 series of 12 repetitions of push-ups.
To grow muscle, you will have to progressively increase the difficulty of the movement. This is most often done using weights.
Volume
Intensity
Rest
Execution
Progression
Drop sets
Gym equipment