system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Do our bodies get used to certain exercises, and so start burning fewer calories when we do them?

My instructor at the gym says that I need to keep changing my routine, as my body will plateau and burn fewer calories even doing the same work.

Why is this? Surely lifting a certain weight a certain number of times will always require the same amount of energy?

Or is my body just getting more efficient at it?
gpt
Your body will realign and reallocate muscle fibers as you tear them and they get repaired. So, technically, yes - you will get better at doing one particular motion efficiently at one particular weight and rep range. In reality, though, you will likely up the weight as you build muscle and get better at the exercise, and so will end up burning MORE calories moving a higher weight and doing the same exercise.

Lift heavy, lift compound.