system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If exercising means you strain muscles to grow them, why does straining your back hurt it instead of making it stronger?
gpt
There is a fine line between exercising and straining. Sudden jolts of pressure, weird twisting, almost anything going wrong can cause damage to things like tendons, disks, etc.

If you work out carefully you do strengthen your back muscles instead of iinjuring them the same as your arm and leg muscles.