Progressive overload is the simplest idea in strength training, and the easiest to apply badly.
The rule: your body only adapts to demands it hasn't fully met yet. So each week, one of these has to move:
- Load — more weight on the bar
- Volume — more total sets or reps
- Density — the same work in less rest time
Pick one knob, turn it, leave the others alone. Trying to push all three at once is how programs fall apart in week three.