The principle in one sentence
Progressive overload means gradually increasing the demand you place on a muscle so adaptation continues. Everything else — periodisation, splits, rep schemes — is a delivery mechanism for that one idea.
Five ways to overload that aren't 'add weight'
Add a rep at the same load. Add a set. Slow the lowering phase. Shorten rest between sets. Improve range of motion. Each one increases demand without touching the bar.
This matters because linear weight increases stop working within months for most lifters, while these levers keep working for years.
How fast is too fast
If your form degrades, or a session leaves you unable to train two days later, you've overloaded faster than you can recover. Recovery capacity — sleep, food, stress — is the ceiling on progression rate.
Track it or lose it
You cannot progressively overload what you don't measure. Logging sets and reps in Propal turns 'I think I'm getting stronger' into an estimated one-rep-max curve you can actually read.