Body & HealthMental model
Your body only adapts to what it can't yet do.
Progressive overload is the core principle of all training: muscles, tendons and the cardiovascular system change only when the stimulus exceeds what they are used to. So increase weight, repetitions, distance or pace in small steps, usually by just a few percent at a time. The legend behind it: Milo of Croton carried a calf every day until it was a bull.
Useful: Doing the same workout for months maintains your fitness but doesn't improve it.
Source: en.wikipedia.org