Block periodization concentrates training stimulus on one or two qualities at a time — accumulation, transmutation, realization — in 2-6 week blocks.
Mechanism — Concentrated stimulus produces faster adaptation than dilute concurrent training. Each block builds on the prior — base capacity, transformed into specific power, realized in competition or testing.
Use case — Strength, endurance, or hybrid athletes with peak-event focus. Better than linear periodization for trained athletes with limited time.
Caveats — Block focus means temporarily neglecting other qualities. Schedule retention work so you don't lose what you've built. Doesn't fit all populations — beginners often respond best to undulating concurrent training.