Concentrated loading in sequence
Block periodization, developed and championed by sport scientist Vladimir Issurin, organizes training into focused blocks that each concentrate on a small number of training qualities rather than developing everything at once. The classic sequence runs accumulation, then intensification, then realization, with each block building on the residual fitness left by the one before.
The accumulation block raises work capacity and the foundational quality; intensification shifts toward heavier, more specific loading; realization sharpens and expresses the trained quality near competition.
Why concentrate rather than mix
The rationale is that a concentrated stimulus drives a stronger adaptation in the targeted quality than diluting attention across many goals simultaneously, which can be useful for advanced athletes who no longer respond to mixed training. It relies on the idea that adaptations persist for a time after a block ends, so qualities can be developed sequentially and still overlap.
Where it fits
Block models suit experienced athletes with clear competition targets more than novices, who progress fine on simpler plans. Implementation varies by sport and individual. This is general educational information about periodization, not medical advice.