The post hardcore genre developed from the hardcore scene in the USA in the late 1970's. Post harcore is based on the same structure as hardcore but with a few added creations such as beatdowns, blast beats and breakdowns.
In post hardcore the breakdown is probably the most powerful part of the song because this is generally the heaviest part. In a breakdown the drums would slow down into half time or even slower and would play a pattern on the bass drum usually with a lot of doublewhich can be fast or slow which the guitarists would follow, the guitarists would follow the double bass patternplaying palm muted notes on the lower strings to make it really heavy. The vocals in a break down tend to go from a period of low screams to a period of higher screams which may be done by the one vocalist or going between two vocalists.
Some bands in this genre are
Here are some good post hardcore bands: I Killed The Prom Queen, Parkway Drive, As I Lay Dying, Norma Jean, Bleeding Through, Every Time I Die, Bring Me The Horizon, August Burns Red, All Shall Perish