Ok in the system of Karate I studied Seisan is a power kata. The whole body remains tense thoughout the kata, every muscle. Breathing is done deep like you were doing a powerblock. Breathing on strikes is very forcefull often completely emptying the lungs completely of air. The main concept in this kata is dynamic tension and defensive breathing incase you get hit. It also puts emphasis on strengh. It is alot like a tiger style kata. Powerfull forcefull movements designed to break right though blocks and defenses. Kanku Dai and Kusanku are the oppisite of seisan they use relaxed often whipping and circle movement as opposed to seisan which is linear movement.