Atemi -- striking to the opponent's body -- is done with whole-body connectivity in aikijujutsu. Even though it looks like only the arm or leg is striking or kicking, in reality the power of the entire body is behind it, created by both alignment and the connection of internal tissues including tendon, ligaments, muscle and fascia.
Here are some examples of connected atemi and ate waza, demonstrated by Salahuddin Muhammad Sensei (Hontai Hakkei Ryu Aikijujutsu) at the Hakkeikan dojo in Philadelphia.