Both Sanchin Kata and Tensho Kata are heishu gata (closed hand kata). Heishu gata refers to the constant state of tension maintained throughout the kata. Power is concentrated in the tanden and the muscles are relaxed only when the kata has completed.
Miyagi Chojun Sensei’s version
Higaonna Kanryo Sensei’s version
All other kata are kaishu gata (open hand kata). In kaishu gata, the muscles of the body remain open or relaxed allowing for quick and free flowing movements. You contract the muscles of the body and concentrate power in the tanden only at the point of execution of each technique.