https://www.facebook.com/japanesejapan/posts/1863730073651168
Nakamura Sensei on Choosing a Sword. When he wrote Tameshigiri no Shinzui in 1980 (now translated as The Spirit of the Sword) he lamented that by his estimation, over 70% of the practitioners of Iaido and Battodo in Japan were using swords that were inappropriately balanced for their physique and, as a result, their technique was inevitably distorted and the road to kikentaiichi cut off. He reiterated this in his later books.
Enkeisen. One of the key principles of Nakamura ryu, enkeisen (the full circular trajectory of the sword swing) is key to understanding what constitutes balance in a blade. This movement requires great strength in the core and lower limbs, great elasticity and range of motion in the upper limb and an integration of the two through the engaging of the abdominal ‘brain’ or hara.