足, 腰, 刀
Ashi, Koshi, Katana.
This is the basis of Iaido movements. First is from the feet (ashi), then waist (koshi) finally the sword (katana).
The feet meaning foot works, begin with planting your foot(feet) firmly and stably on the surface. This also means to stabilise your lower body. As the waist is considered where your upper half of body is connected to the lower half, with a stabilised lower half, the force of movement should then transmit from the ground up the stable lower half to the waist. Movement starting from the waist will guide the force/strength up towards your arms and finally to the sword in your hands. All sword movements in this sequence will be well balanced and powerful.
Think of a large crane used for construction. If the base (feet) is not firmly planted to the ground, movement at the mid section and operator's cab (waist) and the weight being moved at the far end (katana) will cause the entire machine to fall over.
This is easier said than done....