This is a great way to begin to warm up for a katana swordfight. Infinity circles work the wrists as well as the forearms and arms and shoulder. You can make them large and slow or tight and fast. They are a great way to begin to get a sense of control of a katana and the space it can cover around a body.  

What's involved: Triceps, shoulders. biceps, forearms, wrists. 

Powered by: Wrist, forearms, triceps, shoulder. 

Tip: Keep your grip tight but your writs relaxed. The best way to form an infinity diagram is to let the katana fall naturally, drawn by the earth's gravity and then flick it up lightly with the wrist so that you form two half loops which then form a complete infinity figure.