Idiotic. Doing suburi or other 'hitting' air warmup more than necessary to increase circulation and to warmup the arms is pointless. 20 of oosuburi, men suburi, and hayasuburi each is enough. Doing more and the warmup becomes fatiguing (not the objective of a warmup) and turns into a aerobic exercise. I know a magical alternative aerobic exercise that is much more natural to the human body: Jogging. Form can't be improved by swinging your shinai madly in the air. Form is impoved by hitting your opponent.