The author has found it very helpful to try do as many things with the left hand as is usually done with the right. Opening doors (the ones with the door-knobs being an ideal hand turning exercise), lacing your shoes, carrying parcels, tieing your necktie, buttoning your shirt, feeding yourself at the table, and writing, have been found to be excellent exercises for the left hand.
—Gene Krupa’s Drum Method (1938)