US Patent 4,175,446
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
The number of steps taken while walking are counted by straining a fatigue life gauge to change its electrical resistance each time the device is stepped on by a subject. The change in resistance of the fatigue life gauge is measured to ascertain the approximate number of steps taken.
Crowninshield, Roy D. and Branch, Andrew J. Step counting device and method. US Patent 4,175,446 filed April 26, 1978 and issued November 27, 1979. https://ir.uiowa.edu/patents/17