The man with some of the biggest arms around was John McWilliams from Kenton, Ohio. While many bodybuilders used to inflate their measurements, he had an open challenge to anyone who could measure his arm at less than 19-1/2 inches… and the money was always safe. In case you are wondering about the “secrets” to his arm development, they were hard training, correct nutrition and proper recovery ~ along with more than a little bit of help from mother nature, of course.