The Isshin-ryu style was developed by Tatsuo Shimabuku. Shimabuku was a student of Chojun Miyagi (founder of Goju-ryu Karate-do), Choki Motobu (Motobu-ryu Karate-jitsu), and Chotoku Kyan (Shorin-ryu). Kyan was particularly small even by Okinawan standards, so he had modified the traditional kata Chinto with specialized movements for use against larger opponents. Shimabuku was on the small side of average for an Okinawan (about 5' 4", roughly 135 pounds). However, he had found himself in the Phillipines training Japanese military how to fight against their larger American opponents. (The "official" story, in a letter from Angi Uezu, Shimabuku's son-in-law, is that Shimabuku was in the Phillipines as a geisha – by which I assume Uezu meant entertainer – and that he "loved" Americans.)
The insights of his teacher Kyan were clearly invaluable in solving the American problem, and they are evident in Shimabuku's Isshin-ryu style, a style which truly favors small person's techniques for use against much larger opponents. Ironically, in the U.S., Isshin-ryu is more of a "big man's" system, owing to the large stature of the original pioneers, men like Steve Armstrong, Harry Smith, Harold Long.
This video mini-blog shows the use of a signature Isshin-ryu technique from the kata Kushanku.
