The Science of Ki-Control
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Groundbreaking Science is the title of a book.
Groundbreaking Science was written by Son Gohan around 800 Age. This book gave a understanding of ki usage to the general public, thus opening up a worldwide interest in martial arts and fighting. Due to this book, Kuririn and Tenshinhan started up their own training schools as Turtle Hermit decided he was too old for the job.
Kuririn founded the New Turtle School. Having fought many battles alongside Saiyans and Namekians, he understood that Humans simply could not compare to aliens and developed techniques that revolved around working together. Even if they are unable to deal a killing blow to kill their opponent, they can still weaken them, and by combining their efforts with others, would be able to contend with far stronger enemies.
Tenshinhan on the other hand came to a different conclusion, believing that it was more important to develop aggressive attacks by controlling ki than it was to provide support. Having witnessed the Super Genki Dama that Son Goku used to defeat Kid Boo, he realized that it was possible for an individual to defeat even the strongest opponent by raising their battle power to the limits and gathering tremendous amounts of ki. As such, he developed techniques that revolved around strategically collecting ki and unleashing bursts of intense energy with precise timing.