Kelly Starrett is a CrossFit trainer, physical therapist, author, and speaker. Wikipedia
Source: Kelly Starrett recommended this book in the "Tools of Titans" book.
Source: "Brilliant, brilliant, brilliant." - Kelly Starrett
Source: "[Kelly Starrett] is a legitimate fantasy and sci-fi nerd. He knows [this book] inside and out." - Tim Ferriss
Source: "Fantastic." - Kelly Starrett