Book excerpt: It has been said that a successful martial artist doesn't need size or strength, because "it's all in the technique." It has also been said that the power of a martial artist seems to increase quickly with weight, and the best lightweight fighter in the world will be defeated every time by an unranked heavyweight in a bar brawl. So is it size and physical strength that matters, or is it experience and dedication to correct technique? This book explores the science behind power in the martial arts. Once we understand the principles of physics that apply to balance, body mass in motion, inertia, direction, rotational speed, friction, torque, impulse, and kinetic energy, the need to memorize hundreds of martial arts techniques vanishes. The principles of physics apply to all people at all times regardless of which martial art we study; regardless of whether we are standing, sitting, kneeling, prone, or supine; whether we are big or small, strong or weak. Physics gives us options. Making physics our ally allows us to maximize our power, speed, and endurance and take advantage of whatever position we happen to find ourselves in. This book is supplemented by hundreds of photos, detailed glossaries, summary and review sections, and even quizzes to test yourself on what you've learned and help you gain an edge on an adversary.