This document provides an overview of the foundations of CrossFit. It describes CrossFit as a core strength and conditioning program aimed at improving functional fitness across 10 domains. The CrossFit methodology focuses on constantly varied, high-intensity, functional movements, as well as cross-training and developing power. CrossFit has proven effective for diverse populations from elite athletes to sedentary individuals. The document argues that compound, high-intensity exercise is more effective for fitness than isolation exercises and extended moderate cardio.