The CrossFit prescription is “constantly varied, high-intensity, functional movement.” Functional movements are universal motor recruitment patterns; they are performed in a wave of contraction from core to extremity; and they are compound movements—i.e., they are multi-joint. Functional fitness consists of training functional movements that mimic motor recruitment patterns that are found in everyday life. Others are somewhat unique to the gym.
Squatting is standing from a seated position; deadlifting is picking any object off the ground. They are both functional movements. Leg extension and leg curl both have no equivalent in nature and are in turn nonfunctional movements. The bulk of isolation movements are non-functional movements. By contrast the compound or multi-joint movements are functional. Natural movement typically involves the movement of multiple joints for every activity. The importance of functional movements is primarily two-fold. First of all the functional movements are mechanically sound and therefore safe, and secondly they are the movements that elicit a high neuroendocrine response.