There are three metabolic pathways that provide the energy for all human action. These “metabolic engines” are known as the phosphagen (or phosphocreatine) pathway, the glycolytic (or lactate) pathway and the oxidative (or aerobic) pathway. The first, the phosphagen, dominates the highest-powered activities, those that last less than about 10 seconds. The second pathway, the glycolytic, dominates moderate-powered activities, those that last up to several minutes. The third pathway, the oxidative, dominates low-powered activities, those that last in excess of several minutes.
Total fitness, the fitness that CrossFit promotes and develops, requires competency and training in each of these three pathways or engines. Balancing the effects of these three pathways largely determines the how and why of the metabolic conditioning or “cardio” that we do at CrossFit.
Favoring one or two to the exclusion of the others and not recognizing the impact of excessive training in the oxidative pathway are arguably the two most common faults in fitness training.
From "What is Fitness" written by @cfceo in 2002. Link in bio 👆🏼#crossfit @crossfittraining