How the body actually works under training stress. The four energy systems, Zone 2, aerobic base development, and why you'll bonk on Event 3 if you go out too fast.
Your body runs on four distinct energy systems — and most training programs only develop one or two of them. Here is what each system does, when it fires, and why the program trains all four concurrently.
Zone 2 training is not supplementary cardio. It is the foundation that makes every hard session recoverable, every conditioning piece sustainable, and every energy system more efficient.
The bonk is not a mental failure. It is a biochemical event — entirely predictable and entirely preventable. Here is exactly what happens in your body when you go out too hard, and how the program is built to stop it.