physiology

The foundation of endurance fitness, built by running at a low intensity where the body primarily uses oxygen to burn fat for fuel.

"Without oxygen." High-intensity exercise where the body demands energy faster than oxygen can be delivered, producing lactate.

The state where the body's stored carbohydrate reserves run low, leading to fatigue and "bonking."

Lactate Threshold: The Key to Faster Running

Second Wind: When Running Gets Easier