VO2 max training comes down to matching the right interval structure to the athlete, the discipline, and the point in the training block. Long intervals, short intervals, micro-intervals, and variable-pace formats all stress the aerobic system differently, and each has a specific place in a triathlete's training. Below is a full breakdown of 15 VO2 max interval formats, how to execute them, why they work physiologically, and how to apply them across swim, bike, and run. 1. 4 × 8 Minutes — The...

Endurance performance is often talked about as one thing, aerobic fitness, but underneath that phrase are two distinct physiological systems doing very different jobs: capillaries, which deliver oxygen to muscle, and mitochondria, which use it. They adapt to training differently, on different timelines, and in response to different stimuli. Understanding the difference changes how you think about training design. Two Separate Systems, One Shared Goal Capillaries are the delivery network. More...

A dive into the biology of stress, hormones, and why more is not better. There's a stubborn myth in endurance training: that the workout is where fitness is built. It isn't. The workout is where fitness is broken down. Adaptation, the actual improvement in your aerobic capacity, muscle strength, and metabolic efficiency, happens afterward, when you're not training at all. Training load is the stimulus. Recovery is the response. Confuse the two, and you end up chasing fatigue instead of...