This training block focuses on developing your VO₂ capacity — your ability to take in, transport, and use oxygen at very high intensities. VO₂ work sits above threshold and pushes you into the zone where breathing is hard, effort feels demanding, and you’re working close to your maximum sustainable aerobic power. It’s uncomfortable by design, but it’s a key driver of fitness: raising your ceiling so your race pace becomes more economical and your body can handle surges and sustained speed. Sessions will use shorter, high-intensity repeats with controlled rest to allow partial recovery while keeping you working in the right zone. The focus is quality at high speed — maintaining good form under fatigue, hitting consistent splits, and learning to stay composed when intensity climbs. The goal isn’t sprinting; it’s controlled fast swimming at the edge of your aerobic limit. By targeting VO₂, you’ll strengthen your top-end aerobic power, improve race-phase surges, and build confidence handling higher-intensity efforts in training and competition. Over time, this block will help you swim faster for longer, respond to pace changes in open water, and recover more quickly after hard efforts. Expect to finish these sessions knowing you’ve worked hard — and feeling fitter, sharper, and better prepared for the demands of triathlon swimming.