If I had to pick one interval format that delivers the most VO2max bang for your time and suffering, 30/15s would be right near the top. They have been used in running and team sports for years, but most cyclists have never tried them — and that is a missed opportunity.
The concept is simple. Ride at 110 to 120 per cent of FTP for 30 seconds, then spin easy for 15 seconds. Repeat. A typical set is 8 to 13 reps, and you would do two to three sets per session with five minutes of easy spinning between them.
What makes this format special is physiology. During traditional long VO2max intervals — say five minutes at 105 per cent — your oxygen consumption ramps up over the first couple of minutes and only sits at true VO2max for the final portion. With 30/15s, the short recovery means your oxygen uptake never fully drops back down. After the first two or three reps, you are at or near VO2max for the rest of the set. You accumulate far more total time at peak oxygen consumption compared to the same total work time done in long intervals.
The other advantage is psychological. Staring down a five-minute VO2max block is grim. Knowing you only have to hold on for 30 seconds at a time? Far more manageable. You complete more work, with better quality, and you are less likely to bail halfway through a rep.
Start with two sets of eight reps and build from there. Keep the 30-second efforts controlled — this is about sustaining high oxygen uptake across the set, not sprinting every rep into the red. If you cannot finish the set, drop the power by five watts and try again.
Two sessions per week alongside your endurance rides. Give it four weeks and watch your ability to sustain hard efforts improve.
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