Raise the ceiling — VO₂max
If your Fractional Utilization is already in the 80–85% range, the engine is the bottleneck. The aim is more oxygen at the muscle.
- 5×4 min at 110–115% CP, 4 min recovery. Once a week through a 6-week block.
- 30/30s — 30 s at 130% CP, 30 s at 50% CP, 12–15 reps × 2 sets.
- Hill repeats 3–5 min at maximum sustainable power, with full recovery between reps.
Lift the threshold — CP
If your VO₂max is high but your Fractional Utilization is below 75–78%, the engine is fine — you just can't use it for long. Time at threshold and sweet-spot fixes that.
- 2×20 min at 95–100% CP, 10 min recovery. Twice a week, capped at 4–5 weeks before regression.
- 3×15 min at 88–92% CP (sweet spot), 6 min recovery. Builds aerobic durability without overshooting.
- Long Z3 endurance — 90–120 min at 75–85% CP. Once a week, ideally as a long ride finisher.
Build the base — FatMax
Whatever the priority above, keep one foot in the FatMax zone (Z2, 65–72% CP). Substrate flexibility is what lets the harder efforts pay off — without it, the engine never has fuel to burn.