2. To improve your ability to boost effort then recover at race pace, do 12/3s
Alternate 12 minutes at race-specific intensity with 3 minutes one zone up (if you’re racing Ironman, do your 3 minutes at half-Ironman race pace).
Olympic-distance athletes can build to 45-minute sets (3×12/3 continuous), 70.3-distance athletes can build to two 75-minute sets (5×12/3) and iron-distance athletes can build to two 90-minute sets (6×12/3).
Most athletes overestimate optimal bike effort, so start a little easier than you think you need to.
For an added benefit, change your cadence in the middle of each 12-minute segment. For example, alternate 92/60/92 RPM for each 4-minute chunk.