Workout of the Week: Fast-Start VO2max Intervals

This session builds off our intro workout on fast-start intervals with a step-down workload that will have your legs screaming.

Man sprinting on his bike past a field of sunflowers
Photo: Slav

Last year we introduced a workout based on Dr. Bent Rønnestad’s research that I titled “Intro” to Fast-Start VO2max Intervals. That workout was designed to ramp up your oxygen consumption quickly with a high initial workload before backing off to prolong your time at high-oxygen consumption values. This is because there is evidence that correlates training time at 95% or greater of VO2max with significant improvements in VO2max values. However, that workout is an introduction—an easier version—to the work that was suggested by Dr. Rønnestad. This week, we’re going to kick it up a notch.  

RELATED: Fast Talk Episode 211—Does Strength Training Help or Hurt Endurance Sports Performance? With Dr. Bent Rønnestad

The emphasis of this workout is still the same as the intro—a hard initial effort is meant to ramp your oxygen consumption quickly. After 2 minutes at a very difficult workload, the effort backs down slightly, prolonging time spent at near-maximal oxygen consumption.

The key is to maintain control and to chunk the workout into segments. The initial workload needs to be approached with confidence; at your best you’re able to hold this 2-minute effort for a full 5 minutes. I start my progression by leading with a 1-minute spike in my 5-minute efforts. If that’s comfortable, add a fourth, then fifth 5-minute effort. 

The step-down workload also needs to be treated with confidence. Your legs will be burning and your mind will be screaming to stop. Don’t listen. Focus on your cadence, smooth breathing, and seeing the effort through to the end. This is what makes you stronger! 

Note on Determining Workloads 

  1. The fast-start workload is at 90 to 100% of your Max Aerobic Power, which is approximately the highest 1-minute workload in a ramp test or approximated by current 5-minute power. For example, 400 watts.  
  2. The second, steady, workload is at the midpoint of this value (400W) and your FTP (for example 300W). To determine this, you would find the difference (400 – 300W) = 100W, then add 50% of that (50W) to your FTP (300W) to get a final workload of 350W for the steady portion. 

Workout of the Week: Fast-Start VO2max Intervals 


10 min. build from 50% to 70% FTP 
3 min. @ 50% FTP with 3 × 10 sec. sprint 

Main set 

3 sets: 

  • 2 min. @ 90-100% Maximum Aerobic Power (MAP) 
  • 3 min. @ FTP + 50% of (MAP – FTP) 

3 min. set rest 


5 min. easy spin to allow heart rate and blood pressure to drop