Workout of the Week: “Intro” to Fast-Start VO2max Intervals

Bust out of winter hibernation with this challenging bike intervals workout.

cyclist riding hard uphill
Photo: Shutterstock

It’s early February. For some that means the “sitting on the couch” phase is soon coming to an end. For others it means their base season is in full-swing as they prepare for the upcoming year. There’s always a perpetual debate about how much and what types of intensity to include at this time of year, but universally everyone ought to agree that the base season isn’t just about noodling around in your small chainring.  

Here in Colorado, our best climbs are still snow-covered and I wait before building my longer threshold-focused efforts into my plan so as to avoid having to steal books from a neighborhood “little free library” to stave off frostbite (again).  

That means my high-intensity work is still on the trainer where it’s the perfect place to execute variable-effort intervals that Dr. Bent Ronnestad has shown to increase time above 90% of an athlete’s VO2max. This workout ensures you get the most bang for your VO2 buck.

The fast start to these intervals ramps up your oxygen consumption quickly prior to settling into a lower sustainable effort. However, it also makes these intervals quite difficult when you’re coming out of your winter hibernation. I start my progression by leading with a 1-minute spike in my three 5-minute efforts. If that’s comfortable, add a fourth, then fifth, 5-minute effort. Once five efforts with 1-minute spikes are comfortable, begin increasing the spike to 1:30, then 2 minutes. Once you’ve mastered five sets of 5 minutes with a 2-minute spike, you can try the Variable Intensity VO2max Intervals that I’ll describe in an upcoming Workout of the Week.  

The fast-start workload is at 90% to 100% of your MAP (Maximum Aerobic Power), which would be approximately your best-effort 5-minute power. For example, for me this would currently be around 400 watts.  

The second steady workload interval is designed to allow you to sustain the higher oxygen consumption without fatiguing prematurely. To find the correct intensity of this interval for you, subtract your FTP from your MAP, take 20% of this difference, and add this to your FTP. For example, for me, this would be 400w less 300w (100w), 20% of which is 20w, so I’d plan to hit the 4-minute interval at 320w.

Fast-Start VO2max Intervals 


10 min. build from 50% to 70% FTP 

3 min. @ 50% FTP with 3 x 10 sec. sprint 

Main set 

3 rounds of: 

1 min. @ 90-100% of Maximum Aerobic Power (MAP) 

4 min. @ FTP + 20% of (MAP – FTP) 

3 min. rest between rounds 


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