Workout of the Week: Variable Workload VO2max Intervals 

Get the most out of your hardest efforts with this VO2max intervals bike set.

Workout of the Week
Photo: Shutterstock

This week’s Workout of the Week builds on a previous one—Intro to Fast Start VO2max Intervals—and is designed to really help you get the most bang from your interval training buck.

It’s going to mean taking your oxygen consumption up a notch by switching from a “fast-start” to a variable-intensity interval. Based on a 2021 Dr. Ronnestad paper, fast-start VO2 intervals ramp your oxygen consumption quickly, leading to increased oxygen consumption over traditional steady intervals. These variable-intensity intervals, however, drive your oxygen consumption quickly and keep it soaring throughout, leading to even higher oxygen consumption.  

It’s hypothesized that this workout is effective because it increases time spent at >90% of your VO2max by recruiting muscle fibers only utilized at a maximal aerobic effort. Because of this, it’s important to enter this workout feeling fresh and well-fueled, and to recover well after it. These efforts are taxing and not to be trifled with throughout the year, but you’ll see a big improvement in power within a few key sessions (so use them wisely). 

 It’s easiest to do this workout on the trainer, but if you’re looking for more race prep and handling work then it’s advised to complete the efforts outside. Find a smooth gradient that allows you to control your effort for the entire five minutes on each interval; nothing so steep that it forces you to go harder than you want.  

For this workout you should start with three rounds then build to a maximum of five as your fitness (and pain tolerance!) improves.  

The surge workload is at 100% of your MAP (Maximum Aerobic Power). While there are various definitions of MAP I use best 5-minute effort to approximate this value. To use round numbers, we’ll say this is 400 watts.   

The lower workload is found by subtracting your FTP from your MAP, taking 20% of this difference, and adding it to your FTP. For example, this would be 400w less 300w (100w), 20% of which is 20w, so I’d plan to hit the 4-minute interval at 320w. 

Workout of the Week: Variable Workload 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: 

3 x [40-sec. surges @ MAP + 1 min. @ (FTP + 20% of (MAP – FTP)]

3 min. rest between rounds 


5-10 min. easy spin

Feeling like something a little different? Check out last week’s Workout of the Week: The Big Stupid Ride