VO2 30/30s — Free Zwift Workout
(.zwo Download)
30 seconds at 115-120% FTP, 30 seconds easy, repeated. The Billat protocol — maximises time at VO2 max without the rep-by-rep breakdown of 4-minute blocks.
Built by Jim Camut. JB Cycling Academy 2004–09 · PCS-verified · Cyclingnews diarist alumnus.
Where are you in your riding?
Races Cat 3/4
What do you want from this workout?
110–120% FTP — engine-builder intervals
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Free .zwo file. Drop it in your Zwift workouts folder — it shows up under Custom Workouts the next time you launch the app.
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VO2 30/30s: prescription + science
Thirty seconds hard, thirty easy, repeated — the short-interval route to VO2 max. Here's why micro-intervals let you bank more time at your ceiling than long reps.
Why short intervals
Alternating short hard efforts with short recoveries accumulates more total time at VO2 max than a single continuous effort, because VO2 stays elevated through the brief recoveries instead of resetting [1]. You get the ceiling stimulus without the rep-by-rep power loss of 4–8 minute blocks.
Short beats long, effort-matched
When total work is matched, short intervals have produced superior endurance and power adaptations versus long intervals in trained cyclists [2]. The 30/30 structure is the most accessible version — high quality, repeatable, and forgiving of a rough day.
Recovery intensity matters
The “off” 30 seconds isn't fully passive — keeping it a genuine easy spin rather than a coast changes the physiological and perceived cost of the session [3]. Keep the recoveries honest and the work intervals stay sharp.
Peer-reviewed sources
- 01Billat et al. 2000. Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time. European Journal of Applied Physiology, 2000.
- 02Rønnestad et al. 2015. Short intervals induce superior training adaptations compared with long intervals in cyclists. Scandinavian Journal of Medicine & Science in Sports, 2015.
- 03Fennell & Hopker 2021. The acute physiological and perceptual effects of recovery interval intensity during cycling-based high-intensity interval training. European Journal of Applied Physiology, 2021.
VO2 30/30s: common questions
What power are 30/30 intervals?
The work bouts sit around 115–120% FTP (or your best ~5-minute power); recoveries are an easy spin. The .zwo sets the watts from the FTP you enter.
Are 30/30s really VO2 max work?
Yes — done in sets, they hold VO2 near its ceiling for more total time than long reps, which is the adaptation that matters most for raising your aerobic ceiling.
30/30 vs 4×4 — which is better?
Both target VO2 max. 30/30s accumulate more ceiling time with less breakdown; 4×4 is a bigger single-rep stimulus. Rotating them beats grinding one.
How many 30/30 reps should I do?
In sets of roughly 8–13 with rest between sets. The generator scales the count to your experience level so you finish the session strong, not shelled.
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