Key takeaways
The best interval format is the one that keeps you near VO2max the longest, not the one that hurts most
4×4 and 5×5 suit runners and beginners, 30/15 suits cyclists and trained athletes, 30/30 and 15/15 are easy on the legs
Tabata is a hard anaerobic session with little time near VO2max per workout, so it is a poor first choice for VO2max
Every interval format claims to be the best for VO2max. They can all work, but they differ in how long they keep you near your maximum, how much they hurt and how much stress they put on your legs. This guide compares the main protocols side by side. For a ranking of training methods in general, see the best training for VO2max; for full session instructions, see 10 VO2max workouts.
What makes one interval format better than another
The working idea in the research is time at or near VO2max, often defined as at least 90 to 95% of VO2max. Midgley and McNaughton's 2006 review concluded that intermittent running keeps people at or near VO2max longer than continuous running, and recommended work intervals at 90 to 105% of the velocity at VO2max (vVO2max) with recoveries between 50% of vVO2max and lactate threshold pace. Buchheit and Laursen add that format also changes the anaerobic load and the strain on muscles and tendons, which decides how often you can repeat it.
Three things drive time near VO2max, the point where heart and blood flow hit their limits (see what limits VO2max):
- Rep length: oxygen uptake takes 1 to 2 minutes to climb, so short reps rely on the rests being short too.
- Recovery type: active recovery keeps oxygen uptake high; standing still lets it fall.
- Number of reps: more total hard minutes, more time at the top.
VO2max interval protocols side by side
| Protocol | Work / rest | Intensity | Time near VO2max | Evidence | Best for |
|---|---|---|---|---|---|
| Norwegian 4×4 | 4 × 4 min / 3 min jog | 90–95% HRmax | Moderate: a few minutes per rep once heart rate catches up | Strong: Helgerud 2007, many trials | Beginners to trained runners, older adults |
| 5×5 | 5 × 5 min / 2.5–3 min easy | 90–95% HRmax, ~106–115% FTP | High: 25 min hard | Moderate: supported by long-interval trials | Trained runners, cyclists, rowers |
| 4×8 | 4 × 8 min / 2 min easy | ~90% HRmax | High at lower strain | Seiler 2013 (cyclists) | Well-trained endurance athletes |
| 30/15 (Rønnestad) | 3 × 13 × 30 s / 15 s, 3 min between sets | Hardest repeatable, RPE 9 | High | Good: Rønnestad 2015 and 2020 (cyclists) | Cyclists, triathletes |
| Billat 30-30 | 30 s at vVO2max / 30 s at 50% | About 3k race pace | High: about 8 min in Billat 2000 | Acute studies | Runners, track and treadmill |
| 15/15 | 15 s / 15 s, 2–3 sets | 90–95% HRmax by set end | High: 14 min in Billat 2001 | Helgerud 2007, Billat 2001 | Masters runners, heavier athletes |
| Tabata | 8 × 20 s / 10 s rest | ~170% VO2max, all-out | Low per session (4 min total) | Tabata 1996, five sessions a week | Anaerobic capacity, short fitness blocks |
4x4 vs 30/30
These are the two formats runners ask about most. In Helgerud et al. (2007), 4×4 training three times a week for eight weeks raised VO2max by 7.2%, while a 15/15 format raised it by 5.5%; steady running matched for total work did not change it significantly. The 4×4 has the stronger long-term evidence and is simple to pace by heart rate.
The 30/30 shines acutely. In Billat et al. (2000), runners alternating 30 s at vVO2max with 30 s at half that speed spent 7 min 51 s at VO2max, against 2 min 42 s during a hard continuous run. Because each rep is short, the legs take less damage and form stays good. A sensible rule: do 4×4 when you train by heart rate and want proven results, and switch to 30/30 when your legs feel beaten up or you want a fast-paced change of stimulus.
30/15 intervals
The 30/15 comes from Bent Rønnestad's group in Norway. In Rønnestad et al. (2015), cyclists did either 30/15 intervals or effort-matched 4 × 5 minute intervals twice a week for 10 weeks. VO2max rose by 8.7% with 30/15 vs 2.6% with long intervals. In elite cyclists (Rønnestad et al., 2020), three weeks of 30/15 sessions improved 20-minute power by 4.7%, against a 1.4% fall with long intervals, though the change in VO2max did not differ between groups. The format is brutal on a run because of the repeated accelerations; on a bike, rower or ski erg it is easier to execute. Rønnestad's data come from cyclists, so treat running results as plausible rather than proven.
Tabata for VO2max
The Tabata (1996) study used 7 to 8 × 20 s at about 170% of VO2max with 10 s rest on a bike, five days a week for six weeks. VO2max rose by 7 ml/kg/min and anaerobic capacity by 28%. Most "Tabata" classes are nothing like this: they use bodyweight moves at lower intensity. Even done properly, a single 4-minute set accumulates little time near VO2max. It is a good finisher or a short-block tool, not a substitute for 4×4 or 30/15.
5x5 intervals and longer reps
The 5×5 (five 5-minute reps with about 2.5 to 3 minutes easy) gives 25 hard minutes, a natural progression from the 4×4. Even longer reps can work better for trained athletes: in Seiler et al. (2013), 4 × 8 minutes at about 90% of peak heart rate produced larger gains than 4 × 4 minutes at about 94%, because the cyclists accumulated 32 rather than 16 hard minutes. Use these in the second half of an 8-week VO2max block.
Which interval format should you pick?
| Situation | Pick | Why |
|---|---|---|
| First VO2max block | 4 × 3 min, then 4×4 | Easy to pace by heart rate |
| Runner with niggles | 30/30 or uphill 4×4 | Less pounding per rep |
| Cyclist or indoor trainer | 30/15 | Best cycling data |
| Trained athlete who has plateaued | 5×5 or 4×8 | More total minutes near VO2max |
| 15 minutes available | 10 × 1 min or a single Tabata | Time-efficient, smaller dose |
Rotate formats every 3 to 4 weeks so the stimulus stays fresh, and keep the rest of the week easy, as in 80/20 training. Uphill reps are another leg-friendly option: see hill repeats. If you cannot run, every format here works on a bike, rower or ski erg (VO2max without running).
Pacing each format
- Long reps (4–8 min): pace by heart rate, reaching 90–95% of max by minute 2 to 3. Get your numbers from the heart rate zone calculator.
- Short reps (15–30 s): heart rate lags too much to guide you; use pace or power. Runners can estimate vVO2max (roughly 3k race pace) with the VO2max running calculator.
- All formats: the last rep should match the first. Fading badly means you started too hard.
How many of these sessions to do and how fast results come is covered in how often to do VO2max workouts. Track progress with the VO2max calculator, and find more running guides on VO2max for running. For why people respond differently to the same session, see VO2max trainability.
Safety: hard intervals put a high load on the heart. If you have heart disease, high blood pressure, chest pain or dizziness during exercise, or have been inactive, get medical clearance before starting them.
Frequently asked questions
Is 4x4 or 30/30 better for VO2max?
Both work. The 4×4 has the stronger long-term trial data, while 30/30 keeps you near VO2max for a similar time with less pounding. Many runners rotate them every 3 to 4 weeks.
What are 30/15 intervals?
Thirty seconds hard and 15 seconds easy, usually in 3 sets of 13 reps with 3 minutes between sets. In cyclists they raised VO2max by 8.7% in 10 weeks, more than 4 × 5 minute intervals.
Is Tabata good for VO2max?
The original Tabata study raised VO2max, but subjects trained five days a week. A single 4-minute Tabata gives only a minute or two near VO2max, so longer interval formats are a better choice.
What are 5x5 intervals?
Five 5-minute reps at about 90 to 95% of max heart rate with 2.5 to 3 minutes easy between them. It is a step up from the 4×4 for trained athletes and gives 25 minutes of hard work.
Sources
- Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc, 2007.
- Billat VL, et al. Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time than intense but submaximal runs. Eur J Appl Physiol, 2000.
- Billat VL, et al. Very short (15s-15s) interval-training around the critical velocity allows middle-aged runners to maintain VO2max for 14 minutes. Int J Sports Med, 2001.
- Rønnestad BR, et al. Short intervals induce superior training adaptations compared with long intervals in cyclists: an effort-matched approach. Scand J Med Sci Sports, 2015.
- Rønnestad BR, et al. Superior performance improvements in elite cyclists following short-interval vs effort-matched long-interval training. Scand J Med Sci Sports, 2020.
- Tabata I, et al. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Med Sci Sports Exerc, 1996.
- Seiler S, et al. Adaptations to aerobic interval training: interactive effects of exercise intensity and total work duration. Scand J Med Sci Sports, 2013.
- Midgley AW, McNaughton LR. Time at or near VO2max during continuous and intermittent running: a review with special reference to considerations for the optimisation of training protocols to elicit the longest time at or near VO2max. J Sports Med Phys Fitness, 2006.
- Buchheit M, Laursen PB. High-intensity interval training, solutions to the programming puzzle. Part I: cardiopulmonary emphasis. Sports Med, 2013.
- Buchheit M, Laursen PB. High-intensity interval training, solutions to the programming puzzle. Part II: anaerobic energy, neuromuscular load and practical applications. Sports Med, 2013.