STUDfit · Run
VO2 intervals
Also known as
vo2 max intervals · norwegian 4x4 · 4x4 · speed work · track intervals
Community talk may be wrong. Not medical, training, or diet advice. Sharp pain, fainting, or disordered-eating concerns need a clinician.
In brief
VO2 intervals are repeated hard cardio efforts separated by recovery periods, discussed as training aimed at aerobic capacity.
The common picture
4 × 4 minutes hard, with 3 minutes easy betweenThe four repeats contain 16 total hard minutes.
Shorter option: 6–10 × 1–2 minutes hardThe examples use equal or longer easy recoveries.
Once a weekNext to easy miles, not instead.
Hard but controlledLast repeat looks like the first. That is the skill.
Warm-up: 10–20 easy minutesThe shorter-repeat and 4×4 versions are both described below.
People compare running, cycling and other formats, the length of work and recovery periods, and how hard sessions fit beside easier training.
Good to know. Four interval days. Starting here as a new runner. Racing the recoveries.
What people say
- The job: A little time at a high output so the easy week has a ceiling to push.
- Peter Attia / Norwegian 4×4 made this a 2020s brand. The session is older than the podcast.
- r/running 2026 still argues Zone 2 vs intervals. Hybrid weeks keep both.
- Self has VO2 / hard-cardio habit cards. Fit owns the session.
- New runners do not need this. C25K and easy miles first.
- Why people get hurt: they do intervals on tired legs after a long run, or they do them daily.
- Bike / rower 4×4 is easier on joints and easier to keep honest.
- Track nights are social and too fast. Ego lives in lane 2.
- Hyrox people sometimes think stations replace this. They do not replace easy miles either.
- Watch “VO2 max” scores are noisy. The session is not for a ring to go up tomorrow.
- It should not be a race. If they vomit, they went looking for a story.
How people do it
- One day. They write it on the calendar so they do not add a second.
- Warm up until they feel like they could jog forever.
- Hard bouts at a pace they can repeat — not a first-rep hero sprint.
- Recoveries are easy. Jog or walk. Not a tempo.
- They stop if form or a joint falls apart.
- Easy next day. Walks fine. Another quality session not fine.
- Heat / bad sleep: they skip or cut to 2–3 bouts.
Amounts people use
- 4×4: 4 min hard / 3 min easy × 4.
- Shorter: 6–10 × 1–2 min hard with equal or longer easy.
- Days: 1 a week for hobby people.
- Warm-up: 10–20 minutes easy.
- Total hard time: often 12–20 minutes, not 40.
How people keep it
- A hill or a bike so pace ego is quieter.
- A partner who will not turn it into a race.
- They skip it during a cut that already feels awful.
- They keep easy miles as 80% of the week.
- A deload week without intervals every few weeks.
How it may feel
- Rep 1: too fast if they are normal.
- Rep 3: this is the workout.
- Rep 4: character. Or they already blew it on rep 1.
- After: legs heavy, mood oddly good.
- Next day: a little wrecked. Easy only.
- A good block: 5K pace feels less like panic. Easy pace may drop too.
How long
- In a race block, once a week for 4–8 weeks.
- Off-season: they may drop it and only go easy.
- It is not a 28-day identity.
- After 40: shorter, fewer, more warmup.
The longer notes
- Tempo is comfortably hard. This is hard. Different days.
- Easy miles pay the bill. Intervals without a base is junk tired.
- Norwegian 4×4 is one recipe. Hills and bikes count.
- Hyrox still wants this plus sled practice. See HYROX.
- Kids / true beginners: no.
Good to know
- Not a first-month runner session.
- Not four times a week.
- Do not race the recoveries.
- Chest pain, wheeze, fainting: person and clinician.
- A watch VO2 number is not a diagnosis or a goal.
Also on this house
Earlier wording (updated)
- Norwegian 4×4 4 minutes hard, 3 minutes easy, four times. Attia-adjacent and r/running both say the name.
- Or shorter repeats 8×400, 5×800, hill sprints — same job, different costume.
- Long warmup 10–15 minutes easy plus strides. The first interval is not the warmup.