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RunVO2max

Norwegian 4 × 4

4 × 4 min at 90–95% max HR, 3 min easy jog

Time
53 min
Hard
16:00
in zones 4–5
Difficulty
Very hardDifficulty 4 of 5 — Very hard
Inspired by
Jan Helgerud

What we typed

Warm up 15 min easy. 4 × (4 min at 90–95% of max heart rate, about 3K–5K effort; 3 min easy jog, no target — about 70% of max heart rate as a guide). Cool down 10 min easy.

Fit File Forge built the steps below from these words — the same steps your watch gets.

Describe your own

The session

4 steps

Warm up

Easy

15 minZ2
4×4 min

Rep

About 3K–5K effort

4 min90–95% max HRZ5

Jog

Easy; about 70% of max heart rate as a guide

3 minZ1

Cool down

Easy

10 minZ1

Targets

Set by heart rate, as a share of your max. Your watch works out the bpm from the max HR in its own settings, so it keeps up as that changes.

90–95% max HR

Heart rate takes a minute or two to climb, so run the start of each rep by feel.

Scaled version

3 × 4 minutes, or 4 × 3 minutes, with the same 3-minute jogs.

Build the scaled version in Forge

About this session

The story

From Jan Helgerud and colleagues' study at the Norwegian University of Science and Technology: moderately trained men ran 4 minutes at 90–95% of maximum heart rate, each followed by 3 minutes of active recovery at about 70%, three times a week for eight weeks. Their VO2max rose about 7% — more than in the groups that did the same work as long easy running or at lactate threshold.

What it trains

VO2max — the ceiling of your aerobic engine — with reps long enough to hold your heart rate near the top for minutes at a time.

Who it's for

Runners of any level with a few weeks of steady running behind them. 'Hard' is about 3K–5K effort: tough, but the fourth rep should be as strong as the first.

Sources 1
  1. Aerobic high-intensity intervals improve VO2max more than moderate training — Medicine & Science in Sports & Exercise (PubMed), 2007

I've been using the AI Training Coach from day 1 for marathon prep and have found it to be a huge step up from ChatGPT/Gemini — I couldn't be happier.

Dave F.Marathon athlete

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