09/04/2026
Stop doing the Norwegian 4x4.
. at least the way it was written.
First, the protocol works. Helgerud et al. (2007) ran 4 x 4 minutes at 90-95% of heart rate max, 3 minutes of active recovery at 70%, three days per week for eight weeks.
VO2max went up 7.2%. Stroke volume went up about 10%.
That part was never the problem.
The problem is what happens when heart rate is the thing you chase.
Minute one, your watts are on target. Then heart rate climbs on its own. So you ease off to hold the prescribed number.
Same heart rate. Less actual work.
The number looked perfect the whole time.
Morales-Palomo et al. (2017) measured exactly this. To hold a target heart rate during intervals, subjects had to drop power by 30 watts. In steady-state work, the drop was only 10 watts.
Cardiac output and stroke volume fell too. Only in the intervals.
Now the honest part.
That was 14 adults with metabolic syndrome, not lifters. It was a single session, not eight weeks of training. It measured the workload cut — not the long-term outcome.
Mechanism ≠ outcome.
But it still shows you exactly where the leak is.
So here is how I actually program it.
Heart rate reports. Output governs.
Get on a rower or any erg and do an all-out 2K. That pace sits near your VO2max. Take the average watts. Say it lands at 200.
That 200 W is now your target. Not a heart rate zone.
Four minutes at 200 W.
Then rest until your heart rate comes back down — open-ended, not a three minute clock.
Go again at 200 W. Repeat while you can hold it.
Watts set the work, heart rate sets the rest.
And this is the part I like most: you get a real stop rule.
If you cannot hold 200 W, that interval was your last one. No amount of extra rest changes that answer. You are done for the day.
That is what keeps you from digging a hole.
Progression is simple. Build to four intervals in one session. Then add a second day. Build that day to four, then add a third.
Add intervals first. Days second. Start with one day per week.
Want the full modified 4x4 protocol?
Comment 4X4 below.
Much love and a bigger engine,
Dr Mike
PS — heart rate is still worth recording. It is data. It is just not the boss.
