How to Do the Norwegian 4x4 on a Bike

To do the Norwegian 4x4 on a bike: warm up 10 minutes, then ride 4 minutes hard enough that your heart rate reaches 85–95% of max, spin easy for 3 minutes, and repeat four times before cooling down. On a smart trainer, start around 85–90% of FTP and adjust; heart rate — not watts — is the target.

The bike might be the most forgiving place to run this protocol. Zero impact, precise control over workload, and no chance of a pothole ending interval three. The original Helgerud 2007 study used treadmill running — worth being honest about — but the 4x4 is defined by heart-rate zones, not by modality, and the 7.2%-in-8-weeks VO2 max improvement it demonstrated came from time spent at 85–95% of max heart rate. A bike gets you into that zone just fine. Full protocol background lives in the Norwegian 4x4 protocol guide; this article is the cycling execution.

Should you target watts or heart rate?

Heart rate. This trips up cyclists specifically, because cycling culture is power-obsessed and power is genuinely the better metric for racing. But the 4x4 is not a race workout — it's a cardiac workout. The adaptations it's chasing (stroke volume, VO2 max) come from the heart working at 85–95% of its max, and heart rate is the direct readout of that.

So use power the way you'd use a steering wheel: it's how you point the workout in the right direction and hold a steady line, but the destination is a heart-rate zone. In practice:

1. Open at 85–90% of FTP if you know your FTP. No FTP? Ride at 7–8 out of 10 effort — breathing hard, able to spit out three or four words, no more.
2. Ignore heart rate for the first 90 seconds. It will read low. That's lag, not laziness (more on this below).
3. Read the number at minute 3. Below 85% of max? Add 5–10 watts next interval. Pinned at 95% and rising? Drop 10–15 watts.
4. Expect watts to stay flat while heart rate climbs. Cardiac drift means round four often sits 3–5% of max HR higher than round one at identical power. That's fine. Hold the power, let the heart rate drift up within the zone.

One dependency: the zone is only as good as your max heart rate number, and 220-minus-age is a blunt instrument. Get a real number first — method in how to find your max heart rate. And note that cycling max HR typically runs a few beats below running max HR because less muscle mass is working, so if your max came from running, don't panic when the bike won't quite reach it.

Erg mode or gears: how should you set up a smart trainer?

If you have a smart trainer, you have two ways to control the work interval, and they suit different people.

Erg mode holds your target wattage automatically — you just pedal and the trainer adjusts resistance to keep power constant regardless of cadence. For the 4x4 it's excellent: no drifting soft in minute three, no accidental surges, perfectly repeatable intervals week over week. Two cautions. First, the "spiral of death": if you're overcooked and your cadence drops, erg mode piles on resistance to hold watts and can grind you to a halt — set a realistic target and shift down your expectations, not your gears. Second, erg mode obeys the number you gave it, so when your minute-3 heart-rate check says the wattage is wrong, change the target between intervals rather than suffering through a mislabeled workout.

Resistance/gear mode (or a dumb trainer, or the road) puts you in charge: pick a gear and cadence that produce the effort, and hold it yourself. It demands more attention but teaches pacing, and it lets you respond to heart rate mid-interval — ease off two clicks when you're trending hot — which erg mode makes awkward.

My take: erg mode for intervals two through four, once the minute-3 check from interval one has told you the right wattage. Use interval one as the calibration lap.

What about spin bikes and stationary bikes?

No power meter, no problem — the protocol predates smart trainers by decades. On a spin bike, gym stationary bike, or air bike:

• Set effort by feel first. Resistance and cadence combined should feel 7–8 out of 10. On most spin bikes that's a moderate-heavy flywheel load at 85–95 rpm.
• Confirm with heart rate. A chest strap paired to a watch or phone is strongly recommended here, since bike consoles' grip sensors are useless mid-interval. You want to see 85–95% of max for roughly the back half of each 4-minute interval.
• Note your settings. Resistance knob position (or level number) and cadence are your poor-man's power meter. Write down what produced the right heart rate; next session, start there.
• Air bikes count double. Arms plus legs means heart rate comes up faster and higher. Start conservatively — an air bike will happily put you at 95% in ninety seconds.

Why does heart rate lag on the bike, and what do you do about interval one?

When you jump from easy spinning to interval wattage, your muscles need the oxygen immediately but your heart rate takes roughly 60–90 seconds to catch up — often a bit longer on the bike than running, because the smaller working muscle mass and seated position blunt the cardiac response. This lag causes the single most common 4x4 cycling error: riders see 75% of max at minute one, conclude they're slacking, surge 40 watts, and then watch heart rate blow through 95% at minute three with two intervals still to go.

Handle it like this:

• Interval one is a rolling start. Ride the opening 90 seconds on power or feel alone, with the heart-rate field mentally switched off.
• Judge only minutes 3–4. That's when heart rate reflects the actual workload. Landing at 85–90% by minute 3 of interval one is perfect — later intervals will start from a higher baseline and reach the zone faster.
• Never chase the display. Decide power between intervals, not during them. A 4x4 ridden on steady watts that ends at 93% beats one ridden as a heart-rate-chasing sawtooth every time.

The recovery side of the lag is worth watching too: how far your heart rate falls in the first 60 seconds of each 3-minute recovery is a fitness marker with real prognostic weight — Cole 1999 found recovery of 12 beats or fewer at one minute predicted mortality. Keep the legs turning at very light resistance during recoveries (don't stop pedaling) so those readings stay comparable. More in heart-rate recovery.

Should you ride seated or standing?

Mostly seated. Seated riding is more efficient, easier to hold at a steady wattage, and keeps heart-rate response consistent across intervals — which matters when the whole point is comparable heart-rate data.

Standing has two legitimate uses. First, a 10–15 second stretch once or twice per interval to relieve the saddle and recruit fresh muscle. Second, a deliberate tool late in interval four if you're just under the zone floor and want a few more beats — standing raises heart rate at the same power because you're supporting body weight. What standing shouldn't be is your default, and definitely not on a spin bike with the resistance too light, where bouncing out of the saddle fakes effort the flywheel isn't providing.

What does a full bike 4x4 session look like?

Example for a rider with an FTP of 200 W and a max heart rate of 185. Scale the watts to your own numbers; the heart-rate column is the workout.

About 38 minutes total, one to three times per week. If four full intervals is out of reach right now, shrink the intervals rather than the intensity — the ramp-up plan is in the beginner's guide, and runners can find the treadmill version in the Norwegian 4x4 on a treadmill.

Let the data show the adaptation

On the bike the 4x4 produces beautifully clean data: steady watts in, heart-rate response out. Watch that relationship across weeks — the same 175 W costing 165 beats instead of 172, recovery dropping further in the first 60 seconds — and you're watching your heart get stronger. That's the exact view I built Viking 4x4 around: per-interval heart-rate reports and HRR-60 trends. Other apps time your workout. Viking 4x4 shows your heart adapting.