The Norwegian 4×4 Workout

If you have 40 minutes and access to any piece of cardio equipment, you have everything you need for one of the most effective cardiovascular workouts available.

The Norwegian 4×4 is a high-intensity interval workout developed in the 1990s by exercise scientists Jan Helgerud, PhD, and Jan Hoff, PhD, at the Norwegian University of Science and Technology. The format is simple: four minutes of hard effort followed by three minutes of easier recovery, repeated four times.

While similar to other types of interval training, the 4×4’s focus is on correct intensity, not exhaustion. And it includes intervals to keep your heart working at a high capacity long enough to make real changes, says Helgerud, a professor of medicine and exercise science and former head coach of the Norwegian national cross-country skiing team.

“We are not training to be tired,” Helgerud explains. “We are training to increase how much blood the heart can pump per beat.”

This method focuses on improv­ing VO₂ max, which measures how well your body uses oxygen. Having a high VO₂ max is a reliable sign of a healthy heart and one of the best predictors of a long life. And this style of long-interval training is especially good at improving it.

In one study, men who did the 4×4 workout three times a week for eight weeks improved their VO₂ max by about 6.5 percent; the workout was more effective than shorter, faster sprints. Additional research suggests that the protocol can effectively improve aerobic capacity and heart health for people with heart disease.

You can do the workout on a treadmill, bike, rower, or anything that lets you reach and sustain a high work rate.

“Running works great, but if that isn’t your jam, then use an incline and power walk,” says Wes Pedersen, SGT coach and member of the GTX programming team at Life Time. “Anything that works as much of your body as possible will get you to your target heart-rate zone efficiently.”

Begin by performing this workout once weekly as part of a routine that includes strength training and lower-intensity cardio. As your fitness improves, or if you are an advanced athlete, Helgerud recommends working up to two or three sessions each week.

After about two to four weeks, the workout will start to feel more manageable, he says. Look for progress in how quickly you can recover during the rest intervals and whether you are able to maintain your target intensity more consistently.

By one to two months, Helgerud says, you can expect clear improvement in your VO₂ max. You’ll likely notice a lower resting heart rate, a lower heart rate at the same pace, and the ability to work harder without the same strain.

Over the longer term, you’ll likely hit a normal training plateau depending on the total number of interval sessions, but see lasting improvements in cardiovascular health, work capacity, and tolerance for high-intensity effort. In your daily life, you’ll likely feel less out of breath during physical activity and have more energy when you need to push yourself. “This is where you feel fitter,” Helgerud says.