How a Two-Year Exercise Program Improved Heart Fitness

Derek: You mentioned the Norwegian 4×4 as an important way to train VO₂ max.

Dr. Rhonda Patrick: It is. I have used a rowing machine or stationary bike for it. It is a hard workout.

One motivating study came from Dr. Benjamin Levine's group. It enrolled healthy, sedentary adults ages 45–64 and randomized them to two years of progressive endurance training or an attention-control program that included yoga, balance, and strength activities.

The exercise program started gradually. You cannot take someone who is inactive and immediately prescribe very hard intervals. The intensity was relative to each participant's fitness. A brisk walk could initially be a hard interval for one person.

Derek: What is VO₂ max?

Dr. Rhonda Patrick: VO₂ max measures cardiorespiratory fitness. It is the maximum amount of oxygen a person can use during hard exercise. A laboratory test measures oxygen consumption during a graded treadmill or cycling test. Watches and field tests can estimate it, but they have more individual error.

The Cooper 12-minute run is one field method. A person covers as much distance as possible on a flat track for 12 minutes, then uses the distance in an estimation equation. It is a strenuous test and is not appropriate for everyone without screening or preparation.

Higher cardiorespiratory fitness is strongly associated with lower mortality and longer life. Those associations do not prove that increasing one person's VO₂ max produces a fixed number of extra years.

In Dr. Levine's trial, participants built toward four or five exercise sessions per week. The program included moderate aerobic work, a longer low-intensity session, interval training, and some strength work. At peak volume, they completed about five or six hours per week. The Norwegian 4×4 was one part of the program, not the whole intervention.

After two years, directly measured VO₂ max increased by about 18 percent in the exercise group. Left-ventricular stiffness also improved. The control group did not show those changes.

The finding is sometimes described as making the heart “20 years younger.” The study did not measure a validated cardiac biological age or reverse chronological age. It showed better fitness, reduced left-ventricular stiffness, and favorable cardiac remodeling.

Derek: How does the Norwegian 4×4 work?

Dr. Rhonda Patrick: After a warm-up, a person completes four four-minute hard intervals separated by about three minutes of active recovery, then cools down. The effort should be hard but controlled and repeatable, not an all-out sprint.

Longer intervals create a strong cardiovascular stimulus, but shorter intervals can also improve fitness. The Norwegian 4×4 is not the only effective protocol.

Derek: How often can someone do it?

Dr. Rhonda Patrick: It depends on the rest of the person's training and recovery. In the two-year study, participants gradually worked up to two interval sessions during part of the program, then generally used one interval session per week during the later maintenance phase.

There is no clear dose-response study that defines one universal best weekly frequency. Someone who already trains hard may not need more high-intensity work. An inactive person needs a gradual progression and an aerobic base.

People with relevant medical conditions or warning symptoms should get clinical guidance before starting vigorous intervals. Moderate continuous activity and shorter intervals remain effective options.