As summer approaches, many people try to get back into healthier exercise habits. Most of us already know physical activity is important, but sticking with a routine can still feel challenging, especially when time is limited.
Current health recommendations suggest exercising for at least 2.5 hours each week, with 5 hours considered even better. For many people, that target can seem overwhelming.
But research from the past two decades suggests the amount of exercise needed for meaningful health benefits may be much lower than many assume. According to researchers, just 30 minutes of high intensity exercise per week can improve health. That works out to roughly 4.5 minutes per day or about 10 minutes every other day. The important part is intensity. The activity needs to be strenuous enough to leave you noticeably out of breath.
If you use a heart rate monitor, researchers say your heart rate should reach about 85 percent of your maximum. However, special equipment is not necessary. A simple way to judge intensity is by how difficult it is to talk. You should still be able to speak in short sentences, but you should not be able to sing or carry on a continuous conversation comfortably.
Why Cardiovascular Fitness Matters
“The biggest reported challenge regarding exercise is lack of time. But with intense, short workouts, this is no longer a valid excuse,” said Ulrik Wisløff, a professor at the Norwegian University of Science and Technology (NTNU) and head of CERG, a research group that conducts research on the health effects of exercise.
Researchers say even a small amount of high intensity activity can improve cardiovascular fitness, which plays a major role in long term health.
“Cardiovascular fitness is the best indicator of current and future health. Good cardio fitness reduces the risk of over 30 lifestyle diseases as well as premature death by 40 to 50 percent,” explained Wisløff.
CERG first documented these effects in a 2006 study that analyzed health information from 60,000 people. Since then, additional large studies from Norway and other countries have reported similar findings.
Is It Better To Spread Workouts Out?
Would it be just as effective to do one intense 30 minute workout each week instead of several shorter sessions spread across multiple days?
“It is best to spread the sessions out a bit, because exercise also has an acute effect that lasts for one to two days, so that way you get the best of both worlds,” said Wisløff.
Researchers say blood pressure and blood sugar control improve for 24-48 hours after a workout that pushes you hard enough to become breathless for several minutes. Because of these short term benefits, experts recommend dividing exercise across two to four days per week whenever possible.
Short Interval Training Can Be Effective
That does not necessarily mean sprinting at full speed or using the highest resistance setting on an exercise bike.
“No. Your own personal fitness level determines what gives you a high heart rate. If you are not very fit, simply taking a brisk walk may be enough. Having said that, you need to walk fast enough that you get quite out of breath. You can then increase the intensity as your fitness improves. Short intervals are effective. For example, this could be bursts of 45 seconds with 15-second breaks. Or like in Tabata workouts, with intense 20 second intervals interspersed with 10 second breaks. Otherwise, 4×4 intervals are recognized as highly effective for increasing oxygen uptake,” Wisløff said.
Fitness Must Be Maintained
Can you compensate for skipping exercise this week by doing extra workouts the week before?
“No. Fitness is something you have to maintain. Cardio fitness and strength decline quickly when not maintained, especially as you get older,” said Atefe R. Tari, a researcher and head of CERG’s initiative on exercise and brain health.
Strength training is also considered important, particularly for middle aged and older adults.
“We know that strength training is important, especially for middle-aged and older adults. There is limited research on how strength training affects lifespan, but a HUNT study exploring this is due to be published soon,” said Wisløff.
The Trøndelag Health Study (The HUNT Study) is a long running population health study in Norway that has gathered health data for more than 40 years.
New AQ Measurement Tracks Exercise Intensity
Researchers have also introduced a new measurement system called AQ (Activity Quotient).
Unlike traditional activity tracking methods that focus mainly on steps or workout duration, AQ measures exercise intensity by monitoring heart rate. Researchers say this provides a more accurate picture of whether someone is active enough to improve health.
Scientists at NTNU and CERG developed the AQ algorithm using population data from five countries, including Norway.
AQ can be measured through the Mia Health app created by NTNU and Sintef through the spin-off company Mia Health. The app connects with heart rate monitors, although users can also manually enter activities if they are not wearing one.
How AQ Points Work
AQ points are earned whenever physical activity raises your heart rate enough to make you slightly out of breath. The harder your heart works, the faster AQ points accumulate.
Researchers found that people reaching at least 25 AQ points per week significantly lowered their risk of lifestyle related diseases. According to the researchers, the strongest health benefits appeared at 100 AQ points or higher.
Click here to read more about AQ.
In a study examining the relationship between AQ and health, researchers analyzed data from more than half a million people. The study found a strong connection between higher AQ scores, better cardiovascular fitness, and improved health outcomes:
Association between Activity Quotient and cause-specific mortality — A prospective cohort study of 0.5 million participants in Asia, Progress in Cardiovascular Diseases, March-April 2025
Exercise and Brain Health
Large studies also suggest exercise benefits the brain in addition to the body.
“Physical health and brain health are closely linked, and cardio fitness is key here as well. Exercise leads to the formation of new brain cells,” said Atefe R. Tari, who is head of a research group at CERG.
Tari helped lead a scientific study on exercise and brain health published last year. The paper became one of the most widely read articles in The Lancet in 2025.
Researchers Push for “Micro Workouts”
Wisløff and Tari are now encouraging Norwegian health authorities to revise the country’s official exercise recommendations, arguing that exercise intensity should receive greater emphasis.
The researchers also wrote the book ‘Mikrotrening’ (in Norwegian), which draws on research reviews showing that brief bursts of high intensity activity may provide greater health benefits than spending many hours each week doing low to moderate intensity exercise. (Captions)
“We need a new Dagfinn Høybråten to get the whole population on board with this,” said Wisløff, referring to the man who was the driver behind the introduction of the smoking ban in Norway.
“In my opinion, Høybråten is the politician who has done the most for public health in Norway since the Second World War,” said Wisløff.
“It usually takes 3 to 5 years to see the effects of implemented measures, and since we have general elections every four years, this is not easy to achieve. This should be a cross-party initiative because it would save Norway 2 to 4 health budgets per year, and could be used for prevention and in areas such as elderly care,” Wisløff said.
Researchers say Norway’s extensive long term health databases make it easier to evaluate how exercise policies affect public health over time.
“Norway could become a pioneer with regard to health benefits from micro workouts,” said Wisløff.
