As summer approaches, many people start thinking about getting back into an exercise routine. While most of us know that physical activity is good for our health, finding the time and motivation to start, and then stick with it, can be a challenge.

Current public health recommendations call for at least 2.5 hours of exercise per week, with 5 hours considered even better. For many people, however, that amount can feel difficult to fit into an already busy schedule.

Research conducted over the past 20 years suggests there may be another option. According to scientists, just 30 minutes of exercise per week can improve health, provided the activity is performed at a high intensity. That works out to about 4.5 minutes per day or roughly 10 minutes every other day. The key is pushing yourself hard enough to become noticeably out of breath.

If you use a heart rate monitor, researchers recommend reaching about 85 percent of your maximum heart rate. But no special device is required. A simple rule of thumb is that you should be able to speak in short phrases, yet be too breathless to sing or carry on a long conversation.

Cardiovascular Fitness Drives Many Health Benefits

“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.

According to Wisløff, even a relatively small amount of vigorous exercise can improve cardiovascular fitness, which is one of the strongest indicators of overall 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 this connection in a 2006 study involving health data from 60,000 people. Since then, numerous large studies from Norway and around the world have reached similar conclusions.

How Often Should You Exercise?

Is one intense 30-minute workout each week enough, or is it better to spread the exercise out?

“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 note that a single workout session that leaves you breathless for several minutes can improve blood pressure and blood sugar regulation for 24–48 hours afterward. Because of these short-term effects, spreading exercise across two to four days each week may provide the greatest overall benefit.

Short Intervals Can Be Highly Effective

Does high intensity exercise mean running at top speed or using maximum resistance 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.

The amount of effort needed varies from person to person. Someone who is less fit may reach the desired intensity with a brisk walk, while others may need more demanding exercise to achieve the same effect.

Fitness Needs Ongoing Maintenance

Can you make up for skipping workouts this week by exercising extra hard 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.

The same principle applies to strength training.

“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.