Oct. 7, 2025, 6:30 PM EDTBy Kaitlin SullivanShort bursts of purposeful activity –– such as walking around the block or lifting small weights –– may be the best way to get in the habit of exercising. Bite-sized bits of exercise also improve heart and muscle fitness, a study published Tuesday in BMJ Sports Medicine found.Less than half of adults in the United States get enough aerobic activity and less than a quarter get the recommended amount of both aerobic and muscle-strengthening exercise. “When people are asked why they don’t exercise, the answers are almost always the same, no time and no motivation,” Miguel Ángel Rodríguez, a doctoral student in clinical research at the University of Oviedo in Spain, who led the study, said in an email.Rodríguez and his team measured how brief bouts of exercise spread throughout the day –– which he calls exercise snacks –– affected cardiorespiratory and muscular fitness, as well as blood pressure and body composition in adults who did not regularly exercise. The team compiled data from seven randomized clinical trials that included people ages 18 to 80. There were more than 400 inactive people across the study, about 70% of whom women.What’s an effective exercise snack? An exercise snack was defined as a bout of vigorous physical activity that lasted less than five minutes. The activity had to be done at least two times a day on at least three days per week, for four to 12 weeks. The exercise was short and deliberate, such as climbing flights of stairs for the purpose of exercise. Stair-climbing was most common in adults younger than 65, while exercise, including tai chi, that strengthened lower body muscles was more common in older adults. They found that in adults younger than 65, these small acts of physical activity significantly improved cardiorespiratory fitness. For older adults –– those 65 and older –– exercise snacks significantly improved muscular endurance. People were also extremely likely to adhere to these small bouts of exercise –– about 91% of adults and 83% of older adults routinely engaged in them.“The biggest benefits happen at the very beginning, when someone goes from being inactive to a little bit active. That’s where exercise snacks can really help,” Rodríguez said. The study did have limitations, including the fact that the seven clinical trials they included used different methods to collect data, and had people exercise for different lengths of time between four and 12 weeks. For this reason, some of the benefits of moving may have been masked.For example, contrary to what past research has found, the new study found that short bursts of activity did not appear to have an effect on cardiometabolic health, such as body composition, blood pressure and blood lipids. Lipids are fatty substances, including LDL (bad cholesterol), HDL (good cholesterol) and triglycerides, that perform critical functions in the body but can be harmful if they build up in the blood.“It was surprising that they didn’t find any improvement in those other markers of cardiometabolic health because most other studies have,” said Carol Ewing Garber, director of both the Applied Physiology Laboratory and the EXerT Clinic at the Columbia University Teachers College, who wasn’t involved in the study. Cardiorespiratory health is a measure of how well the heart and lungs deliver oxygen to the muscles during exercise and predicts a person’s risk of developing heart disease and diabetes. The new study showed short bursts of exercises improved cardiorespiratory fitness.At the very least, getting small amounts of deliberate exercise on a regular basis will make everyday tasks, such as hauling groceries or making the bed, much easier, Garber said. “Most of us could probably find these five-minute bouts of time in our day, to walk around the building we work in, or up and down the stairs. We just don’t think we can,” she said. Short workouts create changes in the bodyPerhaps the biggest benefit of starting an exercise snack routine is that it can help people who are inactive build upon these small changes, said Dr. Tamanna Singh, director of the Sports Cardiology Center at Cleveland Clinic. “If you do the same snack, for the same amount of time, at the same frequency, your body will get used to it. The body needs a challenge,” she said. “The exercise snack can be the start of a foundation for more intense exercise.”Short workouts create key changes in the body that make intensifying workouts easier, Singh added. Within a couple of weeks of getting exercise, aerobic activity initiates cellular changes that increase the amount of plasma in the blood, which allows the blood to deliver more oxygen to the muscles and lengthens endurance. Even small amounts of aerobic activity strengthens the network of tiny blood vessels, called capillaries, that remove waste from muscles. Consistent activity also improves the amount of energy cells can provide, she added. These changes make it easier to exercise for longer periods of time or at a higher intensity. “The main takeaway here is that anything is better than nothing, but that does not mean you should just get three minutes of exercise,” Singh said. “Use that as a base, hopefully these exercise snacks will make people want to have an exercise meal.”Kaitlin SullivanKaitlin Sullivan is a contributor for NBCNews.com who has worked with NBC News Investigations. She reports on health, science and the environment and is a graduate of the Craig Newmark Graduate School of Journalism at City University of New York.