Short Activity Breaks and HIIT Combo Boosts Heart Health in Sedentary Adults

Rockville, Md. (April 7, 2025)—Short activity breaks throughout the day together with high-intensity interval training (HIIT) every other day can counteract negative changes in heart health associated with a sedentary lifestyle. The study is published in the Journal of Applied Physiology and has been chosen as an APSselect article for April. 

In 2020, the World Health Organization updated its physical activity guidelines to add recommendations that people limit sedentary time and break up prolonged periods of sitting regularly. These additions were important, as studies show that people working in an office setting spend approximately 80% of their workday sitting, which has significant health consequences.

Lack of physical activity is linked to increased risk and occurrence of diabetes and cardiovascular disease. Exercise has been found to lower these risks. A new study aimed to learn if limiting sedentary time was enough to reduce the risks or if needed to be in addition to adding regular exercise for better metabolic and heart health. 

A small group of adult volunteers between the ages of 22 and 50 participated in three trial conditions, each lasting two weeks.  

• In the HIIT condition, the volunteers performed 10 sets of one-minute intervals at 85% to 90% maximum heart rate on a treadmill. They engaged in the HIIT routine on alternate weekdays for a total of six sessions. 
• In the interruption condition, the volunteers walked for two and a half minutes every hour to represent a light-intensity interruption of sitting. They performed this intervention for 12 hours each weekday.
• In the combined condition, the volunteers participated in both exercise conditions. The rest of the day was spent sedentary, with limited activity such as working or studying.

Throughout the trial, the participants were asked to limit their daily step count to less than 5,000 other than the exercise regimens. They wore continuous glucose monitoring devices and underwent testing for blood flow, arterial stiffness and cardiorespiratory fitness.

Some of the findings included:

• Significant increases in blood flow after the combined condition.
• Increased VO2max (maximum amount of oxygen the body uses during exercise) after the combined condition compared to interruption alone.

In contrast to previous lab-based studies, there were no significant differences in glucose or cholesterol levels with any condition.

In addition, a follow-up survey of the volunteers revealed they found the combination of HIIT and short activity breaks “the most enjoyable, beneficial to energy levels, productivity and overall health” compared to either activity on its own. Although the volunteers reported that they would most like to incorporate the combined condition into their daily schedules, they were unsure if they would be able to.

“The findings of our study showed that the combination of structured exercise with hourly breaks involving light-intensity physical activity led to the greatest improvements in cardiorespiratory fitness and endothelial function,” when compared with either type of exercise alone, the researchers wrote. The research team encourages people to prioritize participating in both forms of exercise on a regular basis to reap the most benefit. 

Read the full article, “Low-intensity Activity Breaks Combined with Alternate Day Interval Training Mitigate Cardiovascular Effects of Sedentary Behavior.” It is highlighted as one of this month’s “best of the best” as part of the American Physiological Society’s APSselect program. Read this month’s selected research articles.   

NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact APS Media Relations or call 301.634.7314. Find more research highlights in our Newsroom.   

Physiology is a broad area of scientific inquiry that focuses on how molecules, cells, tissues and organs function in health and disease. The American Physiological Society connects a global, multidisciplinary community of more than 10,000 biomedical scientists and educators as part of its mission to advance scientific discovery, understand life and improve health. The Society drives collaboration and spotlights scientific discoveries through its 16 scholarly journals and programming that support researchers and educators in their work.