Andrea Metcalf by Andrea Metcalf

ExerciseHow many days a week do you need to work out? Can you get all the health benefits from one weekly workout lasting more than two hours as you can in daily 20-minute exercise sessions?

A new study from Queen’s University, Canada, looked at how the body reacts to working out once a week compared to several times a week, and how exercise frequency affects health risks.

According to the World Health Organization’s current physical-activity guidelines, adults need to accumulate at least 150 minutes of moderate-to-vigorous physical activity (MVPA) throughout the week in bouts of at least 10 minutes or more. The U.S. Department of Health and Human Services, however, urges at least 30 minutes of daily MVPA. Given the lack of research to clearly demonstrate the optimal frequency of exercise (and hence, the differing guidelines), the research team from Queen’s University set out to find the answer.

A cross-section of 2,324 adults, ages 18-64 years, were recruited to participate in the study. Subjects were divided into two groups—the dailies and the intermittents—and were each given accelerometers to track their activity for one week. The dailies (those who regularly exercised) were assigned to five days a week of physical activity, while the intermittents (those who did not participate in regular exercise programs) were instructed to exercise one to four days a week.  Both groups were required accumulate at least 150 minutes of MVPA for the week.  

Researchers were also interested in the association between the frequency of physical activity throughout the week and the prevalence of metabolic syndrome (MetS) in physically active adults. At the end of the week, each participant’s risk of MetS was measured by blood biomarkers, and researchers found that the more frequent group had lower risks than those who exercised intermittently. However, after adjusting the amount of MVPA, the difference in risk of MetS was less significant.

It is important to note that the short-term nature of this study makes it difficult to draw long-term conclusions about how frequency of exercise affects health conditions such as MetS. Although there is considerable evidence suggesting that any exercise is better than none, it is not advisable to limit exercise to one long session per week in the hopes that that long-term health benefits will result. A myriad of factors should be considered when determining exercise frequency, including time constraints and adherence, as well as the potential benefits associated with more frequent exercise, such as stress reduction and mental stimulation.

Cedric X. Bryant, Ph.D., ACE’s Chief Science Officer, adds that the take-home message of this study should be to strive to accumulate at least 150 minutes of physical activity each week, keeping in mind that regular patterns of activity— specifically at least five days per week—will produce better health outcomes and ultimately greater long-term adherence.