Sitting too much may be aging your heart — even if you’re meeting daily exercise guidelines, according to new research published in PLOS One. Led by Chandra Reynolds, a professor of psychology and neuroscience at the University of Colorado Boulder, the study found that prolonged periods of sitting could increase “heart age” even among young, active adults.

“A quick walk after work may not be enough to offset the health dangers of sitting,” Reynolds warned.

This research drew data from over a thousand participants, mostly current or former residents of Colorado, aged 28 to 49. The team was particularly interested in younger adults, explained study co-author Ryan Bruellman, a PhD candidate at the University of California, Riverside. “Young adults tend to think they are impervious to the impacts of aging. But what you do during this critical time of life matters,” Bruellman said.

Most participants sat for about nine hours a day on average, with exercise levels ranging from 80 to 160 minutes of moderate activity per week and under 135 minutes of vigorous exercise weekly. Using two critical indicators of heart health — cholesterol and body mass index (BMI) — the researchers determined each participant’s “heart age,” a measure that reflects the aging of the heart and cardiovascular system.

Their findings were stark: the more participants sat, the older their heart age appeared, regardless of moderate exercise levels. While 20 minutes of daily “moderate” exercise aligned with general health recommendations, it didn’t counteract the adverse effects of prolonged sitting. In contrast, adding around 30 minutes of vigorous exercise, like running or cycling, did help somewhat — but even this didn’t entirely reverse the negative impacts.

In analyzing twins within the study, the researchers found that substituting sitting time with exercise produced better results for improving cholesterol than merely adding exercise to a day dominated by sitting.

For people who spend much of the day seated, Reynolds’ team suggests small lifestyle changes to counteract the risks: try using a standing desk, aim for 30 minutes of vigorous exercise daily, or commit to intense workouts on the weekends. These adjustments, while small, may go a long way in protecting heart health — particularly for younger individuals.

So, next time you think about sitting back and relaxing, consider standing up and moving — your heart will thank you for it.