The study, published in the European Journal of Preventive Cardiology, analyzed data from more than 86,000 people who wore activity trackers for seven days. The researchers followed them for six to eight years and recorded any hospital admissions or deaths related to coronary artery disease (CAD) or stroke.

They found that people who exercised in the morning, between 8 and 11 a.m., had the lowest risks of both CAD and stroke, compared to those who exercised at other times of the day. This was true regardless of how much physical activity they did throughout the day or whether they were morning or evening types.

The researchers also found that women who exercised in the early or late morning had 22% and 24% lower risks of CAD, respectively, and those who exercised later in the morning had a 35% lower risk of stroke, compared to the reference group.

The study’s co-author, Gali Albalak, a PhD candidate at Leiden University Medical Center, said that “we all know that physical activity is important to reduce cardiovascular risk, but this study suggests that the timing of when you are physically active also plays an important role.”

How Does Morning Exercise Benefit Your Heart?

The exact mechanisms behind the link between morning exercise and lower cardiovascular risk are not clear, but the researchers have some possible explanations.

One is that morning exercise may help regulate the circadian rhythm, which is the body’s internal clock that controls various biological processes. The circadian rhythm affects blood pressure, heart rate, hormone levels, and inflammation, which are all related to cardiovascular health.

Another possibility is that morning exercise may influence eating behaviors and sleep quality, which can also affect cardiovascular health. For example, exercising in the evening may disrupt sleep patterns or increase appetite, leading to unhealthy food choices or overeating.

The researchers caution that their study does not prove causation, only association, and that more research is needed to confirm their findings and explore the underlying mechanisms. They also note that their study population was mostly white and older adults, so the results may not apply to other groups.

However, they suggest that if people can fit workouts in earlier in the day, they may reap some extra benefits for their heart health. Of course, exercising at any time of the day is better than not exercising at all, so people should find a routine that works best for them and stick to it.