The Best Time to Exercise for Heart Health

Many people exercise regularly but still don’t see the health improvements they expect. If you are exercising regularly but not noticing the expected improvements in your heart health, the issue may not be your workout routine itself, but rather the time of day you are exercising.

A recent study published in the medical journal Open Heart suggests that the timing of physical activity plays an important role in how effectively it benefits cardiovascular health. Researchers found that individuals who scheduled their workouts according to their natural body clock—known as their chronotype—experienced significantly better health improvements compared to those who exercised at times that did not match their biological rhythm.

The study was a randomized controlled trial involving more than 130 adults between the ages of 40 and 60. All participants had at least one risk factor for cardiovascular disease, such as high blood pressure, excess body weight, or a sedentary lifestyle. This made them an ideal group to test how exercise timing might influence heart health outcomes.

To determine each participant’s chronotype, researchers used detailed questionnaires and monitored core body temperature over a 48-hour period. Based on the results, participants were categorized into two main groups:

• Morning larks: People who naturally feel more energetic earlier in the day.

• Night owls: People who are more active and alert later in the evening.

Morning larks tend to wake up early and feel most energetic in the first half of the day, while night owls feel more alert and physically capable in the later hours of the afternoon or evening. These natural differences are driven by the body’s internal circadian rhythm, which regulates sleep, hormone release, energy levels, and overall biological activity throughout a 24-hour cycle.

In the study, participants were assigned exercise schedules based on whether their workout time aligned with or conflicted with their chronotype. Morning-type participants exercised between 8:00 a.m. and 11:00 a.m., while evening-type participants trained between 6:00 p.m. and 9:00 p.m. All individuals completed five sessions per week of moderate aerobic exercise, each lasting about 40 minutes, over a 12-week period.

Although both groups showed health improvements after the program, the group whose exercise timing matched their natural body clock achieved noticeably better results. One of the most significant differences was seen in blood pressure. Participants in the matched group experienced a much greater reduction in systolic blood pressure—the top number in a blood pressure reading—compared to those exercising at mismatched times.

For individuals with existing high blood pressure, the improvement was even more pronounced, suggesting that exercise timing may be especially important for those already at risk of heart disease.

Sleep quality also improved more in the chronotype-aligned group. Participants reported deeper and more restorative sleep, which is a key factor in heart health and overall recovery. In addition, other important health markers such as aerobic fitness, cholesterol levels (particularly LDL or “bad” cholesterol), fasting glucose, and heart rate variability showed greater improvement when workouts were aligned with natural body rhythms.

Researchers believe these differences occur because exercising in sync with the body’s internal clock helps regulate smaller biological “peripheral clocks” located in tissues such as muscles, fat, and blood vessels. When these systems are better synchronized, the body may experience reduced inflammation and improved metabolic efficiency, both of which are strongly linked to better cardiovascular health.

This idea is part of an emerging concept known as “chrono-exercise,” which focuses on optimizing physical activity based on circadian biology. Scientists suggest that this approach could become a simple, non-drug method to help prevent or manage heart-related conditions in the future.

Experts, including cardiovascular specialists, note that while the findings are promising, more large-scale and diverse studies are needed before chrono-exercise becomes a standard part of medical recommendations. However, early evidence suggests that personalized exercise timing could improve adherence and outcomes, especially for people with hypertension or metabolic risk factors.

In practical terms, this means that individuals may benefit from paying attention to their natural energy patterns. Morning-oriented people might gain more from exercising earlier in the day, while evening-oriented individuals may see better results from later workouts. Matching exercise time with personal biological rhythm could make physical activity more effective without requiring any major changes in intensity or duration.

Overall, the study highlights an important shift in understanding fitness and health—not just focusing on how much or how hard we exercise, but also on when we do it