You already move to work that powerful muscle. The time of day can amp up the benefits, found physiology and public health researchers.
Want a Healthier Heart? Exercise at This Hour, Says New Research
Published on Jul. 13, 2025
Nearly 130 million adults in the U.S. have some form of cardiovascular disease, according to 2025 data from the American Heart Association. The rate of heart attacks has significantly decreased over the past six decades, but deaths related to heart failure have increased by 146% and to hypertensive heart disease by 106%, says the Journal of the American Heart Association.
It’s been shown time and again that a combination of lifestyle and dietary choices, including a commitment to regular exercise, can help prevent heart disease. A new study even suggests a time of day for physical activity that could help optimize your heart health.
In April 2025, the medical journal Medicine & Science in Sports & Exercise published a study that investigated whether “‘more rhythmic’ rest-activity patterns would be associated with better cardiorespiratory fitness.” That “rhythmic” behavior was dictated by the typical sleep-wake and activity patterns of older adults. The researchers said this would help lend insight to how severely interruptions to humans’ circadian rhythm, such as from jet lag or working overnight shifts, might affect cardiorespiratory health.
Using data collected by the Study of Muscle, Mobility and Aging, researchers analyzed data from 799 participants averaging 76 years of age. These participants wore wrist-worn accelerometers (devices that measure movement) for seven days. They also underwent a heart and lung stress test and were measured for how much energy they expended relative to their walking effort.
The results suggested that people who exercised earlier in the day—and at the same time daily—experienced the greatest cardiological benefits. This was regardless of the activity they chose or the length of the workout.
The study’s lead author, Karyn Esser, PhD, reflected on these findings to Medical News Today, noting “the timing and reproducibility of the activity are working with our intrinsic circadian clock system to maintain health.”
In other words, the most important part is showing up most every day—notes the American Heart Association: “The key is to do what’s most likely to work consistently for you.”
If you’re still looking to nail down that ideal hour, a 2023 study in Obesity concluded that exercise between 7 and 9 a.m. was linked to a lower body mass index. Another study published in Vascular Health and Risk Management suggested that working out at 7 a.m. could improve blood pressure.
The Mayo Clinic echoes other expert sources in suggesting 30 minutes of moderate activity is a solid target for your health.
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