Working out between 7 and 8 AM is way better for your heart than exercising at any other time.
March 19, 2026
Original Paper
Cardiometabolic health and the timing of habitual exercise in the All of Us Research Program
medRxiv · 10.64898/2026.03.16.26348509
The Takeaway
By analyzing a year's worth of minute-level heart rate data, researchers found that habitual morning exercise is linked to a 31% lower risk of coronary artery disease. This benefit was independent of the total volume of exercise, suggesting that the body's internal clock dictates how physical activity impacts heart health.
From the abstract
While the cardiometabolic benefits of exercise volume and intensity are well established, the clinical significance of exercise timing remains poorly understood, largely due to the limitations of short term accelerometry. We leveraged minute level heart rate data from 14,489 participants from the All of Us Research Program to define habitual exercise timing over a one year period. Compared to daytime exercise, habitual morning exercise was associated with lower odds of coronary artery disease (O