Physical activity remains the cornerstone of cardiovascular prevention, but the time of day when we move may be just as important as the effort itself. The link between morning exercise and cardiometabolic health is gaining attention from specialists, as our biological rhythms influence how the body benefits from movement. The question is now being clarified through connected devices capable of tracking every minute of effort over long periods.
Thousands of connected bracelets were scrutinized for a year
To better understand the connection between the time of exercise and heart health, a team from the University of Massachusetts analyzed data from over 14,000 volunteers in the national All of Us program. Each participant wore a Fitbit bracelet recording their heart rate minute by minute. Researchers were able to identify each episode of prolonged effort, defined as at least fifteen consecutive minutes of high heart rate.
The tracking spanned an entire year, representing a colossal volume of data. This approach differed from traditional surveys where participants self-reported their activity levels. Here, the measurement was objective and continuous, reducing memory biases.
Volunteers were classified based on the time slot they most frequently exercised. Factors considered for adjustment included age, gender, income, duration of sleep, alcohol consumption, and smoking. In other words, the comparison was not just morning versus evening but took into account each individual’s overall lifestyle.
Less diabetes, obesity, and coronary diseases
The results presented at the annual American College of Cardiology conference in New Orleans were striking. Individuals who regularly exercised in the morning displayed a 31% lower risk of coronary heart disease compared to those who worked out later in the day. Additionally, the risk of type 2 diabetes decreased by 30%, obesity by 35%, and high blood pressure by 18%.
The most protective time slot was between 7 am and 8 am. However, benefits existed for any activity done in the early morning. Hyperlipidemia, an excess of fats in the blood, also decreased by 21%. These associations remained significant even after adjusting for total daily physical activity volume.
In simple terms, it’s not just the amount of exercise that matters, but also the timing. Connected devices now allow for studying these nuances on an unprecedented scale, as emphasized by Prem Patel from the University of Massachusetts.
A strong signal, but not yet conclusive evidence
Despite the significant figures, the authors urge caution. The study is observational, meaning it shows a statistical link without proving that morning exercise causes the reduced risk. Several hypotheses are being considered to explain this advantage, such as the influence of circadian rhythms on hormone secretion. Additionally, morning exercisers may adopt other favorable habits like regular sleep or a balanced diet, which can also impact the results.
Nevertheless, the signal remains robust and aligns with previous observations on the role of the biological clock in metabolism. The next step will involve conducting controlled trials where volunteers will be assigned to specific time slots to determine if the link is truly causal. In the meantime, fitting in a jog before breakfast costs nothing and could be well worth it.
