News release

From: BMJ Group

Timing exercise to match body clock chronotype may lower cardiovascular disease risk

Alignment with ‘eveningness’ or ‘morningness’ lowered risk factors and boosted sleep quality more effectively than mismatched timing

Include chronotype assessment in exercise prescriptions, suggest the researchers

Timing exercise to match body clock chronotype—the natural predisposition to morning or evening alertness—may lower cardiovascular disease risk among those who are already vulnerable, suggests research published in the open access journal Open Heart.

Chronotype alignment boosted sleep quality and lowered risk factors, such as high blood pressure, fasting glucose, and ‘bad’ cholesterol, more effectively than mismatched exercise timing, the trial results indicate.

The findings prompt the researchers to suggest that individual chronotype assessment should be included in exercise prescriptions for those who are at risk of cardiovascular disease.

Exercise lowers the risks of heart disease/stroke and diabetes, and whether someone is naturally a morning lark or a night owl—an innate disposition that affects sleep-wake patterns, hormone secretion, and energy availability across the day—influences exercise performance and adherence, explain the researchers.

But it’s not clear if the benefits of exercise might depend on its timing relative to a person’s chronotype.

To find out, they assessed the chronotypes of 150 people aged between 40 and 60, using the Morningness-Eveningness Questionnaire and 48 hour core body temperature.

All the participants had at least one cardiovascular risk factor, such as high blood pressure, overweight or obesity, and a sedentary lifestyle (no or minimal structured physical activity in the past 3 months).

Participants with a family history of premature cardiovascular disease (58; 43%) were also included. This was defined as affecting a first degree male relative before the age of 55 or a first degree female relative before the age of 65.

They were randomly assigned to exercising at a time that either matched their chronotype  or at a time that didn’t, between 8:00 to 11:00 hours or between 18:00 to 21:00 hours. They were asked to do 5 sessions of supervised moderate intensity aerobic exercise (brisk/treadmill walking), each lasting 40 minutes, every week for 12 weeks.

In all, 134 participants completed all 60 exercise sessions: 70 were morning larks, 34 of whom had been matched to their chronotype; 64 were night owls, 30 of whom had been matched to their chronotype.

Blood pressure, heart rate variability, fasting glucose, VO₂ max (maximal oxygen consumption during exertion), ‘bad’ (LDL) cholesterol levels, and sleep quality were all measured before the start of the trial and 3 days after it finished.

Analysis of the results showed that cardiovascular disease risk factors, aerobic fitness, and sleep quality improved in both groups after 12 weeks.

But matching exercise with chronotype produced larger improvements in blood pressure, autonomic function (involuntary bodily processes, including heart rate), aerobic capacity, metabolic markers, and sleep quality than mismatched exercise.

These improvements were especially noticeable in sleep quality—an increase of 3.4 compared with 1.2 points—and systolic blood pressure—the higher of the two numbers in a reading.

This fell by 10.8 mm Hg in those whose exercise sessions had been matched to their chronotype compared with a drop of 5.5 mm Hg among those whose exercise sessions had been mismatched.

The fall in systolic blood pressure was even larger among those who had high blood pressure to begin with: their systolic blood pressure fell by an average of 13.6 mm Hg compared with 7.1 mm Hg in those whose exercise sessions had been mismatched.

Although improvements were observed across both chronotypes, overall, the effects were larger among morning larks than among night owls.

The researchers acknowledge that the study participants were drawn only from government hospitals in Lahore and that those with intermediate chronotypes were excluded, which may limit the wider applicability of the findings.

But their findings echo those of other studies, they point out: “This study adds to a growing body of evidence suggesting that the timing of exercise when aligned with an individual’s internal biological clock can significantly enhance health outcomes,” they write.

“Aligning exercise with chronotype may entrain peripheral clocks in skeletal muscle, adipose tissue, and vasculature more effectively, enhancing metabolic efficiency and reducing inflammation, both critical factors in cardiometabolic health,” they explain.

And they conclude: “Integrating the principle of ‘chrono-exercise,’ scheduling workouts according to an individual’s internal biological clock, may offer a novel and impactful approach to enhancing outcomes in preventive cardiovascular and metabolic health.”

Commenting on the findings, Dr Rajiv Sankaranarayanan, of the British Cardiovascular Society, which co-owns Open Heart, said: “From a UK perspective, this study’s findings are highly relevant to preventive cardiology within the NHS, where scalable, cost-effective interventions are essential. Incorporating simple chronotype assessment into lifestyle advice could enhance adherence and outcomes, particularly in patients with hypertension or cardiometabolic risk.

“However, before widespread implementation, validation in more diverse, real-world UK populations (including shift workers and multi-ethnic cohorts), is needed. Overall, this study supports a shift toward more personalised, circadian-informed exercise prescriptions in routine cardiovascular care.”