If you’re exercising regularly but not seeing the heart health results you expected, the problem might not be what you’re doing but instead when you’re doing it.
Recent research published in the journal Open Heart found that people who scheduled their workouts to match their natural body clocks, or chronotypes, showed significantly greater improvements in blood pressure, cholesterol and sleep quality than those who exercised at mismatched times.
The randomized controlled trial included over 130 adults ages 40 to 60, all of whom had at least one cardiovascular risk factor such as high blood pressure, excess weight or a sedentary lifestyle.
Researchers assessed each participant’s chronotype using a questionnaire and 48-hour core body temperature monitoring. Then they assigned participants to exercise at a time of day that was either in sync with their chronotype or against it. All participants did five 40-minute sessions of moderate aerobic exercise per week for 12 weeks.
Your chronotype is your underlying circadian rhythm that determines your sleep-wake patterns, hormone levels and energy availability throughout the day. Researchers generally put people into two broad categories: “morning larks,” who naturally wake early and feel most alert in the morning, and “night owls,” who hit their stride later in the day.
For the study, morning larks who were matched to a time that suited their chronotype exercised between 8 and 11 a.m.; night owls matched to a suitable time exercised between 6 and 9 p.m.
Both groups improved after 12 weeks, but the chronotype-matched group pulled ahead on nearly every measure:
Systolic blood pressure (the top number in a blood pressure reading) dropped by nearly twice as much in the matched group (10.8 mm Hg) compared to the mismatched group (5.5 mm Hg).
Among participants with high blood pressure, the matched group saw systolic pressure fall by nearly twice as much (an average of 13.6 mm Hg) compared to the mismatched exercisers (7.1 mm Hg).
Sleep quality improved by 3.4 points in the matched group versus 1.2 points in the mismatched group.
Improvements in aerobic fitness, heart rate variability, fasting glucose and LDL cholesterol (aka “bad” cholesterol) were also greater in the matched group. Morning larks showed somewhat larger overall gains than night owls.
Why timing may matter so much
The researchers say that exercising in sync with your internal clock may help the body’s peripheral clocks — found in muscle, fat tissue and blood vessels — run more efficiently, reducing inflammation and improving metabolic function. Both metabolism and inflammation are closely linked to heart health.
They call this concept “chrono-exercise” and suggest it could offer a practical, drug-free approach to preventive heart care.
Dr. Rajiv Sankaranarayanan of the British Cardiovascular Society says the results could mean better interventions for at-risk patients, noting in a summary of the finding:
“Incorporating simple chronotype assessment into lifestyle advice could enhance adherence and outcomes, particularly in patients with hypertension or cardiometabolic risk. … Overall, this study supports a shift toward more personalized, circadian-informed exercise prescriptions in routine cardiovascular care.”
He also notes that larger, more diverse studies are needed before the approach becomes standard clinical practice.
Still, if you’re at risk for heart disease, scheduling your workouts according to your chronotype may make your exercise routine more effective.
For more on keeping your cardiac health in line, see “10 of the Worst Possible Foods for Your Heart Health.”
