April 29, 2026, 3:55 pm | Read time: 6 minutes
The body’s biorhythm, also known as the internal clock, regulates numerous processes. It affects sleep, alertness, and concentration—and also training success. Research suggests that biorhythm may help determine the most health-beneficial time of day for exercise. FITBOOK delves into the findings of this recent study.
When You Train Matters Too
Regular exercise supports heart and vascular health. However, the positive effects seem to depend not only on how often or intensely one trains but also on the time of day. Numerous studies have explored this topic. FITBOOK reported on a study suggesting that training between 11 a.m. and 5 p.m. might be particularly beneficial for life expectancy.1 However, personal biorhythm was not considered. A new study suggests that this could influence training success more than previously thought.2
Study on the Influence of Biorhythm on Training Success
The basis of the randomized study from Pakistan is the fact that cardiovascular diseases are among the leading causes of death worldwide. Measures such as regular exercise, weight reduction, and good sleep can reduce cardiovascular risk. The researchers wanted to investigate whether training success could be further enhanced by adjusting training times to personal biorhythm.
The study was conducted between January and June 2025 in Lahore, Pakistan. Initially, 150 physically inactive adults aged 40 to 60 participated, all of whom had at least one known risk factor for cardiovascular diseases. This could be severe overweight, early-stage hypertension, elevated fasting blood sugar, or a family history. Only 134 participants completed the study.
Study Details
The participants’ personal chronotype was first assessed using the Morningness-Eveningness Questionnaire. This scientifically validated questionnaire considers preferred sleep and wake times, energy levels at different times of the day, and subjective performance in the morning and evening. Based on the responses, a total score is calculated, allowing classification into the respective chronotype category. Additionally, the researchers conducted a 48-hour temperature measurement to objectively confirm the biological rhythm.
Exercise Component
Participants were randomly divided into two groups. The first group trained according to their determined individual chronotype. Specifically, morning people—often called larks—trained in the morning, while evening types, or owls, trained in the evening. In the second group, the principle was reversed: participants trained against their biorhythm.
The program lasted twelve weeks and included five training sessions per week, each lasting 40 minutes at moderate intensity. The workouts mostly consisted of brisk walking or treadmill training under supervision.
Study Results
The evaluation showed that both groups generally benefited from regular training. However, significantly stronger training successes were observed in participants who adjusted their workouts to their biorhythm. For instance, systolic blood pressure in this group decreased by an average of 10.8 mmHg, while it only dropped by about 5.5 mmHg in the comparison group. Similar differences were seen in diastolic blood pressure: –7.3 mmHg compared to 3.3 mmHg.
Also interesting: Why both blood pressure values matter
Heart rate variability—a measure of how flexibly the heart responds to stress and how well the autonomic nervous system is regulated—also improved more significantly in the adjusted group. Endurance fitness showed an advantage as well: the estimated maximum oxygen uptake increased by 4.4 mL/kg/min compared to 2.3 mL/kg/min in the comparison group. Additionally, treadmill time and achieved stress levels improved more.
A similar pattern was observed in metabolism. Both LDL cholesterol and fasting blood sugar decreased more in the adjusted group. Participants also reported significantly better sleep quality.
Researchers’ Evaluation of the Results
The results surprised the study authors, particularly due to the significant extent of the differences. Arsalan Tariq, a participating researcher, explained to FITBOOK that chronotype-adjusted training achieved “almost twice the reductions” in blood pressure compared to sessions at inappropriate times of day. Consistent advantages were also seen in fitness, metabolic parameters, and sleep quality. This suggests that timing plays a larger role than previously assumed.
For practical application, the authors derive a clear recommendation: Regular exercise remains central but can gain additional effectiveness when timed to match the biorhythm. “This simple step can further improve blood pressure, metabolism, and sleep quality,” said Dr. Tariq.
The researchers see an interplay of physiological and behavioral factors as an explanation. On one hand, training sessions in sync with the biorhythm could positively influence hormonal and metabolic processes. On the other hand, the study showed higher training adherence in the adjusted group. Both together likely explain the stronger effects and more pronounced training success.
Is the Clock the Enemy of Our Sleep?
Early, Late, or Normal? Take the Chronotype Test!
Potential Significance of the Study
Biorhythm and training success—there may be a stronger connection than previously thought. Training tailored to one’s chronotype could be an underestimated lever in the prevention and treatment of cardiovascular diseases. This is particularly relevant in relation to blood pressure, as even moderate reductions can significantly lower the long-term risk of heart attack, stroke, and other cardiovascular diseases.
For many people, practicality plays a crucial role. Lack of time, fatigue, or lack of motivation make regular exercise difficult. If training is easier at an individually suitable time of day, it could increase regularity. Indeed, the study authors noted more consistent adherence to training guidelines in the adjusted group.
Finally, the improvements in sleep quality and metabolic values observed in the study are potentially relevant. Poor sleep, elevated blood sugar levels, and unfavorable blood lipid levels often occur together and further increase the risk of chronic diseases.
Limitations
The study duration was only twelve weeks. It is unclear whether the observed benefits will persist long-term. Additionally, all participants were from Lahore. The results cannot be easily generalized to other countries, age groups, or populations. Furthermore, individuals with a medium chronotype—those who do not clearly identify as morning or evening types—were excluded from the study.
A complete blinding was hardly possible in a training study. Participants knew when they were training, which could have influenced behavior and motivation. Moreover, endurance performance was not directly measured in the lab but estimated using a standardized stress test, which could lead to inaccuracies.