While some people can spring out of bed at six in the morning and go straight into their day, others prefer to wake up later as they’re most productive in the afternoon or evening. This difference is due to your chronotype – the biological tendency to prefer certain times of day for sleep, waking and activity.
But these aren’t the only factors affected by your chronotype. A growing body of research also suggests that your chronotype can affect the benefits you see from exercise.
People who naturally rise early and feel sharpest in the morning are “early chronotypes”, whereas those who prefer to wake later and function better in the afternoon or evening are “late chronotypes”. People who fall in between are “intermediate chronotypes”.
Your chronotype is determined by your circadian rhythms – the body’s natural daily cycles that repeat around every 24 hours. Although these are strongly influenced by our environment, they function even without external cues such as daylight and food. These rhythms affect our physiology, behaviour and health.
Our circadian rhythms are controlled by the body’s circadian system, which is made up of tiny biological clocks composed of proteins, which are found in organs and tissues. These clocks rely on genes that help coordinate when different processes happen, such as when we feel alert or sleepy.
The circadian system also influences many other bodily functions, including blood pressure, heart rate, blood sugar regulation and blood vessel function. As these factors are also affected by physical activity, this may explain why aligning your workouts to your natural chronotype can be beneficial.
Some studies support this, suggesting that the time of day people exercise can influence health outcomes – including cardiovascular fitness and reducing the risk of cardiovascular disease, obesity and some cancers.
However, as these were observational studies (which only show associations rather than cause and effect), they can’t definitively prove that the findings were solely caused by the timing of the exercise.
But a recent randomised controlled trial has investigated whether aligning workouts with chronotype could enhance the benefits of exercise. The researchers specifically looked at people who were at risk of cardiovascular disease.
Participants were grouped according to their chronotype, which was measured using a specialist questionnaire. Morning types exercised between 8–11am and evening types exercised between 6-9pm. A third group exercised at the opposite time to their chronotype (morning types in the evening and evening types in the morning).
Participants whose exercise was aligned with their chronotype experienced greater improvements in blood pressure, aerobic fitness, blood glucose, cholesterol and sleep than participants whose training times were misaligned with their chronotype.
But though these improvements show that timing exercise to your chronotype can enhance its health benefits, there are a couple of important nuances.
Even the group that exercised at the supposedly wrong time still experienced health benefits, showing that exercise is beneficial even when it doesn’t align with your chronotype. The study also did not include intermediate chronotypes, who make up around 60% of the adult population. For these people, the timing of exercise may be less important.
Based on the available evidence, exercise timing appears to be a meaningful consideration, particularly for people who are strong morning or evening chronotypes.
Beyond your chronotype
So how do you know your chronotype?
Most people have an intuitive sense of this based on when they naturally prefer to sleep and wake. However, work schedules and care-giving responsibilities often force us into routines that conflict with our chronotype. Over time, this makes it harder to be sure of your chronotype.
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For this reason, researchers developed a questionnaire to help you determine your chronotype. The 19 questions include what time you feel you’re at your peak and how easy you find it to wake up in the morning.
Once you have a clearer sense of your chronotype, you can start thinking about when to schedule your training.
However, chronotype isn’t the only factor that can affect training and how you respond to exercise. This is good news for those who may not be able to align workouts with their chronotype.
For instance, body temperature usually peaks in the afternoon regardless of chronotype, which enhances muscle function. This is why strength, speed and coordination tends to be best in the afternoon, making it a prime window for resistance training and technical practice for most people.
Habitual training time can also shift performance over time as the body adapts to the time you regularly train. So even if you’re naturally a night owl, consistent morning training may eventually make you perform better at that time.
Another critical factor to consider when deciding when to workout is sleep.
If you haven’t slept well the night before, research suggests it’s better to exercise earlier in the day, regardless of your chronotype. This is because the drive to sleep, known as “sleep pressure”, builds steadily from the moment you wake up and peaks just before you fall asleep. By evening, growing sleep pressure makes exercise feel harder and can impair your performance.
Exercising late in the evening can also reduce sleep quality, particularly when the session is intense. As a general rule, leave at least a two-hour gap between exercise and bedtime.
There’s no single best time to exercise that works for everyone. While the evidence on the long-term health benefits of matching exercise time to chronotype is growing, some principles apply broadly.
Peak performance varies by chronotype, and matching your workout time to yours may help you train harder and achieve better health benefits. However, any exercise is better than none – regardless of timing.
If you’re a night owl but can only train in the morning, a warm-up is essential. Wear extra clothing and start with 10-15 minutes of light aerobic activity to gradually increase body temperature and increase alertness.
If evenings are your only option, opt for moderate or low-intensity activities (such as yoga or a jog) to avoid disrupting sleep.
Paul Hough does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
