Exercising at any time of day protects against early death from cardiovascular disease or cancer.

No news there, right?

But what time of day does exercise work best to protect your heart?

A large new study involving more than 92,000 people came up with a surprise answer.

People who engage in moderate to vigorous exercise between 11am and 5pm have “lower risks of all-cause and cardiovascular disease mortality”.

These protective associations were more pronounced “among the elderly, males, less physically active participants, or those with pre-existing cardiovascular diseases”.

This is great, useful news for people feeling discouraged by age or compromised health.

The time-of-day factor

As we’ve previously reported – see here and here – exercising at different times of day carries different benefits.

In the morning, women especially tend to lose more body fat. In the evening they gain more upper-body strength and power.

For men, an evening workout significantly improves blood pressure, cholesterol levels, blood sugar levels.

A 2022 study also found improvements in the percentage of fat they burned for energy, along with a bigger drop in feelings of fatigue.

Increasingly of interest is when exercise works best to protect the heart from disease.

This occurs in tandem with boosting mood, and quality of sleep.

These three things significantly impact the likelihood of dying prematurely.

The new study

Researchers analysed data from 92,139 men and women who had joined the UK Biobank, a health study of adults in the United Kingdom.

The participants woren activity trackers for a week, measuring when and how intensely they worked out.

This allowed the researchers to group the participants into those who worked out in the morning, those at midday and afternoon, those in the evening and those who spread their workouts out during the day.

They were also grouped according to age, sex, exercise intensity, pre-existing cardiovascular disease and obesity.

After seven years about 3000 (or three per cent) of the participants had died, about 1,000 from heart disease and 1800 from cancer, health records showed.

People who worked out in the mid-afternoon (11am to 5pm) had a lower risk of dying from heart disease and other causes (except cancer). Those who regularly changed their workout schedules also had this benefit.

Why is this so?

The researchers, from the Guangdong Cardiovascular Institute in China, said the afternoon is, statistically, the time of day when people are least likely to experience a heart attack.

The most likely time for a cardiovascular event is the morning.

Exercising in the evening may disrupt sleep. Which is bad for the heart.

Circadian rhythms also play a part here – they tend to peak between 2pm and 6pm. Core body temperature tends to be at its highest at this time. It’s thought that the body is at its best for physical performance.

It also may be the healthiest time of day to prompt the release of melatonin and shift one’s sleep patterns so that you’ll nod off earlier.