Clocking the standard 150 minutes of exercise a week may only go so far for heart protection.

A large observational study, published online in the British Journal of Sports Medicine, found adults may need 560 to 610 minutes of moderate-to-vigorous physical activity each week to see a major reduction in the risk of heart attack and stroke.

That is about 3 to 4 times the current public health recommendation of at least 150 minutes a week. Moderate-to-vigorous activity includes brisk walking, running and cycling.

Researchers at Macao Polytechnic University in China analysed data from 17,088 people enrolled in the UK Biobank study between 2013 and 2015.

Participants had an average age of 57. Of the group, 56 percent were female and 96 percent were white.

Each person wore a wrist device for seven consecutive days to record typical physical activity. They also completed a cycling test used to estimate VO2 max, a common measure of cardiorespiratory fitness.

The researchers also considered smoking, alcohol use, self-rated health, diet, body mass index, resting heart rate and blood pressure.

Over an average follow-up of 7.8 years, the researchers recorded 1,233 cardiovascular events. These included 874 cases of atrial fibrillation, 156 myocardial infarctions, 111 cases of heart failure and 92 strokes.

Adults who met the 150-minute guideline had a modest 8 to 9 percent lower cardiovascular risk, and that association was similar across all fitness levels.

But the study found that what researchers defined as substantial protection, a reduction in risk of more than 30 percent, was linked to 560 to 610 minutes of moderate-to-vigorous activity a week. Only 12 percent of participants reached that level.

The study also found people with lower fitness levels may need slightly more exercise to get similar benefits.

For a 20 percent reduction in cardiovascular event risk, people with the lowest fitness levels were associated with 370 minutes of moderate-to-vigorous exercise a week. People with the highest fitness levels needed about 340 minutes a week for the same reduction.

People with the lowest fitness levels needed about 30 to 50 extra minutes of exercise a week compared with highly fit participants, according to the study.

The researchers say, “This finding highlights the steeper challenge faced by deconditioned populations.”

The researchers said the findings suggest the current one-size-fits-all approach to exercise advice may need rethinking, with future guidance potentially tailored to a person’s fitness level.

But they also said current exercise guidelines still work as a reliable minimum level for cardiovascular protection.

Because the research was observational, it cannot show that higher exercise levels directly caused the lower cardiovascular risk.

The researchers also said participants may have been healthier and fitter than the general population. Cardiorespiratory fitness was estimated rather than measured directly, and the analysis did not assess sedentary time or lower-intensity exercise.

“Future guidelines may need to differentiate between the minimal moderate to vigorous exercise volume required for a basic safety margin and the substantially higher volumes necessary for optimal cardiovascular risk reduction,” they conclude.

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