560-610 minutes of exercise a week needed for substantial heart benefits

Adults should aim to do between 560 and 610 minutes a week of moderate to vigorous physical activity to achieve a substantial reduction in the risk of heart attacks and stroke, suggest the findings of an observational study published online in the British Journal of Sports Medicine.

This is between 3-4 times higher than the current public health recommendation that adults do at least 150 minutes a week of moderate to vigorous physical exercise such as brisk walking, running or cycling.

People who are less fit need to do slightly more exercise than those who are very fit to get the same cardiovascular benefits, the study suggests.

The researchers say that the current one-size fits-all advice on exercise may need to be changed and replaced with personalised targets according to an individual’s fitness level.

Cardiorespiratory fitness varies greatly and is a strong predictor of cardiovascular health. Low cardiorespiratory fitness is strongly associated with an increased risk of heart attacks, strokes and early death, the researchers point out.

A simple way to assess cardiorespiratory fitness is by measuring VO2 max - the maximum rate of oxygen the body consumes and uses during intense exercise. This measures how efficiently the heart, lungs and muscles deliver and use oxygen.

Researchers from Macao Polytechnic University, China, set out to look at how both exercise levels and cardiorespiratory fitness, as measured by VO2 max, affected the risk of cardiovascular disease.

The study included data from 17 088 people who were taking part in a UK Biobank study between 2013 and 2015. The average age was 57 years and 56% were female and 96% were white.

The study participants wore a device on their wrist for seven consecutive days to record their typical exercise levels and had completed a cycle test to measure their estimated VO2 max.

Data on smoking status, alcohol intake, self-related health and diet, body mass index, resting heart rate and blood pressure were also included in the analysis.

During an average follow up period of 7.8 years, there were 1233 cardiovascular events, including 874 atrial fibrillation, 156 myocardial infarction, 111 heart failure and 92 stroke events.

Those adults who met the 150 minute a week guideline on exercise experienced a modest 8-9% reduction in cardiovascular risk, the study found. This was consistent across all levels of fitness.

In order to achieve substantial protection, classed as a greater than 30% risk reduction, between 560 and 610 minutes of moderate to vigorous exercise a week was needed. However, this level of exercise was only achieved by 12% of people in the study.

The analysis found that those individuals with the lowest fitness needed approximately 30-50 additional minutes per week compared with those with high fitness to achieve equivalent benefits.

For example, to achieve a 20% reduction in the risk of cardiovascular events, 370 minutes of moderate to vigorous exercise was needed for those at the lowest fitness compared to 340 minutes for those at the highest fitness levels.

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

This is an observational study and as such no firm conclusions can be drawn about cause and effect. The researchers acknowledge that the study group could have been healthier and fitter than the general population. Another limitation was that cardiorespiratory fitness was estimated and sedentary time or less vigorous exercise was not measured.

The researchers say their findings confirm that current guidelines provide a robust universal minimum for cardiovascular protection. But they add that there should be stratified advice to help guide motivated patients to do more to protect their heart health.

“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.