Study urges 10 hours weekly—experts urge caution

A new analysis in the British Journal of Sports Medicine estimates that people may need roughly nine to 10 hours of moderate-to-vigorous exercise a week to cut the risk of stroke or heart attack by 30 percent. But cardiovascular and fitness specialists say the

On a day when exercise advice already feels like it changes every season, a new study has landed with the force of a stopwatch: aim for around nine to 10 hours of exercise a week.

The recommendation is tied to a specific goal—“a substantial reduction” in the risk of stroke or heart attack—and it goes well beyond the World Health Organization’s 150 minutes a week. The study. published this week in the British Journal of Sports Medicine. drew from accelerometer readings over a single week from 17. 000 individuals in the U.K. Biobank, a long-term health study. It found that. on average. people would need about 560 to 610 minutes of moderate to vigorous physical activity each week to experience a 30 percent reduction in risk.

Even then, the study suggests the numbers may rise for those who are less fit. To see the same benefits, the analysis indicates they may need as much as 50 additional minutes of exercise compared with people who are more fit.

The problem, several exercise and cardiovascular experts say, is not that people shouldn’t be active—it’s that the study’s design and its framing can make the message harder to interpret than it needs to be.

Sean Heffron. an assistant professor of medicine and a cardiologist specializing in exercise science at New York University. called the study’s pitch too restrained in the opposite direction: “playing down the benefit of physical activity.” He points out that the World Health Organization’s guidance of 150 minutes of moderate exercise a week is associated with an 8 to 9 percent reduction in risk. “That’s not nothing,” Heffron said. He added, “If we came up with a new medicine that improved risk that much, we’d be thrilled.”.

For Heffron, the new results don’t make the older public-health advice wrong. He says the findings do not indicate that the WHO’s guidance on exercise is incorrect. He also notes that the study doesn’t negate the idea that short. high-intensity bursts—such as high-intensity interval training—are tied to large reductions in cardiovascular disease risk.

Ulrik Wisløff. a professor at the Norwegian University of Science and Technology who heads the university’s Cardiac Exercise Research Group. agrees with that larger point while sharpening the critique of how the new number is presented. “The 150-minute recommendation was never intended to represent an ‘optimal’ target,” Wisløff said. “Rather it was designed as a realistic, achievable public health threshold associated with meaningful health benefits in the population.”.

Wisløff also argues the study’s approach can blur the meaning of intensity across individuals. The same physical task may feel completely different depending on age and fitness. “The study’s design also risks obscuring the relative intensity of physical activity for different individuals,” Wisløff said. He gave an example: an older person might view a walk around the block as vigorous exercise. while a younger and fitter person might not see that as exercise at all.

Heffron sees a second issue on the individual side. Many people may underestimate how much exercise they are already getting. He pointed out that moderate walking. tennis playing. gardening. or anything that makes you break a sweat “counts as vigorous activity.” “The gym does not hold a monopoly on exercise. ” he said.

Both experts emphasize intensity as the dividing line for health effects, not the wall clock. Wisløff highlighted previous studies suggesting that even five minutes a day of moderate to vigorous physical activity can reduce mortality risk by around 30 percent in people who otherwise didn’t exercise. “Small amounts of relatively intense activity appear extraordinarily powerful,” he said.

What the new study can’t capture, Heffron says, is that genetics also shapes fitness. He adds that the analysis uses only a week of data—so it’s possible participants exercised more than usual during that particular week, which could complicate what the findings mean over the long term.

Then there’s the part that most directly affects anyone who hears the headline and thinks. “This won’t work for me.” The study’s finding that less fit people may need up to 50 minutes more than their fitter counterparts to see the same benefits is one Heffron says clinicians shouldn’t treat as a personal verdict. “as a clinician, I would ignore that wholly,” he said.

Heffron stressed that exercise shouldn’t be framed as a contest with someone else’s baseline. “Your individual health and longevity is not a competition,” he said. “We’re confident that exercising is beneficial for multiple reasons, and we can’t determine who is going to benefit most from exercise.”

What is clear to him, he said, is that staying inactive carries real danger. “It’s clear that no activity puts you at markedly increased risk [of conditions such as diabetes and hypertension]. ” he said. And for people starting from zero, the first step matters. “Going from zero to anything on an individual basis can be helpful.”.

The sequence of claims in the new paper is straightforward—accelerometer data. a time target tied to a 30 percent reduction. and an explanation that those who are less fit may need more. But the experts’ reactions land on the gaps that matter to everyday readers: whether the intensity is truly comparable across bodies and ages. whether people already do more than they assume. and whether a week of measurement can safely stand in for a lifetime of movement.

exercise stroke risk heart attack risk British Journal of Sports Medicine U.K. Biobank accelerometer World Health Organization physical activity guidelines high-intensity interval training cardiovascular fitness