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Newsweek confuses association with causation in ‘weekend warrior’ exercise story


4 Star




Our Review Summary

This story highlights the findings of a large, longitudinal study conducted in England and Scotland. However, “large” doesn’t mean “conclusive,” which this story seems to indicate.

As we saw in our review of The Guardian’s take on the same study, the story confuses association with causation (see more in Why This Matters and Quantified Benefits, below) and didn’t adequately provide a sense of the size of the potential benefits.


Why This Matters

If getting a lot of activity is only plausible on the weekends, and research shows it’s useful at reducing early death risk, then that’s perhaps newsworthy. However, the findings should not be overstated as conclusive, which was done in this story. Researchers saw an association with physical activity and reduced risk of death when looking at data–they did not prove it’s a direct cause-and-effect relationship by assigning people to different types of exercise and then tracking what happens. This should have been made clearer.


Does the story adequately discuss the costs of the intervention?

Not Applicable

Given the nature of the study we don’t think that this issue is relevant.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The story used only relative risk numbers to quantify the benefit. This is inadequate, as we explain in Reporting the findings: Absolute vs relative risk.

Also, the story confused association with causation, i.e., “researchers in the U.K. found that weekend exercise appears to be just as effective at preventing heart disease and cancer as exercise done more frequently.”

The title of the paper suggests otherwise: “Association of Weekend Warrior and other Leisure Time Activity Patterns with Risk of All Cause Cardiovascular Disease and Cancer Mortality.” See more on the importance of not overstating observational findings.

Does the story adequately explain/quantify the harms of the intervention?


The story does a good job highlighting some of the potential harms associated with vigorous physical activity: “However, experts caution that it is possible to overdo it”  and “more exercise than two and a half hours a week can actually be unhelpful and even harmful.”

An expert in the field not associated with the study provides a bit of common sense to the discussion; “There are risks that come with a weekend warrior exercise schedule, especially for people who aren’t used to being active. “I would be more concerned about what’s happening at the point of exercise—not the long-term benefits,” says Dr. Howard Andrew Selinger, chair of family medicine at Quinnipiac University.

Does the story seem to grasp the quality of the evidence?


The story provides adequate information about the study design, the populations involved and some of the limitations of the study design.

However, it left out important limitation: The inactive population studied was 7 years older, had more current smokers, and suffered more from unspecified “long standing illness” than the participants who were active.

Does the story commit disease-mongering?


No evidence of disease mongering here.

Does the story use independent sources and identify conflicts of interest?


The story does provide some precautionary words from an independent expert in the field related to the risks associated with strenuous exercise. We would have liked to have seen an expert in the field provide comments on the study, the inherent limitations and on the conclusions drawn.

Does the story compare the new approach with existing alternatives?


Although the focus of the story was the “weekend warrior,” several comments were included suggesting alternative exercise strategies, including: “This could be something as simple as a brisk walk or other low-impact options for vigorous exercise about 20 minutes a day.  “In theory, someone who did one bout of 150 minutes of moderate exercise is a weekend warrior,” says O’Donovan. This study shows that it doesn’t matter how you decide to split up the recommended weekly amount of exercise. You just need to do it.”

Does the story establish the availability of the treatment/test/product/procedure?

Not Applicable

We think that the ability to exercise is generally available, so this is N/A.

Does the story establish the true novelty of the approach?

Not Satisfactory

The story did not establish what’s novel, unlike what we saw in our review of The Guardian’s story.

Does the story appear to rely solely or largely on a news release?


The story does not appear to rely on a news release.

Total Score: 6 of 8 Satisfactory


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