A recent article published in the Journal of the American College of Cardiology, which analyzed data from the Copenhagen City Heart Study, found that compared to frequent running sessions that are long and intense (or what some are describing as “too much running”), occasional bouts of light jogging may be better for overall health and longevity.
The key word here is “may.”
If you do a Google news search for the words “jogging” or “running” today, within the top results you’ll find a few accusatory headlines like, “Too much jogging ‘as bad as no exercise at all’”, “Cool News: Jogging Too Much Is Bad for You”, and “Fast running is as deadly as sitting on couch, scientists say.”
However, as many other reporters have recently pointed out, these headlines really missed the mark, because the statistical evidence from this analysis isn’t significant enough to form a solid conclusion about whether or not “too much running” is actually “bad” or “as deadly as sitting on the couch.”
Where are these crazy claims coming from, then?
Well, the study tracked and compared 1,098 healthy joggers and 413 non-joggers that were otherwise considered healthy over the course of 12 years. To summarize the results simply, the researchers found that during that time period, the subjects who jogged “strenuously” were as likely to die as the subjects who did not jog at all, while the “light joggers had the lowest rates of death.”
However, this oversimplified summary leaves out so many important details and completely ignores the larger significance of the study.
Forbes reporter Larry Husten makes note of the study’s weaknesses, which were highlighted by the its own authors.
“First there is the general issue that this is just an observational study. There are a multitude of differences between the different groups in the study, and it is impossible to know with any certainty whether the jogging dose had any important causal relationship with the deaths that occurred in the study. Of course the researchers attempted to correct for many of the known differences but this is a highly imperfect science at best. And this was not a best case scenario. The mean age of the non-joggers in the study was 61.3 years while the mean age of all the joggers in the study ranged from the late 30s to the mid 40s. So this isn’t just comparing apples and oranges, it’s comparing a young juicy apple with a shriveled old lemon.”
Basically, the data just does not support any definitive proof that “too much jogging” is as a “deadly” as being sedentary.
In his analysis of the study, science journalist Alex Hutchinson included a simple breakdown of the raw data to further emphasize the lack of any statistical significance.
“You can search through those numbers looking for patterns. Does your risk really go up if you run more than 2.5 hours, but then go down again if you run more than four hours? Of course not,” he wrote. “These are not real patterns, because we're talking about one, two, three, or at most five or six deaths. No matter how interesting or important the question is, you can't torture these numbers enough to force them to reveal the answers. They're simply not there.”
Additionally, Dr. Valentin Fuster, Director of Mount Sinai Heart at The Mount Sinai Hospital and editor-in-chief for the Journal of the American College of Cardiology, provided audio commentary about the study, which included quotes from some of the study’s authors.
The key points mentioned included:
- “The good news is that the mortality benefits of light jogging will encourage more people to jog for health benefits as a practical, achievable, and sustainable goal.”
- “The study entailed about 1,000 healthy joggers, but excluded about 3,500 active non-joggers who are active in other types of exercise. I think this is critically important. So we talk about exercise as an equivalent to jogging not other types of exercise.”
- The sample size was small, “and therefore the statistical power is somewhat challenging.”
- “The general consensus of the data certainly suggests that more is not better regarding running and mortality, however, we still need more data to truly determine, ‘is more actually worse?’”
Is more actually worse?
The bottom line: we don’t have enough evidence to answer that question yet. This also means that we have no way to quantify what “too much running” is.
As Duck-chul Lee, Carl J. Lavie, and Rajesh Vedanthan explain in an accompanying review of the study, “The dose-response relationship between running and mortality is still subject to debate and controversy.”