Is Cycling Bad For Your Health, pt 2

The Journal of the American College of Cardiology recently published an article Dose of Jogging and Long-Term Mortality. You can read the abstract here.

The author's conclusions: The findings suggest a U-shaped association between all-cause mortality and dose of jogging as calibrated by pace, quantity, and frequency of jogging. Light and moderate joggers have lower mortality than sedentary nonjoggers, whereas strenuous joggers have a mortality rate not statistically different from that of the sedentary group.

I don't have a subscription to the journal so I haven't gone through the article in depth and can't comment on the strengths and weaknesses of the study (and there are always many). This was part of The Copenhagen City Heart Study. One of the difficulties in applying conclusions from a European study looking at diet or activity to North Americans is the difference in diet and lifestyle. I lived parts of 3 summers in Copenhagen. It is shockingly expensive to own a car there. Danes ride bikes as transportation far more than North Americans. Things are a lot closer and so they walk more than we do. Their baseline physical activity level may be higher and the jogging is added on top of it. The Danish diet is also much different. Pork is the national dish (with loads of fat in the gravy and flaeskesvaer - pork crackling or fried pork rinds/fat). Tempering that, they are practically surrounded by water and eat more seafood than we do. Perhaps most importantly, although the last 15-20 years have seen an influx of Italian and Turkish immigrants, Danes have a much less varied genetic make-up than we do.

This paper raises yet more questions about possible deleterious health effects from repeated strenuous physical activity. It is very important for us to keep that in mind. On the other hand it is early days in our understanding and the findings shouldn't just be applied blindly to North Americans.