Run For Your Life, But Not Too Far

Once again, we have a story of "the dose makes the poison." In the fitness world many believe that if running 5 miles is good for you, running 10 might double the benefit. Apparently not.

A recent study presented at the American College of Sports Medicine's annual meeting suggests that shorter distances (less than 20 miles per week) provide a greater mortality benefit. (1) While this is an unexpected finding, the more shocking news is that with increasing distance the reduction in mortality doesn't just level off but actually but reverses.

Dr. Duck-chul Lee led the research, a part of the Aerobics Center Longitudinal Study (ACLS) which includes 52,000 men and women in a retrospective analysis. Subjects entered the study free of cardiovascular disease, EKG abnormalities, diabetes and cancer. They were followed for 15 years.
Running was associated with a 19% lower risk of all-cause mortality compared with individuals who did not run.

Interestingly, how fast you run is important too. Subjects who ran 6 and 7 miles per hour had a significant (21% and 27%) lower risk of all-cause mortality. Those running faster (8 or more miles per hour) had a nonsignificant decrease in risk of all-cause mortality.

The most robust decrease in risk of death was seen in subjects who ran between 10 and 15 miles per week.

How often you run also makes a difference. The benefits of running were lost in those running more than 5 days per week.

While it is possible that some unmeasured variables might have contributed to these findings, the investigators corrected for other known factors such as age, gender, smoking status, blood pressure, and cholesterol levels.

The ACLS study coincides with the publication of a review paper in the Mayo Clinic Proceedings on the possible causes of heart damage seen in participants of long-distance endurance events (marathons, Ironman, long-distance cycling).(2) The review suggests that such activities may cause fibrosis of the heart muscle that can lead to arrhythmias and coronary artery calcification and hardening.

The bottom line is less is more. This data should not be a reason not to run. A regimen of up to 20 miles a week in 2 to 5 sessions at a pace below 8 miles per hour looks best.

So, run for your life, not too far, too fast, too often.  

References

1. Lee DC, Pate RR, Lavie CJ, et al. Running and all-cause mortality risk--is more better? American College of Sports Medicine 2012 Annual Meeting; June 2, 2012; San Francisco, CA. Presentation 3471.
2. O'Keefe JH, Patil HR, Lavie CJ, et al. Potential adverse cardiovascular effects from excessive endurance exercise. Mayo Clin Proc 2012; 87:587-595.