A new study in by Dr Carl Lavie (Ochsner Health System, New Orleans, LA) showed that the mortality benefits of running are best accumulated in shorter distances, specifically at less than 20 miles per week. In fact, at longer distances, the researchers observed a U-shape relationship between mortality and running, with longer weekly distances trending back in the wrong direction, toward less mortality benefit.
Lavie stressed that the study is one of the largest to date, including data on more than 52 000 men and women participating in the Aerobics Center Longitudinal Study (ACLS), results will likely vary among individuals with differing athletic abilities or different ages. Running was associated with a 19% lower risk of all-cause mortality when compared with individuals who did not run. Individuals who ran six and seven miles per hour had a significant 21% and 27% lower risk of all-cause mortality, whereas those who ran eight or more miles per hour had a nonsignificant 7% lower risk of all-cause mortality. Running up to 20 miles per week was associated with a significantly reduced risk of death, with the largest benefit observed in those who ran between 10 to 15 miles weekly. For those who ran 20 to 25 miles and more than 25 miles per week, however, there was a nonsignificant 10% and 5% reduction in all-cause mortality.
Lavie noted that it is impossible to say definitively that more running is making the reduction in all-cause mortality go in the other direction, as it's possible that unmeasured variables might have influenced the results. It's possible that runners might not be taking care of themselves in other ways. Endurance exercise may also be associated with coronary artery calcification, diastolic dysfunction, or arterial stiffening. For a cardiovascular protection thirty to forty minutes of running is better that ninety minutes of running. This study is showing that more is not better when it comes to exercise.