An important abstract presented at the 2012 annual meeting of the American College of Sports Medicine attracted a lot of attention because it added fuel to the “excessive endurance exercise” hypothesis that was gathering steam at that time. Now the paper has appeared in its full-text, peer-reviewed form in the Journal of the American College of Cardiology, and it’s, well, quite different.
The new paper is receiving wide coverage and being heralded as a landmark study on the benefits of running. It concludes: “Running, even 5-10 minutes a day, at slow speeds, even slower than 10 kilometres per hour [6:00 minute pace], is associated with markedly reduced risks of death from all causes and cardiovascular disease.”
In other words, it takes only about 6 to 8 kilometres a week of running at 6:50 to 7:30 minutes-per-kilometre pace to gain considerable benefit. The authors state: “This study may motivate healthy but sedentary individuals to begin and continue running.”
The paper places the reduced risks for runners at 30 per cent for all-cause mortality and 45 per cent for cardiovascular mortality. A sub-group of “persistent runners” who maintained their running programs for an average of 5.9 years enjoyed even greater reductions in mortality risks. As with similar reports, women appear to accrue substantially more benefit than men.
The analysis is based on more than 55,000 adults (average age: 44) who were enrolled in the Aerobics Centre Longitudinal Study. The mortality risks were calculated from an average 15 years of follow-up on the subjects. The key comparison was non-runners vs. runners of different speeds and weekly running mileage and frequencies.
When the same basic data was presented in abstract form two years ago, the authors concluded: “Running distances of .16 to 32 kilometres a week, speeds of 10 to 11 kilometres per hour, or frequencies of 2 to 5 days/week were associated with a lower risk of all-cause mortality, whereas higher mileage, faster paces, and more frequent running were not associated with better survival.” In other words, mortality rates increased if runners ran more than 32 kilometres a week, faster than 5:20 pace, or more than 5 days a week, the researchers claimed at the time.
The new paper makes only one mention of increased risks with more running. “However, mortality benefits were slightly less at the highest quintile of weekly running time, greater than 175 minutes a week.”
Lead author Duck-chul Lee, Ph.D., of Iowa State University, U.S., says that runners who run less than an hour per week gain the same mortality benefits as those who run more than three hours a week.
“Since time is one of the strongest barriers to participate in physical activity, the study may motivate more people to start running,” Lee said in a press release accompanying the research. “Running may be a better exercise option than more moderate intensity exercise since it produces similar, if not greater, mortality benefits in 5 to 10 minutes compared to 15 to 20 minutes of moderate intensity activity.”
Most of the subjects enrolled in the study were non-runners. A sub-analysis of 20,000+ subjects who received two medical evaluations revealed the following: 65 per cent were non-runners at the time of both exams, 14 per cent stopped running, 8 per cent started running, and 13 per cent were running at the time of both exams.
The 13 per cent were the ones who had the greatest reduction in mortality rates.
“The findings of this study have huge public health implications,” Michael Joyner, M.D., an endurance expert at the Mayo Clinic, told Runner’s World. “The too-much exercise story, if it even exists, is about rare events in a rare group of people, and is not important from a public-health perspective. The shift in the focus of this study has led to an important finding with big-time implications.”
