There was, however, a statistical difference in mileage between women's performance levels, likely due to their greater range in performance. The elite women (sub 2:40) averaged 84 miles per week with a peak mileage of 112, while their national-class counterparts (2:40-2:48) averaged 69 miles per week with a peak mileage of 91. While the faster female marathoners ran more, only a quarter of the difference in marathon performance between women could be explained by the amount of mileage they ran. Mileage accounted for even less of the difference among the men.
So running more doesn't necessarily make you faster. Regardless of how much you run, genetics plays a large role in your performance. A person with a lot of talent will almost always outperform a person with little talent and a lot of training.
"If you look at the training data of elite athletes, you find that the optimum training volume for the world's best athletes lies somewhere between 75 and 110 miles per week," says Timothy Noakes, M.D., Discovery Health Professor of Exercise and Sports Science at the University of Cape Town in South Africa, and author of Lore of Running. "However, the time spent running may be more important than the mileage since a fast runner will run that distance much quicker than a slow runner. Humans may have a maximum training volume they can undertake, and I think it's close to 75 to 100 miles per week. Your body simply can't absorb any more training volume without breaking down."
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Beyond VO2 Max and Metabolism
If there is little or no improvement in VO2 max and the metabolic profile of muscles as one runs more than 70 miles per week, is there any benefit at all to running more? Maybe. Research has shown that runners who run high mileage tend to be more economical, which has led to the suggestion among scientists that running more than 70 miles per week improves running economy (the amount of oxygen used to maintain a given pace).
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It is possible that, just as repetition of the walking movement decreases the "jerkiness" of a toddler's walk to the point that it becomes smooth, repetition of the running movement has an under-recognized neural component. With countless repetitions, muscle fiber recruitment patterns and possibly even the relationship between breathing and stride rhythms are optimized to minimize the oxygen cost. In other words, practice makes perfect.
Additionally, high mileage reduces body weight, which further reduces the oxygen cost. Because it is hard to prove cause and effect, it is not clear whether high-mileage runners become more economical by running more miles, or are innately more economical and can therefore handle higher mileage without getting injured.
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Beyond the physiological adaptations to running lots of miles and their contribution to performance, the amount of mileage you run may ultimately depend on your brain. "The more important explanation, in my view, is that the brain is critically important in this process and is under-recognized," says Dr. Noakes. "The brain may optimally adapt to a certain volume of training and a lot of our training focus and adaptation may actually be to teach us that we can run the distance. The mental preparation starts long before you go training."
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While most runners and coaches agree that training volume is important, training intensity is more important than volume for improving fitness and performance, especially in highly trained runners. Research has shown that a high training intensity is vital for maximizing cardiovascular improvement and that VO2 max and other physiological variables can continue to improve with the inclusion of high-intensity training. For example, interval training performed at 95 to 100 percent VO2 max is the most potent stimulus for its improvement, and is necessary for further improvement in highly trained runners. Given that training volume will impact training intensity, the better question may not be how much mileage is necessary or enough, but how much mileage is too much to sacrifice intensity.
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So, as you prepare for your next 5K or marathon, how much mileage should you run? If you've read this far, you know that the answer is not an easy one (for some guidance, see "Should You Run More Miles?"). The best way to determine how much to do is to increase your mileage slowly and systematically from month to month and year to year, taking care to note how you respond to the training stimulus. And remember that more is not always better.
More: Should You Run More Miles?
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