When Running Up Mileage, 10 Percent Isnít the Cap
My friend Martin Strauss of Ann Arbor, Mich., was running 60 miles a week when he suffered a stress fracture that put him on crutches for three months. Now that heís better, he wants to play it safe to avoid another injury. But whatís the best way to do that? How quickly can he ramp up the miles?
Martin decided to follow the 10 percent rule, one of the most widely known in running. It does not specify a starting distance but says you should increase your mileage no more than 10 percent a week. The idea is that this is a safe way to increase your distance without risking injury.
(Within limits, of course; if you started at 30 minutes a day and kept increasing 10 percent a week, after 41 weeks youíd be running 24 hours a day.)
Martinís first run was on March 15. He ran half a mile, on a treadmill. Over the next five weeks, he increased his distance to ten miles a week, then began using the ten percent rule. Last week he ran 22 miles, including a long run of 10 miles. He calculates that it will take him a total of 18 weeks from when he started his program to get back to running 60 miles a week.
I, like most runners, have heard of the rule and, like most, tried it once. But, like many, I did not stay with it. Another friend, Rafael Escandon of Philadelphia, tried it years ago when he was training for his first marathon. It was the slowest marathon he ever ran, slower even than one when he tore his calf muscle at mile 17 and somehow forced himself to finish the race, limping for the last 9 miles. Cliff Rosen, a distance runner in Maine, said he tried it once but "it didnít seem to work."
That made me wonder, Where did this rule come from?
Carl Foster, director of the Human Performance Laboratory at the University of Wisconsin in La Crosse, said its origin "is lost in history," and added, "Whether it is right is undocumented."
It might be more correct to say "almost undocumented." There is at least one large and rigorous study of the 10 percent rule, the sort of study that is a rarity in exercise science. Conducted by Dr. Ida Buist, Dr. Steef W. Bredeweg, Dr. Ron L. Diercks and their colleagues at the University of Groningen in the Netherlands, itís one of a continuing series of studies on how to prevent running injuries.
The injury problem is huge, said Dr. Diercks, head of the sports medicine program at the university ó as many as 40 percent of runners are injured, usually to their feet, ankles, knees or legs. At his universityís running clinics, 30 to 40 percent of beginning runners gave up because of injuries.
Although there are many training programs for beginning runners, none are based on good scientific evidence, Dr. Diercks said. He and his colleagues decided to conduct such a study.
They investigated the 10 percent rule because it is so popular and seemed to make sense with its gradual increase in effort. The study involved 532 novice runners whose average age was 40 and who wanted to train for a four-mile race held every year in the small town of Groningen.
Half the participants were assigned to a training program that increased their running time by 10 percent a week over 11 weeks, ending at 90 minutes a week. The others had an eight-week program that ended at 95 minutes a week. Everyone warmed up before each run by walking for five minutes. And everyone ran just three days a week.
And the results? The two groups had the same injury rate ó about 1 in 5 runners.
Maybe, the investigators thought, they might prevent injuries with a conditioning program before the training started. So they did another clinical trial, randomly assigning one group of novice runners to a four-week program of walking, hopping and jumping rope before starting the running program. The others started right in with running.
The conditioning program had no effect. Once again, about 1 in 5 runners in both groups wound up with injuries.
The researchers are at a loss. Most people who take up running, Dr. Diercks says, think it will be easy ó all they need is a pair of shoes. But in fact, running is a difficult sport, and most people quit before it becomes fun, often because they are injured. Experienced runners know how to adjust and return to the sport. Novices usually do not, he says.
Now the Groningen group wants to do a large and rigorous study of barefoot running, comparing it to running with shoes ó another study that has never been done.
For now, though, the lesson is that running lore often is just that. And the 10 percent rule is a case in point.
"Nobody found out if it works or what is the basis of it," Dr. Diercks said.
And that is the way it often goes in exercise science. People "hear something, they read something," he said, "and then itís like a religion."
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