- Increasing your mileage too quickly can up your risk of injury, according to a new study published in the British Journal of Sports Medicine.
- While training for a marathon, focus on consistency and slowly increasing your long runs to safely rack up miles and remain injury-free.
Before you start training for your first or next marathon, here’s yet another reason for you to be meticulous about how you approach training: New research published in the British Journal of Sports Medicine found an association between rapid increases in mileage and injuries in marathon runners after analyzing nearly 50,000 runs using Strava data.
Sixteen weeks before the New York City Marathon, researchers began to track the runs of 735 participants, ages 18 and older, to analyze changes in their training volume and injury status. During the study, runners tracked their mileage through Strava and completed a survey every four weeks to report any illnesses or injuries that interrupted their training or resulted in them not competing.
“There’s a lot of different ways that you can look at training in terms of mileage, pace, frequency, and heart rate. What we wanted to do is start with something that is relatable to runners because runners often discuss their training in the form of mileage,” lead researcher, Brett Toresdahl, M.D., attending physician at the Hospital of Special Surgery (HSS) and research director for the HSS Primary Sports Medicine Service tells Runner’s World.
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For the purpose of this study, training volume was analyzed using two common methods: The 10-percent rule and acute to chronic workload ratio (ACWR). The 10-percent rule recommends runners consistently increase their training volume by no more than 10 percent each week. A more conservative approach, Toresdahl says this isn’t always an ideal way to increase mileage while training for a marathon. The ACWR method, on the other hand, is used to compare weekly training volume to monthly training volume. For example, Toresdahl explains, if you ran 20 miles in the past week but only averaged 10 miles in the past month, your ACWR would be 2:1 or 2.
In the end, researchers found a link between runners who had an ACWR of 1.5 or more and injury, while there was no association between injury and exceeding the 10-percent rule. Runners who initially reported injury during the first month had more days when their ACWR rapidly increased than those who ran injury-free that month.
“If your training volume in the past week was 50 percent higher than the average of your training volume over the past four weeks, that would be a risk factor for injury,” says Toresdahl. (That means if you run a weekly total of 25 miles this week, your previous four-week average should be somewhere above about 17 miles.)
That doesn’t mean everyone who exceeds that amount will experience an injury, but rather the more times you exceed that amount over the course of training, the more likely you are to become injured, Toresdahl says.
Overall, 40 percent of runners experienced an injury while training, and 4 percent of participants experienced a major injury that resulted in them not participating in the marathon.
How to Safely Progress Your Training Volume Leading Up to a Marathon
To sidestep injury, focus on consistency first, Toresdahl says, then focus on increasing the long run and not necessarily increasing those midweek, shorter runs. “Just looking at the training patterns of the runners who remained uninjured, we saw that their long run distance was increasing, but their total distance per week wasn’t increasing that much, meaning that they were maintaining a pretty consistent midweek or shorter run cumulative mileage,” he says.
Dealing with changes in mileage is only part of the overall stress a runner will endure while preparing for a marathon. Likewise, the ACWR is only one way to monitor your training volume, says Toresdahl. Meaning, there are plenty of ways to approach safely increasing your mileage to remain injury-free as you train for a marathon—the key is listening to your body and not doing too much too soon.
Also, instead of following a generic training plan or virtual trainer, consider teaming up with a run coach to help you through your training. They can also help you adjust your training plan to your schedule and needs.
Most importantly, Toresdahl says, “listen to your body—don’t feel compelled to just put in more mileage. More miles don’t always equal a better result.”
Monique LeBrun joined the editorial staff in October 2021 as the associate health and fitness editor. She has a master’s degree in journalism and has previously worked for ABC news and Scholastic. She is an avid runner who loves spending time outside.