It has long been an article of faith among most runners and coaches that increasing your mileage by more than 10% from one week to another increases your risk of injury.
Perhaps not so much, according to a new Danish study published in the Journal of Orthopaedic & Sports Physical Therapy, which has devoted its October issue to running injuries.
Researchers led by Rasmus Østergaard Nielsen of Aarhus University divided nearly 900 novice runners each week for a year into three groups determined by how much they had increased their mileage from the previous week — those who kept it to less than 10%, those who raised it by 10-30%, and those who ran more than 30% farther than in the previous week.
More than a quarter of the runners suffered an injury serious enough to require a week off or at best no more than light training — but there was no statistically significant difference in the injury rate across the three groups.
If there was a difference it was in the mix of injuries. Those with the highest increases in mileage, not unsurprisingly, suffered more injuries of the kind usually associated with distance. Nielsen and his team defined these as patellofemoral pain (runner’s knee), iliotibial band syndrome, medial tibial stress syndrome (shin splints), gluteus medius injury, greater trochanteric bursitis, injury to the tensor fascia latae, and patellar tendinopathy (jumper’s knee).
Other common overuse running injuries, such as plantar fasciitis, Achilles tendinopathy, calf injuries, hamstring injuries, tibial stress fractures, and hip flexor strains, affected all runners regardless of how they mixed up how far they ran each week. Look elsewhere than sharp increases in weekly mileage for the causes of those.
The Danish researchers also found that runners who increased their mileage by more than 30% in successive weeks sustained more of the distance injuries than those who dialed back their increase in the second week.
Whether those findings apply to more experienced runners will take more research, but the conclusion for newcomers to running is that it is fine to up your mileage significantly once in a while. Just don’t make a habit of it if you want to stay injury free.