It has often been suggested that the 10% rule was the best amount to increase running distance. But this has been more based on clinical experience then research.
A recent research paper published in the October edition of Journal of Orthopaedic and Sport Physical Therapy attempted to shed light on this topic. They completed a one-year study into 874 novice runners and looked at what was the safe amount of running distance increase without sustaining an injury. At the completion of the study they determined that if you increase running distance weekly by more than 30% over a 1-week period you were more likely to sustain a distance related injury then those who increased less than 10%.
(Distance related injuries are injuries like patellofemoral pain (knee cap pain), iliotibial band syndrome, patellar tendinopathy, gluteus medius injury, greater trochanter bursitis, and tensor fascia lata injuries).
The lowest amount of distance related running injuries came from the group who increased their weekly distance by less than 10%. Caution should be taken not to increase just under 30% for more than a 1-week period (for example, 25% for 4 weeks) as there is a potential to again increase the chance of injury.
So what is your magic number? Unfortunately that may be depended on a number of factors such as age, weight, previous injuries and types of injuries. So if you have any questions about determining the safest way to increase running distance speak to one of your physios at Sydney Stadium Sports Physiotherapy.
References:
Nielsen, Parner, Nohr, Sorensen, Lind, & Rasmussen. (2014). Excessive progression in weekly running distance and risk of running-related injuries: an association which varies according to type of injury. Journal of Orthopaedic and Sports Physiotherapy. 44 (10), 739-748.