Weekly running volume and risk of running-related injuries among marathon runners. International Journal of Sports Physical Therapy. (2013)

Abstract
PURPOSEBACKGROUND: The purpose of this study was to investigate if the risk of injury declines with increasing weekly running volume before a marathon race.
METHODS:
The study was a retrospective cohort study on marathon finishers. Following a marathon, participants completed a web-based questionnaire. The outcome of interest was a self-reported running-related injury. The injury had to be severe enough to cause a reduction in distance, speed, duration or frequency of running for at least 14 days. Primary exposure was self-reported average weekly volume of running before the marathon categorized into below 30 km/week, 30 to 60 km/week, and above 60 km/week.
RESULTS:
A total of 68 of the 662 respondents sustained an injury. When adjusting for previous injury and previous marathons, the relative risk (RR) of suffering an injury rose by 2.02 [95% CI: 1.26; 3.24], p < 0.01, among runners with an average weekly training volume below 30 km/week compared with runners with an average weekly training volume of 30-60 km/week. No significant differences were found between runners exceeding 60 km/week and runners running 30-60 km/week (RR=1.13 [0.5;2.8], p=0.80).
CONCLUSIONS:
Runners may be advised to run a minimum of 30 km/week before a marathon to reduce their risk of running-related injury.

My comments:

This was an interesting study with researchers finding elevated risk for injury if marathoners ran less than 30 km per week (18.6 miles) as they trained for their marathon. You hear a lot of talk of overuse injuries and these investigators found there was also risk of being underprepared for a race, and better yet they quantified how much was enough. People training less than 30 km per week being 134% more likely to be injured than marathoners who ran more. Those who ran more than 60 km (37.3 miles) had no additional risk reduction but were not of elevated risk.

Also noted in the study was that first time marathoners were at higher risk for injuries than those had run them before. Those with prior running injuries were more likely to get injured. Surprisingly younger runners (those under 35) were more likely to get injured than older ones. Most common injuries were of the knee, foot and ankle.