On last week’s running-related research post, I discussed whether or not the heel-to-toe drop of a running shoe influences injury rates.
This week, I’ll be discussing whether hip abductor, knee extensor, and knee flexor strength is associated with knee injuries in cross country runners. This study was published in The International Journal of Sports Physical Therapy in 2015. You can read the abstract below. This article is also open-access and the full-text can be viewed here.
Type of Study
Prospective cohort study. Similar to the type of study utilized in the research I covered in this post, a prospective cohort study is a study that follows similar individuals (or cohorts) over a period of time to determine how certain factors affect certain outcomes.
68 high school cross country runners.
What did they look at?
Isometric muscle strength was measured for three different movements using a device called a handheld dynamometer. Each one is pictured below.
Each runner reported whether a knee or shin injury occurred over the course of the cross country season. A typical cross country season generally starts in August and ends in November.
Of the 68 XC runners who participated in this study, 3 sustained a knee injury (4.4%) and 13 sustained a shin injury (19.1%).
Runners were placed within groups (which the researchers called tertiles) as either having the highest, middle, or lowest strength among the different movements tested.
Runners with the lowest hip abductor, knee extensor, and knee flexor strength had a significantly higher incidence of knee injury compared to those in the highest strength group.
Overall, decreased strength of these three muscle groups was not associated with shin injury. However, when analyzing girls individually, decreased knee extensor weakness was found to be associated with shin injury.
I really liked reading this study because it dealt with runners who were more competitive and who ran more frequently. I will often read studies where the participants are considered recreational runners but when you look at their average mileage, over the study duration, it is often very low with a very high standard deviation. This means that some runners in the study will often run 2 miles a week and others will be closer to 40.
I thought it was odd that so few runners sustained knee-related injuries.
I think most injuries are related more to inconsistency and not allowing the body enough time to adapt to the stresses placed upon it. I think this study highlights that idea well for shin injury especially since, for the most part, muscle strength was not associated with shin injury.
Questions for Readers
Have you had success implementing hip/knee strengthening while training for a particular race?