Runners’ Injury Risk Factors Might Surprise You

A new study sheds some light on the injury risk factors for recreational runners. One of the most surprising findings was that vertical impact peak, loading rate, and step rate were not risk factors at all.

In the study, “Spatiotemporal and Ground-Reaction-Force Characteristics as Risk Factors for Running-Related Injury: A Secondary Analysis of a Randomized Trial Including 800+ Recreational Runners,” published online on January 20, 2022 in The American Journal of Sports Medicine, the researchers sought to identify risk factors among spatiotemporal and ground-reaction force characteristics in recreational runner.

They also wanted to know if shoe cushioning changed the way running biomechanics impacted injury risk.

“Running biomechanics may play a role in running-related injury development, but to date, only a few modifiable factors have been prospectively associated with injury risk,” the researchers wrote.

For the study, they tested 848 recreational runners on an instrumented treadmill at their preferred running speed. They were all randomly assigned to wear either hard or soft cushioned shoes.

The researchers calculated typical kinetic and spatiotemporal metrics from ground-reaction force recordings. All the runners were then tracked for up to six months for running activity and injury risk.

They found that greater injury risk was associated with greater step length (sub hazard rate ratio [SHR], 1.01; 95% CI, 1.00-1.02; p = .038), longer flight time (SHR, 1.00; 95% CI, 1.00-1.01; p = .028), shorter contact time (SHR, 0.99; 95% CI, 0.99-1.00; p = .030), and lower duty factor (defined as the ratio between contact time and stride time; SHR, 0.95; 95% CI, 0.91-0.98; p = .005).

And when they stratified the analysis by shoe version and adjusted for previous injury and running speed, they determined that lower duty factor was associated with a greater injury risk for runners using soft shoes, but not for those wearing hard shoes.

“Lower duty factor is an injury risk factor, especially for softer shoe use. Contrary to widespread beliefs, vertical impact peak, loading rate, and step rate were not injury risk factors in recreational runners,” the researchers wrote.

The study authors included Laurent Malisoux and Paul Gette of Luxembourg Institute of Health in Grand-Duchy of Luxembourg, Nicolas Delattre of Villeneuve d’Ascq in France, Axel Urbausen, M.D., of Centre Hospitalier de Luxembourg in Grand-Duchy of Luxembourg, and Daniel Theisen of ALAN-Maladies Rares Luxembourg in the Grand-Duchy of Luxembourg.