Running Fast Isn’t Necessarily Linked to Stress Fractures
To avoid stress fractures, runners often guard against running too fast or too long or accelerating their training too quickly. But according to a new study from the University of Maryland School of Public Health, running fast doesn’t cause any more strain on a person’s shin bones than running at a slower pace does.
Assistant Professor Ross Miller and his research team, including doctoral students Jessica Hunter and Gina Garcia and Associate Professor Jae Kun Shim, all in the Department of Kinesiology, studied 43 recreational runners as they circled a 50-meter track, first at a self-chosen moderate speed, and again alternating between slow and fast speeds.
While the participants ran, the researchers measured three variables that affect the pressure running asserted on their tibias: how quickly they transfer their weight onto their leg when taking a step, the pattern of their foot’s movement on the ground and how much weight their legs ultimately bore.
The researchers found that fast running was no riskier than slow running. Both speeds contributed similarly to the first two variables, but slow running actually meant the participants’ tibias bore more cumulative weight — or cumulative tibial load — than they did while running fast. That’s because, when a runner’s pace slows, their stride shortens and their feet are in contact with the ground longer.
“Of the variables we tested, the difference in step length between the fast and slow speeds had the greatest effect on cumulative tibial load,” Hunter told Runner’s World in an interview about the research. “Since step lengths were shorter at slower speeds, subjects needed to take more steps while running slower.”
Because stress fractures are often attributed to running too fast or too intensely, interval training — alternating between fast and slow speeds — is thought to decrease risk of injury. Little is known though about how changing speeds affects the strain placed on a runner’s shins. This study clarifies the effect of interval training on stress fracture risk, suggesting that runners can add more fast running to their training programs without increasing their chance of injury.
The study also has implications for how runners calculate the intensity of their workouts. Runners often measure the strain placed on their body by tracking the total distance and average speed of their runs, but the study’s results show that additional variables like changes in speed should be tracked, too, to accurately characterize the intensity.
Exercise physiology, including how exercise interventions affect risks for injury and disease, is one of the major research areas among UMD kinesiology faculty. Miller's research centers on how the neural, muscular and skeletal systems interact to produce locomotion in health and pathology.
The study, ‘Fast Running Does Not Contribute More to Cumulative Load than Slow Running,’ was published in January in the American College of Sports Medicine’s journal Medicine & Science in Sports & Exercise.