Implications of Impact Force

What is the link between impact force and injury rates? Past studies have demonstrated a link between running injury and heel-strike impact. However, none of these studies have been prospective. Irene Davis, PT, PhD, a professor at Harvard Medical School and director of the Spaulding National Running Center in Boston researched the affect impact forces have on injury rates. The study was published in the British Journal of Sports Medicine in December of 2015. Included were 249 female runners with at least 6 months of injury free running. After two years, 58% experienced an injury. This is consistent with other research demonstrating approximately 50% of runners are injured every year. Dr. Davis is quoted as saying, “When you look at the people who have never been injured, they land significantly more softly than those who have injuries or an injury history.” Several impact variables were evaluated. “We suspect that it may not be the magnitude of the force that contributes to injury, but rather the rate of force development that is more important,” Dr. Davis commented. In layman’s terms, this means the harder you land the greater chance a runner can experience an injury. To date, there are no studies, including the present study, that demonstrate higher peak vertical forces are the primary cause of injury. Rather, impact forces are likely a small piece to the larger puzzle of running injuries. Higher rates of injury in this study included: bony stress injury, muscle strain, plantar fasciitis, Achilles tendinopathy, and anterior compartment syndrome. Dr. Davis concluded, “Now that we have this study suggesting more strongly that impact is related to injuries, we need to see the effect of training people to run more softly.”

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