Differences in 10-20 Hz 'shock' attenuation emerge between injured and uninjured runners across a 30-minute run

Running is associated with high rates of injury. One mechanism that has been proposed to contribute to running injury is greater exposure to 10-20 Hz frequencies. Typically, these frequencies are attenuated (decreased in power) as they travel up the body, however, attenuation may be compromised as runners become fatigued. Here, we report the first ever comparison of 10-20 Hz frequency attenuation in injured and uninjured runners across a fatiguing run. Thirty-one runners (16 uninjured; 15 previously injured; 14 female; 17 male; age 31.6 ± 12.6 years) ran overground for 30-minutes while accelerations were measured at the tibia, gastrocnemius, sacrum, and head using tri-axial inertial measurement units. Power spectral density was calculated at each location and transfer functions between locations were used to quantify attenuation. Across the 30-minute run, fatigue was recorded using Borg's rating of perceived exertion and percent maximum heart rate. Between-group differences in attenuation were analyzed using statistical parametric mapping and ANOVA. Injured and uninjured runners showed similar patterns of attenuation from the tibia to head but differed in how they achieved this attenuation: When compared to uninjured runners, injured runners had significantly greater 10-20 Hz attenuation with the lower body (between tibia and sacrum) and significantly less 10-20 Hz attenuation with the upper body (between the sacrum and head). Further, the magnitude of these differences increased across the duration of the run. These findings demonstrate that previously injured runners attenuate 10-20 Hz frequencies differently than uninjured participants, suggesting an altered neuromechanical control strategy.