June 2011

Impact frequency data suggest unique risks for forefoot strikers

In the moment: Footwear

The frequency content of vertical ground reaction forces generated during running differ among forefoot strikers and rearfoot strikers, and this may have implications for injury risk, according to findings from the University of Massachusetts presented in June at the ACSM meeting.

Researchers assessed frequency amplitude and power in 10 natural rearfoot strikers and 10 natural forefoot strikers as they ran across a force platform.

At frequencies above 9 Hz, rearfoot strikers’ amplitude exceeded that of forefoot strikers. Similarly, above 22 Hz, power was significantly greater in rearfoot strikers. This is consistent with previous reports that only rearfoot strikers have an impact peak, which occurs between 10 Hz and 20 Hz.

But between 4 Hz and 7 Hz, amplitudes were higher in forefoot strikers. And for frequencies less than 6 Hz and between 9 Hz and 11 Hz, power was greater in forefoot strikers.

Because the body attenuates shock differently at different frequencies, the findings could suggest that even forefoot strikers (including most barefoot runners) may be at risk for certain injuries despite lacking an impact peak.

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