Ground Reaction Force Variables as Predictors of Lower Extremity Shock in Forefoot and Rearfoot Strike Patterns

Ground reaction force (GRF) parameters have been used to predict tibial shock in rearfoot strike patterns (Hennig & Lafortune, 1991). However, forefoot strike (FFS) runners have significantly different GRF parameters when compared to rearfoot strike (RFS) runners (Williams, D.S., et al., in press). A typical FFS running pattern results in significantly lower vertical GRF loading rates (ZLR) and greater peak vertical GRFs (PZ) when compared to a RFS pattern. Force plate data is used as a way to indirectly measure both the magnitude and the rate of external loading on the lower extremity during running, while tibial acceleration attempts to measure the resulting shock to the lower leg which is directly influenced by GRFs. Predicting shock from GRF parameters would potentially eliminate the need for measuring tibial accelerations.