Not All Forefoot Striking Is Equal

Abstract

Rearfoot strike (RFS) runners typically exhibit an impact peak in their vertical ground reaction force caused by heel impact. This impact is associated with high load rates that have been linked to running injuries. The vast majority of forefoot strike (FFS) runners do not exhibit this impact peak and have significantly lower load rates compared with RFS runners. However, some FFS runners do exhibit an impact peak and load rates similar to RFS. The heel descent after initial contact in FFS could help further explain this phenomenon. PURPOSE: To investigate the relationship between heel kinematics and vertical average loading rate (VALR) in FFS runners. METHODS: 30 habitual FFS runners from an ongoing study were included (5F, 25M; age: 35.6±9.3). Ground reaction forces and heel kinematics were collected on an instrumented treadmill at 2.6±0.4m/s. Pearson correlations between VALR and heel height at initial contact (HIC), time to heel contact (THC), heel descent acceleration (HDA) and heel descent excursion (HDE) were extracted. These variables were also compared between runners who exhibit an impact peak (n=9) and those that did not (n=21). RESULTS: VALR was significantly (all p<0.01) correlated with HIC (r=-0.514), THC (r=-0.783) and HDA (r=0.612). A trend was found for the correlation with HDE (r=-0.33, p=0.08). FFS runners with an impact peak exhibited significantly lower HIC, a shorter THC and higher HDA (Table 1). A trend for lower HDE was noted in this group as well. CONCLUSIONS: Lower heel at initial contact, decreased time to heel contact, and higher heel descent acceleration were significantly correlated with greater VALR and were observed by FFS with vertical impact peaks. This suggests that FFS runners with these impacts should be trained to land with more plantarflexion and greater eccentric control of their heel descent to reduce their landing impacts.Supported by FAPESP (2017/26844-1).