Effects of Foot-Strike Patterns During Running on Cumulative Load of Achilles Tendon Force, Plantar Fascia Force, and Patellofemoral Joint Stress.

Foot-strike patterns, including rearfoot strike (RFS), midfoot strike (MFS), and forefoot strike (FFS), are related to running injuries. Additionally, cumulative load is an important parameter when considering running injuries, but the cumulative loads of Achilles tendon force (ATF), plantar fascia force (PFF), and patellofemoral joint stress (PFJS) across all foot-strike patterns, including MFS, remain unknown. This study examined the effects of different foot-strike patterns during running, including MFS, on the peak values and cumulative load of ATF, PFF, and PFJS. Twenty healthy participants were enrolled in this study. The ATF, PFF, and PFJS during barefoot running with RFS, MFS, and FFS at 10 km/h were analyzed using a three-dimensional motion capture system and force plates. Their peak values and impulse per mile (an indicator of cumulative load) were calculated. These variables were statistically compared across foot strike patterns. The significance level was adjusted using the Bonferroni method for post-hoc tests (α = 0.016). Additionally, Cohen's d was used to calculate the effect size. The peak values and cumulative loads of the ATF and PFF were highest in FFS, followed by MFS and RFS. Conversely, the peak values and cumulative loads of the PFJS were higher in RFS and MFS than in FFS. Additionally, the effect size of impulse per mile was larger than that for peak values. The load is applied to different regions depending on the foot-strike pattern. ATF and PFF showed intermediate values at midfoot strike, MFS is suggesting that it may reduce the risk of developing or exacerbating Achilles tendinopathy and plantar fasciitis. Moreover, cumulative load may be a more meaningful parameter than peak values for estimating load during actual running.