Rearfoot, mid/forefoot, and barefoot running: biomechanical differences related to injury
Running is an accessible, inexpensive form of exercise. However, running injuries are common and burdensome. Many runners are curious about switching to barefoot (BF) running or minimalist shoes to avoid injuries, which is commonly associated with rearfoot strikers (runners who land on the posterior third of their foot) landing on the middle or front third (mid- or forefoot strike; FFS). My purposes were to determine if undocumented aspects of FFS and BF running are beneficial or harmful compared to rearfoot striking (RFS), and if any potential benefits of FFS or BF running can be achieved by shortening one’s stride length (SL) when using a RFS. I addressed this by conducting four studies. For all studies, habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF) ran with a RFS, FFS, and BF, and with a shorter SL. I looked at several ground reaction force (GRF) variables, kinematics, joint kinetics, tibial accelerations, stride time variability, and tibial bone stresses.
Impact peaks were present in the vertical GRF for RFS and in the posterior and medial directions with a FFS. Loading rates were generally higher in those same respective directions for the two foot strike styles. hRF decreased their vertical GRF variables by using a FFS.
Joint moments and contact forces were generally larger at the ankle for FFS while they were similar or larger at the hip for RFS. Some knee moments and contact forces were larger for RFS while others were larger for FFS. Patellofemoral loads were similar for foot strike styles. Nearly all moments and contact forces decreased with a shorter SL.
Free moment was distinctly different between foot strikes. Additionally, step width was narrower for FFS, but ITB strain and strain rate were similar, while RFS demonstrated greater pelvic drop. Shortening one’s SL had many minor beneficial effects, including a wider SW, and decreased free moment, pelvic drop, hip adduction, ankle eversion, ITB strain and strain rate.
Stride interval long range correlations became more patterned for the novel conditions, suggesting runners were not operating in their optimal state of adaptability, possibly making them susceptible to injury.
Finally, FFS resulted in higher compressive, tensile, and shear stresses in the distal tibia compared to RFS and BF. An 8% shorter SL only significantly decreased shear stresses.
In conclusion, not all lower extremity loading variables are lower with a FFS or when running BF; in fact, several variables were elevated compared to RFS. Therefore, switching to a FFS (whether shod or BF), may not alleviate certain pain or help runners avoid injury. A more viable option may be to shorten one’s SL 10%.