Midtarsal locking, the windlass mechanism, and running strike pattern: A kinematic and kinetic assessment

Abstract

Changes in running strike pattern affect ankle and knee mechanics, but little is known about the influence of strike pattern on the joints distal to the ankle. The purpose of this study was to explore the effects of forefoot strike (FFS) and rearfoot strike (RFS) running patterns on foot kinematics and kinetics, from the perspectives of the midtarsal locking theory and the windlass mechanism. Per the midtarsal locking theory, we hypothesized that the ankle would be more inverted in early stance when using a FFS, resulting in decreased midtarsal joint excursions and increased dynamic stiffness. Associated with a more engaged windlass mechanism, we hypothesized that a FFS would elicit increased metatarsophalangeal joint excursions and negative work in late stance. Eighteen healthy female runners ran overground with both FFS and RFS patterns. Instrumented motion capture and a validated multi-segment foot model were used to analyze midtarsal and metatarsophalangeal joint kinematics and kinetics. During early stance in FFS the ankle was more inverted, with concurrently decreased midtarsal eversion (p < 0.001) and abduction excursions (p = 0.003) but increased dorsiflexion excursion (p = 0.005). Dynamic midtarsal stiffness did not differ (p = 0.761). During late stance in FFS, metatarsophalangeal extension was increased (p = 0.009), with concurrently increased negative work (p < 0.001). In addition, there was simultaneously increased midtarsal positive work (p < 0.001), suggesting enhanced power transfer in FFS. Clear evidence for the presence of midtarsal locking was not observed in either strike pattern during running. However, the windlass mechanism appeared to be engaged to a greater extent during FFS.

Keywords: Forefoot strike; Metatarsophalangeal joint; Midfoot; Multi-segment foot; Rearfoot strike.

Figure 1

Ankle, midtarsal (MT), and metatarsophalangeal (MP) joint angles, time normalized across stance phase (0–100%) for rearfoot (RFS) and forefoot (FFS) strike patterns. Each curve contains the mean ± standard error bands (shaded regions). Below each angle plot is a between-condition difference plot (RFS - FFS), containing the mean ± 95% confidence interval bands. Regions where those bands separate from zero can be considered regions of statistical differences. (Legend: FFS, RFS)

Figure 2

Power profiles for the knee, ankle, midtarsal (MT), and metatarsophalangeal (MP) joints as well as for the structures distal to the rearfoot for rearfoot (RFS) and forefoot (FFS) strike patterns. Each curve contains the mean and ± standard error bands (shaded regions). Below each angle plot is a within-subject difference plot (RFS - FFS), containing the mean ± 95% confidence interval bands. Where those bands separate from zero can be roughly considered regions of statistical differences. (Legend: FFS, RFS)

Figure 3

Sagittal plane midtarsal (MT) moment and stiffness for rearfoot (RFS) and forefoot (FFS) strike patterns. A) Sagittal plane MT moment across stance phase (mean ± standard error bands as in Figure 1). B) Sagittal plane MT moment vs angle plot for a single representative subject. Stiffness was calculated as a linear best fit during early (moving upward and right in this subject) and late stance (moving downward and left). Note that the beginning of the RFS plot is horizontal until the CoP passes anterior to the MT joint; this portion was not included in the RFS stiffness. (Legend: FFS, RFS)