Primary mechanical factors contributing to foot eversion moment during the stance phase of running

Effect of individual ankle taping components on the restriction of ankle external inversion moment

The efficacy of individual taping components to restrain ankle inversion sprain has not been fully understood to date. We aimed to clarify specific taping components that can effectively restrain the amount of angular impulse due to external ankle inversion moments during dynamic ankle motion. Nine participants with chronic ankle instability performed a side-jump with five taping conditions: stirrup, figure eight, heel lock, basketweave, and without taping (control). During the initial landing phase, angular impulses, plantar inclination angle of the whole foot, and plantar flexion angle of the midfoot and hindfoot were compared among these conditions. The basketweave was the only taping condition succeeded in significantly reducing plantar inclination angle of the whole foot, thereby inducing significantly reduced angular impulse due to external ankle inversion moment compared with the control. Although the stirrup and figure eight were found to significantly restrict the plantar flexion angle of the hindfoot and the midfoot, respectively, neither of these components could alter the plantar inclination angle of the whole foot. It was suggested that all the taping components are necessary to reduce the external ankle inversion moments. Certain components should not be used individually to alter the plantar inclination angle of the whole foot.

Major factors influencing rearfoot external eversion moment during barefoot walking

BACKGROUND

Excessive rearfoot eversion motion during walking has been considered as a risk factor for lower limb chronic injuries. External moment due to ground reaction force (GRF) is the essential cause by which the rearfoot is passively everted during walking.

RESEARCH QUESTION

This study aims to identify the key factors influencing the rearfoot external eversion moments due to the GRF during walking.

METHODS

From 3-D foot coordinates and GRF data of 29 healthy participants during walking, the rearfoot external eversion moments due to the GRF and factors composing the moment (height of the ankle joint center, mediolateral GRF, mediolateral distance of the center of pressure relative to the ankle joint center in the transverse plane, vertical GRF) were computed.

RESULTS

The mediolateral GRF was a key factor influencing the magnitude of the rearfoot external eversion moment just after foot contact, with which pre-contact medial foot velocity was significantly correlated. During the subsequent support phase, the mediolateral distance of the center of pressure (the application point of the vertical GRF) relative to the ankle joint center was also found to be another determinant of the magnitude of the rearfoot external eversion moment.

SIGNIFICANCE

We succeeded in demonstrating the specific factors that most likely explain the magnitude of the rearfoot external eversion moment during initial contact and the subsequent support phase during walking. Based on the findings, specific measures to suppress the rearfoot external eversion moment could be proposed.

Mechanical factors affecting the foot eversion moment during the stance phase of running in non-rearfoot strikers

This study aimed to identify the primary factors that induce rearfoot external eversion moments due to ground reaction force (GRF) in non-rearfoot strikers. The data were compared with those of rearfoot strikers. Totally, 11 healthy males who were habitually non-rearfoot strikers ran barefoot. Rearfoot external eversion/inversion moments due to GRF (Mtot) were decomposed into two components based on mediolateral (Mxy) and vertical (Mz) GRFs. The height of the ankle joint centre and the mediolateral distance from the centre of pressure (COP) to the ankle joint centre (a_cop) were calculated as the lever arms to the Mxy and Mz components. Just after foot contact, non-rearfoot strikers demonstrated a significantly larger Mz, which was strongly dependent on a_cop and produced most of the Mtot, whereas Mxy dominated Mtot in rearfoot strikers. During the consecutive loading phase, non-rearfoot strikers demonstrated a significantly larger Mxy, which was strongly dependent on the mediolateral GRF and substantially contributed to Mtot, unlike the rearfoot strikers, whose Mtot was almost dominated by Mz during the loading phase. It was found that since the factor of generating the moment differs depending on the foot contact pattern, the strategies for suppressing the moment may be different for each foot contact pattern.

Ankle taping can reduce external ankle joint moments during drop landings on a tilted surface

Ankle taping is commonly used to prevent ankle sprains. However, kinematic assessments investigating the biomechanical effects of ankle taping have provided inconclusive results. This study aimed to determine the effect of ankle taping on the external ankle joint moments during a drop landing on a tilted surface at 25°. Twenty-five participants performed landings on a tilted force platform that caused ankle inversion with and without ankle taping. Landing kinematics were captured using a motion capture system. External ankle inversion moment, the angular impulse due to the medio-lateral and vertical components of ground reaction force (GRF) and their moment arm lengths about the ankle joint were analysed. The foot plantar inclination relative to the ground was assessed. In the taping condition, the foot plantar inclination and ankle inversion angular impulse were reduced significantly compared to that of the control. The only component of the external inversion moment to change significantly in the taped condition was a shortened medio-lateral GRF moment arm length. It can be assumed that the ankle taping altered the foot plantar inclination relative to the ground, thereby shortening the moment arm of medio-lateral GRF that resulted in the reduced ankle inversion angular impulse.