Evaluation of a Method to Estimate Foot Eversion Moments During the Support Phase of Running.

BACKGROUND: Excessive external eversion moments acting on the ankle derived from the ground reaction force (GRF) during the support phase of running are considered a risk factor for overuse lower-limb injuries. The external eversion moment is considered to be dominated by the moment derived from the vertical GRF. However, no studies have directly evaluated the accuracy with which external eversion moment can be estimated with this information. Thus, the objective of this study was to evaluate the extent to which external eversion moment can be estimated from external eversion moment derived from vertical GRF. METHODS: From three-dimensional foot coordinates and GRF data of 28 healthy participants, we computed external eversion moment (EMrun), center of the ankle coordinates (ANKrun), center of pressure coordinates (COPrun), and vertical GRF (VGRFrun) during the support phase of running. Moreover, we computed center of the ankle joint coordinates (ANKstand) and vertical GRF (VGRFstand) in the resting standing position. RESULTS: A highly significant correlation was observed between EMrun and external eversion moment derived from vertical GRF ([COPrun - ANKrun] × VGRFrun), with a contribution of 84.7%. Moreover, a highly significant correlation was observed between EMrun and (COPrun - ANKstand) × VGRFstand, with a contribution of 81.5%. CONCLUSIONS: These results indicate that external eversion moment can be estimated from the external eversion moment derived from vertical GRF with high accuracy. Moreover, it was found that the accuracy did not decrease even if the data of center of ankle and vertical GRF were replaced with the data during standing.

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.

Prediction of the Longitudinal Arch Angle During Running for Various Foot Strike Patterns Using a Static Longitudinal Arch Angle Measurement.

BACKGROUND: The medial longitudinal arch angle (LAA) of the foot has been used as an index of high and low arches. The LAA during the support phase of running (LAArun), which may be related to lower-limb injuries, is commonly predicted from the LAA at standing (LAAstand). However, it is not known whether this prediction is valid for all of the foot contact patterns. The purpose of this study was to verify whether prediction of the LAArun from the LAAstand is valid for different foot strike patterns. METHODS: The 26 participants were divided into a rearfoot strike group (n = 15) and a nonrearfoot strike group (n = 11). The LAA was obtained by measuring the angle formed between the line from the navicular bone to the medial malleolus and the line from the navicular bone to the first metatarsal head. The LAAstand and the minimum value of the LAArun, when the arch is most collapsed, were measured using a motion capture system. RESULTS: There were no significant differences in the LAAstand, the LAArun, and the difference (LAAstand - LAArun) between the two groups. In both groups, a very strong and significant correlation was found between the LAAstand and the LAArun. Furthermore, a nearly identical equation for predicting the LAArun from the LAAstand was derived for the two groups. CONCLUSIONS: The LAArun can be predicted from the LAAstand for any foot strike pattern with almost the same equation.

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.

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

Rearfoot external eversion moments due to ground reaction forces (GRF) during running have been suggested to contribute to overuse running injuries. This study aimed to identify primary factors inducing these rearfoot external eversion moments. Fourteen healthy men ran barefoot across a force plate embedded in the middle of 30-m runway with 3.30 ± 0.17 m · s-1. Total rearfoot external eversion/inversion moments (Mtot) were broken down into the component Mxy due to medio-lateral GRF (Fxy) and the component Mz due to vertical GRF (Fz). Ankle joint centre height and medio-lateral distance from the centre of pressure to the ankle joint centre (a_cop) were calculated as the moment arm of these moments. Mxy dominated Mtot just after heel contact, with the magnitude strongly dependent on Fxy, which was most likely caused by the medio-lateral foot velocity before heel contact. Mz then became the main generator of Mtot throughout the first half of the stance phase, during which a_cop was the critical factor influencing the magnitude. Medio-lateral foot velocity before heel contact and medio-lateral distance from the centre of pressure to the ankle joint centre throughout the first half of the stance phase were identified as primary factors inducing the rearfoot external eversion moment.

The effect of fatigue on the underwater arm stroke motion in the 100-m front crawl.

The purpose of this study was to indicate the effect of fatigue on the underwater right arm stroke motion during the 100-m front crawl. The arm stroke motions of eight male competitive swimmers were captured three-dimensionally at 60 Hz in the positions of 15 m and 65 m from the start. The hand velocity, the arm angular velocities and the relative contribution of the arm angular velocities to the hand velocity were computed at each instant during the arm stroke motion. A significant decrease of the hand velocity and the peak angular velocity of shoulder adduction were observed in the second half than in the first half. The contribution of shoulder adduction was especially large in the pull phase and subsequently that of shoulder horizontal abduction became dominant in the push phase. However, in the second half, the contribution of shoulder adduction tended to decrease while that of shoulder internal rotation tended to increase. Thus, it is quite likely that the arm stroke motion of swimmers were driven to be influenced by induced fatigue and resulted in an increase in the contribution of shoulder internal rotation to compensate the decreased contribution of shoulder adduction angular velocity.