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Objective: To compare walking stance phase rearfoot and forefoot motion, ankle joint moments and extrinsic foot muscle EMG profiles between normal and pes planus feet., Design: A cross-sectional comparative study., Background: Musculoskeletal conditions are often attributed to pes planus, in which motion is assumed to be excessive and the muscle control inadequate. However, many of the speculated differences in mechanics and control between the normal and the pes planus foot have not been quantified., Methods: Kinematic and kinetic data were obtained from video recordings of skin surface markers and a force plate, and EMG was recorded with surface electrodes. Analysis of variance was carried out to compare the group profiles., Results: In the pes planus group: the forefoot was less adducted (P < .05) at toe-off, and total transverse plane range of motion, at 8 degrees versus 10 degrees, was less (P < .01); the peak plantarflexor ankle moment at push-off was greater (P < .05); the invertor moment was greater at foot flat (P < .05); for the EMG profiles, activity early in stance, relative to the mean stance phase activity was higher (P < .01) in tibialis anterior and lower (P < .05) in the peronei, soleus and medial and lateral gastrocnemius., Conclusions: Despite reaching statistical significance, the group differences were small for the task of laboratory walking at a natural pace. The main implications of the differences were for restraint of motion. The expectations of excessive motion and muscle effort in the pes planus group were therefore not substantiated., Relevance: Symptomatic pes planus subjects did not reveal the expected biomechanical differences from normal subjects. The underlying causes of symptoms were not identifiable.

Objective: To compare the magnitude and patterns of motion of the rearfoot segment relative to the leg, forefoot segment relative to the rearfoot, height change in the medial longitudinal arch and ground reaction forces of normal adult males during the stance phase of walking., Background: Knowledge of normal motion of the rearfoot and forefoot segments and of the arch during stance phase is important in clinical management., Methods: Motion data were obtained from surface markers, and force data from a force plate, from the right limb of participants while walking at a self-selected pace., Results: Stance phase range of motion across sagittal, frontal and transverse planes was 12 degrees, 4 degrees and 10 degrees for the forefoot, compared to 22 degrees, 8 degrees and 10 degrees for the rearfoot. Most motion occurred at the beginning and end of stance phase when support was via only the rearfoot or forefoot, and when forces were maximal. Arch height decreased from heel contact and increased after heel rise to its maximum at toe-off., Conclusions: The extent of forefoot segment motion confirms the significance of midfoot joints to normal foot function. Between foot flat and heel rise, the forefoot pattern of motion is indicative of foot stability. Typical foot motion does not obey descriptions of triplanar motion such as 'pronation' and 'supination'., Relevance: Typical stance phase foot motion has been described according to a forefoot:rearfoot model and rearfoot:leg model of motion, together with profiles of medial longitudinal arch height and ground reaction forces. This information can be applied in the management of foot dysfunction and should stimulate research into midfoot motion and overall control of the foot.

This study examined stance phase foot kinematics, kinetics and electromyographic (EMG) activity of extrinsic muscles of 18 healthy males. Three-dimensional kinematic and kinetic data were obtained via video analysis of surface markers and a force plate. Ankle joint moments are described about orthogonal axes in a segmental coordinate system. Kinematic data comprise rearfoot and forefoot motion, described about axes of a joint coordinate system, and medial longitudinal arch height. Surface EMG was obtained for tibialis anterior, soleus, gastocnemius medialis and lateralis, peroneus longus and peroneus brevis and extensor digitorum longus. It was concluded that the demands on the controlling muscles are greatest prior to foot flat and after heel rise. Tibialis anterior restrained rearfoot plantarflexion from heel contact to 10% stance, and eversion between 10% stance and footflat. Activity in peroneus longus was consistent with its role in causing eversion after heel contact, then as a stabiliser of the forefoot after heel rise. Activity in peroneus brevis suggested a role in restraining lateral rotation of the leg over the foot, late in stance.