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Background and Purpose. Abnormality in the structure of the medial longitudinal arch of the foot is commonly thought to be a predisposing factor to injury. The purpose of this investigation was to compare the reliability and validity of several measurements used to characterize various aspects of the foot, including the medial longitudinal arch. Subjects. One hundred two feet (both feet of 51 subjects) were measured to establish a reference database. From this group, a subset of 20 feet (both feet of 10 subjects) was used to determine intertester and intratester reliability. Radiographs of a further subset of 10 feet (right feet of 10 subjects) were used to determine validity. Methods. Five foot measurements were taken in 2 stance conditions: 10% of weight bearing and 90% of weight bearing. Results. Intraclass correlation coefficients (ICCs) for intertester and intratester measurements were between .480 and .995. The most reliable method of characterizing arch type in 10% of weight bearing between testers was dividing navicular height by foot length in 10% of weight bearing. However, this measure yielded highly unreliable measurements in 90% of weight bearing. The most valid measurements were navicular height divided by truncated foot length, navicular height divided by foot length in 10% of weight bearing, and navicular height divided by foot length in 90% of weight bearing. Dorsum height at 50% of foot length divided by truncated foot length showed relatively high intertester reliability (ICC=.811 in 10% of weight bearing, ICC=.848 in 90% of weight bearing) and validity (ICC=.844 in 10% of weight bearing, ICC=.851 in 90% of weight bearing). Conclusion and Discussion. These data suggest that, of the measures tested, the most reliable and valid method of clinically assessing arch height across 10% and 90% of weight bearing was dividing the dorsum height at 50% of foot length by truncated foot length.

It is important to understand the day-to-day variability that is attributed to repositioning of markers especially when assessing a treatment effect or response over time. While previous studies have reported reliability of waveform patterns, none have assessed the repeatability of discrete points such as peak angles, velocities and angular excursions which are often used when making statistical and clinical comparisons. The purpose of this study was to compare the within-and between-day variability of discrete kinematic, kinetic, and ground reaction force (GRF) data collected during running. Comparisons for 20 recreational runners were evaluated for within-and between-day reliability of discrete 3D kinematic, kinetic, and GRF variables. The results indicated that within-day compal-isons were more reliable than between-day. Joint angular velocity and angular excursion values were more reliable betweendays as compared to absolute peak angle measures and may be more useful in interpreting changes in treatment over time. Betweenday kinematic and kinetic sagittal plane values were more reliable than secondary plane values. Reliability of GRF data was greater than kinematic and kinetic data for between-day comparisons.

High- and low-arched feet have long been thought to function differently. The purpose of this study was to investigate the relationship between arch structure and lower extremity mechanics in runners with extreme pes planus and pes cavus. It was hypothesized that low-arched individuals would exhibit an increased rearfoot eversion excursion, eversion/tibial internal rotation ratio, and increased angular velocity in rearfoot eversion when compared to high-arched runners. In addition, it was hypothesized that high-arched runners would exhibit greater vertical loading rates. Twenty high-arched and 20 low-arched runners with histories of running-related injuries were included in this study. Low-arched runners were found to have increased rearfoot eversion excursion, eversion to tibial internal rotation ratio, and rearfoot eversion velocity. High-arched runners had increased vertical loading rate when compared to low-arched runners. These results suggest that arch structure is associated with specific lower extremity kinematics and kinetics. Differences in these parameters may subsequently lead to differences in injury patterns in high-arched and low-arched runners.