Introduktion: Fotisättningstyper (FST) vid löpning är associerat med prestation och löprelaterade skador. Tidigare studier har undersökt prevalensen av olika FST hos amerikanska och asiatiska löpare, men däremot inte hos svenska löpare. Syfte: Att undersöka och jämföra prevalensen av olika FST (RFS = hälisättning; MFS = mittfotisättning; FFS = framfotaisättning) hos svenska löpare mellan olika löptävlingar, distanser och med avseende på prestation. Metod: Fotisättningar spelades in i 100 bilder per sekund (fps), vid tre olika platser för både Stockholm maraton (1.2, 25, 42 km) och Göteborgs halv-maraton (7.5, 15, 20 km), baserat på 2071 personer per mätpunkt. FST bedömdes genom en frame-by-frame analys. Resultat: 12’426 observationer av fotisättningar analyserades. Den totala prevalensen av FST var 92.3% (n=11’465), 4.5% (n=559), och 3.2% (n=402), för RFS, MFS, respektive FFS, och skiljde sig mellan maraton och halv-maraton (p < .001, φc = 0.069), där det förekom högre andel RFS i det sistnämnda. FST var associerat med distans, där MFS och FFS var mer vanligt förekommande på kortare distanser jämfört med RFS (p < .001, df = 2; H = 71.524). Stratifierade analyser baserade på löptävling visade att associationen mellan FST och distans inom respektive lopp försvann för halv-maratontävlingen, men kvarstod för maratontävlingen. Slutligen så var FST associerat med prestation (p < .001, df = 2, H = 65.419) och denna kvarstod för både halv-maraton (p < .001) och maratontävlingen (p < .001) efter stratifierade analyser baserat på löptävling. Konklusion: Resultaten överenstämmer med tidigare studier på området av andra grupper löpare, och stödjer tidigare fynd att RFS är den vanligaste förekommande FST, och att FST är associerat med distans och prestation, vid hel- och halvmaraton. / Foot strike type (FST) is associated with performance and running-related injuries. Previous studies have examined the prevalence proportion of FST among predominantly American and Asian cohorts. However, no study has investigated this among a predominantly Swedish cohort. Aim: To examine and compare the prevalence proportions of FST between running races, distance and performance, among a predominantly Swedish cohort of runners. Method: FST was recorded in 100 frames per second (fps), at three different points of measure for both the Stockholm Marathon (1.2, 25, 42 km) and the Gothenburg Half-Marathon (7.5, 15, 20 km), based on 2071 individuals per point of measure. FST was assessed using frame-by-frame analysis. Results: 12’426 observations of FST were analyzed. The overall prevalence proportions of FST was 92.3% (n=11’465), 4.5% (n=559), and 3.2% (n=402), for RFS, MFS, and FFS respectively, and differed between the half-marathon and marathon (p < .001, φc = 0.069), with the latter having higher proportion of RFS. FST was associated with distance, with MFS and FFS being more common at shorter distances compared with RFS (p < .001, df = 2; H = 71.524). Stratifying the data by race type revealed that the association between FST and distance within the races disappeared within the half-marathon race, but remained for the marathon. Lastly, FST was associated with performance (p < .001), and this association remained for both the half-marathon (p < .001) and marathon (p < .001) after stratifying by race type. Conclusion: The results are consistent with previous studies on other populations, and add to the body of literature showing that RFS is the most common FST, and that FST is associated with distance and performance, for full- and half-marathon races.

No / Motion at the midfoot joints can contribute significantly to overall foot motion during gait. However, there is little information regarding the kinematic coupling relationship at the midfoot. The purpose of the present study was to determine whether the coupling relationship at the midfoot and subtalar joints was affected when step width was manipulated during running. Twelve subjects ran over-ground at self-selected speeds using three different step widths (normal, wide, cross-over). Coupling at the midfoot (forefoot relative to rearfoot) and subtalar (rearfoot relative to shank) joints was assessed using cross-correlation techniques. Rearfoot kinematics were significantly different from normal running in cross-over running (P < 0.05) but not in wide running. However, coupling between rearfoot eversion/inversion and shank rotation was consistently high (r > 0.917), regardless of step width. This was also the case for coupling between rearfoot frontal plane motion and forefoot sagittal plane (r < 0.852) and forefoot transverse plane (r > 0.946) motion. There was little evidence of coupling between rearfoot frontal plane motion and forefoot frontal plane motion in any of the conditions. Forefoot frontal plane motion appeared to have little effect on rearfoot frontal plane motion and thus, had no effect on motion at the subtalar joint. The strong coupling of forefoot sagittal and transverse plane motions with rearfoot frontal plane motion suggests that forefoot motion exerts an important influence on subtalar joint kinematics.

In clinical settings, dynamic foot function is commonly inferred from static and passive foot measurements; however, there is little evidence that static foot structure can predict dynamic foot function during walking gait. Previous research seeking to find correlations between the two have focused primarily on sagittal plane midfoot angles even though the midfoot has triplanar motion, which misses potentially important information. Additionally, the focus on kinematics alone may miss the contributions that forces play in midfoot mechanics. To address the angle limitations, a novel Signed Helical Angle (SHA) was developed to capture the triplanar motion of the midfoot from a multi-segment foot model. This was combined with foot segmental force measurements and inverse dynamics to capture dynamic midfoot stiffness. The SHA method and static-dynamic analysis were evaluated on 40 healthy subjects walking at a controlled speed. Subjects were divided into three structural groups based on static arch height (high, normal, low) and stiffness (stiff, normal, flexible). One-way ANOVA was used to evaluate differences among groups in dynamic motion and stiffness and a multiple regression was employed to evaluate relationships across the sample. Calculating the SHA resulted in a greater range of motion (ROM) compared to the sagittal Euler angle commonly used, showing that the motion in the other planes are captured in the SHA. The Finite Helical Axis (FHAx) associated with the SHA also showed that on average the population had a clear distinction between pronation and supination during the stance phase, although individual subjects exhibited substantial variability. While there were visual distinctions in the SHA and the midfoot stiffness among the three stiffness groups and the three arch height groups, the differences were not statistically significant. The only measurement achieving statistical significance was the mean of the sagittal plane midfoot Euler angles among the three AHI groups (p = 0.015); however, this is a postural measure which simply confirms that a high arch will remain high and a low arch will remain low throughout the gait cycle. The lack of any relationships between static foot structure and dynamic foot function, despite advanced modeling and measurements, further confirms that other factors play a large role in foot mechanics. Future studies should focus on evaluating the role of the intrinsic foot musculature (e.g., muscle strength, activation, and redundancy) during gait, and replacing traditional shoe and orthotic recommendations.

One possible solution to common running related injuries is to transition runners from a rearfoot strike during initial contact to a midfoot strike. Natural rearfoot strike runners were studied to see if a modified elliptical trainer could be used to alter their running pattern to that of a midfoot strike runner. Their results were compared to subjects who ran on a non-modified elliptical trainer. After training on the modified elliptical trainer, subjects demonstrated a decrease in foot angle at initial contact when attempting to run with a midfoot strike. Training did not affect all kinetic metrics or stride frequency. However, the kinematic change suggests that there may be an impact on running energetics. Training on the modified elliptical trainer resulted in improved midfoot strike kinematics in natural rearstrike runners when they attempted run in a midfoot strike pattern.