Changes in segment coordination variability and the impacts of the lower limb across running mileages in half marathons:Implications for running injuries

Background:Segment coordination variability(CV)is a movement pattern associated with running-related injuries.It can also be adversely affected by a prolonged run.However,research on this topic is currently limited.The purpose of this study was to investigate the effects of a prolonged run on segment CV and vertical loading rates during a treadmill half marathon.Methods:Fifteen healthy runners ran a half marathon on an instrumental treadmill in a biomechanical laboratory.Synchronized kinematic and kinetic data were collected every 2 km(from 2 km until 20 km),and the data were processed by musculoskeletal modeling.Segment CVs were computed from the angle-angle plots of selected pelvis-thigh,thigh-shank,and shank-rearfoot couplings using a modified vector coding technique.The loading rate of vertical ground reaction force was also calculated.A one-way MANOVA with repeated measures was performed on each of the outcome variables to examine the main effect of running mileage.Results:Significant effects of running mileage were found on segment CVs(p≤0.010)but not on loading rate(p=0.881).Notably,during the early stance phase,the CV of pelvis frontal thigh frontal was significantly increased at 20 km compared with the CV at 8 km(g=0.59,p=0.022).The CV of shank transverse vs.rearfoot frontal decreased from 2 km to 8 km(g=0.30,p=0.020)but then significantly increased at both 18 km(g=0.05,p<0.001)and 20 km(g=0.36,p<0.001).Conclusion:At the early stance,runners maintained stable CVs on the sagittal plane,which could explain the unchanged loading rate throughout the half marathon.However,increased CVs on the frontal/transverse plane may be an early sign of fatigue and indicative of possible injury risk.Further studies are necessary for conclusive statements in this regard.

The interaction effects of rocker angle and apex location in rocker shoe design on foot biomechanics and Achilles tendon loading

The influences of rocker shoes on foot biomechanics were controversial because the interaction between two design factors—rocker angle and apex location,was usually omitted.This study investigated the interaction effects of rocker angle and apex location on plantar foot pressure,metatarsophalangeal/ankle angle,and Achilles tendon force during walking.Ten participants performed walking trials under six rocker shoe conditions:2 rocker angles(mild and severe)×3 apex locations(distal,standard,and proximal),wherein the plantar foot pressure was measured and the movement data were processed by musculoskeletal modeling to report joint angle and Achilles tendon force.A two-way ANOVA repeated measures was used for statistics.Significant interaction effects were reported in examinations of forefoot pressure,midfoot pressure,and metatarsophalangeal dorsiflexion.The standard apex significantly reduced peak forefoot and midfoot pressures(p=0.008–0.034,Hedges'g=0.75–0.84),which was further decreased by a severe rocker angle(p=0.006,Hedges'g=0.51–0.81).Moving the apex proximally reduced Achilles tendon forces(p<0.001,Hedges'g=0.80)and facilitated both metatarsophalangeal dorsiflexion and ankle plantarflexion during push-off(p=0.003–0.006,Hedges'g=0.03–0.82).Rocker angle seemed to have fewer effects on ankle joint angle and Achilles tendon force.We concluded that apex location was likely the dominant design factor of the rocker sole in influencing foot biomechanics,yet its interactions with rocker angle should be considered.The configuration of the two features could be varied to possess different therapeutic merits and adapt to specific application purposes.

Computational models of flatfoot with three-dimensional fascia and bulk soft tissue interaction for orthosis design

The finite element(FE)method has been widely used to investigate the internal force of plantar fascia,which could reveal the relationship between plantar fascia dysfunction and flatfoot deformity during weight-bearing conditions.However,for most foot FE models,plantar fascia utilized truss elements or three-dimensional geometry that did not consider the interaction between plantar fascia and bulk soft tissue.These configurations could ignore the impact of superoinferior loading induced by arch support and underestimate the plantar fascia loading.This study aims to investigate how the fascia-bulk soft tissue interaction affects the internal foot biomechanics in the flatfoot FE analysis with a three-dimensional plantar fascia model,which included both fascia-bone and fascia-bulk soft tissue interactions(3DBPT).To evaluate the effect of fascia-bulk soft tissue interaction on internal foot mechanics,this study compared the 3DBPT model with the other two plantar fascia models,including linear fascia(BPL)and three-dimensional plantar fascia without fascia-bulk soft tissue interaction(3DBP).The predicted foot contact pressure in the 3DBPT model was compared with the measured value obtained by the F-Scan pressure measurement system in balanced standing.Peak von Mises stresses in the plantar fascia and foot ligaments were reported.The stress of the plantar fascia in the 3DBPT model was higher than that of 3DBP.In the 3DBPT model,the superoinferior loading exerted on the bulk soft tissue could be directly transferred to the plantar fascia.The proposed model,including the plantar fascia and bulk soft tissue interaction,could reveal relatively reliable plantar fascia loading in flatfoot deformity,thereby contributing to the development of orthotic designs for the flatfoot deformity.

An instrument for methodological quality assessment of single-subject finite element analysis used in computational orthopaedics

The methodological quality of subject-specific finite element analysis papers depends on the rigor of the study design and detailed description of key elements,while assessment instruments are often confined to clinical trials or quasi-experiments.This study aims to present an instrument for methodological quality assessment of singlesubject finite element analysis used in computational orthopaedics(MQSSFE).Based upon existing instruments and relevant review papers,a pilot version was developed consisting of 37 items with 6 domains,including study design and presentation of findings,subject recruitment,model reconstruction and configuration,boundary and loading conditions(simulation),model verification and validation,and model assumption and validity.We interviewed four experts in the field to assess the face validity and refined the instrument.The instrument was tested for interrater reliability among two assessors on nine finite element study papers.Also,the criterion validity was evaluated by comparing the similarity of the MQSSFE and the modified Down and Black instrument.The intraclass correlation coefficient was 0.965,while the MQSSFE was significantly moderately correlated with the modified Down and Black instruments(r=0.61).We believed that MQSSFE was adequately appropriate,reliable,and valid for assessing the methodological quality for finite element studies used in computational orthopaedics.The instrument could facilitate quality assessment in the systematic reviews of finite element models and checklists for fidelity.