The dynamic characteristics of the center of pressure for toe-out gait:implications for footwear design

Background:Toe-out gait is often used as a conservative technique to reduce knee adduction moment,which has been targeted to modify knee osteoarthritis progression.The center of pressure(COP)can not only be used to evaluate gait stability,but is also more reliable and practical than local plantar pressures as it does not depend on accurate foot zone divisions.However,to the authors'knowledge,few study has reported the influence of the foot progression angle on the dynamic characteristics of the COP.Research question:The aim of the study was to investigate the effects of the deliberately toe-out gait on the COP trajectory and stability during walking in healthy individuals.Methods:Thirty healthy young adults were asked to walk along an 8-m walkway.A Footscan 1 m pressure plate was used to measure the center of pressure during walking.Results:Compared to the normal gait,the COP of the toe-out gait shifted laterally during the initial contact phase,and shifted laterally and anteriorly during the forefoot contact phase.The mean anterior-posterior velocity of COP reduced by 0.109 m/s during the foot flat phase and the duration of the foot flat phase and forefoot push off phase increased by 4.5%and reduced by 7.0%,respectively.Significance:Compared to the normal gait,the findings of this study suggest that biomechanical alteration of foot under our experimental conditions may decrease gait stability and increase forefoot load during toe-out walking.The situation may be improved by well-designed footwear or custom-made insole and the biomechanics analysis method can be used to test the efficacy of therapeutic footwear or insole for individuals with deliberately toe-out walking.

The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes

Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.

The center of pressure progression characterizes the dynamic function of higharched feet during walking

Background:The medial longitudinal arch height has an effect on kinetic parameters during gait and might be related to the risk of injury.For the assessment of foot structures,the center of pressure(COP)trajectory is a more reliable and practical parameter than plantar pressure.This study aimed to clarify the COP trajectory and velocity characteristics in the medial-lateral and anterior-posterior direction of individuals with a high-arched foot during barefoot walking.Methods:Sixty-two healthy young adults were asked to walk over a Footscan pressure plate to record the COP parameters during the stance phase of walking.Results:Compared to normal arched feet,the COP during forefoot contact and foot flat phases of high-arched feet shifted anteriorly(19.9mm and 15.1 mm,respectively),and the mean velocity of COP in anterior-posterior direction decreased by 0.26 m/s and increased by 0.044 m/s during these two phases respectively.Conclusions:The findings of this study suggest that the displacement and velocity of COP in anterior-posterior direction was different between high-arched and normal-arched subjects during barefoot walking,which can be used for the assessment of gait characteristics for high-arched individuals.The results of this study may provide insights into modifying clinical intervention for individuals with high-arched feet to enhance rehabilitation and prevent injuries and have implications for assessing the design of footwear and foot orthotics.

Does weight loss affect the center of pressure of children with obesity: a follow-up study

Background:Children with obesity were found to show the greater postural instability compared to the normal-weighted children.However,it’s still unclear if their altered postural control ability would recover towards normal pat-tern after weight loss.The purpose of this study was to investigate the effect of weight loss on the center of pressure(COP)for obese children.Method:Totally 147 children were conducted a follow-up study in three years.A total number of 22 participants aged 7-13 years were recruited for their remission of obesity problem after 36 months.Their dynamic plantar pressure data were collected by Footscan pressure plate.The normalized time of four sub-phases,displacements and velocities of COP in anterior-posterior(AP)and medial-lateral(ML)directions were calculated to perform the Kolmogorov-Smirnov test and paired sample t test for statistical analyses.Results:After weight loss,children’s normalized time of forefoot contact phase(FFCP)increased significantly,and their duration of flat foot phase(FFP)decreased significantly.They also exhibited the more medial and posterior ori-entated COP path after weight loss.In ML-direction,the COP displacement during FFP and FFPOP increased,and the COP velocity during FFPOP increased.In AP-direction,COP velocity during FFP and FFPOP increased.Conclusions:The findings indicated that weight loss would have effects on the COP characteristics and postural stability for obese children.COP trajectory can provide essential information for evaluating foot function.The findings may be useful for obese children,medical staff,and healthcare physician.

The dynamic characteristics of the center of pressure for toe-out gait: implications for footwear design

Background: Toe-out gait is often used as a conservative technique to reduce knee adduction moment, which has been targeted to modify knee osteoarthritis progression. The center of pressure (COP) can not only be used to evalu-ate gait stability, but is also more reliable and practical than local plantar pressures as it does not depend on accurate foot zone divisions. However, to the authors’ knowledge, few study has reported the influence of the foot progression angle on the dynamic characteristics of the COP. Research question: The aim of the study was to investigate the effects of the deliberately toe-out gait on the COP trajectory and stability during walking in healthy individuals. Methods: Thirty healthy young adults were asked to walk along an 8-m walkway. A Footscan 1 m pressure plate was used to measure the center of pressure during walking. Results: Compared to the normal gait, the COP of the toe-out gait shifted laterally during the initial contact phase, and shifted laterally and anteriorly during the forefoot contact phase. The mean anterior-posterior velocity of COP reduced by 0.109 m/s during the foot flat phase and the duration of the foot flat phase and forefoot push off phase increased by 4.5% and reduced by 7.0%, respectively. Significance: Compared to the normal gait, the findings of this study suggest that biomechanical alteration of foot under our experimental conditions may decrease gait stability and increase forefoot load during toe-out walking. The situation may be improved by well-designed footwear or custom-made insole and the biomechanics analysis method can be used to test the efficacy of therapeutic footwear or insole for individuals with deliberately toe-out walking.

The effect of active sitting on trunk motion

Background： Prolonged sitting is a risk factor for low-back pain. The primary purpose of this study is to determine if prolonged active sitting will result in increased trunk motion. Methods： Fifteen healthy female participants volunteered to sit for 30 vain on each of three surfaces including an air-cushion, a stability ball, and a hard surface. Trunk motion was monitored using a Vicon motion capture system, and foot center of pressure was collected with two AMTI force plates. Results： Our findings indicated that the average speed of the trunk center of mass significantly increased with seating surface compliance. There were significant differences in fight and left foot centers of pressure in the antero-posterior direction between the ball and air-cushion conditions and the ball and chair conditions. Conclusion： Active sitting results in increased trunk motion and could have a positive effect on low-back health.

The characteristics of walking strategy in elderly patients with type 2 diabetes

Objective:To explore the walking strategy by monitoring the characteristics of center of pressure(COP)of gait in the elderly with type2 diabetes.Methods:All of the elderly patients with type2 diabetes(n=543)were enrolled from Huadong Hospital Affiliated to Fudan University.Dynamic barefoot plantar pressure was assessed by Footscan7 USB2 flat.Outcome measures included excursion,the x-and ycoordinates displacement of COP and falling frequency.Results:There were 64.5%of cases with abnormal COP trajectory.Among them,45.2%were with abnormal fold-back,14.0%with two or more abnormal fold-back,20.5%with abnormal beginning point deviating from the heel to the arch and metatarsal region,18.0%with abnormal terminal point deviating from the hallux to toe 2e5 and the x-and y-coordinates displacement of COP in both feet are asymmetry.Conclusions:It highlights to put forward the walking strategy according to the abnormal COP trajectory.Due to the elderly diabetics with high risks of falling,the rehabilitation nursing should be strengthened mainly including the training of enhancing proprioception to prevent the elderly patients with type2 diabetes from falling.

Toward more reliable stability measurements in stance: recommendations for number of measurements, foot position and feedback——a cross-sectional study among servicemen

Background:In the military,insufficient postural stability is a risk factor for developing lower extremity injuries.Postural stability training programs are effective in preventing these injuries.However,an objective method for the measurement of postural stability in servicemen is lacking.The primary objective of this study was to assess the influence of the number of repetitions,different foot positions and real-time visual feedback on postural stability,as well as their effects on the intrasession reliability of postural stability measurements in servicemen.The secondary objective was to assess the concurrent validity of the measurements.Methods:Twenty healthy servicemen between 20 and 50 years of age and in active duty were eligible for this quantitative,cross-sectional study.The measurements took place on a force plate,measuring the mean velocity of the center of pressure.The participants were asked to stand as still as possible in three different foot positions(wide stance,small stance,and on one leg),five times each for 45 s each time,and the measurements were performed with and without real-time visual feedback.Results:We observed a significant main effect of foot position(P<0.001),but not of visual feedback(P=0.119)or repetition number(P=0.915).Postural stability decreased in the more challenging foot positions.The ICC estimates varied from 0.809(one repetition in wide stance)to 0.985(five repetitions on one leg).The common variance(R2)between different foot positions without feedback varied between 0.008(wide stance)and 0.412.Conclusions:To yield reliable data,wide-stance measurements should be conducted three times,and small-stance measurements and measurements on one leg should be conducted two times.The scores of a measurement in a particular foot position cannot predict the scores of measurements in other foot positions.

Automatic Assessment of Expanded Disability Status Scale (EDSS) in Multiple Sclerosis Using a Decision Tree

The expanded disability status scale (EDSS) is frequently used to classify the patients with multiple sclerosis (MS). We presented in this paper a novel method to automatically assess the EDSS score from posturologic data (center of pres-sure signals) using a decision tree. Two groups of participants (one for learning and the other for test) with EDSS rang-ing from 0 to 4.5 performed our balance experiment with eyes closed. Two linear measures (the length and the surface) and twelve non-linear measures (the recurrence rate, the Shannon entropy, the averaged diagonal line length and the trapping time for the position, the instantaneous velocity and the instantaneous acceleration of the center of pressure respectively) were calculated for all the participants. Several decision trees were constructed with learning data and tested with test data. By comparing clinical and estimated EDSS scores in the test group, we selected one decision tree with five measures which revealed a 75% of agreement. The results have signified that our tree model is able to auto-matically assess the EDSS scores and that it is possible to distinguish the EDSS scores by using linear and non-linear postural sway measures.

Differences in standing balance between patients with diplegic and hemiplegic cerebral palsy

Maintaining standing postural balance is important for walking and handling abilities in patients with cerebral palsy. This study included 23 patients with cerebral palsy （seven with spastic diplegia and 16 with spastic hemiplegia）, aged from 7 to 16 years of age. Standing posture balance measurements were performed using an AMTI model OR6-7 force platform with the eyes open and closed. Patients with diplegic cerebral palsy exhibited greater center of pressure displacement areas with the eyes open and greater center of pressure sway in the medial-lateral direction with the eyes open and closed compared with hemiplegic patients, Thus, diplegic patients exhibited weaker postural balance control ability and less standing stability compared with hemiplegic cerebral palsy patients.

Balance Performance in Female Collegiate Athletes

Proper balance is essential for athletes during competition and training as sport places different balance requirements on the human body. The purpose of the study was to analyze balance performance among female athletes using COP （center of pressure） sway parameters. Twenty one NCAA （National Collegiate Athletic Association） division I female athletes （soccer, volleyball and dance） completed the study. Static balance was assessed using UST （unilateral stance test） and dynamic balance was assessed using MCT （motor control test） on the NeuroCom Equitest. Sway velocities, root mean square sway and reaction time latencies were used to quantify balance. A one-way between subjects ANOVA （analysis of variance） was performed to analyze these balance parameters. Significant （p 〈 0.05） differences between groups were found and post hoc comparisons revealed that the volleyball and dance groups had better static balance compared to soccer players, while both soccer and volleyball groups had better dynamic balance compared to the dance group. The results from the study indicate two points： first, differences in balance performance among female athletes in different sporting discipline; second, there is no relationship between static and dynamic balance. This indicates that it may be more beneficial to assess and train for static and dynamic balance individually.

Review of biomechanical deviations among nonpregnant,pregnant,and postpartum cohorts

During pregnancy,women experience substantial changes in physiology,morphology,and hormonal systems.These changes have profound effects on the biomechanics of the human body,particularly the musculoskeletal system,resulting in discomfort,pain,and decreased body stability.Sufficient biomechanical knowledge is critical for understanding the etiology and precautions of musculoskeletal disorders.With awareness of health problems in the pregnant cohort,identification,intervention,and precaution of problems have garnered attention.Researchers have conducted studies to determine the biomechanics of pregnancy.There have been review studies on summarization.However,to the best of our knowledge,few studies have comprehensively described biomechanical changes throughout pre-,in-,and postpartum periods.This review analyzed available studies on biomechanical changes during these three periods in the electronic databases of PubMed,Scopus,and Cochrane from inception until June 2,2021.Synthesized the general information,age of the studied subjects,investigated periods,sample size,objectives,measurement tools,and outcomes of reviewed studies.And Using National Institutes of Health quality assessment tool for observational cohort and cross-sectional studies to assessment the quality of the reviewed articles.These studies revealed biomechanical deviations in body stability,motion patterns,and gait modes during these three periods.Regarding research content,there are insufficient studies on certain critical biomechanical aspects,such as the kinetic parameters of the inner body,which are the most direct factors related to musculoskeletal problems.According to the National Institutes of Health quality assessment tool for observational cohort and cross-sectional studies,a more comprehensive and explicit understanding of pregnancy biomechanics can be expected.

Effects of a 12-week online Tai Chi intervention on gait and postural stability in individuals with Parkinson’s disease

Parkinson's disease(PD)affects gait and postural stability.Tai Chi(TC)is recommended for PD for management of the condition,however biomechanical understanding to its effects on gait and postural stability is limited.This study aimed to examine the effects of an online 12-week biomechanical-based TC intervention on gait and posture in people with PD.Fifteen individuals in early-stage PD were recruited(Hoehn&Yahr stages 1-2).The TC intervention program was 60min session,three times weekly for 12 weeks.The pre-and post-intervention test in obstacle crossing,timed-up-and-go(TUG)test,and single leg standing(SLS)with eyes open(EO)and closed(EC)were conducted.Gait speed,crossing stride length,clearance height of the heel and toe,anterior-posterior(AP)and medial-lateral(ML)displacement and velocity of the center of mass(COM)and separation of the COM-center of pressure(COP)were analyzed.The participants significantly improved their pre-vs.post-TC intervention performance on TUG test(p=0.002).During obstacle crossing,the participants significantly increased crossing stride length of the trailing foot,increased AP COM displacement and decreased ML COM-COP separation(p<0.05);the maximal dorsiflexion angle of the leading limb significantly increased and maximal plantarflexion angle of the trailing limb significantly decreased(p<0.05).A 12-week biomechanical-based online TC training was effective towards improvement of gait and postural stability among people in the early-stage of PD.The TC program and online training could be applied for management of PD.

GETTING TO THE BOTTOM OF FOOTWEAR CUSTOMIZATION

Footwear have been evaluated mostly using commercially available products, while some researchers have used custom shoes. Hence, the understanding of the effects of various parameters of a shoe is quite limited. The footbed simulator invented in recent years allows a range of parameters to be studied in quiet standing. It can be used to evaluate perceived feel and center of pressure changes to changes in heel height, seat length, material, wedge angle and toe spring. This paper is meant to show the value of the footbed simulator in terms of research and the actual production of shoes. A study performed with two heel heights, three combinations of seat length and material and three wedge angles showed that the perceived feel is closely related to the center of pressure. The results also show the optimum footbed has a significantly different perceived feel. Thus, the footbed simulator is an ideal way to generate custom footwear designs.

A Kinetic Analysis of Golf Swings Performed by Healthy Older Adult Males

Purpose The kinetic profile of golf swings is frequently assessed in biomechanics.However,most research is limited to young golfers,so the mechanical demands on older athletes are poorly documented.This study provides kinetic data of older golfers swinging with a driver and a 6-iron.Methods We examined 17 older,skilled male golfers(62.2±8.8 years,handicap 8.7±4.9)using a 10-camera motion cap-ture system and two force platforms.Three-dimensional net support moments,joint moments of the hip,knee,and ankle,ground reaction forces(GRF),and the inclination angles between the centre of mass(COM)and centre of pressure(COP)were calculated and tested for between-club differences.Results The 3D net support moments of the trail leg were higher when using the driver,while those of the lead leg were higher with the 6-iron.Between-club differences existed in the relative contribution from each joint,the COM-COP inclina-tion angles,and the peak GRF.Conclusion The mechanical demands of golf swings on older adults differ between a driver and a 6-iron,which likely affects the balance and control strategies required.This improved understanding of the kinetic profiles of golf swings in older adults provide clinicians and coaches better means to maintain older golfers active and healthy for longer.