Ground reaction forces and plantar pressure distribution during occasional loaded gait

Center of Pressure- and Machine Learning-based Gait Score and Clinical Risk Factors for Predicting Functional Outcome in Acute Ischemic Stroke

OBJECTIVES

To investigate whether machine learning (ML)-based center of pressure (COP) analysis for gait assessment, when used in conjunction with clinical information, offers additive benefits in predicting functional outcomes in patients with acute ischemic stroke.

DESIGN

A prospective, single-center cohort study.

SETTING

A tertiary hospital setting.

PARTICIPANTS

A total of 185 patients with acute ischemic stroke, capable of walking 10 m with or without a gait aid by day 7 postadmission. From these patients, 10,804 pairs of consecutive footfalls were included for analysis.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The dependent variable was a 3-month poor functional outcome, defined as modified Rankin scale score ≥2. For independent variables, 65 clinical variables including demographics, anthropometrics, comorbidities, laboratory data, questionnaires, and drug history were included. Gait function was evaluated using a pressure-sensitive mat. Time-series COP data were parameterized into spatial and temporal variables and analyzed with logistic regression and 2 ML models (light gradient-boosting machine and multilayer perceptron [MLP]). We derived GAIT-AI output scores from the best-performing model analyzed COP data and constructed multivariable logistic regression models using clinical variables and the GAIT scores.

RESULTS

Among the included patients, 70 (37.8%) experienced unfavorable outcomes. The MLP model demonstrated the highest predictive performance with an area under the receiver operating characteristic curve (AUROC) of 0.799. Multivariable logistic regression identified age, initial National Institutes of Health Stroke Scale, and initial Fall Efficacy Scale-International as associated factors with unfavorable outcomes. The combined multivariable logistic regression incorporating COP-derived output scores improved the AUROC to 0.812.

CONCLUSIONS

Gait function, assessed through COP analysis, serves as a significant predictor of functional outcome in patients with acute ischemic stroke. ML-based COP analysis, when combined with clinical data, enhances the prediction of poor functional outcomes.

Altered gait patterns during arch important development period in children with persistent obesity: An experimental longitudinal study

BACKGROUND

Obesity can cause structural changes and functional adjustments in growing children's feet. However, there is a lack of continuous observation of changes in feet in children with persistent obesity during important developmental periods. This makes it challenging to provide precise preventive measures.

OBJECTIVE

This study aimed to investigate the effects of persistent obesity on gait patterns in children at an important stage in the formation of a robust foot arch.

METHODS

The Footscan® plantar pressure system was used for 3 checks over two years. A total of 372 children aged 7-8 years participated in the study, and gait data from 33 children who maintained normal weight and 26 children with persistent obesity were finally selected. Repeated measures ANOVA or Friedman's test were used for longitudinal comparisons. Independent-Sample t-tests or the Mann-Whitney-Wilcoxon tests were used for cross-sectional comparisons.

RESULTS

During the important period of development, children with persistent obesity did not exhibit a significant decrease in the arch index and had significantly higher values than the normal group in the third check. The persistently obese children showed increased load accumulation in the lateral rearfoot, first metatarsophalangeal joints, and the great toe regions. Children with persistent obesity had significantly greater medial-lateral displacements in the initial contact phase and forefoot contact phase than normal children in the first check. These differences diminished between the second and third checks.

SIGNIFICANCE

Persistent obesity during an important period of foot development leads to slow or abnormal development of arch structure and affects foot loading patterns with heel inverted and forefoot everted. Additionally, the development of gait stability is not limited by persistent obesity.

The Soft Prefabricated Orthopedic Insole Decreases Plantar Pressure during Uphill Walking with Heavy Load Carriage

This study aimed to investigate the effect of varying the hardness of prefabricated orthopedic insoles on plantar pressure and muscle fatigue during uphill walking with a heavy backpack. Fifteen healthy male recreational athletes (age: 20.4 ± 1.0 years, height: 176.9 ± 5.7 cm, weight: 76.5 ± 9.0 kg) wore prefabricated orthopedic insoles with foot arch support; a heel cup with medium (MI), hard (HI), and soft (SI) relative hardnesses; and flat insoles (FI). They performed treadmill walking on uphill gradients with 25 kg backpacks. The plantar pressure and surface electromyographic activity were recorded separately, in 30 s and 6 min uphill treadmill walking trials, respectively. The HI, MI, and SI significantly decreased peak plantar pressure in the lateral heel compared to FI. The MI and SI significantly decreased the peak plantar pressure in the fifth metatarsal compared to FI. The MI significantly reduced the pressure–time integral in the lateral heel compared to FI. The HI significantly increased the peak plantar pressure and pressure–time integral in the toes compared to other insoles, and decreased the contact area in the metatarsal compared to SI. In conclusion, a prefabricated orthopedic insole made of soft material at the fore- and rearfoot, with midfoot arch support and a heel cup, may augment the advantages of plantar pressure distribution during uphill weighted walking.

The Podoprint® plantar pressure platform: Evaluation of reliability and repeatability, and determination of the normality parameters

INTRODUCTION

The Podoprint® pressure platform system is widely used in routine podiatric clinical practice to measure plantar pressures. It allows non-invasive examination of the patient, and provides fast results with high levels of precision, reliability, and repeatability. Once these conditions have been demonstrated, the clinical and/or research use of baropodometry allows results to be obtained in the field of podology that are far from inconsiderable. The study was designed to evaluate the repeatability and reliability of the platform, and to identify the normal foot pressure parameters.

METHODS

Records were collected from 52 random healthy individuals, 10 men and 42 women, in two sessions separated by one week. The study variables were: maximum pressure, mean pressure, support surface areas (heel, midfoot, and forefoot), and contact time. Repeatability and reliability were evaluated by calculating the interclass correlation coefficient (ICC) and the coefficient of variation (CV) in the three tests.

RESULTS

The ICCs showed moderate to good repeatability for the variables of interest, and the CVs were all less than 18%. The maximum pressure was under the forefoot (mean 2675.4 ± 513.8 g/cm²). The mean contact time of the steps was 0.72 ± 0.07 s.

CONCLUSIONS

The Podoprint® system is a reliable tool for evaluating the distribution of plantar pressures in the dynamic study of the barefoot gait of healthy individuals.

Characteristics of Plantar Pressure Distribution in Diabetes with or without Diabetic Peripheral Neuropathy and Peripheral Arterial Disease

Background. Excessive plantar pressure leads to increased risk of diabetic foot ulcers. Diabetic peripheral neuropathy (DPN) and peripheral arterial disease (PAD) have been considered to be associated with alterations in gait and plantar pressure in diabetic patients. However, few studies have differentiated the effects with each of them. Objective. To investigate the plantar pressure distribution in diabetic patients, with DPN and PAD as independent or combined factors. Methods. 112 subjects were recruited: 24 diabetic patients with both DPN and PAD (DPN-PAD group), 12 diabetic patients with DPN without PAD (DPN group), 10 diabetic patients with PAD without DPN (PAD group), 23 diabetic patients without DPN or PAD, and 43 nondiabetic healthy controls (HC group). The in-shoe plantar pressure during natural walking was measured. Differences in peak pressure, contact area, proportion of high pressure area (%HP), and anterior/posterior position of centre of pressure (COP) were analysed. Results. Compared with HC group, in DPN-PAD group and DPN group, the peak pressures in all three forefoot regions increased significantly; in PAD group, the peak pressure in lateral forefoot increased significantly. The contact area of midfoot in the DPN-PAD group decreased significantly. PAD group had larger HP% of lateral forefoot, DPN group had larger HP% of inner forefoot, and DPN-PAD group had larger HP% of total plantar area. There was a significant tendency of the anterior displacement of COP in the DPN-PAD group and DPN group. No significant differences were observed between the D group and HC group. Conclusion. DPN or PAD could affect the plantar pressure distribution in diabetic patients independently or synergistically, resulting in increased forefoot pressure and the area at risk of ulcers. DPN has a more pronounced effect on peak pressure than PAD. The synergistic effect of them could significantly reduce the plantar contact area of midfoot.

Grip socks improve slalom course performance and reduce in-shoe foot displacement of the forefoot in male and female sports players

This study assessed whether grip socks reduce in-shoe foot motion and improve change of direction performance in team sports players and compared the effects between males and females. A sledge and pulley system confirmed the static coefficient of friction was increased in the grip socks (1.17) compared to the regular socks (0.60). Performance during a slalom course was faster in the grip socks compared to regular socks (p = .001). Yet, there was no difference in the utilised coefficient of friction between the shoe-floor interface during a side-cut and turn change of direction manoeuvre. Three-dimensional motion capture revealed the grip socks reduced in-shoe foot displacement during the braking phase, with greater effect during the sharper turn manoeuvre. The magnitude of natural foot spreading within the shoe was greater in the calcaneus region than the metatarsals which suggests in-shoe sliding may only occur at the forefoot. Males tended to have increased in-shoe displacement, which is associated with larger foot spreading due to their increased mass. Findings provide guidance for product developers to enhance the support inside the shoe at the forefoot, and change of direction performance.

Pathophysiological Behaviour of the Climber's Foot versus the General Population: A Prospective Observational Study

Sport climbing is becoming increasingly popular, with people of all types and ages practising it. The feet suffer a lot of pressure with the sport climbing gesture, which in the long run can produce alterations in the first metatarsophalangeal joint or in the first radius of the foot. Objective: To observe and quantify the behaviour of the foot in climbing subjects compared to a group of non-climbing subjects, comparing the pressures, first metatarsophalangeal joint and first radius of the foot. Method: This is a non-experimental and observational, cross-sectional, descriptive and prospective research. The study sample consisted of 105 subjects (42 males and 63 females). The control group consisted of 52 subjects and the climbing group consisted of 53 subjects. Different exploratory tests were carried out on all the subjects, such as: mobility of the metatarsophalangeal joint and first radius of the foot and the study of plantar pressures in different areas of the study. Results: No significant difference was found between left and right foot measurements (p > 0.05). The pressures of the same foot are significant, both at static and dynamic stages for both groups. The maximum pressure in the climbing group was under the first metatarsal head, while in the control group it was under the second metatarsal head. There were significant differences in the mobility of the first metatarsal joint and the first radius between the two groups. Conclusion: It can be seen that the group of climbers has less plantar pressure than the control group. They also have altered mobility of the first radius and the first metatarsophalangeal joint.

Force Plate with Simple Mechanical Springs and Separated Noncontact Sensor Elements

This paper reports on a force plate (FP) using mechanical springs and noncontact distance sensors. The ground reaction force (GRF) is one of the factors for clarify biomechanics, and FPs are widely used to measure it. The sensor elements of conventional FPs are mainly strain gauges. Thus, the mechanical properties of FP depend on the sensor element performance. If the FP performance must change, we must redesign the FP, including changing the sensor elements. Here, we proposed an FP that uses a measuring principle based on simple springs and noncontact sensors. The shape and performance of the proposed FP are expected to change easily. As a prototype device, we designed and fabricated an FP installed with 12 springs and four sensors for human walking. A planar coil and magnet were used as the sensor elements, and the sensor output was proportional to the vertical and horizontal displacements. The FP resonance frequency was 123 Hz, which was larger than the required specification. The calibration experiments showed that vertical and horizontal forces and moments could be measured independently. The FP’s resolutions were 1.9 N and 1.4 N in the anterior–posterior and vertical directions, respectively. Furthermore, the fabricated FP measured GRF similarly to the commercial FP when a human walked on the plate. These results suggest that the proposed method will be helpful for FPs with custom-made requirements.

Footwear outsole temperature may be more related to plantar pressure during a prolonged run than foot temperature

Objective. The temperature of the sole of the foot has been suggested as an alternative to the measurement of plantar pressure during running despite the scarce evidence about their relationship. The temperature of the footwear outsole could also be representative of plantar pressure distribution due to its less multifactorial dependence. The aim of the study was to determine if plantar pressure during a prolonged run could be related to plantar temperature, either of the sole of the foot or the footwear outsole.Approach. Thirty recreational runners (15 males and 15 females) performed a 30 min running test on a treadmill. Thermographic images of the sole of the foot and the footwear outsole were taken before and immediately after the test, and dynamic plantar pressure was measured at the end of the test. Pearson correlations and stepwise multiple linear regressions were performed.Main results.Plantar pressure percentage was related to a moderate correlation with plantar temperature percentage in forefoot and rearfoot (P < 0.05), showing a greater relationship with the footwear outsole than with the sole of the foot (r = 0.52-0.73 versusr = 0.40-0.61, respectively). Moreover, moderate correlations were also observed between footwear outsole and sole of the foot temperature variables, especially in rearfoot.Significance. Footwear outsole temperature may be better related to plantar pressure distribution than sole of the foot temperature, in the forefoot and rearfoot. The midfoot is the most sensitive and variable region to analyze, as it does not seem to have any relationship with plantar pressure.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity

Context

Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance.

Purpose

1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics.

Hypothesis

1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV.

Methods

Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05).

Results

FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking.

Conclusion

Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

Insoles of uniform softer material reduced plantar pressure compared to dual-material insoles during regular and loaded gait

There is limited evidence on the efficacy of insole materials to reduce plantar pressure during regular walking and loaded walking. In-shoe plantar pressures and subjective footwear comfort were recorded in twenty healthy participants at a self-selected treadmill walking speed in six conditions: two commercial insoles or no insole, and with or without carrying a load in a backpack. A single-material insole, comprised of polyurethane, had reduced density and compressive stiffness compared to a dual-material insole with added viscoelastic material in rearfoot and forefoot regions. Load carriage increased peak pressure across the foot. Both insoles reduced plantar pressure in the rearfoot. Yet, the softer single-material insole also attenuated forefoot pressure and loaded walking did not appear to cause bottoming-out of the polyurethane. Plantar pressure changes did not affect perceived footwear comfort. The softer single-material insole was more effective in reducing plantar pressure, further research would confirm if this influences injury prevalence.

A Novel Method for Gait Analysis on Center of Pressure Excursion Based on a Pressure-Sensitive Mat

Center of pressure (COP) during gait is a useful measure for assessing gait ability and has been investigated using platform or insole systems. However, these systems have inherent restrictions in repeated measure design or in obtaining true vertical force. This study proposes a novel method based on a pressure-sensitive mat system for COP measurement and presents normal reference values for the system. To explore repeatability, this work also investigated relative and absolute intra-rater reliabilities and determined the number of footfalls required to obtain a reliable measurement. Ninety healthy young adults participated and performed barefoot walking on a force-sensitive mat at a comfortable and fast pace. The time points and subphase duration of the stance phase, displacement ranges, and mean locations of COP and velocity of COP excursion were parameterized. The results showed acceptable and consistent variabilities of the parameters. Seven footfalls were determined as the threshold for most parameters to show a good to reasonable level of reliability. In conclusion, the presented method can be used as a reliable measurement for COP excursion, and it is recommended that more than seven footfalls be collected to ensure a high level of reliability.

The relationship between neck angles and ground reaction forces in schoolchildren during backpack carriage

Study aim: This study aimed to examine the effect of carrying backpacks on neck posture and ground reaction forces (GRFs) and to investigate the relationship between neck angles and GRFs during backpack carriage in schoolchildren.

Material and methods: The craniohorizontal angle (CHA), craniovertebral angle (CVA), sagittal shoulder posture (SSP) and GRFs were measured in right-handed schoolchildren (14 male and 12 female) with mean age 10.17 ± 1.15 years during loaded and unloading conditions. The Qualisys motion analysis system with a force plate was used to assess the neck angles and GRFs.

Results: During backpack carriage there was a significant increase in the CHA (p = 0.001), significant decrease in the CVA and SSP (p = 0.001, 0.016 respectively), no significant difference in the normalized (scaled to body weight) vertical GRFs (p > 0.05), and a significant increase in the anterior braking and posterior propulsive GRFs (p = 0.035, 0.002 respectively) compared to the unloading condition. While carrying a backpack there was a moderate negative correlation between the SSP and first vertical GRF (r = –0.464) and a strong negative correlation with the second vertical GRF (r = –0.571) and the posterior propulsive GRF (r = –0.587).

Conclusion: Carrying a backpack weighing 15% of the child’s body weight changes the head posture and increases the normalized value of the anterior-posterior shear force. During backpack carriage, decreasing the SSP is associated with increasing the load acceptance, thrusting and posterior propulsive forces. Increasing the shearing force may lead to development of postural abnormities. Consequently, the ideal backpack weight should be considered by parents and teachers.

A state-of-the-art review of foot pressure

The science of foot pressure studies the forces acting on the bottom and different regions of the foot along with the pressure exerted on the plantar surface with the interacting surface in contact. The information derived gave impact to human biomechanical assessment on body balance and ergonomics posture during gait. Various experiments designed at generating foot pressure data returns only with limited knowledge generated. Obviously, the procedure for experiment design needs to be properly understood from the foot morphology aspects; healthiness, footwear, surface in contact, load and forces impacts, and the foot sensitivity as well as the specification for the foot pressure. This paper reviews the proper preliminary experimental setups for foot pressure measurement analysis during static or dynamic gait. The strength and limitations of recent devices used and considerable variables are also discussed. The overall review explains that the comfortable natural gait in relation to the aspects of sensitivity, load, time duration, and stability are the standard considerations for plantar pressure experiments.

Effects of Backpacks on Ground Reaction Forces in Children of Different Ages When Walking, Running, and Jumping

Backpacks for transporting school loads are heavily utilized by children, and their mechanical advantages have been allowing children to transport heavy loads. These heavy loads may increase ground reaction forces (GRFs), which can have a negative effect on joints and bone health. The aim of this study was to investigate the effect of backpacks on the GRFs generated by children during walking, running, and jumping. Twenty-one children from the fifth (G-5, n = 9) and ninth (G-9, n = 12) grades walked, ran, and jumped over a force plate. When walking, the G-5 had GRF increments in the first (17.3%; p < 0.001) and second (15.4%; p < 0.001) peak magnitude, and in the total integral of the vertical force (20%; p < 0.001), compared to the control condition (i.e., no backpack), and the G-9 had increments of 10.4%, 9%, and 9% (p < 0.001), respectively. The G-9 did not prolong their total stance time (p > 0.05), unlike the G-5 (p = 0.001). When running, total stance time increased 15% (p < 0.001) and 8.5% (p < 0.001) proportionally to the relative load carried, in the G-5 and G-9, respectively. Peak GRF did not increase in any group when running or landing from a jump over an obstacle. It was found that GRF was affected by the backpack load when walking and running. However, when landing from a jump with the backpack, schoolchildren smoothed the landing by prolonging the reception time and thus avoiding GRF peak magnitudes.

The effects of backpack carriage on gait kinematics and kinetics of schoolchildren

There has been a growing concern among clinical and educational practitioners, as well as, policy makers on the use of backpacks by schoolchildren. On a daily basis, pupils spend a significant amount of time carrying stuffed and heavy backpacks. The aim of this study was to investigate the effects of backpack carriage with different loads on spatiotemporal parameters of gait, plantar pressure and force distribution under different foot regions in schoolchildren. We have assessed fifty-seven primary school students (7–9 years-old) performing four walks of 10 m (carrying 0%, 10%, 15% of body mass in the backpack and the load they brought to school). A floor-based photocell system was used to collect the gait kinematics and insoles capacitive pressure sensors the kinetics. Children walked slower and at lower cadence with the load brought to school than in the other three conditions. There was no significant main effect on stride length. Backpack carriage with different loads did have a significant effect on plantar pressure and force distribution. We noted that heavier the load, higher the pressure and force under different foot regions. Our findings highlight that gait biomechanics of children (such as stride kinematics and pressure under the feet) is affected by carrying loads in the backpacks.

The effect of working memory intervention on the gait patterns of the elderly

INTRODUCTION

The purpose of this study was to evaluate the role of working memory (WM) training on walking patterns in elderly people.

METHODS

20 elderly adults were selected and assigned randomly to two groups: WM training group and control group. WM training group received 6 weeks of computerized training on various spatial and verbal WM tasks. The spatial-temporal parameters, the ground reaction force and the timing activity of muscles in pre-posttest and in a follow-up were taken.

RESULT

The results indicated that a significant change in gait speed, double support time and stride time (p < 0.05). Alternations in ground reaction force (GRF) components were found significant. Timing of muscle activity also showed non-significant change after WM intervention.

CONCLUSION

Based on the results of this study, it can be concluded that WM intervention can be applied to improve gait parameters. The improvements in vertical ground reaction force after training may result in an increase upright stability and a decreased in rate falls.

Influence of Shopping Bags Carrying on Human Responses While Walking

Shopping as a daily activity that involves carrying shopping bags in hands might be associated with risk factors contributing to the development of low back pain (LBP) and strains and sprains in the upper extremity. A three-way repeated measures experiment was conducted for the purpose of the study. The independent variables were holding style, carrying technique, and shopping bags' weights. The dependent variables were cardiac cost, muscles' activities as a percentage of their maximum voluntary contraction's EMG (%MVC), peak plantar pressure (PPP), and discomfort rating. Carrying grocery bags with both hands to the sides of the body using shopping bags' holder was favorable and advantageous to other carrying conditions in terms of less cardiac cost, less %MVC, less peak plantar pressure, and less discomfort. It is useful to carry grocery bags close to the body with both hands using holders that are available in the local market.

Development of an IMU-based foot-ground contact detection (FGCD) algorithm

It is well known that, to locate humans in GPS-denied environments, a lower limb kinematic solution based on Inertial Measurement Unit (IMU), force plate, and pressure insoles is essential. The force plate and pressure insole are used to detect foot-ground contacts. However, the use of multiple sensors is not desirable in most cases. This paper documents the development of an IMU-based FGCD (foot-ground contact detection) algorithm considering the variations of both walking terrain and speed. All IMU outputs showing significant changes on the moments of foot-ground contact phases are fully identified through experiments in five walking terrains. For the experiment on each walking terrain, variations of walking speeds are also examined to confirm the correlations between walking speed and the main parameters in the FGCD algorithm. As experimental results, FGCD algorithm successfully detecting four contact phases is developed, and validation of performance of the FGCD algorithm is also implemented. Practitioner Summary: In this research, it was demonstrated that the four contact phases of Heel strike (or Toe strike), Full contact, Heel off and Toe off can be independently detected regardless of the walking speed and walking terrain based on the detection criteria composed of the ranges and the rates of change of the main parameters measured from the Inertial Measurement Unit sensors.

Stiffness Effects in Rocker-Soled Shoes: Biomechanical Implications

Rocker-soled shoes provide a way to reduce the possible concentration of stress, as well as change movement patterns, during gait. This study attempts to examine how plantar force and spatio-temporal variables are affected by two rocker designs, one with softer and one with denser sole materials, by comparing them with the barefoot condition and with flat-soled shoes. Eleven subjects' gait parameters during walking and jogging were recorded. Our results showed that compared with barefoot walking, plantar forces were higher for flat shoes while lower for both types of rocker shoes, the softer-material rocker being the lowest. The plantar force of flat shoes is greater than the vertical ground reaction force, while that of both rocker shoes is much less, 13.87-30.55% body weight. However, as locomotion speed increased to jogging, for all shoe types, except at the second peak plantar force of the denser sole material rocker shoes, plantar forces were greater than for bare feet. More interestingly, because the transmission of force was faster while jogging, greater plantar force was seen in the rocker-soled shoes with softer material than with denser material; results for higher-speed shock absorption in rocker-soled shoes with softer material were thus not as good. In general, the rolling phenomena along the bottom surface of the rocker shoes, as well as an increase in the duration of simultaneous curve rolling and ankle rotation, could contribute to the reduction of plantar force for both rocker designs. The possible mechanism is the conversion of vertical kinetic energy into rotational kinetic energy. To conclude, since plantar force is related to foot-ground interface and deceleration methods, rocker-design shoes could achieve desired plantar force reduction through certain rolling phenomena, shoe-sole stiffness levels, and locomotion speeds.

Intra-Rater Reliability and Minimal Detectable Change of Vertical Ground Reaction Force Measurement during Gait and Half-Squat Tasks on Healthy Male Adults

BACKGROUND

The understanding of vertical ground reaction force (VGRF) during walking and half-squatting is necessary and commonly utilised during the rehabilitation period. The purpose of this study was to establish measurement reproducibility of VGRF that reports the minimal detectable changes (MDC) during walking and half-squatting activity among healthy male adults.

METHODS

14 male adults of average age, 24.88 (5.24) years old, were enlisted in this study. The VGRF was assessed using the force plates which were embedded into a customised walking platform. Participants were required to carry out three trials of gait and half-squat. Each participant completed the two measurements within a day, approximately four hours apart.

RESULTS

Measurements of VGRF between sessions presented an excellent VGRF data for walking (ICC Left = 0.88, ICC Right = 0.89). High reliability of VGRF was also noted during the half-squat activity (ICC Left = 0.95, ICC Right = 0.90). The standard errors of measurement (SEM) of VGRF during the walking and half-squat activity are less than 8.35 Nm/kg and 4.67 Nm/kg for the gait and half-squat task respectively.

CONCLUSION

The equipment set-up and measurement procedure used to quantify VGRF during walking and half-squatting among healthy males displayed excellent reliability. Researcher should consider using this method to measure the VGRF during functional performance assessment.

Center of pressure and total force analyses for amputees walking with a backpack load over four surfaces

Understanding how load carriage affects walking is important for people with a lower extremity amputation who may use different strategies to accommodate to the additional weight. Nine unilateral traumatic transtibial amputees (K4-level) walked over four surfaces (level-ground, uneven ground, incline, decline) with and without a 24.5 kg backpack. Center of pressure (COP) and total force were analyzed from F-Scan insole pressure sensor data. COP parameters were greater on the intact limb than on the prosthetic limb, which was likely a compensation for the loss of ankle control. Double support time (DST) was greater when walking with a backpack. Although longer DST is often considered a strategy to enhance stability and/or reduce loading forces, changes in DST were only moderately correlated with changes in peak force. High functioning transtibial amputees were able to accommodate to a standard backpack load and to maintain COP progression, even when walking over different surfaces.

The influence of gait cadence on the ground reaction forces and plantar pressures during load carriage of young adults

Biomechanical gait parameters--ground reaction forces (GRFs) and plantar pressures--during load carriage of young adults were compared at a low gait cadence and a high gait cadence. Differences between load carriage and normal walking during both gait cadences were also assessed. A force plate and an in-shoe plantar pressure system were used to assess 60 adults while they were walking either normally (unloaded condition) or wearing a backpack (loaded condition) at low (70 steps per minute) and high gait cadences (120 steps per minute). GRF and plantar pressure peaks were scaled to body weight (or body weight plus backpack weight). With medium to high effect sizes we found greater anterior-posterior and vertical GRFs and greater plantar pressure peaks in the rearfoot, forefoot and hallux when the participants walked carrying a backpack at high gait cadences compared to walking at low gait cadences. Differences between loaded and unloaded conditions in both gait cadences were also observed.

The generation of centripetal force when walking in a circle: insight from the distribution of ground reaction forces recorded by plantar insoles

Background

Turning involves complex reorientation of the body and is accompanied by asymmetric motion of the lower limbs. We investigated the distribution of the forces under the two feet, and its relation to the trajectory features and body medio-lateral displacement during curved walking.

Methods

Twenty-six healthy young participants walked under three different randomized conditions: in a straight line (LIN), in a circular clockwise path and in a circular counter-clockwise path. Both feet were instrumented with Pedar-X insoles. An accelerometer was fixed to the trunk to measure the medio-lateral inclination of the body. We analyzed walking speed, stance duration as a percent of gait cycle (%GC), the vertical component of the ground reaction force (vGRF) of both feet during the entire stance, and trunk inclination.

Results

Gait speed was faster during LIN than curved walking, but not affected by the direction of the curved trajectory. Trunk inclination was negligible during LIN, while the trunk was inclined toward the center of the path during curved trajectories. Stance duration of LIN foot and foot inside the curved trajectory (Foot-In) was longer than for foot outside the trajectory (Foot-Out). vGRF at heel strike was larger in LIN than in curved walking. At mid-stance, vGRF for both Foot-In and Foot-Out was higher than for LIN foot. At toe off, vGRF for both Foot-In and Foot-Out was lower than for LIN foot; in addition, Foot-In had lower vGRF than Foot-Out. During curved walking, a greater loading of the lateral heel occurred for Foot-Out than Foot-In and LIN foot. On the contrary, a smaller lateral loading of the heel was found for Foot-In than LIN foot. At the metatarsal heads, an opposite behaviour was seen, since lateral loading decreased for Foot-Out and increased for Foot-In.

Conclusions

The lower gait speed during curved walking is shaped by the control of trunk inclination and the production of asymmetric loading of heel and metatarsal heads, hence by the different contribution of the feet in producing the body inclination towards the centre of the trajectory.

Plantar Pressure and Foot Temperature Responses to Acute Barefoot and Shod Running

Purpose. Increased contact pressure and skin friction may lead to higher skin temperature. Here, we hypothesized a relationship between plantar pressure and foot temperature. To elicit different conditions of stress to the foot, participants performed running trials of barefoot and shod running. Methods. Eighteen male recreational runners ran shod and barefoot at a self-selected speed for 15 min over different days. Before and immediately after running, plantar pressure during standing (via a pressure mapping system) and skin temperature (using thermography) were recorded. Results. No significant changes were found in plantar pressure after barefoot or shod conditions (p > 0.9). Shod running elicited higher temperatures in the forefoot (by 0.5-2.2°C or 0.1-1.2% compared with the whole foot, p < 0.01) and midfoot (by 0.9-2.4°C, p < 0.01). Barefoot running resulted in higher temperature variation in the rearfoot (0.1-10.4%, p = 0.04). Correlations between skin temperature and plantar pressure were not significant (r < 0.5 and r > -0.5, p > 0.05). Conclusions. The increase in temperature after the shod condition was most likely the result of footwear insulation. However, variation of the temperature in the rearfoot was higher after barefoot running, possible due to a higher contact load. Changes in temperature could not predict changes in plantar pressure and vice-versa.

Short-term effects of backpack carriage on plantar pressure and gait in schoolchildren

PURPOSE

To assess the effects of backpack carriage on plantar pressure distributions and spatio-temporal gait parameters among children.

PARTICIPANTS

Two hundred-eighteen schoolchildren, aged 6-13, and attending primary and secondary schools in the city of Cagliari (Italy).

METHODS

Participants were tested at school, during regular days. A pressure plate and wearable inertial sensors were used to measure plantar pressures and spatio-temporal parameters of gait. Measures were obtained during both quiet standing and walking, and both with and without a backpack. The latter contained those items a child had on the testing day.

RESULTS

Participants carried a mean mass in their backpacks of 5.2 kg, and more than half had a backpack/body mass ratio higher than 15%. While spatio-temporal gait parameters were not affected by backpack carriage, significant increases (up to 25%) in plantar pressures were found during both static standing and walking, especially in the forefoot.

CONCLUSION

Under realistic conditions, the impact of backpack carriage was more evident on foot-ground interaction than on gait features. However, long-term consequences of altered plantar pressure need to be assessed in future work, considering the actual durations typically spent carrying school items.

Metabolic rate of carrying added mass: a function of walking speed, carried mass and mass location

The effort of carrying additional mass at different body locations is important in ergonomics and in designing wearable robotics. We investigate the metabolic rate of carrying a load as a function of its mass, its location on the body and the subject's walking speed. Novel metabolic rate prediction equations for walking while carrying loads at the ankle, knees and back were developed based on experiments where subjects walked on a treadmill at 4, 5 or 6km/h bearing different amounts of added mass (up to 2kg per leg and 22kg for back). Compared to previously reported equations, ours are 7-69% more accurate. Results also show that relative cost for carrying a mass at a distal versus a proximal location changes with speed and mass. Contrary to mass carried on the back, mass attached to the leg cannot be modeled as an increase in body mass.

Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces

The aims of this study were to test the effects of two pressure relief insoles developed for backpackers and obese people on the ground reaction forces (GRF) and plantar pressure peaks during gait; and to compare the GRF and plantar pressures among normal-weight, backpackers, and obese participants. Based on GRF, plantar pressures, and finite element analysis two insoles were manufactured: flat cork-based insole with (i) corkgel in the rearfoot and forefoot (SLS1) and with (ii) poron foam in the great toe and lateral forefoot (SLS2). Gait data were recorded from 21 normal-weight/backpackers and 10 obese participants. The SLS1 did not influence the GRF, but it relieved the pressure peaks for both backpackers and obese participants. In SLS2 the load acceptance GRF peak was lower; however, it did not reduce the plantar pressure peaks. The GRF and plantar pressure gait pattern were different among the normal-weight, backpackers and obese participants.

In-shoe plantar pressures and ground reaction forces during overweight adults' overground walking

PURPOSE

Because walking is highly recommended for prevention and treatment of obesity and some of its biomechanical aspects are not clearly understood for overweight people, we compared the absolute and normalized ground reaction forces (GRF), plantar pressures, and temporal parameters of normal-weight and overweight participants during overground walking.

METHOD

A force plate and an in-shoe pressure system were used to record GRF, plantar pressures (foot divided in 10 regions), and temporal parameters of 17 overweight adults and 17 gender-matched normal-weight adults while walking.

RESULTS

With high effect sizes, the overweight participants showed higher absolute medial-lateral and vertical GRF and pressure peaks in the central rearfoot, lateral midfoot, and lateral and central forefoot. However, analyzing normalized (scaled to body weight) data, the overweight participants showed lower vertical and anterior-posterior GRF and lower pressure peaks in the medial rearfoot and hallux, but the lateral forefoot peaks continued to be greater compared with normal-weight participants. Time of occurrence of medial-lateral GRF and pressure peaks in the midfoot occurred later in overweight individuals.

CONCLUSIONS

The overweight participants adapted their gait pattern to minimize the consequences of the higher vertical and propulsive GRF in their musculoskeletal system. However, they were not able to improve their balance as indicated by medial-lateral GRF. The overweight participants showed higher absolute pressure peaks in 4 out of 10 foot regions. Furthermore, the normalized data suggest that the lateral forefoot in overweight adults was loaded more than the proportion of their extra weight, while the hallux and medial rearfoot were seemingly protected.

Accuracy and repeatability of the gait analysis by the WalkinSense system

WalkinSense is a new device designed to monitor walking. The aim of this study was to measure the accuracy and repeatability of the gait analysis performed by the WalkinSense system. Descriptions of values recorded by WalkinSense depicting typical gait in adults are also presented. A bench experiment using the Trublu calibration device was conducted to statically test the WalkinSense. Following this, a dynamic test was carried out overlapping the WalkinSense and the Pedar insoles in 40 healthy participants during walking. Pressure peak, pressure peak time, pressure-time integral, and mean pressure at eight-foot regions were calculated. In the bench experiments, the repeatability (i) among the WalkinSense sensors (within), (ii) between two WalkinSense devices, and (iii) between the WalkinSense and the Trublu devices was excellent. In the dynamic tests, the repeatability of the WalkinSense (i) between stances in the same trial (within-trial) and (ii) between trials was also excellent (ICC > 0.90). When the eight-foot regions were analyzed separately, the within-trial and between-trials repeatability was good-to-excellent in 88% (ICC > 0.80) of the data and fair in 11%. In short, the data suggest that the WalkinSense has good-to-excellent levels of accuracy and repeatability for plantar pressure variables.