What is the foot strike pattern distribution in children and adolescents during running? A cross-sectional study.

BACKGROUND: There is a lack of studies describing foot strike patterns in children and adolescents. This raises the question on what the natural foot strike pattern with less extrinsic influence should be and whether or not it is valid to make assumptions on adults based on the knowledge from children. OBJECTIVES: To investigate the distribution of foot strike patterns in children and adolescents during running, and the association of participants' characteristics with the foot strike patterns. METHODS: This is a cross-sectional study. Videos were acquired with a high-speed camera and running speed was measured with a stopwatch. Bayesian analyses were performed to allow foot strike pattern inferences from the sample to the population distribution and a supervised machine learning procedure was implemented to develop an algorithm based on logistic mixed models aimed at classifying the participants in rearfoot, midfoot, or forefoot strike patterns. RESULTS: We have included 415 children and adolescents. The distribution of foot strike patterns was predominantly rearfoot for shod and barefoot assessments. Running condition (barefoot versus shod), speed, and footwear (with versus without heel elevation) seemed to influence the foot strike pattern. Those running shod were more likely to present rearfoot pattern compared to barefoot. The classification accuracy of the final algorithm ranged from 80% to 88%. CONCLUSIONS: The rearfoot pattern was predominant in our sample. Future well-designed prospective studies are needed to understand the influence of foot strike patterns on the incidence and prevalence of running-related injuries in children and adolescents during running, and in adult runners.

Physical and psychological predictors on pain intensity in conscripts with plantar fasciitis.

BACKGROUND: Plantar fasciitis is commonly found among the physically active population, including conscripts. Some studies have reported that being overweight and having psychological symptoms contribute to pain from plantar fasciitis. However, there is a lack of information regarding the physical predictors, and more research is needed to determine the relationship between such predictors and pain intensity from plantar fasciitis in conscripts. OBJECTIVE: To determine which physical and psychological variables act as predictors of pain intensity among Thai novice conscripts with plantar fasciitis. METHODS: Two hundred and seventy Thai novice conscripts without musculoskeletal pain completed the Depression, Anxiety and Stress Scale short version and then received baseline assessment of ankle dorsiflexion angle, ankle plantarflexor strength, and quality of lower extremity movement from a physical therapist. After 10 weeks of military training, 71 of these Thai conscripts developed pain from plantar fasciitis. Multiple linear regression analysis with the forward stepwise method was used to explore the predictors of pain intensity due to plantar fasciitis. RESULTS: Using a forward regression analysis, anxiety (B=0.13; 95% CI, 0.06-0.20; p<0.01) and quality of movement score (B=0.87; 95% CI, 0.28-1.47; p=0.01) were significant predictors of pain intensity. The regression model with these predictors explained 25% of the variability in pain intensity from plantar fasciitis. CONCLUSION: Higher scores of anxiety and movement quality on the lateral step-down task were associated with pain intensity from plantar fasciitis after the completion of a 10-week military program. However, lower ankle dorsiflexion angle and ankle plantarflexor strength did not predict pain intensity.

Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks.

The aim of this study is to use a multilayer perceptron (MLP) artificial neural network (ANN) for phaseless imaging the human heel (modeled as a bilayer dielectric media: bone and surrounding tissue) and the calcaneus cross-section size and location using a two-dimensional (2D) microwave tomographic array. Computer simulations were performed over 2D dielectric maps inspired by computed tomography (CT) images of human heels for training and testing the MLP. A morphometric analysis was performed to account for the scatterer shape influence on the results. A robustness analysis was also conducted in order to study the MLP performance in noisy conditions. The standard deviations of the relative percentage errors on estimating the dielectric properties of the calcaneus bone were relatively high. Regarding the calcaneus surrounding tissue, the dielectric parameters estimations are better, with relative percentage error standard deviations up to ≈ 15%. The location and size of the calcaneus are always properly estimated with absolute error standard deviations up to ≈ 3 mm. Microwave tomography of the calcaneus using phaseless data. Simulations were inspired in Computed Tomography images from real heels (above). Inverse problem was solved using Multilayer Perceptron Artificial Neural Network (below).

Gait initiation and partial body weight unloading for functional improvement in post-stroke individuals.

BACKGROUND: To better understand gait initiation in individuals with stroke and suggest possible training strategies, we compared the gait initiation of individuals with stroke and age-matched controls, and we examined the influence of different amounts of body weight support (BWS) during the execution of gait initiation in individuals with stroke. MATERIALS AND METHODS: Twelve individuals with stroke and 12 age-matched controls initiated gait after a verbal command at a self-selected and comfortable speed, and individuals with stroke also initiated gait wearing a harness with 0%, 15%, and 30% of BWS. Length and velocity of the first step, distance between heels, and weight bearing in both lower limbs in the initial position were calculated. We also assessed the displacement and average velocity of the center of pressure (CoP) in the medial-lateral (ML) and anterior-posterior (AP) directions in 3 distinct sections during gait initiation, which correspond to the CoP position toward the swing limb, stance limb and progression line, respectively. RESULTS: Individuals with stroke presented shorter and slower step, shorter and slower CoP-ML and CoP-AP toward swing limb and Cop-ML towards stance limb, and longer and faster CoP-AP toward stance limb compared to their peers. The BWS lead individuals with stroke to decrease step length and to increase CoP-ML displacement and average velocity toward stance limb. CONCLUSION: Individuals with stroke present impairments in executing gait initiation mainly during the preparation period and the employment of an overground BWS system promotes a better performance. These results suggest that BWS is a functional strategy that enables individuals with stroke to modulate gait initiation and it could be adopted for gait intervention.

Reference values for the bilateral heel-rise test.

BACKGROUND: The bilateral heel-rise test is an instrument that evaluates the performance of the triceps surae. Normative parameters need to be established for the use of the heel-rise test in clinical practice. OBJECTIVE: To determine the reference values for the bilateral heel-rise test. METHODS: This cross-sectional study assessed healthy subjects using the bilateral heel-rise test. We analyzed the number of repetitions, time (in seconds), and repetition rate (repetitions/second) during execution of the heel-rise test, until the point of voluntary fatigue. The estimates were stratified by age and gender. Multiple linear regression was performed to define the reference equation for the bilateral heel-rise test. RESULTS: A total of 147 individuals were included. The median age was 37 years (IQR 28-46). It was observed that the number of repetitions decreases with age, with a higher number of repetitions in male participants compared to female participants. Gender, body mass index, and maximum activity scores predict 14% of the number of plantar flexions performed in the bilateral heel-rise test. Age and adjusted activity scores predict 18% of the repetition rate in the bilateral heel-rise test. CONCLUSION: The bilateral heel-rise test reference values for an adult population were defined as scores above the 25th percentile for number of repetitions, time, and repetition rate. The number of heel-rise test repetitions that corresponds to the 25th percentile, according to age and gender, is as follows: age 20-29, 65 repetitions for men and 45.5 for women; age 30-39, 62.75 men and 41.5 women; age 40-49, 67.25 men and 45 women; and age 50-59, 54 men and 39.25 women.

A simple, reliable method to determine the mean gait speed using heel markers on a treadmill.

Gait speed is an essential parameter of gait analysis. Our study proposed a simple and accurate method to extract a mean gait speed during walking on a treadmill using only kinematic data from markers placed on the heels of the participants' feet. This method provided an attractive, simple method that remains resistant to errors in treadmill calibration. In addition, this method required only two markers, since heel markers are essential to gait analysis, and the proposed method is robust enough to differentiate among various gait speeds (mean error <1%).

Shoe heel abrasion and its possible biomechanical cause: a transversal study with infantry recruits.

BACKGROUND: Excessive shoe heel abrasion is of concern to patients and shoe manufacturers, but little scientific information is available about this feature and its possible causes. The purpose of this study was to relate this phenomenon with biomechanical factors that could predispose to shoe heel abrasion. METHODS: Ninety-seven recruits (median age 25) were enrolled in this study. Shoe abrasion was assessed manually with a metric plastic tape on the posterior part of the heel that comes in contact with the ground. The number of sprains, foot alignment, and calf muscle shortening (Silfverskiold test) was also assessed in order to relate it with shoe heel abrasion. After using our exclusion criteria, 86 recruits and 172 were considered for this study. RESULTS: The most common abrasion site was the lateral portion of the heel surface (50 %). Forty-four percent of the participants had neutral hind-foot alignment and 39 % had valgus alignment. Twenty-six (30 %) patients have had previous ankle or foot sprains. Neutral foot was related with less calf muscle shortening. On the other hand, valgus hind-foot alignment was more associated with Achilles shortening (p < 0.05). Patients with neutral alignment were associated with more uniform shoe heel abrasion and varus feet were associated with more central and lateral abrasion (p < 0.05). The pattern of shoe heel abrasion was not statistically related with calf muscle shortening nor with number of sprains. CONCLUSION: This study was able to correlate shoe heel abrasion with biomechanical causes (neutral alignment-uniform abrasion/varus alignment-central and lateral abrasion). More effort has to be done to continue evaluating outsole abrasion with its possible biomechanical cause in order to predict and treat possible associated injuries.

Failure to Reposition After Sliding Down in Bed Increases Pressure at the Sacrum and Heels.

UNLABELLED: The head of the bed (HOB) for a patient is often elevated since it improves comfort and facilitates respiratory functions. However, elevating the HOB essentially causes the patient support surface to turn into a ramp, forcing the patient's body to slide down. As the patient slides down, weight pressing on the pelvis, the coccyx, and the ischial tuberosities increases, resulting in associated increases in interface pressures. METHODS: In an institutional review board-approved study, pressure distribution was measured on volunteers at 4 discrete body positions sliding down in bed on 3 commonly used support surfaces. RESULTS: This study showed the total contact area of the patients decreased as they slid down, resulting in increased pressure, particularly on the sacral area and the heels. The study also confirmed that these pressure increases are persistent and occurred on all of the support surfaces tested. CONCLUSION: These increases in pressure likely contribute to the development of pressure ulcers.

Kinematic evaluation of the classical ballet step "plié".

Lack of alignment between the lowerlimb structures, such as the hips, knees, and longitudinal arches of the feet, has been described as an important predisposing factor in musculoskeletal injury among classical ballet dancers. However, no studies were found that analyzed basic ballet movements with quantification of objective criteria of the movements. The purposes of this study were: 1. to establish a methodology to quantify, using kinematic evaluation, the technical criteria that guide the correct execution of all phases of the plié (simultaneous flexion of the hips, knees, and ankle joints); and 2. to explore whether experienced ballet dancers respect those criteria when performing the plié. The technical criteria considered were the following: 1. midfoot stability; 2. pelvic positioning in a neutral alignment; 3. pelvic stability, represented by pelvic angle variation; and 4. vertical alignment of the knee joint with the second toe of the ipsilateral foot. Twenty dancers from Porto Alegre, Brazil, with 18 years of uninterrupted ballet training, were filmed while performing plié using four synchronized cameras. The descriptive statistical analysis involved calculating the median, minimum, and maximum of each of the technical criteria. Results showed that for criterion 1, the 20 dancers showed great stabilization of the midfoot; for criteria 2 and 3, 18 dancers displayed pelvic instability tending toward retroversion throughout execution of the plié; and for criterion 4, 13 dancers presented with medial misalignment of the knees at all phases of the plié. Using these criteria, it was possible to characterize the plié from a kinematic point of view.

The amount of rearfoot motion used during the stance phase of walking.

The purpose of this study was to determine the proportion of available passive frontal plane rearfoot motion that is used during the stance phase of walking. Data were collected from 40 healthy, asymptomatic volunteer subjects (20 men and 20 women) aged 23 to 44 years. Passive inversion and eversion motion was measured in a non-weightbearing position by manually moving the calcaneus. Dynamic rearfoot motion was referenced to a vertical calcaneus and tibia and was measured using a three-dimensional electromagnetic motion-analysis system. The results indicated that individuals used 68.1% of their available passive eversion range of motion and 13.2% of their available passive inversion range of motion during walking. The clinical implication of individuals' regularly operating at or near the end point of their available rearfoot eversion range of motion is discussed.

Biomechanical research in fotwear development

Material test procedures are used to anlyse properties of running shoes. Measurements of me-chanical variables of running shoes have shown that the mechanical cushioning capacity in the heel area improved continously. Various Ground Reaction Forces (GRF) variables are used to describe the load onto the body inrunning. Since the vertical GRF variables are used to describe cushioning properties, the horizontal GRF Fx (posterior-anterior) characterize the touch down and take off component, Fy (medio-lateral) the abduction and adduction of the foot in running. The tibial peak acceleration is highly correlated to GRF variables like the force rising rate and the median power frequency. Furthermore, the recent tendency to design running in shoes with better stability properties seems to result in increased impact loads. Reduced cushioning proper-ties were confirmed by considerably higher tibial peak acceleration values. Rearfoot motion variables have been shown to be lower when using the inshoe goniometer compared to a heel counter method. Recent studies have concentrated onto the aspect of subjective running shoe tests in order to get more knowledge about the comfort perception of subjects depending on the running shoe properties.