New Optimized Dynamic Calibration Proposition for Discretized Sensorized Insoles With Resistive Force Sensor: A Descriptive and Comparative Study.

Sensorized insoles (SIs) have been used as a wearable instrument to study human gait and have the potential to identify and predict pathologies and injuries. However, most of these sensorized insoles are only statically calibrated, relying on a scale and known weights to establish a relationship between electrical signals and the load applied on laboratory benches while ignoring the dynamic interaction between person and instrument. This study proposes and verifies a calibration method complementary to static calibration to compensate for different dynamic interactions between the insole and the individual during gait. In order to perform this comparison, a laboratory test was proposed with 32 volunteers (18 men and 14 women). Each volunteer walked on a double-belt instrumented treadmill (Bertec at 1000 Hz, Bertec Corp, Columbus, OH) while wearing an experimental resistive sensorized insole (SI). The SI data were compared with the instrumented treadmill and adjusted using an optimization algorithm to create a dynamic coefficient to complement and optimize the results. This study also verifies the impact of the method considering three different types of gait: pronated, neutral, and supinated. After using this technique and considering static calibration, the Pearson correlation coefficient between the SI and the instrumented treadmill improved by 12%.

An exploration of the effects of prefabricated and customized insoles on lower limb kinetics and kinematics during walking, stepping up and down tasks: A time series analysis.

BACKGROUND: Prefabricated and customized insoles are used in clinical practice to reduce foot pronation. Although data exist on the effects at key points within the stance phase, exploring the impact of different insoles using time series analysis may reveal more detail about their efficacy. RESEARCH QUESTION: What are the effects revealed by a time series analysis of arch-supported prefabricated insoles (PREFABRICATED) versus arch-supported prefabricated insoles customized with a 6º medial wedge (CUSTOMIZED) on the lower limb biomechanics during walking, stepping up and down tasks in individuals with pronated feet? METHODS: Nineteen individuals with excessive foot pronation performed walking, stepping up and down tasks using three insoles: CONTROL (flat insole), CUSTOMIZED, and PREFABRICATED. Angles and moments of ankle and knee coronal and hip transverse planes were compared between conditions using statistical parametric mapping (SPM). RESULTS: For walking, CUSTOMIZED reduced ankle eversion moment compared to CONTROL during midstance and PREFABRICATED during propulsion. CUSTOMIZED decreased KAM during midstance and propulsion compared to PREFABRICATED. Compared to CONTROL, CUSTOMIZED and PREFABRICATED reduced hip internal rotation during propulsion and loading response, respectively. CUSTOMIZED decreased eversion movement during midstance and propulsion for the stepping up task. PREFABRICATED reduced eversion movement during midstance in comparison to CONTROL. For the stepping down task, CUSTOMIZED increased eversion movement during propulsion compared to PREFABRICATED. CUSTOMIZED reduced hip internal rotation angle for stepping up task during propulsion, decreased medial rotation movement during midstance compared to CONTROL, and reduced medial rotation during midstance compared to PREFABRICATED. CUSTOMIZED increased KAM for stepping up and down tasks during propulsion. SIGNIFICANCE: These findings suggest that both CUSTOMIZED and PREFABRICATED reduce foot pronation. However, non-local effects, such as changes in KAM and hip internal rotation, were seen only in the CUSTOMIZED. Therefore, CUSTOMIZED may be preferable if the objective is to modify the knee and hip mechanics.

Reliability of a computational model for evaluating thoracoabdominal mobility in newborns: a cross-sectional study.

The present study aimed to verify the inter and intra-examiner reliability of an interactive custom-made MATLAB® App for bio-photogrammetric analysis of thoracoabdominal mobility in newborns and compare the respiratory rate (RR) results between the automatic MATLAB® App and its manual counterpart. This is a cross-sectional study conducted in 27 healthy newborns of both sexes (gestational age between 37 and 41 weeks and up to 72 h of life) who did not cry during data acquisition. Chest and abdominal areas of the subjects in the supine position were analyzed through 60 s videos, totaling 30,714 photograms. All photograms were analyzed by three examiners on three different occasions. Analysis of variance (ANOVA) and intraclass correlation coefficient (ICC) were applied, adopting a 95% confidence interval and significance level of α = 0.05. Reliability was excellent for intra (ICC 0.81-0.96) and inter-examiner correlations (ICC 0.84-0.99) between the chest and abdominal areas, in both inspiration and expiration, with no differences between them. Evaluation of newborns' thoracoabdominal mobility using the custom-made MATLAB® App for bio-photogrammetric analysis exhibited good to excellent intra- and inter-examiner reliability and an excellent correlation between manual and automatic models for measuring RR. Thus, it proved to be an objective and practical tool for bedside thoracoabdominal mobility assessment in different clinical situations involving neonatal care.

Is there a dose-response of medial wedge insoles on lower limb biomechanics in people with pronated feet during walking and running?

BACKGROUND: Although the effects of medial wedge insoles on lower limb biomechanics have been investigated, information about the effects of different magnitudes of medial posting is still lacking. RESEARCH QUESTION: What are the dose-response effects of medial wedge insoles with postings varying between 0 °, 3 °, 6 °, and 9 ° of inclination on the lower limb biomechanics during walking and running in individuals with pronated feet? METHODS: Sixteen participants with an FPI ≥ 6 were recruited. Four arch-supported insole conditions with varying degrees of medial heel wedge were tested (0°, 3°, 6°, and 9°). A 3D motion analysis system with force plates was used to obtain the kinetics and kinematics of walking and running at self-selected speeds. To compare the ankle, knee, and hip angles and moments among conditions, a time series analysis was performed using Statistical Parametric Mapping (SPM). RESULTS: A reduction in ankle eversion angle was observed during walking for all insoles. For running, the 6° and 9° insoles decreased the ankle eversion angle during early stance and increased this angle during the propulsive phase. A decrease in ankle eversion moment was observed in walking and running for 6° and 9° insoles. An increase in knee adduction moment occurred in walking and running for all insoles. For hip, the 6° and 9° insoles showed, during walking, a decrease in hip adduction angle and an increase in hip adduction and external rotation moments. For most variables, statistical differences were found for a greater period across the stance phase as the medial wedge increased, except for ankle eversion moment and hip external rotation moment during walking. SIGNIFICANCE: The biomechanical effects over the time series for many of the parameters increased with the addition of insole inclination, showing a dose-response effect of medial wedge insoles on the lower limb biomechanics during walking and running in adults with excessive foot pronation.

The Effects of Knee Flexion on Tennis Serve Performance of Intermediate Level Tennis Players.

This study aimed to investigate the effects of knee flexion during the preparation phase of a serve on the tennis serve performance, using inertial sensors. Thirty-two junior tennis players were divided into two groups based on their maximum knee flexion during the preparation phase of serve: Smaller (SKF) and Greater (GKF) Knee Flexion. Their racket velocity, racket height, and knee extension velocity were compared during the tennis serve. Inertial sensors tracked participants' shank, thigh, and racket motions while performing five first, flat, and valid serves. Knee flexion was analysed during the preparation phase of serve, knee extension velocity after this phase, racket velocity just before ball impact, and racket height at impact. Pre-impact racket velocity (mean difference [MD] = 3.33 km/h, p = 0.004) and the knee extension velocity (MD = 130.30 °/s, p = 0.012) were higher in the GKF than SKF; however, racket impact height was not different between groups (p = 0.236). This study's findings support the importance of larger knee flexion during the preparation phase of serve-to-serve performance. This motion should be seen as a contributor to racket velocity.

Hip passive stiffness is associated with midfoot passive stiffness.

BACKGROUND: Hip motion in the transverse plane is coupled with foot motion in the frontal plane during closed kinematic activities, such as gait. Considering that movement patterns and bone alignment might influence passive mechanical properties of joints in the long term, it is possible that hip passive stiffness and foot complex stiffness and alignment are related to each other. OBJECTIVES: To investigate whether hip passive stiffness, midfoot passive stiffness and shank-forefoot alignment are related to each other. METHOD: Thirty healthy adult individuals with a mean age of 25.4 years participated (18 women and 12 men). The Foot Torsimeter was used to measure midfoot stiffness, and hip stiffness and foot alignment were measured using clinical measures. Pearson and Spearman correlation coefficients were calculated to test the associations between each pair of variables, with α = 0.05. RESULTS: Hip stiffness was positively correlated with midfoot absolute stiffness (r = 0.41, p = 0.02), indicating that increased hip stiffness is associated with increased midfoot stiffness. There were no associations between shank-forefoot alignment and the other variables. CONCLUSIONS: In clinical settings, individuals with reduced hip passive stiffness may also have reduced midfoot passive stiffness, and vice versa. Shank-forefoot alignment is not linearly associated with hip or midfoot passive stiffness.

Respiratory synchrony comparison between preterm and full-term neonates using inertial sensors.

INTRODUCTION: Due to inefficient respiratory control, newborns become prone to asynchronous thoracoabdominal (TA) movements. The present study quantitatively estimated the synchrony of TA in preterm and full-term newborns through an inertial and magnetic measurement units (IMMUs) system. METHODS: This cross-sectional study was conducted with 20 newborns divided into Preterm Group (PTG, n = 10) and Full-Term Group (FTG, n = 10). Each neonate had IMMUs placed on the sternum and near the umbilicus, thus the TA motion was estimated through the resultant inclination angles calculated using a sensor fusion filter. The respiratory incursions were also manually counted and video-recorded for two minutes, then used to validate a Matlab custom-written routine for their automatic identification. The respiratory cycles were used to calculate the phase change angle (φ) between the thoracic and abdominal compartments. Association between the manual and automatic methods were verified by Pearson's correlation and root mean squared errors (RMSE), and the comparison between the groups was performed through the Student's t test with α = .05. RESULTS: The values of respiratory incursions measured by both methods showed a high association and low measurement error (r = .96, RMSE = 9.8, p < .001). The FTG presented a higher occurrence of TA synchrony (p = .049) while the PTG group presented a higher occurrence of TA asynchrony (p = .036). No difference was found between the groups regarding the paradoxical classification (p = .071). CONCLUSION: The proposed method was valid to quantitatively assess the TA synchrony of hospitalized neonates. Preterm infants had a higher occurrence of the asynchronous respiratory pattern in comparison to full-term infants.

Midfoot passive stiffness affects foot and ankle kinematics and kinetics during the propulsive phase of walking.

The midfoot joint complex (MFJC) is related to the mechanics and efficiency of the walking propulsive phase and low midfoot passive stiffness may require compensatory foot and ankle joint moments to avoid excessive pronation and inefficient propulsion. This study aimed to investigate the kinematics and kinetics of the MFJC and ankle during the propulsive phase of walking in subjects with larger and smaller midfoot passive stiffness. MFJC passive stiffness of 20 healthy adult participants, and the kinematics and kinetics of the MFJC (forefoot-rearfoot) and ankle (rearfoot-shank) during the stance phase of walking were measured. The participants were divided equally into two groups according to the MFJC passive stiffness. Ranges of motion (ROM) and mean joint moments were computed for the late stance. Independent t-tests (α = 0.05) revealed that subjects with lower midfoot passive stiffness showed an increased MFJC sagittal ROM (flattened longitudinal arch) (p = 0.002), increased ankle frontal ROM (more everted positions) (p = 0.002), increased MFJC frontal ROM (more inverted positions) (p = 0.019), as well as a tendency for larger ankle sagittal ROM (p = 0.056). They also showed increased MFJC (p = 0.021) and ankle (p = 0.018) moments in the sagittal plane, increased MFJC moment in the frontal plane (p = 0.047) and a tendency for a predominant ankle moment in the frontal (p = 0.058). Foot and ankle joint moments are possible strategies to reduce pronation and improve propulsion, but not sufficient to prevent the altered kinematics related to low midfoot stiffness. Therefore, midfoot passive stiffness is critical for foot and ankle kinematics and kinetics during walking propulsive phase and is a potential target of interventions.

Reliability and sensitivity of an instrument for measuring the midfoot passive mechanical properties.

To assess the test - retest reliability and sensitivity of an instrument developed to measure the passive mechanical properties of the midfoot joint complex (MFJC), nine female and three male healthy young adults were evaluated in two different days by two experienced examiners. After proper participant positioning on the instrument, the left forefoot was passively moved from eversion (20°) to inversion (45°) at 2°/s, while the rearfoot and shank were kept immobile. From the instrument's sensing units (torque meter and potentiometer at 100 Hz), passive torque and angle data were registered. Passive stiffness was calculated as the instantaneous slope of the torque vs. angle curve. Therefore, the variables analyzed were resting angle, passive torques and stiffnesses during inversion and eversion through the intraclass correlation coefficient (ICC3,3), standard error of measurement (SEM) and minimal detectable change (MDC95). For the resting angle, ICC3,3 ranged from 0.85 to 0.91, SEM ranged from 1.54° to 1.95° and MDC95 ranged from 4.26° to 5.41°. For the torques, ICC3,3 ranged from 0.85 to 0.97, SEM ranged from 0.09Nm to 0.42Nm and MDC95 ranged from 0.26Nm to 1.16Nm. Finally, for the stiffnesses, ICC3,3 ranged from 0.79 to 0.98, SEM ranged from 0.01Nm/° to 0.04Nm/° and MDC95 ranged from 0.01Nm/° to 0.10 Nm/°. It can be concluded that most of the measurements presented good to excellent reliability with low measurement error. Hence, clinicians and researchers may benefit from the reliable and stable measures provided by the Foot Torsimeter when assessing patients and planning interventions.

Comparison of the rigidity and forefoot - Rearfoot kinematics from three forefoot tracking marker clusters during walking and weight-bearing foot pronation-supination.

Due to the relative motion among the foot rays, the present study aimed to compare the rigidity as well as the forefoot - rearfoot kinematics obtained from three forefoot tracking marker clusters during walking and foot pronation-supination (PROSUP). Nineteen healthy adults performed six walking trials and ten cycles of foot PROSUP movements recorded by an optoelectronic system. Rearfoot's and forefoot's coordinate system were equal for all setups, only the forefoot's tracking markers locations varied among them, which were: (1st) a typical cluster, focusing on the proximal forefoot, (2nd) a second typical cluster, focusing on the distal forefoot and outer metatarsals, and (3rd) a new cluster proposition, focusing on the distal forefoot and central metatarsals. Cluster rigidity was the normalized intra-markers residual, and forefoot - rearfoot angles were the forefoot motion relative to the rearfoot at the peak of each plane of motion. Repeated-measures ANOVA with pairwise comparisons (α=0.05) revealed that the 3rd cluster had the smallest residual (p < 0.001) in comparison with the other clusters for both walking and PROSUP. Differences between forefoot - rearfoot angles were found in the sagittal plane for walking (p < 0.001), but not for PROSUP (p > 0.686). In the frontal and transverse planes, all clusters showed different forefoot - rearfoot angles (p < 0.001) for both walking and PROSUP. The 1st cluster showed smaller ROM in the three planes during walking, and the 3rd cluster was the only that showed forefoot - rearfoot inversion during maximum pronation. Therefore, the new forefoot tracking marker cluster proposition (3rd cluster) captured different forefoot - rearfoot kinematics and can be recommended when the objective is to maximize the cluster rigidity.

The clinical measure of forefoot-shank alignment partially reflects mechanical properties of the midfoot joint complex.

BACKGROUND: The clinical measure of forefoot-shank alignment (FSA) predicts the amount of foot pronation during weight-bearing tasks. This may be mediated by a relationship between FSA and the mechanical resistance of the midfoot joint complex (MFJC) to forefoot inversion, which is a component of weight-bearing foot pronation. OBJECTIVE: To investigate if the clinical measure of FSA is associated with MFJC mechanical resistance to inversion. DESIGN: Cross-sectional observational study. METHOD: Forty-six healthy individuals (27 males; 19 females) with mean age of 26.4 years (SD 5.3) participated in this study. FSA was measured with photographs. The resistance torque of the MFJC against inversion was measured with a specially designed device. Mean torque, mean torque normalized by body mass, and joint resting position were calculated as variables related to MFJC mechanical resistance. Correlation analyses were carried out to test the association between each MFJC resistance variable and the FSA (α = 0.05). RESULTS: /findings: There were significant moderate correlations of FSA with mean torque (r = -0.44, p = 0.002), mean normalized torque (r = -0.42, p = 0.004) and resting position (r = 0.39, p = 0.007). The clinical measure of FSA is associated to the mechanical resistance of the MFJC: (a) the greater the FSA, the smaller the resistance torques; (b) the greater the FSA, the more inverted the forefoot resting position. CONCLUSIONS: These results showed that the clinical measure of FSA is moderately related to mechanical properties of the MFJC.

Myofascial force transmission in the lower limb: An in vivo experiment.

Anatomical studies have shown structural continuity between the lumbopelvic region and the lower limb. The present study aimed to verify how simultaneous changes on knee/hip positions modify the ankle's resting position and passive torque. Thirty-seven subjects underwent an isokinetic assessment of ankle passive torque. The relationship between the absolute values of ankle passive resistance torque and the ankle angular position was used to calculate the dependent variables: ankle resting position (position in which the passive resistance torque is zero); and ankle passive torque at 0° (torque at the neutral position of the ankle in the sagittal plane). These measures were carried out under three test conditions: 0° at knee and 0° at hip (0°/0°); 90° at knee and 90° at hip (90°/90°); and, 135° at knee and 120° at hip (135°/120°). The results demonstrated that the ankle resting position shifted towards dorsiflexion when knee/hip position changed from 0°/0° to 90°/90° and shifted towards plantar flexion when knee/hip position changed from 90°/90° to 135°/120°, achieving values close to the ones at the position 0°/0°. Similarly, passive torque reduced when knee/hip position changed from 0°/0° to 90°/90°, but it increased when knee/hip position changed from 90°/90° to 135°/120°. The unexpected changes observed in ankle passive torque and resting position due to changes in knee and hip from 90°/90° to 135°/120°, cannot be explained exclusively by forces related to tissues crossing the knee and ankle. This result supports the existence of myofascial force transmission among lower limb joints.

Assessment of three-dimensional joint kinematics of the upper limb during simulated swimming using wearable inertial-magnetic measurement units.

The analysis of the joint kinematics during swimming plays a fundamental role both in sports conditioning and in clinical contexts. Contrary to the traditional video analysis, wearable inertial-magnetic measurements units (IMMUs) allow to analyse both the underwater and aerial phases of the swimming stroke over the whole length of the swimming pool. Furthermore, the rapid calibration and short data processing required by IMMUs provide coaches and athletes with an immediate feedback on swimming kinematics during training. This study aimed to develop a protocol to assess the three-dimensional kinematics of the upper limbs during swimming using IMMUs. Kinematics were evaluated during simulated dry-land swimming trials performed in the laboratory by eight swimmers. A stereo-photogrammetric system was used as the gold standard. The results showed high coefficient of multiple correlation (CMC) values, with median (first-third quartile) of 0.97 (0.93-0.95) and 0.99 (0.97-0.99) for simulated front-crawl and breaststroke, respectively. Furthermore, the joint angles were estimated with an accuracy increasing from distal to proximal joints, with wrist indices showing median CMC values always higher than 0.90. The present findings represent an important step towards the practical use of technology based on IMMUs for the kinematic analysis of swimming in applied contexts.

Wearable inertial sensors in swimming motion analysis: a systematic review.

The use of contemporary technology is widely recognised as a key tool for enhancing competitive performance in swimming. Video analysis is traditionally used by coaches to acquire reliable biomechanical data about swimming performance; however, this approach requires a huge computational effort, thus introducing a delay in providing quantitative information. Inertial and magnetic sensors, including accelerometers, gyroscopes and magnetometers, have been recently introduced to assess the biomechanics of swimming performance. Research in this field has attracted a great deal of interest in the last decade due to the gradual improvement of the performance of sensors and the decreasing cost of miniaturised wearable devices. With the aim of describing the state of the art of current developments in this area, a systematic review of the existing methods was performed using the following databases: PubMed, ISI Web of Knowledge, IEEE Xplore, Google Scholar, Scopus and Science Direct. Twenty-seven articles published in indexed journals and conference proceedings, focusing on the biomechanical analysis of swimming by means of inertial sensors were reviewed. The articles were categorised according to sensor's specification, anatomical sites where the sensors were attached, experimental design and applications for the analysis of swimming performance. Results indicate that inertial sensors are reliable tools for swimming biomechanical analyses.